I have been building speakers for over 40 years. Another miss-conception is that they are cheap. Not so. Markup on drivers and crossover parts is as brutal as finished speakers and one needs to figure I go through a couple prototype boxes before I am happy and usually several sets of drivers. I prototype the crossovers with cheap parts before I risk buying big air-cores and poly caps. Then, you think you can match those Chinese piano finish cabinets? I can but it takes me weeks and materials for a couple bookshelves can run several hundred.
If you look at the direct sale companies, Buchard, Emotiva, Taylor, Ohm etc, you will see about half price compared to the traditional distribution network. It is actually hard for a DIY to match them in overall value and a disaster if you include your time.
FWIW, I lean to paper cones and silk domes. Seas, SB, Vifa etc. Above 4K, I have never heard a tweeter beat an XT-25. Unfortunately, that leaves a problem getting from a 6 inch to the tweeter, so I am working on one now using an SB.
The GR kits may be pretty fair. Danny can at least get the simple frequency response decent which is far above 90% of the speakers in the store! The CSS kits and even the spec design from ASR would seem to be reasonable. SEAS and SB have spec designs. All could be built if not getting crazy with exotic woods for under $1500 a pair. Do consider if the same materials were bought by a big company, they may be only $150. If I get lazy, I really like the CSS tweeter, but the ASR spec uses the Purify woofer which is in a class by itself. I prefer one of the SB tweeters over the DTX though. I wish Transducer Labs was still around.
Fortunately for my bank account, the couple of times I thought about a commercial line, events saved me. Closed I got was a series of three and I had two stores and a distributor seriously looking.
Why so few off the shelf drivers in commercial speakers? Well, preventing copy-cat rip-offs is one, and then we engineers always think we know better than transducer engineers who have been doing it for decades. Sometimes for good reason to make a woofer fit a box size and price point set by marketing. Sometimes just for our ego.
In-house manufacturing is reserved for ultra high volume ( cost control, supply chain management, rapid prototyping like Dynaudio) or for the uber high end prestige market where you are trying to justify the price. Even there, you will find they don't make all the pieces. As far as quality control, if you can't control the quality of your supplier, it is your fault. I say that from the years I spent in Failure Analysis as a Quality Engineer. Even I knew how to prevent Chinese bait and switch runs.
Eric, a super smooth $50 clean tweeter is not that easy to find though they are out there. If you have any recommendations, I am all ears. But yea, if you want to produce insane levels then follow the hints from the late Dr. Geedes and use compression drivers in horns and JBL PA midranges. Personally, a 1 inch soft dome can exceed the level of hearing damage in my living room so I have no need.
Now the patents have run out, I keep hoping for AMT's with distortion levels that I can handle. They do so much well, but gasp, not there yet. Elac, Golden Ear, Martin Logan. ARRG! RAAL and other similar ribbons? Just as bad. I get the airiness and that is great, but just can't handle the distortion.
Hidden cost factor: For what my woodshop cost, I could have bought top end Wilsons! Same with the misconception you can build furniture cheaper than you can buy it.
