What does Q mean in speaker specifications?

@mrteeves

They do that in electronics. There is a filter before the subwoofer amplifier that adjusts the bass behavior in a very similar fashion to how a woofer behaves with different sized cabinets. It’s just some basic equalizer circuitry.  Great flexibility but requires your amplifier and driver to have plenty of headroom so you don't over drive it.

They also make some speakers you can convert from sealed to ported AND have a Q control.

In all cases the idea is to give you more flexibility and help the subs adapt to different rooms and placements.

Total Q of a driver (only) is two parameters- mechanical and electromagnetic …

Dont mistake this for “total system Q” which incorporates an enclosure (and it’s volume/ port size length  (or sealed).

QMS, QES, QTS, QTC

QMS tells us how well a speaker is damped in the mechanical realm or suspension

QES tells us how well a speaker is controlled through its electro-mechanical side, magnet & voice coil

QTS is a summary of the 2 combined.... QTS helps us easily judge if a driver belongs in a sealed or vented/ported box.

QTC is the final system Q after it is in the box.  .707 is considered a perfect rolloff.  .8 to .9 will give you a warmth or small rise in the lower region, Over 1.0 can get to be sizeable rise, but not necessarily, some drivers sound reasonably good with the rise in bass.  

Below the .707, its just the opposite of being above, the lower below it is, the leaner low frequency is.  I hope this helps in some way. Tim

Do horn woofers have a Qtc?

QTC is a function of the woofer completed in the box and really designed for a sealed box. A driver in itself has a QMS/QES = QTS and yes, you would be able to measure these on a horn driver.