i would like to know if a amp whit better damping factor than other one necessarily mean better bass punch? considering that they would have the same power.
05-27-11: Elizabeth I guess guys in Bombay don't like chicks in there forums...
we do like women (I won't use "chicks" ...ahem!) in our forums Elizabeth (& those women do spell correctly too. Sorry that aspect was begging to be addressed. LOL! :-)) & they are always welcome but we'd like them to educate the public correctly on technical matters because in this particular case the subject matter is well-defined & documented & has a science-based explanation. Continuing to spread old wives tales keeps people uneducated which is never a good thing. No major beef with you - you've been on this forum for as long (& maybe longer) than I have....
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
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.
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.
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.....
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.
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
Slew rate is just as important(the amps ability to recover after a hard bass note).
I believe that you're correct - slew rate can give the buyer/user an idea of the power amp's bandwidth. What you wrote was re. transient decay (post event) but slew rate is equally important for transient attack. Thanks.
Hi Bombaywall, Of course you are correct that woofer size has nothing to do with damping factor, but not everyone on Agon knows much about it, thats why this section says "learn". I still appreciate Elizabeth giving a very non technical breakdown of terms. I try to do the same, sometimes it is nearly impossible to explain technical terms in a non technical way. Normally she comes very close to getting it right and normally conveys the correct idea, which I think is what she is after. Overall I have always felt she does a good job and I'm sure people that didn't always get the technical explanations appreciated what she had to say.
05-27-11: Elizabeth The damping factor is the 'control' the amp has of the woofer movement. When the amp has a signal that moves the woofer and then the other way, the damping factor is the control the amp has to "HOLD" on to the cone and not allow it to continue going in the first direction, instead of obeying the amp and moving in the opposite immediately that the new signal wants. (sloppy explanation but it will do...
So "IF" your speakers have a BIG, 12" or maybe even a 10" sloppy woofer, the higher damping factor amp will 'control' it better, and that big sloppy woofer will behave better, giving a more solid punch, with less overhang and less woolly sound. Where if you own a set of speakers with a single or pair of 'tight' 8" or 6" woofers, then the damping factor will not matter nearly as much, and other factors will overshadow the damping factor. Generally it is said ANY solid state amp has enough damping factor to control any modern speaker system woofers. Only if you had some old speakers with giant woofers.. And the place where damping factor may be a little too small for some speakers is in a tube amp. Although the combo of a tube amp and big efficient speakers is usually heavenly, even if the bass is a little sloppy. So all in all, you do not have to worry in any way about that particular spec called Damping factor. It is used to sell stuff, particularly amps which 'just by chance' have a particularly BIG damping factor, but it is a nearly meaningless spec.
there she goes again..............giving explanation on technical subjects she has no/little understanding!! Very similar situation to the "what is tube bias?" question posed not long ago by some other member.
Size of woofer cone has no bearing amp's ability to control woofer.
There is no speaker made that requires more than 20:1 for a damping factor, and there are speakers that prefer a damping factor of 1:10 (usually high efficiency full-range speakers). If a speaker is over-damped it will produce less bass and what bass there is will be tight and 'punchy', without much in the way of definition. When the speaker is properly damped not only will you have impact but you also get definition.
If the speaker is under-damped, many people assume that the loss of control by the amplifier is responsible for muddiness, but this is not true. What is really happening is that the amplifier has a high output impedance relative to the speaker, and is making excess distortion, which is interpreted as a loss of control.
The size of the woofer cone has absolutely no bearing on how well the amplifier will be able to damp the speaker. The idea that the cone size makes a difference is a common myth.
One other myth is the idea that the amplifier has to be able to 'stop' the speaker as well as get it started. It turns out that this issue is minor- if you look at any audio waveform, you will see that they don't require this of the amp and speaker to any great degree.
The only area where this really comes into play is 'overshoot'- the idea that the cone will move too far on transient peaks. But most cones will see a fair amount of mechanical damping coming from their own suspension on transients, and when an amplifier is reproducing a transient its damping factor will be higher than the that same amplifier's damping factor will be at rest; this is really not much of a problem!
I usually don't like talking specs, just because of issues like this... Think about how much damping factor measurements can change depending on where you measure from. What if you measure at the output, what if you measure at the speaker? How can two amps have great bass control with one having a damping factor of 50 or 100 and the other at 400 or even 1000.... For me, even though this is a very legitamate questions, its useless, you've got to plug the thing in and take a listen. By the way, Slew rate is just as important(the amps ability to recover after a hard bass note). Good Listening, Tim
Good answers above. There is an additional factor that often needs to be considered, though. Damping factor and amplifier output impedance are inversely related. Damping factor, as usually defined based on an assumed 8 ohm speaker load, equals output impedance divided into 8 ohms. To the extent that the speaker's impedance varies with frequency, that output impedance will affect tonal balance, by interacting with the speaker's impedance vs. frequency variation.
Many electrostatic speakers, for instance, have high impedances at low frequencies, which descend to low values at high frequencies. A solid state amp, having a high damping factor and negligibly small output impedance, will produce LESS bass and MORE treble into that kind of speaker, relative to a tube amp. The tube amp, having a relatively low damping factor/high output impedance, will produce MORE bass and LESS treble into that kind of speaker.
Conversely, many dynamic (cone-type) speakers have low impedances in the bass and mid-bass regions, and higher impedances in the upper mid-range and treble. Driving that kind of load, a solid state amp will provide a stronger bass response than a tube amp, and the tube amp may sound excessively bright.
As was stated, synergy with the particular speaker is key.
But, particularly in the case of very efficient drivers, there is the issue of overdamping. Too much control over the driver can lead to a bass response that is less natural and not as deep as it otherwise could be. My Aleph 30 amp was great except that it was overdamped, causing an unsatisfactory bass response. I have since gotten an Atma-sphere amp with a lower damping factor that works much better with my speakers. As always, synergy with speakers is the key.
Actually, what happens is when the amp sends a signal to the driver it energizes the voice coil and causes the cone to move. When the signal stops, the woofer cone keeps moving by inertia (the amplifier cannot stop the moving mass). This causes the voice coil to move back through the magnet inducing an emf onto the voice coil. Ideally, the amplifier is to present a short to the speaker (via zero or very very low output impedance). If the amp has a high output impedance, it presents a load to the back emf, and by adding speaker cable capacitance into the mix, it causes resonance. It is this reflected, or oscillating, voltage that "looses control" over the driver. The higher the damping factor, the lower this effect. Does it mean better bass punch? All depends how you define "better".
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