I've always liked the ZaphAudio designs. For example, the ZMV5 should come in significantly under your budget ($125 for drivers + electronics, and then add in enclosure and bindings). He designs them around well-known and well-tested drivers, and it is easy to put those designs into pre-fab enclosures or build your own to suit. Some of his other designs look nice too, but come in above $400 after you build a box (ie, the SR71).
My experience has shown me that enclosures easily take the most time in a DIY speaker project, and determine the lion's share of how most people will evaluate them. If you are a talented woodworker or are particularly meticulous, go for it. Otherwise, if you want them to look "professional," buy the pre-fabs. Personally, I've enjoyed the process of building enclosures to make them look and feel my own, but I usually make enough little mistakes that it takes a while to converge on what I consider acceptable as a final product.
Crossovers are (in my opinion) the hardest part to design well, especially when you start understanding the subtler points like phasing and reactive impedance. These can obviously be eliminated if you go the single-driver route--a bad crossover is worse than none at all! Many crossovers eat dynamics, smear imaging, waste power, add coloration to the sound, etc. But a well-designed multi-way system will usually outperform a single driver system, and I am skeptical that anyone can build a truly good pair of single-driver speakers for under $400 within your constraints of bookshelf speakers. Using old/NOS drivers or something Chinese, or Dayton and tower configurations, maybe (but unlikely, after accounting for the cost of enclosure)...single driver systems rely heavily on the output of the one driver, and it just isn't worth cheaping out on it...so spending $150+ on each driver (Jordan JX92, etc) is not uncommon.
You can do away with the tablesaw if you are especially handy with a router (especially for bookshelf sizes). But if you have access, great. A couple good clamps are absolutely worth it because an air-tight enclosure is made like good furniture--fastened with some wood-on-wood method, glued, and clamped.
I've built huge subwoofers in less than week, with access to a shop and the space to leave my supplies all over the place while drying/curing. If you use pre-fab or pre-cut boxes, you can do it in a few hours in one day, really. Passive speakers are pretty simple to assemble after the design is done, and settling in to the right stuffing/measurement/placement values will take some time and personal preference anyway.
I suggest you DO NOT make your own drivers as a first project, and probably ever. There are good designs on the market for nearly anything you would want at this point...it would be a real challenge to best the performance of these for cheaper than the price to order online from, say, Madisound or Parts Express. You can do DIY electrostats, and that might make sense, if you want something exotic. But it will NOT be cheap to energize those huge films. I don't know enough about ribbons to comment on them.
Easiest designs that sound excellent (ie, large margins of error) are typically sealed acoustic suspension designs. As long as you can make the enclosure air-tight, you can make a winner.
I have been most impressed with open baffle designs. But not a good place to start with a first project :). They only look simple.
Good luck! I have found that DIY speakers tend to elicit a greater interest from friends/family/guests than DIY electronics because anyone can see it and understand why the design problem is interesting...great way to get friends involved in a rewarding pursuit!
Quote:
Originally Posted by
Zafsk 
Hey guys,
I'm thinking about taking on a project that seems a bit daunting but I think I can do it with a bit of help. I've been wanting to DIY a pair of bookshelf speakers for awhile now and actually get some decent quality out of them. I've been doing a lot of reading on circuit diagrams and electrical engineering, and honestly, understanding only a fraction. I found Parts Express, and that gave me a bit of a confidence boost, knowing that there was someplace I could get parts, but I'm still a bit overwhelmed on where to start. I'm willing to go all out and use kevlar and magnets to make drivers and such but I'm not sure how that would end.
So here are a couple starting questions for you guys:
1. How feasible is making a pair of DIY speakers that sound hi-fi (i.e. have a wide frequency response, dynamic enough to handle loud volumes, and has good clarity) on my own?
2. Can I do it without breaking the bank (I think that I'd probably cap around $400 for the pair)
3. What timeframe am I looking at here?
4. Tools needed?
If I could get a general idea, that'd be fantastic. I'm sure I'm looking pretty silly here, asking about DIY speakers when I don't know much about it, but I figured I'd jump in feet first.