Basically all of them.. Especially since everyone here runs 1.5-2k to most of their wooofers. Power compression is a ***** and the extra weight of the coil is more than offset by the extra coil in the gap creating more motor force. There is NOTHING magic about a 3inch coil. We could all go down to 2inch coils for better effeciency if smaller coils were really better.. They aren't, they make for lesser BL numbers all things equal and in the long term handle significantly less power.
3inch coils can be built to handle large amounts of power, but the tradeoffs they general make to do so arent' always acceptable. That's why most "big boy" 3inch coiled woofers sound like crap. Much easier to make a musical 3k handling subwoofer using a 4inch coil than a 3inch coil.
My current subwoofer uses a 6inch voicecoil.. Bl^re value of well over 300, so significantly stronger than any 3inch coiled woofer outside of a DDZ or something of that nature that sounds like crap and does nothing but burp and it's 96db/1w/1m at 1000hz (and yes it WILL play that high if you wanted it too)
Even companies like DD are moving to 4inch coils for their daily applications at the highest level, look at the 9900 series, IIRC, it's a 4inch coil.
The ONLY reason many big subs use 3inch coils is because with the proper treatements to the motor, (most of which make the woofer sound like **** for music) you can give a 3inch coil enough power for 3 seconds to run the suspension into xmax near tuning without frying the coil.. Once you hit that point, there is no point in using a bigger heavier coil. You just need very powerful magnet to make up for the lack of coil area compared to a 4inch coil, and a thick 3inch coil. Most companies top end line are comp oriented, or at least they mostly care how loud the woofer is below 60hz than anything else, so that's a perfectly fine application.. Doesn't make it ideal for daily though.
