Designer:
Craig J. Coley

Project Category:
Bookshelf Speakers

Project Level:
Beginner

Project Time:
1-8 Hours

Project Cost:
$100 – $500

Project Description:
This project is the Coley A6 speaker. It combines a Dayton reference woofer and large area Dayton AMT with a somewhat unorthodox crossover to provide full range performance in a very modest enclosure. The idea was to make a small full range speaker with presence and detail of an electrostatic with enough bass that a subwoofer was not necessary for most music types. These speakers are paired with the Coley W225 tube amplifier and are my primary speakers.

Design Goals:
The origins of the Coley A6 began with design and construction of an electrostatic speaker for jazz music, my primary listening genre. The detail and articulation of an electrostatic is ideal but it came at the price of complexity, high operating voltage, environmental instability and very low impedance at high frequency. Air Motion Transformers (AMT) offer the same advantages of low moving mass and good articulation without the complexities of electrostatic. While many AMT drivers are relatively small and have crossover points above most of the midrange, the Dayton AMTPRO-4 has a comparatively large emitting area and convenient crossover frequency. The amplifier loading of the A6 speaker is somewhat variable but it only drops below 8 ohms below 100Hz; at high frequencies where amplifier stability can be a problem, the impedance is above 8 ohms and largely resistive.

Driver Selection:
Dayton RS180-4
Dayton AMTPRO-4

Enclosure Design:
Space for the speakers was limited so they were designed to be no taller than necessary to accommodate the drivers and 6” deep shelf-type port. Solid cedar 1”x8” lumber was used for an overall cabinet size of 18”x7.5”x9”. Solid cedar was chosen instead of MDF because of the possibility of formaldehyde emissions causing problems with asthmatic children. Since these were developmental prototypes, there was also the desire to assemble the cabinet with screws to make internal changes easy. No degradation was noticed in the performance due to the use of screws but all holes had to be predrilled. More accomplished carpenters with access to routers or CNC equipment could make a superior cabinet from MDF; the materials and design were chosen due to unique needs and limited carpentry skills.

Enclosure Assembly:
Once the lumber was cut, the box was hand-fitted and holes drilled to accommodate #6×1.5” wood screws. Predrilling is absolutely mandatory when using solid lumber because splitting along the grain is problematic. Once the enclosure sides are completely assembled, the entire enclosure was sanded with an orbital sander until all surfaces and joints were smooth. After sanding, hole-saws were used to create holes for the woofer and terminal block and a jig saw was used to create the rectangular hole for the AMTPRO-4 and port hole. The port shelf occupies the full width of the enclosure and stops 1” from the rear cover. The front panel port hole was intentionally varied between each speaker prototype to determine dimensional criticality. A 1”x4” port size was used on one speaker and 1”x5” on the other with no audible difference. A port hole smaller than 1”x4” was not tested and may cause chuffing.
At this point, the cabinet was finished with two coats of natural tung oil. Once the tung oil had dried, the crossover components were mounted to the rear cover, the speakers wired and then finally mounted to the enclosure. #6×3/4 black sheet metal screws were used for speaker mounting to predrilled holes. Before installing the final side cover, the entire cabinet is loosely filled with 1 pound of Polyfill, fluffed as necessary to fill the cabinet volume. Polyfill serves to reduce the velocity of sound in the enclosure by around 20%, making the cabinet volume appear acoustically larger than its physical size.

Crossover Design:
Since I personally like the sound and smooth transition of first order series crossovers, SPICE was used to model a series crossover design that takes into account the driver circuit characteristics. Fine tuning was still by ear but SPICE modeling was a great help getting very close to the final values. The 100uF capacitor connected across the Dayton RS180-4 is made by connecting two 47uF poly caps in parallel. All components were mounted to the rear panel which allowed easy removal during development.
Since the enclosure was relatively small, an additional L+R circuit was added to increase the available drive to the woofer below 100 Hz. The inductance of this circuit determines the transition frequency while the resistance value affects the depth. This L+R bass-boost circuit is fairly common with open-baffle designs and can be modified to tailor the enclosure used. Some driver efficiency is lost to boost the bass but even with a 25W amplifier, the performance is excellent.

Tips & Tricks:
To even someone with minimal carpentry experience, the Coley A6 should be easy to build with normal woodworking tools. If solid cedar is chosen and care is taken not to split the wood during assembly, the aesthetics are reasonable. The L-Pad and other fixed resistors specified in the design were chosen for use with a 25W amplifier; higher power systems will require higher wattage resistors. Also, bass-boost can be adjusted up or down by adjusting the 12.5 ohm resistor but higher values will reduce overall efficiency further.

Conclusion:
I had doubts about AMT performance versus an electrostatic when I started this project but the results have been beyond expectation. Getting good bass from a small enclosure was also a challenge but the A6 has more than enough bass for most usage except maybe hip-hop but that is not my listening preference.

About the Designer:
This project was designed and constructed by Craig J. Coley of Burleson, TX. I work as an electrical designer and am listed as inventor on 8 US patents in the field of electro-optics. I have been an electronics hobbyist since I built my first Heath radio at age 7 and a ham radio operator since age 11.

Project Parts List:

Designer:
Chadt

Project Category:
Subwoofers

Project Level:
Beginner

Project Time:
8-20 Hours

Project Cost:
$100 – $500

Project Description:
3 landzar max pro 10″ subwoofers wired to 6 ohms in a custom enclosure with 2 3″ flared ports that are 11″ long. Box made out of 3/4 sanded plywood with a 1 1/2″ front baffle. It has a honey satin finish.

Design Goals:
Loud bass

Driver Selection:
Landzar max pro 10″subwoofer

Enclosure Assembly:
Glued and screwed

Conclusion:
Came out looking and sounding awesome

About the Designer:
I have been building for a few years now. With every build I get better and always learn new things.

Designer:
Craig J. Coley

Project Category:
Loudspeakers/Cabinets

Project Level:
Beginner

Project Time:
1-8 Hours

Project Cost:
$100 – $500

Project Description:
This project is the Coley CH12 speaker. It uses a Seismic Audio Coax-12 PA speaker in a stock 1.8 cubic foot Belva automotive enclosure. A somewhat unorthodox crossover was designed to level the low frequency response of the stiff-hung low frequency driver. The amplifier used for casual listening is a small 25W/channel Class D driven by my iPad. For parties, I usually bring out my Coley W225 tube amplifier, also driven by my iPad. Since this is a single speaker intended for outdoor use, monaural drive was used for the amplifier.

Design Goals:
The origins of the Coley CH12 began with what may sound petty: I can’t stand crappy sounding jazz when I’m lounging around the pool. Not wanting to spend a lot of time or money, I chose a driver that was on sale for $120.00 and a 1.8 cubic foot cabinet, also on sale for $50.00; both came with free shipping. The crossover was my own design, incorporating bass boost, and modeled in SPICE to match the desired performance. The desire was to have a reasonably flat response from 42 Hz to at least 16 KHz and require no more than 25W drive.

Driver Selection:
Seismic Audio Coax-12

Enclosure Design:
The enclosure was a stock 1.8 cubic foot Belva BBX112BL subwoofer enclosure with a 42 Hz shelf type port. This enclosure was available for $50.00 with free shipping and made the construction fast and easy. Included was an internal absorber glued to the interior walls and rear speaker terminals. Any similar enclosure could be used; this one was chosen purely for economics. While this speaker does stay outside most of the time in the summer, it is protected from any direct contact with rain or pool water.

Enclosure Assembly:
The enclosure was received preassembled. To simplify wiring, most of the crossover components were glued to the rear of the Coax-12 with silicone RTV but the large bass boost circuit was screwed to the bottom of the cabinet. I did load the rear section of the port with Polyfill, not so much for a performance advantage but to keep wasps from making nests inside the speaker cabinet.

Crossover Design:
Since I personally like the sound and smooth transition of first order series crossovers, SPICE was used to model a series crossover design that takes into account the driver circuit characteristics. Balancing the very efficient horn loaded compression driver took several tries, both objectively with measurements and subjective by listening.
Since this was a PA speaker, the low frequency driver was very stiffly suspended and required compensation to extend the low frequency response. The low frequency network was an additional L+R circuit added to increase the available drive to the woofer below 100 Hz. The inductance of this circuit determines the transition frequency while the resistance value affects the depth. This L+R bass-boost circuit is fairly common with open-baffle designs and can be modified to tailor the enclosure used. Some driver efficiency is lost to boost the bass but even with a 25W amplifier, the performance is excellent.

Tips & Tricks:
This speaker is very easy to build. The L-Pad resistors specified in the design were chosen for use with a 25W amplifier; higher power systems will require higher wattage resistors. Also, bass-boost can be adjusted up or down by adjusting the 16 ohm resistor but higher values will reduce overall efficiency further.

