Originally Posted by Bigus
and there really isn't one "best" driver, or even one "best" tweeter, midrange, woofer etc. There are only "best" options within a given budget and especially given your choice of tradeoffs briefly mentioned above.
Well yeah, but surely if we point the goal at best sound quality, then we will find a group of design compromises that are superior? Probably a set of optimal compromises along the scale of db output capacity, since you can probably get the same sound quality for cheaper if the output amount is smaller.
The same way we find that all the Formula 1 teams make cars that look similar; That happens to be the best way to go fast around a track 50-100 times with minimal fuel stops, to our current level of knowledge. Then the cheaper Formula classes represent cheaper ways to get round quick.
So, no costs barred, lets say it has to be 10" diameter. Then the optimal SQ design would maybe be (random big numbers here) 1000oz+ neodynium magnet, with a solid carbon fiber epoxy spider, coil and cone, with aluminium coil wires for weight savings. The coil would be lets say 7" diameter and 20mm coil winding depth inside a 30mm magnet gap, so its entirely inside the magnet gap up to 5mm xmax, allowing reasonably good sensitivity (with the 1000oz magnet) in spite of insane spider stiffness. As well as an even force application per watt during the stroke. Note that if you had a smaller diameter voice coil you would have that much less voice coil inside the magnet gap hence each watt would do less.
The surround would be quite large in diameter but made out of a thin carbon fiber composite, so it allows in and out movement of the cone yet preventing any other movement. The spider and surround thickness would be adjusted to be such that the insane magnet and voice coil combo has about 90db 1w/m output. Perhaps the spider would be so stiff that the resonance frequency is above the frequency area that the driver is used in, so that the weight of the cone never oscillates in tune with its natural frequency.
interesting to theorize like this. Because it appears good expensive home-grade drivers are on the track to this. Often deeper basket and magnet structure than the diameter of the driver. And often magnet size on par with 18" PA drivers that can put out 125-130db continuously. But they have voice coils like 1-2" sometimes a bit more, and often something like 10mm magnet gap and 30-50mm winding depth, making 10-20mm xmax. So there's much much less voice coil in the magnet gap, so most of each watt powers voice coil that isn't in the magnet gap, all to just get extra xmax at the cost of smaller woofer size. yes, sure, they can have stiffer woofer and have less breakup and distortion that way, but then they need weaker spider than they otherwise could have because they still need 85-90db 1w/m efficiency.
I would love to read the mind of the high SQ driver engineers.
Now, what shape would be best? I don't see much variation in that.