One of the best ways to save some money on your stereo system and still get the best sound is to make your own speakers. There are many directions to go; multiway (using more than one driver per speaker) or single driver, and then there are the cabinet designs: open baffle, ported, horn loaded, sealed, and transmission line are the most common types. Because of the overwhelming number of directions a speaker build can go, it's important to start with a budget, and then take into consideration your listening requirements. Listen to hip-hop and host parties? Ported with some big woofers (low frequency driver) is the way to go. Like classical at softer listening levels? Probably open baffle with a single full range driver. Small listening space? Keep the drivers and cabinet on the smaller size. No 18 inch woofers for you. Since the design of the speaker is entirely in your hands, it's possible to tailor it to your needs.

For my build, I gave myself a budget of 250 dollars for the pair. This seems extremely low compared to the price of store bought speakers, but it really isn't too limiting because of the extreme markups on commercial speakers. For my design, I chose to go a single full range driver in a MLTL, which stands for mass loaded transmission line. The basis of transmission line theory will be covered later. This design was chosen because of the simplicity of the build, lower cost, and the better soundstage, low distortion, and fidelity that a full range design offers. With this design goal in mind, the WiBAQ was born. It stands for Wild Burro Audio Quarter wave. Wild Burro Audio is the manufacturer of the driver I used, and it's a quarter wave transmission line speaker. The name is a play on the TaBaQ design by Bjohannesen on the diyaudio.com website, who helped with the modeling of the speaker and who's TaBaQ the WiBAQ is base on.

Step 1: The Design

So, the WiBAQ. The official WiBAQ thread is here. But the original inspiration is in a different thread, linked to on the WiBAQ thread. The speaker utilizes a Wild Burro Audio Labs Betsy K full range driver, which is available through Wild Burro Audio for 110 dollars a pair. For their performance, these drivers are some of the best value on the market. The driver is mounted in a mass loaded transmission line enclosure. This means that the port at the bottom adds resistance to the air moving in and out of the cabinet, which is being pushed/pulled by the driver. This effectively increases the size of the cabinet. This is similar to how a standard ported speaker works. But in a transmission line, the length of the "line" or "pipe" behind the speaker is one quarter of the tuning frequency. Here, the mass loading of the port and height of the speaker together tune the enclosure to 35 Hz. This gives the enclosure an f3, (or a 3db cut off, or the point where the volume at that frequency has decreased just enough to be noticable) of 35 Hz, which is actually pretty low, especially with a speaker of this design.
Pictured is a Google Sketchup model of the speaker. The dimensions given are the inside dimensions. Its the insides that are the important ones, since its the inside ones that dictate the tuning of the enclosure. The external cutting dimensions of the enclosure will be given later in the Instructable. 

