David Debertin’s Do-It-Yourself Speaker Building and Vintage Audio Page

 

Home of

Truly Inexpensive DIY Loudspeaker designs

DLDebertin@aol.com

 

 

Introduction

 

Are you looking for low-budget, two- and three-way DIY loudspeaker designs? You’ve found the place! This speaker building page is for those interested in building do-It yourself speaker projects employing drivers of moderate to very moderate cost. The typical driver cost for one of my speaker designs runs between $10 and $50 per speaker. The crossover uses around $15 in parts, sometimes less. The box is made from MDF and can be built with simple power tools, portable circular saw, saber saw, sander and drill. Boxes cost about $10-15 per speaker in MDF (Medium Density Fiberboard, readily available at places like Lowes and Home Depot), decking screws and glue, and are not beyond the capability of a very casual woodworker.

 

Computer modeling using a program called WinISD was used to develop basic box sizes for the drivers employed, using the so-called T/S parameters. Crossover design was not done on the computer, other than to use a spreadsheet program to select crossover components based on the frequencies I wanted to try crossing drivers. Beyond that, crossover designs were modified by running repeated experiments using different crossover component values and configurations, and comparing the sound with a speaker using the best previous configuration. They should not be regarded as the perfect crossover for the drivers, but they are the best sounding configuration I have been able to find so far for each speaker design. So again, if you want a highly sophisticated crossover based on a lot of computer modeling, you should check out any number of other sites.

 

There are several interesting projects outlined here that I currently enjoy. Furthermore, they are simple enough so that nearly anyone can build them. All of these are works in progress. I never regard a design as final.  I rework these designs over and over. I often end up exchanging drivers and rebuilding crossovers on a whim. I will keep the most recent design posted here, the design I believe is the best of those I have tried.  Considering the cost, each design offers excellent sound for the money. There could be a number of ways to improve on these designs, and if you want to simply treat them as starting points for a design of your own, that’s fine with me. These are not sophisticated, high-end designs with a lot of polish.

 

 

 

Background

 

I spent some time in the fall of 2003 at the Dayton Ohio DIY gathering, where I brought the recently completed “Goldwood Project” along. I spent the day listening to everything from super low-budget projects to high end semi-commercial designs. I came away from that event with some very mixed feelings about the general state of DIY speaker building.  Part of the problem is that I didn’t see any project at that event that I had any real desire to build. Here are some of the problems with the designs I auditioned there.

 

Overwhelming Highs. Of course, there was a lot of emphasis on projects that when tested using computer listening software produced as close as possible to a flat response curve. This leads to a lot of designs whereby the overall frequency balance to my ears is tilted upwards. These speakers may be what the computer finds as flat response, but to my ears they often sounded overly bright and irritatingly harsh. These are the kinds of speaker that sound realistic for ten minutes of listening. After that they are simply grating and irritating. My ears were physically hurting for two days after doing these auditions. The question I kept asking myself is how could I possibly enjoy listening to such speakers over the long term in my home. Along with this seemed to be a desire on the part of builders to not provide any high frequency level control to compensate for what are obvious differences in various rooms’ ability to absorb sound. I find this curious at best

I suggest that a variable L-pad be on every DIY speaker and that the plate on it be labeled like this.

 

Where is the Listener? To me, most of the DIY builders who brought their designs to Dayton planted the listener  among the musicians seated on the stage of a concert, not out in the audience 12 rows back, where highs are naturally rolled off a bit due to room acoustics and the ability of people and the room to absorb higher frequencies. Again, I suppose it would be fun to be seated among the musicians for a few minutes, but I am not at all certain that this is the sound we want in an ordinary listening room.

 

Room Boundaries. Most designs were made to be placed on tall stands well outward from walls and corners. Thus, room boundary effects had minimal effect on bass performance, and contributed to the overall upward tilt in the frequency balance. There were very few designs there that actually tried to take advantage of walls and ceiling to reinforce the bass performance, and then combined with the mid-and high frequency emphasis in the usual small-woofer two-way design this tends to result in irritatingly screechy and grating designs.