Conclusion:
Even though my initial expectations were not high when using a PA speaker, the performance was excellent and far beyond the performance of a low cost store bought stereo. Even though some efficiency was sacrificed to flatten the driver response, the overall efficiency of the speaker was so high that little sacrifice was noticed.

About the Designer:
This project was designed and constructed by Craig J. Coley of Burleson, TX. I work as an electrical designer and am listed as inventor on 8 US patents in the field of electro-optics. I have been an electronics hobbyist since I built my first Heath radio at age 7 and a ham radio operator since age 11.

Project Parts List:

Designer:
Chris N

Project Category:
Guitar and Bass Speakers

Project Level:
Beginner

Project Time:
1-8 Hours

Project Cost:
Under $100

Project Description:
A traditional guitar cabinet with one 12″ driver.

Design Goals:
A versatile cabinet that could be used open back or sealed.

Driver Selection:
Eminence Legend 1258 290-486

Enclosure Design:
The enclosure is roughly 25″ wide, 19″ tall, and 9″ deep. The sides are made from solid Red Oak and Pine, laminated together. The top and bottom pieces are Birch plywood, the front and rear baffles are Pine plywood. The rear panel is removable, held in place with screws.

Enclosure Assembly:
The cabinet was joined together with biscuits for alignment, and held by glue and pocket screws. The finish is satin poly, wiped on with a rag, then rubbed with #0000 steel wool. The grill is made from scraps of wood, with fabric wrapped over it and held in place by staples.

Conclusion:
I’m pleased with the way this turned out. I prefer the sound with the rear baffle in place. It is plenty loud without needing much power, and sounds good with clean and dirty tones.

About the Designer:
Speaker building is a hobby I’ve never considered quitting.

Designer:
Raymond Thompson

Project Category:
Freestyle Speakers

Project Level:
Intermediate

Project Time:
1-8 Hours

Project Cost:
$500 – $1,000

Project Description:
This is the Tango MT Bookshelf Speaker Kit which is a 2-way system with a knock down cabinet to build.

Design Goals:
To complete the speakers in one weekend and improve the sound in the family room.

Driver Selection:
Dayton Audio RS180S-8 7″ Reference Shielded Woofer 8 Ohm
Dayton Audio RS28A-4 1-1/8″ Aluminum Dome Tweeter

Enclosure Design:
Part of kit

Crossover Design:
Part of kit.

About the Designer:
I am an electrical engineer. I use to work in the audio industry when I was young for several years, Sound has been a hobby for a ling time.

Designer:
Vaheed

Project Category:
Tower Speakers

Project Level:
Intermediate

Project Time:
20+ Hours

Project Cost:
Over $1,000

Project Description:
Project is about building a set of 3-way stereo speakers, as the name suggests they had to be perfect in everyway and I believe they are.

Design Goals:
The project has a “No Compromise” criteria, I wanted a detailed, natural sound on a sealed design to minimize the delay with 25hz-20khz extension at -+3dB

Driver Selection:
High frequency driver:
Morel CAT 308 1-1/8″ Soft Dome Tweeter (#277-082)

Mid frequency driver:
Morel TiCW 638Nd Titanium Series (#297-105)

Low Frequency driver:
Dayton Audio UM12-22 Ultimax (#295-512)

Enclosure Design:
To minimize the delay I chose the sealed design, Low frequency driver is sealed in the main enclosure and mid frequency is also sealed in another enclosure inside the main.
Enclosures are massive and heavy, each one weights closer to 400 lbs. Material used is 1″ MDF everywhere, tons of internal bracing with sluts and wave guides plus 3″ front baffles.

Enclosure Assembly:
I’ve only used glue and no screws. on joints I’ve used Titebond 3 and for layering, I’ve used Titebond melamine glue.
I’ve also used multiple layers of Bitumin paper and Melamine glue for vibration dampening everywhere and ofcourse pre-modelled extensive insulation.

Crossover Design:
It is an active dual mono 3-way crossover design.

Tips & Tricks:
Project was a huge success. I am very much happy with the results, Literature reviews took 3 months, design phase took 2 months and construction phase took another ~4 months.
Speakers are detailed and fast, base extension is lower than 25hz +-3dB in my living room, mid frequencies are to die for and high frequencies are silky and smooth, you simply can not stop listening to them.

About the Designer:
I am crafty and have experience in wood working.
This was my first serious speaker building project.

Designer:
chadt

Project Category:
Tower Speakers

Project Level:
Beginner

Project Time:
8-20 Hours

Project Cost:
$100 – $500

Project Description:
towers are made out of 3/4″ mdf and are glued and screwed together.housing three 8″ goldwood heavy duty midrange speakers and one 1″ typhany silk dome tweeter.its a 2 way setup and i am using a dayton 4500hz crossover.the towers are ported, each has two 2″ ports that are 5 1/2″ long. they have gold plate terminal cups and rubber cabinet feet. they stand 38″ tall and are 15 1/2″ deep and 10″ wide. finished in black duratex. they are wired to 6 ohms each

Design Goals:
build amazing sounding and powerful tower speakers. that look good as well

Driver Selection:
6 goldwood heavy duty 8″ mids

Enclosure Design:
3/4″ mdf
38″ tall
15 1/2″ deep
10″ wide
2 2″ ports 5 11/2″ long in each tower

Enclosure Assembly:
glued and screwed together

Crossover Design:
dayton 4500hz crossover in each tower

Parts Used:
6 heavy duty 8″ mids
2  1″ silk dome tweeters
2 dayton audio 4500hz crossovers
4 port tubes
8 cabinet feet
duratex black
speaker grill cloth
speaker grill mounting hardware

Conclusion:
amazing sound and great looking.

About the Designer:
love building speakers, been doing it for a few years now. it is just a on going evolving thing. plus you learn as you go and get better and better.

Designer:
JayTee

Project Category:
Tower Speakers

Project Level:
Beginner

Project Time:
1-8 Hours

Project Cost:
Under $100

Project Description:
I purchased a pair of Dayton Audio T652 tower speakers at a restocked bargain price ($63) and was quite impressed with the bass and overall sound they produced. I’m a big fan of open, airy sound stage when listening to music, so I thought “Why not use these speakers to create a modified open baffle design with little to no extra investment?”

Design Goals:
To incorporate all the elements of the Dayton T652 into a modified open baffle setup resulting in the expanded, room filling sound stage offered by open baffle designs at an “ultra budget” cost.

Driver Selection:
All components of the Dayton Audio T652 speaker pair were re-used. Wiring was performed without schematic alterations.

Enclosure Design:
The bass reflex cabinet of the Dayton Audio T652 was re-used and attached to the rear of a a 45″ tall by 19 inch wide tapered board design.

Enclosure Assembly:
Very little to do here other than to lay out the new board, cut it , trim it with boarder trim, Cut the driver and port tube holes, and paint it to whatever color is desired ( I used a shade of gray). The existing Dayton cabinet only required a 5-3/4 inch round hole in the top to be cut for re-attaching one of the existing drivers.

Crossover Design:
Same first order crossover used in the Dayton T652 (re-used).

Tips & Tricks:
Accurate measurements of the location of the front port and tweeter locations on the Dayton Audio T652 cabinet front are required in order to layout and cut the new openings on the front attached wood baffle. The port tube is glued into the Dayton cabinet. I used a drill to pilot a hole and a jig saw to cut about 1/4 inch around the port tube to remove it and then broke-off the remaining MDF cabinet pieces attached to the port tube with vise grips. A 5-3/4 hole must be cut in the top of the Dayton cabinet to acomodate an upward firing driver. The existing wiring needed to be modified to lengthen the leads from the terminals to extend out the top of the newly cut opening in order to re-attach (solder) all drivers. This can be done my splicing or by remove/re-attaching at the speaker terminals (this must be done before attaching the Dayton cabinet to the new front baffle board). I drilled 6 new holes in the front of the Dayton cabinet and used 6 ph ilips head screws no deeper than the combined depth of the Dayton cabinet and the new front baffle board to attach the cabinets to the board (also used foam weatherstrip tape to fully seal the cabinet front to the new board and eliminate any additional vibration potential). I needed to use a “stubby” phillips screw driver and reached down inside the cabinet to tighten all 6 screws to finish attaching the front board (this hides all of the screws completely). I used hole saws from my standard hole saw kit to cut the new openings for the tweeter and port tube in the front board, which is aligned and attached directly over the original Dayton Audio T652 mounting holes. I used a drilled pilot hole and jig saw to cut the woofer holes in the new front boards and the top of the Dayton cabinets.

Conclusion:
They look and sound great to me!….I wasn’t planning to do a photo step by step so I only have a front and back view of the finished product to share.

