Intro to DIY Speakers

Silly as it may seem, building speakers is a lot of fun, and possibly addicting.  However, it's not an easy hobby to learn because it's not as well-documented as other hobbies or professions.  The internet has really opened things up for the DIY community, and computer tools have allowed average enthusiasts to create homespun projects that sound better than speakers costing several times that amount at a home theater or HiFi store.

Where to Start?

The best way to get started with DIY speakers is to hear or build a proven design.  There are many good ones to choose from currently.  Chances are, once you feel the immense satisfaction of building something that sounds so good with your own two hands, you'll be hooked (You'll probably also feel ashamed for spending so much money on store-bought speakers).  Here are some of the best designs for a beginner:

Dayton III (Wayne Jaeschke) - Bookshelf MTM with bass extension that seems to defy physics.  They image great, and have a fun overall sound--excellent for Rock and Acoustic music.  You'll be amazed that $175 worth of electronics will sound this good.  The best part about this design is that a very generous person wrote a fairly detailed walkthrough on how to build them.

TriTrix (Curt Campbell) - MTM design that can be adapted for anything from a small bookshelf to floorstanding cabinets.  Amazingly low parts count means they are easy to wire (and debug in case of problems), and will only cost about $150 in electronics for a pair.  They make a great home theater.  Curt also did a TM version of the TriTrix which pack a ridiculous amount of value for the buck!

Modula MT (Jon Marsh) - Bookshelf TM with a well-balanced, highly detailed sound.  Good for every taste in music and home theater.  It uses some mad science in the crossover--don't even ask me to explain it.  However, many, many people have built them, so don't be intimidated.  These will cost around $250 in electronics.

Cryolite and Ruby (Lou Coraggio) - These are relatively small TM bookshelf designs that pair up the highly-detailed-yet-hard-to-tame Dayton RS woofers with very good tweeters.  All of Lou's designs show a good blend of practicality, musicality, and approachability.  You really can't go wrong with any of them.

Microbe (Roman Bednarek) - A small TM design.  Works wonderfully for home theater or computer speakers.  Cheap to build, yet surprisingly high performance.  I've never heard a bad word said about them!

Dayton 8 (Wayne Jaeschke) - Large MTM towers.  If a bookshelf design just isn't going to cut it for you, and you really want to rattle the rafters, this is the design you've been looking for.  They will cost around $200 in parts and they will rock like you've never heard.  Throw away your sub.

Natalie P (Jon Marsh) - Large bookshelf MTM.  These will give you a bit more punch than the Modula MT, but still employ a lot of the same spaghetti crossover design Jon Marsh is famous for.  These will cost around $300, but will definitely satisfy most any refined taste.  Many people tend to pair these up with a sub.

RS 150 MTM (CJD) - CJD described these to me as "An RS version of the Dayton III."  They pump out a surprising amount of bass, but are otherwise very neutral.  The only difficulty a beginner may have with these is that it requires knowledge of how to translate a crossover diagram into physical parts.

Bargain Aluminum MTM (John "Zaph" Krutke) - Proves that when you pair up low-distortion, easy-to-work-with drivers, you can get great results without too many crossover parts.  Has a neutral sound that should suit most listening tastes.

Overnight Sensation, Orient Express, China Syndrome - All designs use drivers that are pretty good for the money, paired up with a crossover meant to get the most performance from the drivers.  Plus, they all come in at $100 or less for the drivers and crossover component parts!

Note: Just because these are "beginner" projects does not mean you will sacrifice anything in terms of sound quality.  In fact, should you continue with the hobby and design your own, it will probably be a long time before you build something that rivals any of these designs!

Next Step

Okay, so now you have all the weird quirks of building a speaker under your belt (and yes, there are a bunch).  What comes next?  

