I believe that Qms and Qes are irrelevant in normal (voltage driven, reasonably thick and short cable/negligible series resistance) applications, only Qts matters. However, some others may believe that Qms should be low to indicate good mechanical damping and say that it makes things sound better 
Woofer low freqency design is based on Qts, which is the combination of Qes and Qms. There are an infinite number of combinations of Qes and Qms that will give you the same Qts. High Qms happens when non-conductive formers are used. and it is an inverse measure of losses in the suspension. High Qms means low losses and low Qms means high losses...
The only effect on bass frequencies according to modelling is that drivers with higher Qms have higher Impedance peaks - which does not matter for solid state amps and matters only some for tube amps......
Contrary to what others have said, I believe the golden eared crowd tend to favor High Qms drivers because they have less damping and they believe they sound more dynamic. I think that because high enders are the ones more likely to use tube amps nowadays, they are hearing the FR bumps caused by their amps' high output impedance, and they like it.
The only effect on bass frequencies according to modelling is that drivers with higher Qms have higher Impedance peaks - which does not matter for solid state amps and matters only some for tube amps......
Contrary to what others have said, I believe the golden eared crowd tend to favor High Qms drivers because they have less damping and they believe they sound more dynamic. I think that because high enders are the ones more likely to use tube amps nowadays, they are hearing the FR bumps caused by their amps' high output impedance, and they like it.
For what it's worth, I have heard a number of respected speaker designers state that they prefer high QMS designs with low QES. They theorise that there is more dampening occuring within the suspension.
A high BL factor is also a consideration.
Listening to a driver is the final determining factor as figures can only tell you so much (but they are a good starting point).
A high BL factor is also a consideration.
Listening to a driver is the final determining factor as figures can only tell you so much (but they are a good starting point).
madinoz said:
Qms is related to the dampening in the suspension. A High Qms means low damping in the suspension relative to the mass.
Qes is related to the dampening in the motor system - which is related to Bl/Re. High Bl factor in itself means absolutely nothing at all.
Do a search for Joachim Gerhard of Audio Physik.
http://www.speakerbuilding.com/content/1039/
He is the only "well respected designer" that I know of that has spoken out about this parameter that I know of - and he makes comments that completely contradict what you say regarding the amount of damping in the suspension. He also makes comments that contradict himself. Q is a measure of energy stored divided by energy dissipated, meaning that higher Q means more energy storage
"Dissipated energy" is loss.
Well i used to think that there was no possible way for there to be a sound difference-but perhaps this is true.Im no golden ear!
Klippel.de article
Klippel.de article
Variance of t/s parameters with excursion
The total loss factor QTS considering all system resistances and the resonance frequency fS are important parameters for the final alignment of the loudspeaker system. Both parameters vary with the displacement if the motor and the suspension are nonlinear.
The instantaneous value fS(x) is proportional to the square root of stiffness KMS(x). Operating the driver A,B, C, D, F and G at xmax where Cmin=25% the resonance frequency is shifted one octave higher then at the rest position x=0.
An increase of the resonance frequency fs also leads to a higher mechanical loss factor QMS and has also an effect on the total loss factor QTS. However, the electrical damping usually dominates and variations of QTS(x) can be neglected if the motor is sufficiently linear.
Contrary, the electrical damping of the system will vanish with the squared force factor variation. For example, if the force factor variation goes down to Bmin= 25% the electrical loss factor QES(xmax) increases by factor 16 and the remaining mechanical damping will determine the total QTS. Operating driver F at xmax the total QTS is 10-times higher than at the rest position giving more acoustic output at fs. However, the generation of a distinct resonance peak and the shift of the resonance frequency by one octave are usually perceived as a spectral coloration of the sound (booming bass).
Klippel.de article
Klippel.de article
Variance of t/s parameters with excursion
The total loss factor QTS considering all system resistances and the resonance frequency fS are important parameters for the final alignment of the loudspeaker system. Both parameters vary with the displacement if the motor and the suspension are nonlinear.
The instantaneous value fS(x) is proportional to the square root of stiffness KMS(x). Operating the driver A,B, C, D, F and G at xmax where Cmin=25% the resonance frequency is shifted one octave higher then at the rest position x=0.
An increase of the resonance frequency fs also leads to a higher mechanical loss factor QMS and has also an effect on the total loss factor QTS. However, the electrical damping usually dominates and variations of QTS(x) can be neglected if the motor is sufficiently linear.
Contrary, the electrical damping of the system will vanish with the squared force factor variation. For example, if the force factor variation goes down to Bmin= 25% the electrical loss factor QES(xmax) increases by factor 16 and the remaining mechanical damping will determine the total QTS. Operating driver F at xmax the total QTS is 10-times higher than at the rest position giving more acoustic output at fs. However, the generation of a distinct resonance peak and the shift of the resonance frequency by one octave are usually perceived as a spectral coloration of the sound (booming bass).
Well i posted all that rubbish,because it seems to say that at high excursions Qms can become dominant-because the Vc is not being controlled by the Magnetic circuit (low bl state)
Cheers!
