Hi there,
Just a question concerning excursions and SPL re ESL's vs subwoofer.
I heard this today, from someone :
"Assume nearly 1m2 (10000cm2) (Acoustat-M3, perhaps M4 or 2+2, easily) ESL panel, with (for argument sake) max. excursion of +/- 1mm (2mm total movement) (practically, this is "elevator music level" volume on ESLs),
Assume a large (12") sub (cone area ~700cm2 - 14 times smaller area than ESL)
=> For the same volume of air to be displaced, the sub cone has to move +/- 14mm (28mm total movement)
Now, assume +/- 2.5mm average ESL membrane displacement, for a very low listening volume; Total Sub cone movement of 70mm!!! (coil in the magnet gap). In order for coil/magnet flux field to maintain the required motor strength (ability to pull back the coil) the length of the pole piece would have to be ... at least 100mm?
Now, with all this in mind...if there are subs out there capable of 70mm excursion within same time it takes ESL membrane to travel 2.5mm (the "speed" is the essential requirement for different sound sources to sound at least similar, without altering the original instrument timbre to the point that a bass sounds like organ, and piano like bass...),
.. and within the financial reach of the mere mortals,
.... I'd love to know about them!"
Does any of this sound ridiculous or absurd?
Just a question concerning excursions and SPL re ESL's vs subwoofer.
I heard this today, from someone :
"Assume nearly 1m2 (10000cm2) (Acoustat-M3, perhaps M4 or 2+2, easily) ESL panel, with (for argument sake) max. excursion of +/- 1mm (2mm total movement) (practically, this is "elevator music level" volume on ESLs),
Assume a large (12") sub (cone area ~700cm2 - 14 times smaller area than ESL)
=> For the same volume of air to be displaced, the sub cone has to move +/- 14mm (28mm total movement)
Now, assume +/- 2.5mm average ESL membrane displacement, for a very low listening volume; Total Sub cone movement of 70mm!!! (coil in the magnet gap). In order for coil/magnet flux field to maintain the required motor strength (ability to pull back the coil) the length of the pole piece would have to be ... at least 100mm?
Now, with all this in mind...if there are subs out there capable of 70mm excursion within same time it takes ESL membrane to travel 2.5mm (the "speed" is the essential requirement for different sound sources to sound at least similar, without altering the original instrument timbre to the point that a bass sounds like organ, and piano like bass...),
.. and within the financial reach of the mere mortals,
.... I'd love to know about them!"
Does any of this sound ridiculous or absurd?
Interesting analysis of subwoofer requirements for matching electrostatic loudspeaker "speed"... 
I've lived for 20+ years with a pair of the original MartinLogan CLS (Curvilinear Line Source) full-range electostatic loudspeaker (MartinLogan | CLS) and the best subwoofer complement that I found was the Janis W1 + Janis Interphase crossover+power-amplifier. A large part of the reason why the Janis W1 was able to present bass frequencies with a similar sonic "speed" characteristic to that of the MartinLogan CLS was the fact that the Janis W1 was a slot-loaded woofer (see attached diagram), which magnifies the effective velocity of the woofer output by the ratio of the woofer surface area divided by the area of the subwoofer slot (see Nelson Pass's slot-loaded subwoofer project The Slot Loaded Open Baffle Project Article By Nelson Pass). Nelson Pass's slot-loaded open-baffle subwoofer design has the additional advantage of eliminating the inherent resonances of the enclosed cabinet of the Janis W1. Wicked cool work by Mr. Pass...
The Nelson Pass slot-loaded subwoofer is very amenable to DIY construction (some MDF and simple power-tools), so you could experiment with tailoring an implementation to your specific needs.
Just my $0.02's worth...
I've lived for 20+ years with a pair of the original MartinLogan CLS (Curvilinear Line Source) full-range electostatic loudspeaker (MartinLogan | CLS) and the best subwoofer complement that I found was the Janis W1 + Janis Interphase crossover+power-amplifier. A large part of the reason why the Janis W1 was able to present bass frequencies with a similar sonic "speed" characteristic to that of the MartinLogan CLS was the fact that the Janis W1 was a slot-loaded woofer (see attached diagram), which magnifies the effective velocity of the woofer output by the ratio of the woofer surface area divided by the area of the subwoofer slot (see Nelson Pass's slot-loaded subwoofer project The Slot Loaded Open Baffle Project Article By Nelson Pass). Nelson Pass's slot-loaded open-baffle subwoofer design has the additional advantage of eliminating the inherent resonances of the enclosed cabinet of the Janis W1. Wicked cool work by Mr. Pass...