About the Designer:
I’m just about a complete “newbie” and have only performed re-foams and cap replacements to this point. I don’t make any claims that the work I performed in this project should be done by others, but I personally love the results for both sound and appearance in my den. Dayton Audio makes a great budget product with their T652 speakers and I simply sought to improve them to my taste and share the results from a happy DIY customer.

Parts Used:
All components of the Dayton T652 speakers.

Plus some scrap T-111 and wood trim ( yeah, I know it doesn’t have the acoustics of MDF but it’s what I had available and it works) and a few screws, 2 4′ pcs of 16 awg speaker wire, solder, weather stripping and paint.

Designer:
Dan Poinsett

Project Category:
Bookshelf Speakers

Project Level:
Intermediate

Project Time:
8-20 Hours

Project Cost:
$500 – $1,000

Project Description:
UX3 is a compact stand-mount 2-way loudspeaker utilizing a 7″ woofer and a large format ribbon tweeter.

Design Goals:
My design goals with this project were to build a compact high end speaker with high output potential

Driver Selection:
I chose the Fountek Neo X 3.0 ribbon tweeter because I wanted to use a ribbon tweeter, but needed one robust enough to cross to a 7″ woofer in a high output design. This tweeter seemed to have good reviews and has a relatively large diaphragm so I gave it a try.

The Usher 8836AC was chosen due to it’s wonderful reputation and truncated frame, allowing closer placement to and better visual cohesion with the Fountek tweeter.

The shape of these drivers allowed me to install them both on a very svelte trapezoidal baffle.

Enclosure Design:
The enclosure design was straightforward in that it is a simple sealed box of approximately 1/2 cubic foot. The angles of the enclosure are a little more complex than usual though, as are the recesses for the drivers.

The enclosure is a trapezoidal prism, 14″ tall, 13.5″ deep, and increases from 4.25″ wide at the top to 10.5″ at the bottom (external dimensions). I used 18mm Baltic Birch for the top, bottom and sides and 3/4″ MDF for the front and real baffles. A single trapezoidal brace joins the two sides from the top of the enclosure to about the middle. I lined the enclosure with 3.5″ thick fiberglass, which filled about 75% of the internal volume. Measured F3 is about 48Hz and the Qtc is about 0.9 which gives a very full, warm bass.

Enclosure Assembly:
I used miter joints to join the top panel to the 2 sides, but used butt joints to join the bottom panel to the 2 sides because I wasn’t comfortable using a miter on the sub-90 degree angle at the bottom of the trapezoid. Once the top, bottom and sides were glued with wood glue, I cut the front and rear MDF baffles oversized and trimmed them to size. I then cut 45 degree chamfers around the baffle edges.

I made router guides of particle board for the non-circular recesses required by both woofer and tweeter. After cutting the through holes for the drivers, I clamped the guides in place and cut the recesses. The nice thing about using a guide is if the opening is too small, you can shift the guide over a hair and remove a little more material.

I will admit laziness on the finish, even though it doesn’t look too bad. I used a grey stain on the Baltic Birch and flat black spray paint on the baffles. This shape enclosure is quite attractive and would actually look very nice with a quality finish, but that wasn’t in the cards this time around.

Crossover Design:
The crossover turned out to be quite a dichotomy of complexity and simplicity. I knew I wanted to cross the drivers higher than normal for a 7″ 2-way to allow the ribbon to perform at higher output levels, so I began playing with woofer lowpass frequencies at about 3kHz. After a lot of simulations, I found that the most well behaved roll off in that vicinity was to be had with a single inductor and nothing else. The value I settled on was 2.0mH to get the right integration with the tweeter.

The tweeter on the other hand was very difficult. It has a natural rise of about 8dB on each end of its passband, leaving a deep valley that I had to level the response to. In the end, an aggressive 3rd order electrical highpass took care of the low end peak and an aggressive zobel tamed the upper peak. Three resistors provided the padding and kept the other elements at reasonable values, leaving the total parts count at 8. This is more than I usually like to have on a single driver, but it was absolutely necessary in this case and since there is only one coil, the overall cost remains pretty low.

The crossover topology ended up being asymmetrical 3rd/4th order acoustic at about 3.4kHz. This allows the tweeter to be pushed very hard without strain and did not affect the power response too poorly as can be inferred from the off axis plots in the graph above.

Tips & Tricks:
The 2.4 ohm tweeter in front of the tweeter xo can be altered to raise or lower the tweeter level without altering the transfer function (other than a static gain/loss). At 2 ohms, the on axis FR is actually a little flatter, but I found it to be a little bright in my listening space and 2.4 ohms brought it right in line. I suggest ordering a 2 ohm and a 2.7 ohm along with the 2.4 ohm for experimentation.

http://www.ohio.edu/people/schneidw/audio/routing_truncated_recesses.html
This tutorial, posted by fellow PETT member williamrschneider is the best method (and best documented) I have seen for creating guides to recess straight edged drivers. Both the woofer and tweeter in UX3 were recessed perfectly using this method.

Conclusion:
This project was a lot of fun to build and is very satisfying to listen to.

The Fountek tweeter is detailed and delicate and worth the added trouble in the crossover. I’m hearing details in music I never noticed before and not in the sterile way that detailed sometimes comes across as. The sound is very dynamic as well without the least bit of strain at higher level than I care to listen. With an inherent 95dB sensitivity (even more with the peaks at each passband extreme) and crossed at 3.4kHz, these large format ribbons are producing a very large sound with very little energy input. This format does have its disadvantages as well, however. Vertical dispersion is poor and the comb filtering induced by a necessarily large CTC distance and a highish xo point exacerbates this weakness as you move above the listening axis. The difference between standing and sitting is not subtle. If they cannot be placed on stands tall enough to elevate the tweeters to ear level, then they should be tilted back slightly to accommodate.

The Usher woofer is a beast and one I wish I would have tried sooner. It provides prodigious amounts of bass in this small enclosure and sooooo smoooooth. It exceeds xmax gracefully and keeps on going. The midrange it produces is no slouch either and blends seamlessly with the delicate tweeter, but that bass! I keep playing one bass heavy track after the next, trying to find its limits and loving what I’m hearing. I will admit that the 0.9 Qtc is giving me a little boost down low AND helping to control the cone, but still! That bass is sweet!

Overall the combination of extra sweet, delicate highs and smooth, pounding bass is one that is very fun to listen to. These drivers deserve their reputations and price tags and this is about as small a package you could combine them in.

About the Designer:
I have been building speakers for over 20 years and I am a member of the PE Speaker Building Design Team.

Parts Used:

Designer:
Scott Sehlin

Project Category:
Home Theater

Project Level:
Intermediate

Project Time:
8-20 Hours

Project Cost:
$100 – $500

Project Description:
The Helium Soundbar is a DIY soundbar that features the SMSL Q5 Pro DAC/Amplifier, which has a great feature set for typical soundbar funcationality and a variation of the Helium Micromonitor design to give big sound in a small package.

Design Goals:
I wanted to build a soundbar with a height and depth of approximately 4″x4″ and a length of approximately 2 feet in order to create something that would work either hanging on the wall under large or small flatscreen TV’s or on a desktop hooked to a computer. I wanted the ability to add a subwoofer, but also wanted enough bass capability so that music or tv would still be somewhat enjoyable without a sub – a major step up from what is built into TV’s or monitors.

Driver Selection:
The size requirements eliminated most woofers from consideration. The Dayton ND-91 drivers work really well in the small boxes. Not only do they produce a lot of bass, but they also handle quite a bit of power before complaining – especially considering that it is a 3″ driver. I decided to go with the 8 ohm version (290-226) for this project to minimize the current demands on the small SMSL amplifier.

The Dayton ND16FA-6 (275-025) is a small, inexpensive tweeter that sounds good and has wide dispersion, which is desirable in a soundbar application for room-filling sound.

Enclosure Design:
The approximate dimensions of 4″x4″x24″ were chosen to be less than or equal to the width and mounting depth of most typical screen TV installations. The 4″ height would allow placement in front of some screens without obstructing the picture. The tweeters and woofers are placed close to the edges of the enclosure to maximize stereo separation. There are two solid braces on either side of the amplifier to isolate the woofer’s air space from each other and minimize any air leaks that might occur around the amplifier. Ports fire out the ends of the enclosure, which allows the use of simple, straight 3/4″ by 4″ PVC sections. The actual cabinet depth was extended to 4.75″, which allowed the connectors on the rear of the amplifier to be completely recessed into the rear surface of the enclosure.

