"Can't Do 3D Like Other Technologies". Fair Criticism of Horn Speakers?

morricab

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This is great Brad. It explains a lot for me especially in terms of experiences both with my Maggies and also the Pureaudio project Trio horns both as dipoles.

Getting the reflected sound in just the right timing in delay, coherently and just in the right balance with the direct sound is the thing for me that snaps both these speakers into sounding more real and alive.

The Maggie 20.7s when dialled into the room just right are 3D imaging machines.

My work with the Trio OB horns has been to get them to do everything in similar competencies to the best aspects of the Maggies with the big added advantages of their effortless dynamic natural horn nature for fine texture and then to scale up big and fast as well as the invaluable (to me) capacity for SET to drive.

With the new larger horns I’m under way on now I’m now thinking when I get in the Radian beryllium CD and Seos waveguide I will then also be able to try using the Pap iwata with the Beyma CD for rear firing duties as well.

I’ll likely be able to crossover at the same point as the Radian Seos front horn and just use an L-pad to set the right balance level with the rear horn. Getting perhaps a bit ahead of myself but now that seems to me very much worth exploring as well.

Super excited to try this out, very big thanks guys for bringing this all to light.


I am actually thinking, what if I simply take the back cover off of the compression driver? As you probably know, these drivers are essentially inverted domes with the concave part coupling to the horn throat and the convex side of the dome firing into a damped back plate. Just removing that plate would expose the convex (dome) side of the diaphragm and would act as a natural dipole. Why bother with another driver when you already have a dipole handy?

Now, what the Carolus was doing was another driver wired in phase with the front one, which makes a bipolar response. This is not how panel speakers or open baffle speakers work as the back wave is out of phase with the front one, making it a dipole. Which is more correct for creating a sense of space? I am not sure but would be worth the while to experiment and what easier way than just to take the back cover off your compression driver. You could do it with the PAPs right away. With my Odeons it is not possible but with my other system, where the horn sits exposed, I don't see why not to try it.

It shouldn't impact the driver as I think the system doesn't rely on pressure in that chamber for anything. I think the diaphragm is wholly controlled by the very powerful magnets used and the compression chamber is on the other side of the diaphragm.

Maybe someone can correct me if I am wrong about this.
 

DaveC

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For myself I would agree that the feeling of acoustic space, of being present in the original venue is one of the most highly enjoyable aspect of reproduced music. I've gotten it best from using a divider plate to minimize crosstalk. Totally blew my mind on some recordings, and always makes me sad because it's a difficult arrangement to live with but nothing else does it quite so well, including analog and digital electronic crosstalk minimizing methods I've tried so far. It works for me especially well on live event recordings, and some electronic ambient music, which can leave me gobsmacked with sonic impressions I didn't know I was even capable of perceiving. Interestingly it doesn't seem to require extremely high end equipment, and makes me think that crosstalk is an inherent weak link that seriously limits stereo reproduction regardless of the level of equipment or the acoustic qualities of the room, at least for some of us. I know some people report hearing nothing compelling from crosstalk elimination. Perhaps their brains can filter it out adequately that they are already hearing all the spacial effects available.

I forgot to post the new Polk speaker, this has active crosstalk elimination. It DOES work! I do think you can get a similar result with a setup where the speakers are placed wider than usual with more toe-in, especially with a more directional speaker. However, a big advantage of the Polks with the crosstalk elimination is you have more flexibility on placement, they can be placed closer together than normal and still project a massive soundstage. In many situations this is a significant advantage!

 
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Duke LeJeune

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I am actually thinking, what if I simply take the back cover off of the compression driver? As you probably know, these drivers are essentially inverted domes with the concave part coupling to the horn throat and the convex side of the dome firing into a damped back plate. Just removing that plate would expose the convex (dome) side of the diaphragm and would act as a natural dipole. Why bother with another driver when you already have a dipole handy?

It shouldn't impact the driver as I think the system doesn't rely on pressure in that chamber for anything. I think the diaphragm is wholly controlled by the very powerful magnets used and the compression chamber is on the other side of the diaphragm.

As long as the voice coil assembly doesn't come out when you remove the back cover, it should work.

Danny Ritchie (GR Research) and Clayton Shaw (Spatial Audio) have both done this in high-end dipole speakers. Just don't bump the unprotected diaphragm! Clayton had a protective grille made .

Now, what the Carolus was doing was another driver wired in phase with the front one, which makes a bipolar response. This is not how panel speakers or open baffle speakers work as the back wave is out of phase with the front one, making it a dipole. Which is more correct for creating a sense of space?

I don't think either one is slightly more "right" nor the other slightly more "wrong".
 

morricab

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As long as the voice coil assembly doesn't come out when you remove the back cover, it should work.