The Nelson Pass slot-loaded subwoofer is very amenable to DIY construction (some MDF and simple power-tools), so you could experiment with tailoring an implementation to your specific needs.
Just my $0.02's worth...
Attachments
So you don't agree with the logic in the above? I don't understand how "speed" is an important factor for different sound sources to sound the same. I thought frequency response was a more significant metric.
As far as excursion requirements go, what are your thoughts in that post? Does the math add up? Why would a sub need to have a 70mm excursion to match 2.5mm excursion on the ESL? Does the whole ESL panel act like a subwoofer? I just don't understand what he was saying.
As far as excursion requirements go, what are your thoughts in that post? Does the math add up? Why would a sub need to have a 70mm excursion to match 2.5mm excursion on the ESL? Does the whole ESL panel act like a subwoofer? I just don't understand what he was saying.
As far as I can tell mullardel34 is probably agreeing that the speed of the air is the triggering factor for matching the sound of a sub to ESL. So if you do not have the same area in woofers it does not matter much if you can just increase the speed of the air it moves. The sensitivity will of course be lower than if you had the same area as the ESL in woofers, but how much space and money are you willing to sacrifice? And how loud do you really need to play?
Edit:
clarification
Edit2:
A 12" with 700cm2 area sounds like a bit of a stretch, I know it's not part of the discussion, but a 12" will have at most ~550cm2 area, less area the more excursion it has.
Edit:
clarification
Edit2:
A 12" with 700cm2 area sounds like a bit of a stretch, I know it's not part of the discussion, but a 12" will have at most ~550cm2 area, less area the more excursion it has.
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That looks a lot like the DeathBox from Decware. It's even 'tunable'.
I'm using one right now until my other big ones are done.
Amazing what it puts out, have been using it for some years now.
It is "fast" but SQ isn't high in my opinion. But this can be because of the low budget drivers (that I've put in isobaric configuration).
Apparently the DBII has a lot more SQ to it. (no experience with it)
I'm using one right now until my other big ones are done.
Amazing what it puts out, have been using it for some years now.
It is "fast" but SQ isn't high in my opinion. But this can be because of the low budget drivers (that I've put in isobaric configuration).
Apparently the DBII has a lot more SQ to it. (no experience with it)
Interesting analysis of subwoofer requirements for matching electrostatic loudspeaker "speed"...
I've lived for 20+ years with a pair of the original MartinLogan CLS (Curvilinear Line Source) full-range electostatic loudspeaker (MartinLogan | CLS) and the best subwoofer complement that I found was the Janis W1 + Janis Interphase crossover+power-amplifier. A large part of the reason why the Janis W1 was able to present bass frequencies with a similar sonic "speed" characteristic to that of the MartinLogan CLS was the fact that the Janis W1 was a slot-loaded woofer (see attached diagram), which magnifies the effective velocity of the woofer output by the ratio of the woofer surface area divided by the area of the subwoofer slot (see Nelson Pass's slot-loaded subwoofer project The Slot Loaded Open Baffle Project Article By Nelson Pass). Nelson Pass's slot-loaded open-baffle subwoofer design has the additional advantage of eliminating the inherent resonances of the enclosed cabinet of the Janis W1. Wicked cool work by Mr. Pass...
The Nelson Pass slot-loaded subwoofer is very amenable to DIY construction (some MDF and simple power-tools), so you could experiment with tailoring an implementation to your specific needs.
Just my $0.02's worth...
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The explanation is based on an inflated excursion of the electrostatic panel.Sorry, can someone please explain the whole SPL/excursion of ESL and subwoofer, in that example? I'm not getting it.
If the very large panel could indeed move +/- 2.5 mm, it could move a lot more air than a 12" speaker, but electrostatic panels don't have near that much Xmax, which is exactly why they can't produce low frequencies at loud levels.
Specifications on electrostatic panels are often sketchy, if "someone" can show any that have actual sound pressure levels supporting a 2.5 mm Xmax I'd love to see them.
As far as the "speed" aspect, sound waves travel at 1130 feet per second regardless of what speaker they come from.
An argument can be made about lagging group delay of a particular sub design making it sound "slow", but if a speaker can't make enough low bass to satisfy one's needs, who cares how "fast" it sounds?
weltersys said:
So you are saying that ESL's typically don't have anywhere close to 2.5mm excursion? That 70mm figure, I don't know if that is the woofer operating in free air or not. Wouldn't putting it in a box, with room gain changing the numbers considerably?
