A good voltage source amp usually have low enough output impedance. But passive crossover components does not help here, but this is another story.
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Qms is only suggestive of how damped the cone is, but cone material and damping are very important to the overall sound and frequency response.
It seems like underdamped is considered trendy nowadays. In theory an underdamped cone with the same FR as an overdamped one will have more micro detail.
The problem is that usually underdamped cones are more resonant and so some of the "life" is coming from a bumps in the frequency response and early break up. Also it depends on the quality of the recording.
Full rangers are usually thought to be underdamped by design but then some are different and some have lowish qms.
Something like this would effective at damping a cone in small amounts Flex Seal Liquid Rubber in a Can, 16-oz, White - - Amazon.com
Just stumbled over this thread. Should have found this earlier!
Yes, Qms is one of the Thiele/Small (TS) parameters that are used to describe the resonant behaviour of a driver. There is nothing very special about Qms that would set it apart from the other TS parameters used in the (linear!) TS driver model.
My view on Qms is that it is useful to look at non-linear behaviour of real-world drivers (not TS models!). Mechanical losses have a strong tendency for non-linearity. At low cone excursion, the suspension and other moving parts tend to "stick", where as at high excursion they "slip" more easily. I guess I am trying to say that there is a transition from static friction (stiction) to dynamic friction, which is not exactly breaking news. Since static friction is much higher than dynamic friction, mechanical losses depend strongly on the cone excursion. Small signals tend to get lost in stiction at low cone excursion ("loss of detail"). This is not the case at high cone excursion, where dynamic friction prevails. One way to reduce these mechanical non-linearities is to minimize mechanical losses in the driver. This is why I tend to prefer drivers with high Qms.
Yes, Qms is one of the Thiele/Small (TS) parameters that are used to describe the resonant behaviour of a driver. There is nothing very special about Qms that would set it apart from the other TS parameters used in the (linear!) TS driver model.
My view on Qms is that it is useful to look at non-linear behaviour of real-world drivers (not TS models!). Mechanical losses have a strong tendency for non-linearity. At low cone excursion, the suspension and other moving parts tend to "stick", where as at high excursion they "slip" more easily. I guess I am trying to say that there is a transition from static friction (stiction) to dynamic friction, which is not exactly breaking news. Since static friction is much higher than dynamic friction, mechanical losses depend strongly on the cone excursion. Small signals tend to get lost in stiction at low cone excursion ("loss of detail"). This is not the case at high cone excursion, where dynamic friction prevails. One way to reduce these mechanical non-linearities is to minimize mechanical losses in the driver. This is why I tend to prefer drivers with high Qms.
Some cone materials might have a volume compressing effect where louder sounds are dulled a bit by friction and this is very good for reducing fatigue. Dynamic friction is better I suppose, but Qms really doesn't tell us much about what the cone does higher up in frequency.
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Qms relates not only the cone but the whole driver (motor+cone+suspension). For example if one driver have aluminium voice coil former, this driver usually have lower Qms and higher mechanical resistance than a driver which have electrically non-conducting former material.
So it is electrically related, but mechanically manifested.
Cone resonance Q is usually problem at higher frequencies like break-up or so. But Qms is more relevant on the lower end of the drivers frequency spectrum as this is a T/S parameter.
MY VIEWPOINT ALSO
I elaborated at length on this point in this other thread:
Considerations for good performance at low volume
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The question remains wheter a rule that definitely and unquestionable applies to all sorts of bearings and thing that are dragged around does also apply to topologies that are bent and stretched. OK - maybe partly. But then it does still depend on where the low Qms is coming from. If it is caused elecrically (voice--coil former) then it should contribute much less to low-level non-linearity.
If the high Qms rule is correct, then my Beymas must be real champs with a Qms over 20 (on paper though).
Regards
Charles
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Yes your Beymas looks really good at this parameter.
For the easier imagination here is an extreme example of the importance of Qms.
We see that extreme high Qms drivers with low Qes are exist and they're works pretty well. Now just imagine the opposite, a driver with very low Qms but with a really high Qes. Such a driver has so many mechanical resistances (low Qms) that it can hardly move, and it is also blessed with a very weak motor (high Qes) which is not helping here either.
I do not think I have to explain the outcome.
So if the Qes is the more dominant the better the driver because your music is converted to electricity at the moment of recording.
...which is exactly what I said in the Beyond the Ariel thread, too:
"Electrical damping = (BL)^2/(Re*Mms) = 2*Pi*(Fs/Qes) is always much more than mechanical damping = Rms/Mms = 2*Pi*(Fs/Qms).
BUT even so, all else being equal and for the same amount of total damping (Fs/Qts = Fs/Qes+Fs/Qms), wouldn't you always prefer a driver for which the share of total damping provided by the electric "motor" (i.e., (BL)^2/Re) is maximised and the share of damping provided by the much less ideal and more compromised mechanical resistance (Rms) is minimized?"
I noticed that some of the newer peerless drivers and wavecor have very high qms. As a ratio to qes the mechanical damping is very low on these drivers and this is no accident.
Ok so lets say all things equal then less mechanical interference (drag friction etc) is better. Most would say that makes sense. But all things aren't equal because a cone with little or no damping will start to ring and not have as large of a usable bandwidth.
But also softer cone materials with more give can sound more pleasing to the ear. Its almost like a capacitive effect where the sound is released less quickly and muffled a bit. This isn't necessarily a bad thing to reduce fatigue. A lot of factors come into play like room, listening volume, recording etc.
I get what you say, but check a metal cone Seas driver, these have low Qms but at the top of its freq response have a homongous high Q resonant peak and it does not matter how low is the Qms, this resonant is there.
Then check the low end response, their Qts is relative low but not because of low Qes but because of low Qms and it imitates a strong motor but its fake.
I get what you say, but check a metal cone Seas driver, these have low Qms but at the top of its freq response have a homongous high Q resonant peak and it does not matter how low is the Qms, this resonant is there.
Then check the low end response, their Qts is relative low but not because of low Qes but because of low Qms and it imitates a strong motor but its fake.
But regardless of this, some Seas driver have a strong motor, mainly with 4 layer voice coil.
That "rule" is certainly not an irrefutable axiom -- it's just a rule of tumb. However, the transition between static and dynamic friction does happen within the suspension materials. And yes, the part of Qms related to electrical losses in the voice coil former is a different story, although I am not sure if these are linear due to the "turbulent" nature of the eddy currents.
P.S.: I don't trust the Beyma datasheets. I have found that some are rather inconsistent with the published impedance curves.
I think those particular cones are damped to push that break up higher up. It would be worse with less damping. Tweeters are usually well damped also.
I get what you say, but check a metal cone Seas driver, these have low Qms but at the top of its freq response have a homongous high Q resonant peak and it does not matter how low is the Qms, this resonant is there.
I think you can generalize that dynamics are influenced by the QMS. It is called transient response.
High QMS is great however the trade-off is less micro detail.
High QMS is great however the trade-off is less micro detail.
The problem is not within specs, it is in not understanding what to make of them.
If there was any truth to low Qms being something bad, the Dynaudio line of legendary tweeters (Esotar, Esotec, D28/2 etc...) would never have sounded as great as they did, and still do! Their speciality has always been in revealing the finest details in a recording.
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Qms is an artifical construction that Novack/Teile/Small came up with to make it easier to develop box alignments. Be careful trying to apply it to real world properties.
dave
dave