Enclosure Assembly:
The enclosure was build using 1/2″ plywood. Plywood was chosen primarily to reduce weight relative to fiber board products. Enclosure construction was mostly straightforward. Four 4″ by 24″ pieces were cut to form the top, bottom, front and rear of the enclosure. Four 3″ by 4″ pieces were cut to form the ends of the enclosure and the two internal braces. The ND-91 requires a simple 3″ mounting hole and the ND-16 uses a 1.25″ hole, which fits just right with a little sanding. The rectangular cutouts for the amplifer would be a little challenging to get exactly right with normal tools, so a CNC router was used.

I decided to make the rear panel removable, so 1/4″ deep by 1/2″ wide rabbets were cut around the edges of the rear panel and in the areas where the braces intersect with the rear panel. The rabbets allow the rear panel to only add 1/4″ to the overall depth of the enclosure and create a more secure connection between the rear panel and the rest of the cabinet.. Weather stripping was used on the surfaces contacting the rear panel to eliminate leaks or the possibility of any noises caused by an imperfect fit.

Crossover Design:
The crossover schematic is shown in a figure included in this writeup. The woofer has a 2nd order filter and the tweeter has a 3rd order filter with series and parallel resistors to match the tweeter and woofer sound pressure levels. These filters result in an approximately 4th order crossover at 5 kHz, which is well within the comfort zone for both of these drivers. The resulting response is +/- 3dB from the lowest point where my gated response measurement is accurate (about 300 Hz) to 20 kHz.

Conclusion:
The overall sound is similar to the Helium Micromonitors – maybe a little bit deeper bass extension. The SMSL Q5 pro is really the ideal electronics package for this application. It has optical and coaxial digital inputs along with USB and analog inputs. Remote control and a subwoofer out are other key features. There is enough power to get solid volume out of the relatively inefficient ND-91’s. A bluetooth module can be added if desired to one of the inputs (in most cases, this would be hooked to the analog input). All-in-all, this will significantly outperform similarly priced and sized commercial soundbars and is not too difficult to build if you can make the rectangular cutouts for the front and rear of the amp or have them made.

About the Designer:
Scott is an Engineering Manager for a manufacturer of aerospace equipment. He has been designing and building speakers for over 12 years and was a 2015-2016 member of the Parts Express Speaker Building Design Team.

Project Parts List:

Designer:
Erock

Project Category:
Portable Speakers

Project Level:
Intermediate

Project Time:
8-20 Hours

Project Cost:
$100 – $500

Project Description:
Portable DIY BT boombox housed in a hard plastic tool box. The design was built around the Wondom AA-AC111

Design Goals:
I wanted to build a portable BT boombox for a friend that owns a tile contracting company. The idea was to create a portable boombox he could take to job sites that would be durable and rechargeable for greater portability.

Driver Selection:
Dayton Audio ND90 8ohm 3-1/2″ full range driver

Enclosure Design:
Repurposed hard plastic tool box

Tips & Tricks:
The Parts Express support team was super helpful. They helped me calculate the proper bass port design and the issue with the bad aux cable.

Conclusion:
The amplifier has decent output. The BT range is not as
good as the specs say. The aux cable included with the board was wired incorrectly. I had to cut the wires and re-wire in the correct pinout to the connecter.

About the Designer:
I’ve been tinkering with electronics for the past 10 years. I design and build coustom effect pedals for guitar and bass, as well as low watt guitar amplifiers. I love DIY and re-proposing old radios and storage objects for audio electronic projects.. I’m not an experienced speaker builder but I’m working on it.

Project Parts List:

Designer:
JDCrae

Project Category:
Loudspeakers/Cabinets

Project Level:
Intermediate

Project Time:
20+ Hours

Project Cost:
$100 – $500

Project Description:
Converting a late 60’s Stereo Console into an updated Stereo. Needed to procure a sufficient power source, speaker design that would fit the parameters of the cabinet, and then finish to a beach house distressed appearance.

Design Goals:
The goal of this project was to turn a 1968 Stereo Console into a hifi piece of furniture for our living room. We were looking for an aesthetically pleasing appearance, wide sound dispersion and capable low end response.

Driver Selection:
The speaker design was suggested by Chris Roemer, which called for 295-310 – Dayton 8 inch Woofer. The 275-075 – Dayton Tweeter was chosen because the unshielded version was on a pretty extended backorder. Went with 268-350 – Ports and cut those to 8.5 inches per the crossover design

Enclosure Design:
The enclosures were essentially already determined by the cabinet speaker cavities. It was originally a 2.5 way so I need to close off the extra opening in the baffle. Luckily the openings were smaller than what I needed, so I simply routed out the proper sized openings using a rabbeting bit. I preferred the port to exit on the rear of the cabinets to a 3 inch hole was cut to slide the port in. It was a very snug fit so I didn’t need to secure the port with anything. The dimensions of the cabinet compartments were 9 inches Wide, 13 inches deep and 21 inches tall externally. This was close enough to the original size recommended that I felt confident the sound would not change greatly.

Enclosure Assembly:
Luckily, besides some plugging of the previous front firing port, and routing out the new driver openings, there was little assembly to mess with. I did redesign the rear of the cabinet to be rear port firing, and added gasket tape to seal up the back of each “enclosure”

Crossover Design:
The Crossover design was done by Chris Roemer. Picture attached below shows the values and placement. Please remember my dimensions were different than the originals called for, so this design can no longer be described as for critical listening in my application.

Tips & Tricks:
If I were to do it all over again, I would more than likely completely build the cabinet from scratch. It would have been cheaper in the long run given the amount of paint and distressing I had to do to given faux maple laminate a grain. If you were going to simply paint it, modifying would be cheaper

Conclusion:
Overall, my wife and I are completely thrilled with the outcome of this project. I will be changing out the amplifier for something diy in the future, but for the moment, this old Yamaha NS is working perfectly. While not for critical listening, this radio puts out an amazing amount of sound, is accurate, provides ample low end response and most importantly provides much enjoyment for our family. We like the fact that 50 years ago people circled around this very console to listen to music and spent time together, and we will be continuing that fine tradition.

About the Designer:
I am a veteran of the USAF, and am in Marketing within the Recycling Industry. A woodworker on the side, I enjoy all aspects of building and modifying things. I am in no way a speaker designer, much more a builder.

Project Parts List:

Designer:
Mike P

Project Category:
Tower Speakers

Project Level:
Intermediate

Project Time:
20+ Hours

Project Cost:
$500 – $1,000

Project Description:
The Mavericks – 5 driver, 4-way floor standing tower speakers

Design Goals:
There were two things I hoped to accomplish with this build. First, I wanted to build a pair of floor standing tower speakers utilizing all of the Dayton Audio drivers I purchased at the 2015 PE Midwest Audiofest. Second, I wanted to incorporate the suggestion that I received from the speaker competition judges on my first tower build which was to improve the cabinet astetics.

Driver Selection:
RS100-4 mid-range 295-378
RS150-4 mid-woofer 295-372
RS225-8 woofers 295-356
ND25FA-4 soft dome tweeter 275-059

Enclosure Design:
To utilize all of the speakers, I chose a 4-way design with a 5 driver layout having a mid-woofer at the top followed by a tweeter, a mid-range and then dual woofers. For improving the cabinet, I used beveled joints at the top, not butt joints as I had in my first tower build.

Enclosure Assembly:
I used ¾” five ply walnut vineer plywood with cabinet dimensions of 40”H x 11”W x 14”D. I first ripped the plywood sheet on my table saw. Then, I used my radial arm saw to cut the cabinet pieces to the approximate lengths leaving some extra to be trimmed after I cut and dry fit the angles.

I cut the angles using the table saw. Wood glue was used to secure the sides and tops. I used painters tape to keep the pieces square while they dried. A tip for doing this: lay the top and side beveled edge pieces together flat. Place some painters tape along the edge where the two edges meet. Then apply the glue and fold the top up 45°. The tape acts as a hinge. Use a square to get the side perfect, then use tape to secure and let set until the glue dries.

Wood glue was used to assemble the sides and back. Using liquid nails, I installed battens to the inner seems to hold, seal and increase the cabinet strength. I also cut small triangular pieces and secured them in the corners for added strength. I added several more later after the mid-woofer and mid-range/tweeter compartments were completed. This provided additional strength to the enclosure and surface area for gluing the front baffle to the cabinet.

For the mid-woofer and mid-range/tweeter speakers, I created sealed upper compartments. The volume of these compartments did not require porting. Two large holes were cut in each of the lower portions of the compartment walls to allow the space behind them to become part of the volume for the woofers.

Before gluing into place, I lined the walls behind these holes with acoustic dampening polyfill. A brace was added in the woofer compartment connecting the cabinet side walls to further increase strength and to reduce cabinet vibrations. Additional triangle braces and battens were added for support and for gluing surface area of the front baffle. Note that the comparments and triangular support pieces were set 3/4” below the top of the sides to allow for flush mounting the double thick front baffle.