Another thing as well which I thought I would ask is the roll-off of ESL's. Is it true that dipoles have a 6 dB roll-off per octave but this eventually becomes a 12 dB drop, and it gets worse as frequencies decrease?
I'm saying that to my knowledge, even a large (one meter square) electrostatic panel could not keep up at low frequencies below about 50 Hz to a real world 12" with around 13mm displacement in a sealed box, ergo, the displacement is likely far less than 2.5 mm.
There is no replacement for displacement, whether in the form of a large diaphragm moving little or little diaphragms moving a lot, but the type of box the driver is put in makes a difference in sensitivity, that being how much sound level comes out per voltage in.
Open backed speakers are the least sensitive regarding low bass, the roll off rate is determined by baffle or membrane area. As frequencies are lowered the baffle becomes small relative to wavelength and the front and back waves cancel as they become progressively more out of phase.
My MartinLogan CLS's can easily reach 108dB SPL levels without significant distortion in my 12'x14' listening room, when combined with my Janis W1/Interphase-1A crossover/power-amplifier. The fixed 100Hz crossover frequency relieves the full-range CLS electronstatic panels from having to address large-excursion bass-frequency music reproduction. Even without the Janis subwoofer system, the "naked" MartinLogan CLS's can readily exceed 100dB SPL levels; they just roll-off pretty damned quickly below about 60Hz in my listening room...
True, the speed-of-sound is consistent in a given room, but that's not what we're talking about...
The "sonic" speed of the subwoofer is critical when attempting to assemble a full-range audio system employing single-panel electrostatic loudspeakers. Enclosure resonances in a subwoofer (which are absent in open-baffle dipole electronstatic loudspeaker) can be very quickly identified within this context; the sonic footprint of a subwoofer enclosure presents a very different ("slower") sonic characteristic from that of the electronstatic panels interfacing with the listening room. The slot-loaded Janis W1 12-inch woofer fires into a 2"x12" slot and the pressure generated flows out the front through a horizontal slot. The rear wave of the woofers is dissipated/absorbed within the enclosure.
The purpose here, as with an AMT (air-motion transformer) driver, is to have the air velocity at the output to be much faster than the velocity at the driving surface, in this case the subwoofer cone.
The motional energy imparted to the moving air is proportional to the mass of the air times the velocity squared. The "squared" part means that if you increase the velocity of the moving air by forcing the moving air through a slot that is less than the surface-area of the driver. This raises the efficiency of the speaker quite a bit, and it improves the transient response as the apparent mass of the air moved is higher in relation to the cone mass of the drivers (hence, the effective "speed" of the subwoofer rises accordingly).
The way this is accomplished is by "squeezing" the air through an opening narrower than the surface of the moving diaphragm of the driver. The air pushed by the cone has to exit out the front of the loudspeaker through a slot opening whose surface area is only about one third that of the cone driver, and so it goes out about two-to-three times faster than the velocity of the cone.
True, the speed-of-sound is consistent in a given room, but that's not what we're talking about...
The "sonic" speed of the subwoofer is critical when attempting to assemble a full-range audio system employing single-panel electrostatic loudspeakers. Enclosure resonances in a subwoofer (which are absent in open-baffle dipole electronstatic loudspeaker) can be very quickly identified within this context; the sonic footprint of a subwoofer enclosure presents a very different ("slower") sonic characteristic from that of the electronstatic panels interfacing with the listening room. The slot-loaded Janis W1 12-inch woofer fires into a 2"x12" slot and the pressure generated flows out the front through a horizontal slot. The rear wave of the woofers is dissipated/absorbed within the enclosure.
The purpose here, as with an AMT (air-motion transformer) driver, is to have the air velocity at the output to be much faster than the velocity at the driving surface, in this case the subwoofer cone.
The motional energy imparted to the moving air is proportional to the mass of the air times the velocity squared. The "squared" part means that if you increase the velocity of the moving air by forcing the moving air through a slot that is less than the surface-area of the driver. This raises the efficiency of the speaker quite a bit, and it improves the transient response as the apparent mass of the air moved is higher in relation to the cone mass of the drivers (hence, the effective "speed" of the subwoofer rises accordingly).
