I am thinking of building a hybrid ESL with dipole bass.
Since dipole bass cause huge pressure difference between front and back of the speaker, it will also move ESL diaphragm more or less. I am afraid that ESL could misbehave because of that.
How can I avoid intermodulation distortion as well as diaphragm being to close to stators in all possible case? Does anybody have any experience about that?
Since dipole bass cause huge pressure difference between front and back of the speaker, it will also move ESL diaphragm more or less. I am afraid that ESL could misbehave because of that.
How can I avoid intermodulation distortion as well as diaphragm being to close to stators in all possible case? Does anybody have any experience about that?
Hi,
You´re right. Any bass in close proximity to an ESL-Panel can blow the diaphragm into the stator. So does a dipole-bass.
R. Sanders named this phenomen acoustic coupling.
Solutions:
-move the bass farther away from the panel
-when using dipoles a ´slot ´ between Panel and woofer, used as kind of a pathway, helped
-use highest possible diaphragm tension
-use higher -but still smallest possible- d/s spacing.
jauu
Calvin
You´re right. Any bass in close proximity to an ESL-Panel can blow the diaphragm into the stator. So does a dipole-bass.
R. Sanders named this phenomen acoustic coupling.
Solutions:
-move the bass farther away from the panel
-when using dipoles a ´slot ´ between Panel and woofer, used as kind of a pathway, helped
-use highest possible diaphragm tension
-use higher -but still smallest possible- d/s spacing.
jauu
Calvin
Bill, do you mean, pushing on the midrange from the outside?
I would think that theoretically it would be possible to have this affect the sound quality. By that level of volume, it seems likely also that the eardrums are moving so much, along with the lungs and walls and windows etc. that the difference would be hardly heard....
Good point though, I think.
I would think that theoretically it would be possible to have this affect the sound quality. By that level of volume, it seems likely also that the eardrums are moving so much, along with the lungs and walls and windows etc. that the difference would be hardly heard....
Good point though, I think.
Stocker said:
Yes, that's what I meant. And this would apply to a tweeter as well.
So there is a situation of dynamically changing air pressure in front of mid relative to the rear. It would seem to me that the mid would have a more difficult time pushing against a high pressure (>15psi) than it would against a low pressure (<15psi) and that some of the T/S parameters, for example, would keep changing in response to the woofer output, notably Cms and Qms. I need to read about this acoustic coupling as noted by Sanders.
Who has some additional input?
Your question is not in vain. It is a problem. I backed into this by having my subwoofers slap the diaphragms in my Magneplanars against the screen. Having a quad-amped system, and knowing that the amp powering the woofer panels was off at the time (I was testing some changes to the subs), it was clear that the subs alone were bottoming the woofer panels.
Not just vibrating the membranes...bottoming them.
I'd say that would cause a little tiny, itsy bit of IM distortion.
The subs were three or four feet behind the woofer panels at the time. I later brought the subs forward into the room in order to cure a resonance and discovered by accident that it reduced--but did not eliminate--the problem. My subs are sealed enclosures, so all the pressure originates from the front.
I have also noticed the same thing with my midrange driver modulating my tweeter, so it's not just in the bass.
What to do about it, I don't know. But, yes, I'd say it was a problem--one that doesn't get recognition. On the other hand, perhaps everyone is mum because there's nothing that can be done so there's no point in getting worked up about it. I drag the problem out and meditate on it from time to time, but I've got too many other things on my plate to give it my full attention, so it just kinda hangs around like a bad smell in the air.
Grey
Not just vibrating the membranes...bottoming them.
I'd say that would cause a little tiny, itsy bit of IM distortion.
The subs were three or four feet behind the woofer panels at the time. I later brought the subs forward into the room in order to cure a resonance and discovered by accident that it reduced--but did not eliminate--the problem. My subs are sealed enclosures, so all the pressure originates from the front.
I have also noticed the same thing with my midrange driver modulating my tweeter, so it's not just in the bass.