All of the speakers were flush mounted. I used the Jasper Circle Jig model 200 and a router for cutting the precision holes. Parts Express sells this jig and has a very good demonstration video of this jig in action on its web site. I carefully determine the layout of the drivers on the front baffle and after I made several practice cuts in scrap wood using the jig, I began cutting the holes. When cutting, be sure to allow for the speaker edge width and thickness as well as the depth. PE typically provides these dimensions in the speaker literature or you can usually find the specification drawings from the driver manufacturer linked within the PE e-catalog. I measured the actual speakers and looked at the specs, set the router bit accordingly and ran a few test cuts.

Since the baffles were double thickness, I had to cut holes in four pieces of wood, then secure the pieces together. This was done with wood glue and wood screws. Notice the inside baffle is set in ¾”. This area will be glued to the battens and triangular pieces making for a very strong and low vibration front baffle.

After the front baffles were assembled, I dry fit the speakers. Some small adjustments were needed to allow the speakers and wire terminals to set just right. Sandpaper and hand files were used to make these small adjustments.

I covered the front baffles in a black vinyl imitation leather material, something that I had seen and liked on some high end speakers. I took into account the thickness of this covering material when cutting the speaker holes.

Due to the design being a 4-way and the cabinets having individual closed compartments, I determined it would be best to build the woofer and mid-woofer crossovers separately but combine the mid-range and tweeter crossover onto one board. Then mount each board in the individual compartments. I purchased some DIY FR4 pre-drilled circuit boards from Amazon. These worked as a perfect base for constructing the crossovers. Standard 16 gauge speaker wire was soldered to each of the driver connections on the crossover. For mounting the circuit boards, I used 1” wall anchors cut in half as standoffs and wood screws for mounting. Small holes were drilled for routing the wires to the upper compartments.

I had to modify the mid-woofer crossover near the end of the build when, during listening tests, I found the mid-woofer did not like the low frequencies ≤600hz and was distorting badly. I rectified this by blocking those frequencies with a filter placed in front of the crossover (C4 and L4). Having already completed and mounted the mid-woofer crossover, I mounted this filter in the woofer compartment and wired it between the terminal conections and the mid-woofer crossover. It worked well, completely eliminating the distortion.

Acoustic dampening materials – Polyfill was stapled to the inside walls of the cabinet, the back of the driver baffle and inside the area behind the mid-woofer, midrange and tweeter enclosures before gluing and sealing those compartments. Fixed cell foam material was also added to the mid-woofer and midrange/tweeter compartments to further reduce and dampen unwanted low frequency vibrations.

Tuning Port – The tuning port is located on the back of the cabinet. Matt at PE calculated the port size. I provided him with the woofer cabinet volume and the part number of the woofers. Matt determined a 3 inch diameter 9.5 inch long flared port would provide a tuning frequency of 28 hertz.

Wood finish – I wanted the cabinets to be black. So, I applied two coats of black paint to the cabinets and a clear coat of Minwax polyurethane sealer a few days later.

Speaker installation, wiring and final assembly – The drivers were carefully positioned on each of the front baffles and pilot holes drilled for the screws. A hand screw driver was used to install the screws. More control of screw pressure is achieved by hand tightening vs using an electric drill. One slip with a drill driver and a speaker or the vinyl on the baffle could have been ruined. Each driver connection was soldered. Liquid Nails was used for gluing the baffles, side walls, back wall and all other support pieces. Ten large clamps were used to hold the units while the glue hardened. Custom made speaker spike support bars have been constructed but not yet installed.

Crossover Design:
For my first tower project, I had purchased a pre-assembled 3-way crossover. For this project, I wanted to design and build the crossover myself. Since these speakers will be used with a vintage stereo integrated amplifier without a subwoofer connection, the design is a 4-way.
I studied the spec sheets for all of the DA drivers I had purchased and I choose the following crossover points based on the frequency response for each driver:
• Woofer low pass <600hz
• Mid-woofer band pass 600hz – 2.6khz (originally was low pass ≤2.6khz but changed during listening tests)
• Midrange band pass 2.6khz – 6.0khz
• Tweeter high pass >6.0khz

I used several “freeware” and “app” crossover calculators as well as the Parts Express crossover tables to determine the crossover component values.

Conclusion:
I was very happy with the final product. The sound quality and bass greatly exceeded my expectations. On the construction end, the enclosures are very solid and cabinet astetics are much improved verses my first tower build (see “4 Driver, 3 – Way Floor Standing Tower Speaker” in the PE project gallery). The vinyl material on the front baffels provide a very nice and asteticly pleasing appearance. The black finish matches my other home theater components. Currently the speakers are connected to to a Russound two input, 6 speaker out speaker switch so I can run them through the vintage amp and my AV receiver.

About the Designer:
Since my teenage years, I have been interested in electronics, specifically stereo equipment, speakers, amps, etc. I still use my 1978 integrated amplifier as my primary audio source for playing CDs and vinyl. I like the simplicity of the vintage equipment along with the sound and build quality, real aluminum knobs, aluminum face plates, the feel of quality. The pursuit of better quality is what drove me to try my hand at building speakers. Thank you Parts Express for your support in this hobby.

Parts Used:

Jantzen Audio 0.15mH 20 AWG Air Core Inductor Crossover Coil 255-022
Jantzen Audio 0.25mH 20 AWG Air Core Inductor Crossover Coil 255-026
Jantzen Audio 0.40mH 20 AWG Air Core Inductor Crossover Coil 255-032
Jantzen Audio 1.5mH 20 AWG Air Core Inductor Crossover Coil 255-052
Jantzen Audio 0.13mH 18 AWG Air Core Inductor Crossover Coil 255-204
Jantzen Audio 0.18mH 18 AWG Air Core Inductor Crossover Coil 255-208
Clearance 1.0mH 20 Gauge Ferrite Core Inductor 269-2124
Audyn Cap Q4 4.7uF 400V MKP Metalized Polypropylene Foil Capacitor 027-114
Audyn Cap Q4 6.8uF 400V MKP Metalized Polypropylene Foil Capacitor 027-116
Audyn Cap Q4 10uF 400V MKP Metalized Polypropylene Foil Capacitor 027-118
Audyn Cap Q4 47uF 400V MKP Metalized Polypropylene Foil Capacitor 027-122
Dayton Audio DMPC-20 20uF 250V Metalized Polypropylene Capacitor 027-436
Dayton Audio DMPC-40 40uF 250V Metalized Polypropylene Capacitor 027-442

Designer:
Craig J. Coley

Project Category:
Amplifiers

Project Level:
Advanced

Project Time:
20+ Hours

Project Cost:
$500 – $1,000

Project Description:
This project is the Coley SET125 Mono-Block Amplifier. It is a one channel single ended triode (SET) amplifier using a Soviet era directly heated GM70 triode. It can easily produce a continuous output power in excess of 20W while operating full Class A at low distortion. The sound of the amplifier throughout its power range is warm, clear, and transparent; an excellent choice for driving a bass-compensated open baffle speaker.

Design Goals:
The goal of this design was to produce a high power Class A SET amplifier that could easily drive a compensated open baffle speaker to high volume. The Soviet GM70 and Chinese 845 tubes were considered good candidate tubes. The NOS Soviet era GM70 was chosen because of its ability to operate easily at 100W continuously, thereby allowing a Class A output approaching 25W peak. The GM70 with carbon anode can usually be acquired on eBay for around $50.00 from the Ukraine, including shipping. Four GM70 and four 6N8S tubes were ordered so that multiple tubes manufactured at different times could be tested. The ultimate goal is the construction of a pair for stereo operation. It was decided from the beginning to use 6-8dB of negative feedback to compensate for transformer overshoot and speaker load dumping that is common at low frequency. The power supply voltage required for the GM70 is 950V, easily lethal, and construction should only be attempted someone who is familiar with the safe operation of high voltage circuits.

Driver Selection:
A Hammond 1628SEA was chosen for the output transformer, a Hammond 278X chosen for the power transformer, and Hammond 187F20 chosen for the GM70 filament. For power supply filtering, a 6 Henry Triad Magnetics C14X was chosen due to its low cost and 1500V rating.

Enclosure Design:
A black Hammond 12x8x3 steel chassis was chosen due to the weight of the magnetics and it was believed to represent about the smallest enclosure that could be used for an amplifier of this type. Greenlee knock-out punches were used for all tube socket holes and transformer wire entries. A 1:1 2D CAD drawing was made for all sides of the enclosure which aided greatly in packaging and pre drilling the small chassis. Printouts were made of the drawings, taped to the sides of the chassis and then used as drill guides for all hole centers.

