There is no problem, if the FS of the cone don't bother you you should go with it.
But, i've experimented a 80Hz FS woofer with a Linkiwitz transform and the resonnance of the cone was slightly audible even with equalizations.
So here are 3 sims using the 12 inch driver from post 2 with the 69 hz fs.
First example is a small sealed box, internal volume = Vas, which is a quite small 32 liters. As expected this gives a very high natural f3 (blue curve). Using just 3 parametric eq filters I've shown it here ruler flat down to 10 hz (red curve). And this was without using any hpf, lpf or shelf filters (which would make the job a lot easier), just 3 parametric eq filters. Note that this is just one of many ways to eq it flat, this is probably not how I'd actually do it as it give about 40 db of boost at 10 hz. Not that I'd be using this driver at 10 hz in a sealed box anyway, this is just an example to show you can get any frequency response curve you want.
Next example is a ported box, 64 liters + port volume. This is shown without filters (blue curve), and it shows the rising response I was talking about. With a simple REQUIRED high pass and low pass filter we get a flat passband of 30 - 100 hz (red curve) IF that's what you want. if it was tuned lower that rising response would be beneficial to sum with the room gain curve to achieve a flat(ish) in room response.
Third example is a super simple single fold tapped horn. No filters applied here, none are required to get the flat(ish) passband from 30 - 100 hz.
So no, fs really doesn't matter that much. There are other issues with this driver that are far more important. But that doesn't mean it can't be used in just about any type of enclosure you want and with intelligent design and a bit of filtering you can a flat passband.
First example is a small sealed box, internal volume = Vas, which is a quite small 32 liters. As expected this gives a very high natural f3 (blue curve). Using just 3 parametric eq filters I've shown it here ruler flat down to 10 hz (red curve). And this was without using any hpf, lpf or shelf filters (which would make the job a lot easier), just 3 parametric eq filters. Note that this is just one of many ways to eq it flat, this is probably not how I'd actually do it as it give about 40 db of boost at 10 hz. Not that I'd be using this driver at 10 hz in a sealed box anyway, this is just an example to show you can get any frequency response curve you want.
Next example is a ported box, 64 liters + port volume. This is shown without filters (blue curve), and it shows the rising response I was talking about. With a simple REQUIRED high pass and low pass filter we get a flat passband of 30 - 100 hz (red curve) IF that's what you want. if it was tuned lower that rising response would be beneficial to sum with the room gain curve to achieve a flat(ish) in room response.
Third example is a super simple single fold tapped horn. No filters applied here, none are required to get the flat(ish) passband from 30 - 100 hz.
So no, fs really doesn't matter that much. There are other issues with this driver that are far more important. But that doesn't mean it can't be used in just about any type of enclosure you want and with intelligent design and a bit of filtering you can a flat passband.
An externally hosted image should be here but it was not working when we last tested it.
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It doesn't bother me at all, it simply is not a problem.
But to be clear, the only way to control this phenomena you are talking about is to not use the driver at fs at all - keep the usable passband away from fs. Is that what you are recommending? I certainly would not agree that this is necessary or even beneficial.
No, i was thinking about doping the cone to reduce the Fs.
But it would raise the QTS... the margin seems pretty low, it should work with some compromises on the alignment.
I still don't know what you are getting at with "membrane self ringing".
There is no notable cone breakup or cone resonances going on at fs.
So the only thing that can ring is the cone itself (a mass on a spring).
The only way to stop that ringing is to stiffen the spring, which will lower qts. An infinitely stiff spring will stop the resonance completely and there will be no ringing at all (and also no cone motion). Adding mass will raise qts and it will ring more, both in amplitude and for a longer time. This is what qts is, the control over the cone motion, less control (more mass with no increase in motor strength) = more ringing.
So what you are saying (as far as I can tell) is completely backwards.
Besides, for this type of alignment (tapped horn) it is very advisable to have fs well above the enclosure's low frequency knee, so the high fs is actually a VERY good thing. That (and damping) is how you get that gently rising smooth response shown in the measurement.
