Just a comment. Stax have made the 4070 closed-back electrostatic headphone, and had succes. An electrostatic speaker with a closed back would sell even more than an open I imagine. But, the final question, will high end users not buy them because of their non-tweakable nature ??
New way for absorbing back wave?
- Thread starter ted99
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amey01
Well-known member
Sorry - I have to disagree on this one. Live music just sounds different. I've said this one before too. Walk past a bar on a Saturday night and even my 95 year old grandmother will be able to tell you whether it is live or recorded music playing. It is that obvious.
Now, I'm not talking sound quality "per-se" here - just that it sounds different.
I've also before told of my experience at a local shopping centre. I walked in and noticed that the crappy PA system sounded particularly fantastic. I was looking up at the speakers wondering if they had been upgraded or changed, only to turn the corner and see a live band playing into a live feed to the PA system.
Live sounds different to recorded - sure, recorded might do "imaging" better, or "bass" better or "midrange purity" better, but it will never do that all important conveying the message of the composer better.
Amey01, I'm not so sure that you are disagreeing with me. I completely agree that live music generally sounds "different" than recorded. As I stated above, live music has multiple point sources of instruments playing in a particular acoustic space and your listening experience is affected by where you are located in that space and what else is in the room. That is a very different beast than recording the same music by placing mics in optimum positions, then engineering the recording for equalization and the like, and then playing the recording back on a stereo music system. They are two totally different methods of creating sound and will of course sound different. As you seem to agree, I also believe that recorded music can (and on my system, does) sound better than most live music.
Because of that, among other things, I question the utility of using live music as a reference by which we judge our system's performance. You can never replicate the actual sound of live music because they are just too different in their methodology of sound reproduction. And, as I have said, whatever quality makes live music sound "live" does not necessarily make it sound "better." I think my system sounds better than the live music that I have listened to. For instance, I heard Allison Krauss and Union Station live (front row, center seats) at my local concert hall, and there is no question to me that their Live CD or DVD sounds tons better on my system than that live performance did. I simply believe that you can judge the quality of your system with reference to other stereo systems much more realistically than using live music as a reference.
As for live music "conveying the message of the composer" better, I'm not sure how you can make such a broad subjective statement, and more so how you would go about proving it. I don't see how you could possibly state that one or the other does a better job of this or how you could really know if it did.
Hmm ..
Ill throw my hat in this ! Although I like my recorded music to be mixed just right. Live is LIVE, It may not be the best live sound as the hall or club or venue may have terrible acoustics. How many of you have seen the same performer in different venues that sounded great in one and HORRIBLE in another. The single most important factor in these systems we call our own is THE ROOM. Some rooms are live and may need treatment. Some are dead and will need help too. I still prefer the sound of a live jazz or blues band playing through their PA systems with no real image other than the venues ability to reflect and bounce the sound. Here is a great example. Put a good band outside with no room and they still sound good. Its the same if you have a small Orchestra at a outside wedding. Do I judge Live as the bench mark to which I try and emulate. NOPE! As stated earlier. I have heard some poor live shows that I knew the band was good. I try and get a few great recordings that have that live sound and tweak my system to duplicate that. The sad part is , that most of your poorly recorded and mixed music will sound worse. Its not your systems fault. Its the ROOM!
I do believe in treatments. I am experimenting right now. I haven't found the golden snitch yet, but I'm close.
As for the rear reflection being blocked early . NOPE . I want some delay to happen and if I'm gonna treat a room I want the rear wave to help not hinder it. I think many here do not play around enough with their room placements and realize that the norm sometimes is not the best. What looks good to the eye as in placement is not always the best for the ear. I had a pair of Magnepans that the only way to get a great image was to off set them in placement. One was a bit different than the other. It was a room issue. I had many people ask why is one crooked ? I said sit down and close your eyes. Trust me I am KING of try any Rube Goldberg approach to get better sound.