• You can build a more complicated [proven] design, such as a 3-way, or a 2-way using higher quality drivers.  Leaf through my links section and do some investigation of your own to find designs you might want to try
• You can experiment with designing your own speakers using some of the excellent freeware available such as Jeff Bagby's Passive Crossover Designer and Speaker Workshop.  You'll also need some sort of box-response modeling program: Unibox and WinISD Pro Alpha are both fantastic and free.  There are commercial software packages for speaker design, but honestly the free stuff I mentioned above is as good--if not better--than many of the retail loudspeaker design programs.  Save your money.
  
• I know I'm not the first to say it, and I definitely won't be the last, but you really owe it to yourself to purchase and read Ray Alden's Speakerbuilding 201 and Vance Dickason's Loudspeaker Design Cook Book.  I can almost guarantee that these books will overwhelm you at first, and the amount of math and engineering involved will be intimidating, not to mention the fact that they are full of graphs and tables using units you've probably never heard of.  The information will not sink in upon first read.  Rather, you have to try out some of the things in the book to hear them for yourself.  Then, as you go back and re-read the book, things will actually start to make sense.  I promise.  
• Don't get hung up on theoretical problems.  Just go ahead and try some stuff out.  There aren't many things more annoying to me in the DIY world than guys who pontificate about all sorts of theoretical projects, and issues related to musical reproduction--but never actually build anything!  For God's sake, go make some sawdust, hook up some drivers, find out what happens.  As Andy G would say, "The best way to learn is to do."
  

Mastered that?

If you have the guts, and are willing to deal with some trial and error, and a bunch of tweaking, it's time to build your own designs, and bring them to DIY events.  Anyway, since you're now answering to no one but yourself, it's time to be creative and original; you can use any drivers and build any kind of box (or non-box) you want!

The final frontier of DIY speakers

Unless your design wins a DIY event, it probably won't get much notice unless you do some measuring.  Measuring can be a total PITA, and requires a bit of an investment in a measurement mic ($50+) and a mic preamp ($60+), and an SPL meter ($50).  You can usually use your computer's built-in sound card, but it often requires a bit of skill in wielding a soldering iron and making your own cables. 

Then there's the measurement software....  Of the software I have tried, I have actually managed to get some results using these:

• Speaker Workshop - This will require you either build some custom cables or a testing jig.  But everything is thoroughly documented, so don't get scared yet.  The problem is that the software is extremely complex and not very intuitive.  It also requires a lot of calibration each time, the steps of which are easy to forget.  On the plus side, this software package can do pretty much everything from soup to nuts, and costs nothing.
•  ARTA - This is a shareware program, and it will perform a lot of tasks, it just won't let you save unless you pay.  In my opinion, the documentation for this program is pretty lousy; however, if you know what you're doing and you have the patience to fiddle with it, it can perform most of the same tasks that the uber-expensive measurement packages can do.
  
• Praxis - This is a commercial piece of software, however the free demo version is pretty useful, and can do a lot of handy tasks (you cannot save your files, though).  It is designed around "modules" that you can run to perform operations; the modules are very well-documented and easy to understand.  You'll still have to build some [simple] custom cables, unless you buy the retail version, in which case you get all the measurement equipment you need. 
• JustMLS - This software is not free at all.  It comes bundled with the design program LSPCad.  It's meant to be as simple and straightforward as possible.  Once you slug your way through the confusing English-as-a-second-language manual, it really is extremely easy to use and very reliable.   

"But how do I measure?" is the question on so many intermediate speaker designer's lips.  So far, I haven't found a decent set of instructions on the internet on how to measure loudspeakers that wasn't either confusing, or contained too much, or not enough information.  However, there is an excellent book written by Joe D'Appolito titled Measuring Loudspeakers, which really fills you in on everything you needed to know on measurement, and also contains all sorts of interesting asides about speaker design.  It does require a decent understanding of loudspeaker design, though--that is, you've read and understood Ray Alden's Speakerbuilding 201 and/or Vance Dickason's Loudspeaker Design Cook Book.