Enclosure Assembly:
Once all holes are predrilled in the Hammond chassis, the tube sockets and magnetic can be mounted in preparation for wiring. Neoprene grommets should be used for all transformer wire entries due to the high operating voltage. All power resistors greater than 5W are metal and screwed to the chassis to dissipate heat. A 15W voltage divider from the 950V supply is used to power the 6N8S preamplifier stage. This method was chosen to both stabilize the 950V supply as well as provide a rapid bleeder for stored energy when the power is turned off. The power supply capacitors are 220 microfarad, 500V aluminum electrolytics and the capacitor connections are covered with a clear plexiglass cover for safety.

Crossover Design:
The design of the amplifier relied on experience and vacuum tube models available for LTSpice, a free SPICE simulator. SPICE simulation enabled resistor value optimization, feedback prediction and stage gain to be determined for the design power level. While both cheaper and more expensive magnetics were available, the availability, modest price and performance of the Hammond products made their selection easy. While somewhat uncommon in an SET amplifier, a modest amount of negative feedback was used that helped to flatten the gain and compensate for magnetic energy stored in the output transformer and speaker system. The measured performance was within 1dB from 20 Hz to 20,000 Hz and could produce greater than 20W continuous power (the limit of my power meter) at 1.25% THD.

Tips & Tricks:
The construction of this amplifier is straightforward but should only be attempted by an expert builder who is familiar with the safe handling of high voltage. Most builders might also desire a larger case for packaging ease and this is recommended wherever practical.

About the Designer:
This project was designed and constructed by Craig J. Coley of Burleson, TX. I work as an electrical designer and am listed as inventor on 8 US patents in the field of electro-optics. I have been an electronics hobbyist since I built my first Heath radio at age 7 and a ham radio operator since age 11.

Parts Used:

Qty(1) Hammond 1628SEA.
Qty(1) Hammond 278X, P/N 122-240.
Qty(1) Hammond 187F20
Qty(1) Triad Magnetics C14X
Qty(1) Soviet GM70 Triode
Qty(1) Soviet 6N8S Dual Triode (or 6SN7), P/N 072-845


Designer:
Craig J. Coley

Project Category:
Loudspeakers/Cabinets

Project Level:
Beginner

Project Time:
1-8 Hours

Project Cost:
Under $100

Project Description:
This project is called the Coley OB15 Open Baffle Speaker. It is a full range speaker with a manageable baffle size and integral electronic compensation for baffle losses. In addition, the impedance curve of the speaker presents itself as a light resistive load at high frequency, making it a good match for single-ended triode amplifiers with little or no negative feedback.

Design Goals:
This project began as a desire to experience the transparency of an open baffle but with full range performance. Limited space meant limited baffle size so it was known from the beginning that compensation would be required. A theoretical efficiency loss of 10dB was deemed acceptable so long as the response was reasonably flat and extended to at least 50 Hertz. In addition, it was desirable to drive the open baffle with a single-ended triode (SET) amplifier. Since it is common for SET amplifiers to use little to no negative feedback, the open baffle impedance needed to remain at 8 ohms or greater at high frequency since amplifier impedance stabilization caused by negative feedback would not occur.

Driver Selection:
While some efficiency was willingly sacrificed to obtain a wide frequency response, these losses can become excessive in the last few octaves below 100 Hertz. To minimize these losses, a large woofer was sought with a higher Qts in the 40 Hertz range but not so excessive that a noticeable hump would be created in the response curve. The Goldwood GW-215/40/8 (P/N 290-346) with a Qts of 1.087 around 40 Hertz met these requirements at a very modest price. The tweeter selection was based upon the desire to have high detail and transparency along with dipole characteristics. The Beston RT002A (P/N 277-116) ribbon tweeter met these requirements with a wide, flat frequency response, and at a very modest price.

Enclosure Design:
As an open baffle prototype, the enclosure consisted of nothing more than wooden panels for each speaker driver mounted to a desktop rack. An edge glued pine panel of 19x16x0.75 inch was used for the woofer and a cedar panel of 19×5.5×0.75 inch was used for the tweeter. Edges of the panels were finished with a router and round-over bit. The 0.75 inch thickness of both wooden panel types allowed easy mounting of components to both sides of the panel but does require countersinking of the rack mounting holes. Because solid wood is used, predrilling of holes is mandatory. MDF would be a better choice for most builders but was not a choice here due to people with formaldehyde sensitivities in my home. Two stains were tried for appearance, a simple light stain and a hand rubbed dark stain to produce a faux antique look. Once stained, inductors and resistors were screwed to the rear of the baffle panels and the large capacitor was soldered directly to the w oofer leads and cemented in place with silicone RTV. The binding posts for the cable were mounted on the lower left corner of woofer panel to be near the floor but any convenient location will work.

Enclosure Assembly:
Assembly is quite easy for anyone with minor woodworking skills. Once the driver and crossover electronics are mounted to the wooden panels, they are then screwed to the Tripp-Lite 12U desktop rack with the tweeter panel mounted above the woofer as shown in the photos. The overall size of each open baffle speaker is 20x24x12 inches, the depth of 12 inches being the support feet of the rack.

Crossover Design:
Since I personally like the sound and smooth transfer characteristics, an 1100 Hertz two-way shunt crossover was used. Crossovers of this type interact with the electrical characteristics of the speaker drivers so once these parameters are measured, the entire circuit can be modeled in SPICE to optimize the component values and performance. Multisim Touch, a National Instruments product, is available free for the iPad and was used for this purpose. In addition to the shunt crossover for the drivers, a series RL network was included to compensate the baffle losses that roll-off at 6dB per octave. The conjugate 6dB per octave reactance characteristics of the RL network will flatten the natural roll-off and thus flatten the frequency response of the entire system. When using RL networks of this type, some trial and error is unavoidable as is some loss in driver efficiency. A 10dB loss was deemed acceptable to have the necessary low frequency extension to make the Coley OB15 a full range speaker. Although the RL components are not available from Parts Express, they are easily available from sources like Mouser. The 50 ohm resistor used in the network is metal and highly recommended due to the higher heat dissipation capability.

Tips & Tricks:
There is nothing special about using a rack for these speakers, construction could have just as easily been all wood which would allow omitting the rack. As long as the approximate width and height are maintained, the performance will be nearly identical. For those concerned about maintaining a constant load over frequency, a 12 ohm load across the speaker terminals can be added with little or no change in performance; simply size the resistor wattage according to expected power. Like any open baffle, it is best to place the speakers at least three feet from the wall for best results.

Conclusion:
The performance of this speaker was beyond my initial expectations. For someone who is accustomed to the bass characteristics of a ported enclosure, the transparent and encompassing bass of an open baffle was a pleasant surprise. The sound from this open baffle speaker surrounds the listener and it is easy to imagine yourself in a smoky bar listening to a live jazz band.

About the Designer:
This project was designed and constructed by Craig J. Coley of Burleson, TX. I work as an electrical designer and am listed as inventor on 8 US patents in the field of electro-optics. I have been an electronics hobbyist since I built my first Heath radio at age 7 and a ham radio operator since age 11.

Parts Used:
Goldwood GW-215/40/8 15” Woofer, P/N 290-346
Beston RT002A Ribbon Tweeter, P/N 277-116
Dayton 40 uF, 250V Poly Capacitor, P/N 027-442
Jantzen 0.6mH Inductor, P/N 255-412
Triad C-56U 35.0mH Inductor
Vishay/Dale RH02550R00FC02, 50 Ohm, 25W Resistor
Tripp-Lite SR2POST12, 12U Desktop Rack

Designer:
TomZ

Project Category:
Bookshelf Speakers

Project Level:
Beginner

Project Time:
Beginner

Project Cost:
Under $100

Project Description:
I would describe this system as a ‘micro’ speaker system without the ‘micro’ sound. It produces deeper bass and more detailed highs than most tiny speakers of this size. The idea for this speaker formed over time as I’ve begun to realize that I tend to listen more and more to smaller subwoofer/satellite systems as opposed to the larger, tower-type speakers that I’ve always associated with high quality sound. Although I’ve built many of the fantastic performing mini/small speaker designs that other folks from PE’s Tech Talk board have designed, I realized that I’ve never designed one myself, and thought it was time to give it a shot.

Design Goals:
My goal for this design was to create an extremely small speaker with reasonable bass output, as well as a nicely executed and sparkly top end. I also wanted to use one of PE’s Denovo brand pre-cut cabinets so anyone could easily build these. This design employs a Peerless 3.5″ passive radiator in lieu of a traditional vent. Using the passive radiator in this system had a few positive results. First, it allowed for a reasonably low tuning with a shallow roll-off in a box size that would have been difficult with a vent. Secondly, I was able to use the frame of the PR as a crossover mount, which simplified crossover assembly and mounting in such a tiny box. Although the passive radiator is small at 3.5″, it takes up almost all of the back of the enclosure, leaving room for only the smallest of binding post terminals.