To this Ill end my .02 cents worth. What sounds the best to YOU is what YOU use or do. Last time I looked not one person here is paying for my equipment or donating to my audio habit. I think its Roberto who always says "Trust your ears"
Ill throw my hat in this ! Although I like my recorded music to be mixed just right. Live is LIVE, It may not be the best live sound as the hall or club or venue may have terrible acoustics. How many of you have seen the same performer in different venues that sounded great in one and HORRIBLE in another. The single most important factor in these systems we call our own is THE ROOM. Some rooms are live and may need treatment. Some are dead and will need help too. I still prefer the sound of a live jazz or blues band playing through their PA systems with no real image other than the venues ability to reflect and bounce the sound. Here is a great example. Put a good band outside with no room and they still sound good. Its the same if you have a small Orchestra at a outside wedding. Do I judge Live as the bench mark to which I try and emulate. NOPE! As stated earlier. I have heard some poor live shows that I knew the band was good. I try and get a few great recordings that have that live sound and tweak my system to duplicate that. The sad part is , that most of your poorly recorded and mixed music will sound worse. Its not your systems fault. Its the ROOM! I do believe in treatments. I am experimenting right now. I haven't found the golden snitch yet, but I'm close.
As for the rear reflection being blocked early . NOPE . I want some delay to happen and if I'm gonna treat a room I want the rear wave to help not hinder it. I think many here do not play around enough with their room placements and realize that the norm sometimes is not the best. What looks good to the eye as in placement is not always the best for the ear. I had a pair of Magnepans that the only way to get a great image was to off set them in placement. One was a bit different than the other. It was a room issue. I had many people ask why is one crooked ? I said sit down and close your eyes. Trust me I am KING of try any Rube Goldberg approach to get better sound.
To this Ill end my .02 cents worth. What sounds the best to YOU is what YOU use or do. Last time I looked not one person here is paying for my equipment or donating to my audio habit. I think its Roberto who always says "Trust your ears"
While I won't say yet whether this approach is legit or not from an overall quality standpoint, I would like to point out that ML themselves do this with the Motif Center.
That is, they place an absorber within an inch or two of the rear stator.
I haven’t' heard the Motif owners complaining about their speakers...
So it's not going to harm the system per se. But as one person pointed out, keep any foam bits out of the stators.
Monopole vs. dipole
Much of the angst seems to be centered around the ‘heresy’ of turning a Dipole ESL into a monopole.
My take is it’s perfectly OK to want a monopole speaker. And if an ESL is the best transducer, then finding an acceptable way to make it a monopole radiator is fine.
The challenge is that with such a significant back-wave, it’s a bigger challenge than say a 5” long ribbon tweeter (which are dipole radiators intrinsically, yet configured and packaged as Monopoles.
There re several approaches to absorbing or isolating the rear wave of a large dipole. Few of them pretty and all quite complex to pull off.
In many ways, treating the walls is the simplest solution, even though it might not seem so at first.
Much of the angst seems to be centered around the ‘heresy’ of turning a Dipole ESL into a monopole.
My take is it’s perfectly OK to want a monopole speaker. And if an ESL is the best transducer, then finding an acceptable way to make it a monopole radiator is fine.
The challenge is that with such a significant back-wave, it’s a bigger challenge than say a 5” long ribbon tweeter (which are dipole radiators intrinsically, yet configured and packaged as Monopoles.
There re several approaches to absorbing or isolating the rear wave of a large dipole. Few of them pretty and all quite complex to pull off.
In many ways, treating the walls is the simplest solution, even though it might not seem so at first.
ted99
Member
I have removed two of the layers, which is quite easy to do, and this picture shows the result. It looks much neater, and the foam is bowed away from the panel. I can now hear a much reduced backwave sound when I put my ear close to the foam at the back of the speaker, where I could hear nothing with the three layers.
I am pursuing this to improve the imaging and clarity of the sound during movie playback. I subscribe to the opinion advanced by some on this forum that there is undesirable interference between the front wave and reflected backwave when the speaker is placed relatively close to the front wall. In my home theater, the front speakers must be placed close to the front walls to avoid having them much too close to the front row of seating. The center speaker is behind the screen and only one foot from the front wall. I kept the three layers of foam attached to the front wall, which brings the front edge of the foam to about 8 inches behind the M-L Theater center speaker.
My ear hears a clearer dialog with the foam in place--can't do an A/B because it's glued in place. I'm happy with it and will keep it. The single layer of foam on the L/R fronts seems to be equally effective in improving the sound as the triple layer. I have cotton-lined silk curtains directly behind the L/R fronts (Ascent i) and a 1/4" heavy rubber carpet pad behind them on the wall. All of this foam and padding is invisible to my wife and therefore acceptable to her. I suspect that the single layer of foam attenuates the back wave sufficently that the additional curtains/lining/pad can control the back wave. The YPAO frequency compensator does not detect a polarity mismatch, so I evidently do not have a lot of backwave propagation. It sounds good to me, where the original instalation with the "bare" Ascents sounded a little muddy, in comparison. I must confess that I was certainly not unhappy with the unfoamed sound. The M-L ascents replaced a pair of large Mirage mains (don't remember the model, but they had the backward firing mid-range driver) and the increase in clarity was striking. I persued this foam idea because I was getting polarity mismatch messages and research of other threads on this forum suggested that attenuation of the backwave would be desirable. I like the new sound.