Danny Ritchie (GR Research) and Clayton Shaw (Spatial Audio) have both done this in high-end dipole speakers. Just don't bump the unprotected diaphragm! Clayton had a protective grille made .



I don't think either one is slightly more "right" nor the other slightly more "wrong".
I will give it a go with my big horns as they are probably the ones that can benefit the most from a bit more "air" and space. :cool:
 

carolus

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As long as the voice coil assembly doesn't come out when you remove the back cover, it should work.

Danny Ritchie (GR Research) and Clayton Shaw (Spatial Audio) have both done this in high-end dipole speakers. Just don't bump the unprotected diaphragm! Clayton had a protective grille made .



I don't think either one is slightly more "right" nor the other slightly more "wrong".
As long as the voice coil assembly doesn't come out when you remove the back cover, it should work.

Danny Ritchie (GR Research) and Clayton Shaw (Spatial Audio) have both done this in high-end dipole speakers. Just don't bump the unprotected diaphragm! Clayton had a protective grille made .



I don't think either one is slightly more "right" nor the other slightly more "wrong".
As long as the voice coil assembly doesn't come out when you remove the back cover, it should work.

Danny Ritchie (GR Research) and Clayton Shaw (Spatial Audio) have both done this in high-end dipole speakers. Just don't bump the unprotected diaphragm! Clayton had a protective grille made .



I don't think either one is slightly more "right" nor the other slightly more "wrong".

@Duke Le Jeune
@morricab

FYI
Another second test in a nut shell ..
1 °) same divers / horn direction, I pooled the two drivers the other way around .... "in reverse" (the + on - and the _ on +).
I may suppose voice coils are now in phase physicaly (!).
2 °) subjective acoustic impressions; ..... perceptions audibly "the same" (no significant difference) ...
3 °) Measurement with IR .... quasi the same (it's normal dixit my prof. acoustique)
4 °) Musical scene and the Wow factor .... ne variatur.

... it all remains "subjective" ... (and difficult to measure)

My WAF suggest to go back in the normal horn-set-up .... with (musical) love ...

Karel
 

Duke LeJeune

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My WAF suggest to go back in the normal horn-set-up .... with (musical) love ...
Do you have enough room to place that up-and-rear firing horn behind your front-firing horns? That might help the Wife Acceptance Factor and would increase the path length, which adds a bit more time delay.

I THINK one of the mechanisms in play (which might benefit from a bit more time delay) is this:

The additional reverberant energy arrives after an "unexpectedly" long time delay, and therefore "contradicts" the small-room-size cues that "normal" reflection path lengths imply to the brain. As the "small room signature" cues become weaker, the spatial cues of the recording venue (whether real or engineered) are less likely to be obscured.

If you notice a greater variation in the soundstage from one recording to the next, this would be an indication that you are actually hearing MORE of the recording and LESS of the room.
 

Robh3606

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Ok but what about the rear wave frequency response?

With a cd horn you eq for flat on axis through the horn. Whats the backwave going to look like? Will the impedence change?

If you are not on a CD horn you will get the response with all the rolloff after the mass break point.

So CD may work but non CD??

Rob :)
 
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Tim Link

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I forgot to post the new Polk speaker, this has active crosstalk elimination. It DOES work! I do think you can get a similar result with a setup where the speakers are placed wider than usual with more toe-in, especially with a more directional speaker. However, a big advantage of the Polks with the crosstalk elimination is you have more flexibility on placement, they can be placed closer together than normal and still project a massive soundstage. In many situations this is a significant advantage!

I should try to find a way to listen to those. I had the SDA-2 back in the early 1990s. I didn't hear the SDA effect at all back then, but I don't think I ever got myself accurately positioned between the speakers.
 

Duke LeJeune

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Ok but what about the rear wave frequency response?

With a cd horn you eq for flat on axis through the horn. Whats the backwave going to look like? Will the impedence change?

If you are not on a CD horn you will get the response with all the rolloff after the mass break point.

So CD may work but non CD??

Rob :)
Good question - I don't know what the rear wave's frequency response would look like.

My guess is that the impedance curve would be different (less peaking at resonance), which could affect a passive crossover.

I don't use this technique so I don't know what all of the implications are.
 
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the sound of Tao

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Good question - I don't know what the rear wave's frequency response would look like.

My guess is that the impedance curve would be different (less peaking at resonance), which could affect a passive crossover.

I don't use this technique so I don't know what all of the implications are.
I was going to ask about this also Duke.

Also could opening up the back chamber on the horn have other sonic implications. My newby technical skills have clearly (considerable) ways to go.
 

morricab

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I was going to ask about this also Duke.

Also could opening up the back chamber on the horn have other sonic implications. My newby technical skills have clearly (considerable) ways to go.
Easy to remove and easy to put back on if it doesn’t work out.
 