 

Baffle Step Compensation. In an effort to regain some low-end performance from small-woofer designs positioned well outward from walls, many builders incorporate some baffle step compensation in an effort to try to raise the apparent volume of the deep bass relative to the upper bass and lower mid range. This is accomplished typically by incorporating shunt or parallel components which also tend to reduce the overall efficiency. For many two-way designs, the overall SPL would be in the 80-82 db  1 watt one meter away from the speaker. These designs quickly become very power hungry to operate at normal volumes, and we were routinely clipping a decent 200 watts per channel amplifier during listening tests at Dayton.

 

I left the Dayton event with some strong misgivings about the current state of DIY. I had hoped to hear designs that I would be blown away by—something so superior that I would want to rush home and build. If the examples I heard were any indication, most of them were being built by men who were trying to come up with designs that sounded flat on-axis to a microphone connected to a computer program. As such, they appeared to be ideal speaker designs for middle-aged people who had already lost a good deal of their high frequency hearing, though I don’t doubt that some of the designs could well result in further hearing loss on short notice.

 

My speaker designs are not at all considered “finished” and they have been continually evolving over time as I experiment with ways to solve problems. They will probably all evolve some more as I keep running more experiments. If you want a plan that is more or less “final” perhaps you should look elsewhere than here. If what you want is a DIY design that sounds a lot like the majority of those I heard at Dayton, there is no shortage of plans posted on the Web, and you should probably look elsewhere than here.

If you believe that the route to good quality sound is by buying high-end, expensive parts, these are likely not the designs for you either.

 

Now that I have described the characteristics of builders who are not going to be happy with my designs, I can better explain where I am coming from.

 

First, I collect low-powered vintage and semi-vintage receivers and my projects are designed to work well and play to reasonably high volumes with 30-40 watts of power, and maybe as little as 20 watts. These are not projects to be played at very high volumes with high-wattage amplification, though some may be better in that regard than others.

 

Second, the designs are for real rooms with real walls and ceilings. The ceilings in my house are 8 feet high. The projects can either be positioned back against a wall or even placed in a corner. The Tower project has a rear-firing port and needs a foot or so of space to the back wall. The Goldwood project is particularly suited to situations where the speaker must be placed in a location partially hidden by room furnishings, and can be placed against a wall. The three-way project is designed to be placed on the floor.

 

The highs in all my designs are well dispersed, but don’t expect them to burn your ears. Three of the designs have high-frequency variable level controls to compensate for room differences and I am contemplating adding high and mid-range level controls to the three-way design as well.

 

Third, I enjoy listening to Pipe organ music, so the emphasis is on designs that does well at this.

 

Whenever I need inspiration for my projects I turn to the budget speaker pages in my 1970 Allied Radio catalog.

Overview of the Projects

 

The Tower Project.

 

The tower project was my first DIY project. I had some 6 ½ inch woofers I had purchased from Radio Shack that I used in some EPI speakers whose woofers had tragically lost their surrounds. They worked well in that application, but later I refoamed the original woofers and I reinstalled them. So I was stuck with this pair of woofers in boxes.  I decided to build a large ported tower about the size of the EPI speakers in internal volume (1.4 cubic ft).  I went down to home depot and had them cut me 8 inch wide strips of MDF four foot long from a single 4 x 8 sheet. I glued and screwed those together, added tops and bottoms, made them air tight except for the port, and those became the boxes.

 

 Interestingly, and not quite by accident, these towers also had the same internal volume as the project that appeared in the old Radio Shack/ David Weems “Building Speaker Enclosures” book that used an earlier version of the Radio Shack 6 ½ inch woofer along with a small Mylar dome tweeter. I tried to locate that tweeter, and discovered that Radio Shack no longer sold it, but it was an Audax Mylar dome tweeter, in the Audax numbering system known as the TW010F1. I found that at Madisound for about $5. At that point I needed a crossover. The crossover used in the Weems book (project 13) was a stock Radio Shack two-way but it was a very simple first-order design with  a 4.7 uF capacitor in series on the tweeter along with a small inductor in series on the woofer. Since this was a simple first-order design, the inductor must be small as well, and I settled on 0.33 mH. Weems specified a variable L-Pad on the tweeter and I did likewise. In essence this was the Weems project 13 built as a tower, using the most recent version of the Radio Shack 6 ½ inch woofer. I lined the boxes with ½ poly quilt batting on three sides, and put an extra heavy pad from an old pillow glued directly behind the woofer.

