Frequency Response?

Your room will amplify bass frequency that corresponds to distance between front and back wall. If this distance is 18' then room will amplify 1150/18'/2=32Hz (where 1150 is speed of sound in ft/s and 2 is for travel forth and back to add).

Lowest bass string E=41.2Hz With 5 or 6 string basses lowest frequency is still 41.2Hz because it is only for the ease of playing (music is typically written for 4 string bass). The issue here is not only extension but quality of the bass. My new Hyperions HPS-938 don't have extension of previous speakers but have better bass - more natural string attack and decay, better dynamics, less resonances etc. Tuning of the port, in addition to better woofers, plays role. With popular mass market speakers bass extension is what sells the speaker, no matter how distorted or poorly defined it is.

Yes piano goes lower, some special pianos even down to 16Hz but I don't know how often lowest A=27.5Hz is played. Perhaps not very often but in either case I can live without it.

62bakes - One way they increase extension of the speaker is to put second woofer for the lowest bass only (higher frequencies filtered out by xover). For two way speakers it is called 2 1/2 way speaker (pretty much like adding subwoofer). I suspect that small drivers, being point source, will have more interaction with the room than large woofers where bigger percentage of the sound goes direct.

Distortion might be caused by by nonlinearity of the motor especially at max extension of the membrane. Most of drivers are designed as overhanged type where magnetic gap is narrow but coil is long extending outside of the gap. Some drivers (like in Acoustic Zen Adagio) have underhung motor meaning that gap is very wide and the whole (narrow) coil is inside of the gap. This scheme is more linear but requires drivers with very large magnets - more expensive. Some tweeters are made that way as well (to lower distortion at max power) including Morel Supreme.

Pbnaudio, We don't have exactly dry air here (Chicago) but I will settle for 1135ft/s which is speed of sound in dry air at 75degF - and this is my last offer.

Same example with new numbers: 1135/18/2=31.5Hz