What to do about it, I don't know. But, yes, I'd say it was a problem--one that doesn't get recognition. On the other hand, perhaps everyone is mum because there's nothing that can be done so there's no point in getting worked up about it. I drag the problem out and meditate on it from time to time, but I've got too many other things on my plate to give it my full attention, so it just kinda hangs around like a bad smell in the air.
Grey
Martin Logan Statement 2
The Martin Logan Statement 2 has a line source dipole ESL, a dipole line array of 6.5" Scan Speaks separated by a physical gap from the ESL panel, and a separate bipole subwoofer array that was placed far away from the panels that could have a radiation pattern aimed perpendicular to the ESL and still pressurize the room.
ML apprears to have used all of the techniques mentioned in this thread to reduce the effects of low frequency sound waves modularing the ESL panel.....physical gap to midrange line array and separate bass cabinet aimed away from the ESL.
The Martin Logan Statement 2 has a line source dipole ESL, a dipole line array of 6.5" Scan Speaks separated by a physical gap from the ESL panel, and a separate bipole subwoofer array that was placed far away from the panels that could have a radiation pattern aimed perpendicular to the ESL and still pressurize the room.
ML apprears to have used all of the techniques mentioned in this thread to reduce the effects of low frequency sound waves modularing the ESL panel.....physical gap to midrange line array and separate bass cabinet aimed away from the ESL.
Attachments
A little off-topic tough (since it is not dealing with ESL) but the mechanical stress on drivers by acoustical coupling is even relevant in the ara of tough professional equipment:
"For example, the horns attached to the driver act in both directions - not only do they transform and radiate sound from the driver to the outside world, but they also focus external sounds on to the diaphragm, adding significantly to its stresses."
Taken from:
http://www.meyersound.com/support/forums/talkshop/drivers.htm
Regards
Charles
"For example, the horns attached to the driver act in both directions - not only do they transform and radiate sound from the driver to the outside world, but they also focus external sounds on to the diaphragm, adding significantly to its stresses."
Taken from:
http://www.meyersound.com/support/forums/talkshop/drivers.htm
Regards
Charles
If a closed box sub is used with dipole you simply place the sub at 90 degrees to dipole and voila, no problem from the direct outputoif the sub.
And with multiway dipole you need a gap between each range just like ML did it with their big speaker system.
The problem also exist with coned drivers as someone was concerned with, but the cone mass and enclosed volume beind makes this much less of a problem compared to a dipole ELS membrane.
By the laws of nature the mids and tweeters thast are most sensitive to this is of course those with soft suspension, low mass and big volume of air in the box behind. The stiffer the suspension, higher the mass and smaller the volume of air in the box the less this moving system will move according to a outside pressure acting on it.
Moving coil dipole speakers are more sensitive than closed box but less so than ESL.
In the end it is actually dipoles (no matter if moving coil, ESL or magnetostats) that can be arranged to be least affected by this phenomena, simply by doing it like ML. With perfect symmetrical dipoles and air gaps between panels there will be no force acting between the panels.
/Peter
And with multiway dipole you need a gap between each range just like ML did it with their big speaker system.
The problem also exist with coned drivers as someone was concerned with, but the cone mass and enclosed volume beind makes this much less of a problem compared to a dipole ELS membrane.
By the laws of nature the mids and tweeters thast are most sensitive to this is of course those with soft suspension, low mass and big volume of air in the box behind. The stiffer the suspension, higher the mass and smaller the volume of air in the box the less this moving system will move according to a outside pressure acting on it.
Moving coil dipole speakers are more sensitive than closed box but less so than ESL.
In the end it is actually dipoles (no matter if moving coil, ESL or magnetostats) that can be arranged to be least affected by this phenomena, simply by doing it like ML. With perfect symmetrical dipoles and air gaps between panels there will be no force acting between the panels.
/Peter
Stocker said:
Yes!
And while a boxed mid/tweeter would function best at a certain frequency node where the pressure is max and speed of air is minimum, the other way is true for a dipole velocity source.
Think about how dipoles vs. monopoles excite room modes... they do not do that in the same way and at same locations... food for thought.
/Peter
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