 

This was the original tower configuration and towers were satisfactory, but without much deep bass. Gradually I convinced myself that the enclosure volume was too large for this woofer. One of the problems of working with the late-generation Radio Shack woofers is that somehow Radio Shack never made the T/S parameters available. These have been accurately measured for previous versions, although even Weems claimed that the printed Radio Shack measurements were inconsistent with what he measured. I didn’t have the equipment (or skill) to measure the ones I have, and couldn’t find them anywhere on the Web.

 

At that point I purchased a Jensen JS 1000A powered subwoofer on ebay, and the towers in combination sounded quite nice as the sub effectively added the deep bass.

 

I then built a kit pair of Dayton/Parts Express BR-1s. I thought it might be useful to compare them with my own projects. Assembly was easy, but the speakers were power hungry, and I was not blown away by how they sounded. Somehow assembling the BR-1s was not a challenge for me nor very interesting to do, and I lost interest in listening to them as well. At that point I started on the so-called Goldwood project (see below).

 

I decided to try to find a pair of inexpensive woofers for the towers that I knew would be correct for the 1.4 cubic foot enclosure volume. I identified the $24 Vifa TC woofer, which was also available in buyout form as the $14.38 Vifa TC/Infinity woofer. The price was right and so I ordered a pair. They made a big improvement in the sound of the towers, even with the simple first order crossover.

 

Next, I reworked the tweeters. I had always felt that the Audax Mylars were beamy, and from my experience with the BR-1’s I knew that the Dayton Silk domes (275-070) were far better, so when they came on a DOTD sale at $9 each,  I ordered a pair. At that point I had the tweeters and RS woofers as spare parts. We will pick up on that in the mini-monitor project. I ran the towers with these drivers and the original simple first order crossover

 

Meanwhile, I was experimenting with a 2nd order crossover on the Goldwood project, and the first design I had come up with sounded quite nice. In that project, Out of necessity (the tweeter supposedly could not be crossed over lower than 4000 Hz, and the woofer wasn’t good beyond 3000 Hz) I had ended up choosing values that underlapped the LR crossover frequencies by 1500 Hz—4500 Hz on the tweeter and 3000 Hz on the woofer. This actually sounded way better than I thought it might.

 

So, I decided that if this general design had worked well for the Goldwoods, why not a similar design for the towers. But the Dayton tweeter could go lower than the Tweeter used in the Goldwood project, so I settled for only a 500 Hz underlap, a target 3000 Hz on the woofer and 3500 Hz on the tweeter.

 

Then I built out one of the towers with this crossover and compared it to the first-order crossover in the other. The new design was the clear winner, and that remains the design I am currently running. I have tried further variations, but have not yet come up with something I am confident is better. This woofer in a large vented tower is probably not the best choice if you want deep bass at very high volumes, but at more moderate volumes, it is excellent.

 

 

The Goldwood Project

 

I have a lengthy discussion of the Goldwood project at The Goldwood Web site with more construction details. On this page I will only highlight this as an effort to design a two-way module that can be used in a variety of configurations much like EPI did in their 101 and 201 models in the 70s. It is also similar in configuration Winslow Burhoe (who founded EPI) uses in his Direct Acoustics “Silent speakers” though that box is vented and I’m sure produces deeper bass than mine do (see the Direct Acoustics Web site at http://www.directacoustics.com/    I also wanted to try building a speaker that mounted the drivers in a floor-standing box with an angled top panel.

 

I had the 1.2 cubic foot box designed before I located the drivers. The project became an ultra-low budget design when I discovered that an inexpensive Goldwood 6 ½ inch woofer (Parts Express 290-305 @ $11.70 but on sale for around $9) was the best match I could find given the cabinet volume. At that point, I decided to pair it with an equally inexpensive Goldwood Mylar dome tweeter (PE 270-170 @ $1.95).  However, I was nearing the frequency limits of both drivers. That’s when I decided to underlap the second-order crossover frequencies as much as I did. Amazingly, it all worked.

