Producing an impressive pair of DIY speakers that perform well beyond their price is easier than you think. Of course, hardcore DIY enthusiasts will do it the hard way - it's their hobby and it's all about putting in the most amount of effort for small improvements! But for the rest of us, there are ways to make it easier.
First, lets talk about the hard part - coming up with a crossover and driver combination. Hardcore enthusiasts will buy their own measurement equipment, invest a lot of time learning to use it all, and then go through many different crossover iterations and even go as far as measuring many different drivers before deciding which ones to use. You won't find instructions here on how to become the speaker design guru others will aspire to emulate. Instead you'll find a starting point in getting there the easy way. It's not easy to the point of being completely idiot proof, but it's easy compared to designing everything from scratch and reinventing the wheel just for fun.
What's the big deal about crossover design?
Surely it's just soldering a few bits together - a few resistors, capacitors and inductors, right? Not quite. There are many different factors to juggle and get right. Crossover design is a big part of what makes two loudspeakers using identical enclosures and drivers sound different. Some describe it as an art, others as science but you might call it a combination of both. It's certainly not something you would expect to perfect on your first project. Considering that it's more challenging than it sounds, and that the experts take many years in perfecting the art and science of crossover design, it makes a lot of sense to follow in the shoes of those who know what they are doing. At least, for a first diy speaker project.
I suggest you are best to start with a project that has a very good chance of working very well. It will be rewarding, and quite likely a good introduction to a long term satisfying hobby.
Where to find existing designs
First, I'll suggest some good quality websites which feature a range of competent designs that many have built:
Humble Homemade Hifi
This is the website of Tony Gee featuring a large range of speakers. Many of them would be sheer madness to try as a first time project.
Another popular suspect is John "Zaph" Krutke of Zaph audio. John has measured a very large collection of drivers. There's a good chance that he's already measured the any popular DIY driver you are interested in.
Troels Gravesen DIY projects
A great range of projects, many of which will appeal to those looking for less conventional designs including hybrid open baffle and efficient designs. He has even gone as far as developing his own driver!
You can also find a good selection of projects at Parts Express in their DIY project showcase. There is considerable variety in the projects, including some novel and innovating designs.
Share and learn
One of the best places to share your DIY experiences and learn is DIY audio. It features a HUGE gallery of projects in the System Pictures and Description thread. There are some inspirational projects in there. Some of them are so good they look like they were built in a factory. Some of them are that good because they were built in a factory.
If you do follow these links and build one of the projects, make sure you come back and tell me about it!