Robh3606

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Also could opening up the back chamber on the horn have other sonic implications. My newby technical skills have clearly (considerable) ways to go.

If you have never opened one before it's no big deal just watch out with the cover off. That's the working end of the driver and the magnetic field is remarkably strong so don't be careless with a screw driver and make sure any loose hardware is kept away.

Rob :)
 

Audiophile Bill

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If you have never opened one before it's no big deal just watch out with the cover off. That's the working end of the driver and the magnetic field is remarkably strong so don't be careless with a screw driver and make sure any loose hardware is kept away.

Rob :)

Agree and make sure you do it in a really clean area. Is amazing how these tiny little fragments that get picked up by the magnet. Those of us familiar with full range drivers are only too aware of this with the dreaded air gap.
 
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Mark Seaton

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I am actually thinking, what if I simply take the back cover off of the compression driver? As you probably know, these drivers are essentially inverted domes with the concave part coupling to the horn throat and the convex side of the dome firing into a damped back plate. Just removing that plate would expose the convex (dome) side of the diaphragm and would act as a natural dipole. Why bother with another driver when you already have a dipole handy?

Now, what the Carolus was doing was another driver wired in phase with the front one, which makes a bipolar response. This is not how panel speakers or open baffle speakers work as the back wave is out of phase with the front one, making it a dipole. Which is more correct for creating a sense of space? I am not sure but would be worth the while to experiment and what easier way than just to take the back cover off your compression driver. You could do it with the PAPs right away. With my Odeons it is not possible but with my other system, where the horn sits exposed, I don't see why not to try it.

It shouldn't impact the driver as I think the system doesn't rely on pressure in that chamber for anything. I think the diaphragm is wholly controlled by the very powerful magnets used and the compression chamber is on the other side of the diaphragm.

Maybe someone can correct me if I am wrong about this.

What is possible in opening the back of the driver is dependent on the specific compression driver. Many use the rear cover to secure and align the voice coil/diaphragm assembly. I'm not certain, but I seem to recall both cases of Danny Richie and Clayton Shaw they cut away the center of the rear cap to maintain the ring which secures the diaphragm and holds the driver together.

I would be very surprised if opening the back of the dome did not alter the acoustic behavior on the front side of the horn. Yes, the magnet, and therefore Qes is likely more dominant to the Qts and damping of the resonance, but that doesn't eliminate the effect of the chamber size, especially on the resonant frequency of the diaphragm (Fs). In fact the magnet/motor has zero impact on the resonant frequency. It only affects the damping at that frequency. You are changing it's operating condition from a very tiny sealed back chamber to a large open space, so the Fs is now only dependent on the mass and suspension. Depending on the crossover frequency vs the original Fs of the compression driver this may or may not not make for a significant change, but it will change the impedance curve and in some situations could make a significant change in response. That's not to say it's not useable, but absolutely different and something that needs to be accounted for and checked in use to maintain appropriate frequency response and make sure there isn't chance of damage to the dome from over excursion.

The rear output will directly relate to the excursion of the diaphragm and not be affected by the front side acoustic loading or intensity change from the horn or waveguide. It will have a different balance than the front side.

My recommendation is if you don't have tools ready to take a before/after impedance measurement and a microphone with REW or similar to check the response (both very inexpensive tools), I wouldn't chance such modifications.
 
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morricab

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What is possible in opening the back of the driver is dependent on the specific compression driver. Many use the rear cover to secure and align the voice coil/diaphragm assembly. I'm not certain, but I seem to recall both cases of Danny Richie and Clayton Shaw they cut away the center of the rear cap to maintain the ring which secures the diaphragm and holds the driver together.

I would be very surprised if opening the back of the dome did not alter the acoustic behavior on the front side of the horn. Yes, the magnet, and therefore Qes is likely more dominant to the Qts and damping of the resonance, but that doesn't eliminate the effect of the chamber size, especially on the resonant frequency of the diaphragm (Fs). In fact the magnet/motor has zero impact on the resonant frequency. It only affects the damping at that frequency. You are changing it's operating condition from a very tiny sealed back chamber to a large open space, so the Fs is now only dependent on the mass and suspension. Depending on the crossover frequency vs the original Fs of the compression driver this may or may not not make for a significant change, but it will change the impedance curve and in some situations could make a significant change in response. That's not to say it's not useable, but absolutely different and something that needs to be accounted for and checked in use to maintain appropriate frequency response and make sure there isn't chance of damage to the dome from over excursion.

The rear output will directly relate to the excursion of the diaphragm and not be affected by the front side acoustic loading or intensity change from the horn or waveguide. It will have a different balance than the front side.