Here is the $1.95 Tweeter and the $11.70 woofer used in the Goldwood project.

 

I greatly enjoy listening to these speakers. They have a bit more of an edge and an “in your face” quality to them than the towers do, although they are not at all harsh and tiring. Those who heard them at Dayton liked them too, once they got over the initial shock that any serious DIYer would attempt to build a speaker using these drivers. Their comments were consistent with my long-term assessment. They don’t have a lot of bass, though the design allows them to easily be slipped up against a wall and into a corner where they can even be mostly hidden by furniture or fake potted plants. Where they really shine is in mid-range clarity—they put the BR-1’s to shame. Jazz vocals are particularly nice. The highs from the Mylar dome have a bit more of an “edge” than a silk dome tweeter. I particularly like their sound on plucked acoustic instruments, female vocals and jazz music. These speakers have been moved into my den where they are going to form the core front channels for a home theater. They seem to create a very wide soundstage, but on mono TV the sound locates directly out of the TV set sitting between them. This is quite amazing, and superior to any speaker I have tried with front-mounted drivers. I haven’t tampered with this design. It has stayed as I originally put it together.

 

It would be easy to reconfigure the towers into this type of enclosure. The enclosure would need to be about 2/10th of a cubic foot larger. I would add that volume by widening the enclosure, which would then make adequate room for the Dayton silk dome, which might need to be covered with a protective grille in that configuration. I would add a 2 inch x 4 inch long port, probably to the front base of the enclosure, so they could still be shoved back against a wall. The resulting sound would likely be a bit more refined with a bit deeper bass. Whether it would be better overall I cannot guess.

 

 

The Mini Monitors

 

I hate having drivers in boxes. On completing the above projects I had the Radio Shack woofers and Audax Mylar tweeters that were originally in the towers back in boxes. I was convinced that I was right about the RS woofers being unhappy in the tower enclosure because it was too large, but these were still mystery woofers with respect to optimal box size.

 

Perhaps Radio Shack ultimately decided that their buyers were not enthusiastic about building 1.4 cubic foot ported boxes for a 6 ½ inch woofer (which was what was needed in the Weems project), and redesigned the woofer so it would fit more properly in a smaller box. What would be reasonable?  Or, were I a Radio Shack customer, what size of box would I likely build for a 6 ½ inch woofer if I knew nothing about the driver?  How about a half cubic foot? Then decided to build a box I that could easily reconfigure and change the baffle board if I changed my mind. So I built two half cubic foot boxes. I also had to build a crossover. Since the second-order Linkwitz-Riley design with a 500 Hz underlap was working well in the towers, I decided that it might work well in this design too. So the parts for this crossover and the configuration ended up being identical to that used in the tower.

 

In building out these speakers, I became convinced that the half cubic foot box, sealed was doing about as well with these woofers as could be done.  They don’t sound boomy. There is not a lot of bass, but what is there is very smooth. And the crossover to the tweeter works well. The Audax dome Mylar worked better in this design than it did in the towers. However, subsequently I decided that it would be fun to try an inexpensive Neodymium textile dome. I wanted a tweeter that would fit the existing hole and baffle board space I considered three different tweeters: 1. Tang Band 25-302S PE 264-804 ($13.96); 2. Peerless 811-435 PE 277-402 ($16.50), and 3. Audax TM025F1  PE 276-102

($15.20). On due consultation with those who had worked with these tweeters on the PE board, I finally settled on the Audax, although I think any of the options would have worked.

 

These speakers sound quite good. They are reasonably efficient and produce clean, well-dispersed highs. The difficulty is that the Radio Shack poly woofer 40-1033 is no longer being made, though there may still be a few around in store back rooms. I have not yet identified a suitable substitute woofer for this project that would work in the sealed half cubic foot box, though I don’t doubt there are some out there.