Driver Selection:
Since I wanted this to be a miniature speaker, but also have a ‘higher end’ sound than you might normally see in this size, I went with the #290-224 Dayton Audio ND 91-4 woofer, and the #275-195 Dayton AMTPOD-4 tweeter pair — which is actually designed to be used in an automotive environment. These drivers are a bit more expensive than are normally used in micro speakers, but after listening to them for some time, I have to say that I feel the extra expense was worth it.

Enclosure Design:
Using the PE supplied Denovo .04 cubic foot knock-down boxes made assembly quick, and super-simple. They only go together one way so you can’t do it wrong, and the machining is so precise, the seams fit perfectly — even when just dry fitting the panels together. If you don’t have the tools to cut panels perfectly square, or just want to try an easier way to build a box for a change, these knock-down cabinets are top-notch. They even seem to use a nicer grade of MDF than what I can get locally.

Enclosure Assembly:
I used Titebond II wood glue and spring clamps because I had them, but you could easily use tape to hold things together until the glue dries as long as you’re not using an expanding/foaming polyurethane glue. After removing the clamps I sanded the seams until they were all flush. The boxes are wisely designed with an ever-so-slight bit of extra material right where you want it, at the seams. A few passes with medium/coarse sandpaper makes the surface flush with the adjoining panel, ready for veneer or paint.
The baffles come already rounded-over on the vertical sides. A light sanding of these round-overs with medium grit sandpaper smoothes the machine marks. I also slightly softened all the remaining edges of the baffle with medium grit sandpaper as well, since I intended to paint them black. If I were veneering the baffles, I would have chose to keep the edges sharp. I also made sure to caulk the inside seams of the cabinet with silicone caulking as I went to be sure there are no air leaks.
Machining the openings in the baffles and cabinet takes time and a bit of precision. I mounted the tweeter in a 2″ hole, 1–5/8″ down from the top of the baffle and centered left to right. The woofer hole is 3–1/8″ and is centered 2 1/8″ from the bottom of the baffle. I cut the tweeter hole with a fostner bit starting with a small 1/8″ pilot hole and drilled the finished hole from both sides to eliminate tear-out. The woofer hole and terminal relief was cut with a jig saw. Be careful with this as there is not much of a flange on the woofer to cover the opening. Mark and drill small pilot holes to mount the woofer at this time. While we’re on the subject of pilot holes, I used a center punch to locate every screw hole on this entire project, and I also made sure to use a drill bit that was as big as the shaft of the screw I intended to use.
The passive radiator opening is 3-3/4″ and is on the rear of the cabinet, with its center at 2–15/16″ down from the top and centered left to right. The PR will be in the top portion of the cabinet, which should have just the two seams for the sides visible, not the third rear seam — leave that for the bottom where nobody will see it if the seams ever show through the veneer or paint. I cut the PR opening with a jig saw. You will notice that the jig saw may dig into the sides of the cabinet slightly, that is normal… just take it slow and try and stay on the line. Mark and drill your pilot holes to mount the PR at this time.
The holes for the binding post terminal are 5/8″ from the bottom of the rear of the box and 3/4″ apart. I drilled these holes with a 3/8″ drill bit, using the leverage of the tip of the drill bit against the inside bottom of the enclosure to ‘elongate’ the hole a bit until the terminal fit in just fine with room for the quick disconnect fittings. I had to bend the terminals a bit closer to the binding post shaft to make everything fit. Mark and drill your pilot holes to mount the binding post terminal at this time. As you can see, it’s a tight fit on the back of the cabinet but if you’re careful, everything should fit just fine.
The woofer is tiny, and even in 1/2″ material there is not much breathing room through the driver frame. I used a drum sander to ‘open up’ the areas where the driver ‘breathes’ leaving the drill hole ‘spokes’ untouched so the screws would have enough ‘meat’ to bite into. I did this for the passive radiator as well, although it ‘breathes’ a bit better with no magnet and more openings in its frame. You can also use a router to do this, but I can’t always see what I’m cutting with even a small trim router and there is little room for error when working with something this small.
I chose a light colored ‘figured maple’ veneer for the sides, top and bottom of the enclosure to provide nice contrast with the black baffle I had planned on using. Since the back of the box is mostly passive radiator, I opted to just paint that black and make life easy. You could also paint the bottom of the box as well as opposed to veneering it, but I happened to have enough small pieces of veneer to do all four panels. After the box is sanded smooth, tape off the areas where you don’t want polyurethane, or whatever you choose as your finish, especially the front where the baffle will glue onto. I use Rustoleum’s wipe-on poly because it’s easy, looks good, and doesn’t smell so bad that I can’t apply it in my basement. 5-6 coats should get you a pretty nice finish.
The baffle was taped off and primed with BIN shellac base primer, sanded smooth with fine sandpaper, and painted with Rustoleum textured paint. I used four 2–1/2″ drywall screws driven slightly into the woofer screw holes to hold up the baffle as I painted it. The texture paint needs to be applied slowly in several coats, I used 5 very light coats. If you put on too much at one time, it will drip and you will need to start over so take it slowly. The first coat hardly covers up the white primer, and by the fourth or fifth you can still see some of the light color underneath. It’s a good idea to change up the direction of your spray pattern each time for a more even texture. I finished up with gloss black paint by Krylon for a nice, glossy look that will contrast nicely with the light colored cabinet. Follow the instructions on the paint you use for re-coat times.
After all finishes have had a few days to dry, it’s time for some assembly. I mounted the tweeter before attaching the baffle since it is a bit tricky to mount as it’s really designed for automotive stick-and-press usage. The best solution I found was to use a full wrap around the inside of the tweeter hole with the Parts Express speaker gasket foam tape, the 1/2″ wide variety. You may have to clean up the tweeter hole with some sandpaper first. Don’t stretch it as you apply it, but press it firmly into the baffle. If you put the baffle face down on a smooth surface, it’s easier to get the foam tape flush with the baffle. Cut the gasket tape about 7″ long so it overlaps, then trim both layers with a razor blade, then remove the tape under and over the cut, then press firm.
The tweeter will push in with some resistance and may need some twisting to get it in just right. If you’re careful and fiddle with it a bit, you can get it nearly flush with the baffle with just a bit of the tweeters curved flange showing. I admit, this process is a bit tricky to get right. My first try looked great, my second try was not as good and I actually ended up redoing it after the cabinet was assembled. It helps to lightly sand the gasket material to remove the ‘grippy’ rubber skin on the gasket so the tweeter will slide easier. Make sure the fins on the tweeter grill are horizontal when you finish. The foam gasket will have some ‘bounce’ to it, so I filled the gap between the tweeter and baffle with construction adhesive. This will ‘firm up’ the tweeter in the baffle. I shot a blob of silicone where the wire exits the tweeter as well, just in case the tweeter is not air-tight.
I glued the baffle to the box with Gorilla brand construction adhesive. I used this as opposed to glue because I allowed the black paint to ‘wrap-around’ the rear of the baffle ever so slightly so there would be no ‘unpainted’ line on that part of the speaker. The construction adhesive laid thick like caulking, but allowed for a good set up and close baffle-to-box alignment. Also, being thicker, it negated the need to seal those seams with silicone later on. Wipe any squeeze-out right away, it should come right off a polyurethaned box. Let that dry for a good 24 hours before proceeding as the adhesive is all that holds the baffle to the box.

Crossover Design:
The crossover uses 8 components, and they all fit nicely on the back of the passive radiator for convenience. I designed a second order crossover for the woofer with a response-shaping resistor in series with the coil. The tweeter filter is a third-order with two resistors for shaping and level-matching. I used hot glue and zip-ties to hold down the two inductors first and worked the rest of the components around them. With some fiddling, I was able to get everything wired point-to-point except for one ground jumper wire. The passive radiator has very good venting around it’s basket and installing the components on the basket frame did little to restrict airflow around the rear of the PR.
Knowing that placing air core inductors next to metal such as a PR frame would change their values, I tested the specs of the inductors with the DATS while mounted on the passive radiator to see if the changes in value were detrimental to the design. Though the two inductors are mounted close to each other and secured to a metal frame, I measured fairly minor changes in values… nothing that was a problem.
One note: The tweeter has no markings on the wire or driver itself to indicate what the polarity is. I assumed that the copper colored wire (as opposed to the silver colored wire) was the positive (+) lead and wired it up under that assumption. I may be wrong on that assumption, but either way, wire the copper colored line to the positive connection on the crossover as indicated in the schematic. I cut some of the wire off the tweeters built-in leads as they were longer than necessary.
The ND91 woofer is an amazing driver. It’s doing the majority of the work in this design as the crossover point lies somewhere between 6,500 and 7k Hz. It’s underhung voice coil and copper shorting ring keep distortion low, and it’s got huge excursion ability with a 25mm peak-to-peak swing to prevent damage on bass heavy passages. Looking at the passive radiator undulating massively during bass-heavy music, you start to get an idea of how a speaker this small can produce so much bass.
I was relieved as I listened to the completed speaker turning the volume up higher and higher…the tweeter didn’t sound stressed at all, even at loud volumes — and it maintains a clear presentation until the woofer finally does begin its rise in distortion and forces you to turn it down a bit.