My recommendation is if you don't have tools ready to take a before/after impedance measurement and a microphone with REW or similar to check the response (both very inexpensive tools), I wouldn't chance such modifications.

All very good advice, thx. I realize that the resonance is likely to change and I would be measuring along the way (I don't have a way to measure the impedance though). The Beyma driver I am thinking of trying I believe has the diaphragm mounted with screws to hold the diaphragm in place and not the rear cover. So, no need to perform surgery and relatively easy to measure before and after.

What do you think will likely happen with the resonance frequency? Wouldn't it be lowered or is that difficult to assume?
 

Robh3606

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All very good advice, thx. I realize that the resonance is likely to change and I would be measuring along the way (I don't have a way to measure the impedance though). The Beyma driver I am thinking of trying I believe has the diaphragm mounted with screws to hold the diaphragm in place and not the rear cover. So, no need to perform surgery and relatively easy to measure before and after.

What do you think will likely happen with the resonance frequency? Wouldn't it be lowered or is that difficult to assume?

Just remember you won't have the terminals which are usually attached to the cover so you will have to use some method to get signal to the driver. Minor surgery depending on if its clips or screws

Rob :)
 
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Mark Seaton

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All very good advice, thx. I realize that the resonance is likely to change and I would be measuring along the way (I don't have a way to measure the impedance though). The Beyma driver I am thinking of trying I believe has the diaphragm mounted with screws to hold the diaphragm in place and not the rear cover. So, no need to perform surgery and relatively easy to measure before and after.

What do you think will likely happen with the resonance frequency? Wouldn't it be lowered or is that difficult to assume?
The resonant frequency will always shift lower with such a change. The air spring stiffness of the chamber behind the dome acts in parallel to the stiffness of the diaphragm surround. Opening the rear effectively eliminates this added stiffness. The amount of change observed will vary for each driver, but softer always makes the resonance shift lower.

The question is just how much lower, how much that effects the frequency response, and then how the accompanying impedance curve change will affect the crossover behavior. In some cases this will significantly change the response around the crossover, or create a response bump below the crossover frequency which can put too much signal to the driver at low frequencies.
 

morricab

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The resonant frequency will always shift lower with such a change. The air spring stiffness of the chamber behind the dome acts in parallel to the stiffness of the diaphragm surround. Opening the rear effectively eliminates this added stiffness. The amount of change observed will vary for each driver, but softer always makes the resonance shift lower.

The question is just how much lower, how much that effects the frequency response, and then how the accompanying impedance curve change will affect the crossover behavior. In some cases this will significantly change the response around the crossover, or create a response bump below the crossover frequency which can put too much signal to the driver at low frequencies.
As I am using active crossovers the impedance change shouldn’t matter much.
 

jdza

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The driver I use here in JBL literature. Impedance on plane wave tube and JBL horn




Impedance curve of the driver on my horn without its rear cover. Not really apples to apples then but unfortunately I no longer have the before removal curve and am too lazy to refit it for measurement only. I would say the second curve does not really indicate imminent self-destruction?



I can only repeat what I wrote before; the unloaded rear output of the driver is minuscule and hardly audible at any distance. It may have a minuscule dipole effect but I seriously doubt it.
 
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Mark Seaton

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The driver I use here in JBL literature. Impedance on plane wave tube and JBL horn




Impedance curve of the driver on my horn without its rear cover. Not really apples to apples then but unfortunately I no longer have the before removal curve and am too lazy to refit it for measurement only. I would say the second curve does not really indicate imminent self-destruction?



I can only repeat what I wrote before; the unloaded rear output of the driver is minuscule and hardly audible at any distance. It may have a minuscule dipole effect but I seriously doubt it.

I never meant to suggest every person doing this is likely to destroy their driver if they open the back of the compression driver. I only meant to caution that it does significantly change the behavior of most drivers. If you are using 5-25W amplifiers on passive speakers, it's highly unlikely you could cause damage in even the worst case examples. It could create some significant changes in a passive crossover response, especially near and below the intended crossover. I recall both product examples more looking to the benefits of eliminating rear chamber confinement and resonances, with any rear driver output being a modest benefit. The intensity difference from the front vs rear will depend a lot on the horn type, angle, and size. The more loading and gain provided by the horn, the bigger the difference will be.

In the case of the impressive horns you showed pictures of, I would expect a greatly reduced output from the back side of the driver vs from the horn. Opening the back of the driver in your case likely reduced some chamber resonances and lowered the resonance of the driver. It appears the horn you have is much deeper and loads lower than the 2393, which is why the bulk of the impedance peak is much lower, but the rear of the driver removed likely shifts that peak lower as well as reducing chamber resonances. Both changes would be likely to contribute to the subtle benefits you described in an earlier post.
 

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