I am pursuing this to improve the imaging and clarity of the sound during movie playback. I subscribe to the opinion advanced by some on this forum that there is undesirable interference between the front wave and reflected backwave when the speaker is placed relatively close to the front wall. In my home theater, the front speakers must be placed close to the front walls to avoid having them much too close to the front row of seating. The center speaker is behind the screen and only one foot from the front wall. I kept the three layers of foam attached to the front wall, which brings the front edge of the foam to about 8 inches behind the M-L Theater center speaker.
My ear hears a clearer dialog with the foam in place--can't do an A/B because it's glued in place. I'm happy with it and will keep it. The single layer of foam on the L/R fronts seems to be equally effective in improving the sound as the triple layer. I have cotton-lined silk curtains directly behind the L/R fronts (Ascent i) and a 1/4" heavy rubber carpet pad behind them on the wall. All of this foam and padding is invisible to my wife and therefore acceptable to her. I suspect that the single layer of foam attenuates the back wave sufficently that the additional curtains/lining/pad can control the back wave. The YPAO frequency compensator does not detect a polarity mismatch, so I evidently do not have a lot of backwave propagation. It sounds good to me, where the original instalation with the "bare" Ascents sounded a little muddy, in comparison. I must confess that I was certainly not unhappy with the unfoamed sound. The M-L ascents replaced a pair of large Mirage mains (don't remember the model, but they had the backward firing mid-range driver) and the increase in clarity was striking. I persued this foam idea because I was getting polarity mismatch messages and research of other threads on this forum suggested that attenuation of the backwave would be desirable. I like the new sound.
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sleepysurf
Well-known member
,
Jon, I have the Motif, and the absorber is really a thin (acoustically transparent) fabric "sock" on a perforated frame, which presumably allows the back wave entry into the enclosure, and then reflected back (unless there is additional absorptive material inside the enclosure). The fabric/frame is not right up against the panel, but actually curved away in a mirror image.
The 4th pic in the Motif Picture Gallery gives a good perspective...
http://www.us.martinlogan.com/gallery/motif
Alan,
The sock is indeed a 'grille cloth' type fabric placed over a plastic frame with holes in it that manage the airflow into a 1/2" thick sandwich of acoustic absorption materials. These dampen the mids and highs (not very effective below 700Hz or so IMHO).
I examined these items carefully during our factory visit. If you recall, it was the motif and its prototypes they had on the table. They clearly worked on the absorber, as they had several iterations of it.
The enclosure is for the mid-bass/woofers, and is a solid surface, which is why they required that absorber.
So they learned from the Logos, which did not have any absorption and was a comb-filtering queen.
Note to Logos owners: Experiment with some 1/2" absorption between the stators and the box. look for something that will do even absorption between 500hz and 3Khz.
It might take a sandwich of thin foam and something denser to achieve that.
sleepysurf
Well-known member
Cool! Nice to know they sweat the details (like somebody else we know in Big Canoe, GA)
If you have placement challenges, this is a reasonable thing to try. And for your center, it’s absolutely the right thing to do.
As you note, dialog is much enhanced due to lack of reverberant artifacts.
Since you have an acoustically transparent screen, I'd treat the entire wall behind it, not just the area behind the center. This will dampen all reflections from the screen material.
If you like what you hear, and prefer over the 'bare' version, then it means it's working for you.
My only reservation, and I'll use my spare SL3 and some of the same foam (I also have RPG profoam and have a half panel I can stuff the SL3 with) and do some measurements of the difference between putting the faom like you do, 4 or five inches from the stator, or on a wall 18" away.
My concern would be that the foam still reflects a good bit of the energy, and it's coming right back through the stator, so there will some comb-filtering.
But we’ll see how severe, and if it even matters.
ted99
Member
Jonfo--excellent! Actual A/B measurements are what is needed. My seat of the pants may satisfy my ear, but it should not be a substitute for objective measurements. Your effort may be just what is needed for this methodology to be useful and I look forward to the results. My ear could be hearing what I want it to hear (placebo effect).