Contrary, the electrical damping of the system will vanish with the squared force factor variation. For example, if the force factor variation goes down to Bmin= 25% the electrical loss factor QES(xmax) increases by factor 16 and the remaining mechanical damping will determine the total QTS. Operating driver F at xmax the total QTS is 10-times higher than at the rest position giving more acoustic output at fs. However, the generation of a distinct resonance peak and the shift of the resonance frequency by one octave are usually perceived as a spectral coloration of the sound (booming bass).
Cheers!
Contrary, the electrical damping of the system will vanish with the squared force factor variation. For example, if the force factor variation goes down to Bmin= 25% the electrical loss factor QES(xmax) increases by factor 16 and the remaining mechanical damping will determine the total QTS. Operating driver F at xmax the total QTS is 10-times higher than at the rest position giving more acoustic output at fs. However, the generation of a distinct resonance peak and the shift of the resonance frequency by one octave are usually perceived as a spectral coloration of the sound (booming bass).
mike.e said:
Dumax rates Xmag at 71% Bl, and at that point they claim there is about 10% Harmonic distortion due to that nonlinearity. So by the time you are moving far enough to get to the 25% Bl point, I would say that Qms is the least of your worries.
I was really just poking you to see if you understood what you had posted.
Maybe we should all be buying woofers with a Qms of 0.2 so that when we factor in the doubling of Fs at high excursions and the neglectible contribution of Qes we get a reasonable Qts for our speaker design....
Madinoz- I agree with you. The sound is what matters. Whats important is the sound.
Also whats important,is to have listening experience of a very accurate system,to be a rule to compare others to.
What most of us here try to do,is find mathematical or physical reasons why a high Qms driver could sound better or worse-and if no reason is found,to continue with the idea that it probably doesnt.
Also whats important,is to have listening experience of a very accurate system,to be a rule to compare others to.
What most of us here try to do,is find mathematical or physical reasons why a high Qms driver could sound better or worse-and if no reason is found,to continue with the idea that it probably doesnt.
Since I have a limited knowledge of physics (i.e an emperical understanding), then it would be pretty pointless for me to get involved in an in-depth expose on QMS, or any other technical aspect of loudspeakers.
Even people with a technical understanding still form pre-suppositions and then attempt to gather data to back up their opinions. They just sound a lot more convincing.
Even people with a technical understanding still form pre-suppositions and then attempt to gather data to back up their opinions. They just sound a lot more convincing.
Spec sheet I saw lists it at around 15. Still pretty high. IME, high Qms in a midrange means a stiff cone (as well as suspension). That means lots of backwave reflections, requiring stuffing, which lowers the effective Qms.
What interests me is the higher power handling than a typical 5" (on par with 6" and some 8"). Of course, you always want more. You can do 1.5, now keep going guys, gimme a 5" with a 2" VC.....
BTW - love your avatar. Skip you, reverse it back to me, draw four, it's red, uno, and I'm out....
What interests me is the higher power handling than a typical 5" (on par with 6" and some 8"). Of course, you always want more. You can do 1.5, now keep going guys, gimme a 5" with a 2" VC.....
BTW - love your avatar. Skip you, reverse it back to me, draw four, it's red, uno, and I'm out....
Hi,
One arguement used goes something this :
Low Qms drivers have inevitably high losses in the suspension
and /or surround, the cone typically doesn't come into it at all.
High losses allow the possibility of hysteresis in the response.
Low losses (high Qms) reduces the effect of any hysteresis.
Hysteresis is assumed to be not a good thing in a driver.
rgds, sreten.
just noticed this thread is under subwoofers.
two from ciare
pw396 qms 24,73
pw455 qms 26,06 with effiency 5.22%
PW396 : Ciare
PW455 : Ciare
two from ciare
pw396 qms 24,73
pw455 qms 26,06 with effiency 5.22%
PW396 : Ciare
PW455 : Ciare
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Interesting.
I'd argue that Qms is fairly irrelevant in quantifying the performance of a driver. The Q-factors are only measured at Fs, where the cone is acting as a piston, resonating as a mass on a spring.
At that frequency, Qes dominates for >90% of drivers.
At any other frequency, all bets are off - we have no idea if the suspension/surround will have any frequency-dependent effects. The only data we're given describes behaviour at one frequency, and any inferences made about the performance at frequencies above resonance must be based on assumptions. As we know, assumptions are the mother of all mess-ups.
More important, IMO, would be distortion curves - bell-mode resonances and how they're damped are fairly obvious.
Chris
I guess I come at this question very differently, like the way you think intuitively about car and motorcycle suspensions.
Sure, you can weight down a cone to lower its resonance and that would have consequences for the mechanical Q... which you could then try to address electrically. But isn't that a dumb way to design?
It's the Corvette (heavy) versus Lotus (light) argument. It's a matter of reducing unsprung weight in your suspension by having in-board brakes.
Ben
Sure, you can weight down a cone to lower its resonance and that would have consequences for the mechanical Q... which you could then try to address electrically. But isn't that a dumb way to design?
It's the Corvette (heavy) versus Lotus (light) argument. It's a matter of reducing unsprung weight in your suspension by having in-board brakes.
Ben
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