Tips & Tricks:
I used a small 4″ x 4″ piece of denim insulation on the inside top of the cabinet. I ripped the piece of 2″ thick insulation apart to yield two approx. 1″ thick pieces, which I adhered to the inside of each cabinet with spray adhesive. I don’t know if this made much of a difference as I didn’t test its effectiveness, but hopefully it calms down any in-cabinet resonances a bit. If you left it out, however, it wouldn’t probably be an issue.
Since the speaker box is so small, there is little room for deviation on where most of the components are placed. The passive radiator and binding post terminal on the back need to be almost exactly where they are in order to fit, as well as to not have any screws being driven into the end grain of the 1/2″ thick MDF, which may cause a split in the wood. Measure carefully and dry fit/mock up the pieces before cutting anything. The notch for the woofers terminals is a good example of being very careful. It is easy to remove just a bit too much material, then you will have a gap to fill. It’s best to remove a bit at a time, then check fitment and repeat until it’s perfect.
Another tip is to make sure the tweeter and gasket are where you want them in the baffle before gluing the baffle to the box. As I said, I had to remount one tweeter after the baffles were glued to the box and it was much more difficult to do that way.
Since the woofer is so small the woofers terminals end up being very close to the driver frame, so I put a few pieces of electrical tape on the basket to guard against accidental short-outs in case the terminals get pressed into the basket when mounted.
Two things to look at when assembling the crossover; make sure the components are able to fit through the opening on the cabinet several times during assembly. Also, make sure nothing gets too close to the moving weight in the center of the passive radiator as you hot glue things together. It’s a good idea to make sure the components don’t touch the woofer magnet as well, though if you lay them out as I show in the pictures, there should be enough room. Look for this project on the ‘Speaker Project Gallery’ on PE’s ‘Tech Talk’ Forum for many more crossover assembly pictures.

Conclusion:
I think this is an exceptional sounding speaker, especially given its size. It can produce a good bit of bass thanks in part to the passive radiator, which in this design yielded an almost first order roll-off after the downward turn of the ‘knee’ on the low end. The AMT tweeter has a nice high end with a bit of sparkle to it which I really like. Many tiny speakers sound decent, but won’t play loud without distorting; the Bantams can play a fair bit louder that you would expect — and sound clean doing it. It doesn’t seem that such a big sound should be able to come from such a tiny speaker box — a testament to the quality designed into these two Dayton drivers.

About the Designer:
I’ve been dabbling in speakers since I was a teenager when I built my first set of speakers. Even as a kid I thought they sounded kind of awful… but I had been bit by the bug — and have been striving for better sound and more creative cabinet designs ever since.

Project Parts List

Designer:
Reithi

Project Category:
Subwoofers

Project Level:
Beginner

Project Time:
20+ Hours

Project Cost:
Over $1,000

Project Description:
For starters, I live in Nairobi Kenya.
I ordered two Bash 500 Plate Amplifiers way back in 2008 to add much needed low end to my home theatre system but never got to build them until now.
Some of the reasons for the delay was getting hold of 15″ subwoofers and good step down 240-110V transformers locally.
I eventually settled for Sony XS-L156P5 Subwoofers and 1000VA 230V to 55-0-55V Torodial Transformers for step down duty. The subwoofers have a Xmax of only 5.5 but figured they would sound OK with the right box.

Design Goals:
Add low end punch for music and movies to my home theater system.

Driver Selection:
Sony XS-L156P5 Subwoofer

Enclosure Design:
The box is downfiring. Net internal volume 2 cubic foot tuned to 34.66 Hz with two ports of 3″ diameter by 12.5″ long each.

Enclosure Assembly:
Glued and screwed together

Conclusion:
Sounds great. The low end can be overwhelming when watching movies. Overall, I am happy with the results.

About the Designer:
I have been building my own amplifier and speaker projects for over 30 years.
Over the years, my focus has shifted to SQ Car Audio.

Parts Used:

300-752 Bash 500S Digital Subwoofer Plate Amplifier 500W RMS

Designer:
Fiddleback Mahogany Towers

Project Category:
Tower Speakers

Project Level:
Advanced

Project Time:
20+ Hours

Project Cost:
$100 – $500

Project Description:
48″ Tower speakers with fiddleback mahogany veneer fronts and hammer black finish painted finish.

Design Goals:
Large Towers with best range.

Driver Selection:
Woofers: Dayton Audio 8″ Classic DC-200-8
Midrange: GRS 5″ sealed back
Tweeters: RT-6 Phenolic Ring
Super Tweeter: New old stock Realistic Horn tweeters

Enclosure Design:
Tower cabinets with internal supports and baffling. A 2″ port flared added to increase low end.

Crossover Design:
Home built crossovers.

Conclusion:
Project turned out better than expected.

About the Designer:
I am a life long cabinetmaker and love building speakers.

Project Parts List:

Designer:
Ammo Boom box

Project Category:
Portable Speakers

Project Level:
Beginner

Project Time:
1-8 Hours

Project Cost:
Under $100

Project Description:
portable Bluetooth

Design Goals:
reliable radio

Driver Selection:
Visaton FRS8-4 3.3″ Full-Range Speaker 4 Ohm

Conclusion:
I like it!

About the Designer:
commercial and residential audio video, radio hobbyist

Parts Used:
2×50 wondom Bluetooth board with ext board and battery pack

Designer:
Midnite Magic

Project Category:
Bookshelf Speakers

Project Level:
Intermediate

Project Time:
8-20 Hours

Project Cost:
$100 – $500

Project Description:
2way ported bookshelf speaker system

Design Goals:
To use the Dayton AMT2-4 as I had never used one before. To make a versatile bookshelf that would work well for movies, TV, and music. To be able to be used with or without a subwoofer.

Driver Selection:
Dayton AMT 2-4 tweeter (275-092) Is a very smooth and easy to work with unit. The off-axis response is very good
Faital Pro 5FE120 woofer (294-1141) is a gem, really. It is linear throughout its operating range and exhibits little cone breakup.

Enclosure Design:
I used the Denovo knockdown .23 cu ft cabinet (300-7062)
The cabinet is ported on the rear using 1.5″ pvc, 5.5″ long. For an Fb of 55Hz. F3/6/10 is 51/45/40

The drivers are centered left to right. The tweeter center is 3.25″ from the top edge (before the oak top was added). The woofer is 7.562″ from the top.

Enclosure Assembly:
The cabinets are CNC cut and even include a roundover on the baffle. There was very little sanding needed. I did use a brad nailer in the corners to hold the pieces steady as I applied the clamps. With the accuracy and fit, I was able to assemble both cabinets in about 20 minutes time.

I added corner blocks of 3/4″ BB ply to hold t-nuts for a removable baffle.

The walls are lined with 1/2″ sonic barrier and there is a handful of loose fiber fill behind the woofer.

The baffle and rear are coated in duratex. The sides in paper-backed oak veneer and the top with 1/4″ oak.

Crossover Design:
I used more parts than I normally do but not anything difficult either. The woofer is a damped 3rd order, the tweeter 4th order, both electrically. This resulted in a 4th order LR alignment at the crossover point of 3.5KHz. A single 8ohm resistor was used ahead of the tweeter circuit for level matching. I did use a 20w unit here for extra heat protection, if it was warranted or not, I’m not sure but it is cheap insurance.

Tips & Tricks:
Use a brad nailer for temporarily holding the pieces together as you apply clamps.

In testing, I used a 30uF cap in series with the tweeter for protection.

Conclusion:
These were a really fun, fast project. Using the manufacturers provided data, I was able to make a very close sim. After taking the measurements and playing around for a few days in PCD, I was able to put together the crossover. They have a very smooth response on and off-axis and handle power very well to way to loud levels. For testing I use an Adcom GFA-555 amp and had no problems driving past the halfway point on my preamp.

These now reside in my living room awaiting a matching sub for movies or when I want to play them way to loud!

About the Designer:
I am a member of the Parts Express speaker design team

Project Parts List: