What matters most in speaker design?

Duke, a lot of the Klipsch Heritage speakers used to have the 3 dB point at 17.5 kHz. I assume this level helped smooth out the sound and mitigated some of the horn harshness. I noticed your speakers quote the same number under the category of system bandwidth. I think this top end is mostly a tube "limitation" and you mostly recommend tubes for your speakers don't you? Is that what you're getting at - a speaker for tubes? We're always quoted 20 to 20 as the range of human hearing. Are those last 2.5 kHz nothing but irritation? :) I always read with interest your posts about speakers and the obvious expertise. I'd like to hear a pair out here in the southeast.

I have a friend who designs speakers. I'd describe him as brillant - his dad is a department head at UVA. My friend has advanced degrees and has written at least one very thick book on signal processing.

I watched him build some speakers a few years ago. Very thick cabinet, the finest drivers, a lot of labor. I watched him work for months and months on the cabinet and later the crossover. He approached the cabinet design and x-over design from several angles eventually using some commercially available software for the x-over. He ended up with a perfectly flat frequency response and speakers that didn't sound too good.

Next he found someone with a lot of experience designing crossovers and worked with him for a few more months. They sounded better and eventually they got it to sound very good. He told me at one time he was thinking about adding some foam or rubber around the tweeter to take the edginess off the highs.

He took his speakers to a DIY show. I went as well. Basically he didn't win with the basic gist of it being the speakers weren't lively or forward enough. I didn't get it then but now I figure he'd built the kind of speakers you could actually sit down and listen to for a good, long while. They just didn't pass the "sip" test. The "sip" test is the first few minutes with the "boom and sparkle" jumping out at you.

Two important points I got out of this experience. First, all the parts he used were among the finest available and used in some very expensive speakers. But the drivers and crossover parts didn't cost much relatively speaking. Lesson 1: you pay as much or more for the design of the speakers as for the materials.
Lesson 2: A flat frequency response is no indicator of how good a speaker sounds.

Shadorne, I appreciate your posts and especially some of the links you've provided in the past. I know you're a big fan of Active speakers. Could you elaborate on the reason for that a bit more? From my perspective, how does moving the amplifier from its normal location to the speaker improve the sound?