The way this is accomplished is by "squeezing" the air through an opening narrower than the surface of the moving diaphragm of the driver. The air pushed by the cone has to exit out the front of the loudspeaker through a slot opening whose surface area is only about one third that of the cone driver, and so it goes out about two-to-three times faster than the velocity of the cone.
[QUOTE="Wed]Open backed speakers are the least sensitive regarding low bass, the roll off rate is determined by baffle or membrane area. As frequencies are lowered the baffle becomes small relative to wavelength and the front and back waves cancel as they become progressively more out of phase.[/QUOTE]
Some people are telling me that the roll-off is less steep than a monopole, at 6 dB per octave once the wavelengths exceed the baffle size. Others claim 18 dB per octave.
I would have thought dipoles would have a steeper roll-off because of the sound waves cancellation.
Some people are telling me that the roll-off is less steep than a monopole, at 6 dB per octave once the wavelengths exceed the baffle size. Others claim 18 dB per octave.
I would have thought dipoles would have a steeper roll-off because of the sound waves cancellation.
weltersys said:
Some people are telling me that the roll-off is less steep than a monopole, at 6 dB per octave once the wavelengths exceed the baffle size. Others claim 18 dB per octave.
I would have thought dipoles would have a steeper roll-off compared to monopoles because of the sound waves cancelling beyond the baffle size.
They start rolling off a lot higher than a monopole, unless the baffle is huge. In room, I'm told they fall off at ~6dB/oct. In free space, I have no idea.
Hornresp seems to think 9dB/oct, but of course individual driver choice will come in: high Qts drivers will extend the bass out, even OB. Low Qts drivers won't. For reference, the driver I sim'd has a Qts ~0.4.
The problem with the original post is that you appear to have forgotten something important: while the electrostatic panel may well move 1mm one-way, not all of that energy is sent into the room - a lot is lost to dipole cancellation.
The actual SPL at low frequencies would be huge, if you could just avoid the dipole cancellation (I have heard of ESLs mounted IB, apparently the bass hit 20Hz easily).
The 12" woofer may radiate into the room with no cancellation, so all of its volume displacement goes into pressurising/depressurising the room.
If, say, 75% of the LF energy of a conventional electrostatic speaker is lost, the 12" driver is moving ~3.5mm one-way in a sealed cabinet. Give it a ported cabinet (or other loading technique), and excursion can be reduced further.
Chris
Hornresp seems to think 9dB/oct, but of course individual driver choice will come in: high Qts drivers will extend the bass out, even OB. Low Qts drivers won't. For reference, the driver I sim'd has a Qts ~0.4.
The problem with the original post is that you appear to have forgotten something important: while the electrostatic panel may well move 1mm one-way, not all of that energy is sent into the room - a lot is lost to dipole cancellation.
The actual SPL at low frequencies would be huge, if you could just avoid the dipole cancellation (I have heard of ESLs mounted IB, apparently the bass hit 20Hz easily).
The 12" woofer may radiate into the room with no cancellation, so all of its volume displacement goes into pressurising/depressurising the room.
If, say, 75% of the LF energy of a conventional electrostatic speaker is lost, the 12" driver is moving ~3.5mm one-way in a sealed cabinet. Give it a ported cabinet (or other loading technique), and excursion can be reduced further.
Chris
Hi,
Just had a quick overview over the thread, so
I might miss a point or two. But
I disagree with most explanations given here.
A ESL has its territory in a frequency range of >>100Hz. As soon as the diaphragm is asked to perform excursions most of the magic is gone. Below 100Hz the dynamic speaker rules.
The dynamic speaker generates more power per membrane area unit than a ESL. This is why ESLs must feature larger surface areas than dynamic speakers.
The lightweight membrane of an ESL is best used in free-air configurations. A casing is most often a bad idea for these kind of speakers. Dynamic speakers beeing heavy profit from an enclosure, which at the same beefs up bass response (increasing Qt).
If one compares an ESL to a dynamic speaker these prerequisites need to be kept in mind.
Due to acoustic phase cancellation an open baffled speaker won't generate as much power in the sub-region. It also is incapable to pressurize the room below the room's lowest mode.
The differences in drive system, power-per-area unit, room interaction and (most often) also the distribution character and amplitudr response can make a seamless integration of ESL and dynamic woofer difficult. I intentionally didn' t list speed, since speed or velocity of the moving parts don' play any significant role at the related range of frequencies. It is a fairytale told over and over again, but it is simply not the truth. It is a conclusion drawn erranously from a listening impression. Indeed do many basses and subs sound 'slow' compared to the panels, but this is due to two reasons. The first is a sharp break in distribution character and the second is non-symmetrical acoustical flanks the crossover point. While the panel exhibits typically a steep rolloff below its base resonance, the bass runs linear past this point over several octaves. Hence the acoustical filter slope may differ drastically.
