damping factor

Leo, please explain Q factor. I don't know anything about it. Also, how does one learn what a particular speaker's Q factor is? I don't think I've ever seen that data/spec reported. Thanks

Amps with low damping factors (high output imp) will have a Hz response curve that may not be flat and IS effected and influenced by the speaker load. -i.e. - you don't know the amps Hz response curve until you hook it up and measure it with the load. In ohter words, if you change speakers, you are kind of changing amps too.- Different beast. :) This effects how loud the amp plays at different Hzs. This is one of the problems with many tube designs esp. SETS and why you need speakers with very flat Z curves.

Q is a speaker's "resonance peeking factor". There is a Q for the bare driver and another Q for the speaker box with the driver installed. This is a measure of the output db at the resonant frequency of the driver and/or box. It has nothing to do with an amp's damping factor OR the speakers impedence curve. Q is measured and used in basic calclations for designing the speaker box volume and is usefull predicted bass responce.

I'm not sure I CAN explain speaker 'q' except that it is a design choice made and involves the TS parameters of a driver....the woofer....and box size and port tuning...where needed.
Critically damped is a value of .707 (sine of 45...coincidence?) while higher numbers result in bloated.....thick or boomy bass. The typical tuning of some of the old 12" 3-way monitor speakers of old was higher and I can't think of an example of a lower 'q' speaker, though they may exist.

Somebody that knows more / better can chime in, but as near as I can tell NO high damping factor can save a speaker with hi 'q'.

The parameter in question....please read....is QTc.......

http://www.bcae1.com/spboxad2.htm

or this discussion...look to 3rd or 4th post down.

http://www.hometheaterforum.com/forum/thread/135679/what-does-qtc-mean

I don't know if this helps. My personal take-away is NOT to depend of damping factor to 'control' a woofer. Whoever wrote that any value over 20 (atmo?) is fine may be on to something. Fullrange Single Driver speakers may benefit from low damping and produce the appearance of fuller bass....but this is conjecture on my part

And Bif, you will NEVER see this number reported. 99% of even those who are in the audiophile camp wouldn't know 'Q' from a bag of beans.....While, on the other hand, the speaker builder, DIY crowd make use of it every day in the design of the bass part of their homebrew efforts.

Thanks, Elizabeth, I owe you one....my login is WAY flakey.....

Does this help or hurt?

From the wiki on damping:
Note the 'curve' for 0.7, which is critically dampened. Desireable in a loudspeaker.

http://en.wikipedia.org/wiki/File:2nd_Order_Damping_Ratios.svg

Please read the section on QTC

http://www.members.shaw.ca/loudspeakerbuilder.ca/thiele-small.html

The connection of speaker and damping factor is simple. IF a speaker system has a high QTC (Q of the Total System) than no amount of damping (electrical) will keep it from sounding a little full and maybe have bass bloom. This is worst case scenario, I hope.

On most speakers I've seen measurments for, the resonant frequency is also an impedance minima. They go together. Read the text for the B&W speaker tested by Stereophile.
http://www.stereophile.com/content/bampw-800-diamond-loudspeaker-measurements

I'm not big into damping factor. It's just my opin that any competently designed SS amp which is operated within its electrical limits will have enough damping for a compatible speaker. Some of the audible problems may be due to speaker amp mismatch or simply the design of the speaker. I just don't think a wacky high DF will fix those speakers. Also, don't forget that many of the very HIGHEST DF amps also employ lots of Negative Feedback....yet another can of worms! I won't touch this on a BET!

It may be noted as an aside that when measuring a bare woofer, a resistance can be put in series with the driver and the voltage measured and considered proportional to the drivers impedance. This using a sweep frequency signal generator / amp and not clipped. I understand there are other methods for making this measure, but this is the one many pre-computer DIY persons use.

Sorry guys, had family over last night, just picked up on the thread. Here is my attempt to explain Q in easy terms. A driver has 3 Q ratings, QMS, QES and QTS.
QMS is a drivers Quality Mechanical Speaker... It is the mechanical resistance that particular driver gives or how much mechanical loss that driver has, QES is the drivers Quality Electrical Speaker, it tells us how the driver electrically generates its strength from the magnet and voice coil assembly. These two measurements combined tell us a driver QTS (the summed total of the two) FS, the drivers resonance, QTS, a drivers summed Q and VAS, the Equivalent air volume tell us what type a box a driver needs to be in. QTC mentioned above is typically used to describe a sealed box design. It does tell us how a woofer is damped in a sealed box. .707 is a perfectly flat curve rolling off at its maximum 3db downpoint and is what we think of as being perfectly damped.
I'll leave it at that for now, if someone wants more post it in the speaker forum. Tim