speakers have intricate parts that might not be as easy to come by which are probably even more difficult to match. but an amp has basic parts that seem essentially easy to come by. the difficulty appears to be producing high quality amps in abundance for wholesale. but what's keeping the knowledgable person from constructing a sturdy, reliable power amplifier made from high quality parts?
this has been discussed several times and it seems like the cost of the parts and labor wouldnt be worth all the hassle...but if i had the knowledge/time/money i would just so i can say that i made my own amplifier
I would say the biggest hurtle to overcome would be to produce the PC boards. Theres a lot of info on the web about amplifier design and all the parts can be had through Digikey or Jameco etc... However making your PCBs can be challenging especially for the complexity of this caliber amp. So you would have to send your circuit diagrams to a company that can make them for you. Im in a robotics club at it costs us like $70 or so per board and these are quite a bit smaller than what would be used inside of an amplifier for car audio.
Also the parts for the power supply can get quite pricey too. Quality transformers are expensive and 4700uF and above caps are like $10 bucks a pop.
Id love to build my own amplifier someday, but i really dont know if its worth it.
you could, but it'd be expensive since you're not using a production line and buying parts en mass to recoup R&D and initial purchase and construction costs. There's a Zen home amplifier that's a good example of a home build amp used in home audio, but it's expensive as well.
you'd need to have a multi-layer PC board created for the amplifier if you go the SMT route. If you go solid state, you'll pay a lot for high end, close tolerance MilSpec components and things like high quality capacitors for the power supply, MOSFETs if it's regulated, bi-polar transistors for the output stage, and so forth. It ads up pretty fast, and that's teh main drawback when you can buy an amp just as good for less thanks to mass production. Speakers are actually easier to do yourself, since you can order all of the parts from supply houses and put them together with the right jigs and adhesives etc.. Most speakers you buy are made by one of a small hand full of speaker building houses who take orders for production, slap on the fancy cone the retail company choses (JL, Kicker, whatever) and ships masses of speakers built to order. There are very few companies who design and build their own speakers entirely in house.