If those two points are taken care of a seamless integration of bassand ESL is possible, regardless of weight differences of the moving parts.
jauu
Calvin
Just had a quick overview over the thread, so
I might miss a point or two. But
I disagree with most explanations given here.
A ESL has its territory in a frequency range of >>100Hz. As soon as the diaphragm is asked to perform excursions most of the magic is gone. Below 100Hz the dynamic speaker rules.
The dynamic speaker generates more power per membrane area unit than a ESL. This is why ESLs must feature larger surface areas than dynamic speakers.
The lightweight membrane of an ESL is best used in free-air configurations. A casing is most often a bad idea for these kind of speakers. Dynamic speakers beeing heavy profit from an enclosure, which at the same beefs up bass response (increasing Qt).
If one compares an ESL to a dynamic speaker these prerequisites need to be kept in mind.
Due to acoustic phase cancellation an open baffled speaker won't generate as much power in the sub-region. It also is incapable to pressurize the room below the room's lowest mode.
The differences in drive system, power-per-area unit, room interaction and (most often) also the distribution character and amplitudr response can make a seamless integration of ESL and dynamic woofer difficult. I intentionally didn' t list speed, since speed or velocity of the moving parts don' play any significant role at the related range of frequencies. It is a fairytale told over and over again, but it is simply not the truth. It is a conclusion drawn erranously from a listening impression. Indeed do many basses and subs sound 'slow' compared to the panels, but this is due to two reasons. The first is a sharp break in distribution character and the second is non-symmetrical acoustical flanks the crossover point. While the panel exhibits typically a steep rolloff below its base resonance, the bass runs linear past this point over several octaves. Hence the acoustical filter slope may differ drastically.
If those two points are taken care of a seamless integration of bassand ESL is possible, regardless of weight differences of the moving parts.
jauu
Calvin
Every couple years, I run my Dayton-Wrights full range. The bass is quite fine on almost any music, lacking only the last octave or so.
These speakers are sealed with a heavy welding gas and therefore the "sounding board" is a one-meter square film, front plus back. That's a lot of surface for an ESL and the gas provides a megaphone or impedance matching benefit. Seems challenging to build that way? Some owners run pairs of them.
Unless you think the gas and the enclosing are faulty concepts, it is one good way to make bass with an ESL.The sound quality is.... ummm, no special quality... like it should be. But there is a resonance around 65 Hz which sounds a bit tubby, as you'd expect; not sure if that is due to a poorly damped resonance or an inevitable perception you get when the bass resonance is on the high side. I cross over sharply around 105 Hz.
Ben
These speakers are sealed with a heavy welding gas and therefore the "sounding board" is a one-meter square film, front plus back. That's a lot of surface for an ESL and the gas provides a megaphone or impedance matching benefit. Seems challenging to build that way? Some owners run pairs of them.
Unless you think the gas and the enclosing are faulty concepts, it is one good way to make bass with an ESL.The sound quality is.... ummm, no special quality... like it should be. But there is a resonance around 65 Hz which sounds a bit tubby, as you'd expect; not sure if that is due to a poorly damped resonance or an inevitable perception you get when the bass resonance is on the high side. I cross over sharply around 105 Hz.
Ben
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I'm running Martin Logan CLX (Borbely Millenium class A driven), Raven R2 Ribbons, with 2 JL fathoms 113's - sealed box, very stiff suspensions, internal Class D amps - find them to blend very well at 56 hz with the CLX, previous subs were Dynaudio 30w 100 in sealed 4 cubic foot boxes driven by Class A Borbely. I was worried that going from the light cone class A driven Dynaudios I would not have the transient speed or detail i had. But I am pleasantly surprised the JL's are deeper, more dynamic, and blend very well - no loss of detail for all the signal processing and class D.
I have a garage full of Dayton Wright speakers and parts - i owe Ben some of them in the next few months as I rationalize what's here.
I have a garage full of Dayton Wright speakers and parts - i owe Ben some of them in the next few months as I rationalize what's here.
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The only detailed comment on the KLH9 electronstatic loudspeakers that I've ever seen was the review by J. Gordon Holt in an early Stereophile issue (KLH Model Nine loudspeaker | Stereophile.com).
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