The first PDF is the original design with the driver mounted 15" from the closed end. This was later changed to 9" from the closed end and the new frequency response chart included in the second PDF. All the information in the first PDF still applies when the driver is 9" from the top except for the frequency response. In these PDFs you can see the ruler flat bass response, with no peaks or humps, as well as the high 95db sensitivity
<p>I made these last fall, using your instructions. I am very happy having made them, and feel the overall product is very positive. Although, i would like them to become a little less &quot;forward&quot;. This may well be my initial setup/combo of amplifier, DAC and source, but nevertheless; i want to ask if it is possible to change the values of the BSC filter to adjust the different levels of bass, mid and treble? In my case, i would start with the midrange, i feel it has too much 'gain' compared to the top and bottom end.<br>Looking forward to your comment on this ?</p>
<p>If I build these I will power them with a McIntosh MA6100 (70w per channel at 8 or 4 ohms) Is that too much power? Do I run a risk of blowing the speakers?</p>
<p>I've been researching horn type transmission line speakers and was considering the Spawn Family design with a Fostex driver, but after reviewing your build this looks much easier with a smaller profile cabinet. What did you use for your stuffing material? I'm curious if the foam egg crate material placed on the interior cabinet sides may have the same affect. Also, where did you get the parts BSC circuit? Parts Express or Radio Shack? I'm slowly learning how this stuff works so getting the correct nomenclature for parts can be tricky. Would an elctronics shop understand what I'm looking for if I took them your schematic? </p><p>I have studied Martin King's quarter wave website and the translation on the Frugal Horns website, but it still gives me a bit of the Homer Simpson deer in the headlights clueless stare. You did a good job of simplifying the explanation of both sites. Did you use King's software to design these by chance?</p><p>I plan on driving these with a Dynaco SCA-35. The 95 db/watt at 1 meter rating and seeing you only drive them with about 10w is encouraging. Plus our musical tastes appear to be similar. Thanks for the information. </p>
I have played with designing some new speakers with Martins calculators, and while I didn't design this one with it, someone else had. If you click on the link I provided to diyaudio.com, which brings you to the WIBAQ thread, you will see it was simulated by someone else, which was very helpful because I was new to this then. (I would still consider myself a newbie) All the components are from parts express. Don't bother with ratshack, unless you need something now and there is one on the corner of your block. <br><br>The frugal horn and other horn-loaded fostex projects are a cool place to start, since they are so simple and you end up with something you would never find for sale in a store. You can't go wrong with any of them.
And about the stuffing material: you want to actually have the fiber fill, because the quarter wavelength tuning relies on how the sound travels slower through the filling. So the eggcrate foam would work for a port loaded speaker or similar, but the fiberfill is important here.
Awesome tutorial!, thanks for sharing!
Hi Joe. <br> <br>I have been following your build on diyaudio, and I am extremely impressed. A great job well done. Just need to order my Betsy's and wait for them to ship to New Zealand ? <br> <br>Voted as my favourite. <br> <br>Tim
Thanks for the positive feedback and the vote. Hopefully Wild Burro Audio has their Betsy Ks back in stock. I'm also reasonably confident they will ship to New Zealand, as I think they do ship internationally.
I love your speaker cabinet build. I had joined so many audiophilia forum and asked around even show them my plans. Few has given me a good thumbs up and a lot of people asked me if I knew anything about real audio building :/ Most of them pointed me to very expensive books to &quot;research&quot; Few has given me site to read through. I am still new to the whole &quot;technical&quot; about audio but they all seem to tell me to look for driver that have thiele small parameters. Issue is I have a set of driver I would really love to use but i don't have much information. Just basic information including that the driver work in enclosed box. I would love to get some insights I just want to make a cabinet for my small room I am tired of this small satellite I have all over the place.
Well the research is very important. I researched and played around with speaker designs for about a year before I finalized the design and chose the WiBAQ. A good website is http://www.quarter-wave.com for any transmission line or open baffle designs. Also, diyaudio.com is a good place to do research. Being educated before you start asking questions makes the process a whole lot easier, as people as more willing to help if you have obviously put in some effort on your own. <br>Now about those drivers- its reaaaalllly hard to design a speaker without thiele-small parameters. To make a properly tuned enclosure like the WiBAQ requires the use of those numbers. They can be measured on your own if you have the proper equipment, but thats often more expensive than buying new drivers. What information do you have on your drivers?
Cool. <br> <br>My Fraiser Super Capsules (35 years old) were destroyed by SuperStorm Sandy. <br> <br>I will build these. <br> <br>What about adding tweeters? Too much complexity?
Sad to hear you were hit hard by Sandy. hope all is well.<br>You could certainly add tweeters. But that unfortunately takes away from the simplicity and low cost. You could figure an extra 60 to 100 bucks for tweeters and crossovers for both speakers. <br>I was thinking about adding a woofer or subwoofer at the beginning but it really doesn't need it now that I have listened to the final product. It's amazing what a quality full range driver can do.
Hmmmm. It still would be in the price range of affordability. <br><br>My Fraisers used a horn and piezo tweeter in addition to the 8 inch(?) woofer. <br><br>Has tweeter technology changed a lot? What type of tweeter/cross over would you suggest?<br><br>Thank you!
BTW, we are fine. My family is safe and healthy. Insurance will replace the other stuff.
Good to hear. I would recommend a silk dome tweeter for a good pairing to the full range driver. A first order crossover is cheaper and easier, but means more frequencies are shared between the FR and tweeter. Second or third order would be better but more expensive. Also, a separate tweeter would require zobel netwrok and SPL leveling to match the FR. That's a lot of design work and tuning.
I was just doing some reading- if you want to have a two way speaker, adding an 8 inch woofer might be an interesting way to go. The full range might have to be attenuated to match the woofer, but the advantage of a full range over a separate tweeter is the phase matching of the high frequencies and near zero comb effect. This provides what many feel is a cleaner and smoother sound.
Thank you, Joe. <br> <br>To design the cross over and so forth is above my pay grade. I will stick with your design. <br> <br>I never realized one speaker could handle full range. Looking forward to building these.
I just had my uncle, who is a devout audiophile, gave them a glowing review. He listened to them for a solid two hours playing various artists, but mostly XTC. He was astonished at the detail and clarity, as well as the stereo imaging. <br> <br>I personally had my doubts about an 8 inch driver being able to produce good highs, but it can and then some.
Cool. Can't wait to build these.<br><br>What are the power requirements and ohms? I have an old Dynaco amp and a Dynaco PAS-5(?) tube pre-amp.<br><br>The amp only has 75 watts per channel. Is this sufficient?<br><br>Thanks for the follow-up.
That's more than sufficient. These have 95 db/watt at 1 meter. So very loud at one watt up close. At any one time I probably use 10 watts MAX listening to music. And that's when I'm being stupid with the volume knob.
Nice work!

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Bio: Why fix it if it ain't broken? Because it's fun.
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