What does Q mean in speaker specifications?

@davidc1 

Questions like this are usually best asked at DIYaudio, but I think this refers to the Qtc.  Q is unfortunately an overloaded term in speaker and filter design.

The charts here will probably help.

@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.

To be a little clear:

Qtc is a driver parameter.  You read it when shopping for a driver.

Total system Q is how a driver performs in a specific cabinet.  You adjust this when using a cabinet simulator.

@yogiboy 

Yeah, it's pretty unusual.  They may be talking to the professionals who use these as near field studio monitors.  They want to let them know these are less punchy and more suitable for certain types of use.

PS - There are other Q’s in speaker design and measurements so don't get them confused but I'm pretty sure this is what is meant here.

In designing the alignment of the lowest frequency driver a great deal of artistic license must be allowed given the tradeoffs of speaker size, maximum bass output and expected placement.

A speaker designed for near-wall or desktop placement in general wants a lower Q.

I wouldn’t worry too much about it. In general in this case, Q refers to the "bass alignment" and how the bass rolls off. A high q ( > 0.7) causes a bump at the bottom followed by a faster drop. A low Q ( < 0.7) causes the bass to roll off more slowly but without the hump.  A lot of smaller speakers use bump at the bottom to make them sound better. 

A Q of 0.7 is often referred to as optimally flat.  The bass alignment of a driver in a sealed enclosure is related to the size of the cabinet.  Smaller cabinet = higher Q.  Larger cabinet = lower Q. 

In a speaker like this though an optimally flat speaker may make it more easily to integrate with a sub at the -3 dB since it wont’ have a bump to minimize.

Truthfully, these are pretty technical terms which are great for designing a speaker but won’t matter much in room as the proximity to walls and floors will change the bass behavior a great deal.  In particular, don't try to get a perfect measuring speaker.  You want one that sounds great in the location you are planning for it.  While a Q of 0.7 may be maximally flat in an anechoic chamber it may also sound like it lacks bass in your room.