 

The Three-Way Project

 

Like some of my other projects, the three-way project has gone through several revisions. Originally, a message board friend had sent me some ten-inch woofers from 1970s from Zenith Allegros, and the original idea was to come up with a two-way design with inexpensive Piezo tweeters, letting the Allegros run free over a wide range. I constructed boxes similar to those I made for the mini monitors except approximately double the internal volume, or 1 cubic foot. This design worked, although the Allegro woofers were quite efficient, and kept overpowering the tweeters unless I added line resistance on the woofers. Further, in the box configuration I had built, male voices sounded tubby. I suspected that this was because the box was undersized.

 

I finally decided that part of the problem was that the Piezos had an inadequate mid range, and I started thinking about a three-way design. I found an inexpensive Vifa buyout Mid-range driver PE 299-488 (now $3.97) and, since I had good luck with the Mylar tweeters in the Goldwoods, I ordered a pair of those ($1.95 each)

 

Having a real mid-range driver improved the sound, but male voices still sounded tubby. So I finally decided the Allegros were going to have to go into a bigger, perhaps ported box. Interestingly, the Dayton 10 inch woofers (PE 295-315, $22.40) are near ideal in a one cubic foot sealed box, so I ordered up a pair. There were also a much better match output match to the mid and tweeter.

 

Then there was the crossover. Going into a three-way design, I expected that the most difficult part would be to get the tweeter to mesh seamlessly with the mid-range driver. As it turned out, that was not difficult. Getting the mid-range to woofer interface right was much more difficult, and I have tried many different configurations. Curt C and Dick M have both had substantial input into the mid and low frequency crossover design, with Curt providing many of the ideas for the mid pass and Dick the low pass. Technically, the low-pass in a second order design with a Zobel. I’m not at all certain the Zobel adds anything. The mid pass is a first-order design, as is the high pass. Resistors are to better match the output of the drivers. Recently I exchanged the Goldwood tweeters in favor of Audax tweeters similar to those I used on the mini-monitors that I found on sale at Parts Express for $8.04 each. They are PE 276-102.  These are a 6-ohm design, and I added a couple of ohms series resistance to better balance the output.

 

The current version of the three-way project is clearly the best of the designs I’ve built so far, but they remain something of a work in progress. They have excellent bass—far better than a small-woofer design, and can be built for similar $ to a small-woofer two-way.

 

Box Construction Notes

Tower Project

 

The boxes for both speakers are crafted from a single sheet of ¾ inch MDF,  I had Home Depot cut eight strips 8 inches wide and 4 ft long from a 4 x 8 sheet which runs about $16. There will be plenty of scrap for tops and bottoms. The towers when assembled are thus slightly deeper than they are wide. The port is located on the rear, near the base. This means that the speakers must be located a foot or so from the wall. You could do a front-firing port.  The cabinets are assembled with liquid nails and recessed 2 ½ inch long deck screws. The cabinets have small braces inside positioned so they don’t block the path to the port. I use closed cell foam instead of caulk for sealing drivers. Ace Hardware has proven a better source of items needed than the local Radio Shack. Here are some parts from ACE that come in handy

 

Ace Self Adhesive Closed cell sponge rubber weatherstrip Super Firm 1/8 inch thick x 3/8 inch wide. ACE 57625.  This is great for woofer gaskets. There is also a 1/4 inch wide version (Ace 50560) that works well for making gaskets for small dome tweeters.

Ace 16 gauge primary wire. The wire comes in red, black and blue. Great for wiring drivers and crossovers together. You can use this also to seal MDF box joints so that one side, top or bottom is removable, for making changes.

 

Wire Guard Twist-on connectors. Get a package of blue, a package of gray and a package of orange. You can assemble crossovers and set them up so they can be easily reconfigured without using any solder. You only need to think about soldering your crossover together when you have come up with your final permanent design.

 

Ace Terminal disconnects 22-18 AWG 3015393 These are the crimp-on disconnects in a good size for most tweeters and small woofers.

 

I lined the towers on three sides by hot gluing ½ thick quilt batting. I use pieces of polyfill glued on the back directly behind the woofer, while keeping the air path between the woofer back and the port clear. 

 

Box Construction Notes:

Goldwood Project

 

See the Information of the Goldwood Page.