There is no notable cone breakup or cone resonances going on at fs.
So the only thing that can ring is the cone itself (a mass on a spring).
The only way to stop that ringing is to stiffen the spring, which will lower qts. An infinitely stiff spring will stop the resonance completely and there will be no ringing at all (and also no cone motion). Adding mass will raise qts and it will ring more, both in amplitude and for a longer time. This is what qts is, the control over the cone motion, less control (more mass with no increase in motor strength) = more ringing.
So what you are saying (as far as I can tell) is completely backwards.
Besides, for this type of alignment (tapped horn) it is very advisable to have fs well above the enclosure's low frequency knee, so the high fs is actually a VERY good thing. That (and damping) is how you get that gently rising smooth response shown in the measurement.
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At resonant frequencies, small periodic driving forces have the ability to produce large amplitude oscillations. This is because the system (loudspeaker cone material) stores vibrational energy.
https://en.wikipedia.org/wiki/Resonance
In case this is not clear, this is what the effect of differing qts values looks like. Qts values range from 0.25 to 2.
This fictional situation is a picture I made years ago, it's a driver on an infinite baffle. Nothing is changed except driver qts, everything else remains equal.
As qts rises you get more ringing. At 0.25 qts you have a very damped response, not much action at fs at all, very damped = low levels of ringing. With the qts of 2 you get massive stored energy, a huge amount of ringing and a huge bump in frequency response just above fs.
This fictional situation is a picture I made years ago, it's a driver on an infinite baffle. Nothing is changed except driver qts, everything else remains equal.
As qts rises you get more ringing. At 0.25 qts you have a very damped response, not much action at fs at all, very damped = low levels of ringing. With the qts of 2 you get massive stored energy, a huge amount of ringing and a huge bump in frequency response just above fs.
An externally hosted image should be here but it was not working when we last tested it.
This is really silly. This is the basic fundamentals of a mass on a spring.
And you can do a home test to prove it.
Put a weight on a spring and see how much it bounces (rings).
Then put a larger weight on the same spring and see how much it bounces (rings).
The larger weight is obviously going to put more energy into the system and ring (bounce) more because the spring can't control it as well.
We know exactly what's going to happen, the frequency of the bounces (fs) will go down, the amplitude (depth) of the bounces will increase and it will ring (bounce) for a longer period of time.
I'm really looking forward to see how you try to prove otherwise.
And you can do a home test to prove it.
Put a weight on a spring and see how much it bounces (rings).
Then put a larger weight on the same spring and see how much it bounces (rings).
The larger weight is obviously going to put more energy into the system and ring (bounce) more because the spring can't control it as well.
We know exactly what's going to happen, the frequency of the bounces (fs) will go down, the amplitude (depth) of the bounces will increase and it will ring (bounce) for a longer period of time.
I'm really looking forward to see how you try to prove otherwise.
That's not what I mean at all. Drivers of all different values of qts have their purpose. What is important is the total system q, which is why you can use up to 2 qts drivers on OB.
All I'm pointing out here is that adding mass to my driver won't reduce the membrane self resonance as you suggest, it will make it worse (raise qts, store more energy, ring more).
You are the one that seems to have a problem with membrane self resonance, which is just qts. And qts alone doesn't mean much as long as it combines with the enclosure (or lack of enclosure) to provide a decent system q. And even that can be modified with filters, eq, dsp, etc.
In other words, there's no problem with the 0.48 qts driver in the tapped horn shown in my measurement. it's a balanced system and it performs as expected with no problems.
All I'm pointing out here is that adding mass to my driver won't reduce the membrane self resonance as you suggest, it will make it worse (raise qts, store more energy, ring more).
You are the one that seems to have a problem with membrane self resonance, which is just qts. And qts alone doesn't mean much as long as it combines with the enclosure (or lack of enclosure) to provide a decent system q. And even that can be modified with filters, eq, dsp, etc.
