I have more than a little sympathy for DIY loudspeaker builders, because that is how I got my start. I think I was about 10 when I built my first speaker with some scrap plywood and a 5-1/4″ driver that my brother gave me. How time flies…
The hobby itself can be quite seductive, especially if you have some woodworking skill. It seems like it’s a pretty straight-forward matter to build a box, buy some drivers, mount them along with a crossover or something, and then have a system that looks great and costs less than the commercial equivalent. However, once you start you will realize that good speaker design is actually a very complex affair. It only seems easy because of the relatively few parts that are involved. But I will let you discover all that for yourself–it’s part of the fun. If you do decide to go down the DIY path, you will do yourself a favor to have modest expectations at the start, and be prepared to get sucked into something that can take over your life if you let it.
Here are a few resources I recommend for the DIYer. Most of these will be known to experienced builders, but if you are new to the area you may not know all of them.
Drivers and other parts
Madisound Speaker Components is one of the best sources of drivers and other parts (capacitors, inductors, etc.) for both the DIYer and for small manufacturers. They have consistently been my first choice for supplying Biro’s own needs. Their service is top-notch, personal, and has never let me down.
Parts Express is another good source of drivers and parts. Professional service and good parts selection. It may be a small thing, but their selection of cabinet ports is quite good.
If you don’t like the idea of making lots of sawdust, Parts Express’ finished cabinets are really hard to beat. I have used these for some prototype projects, and the workmanship and finishes that I have seen have been really good. Madisound has a similar line of cabinets. While I expect that they are of similar quality, I have not actually seen any of these so I cannot say so with any certainty. (Madisound also sells a line of cabinets made by Woodstyle in California that some people really like, but the link shows nothing at the moment. I don’t know if that means they have been discontinued or if it’s just a bug in the website.)
If you are looking for information to help you decide what driver to use in your next project, Zapf Audio has a wealth of information to help you. John “Zaph” Krutke’s attention to detail in his measurement and methodology is admirable, as is his enthusiasm for sharing his findings. In addition to driver measurements, John has published a number of complete designs at his site. I have not heard any of them; however, they appear to have been thoughtfully and competently designed. While I don’t agree with the prioritization of all his evaluation criteria (perhaps the subject of a later post), I do have a ton of respect for his opinions, and they have enhanced my outlook. I have never met or exchanged email with John; in spite of this I feel comfortable saying that he is one of the few voices that are really worth listening to in the DIY speaker hobby realm.
You will need design software. And not just for cabinet design. You can’t really build a good system without software to help you with measurement and crossover design. While everyone seems to have their favorite in this area, I think LspCAD from IJData is just fine.
If you want good results, you must measure the performance of the drivers you have chosen in the cabinets that you will use them in. Because of the varying diffraction effects from different cabinets, you cannot use the measurements from some other source in your design. And you should never trust manufacturer data. Sometimes published curves are from preproduction prototypes, sometimes they are outright lies, and very rarely is enough information given about test conditions to let you extract useful information.
To measure your drivers you will need a microphone with a very flat and/or calibrated frequency response. Some DIYers build their own using Panasonic omnidirectional electret elements–some of which are incredibly flat. The only problem with this approach is that while the flattest of the Panasonic omni elements are quite flat, when all is said and done you may still be left with as much as 3dB error in the audio band. In my opinion, that’s not good enough. A few people make and sell complete mics using these elements and provide you with calibration data as well. This is the approach I recommend. The ones made by Kim Girardin at Wadenhome Sound are very good and very affordable. I’ve known Kim for several years as a result of our association with the Upper Midwest Chapter of the AES. He has real enthusiasm for the field and is one of the nicest people you are likely to encounter in the audio world. You may be able to plug one of Kim’s mics directly into the Mic input of your computer soundcard, but for the best results you will want a preamp with a controlled polarizing voltage. If this is the case, the Mitey-Mic II (or MM2) is a classic.
Most mics based on the Panasonic elements have simple two-conductor outputs and are meant to be interfaced to soundcard “mic” inputs or something like the Mitey-Mic II. If you want an instrumentation mic with a more conventional balanced output (and using +48V phantom power), the Behringer ECM8000 looks interesting. I have never seen one of these in real life, so it may actually be utterly poopy. But the specs and price look decent.
While the soundcards in desktop PCs are usually good enough for making usable speaker measurements, laptop soundcards tend to, er, suck. I have been using Behringer’s tiny and cheap UCA202 USB soundcard with my laptop when I need to make measurements with it, and the results have been just fine. It uses decent 16-bit TI/Burr-Brown converters, and the headphone output is particularly useful for making impedance measurements and is the main reason I use it rather than similar USB devices. (Look here for some test results.) Don’t mess around with the packaged ASIO driver–just plug it into your WinXP machine and let it use WinXP’s built-in USB audio drivers. If you absolutely, positively have to have ASIO with this guy, I recommend ASIO4ALL.
I regret that I don’t have time to respond directly to DIY questions. If I don’t reply to your inquiries or address your question here, please don’t be offended. With this post I really just wanted to offer what little support to hobbyists that I can. And as time allows, I will try to post other tips and suggestions.