 

Box Construction Notes:

Mini Monitor  Project

 

These are a basic unvented box of about 1/2 cubic foot internal volume made from MDF shelving, screwed and glued. The external dimensions are 13 inches high x 9 ½ inches wide x 9 ½ inches deep. I’m still experimenting with fill. Currently, I have a 2-inch thick piece of poly on the back, sides top and bottom. When I originally cut holes for the drivers, I wasn’t sure which tweeter I would ultimately use. I am now using one that has a very small faceplate. Were I to do this again, I would raise the woofer another inch so that it was closer to the tweeter and further from the floor.

 

Box Construction Notes:

Three-Way Project:

 

This is a one cubic foot version of the Mini Monitor box, with similar construction and poly fill. External dimensions are 20 inches high x 13 inches wide x 10 inches deep. Fill is similar to the mini-monitors with polyfill on the back and sides. The tweeters are offset, and the speakers are mirror image pairs.

 

Crossover Notes

 

Crossover notes:

Towers

 

A schematic of the crossover design for the towers, along with part numbers is at Crossovers . I have tried the alternative values shown in the box. Those values increase the underlap between the woofer and the tweeter. The so-called “Pepper Shaker” project posted on the PE message board used similar values. That project was loosely based on these towers, but it also used a different Pioneer Mid-tweet.

 

KenA has been modeling the crossover design I used. He claims that the 0.8 mH inductor does little to alter the rolloff beyond it’s natural acoustical rolloff,  In this regard the 1.2 mH inductor is probably going to have a bit more effect. I’ve tried both sets of values I can hear little if any difference between the two. In theory, at least, the mids should sound slightly more forward with the original values than with the alternate values. I have experimented at length with both the original values and the alternate values and I can detect very little if any difference. Feel free to experiment and see which you like the best, but I don’t think the differences will jump out a you.I set the L-pad on the tweeter about 2/3 up, but again that is a matter of personal preference.

 

Crossover notes:

Goldwood Project

 

See the Goldwood Page at at This location or The Crossover page

 

 

 

Crossover Notes:

The Mini-Monitors

 

A schematic of the crossover design for the towers, along with part numbers is at The crossover page . I

 

The Mini Monitor Crossover is a near textbook underlapped Linkwitz-Riley design which employs a variable L-Pad. I call this my “almost generic” crossover, and is basically identical to the one I used for the Towers. I had heard so many warnings from other speaker builders regarding the lack of advisability of using a crossover design that was not specific to the drivers, and I was anxious to test this contention.  The variable L-pad compensates for differences in relative outputs. It turns out that this simple second order crossover works very well in this design as well, and I would be tempted to try it in many other small-woofer two-way designs. I wouldn’t call it a “truly generic” crossover, but an almost generic design that might work in a variety of small-woofer two-way designs.

 

Crossover Notes:

The Three-Way

 

A schematic of the crossover design for the towers, along with part numbers is at The crossover page

 

The three-way crossover design is second order on the woofer with a Zobel and first order on the mid-range and tweeter.

 

Capacitors 101

 

 

An introduction to various types of Capacitors used in Loudspeaker building

Caps 101

Capacitor and Inductor Spreadsheet Calculator

 

Here is a capacitor and Inductor calculator for first and second order textbook crossovers on a spreadsheet.

LR, Butterworth 2nd order and 1st order spreadsheet calculator

Parts Lists

 

I have put the parts lists for all designs on a single spreadsheet, available here.

Speaker Parts Lists

Photo Album

 

Available here at DIY speaker photos

 

 

Vintage Photo Album

 

Available here at Vintage Gear Photos

 

New: Building a Home Theater System with a Combination of Vintage, DIY, New and Used Equipment

New: Building a Compact Subwoof using the Tang Band 5 1/4 inch Woofer

KLH Loudspeakers

Information on various models is available here at KLH Speakers

 

 

Utah Loudspeakers

Information on various models is available here at Utah Speakers

 

 

David Debertin does a loudspeaker test disk The test disk

 

 

 

 

New:David Debertin answers PJay Smith's Questions for the Speaker Gurus PJay's Questions answered

 

 

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