In other words, there's no problem with the 0.48 qts driver in the tapped horn shown in my measurement. it's a balanced system and it performs as expected with no problems.
Ok, could you explain me what is the resonnant frequency of a loudpeaker (driver unit)?
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No thanks, you can look up the definition of fs on your own.
I already showed you how qts affects stored energy, ringing and frequency response, I'm not going to explain what fs is, how it works and how to use the t/s parameters to design a system with a balanced q. I've also shown a measurement of a decent subwoofer in which the t/s parameters were used to come up with a balanced frequency response with a low knee over an octave below fs.
In fact I've shown a lot of things here, all you've shown is the erroneous opinion that adding mass to my driver would reduce membrane self ringing. So if you want to start somewhere go back to that and prove what I've said is wrong.
I already showed you how qts affects stored energy, ringing and frequency response, I'm not going to explain what fs is, how it works and how to use the t/s parameters to design a system with a balanced q. I've also shown a measurement of a decent subwoofer in which the t/s parameters were used to come up with a balanced frequency response with a low knee over an octave below fs.
In fact I've shown a lot of things here, all you've shown is the erroneous opinion that adding mass to my driver would reduce membrane self ringing. So if you want to start somewhere go back to that and prove what I've said is wrong.
Do you not understand how drivers work? Did you miss the picture in post 19?
Maybe you should do a quick search on mass, springs and resonance and how that relates to drivers.
This is really bottom of the barrel fundamental stuff, like kindergarten level acoustic science Ben.
Just because a driver acts like a mass on a spring doesn't mean it ever has to be flabby.
Maybe you should do a quick search on mass, springs and resonance and how that relates to drivers.
This is really bottom of the barrel fundamental stuff, like kindergarten level acoustic science Ben.
Just because a driver acts like a mass on a spring doesn't mean it ever has to be flabby.
In case this isn't clear by now you can use VERY high qts drivers and have bass that sounds incredibly "tight" and not "flabby" at all if the system is designed right and the overall SYSTEM Q is within an acceptable range.
You can use drivers with qts upwards of 2 in open baffle because in that case the stored resonant energy is quite welcome as it counters the steep baffle diffraction losses below the baffle step frequency.
The high qts amounts to a heavy weight on a very weak spring. And the end result can be very good indeed.
This ridiculously high qts driver will give some of the "tightest" "non flabby" bass you have ever heard, as long as the system is designed properly.
MJK proved this beyond any shadow of doubt in his OB design papers, using very high q drivers on small baffles.
This is about holistic system design, looking at the big picture, not picking out one or two parameters and characterizing them as evil. These parameters don't mean much by themselves but every part of the whole system counts and is important. And resonances are about as close to a "free lunch" as you will ever see.
There's a lot of fear of these evil resonances going around lately. Resonances are not evil, they are a fact of life and can be very useful. Is it too much to ask that members of this forum do some actual research into the scientific aspects of these concepts instead of constantly spouting ill conceived audiophile myths?
You can use drivers with qts upwards of 2 in open baffle because in that case the stored resonant energy is quite welcome as it counters the steep baffle diffraction losses below the baffle step frequency.
The high qts amounts to a heavy weight on a very weak spring. And the end result can be very good indeed.
This ridiculously high qts driver will give some of the "tightest" "non flabby" bass you have ever heard, as long as the system is designed properly.
MJK proved this beyond any shadow of doubt in his OB design papers, using very high q drivers on small baffles.
This is about holistic system design, looking at the big picture, not picking out one or two parameters and characterizing them as evil. These parameters don't mean much by themselves but every part of the whole system counts and is important. And resonances are about as close to a "free lunch" as you will ever see.
There's a lot of fear of these evil resonances going around lately. Resonances are not evil, they are a fact of life and can be very useful. Is it too much to ask that members of this forum do some actual research into the scientific aspects of these concepts instead of constantly spouting ill conceived audiophile myths?
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In mechanical analogue terms,
Mmd = mass
Cms = spring
Rms = damper
Rather similar to a car suspension really
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