Jon,
You mentioned in another thread recently about taking measurements with aborbants at various distances behind the front speakers to determine if there is an optimum distance. Have you gone into it yet? Curious to see the results.
Ben, that's the plan for this weekend. I was getting the measuring rig out then anyway.
I'll test the following combo's using the SL3.
Positioning will be toed out a bit, as I don't think anyone places their speakers straight on to the wall. This will mean the ‘bare wall’ won’t be quite as horrible as it could be.
All measurements will be taken from a static location at around 6 to 8’ from the panel to ensure we are measuring both front and rear wave effects.
I'll test the following combo's using the SL3.
Positioning will be toed out a bit, as I don't think anyone places their speakers straight on to the wall. This will mean the ‘bare wall’ won’t be quite as horrible as it could be.
All measurements will be taken from a static location at around 6 to 8’ from the panel to ensure we are measuring both front and rear wave effects.
- Bare wall behind at 18", 24" and 36" from rear of panel
- ProFoam Treated wall at same distances
- Minitrap HF treated wall at same distances
- Profoam stuffed into SL3 frame as depicted, with a 4” or so gap to the stator.
This is GOOD ! I just made a big panel with some batting and fabric and MDF . It is stopping the rear waves from going crazy with all that diffusion from my stone fire place. I did not want to hide to much of anything. I just wanted the rear wave to be even. (it also hides the fireplace opening too). From initial listening it has made the stage centered and deeper with a bit more focus. Ill post pics soon !
Jon,
Fantastic! I shall look forward to seeing the results. May I suggest a reading with the trap at the focal point too.
Actually, my Mini HFs are angled against the wall about 4.5ft away, parallel to the speakers. Just thought it would provide a more comprehensive cover for the backwave.
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Measurements and analysis
OK Folks, I spent the afternoon testing and measuring, so here come the results as I alluded to in post #54
All these measurements were taken powering the panel only, with an external crossover set for 337Hz prior to feeding the amp.
Mic was 6’ from the panel when it was at 26” from the wall behind it. The mic was not moved (so room influences would remain constant across the measurements).
First, let’s look at the ProFoam stuffed into the speaker vs having a MiniTrapHF on the wall some 36” behind the speaker.
In this frequency response shot, they don’t look all that different, although the MiniTrapHF yields flatter frequency response.
OK Folks, I spent the afternoon testing and measuring, so here come the results as I alluded to in post #54
All these measurements were taken powering the panel only, with an external crossover set for 337Hz prior to feeding the amp.
Mic was 6’ from the panel when it was at 26” from the wall behind it. The mic was not moved (so room influences would remain constant across the measurements).
First, let’s look at the ProFoam stuffed into the speaker vs having a MiniTrapHF on the wall some 36” behind the speaker.
In this frequency response shot, they don’t look all that different, although the MiniTrapHF yields flatter frequency response.
Attachments
Moving on to the Bode response (which is not as smoothed as the third-octave one above), the results here show a rise in the lower midrange, as there is a big hump below 1Khz, and the resonances between 1Khz and 4Khz are quite noticeable compared to those of the MiniTrapHF back on the wall.
This makes sense, as the profoam is still somewhat reflective and the resonances build in the cavity between the stator and the foam. Whereas the MiniTrap has sufficient distance and better absorption to minimize these resonances.
This makes sense, as the profoam is still somewhat reflective and the resonances build in the cavity between the stator and the foam. Whereas the MiniTrap has sufficient distance and better absorption to minimize these resonances.
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Comparisons at 24”
Here we see the Bode response of the three materials at 24” from the wall.
You can see that the least resonances come from the minTrapHF, and the most from a bare wall. The profoam is in-between.
The waterfall plots make it even clearer that the MinitrapHF let’s the sound decay much quicker than the others do.
Best Option: MiniTrapHF
Here we see the Bode response of the three materials at 24” from the wall.
You can see that the least resonances come from the minTrapHF, and the most from a bare wall. The profoam is in-between.
The waterfall plots make it even clearer that the MinitrapHF let’s the sound decay much quicker than the others do.
Best Option: MiniTrapHF
Attachments
Comparisons at 36”
Here we see the Bode response of the three materials at 36” from the wall.
Again, we see that the least resonances come from the minTrapHF, and the most from a bare wall. The profoam is in-between.
The waterfall plots again show that the MinitrapHF let’s the sound decay much quicker than the others do, and the additional distance is beneficial to all three surfaces.
Best Option: MiniTrapHF
Here we see the Bode response of the three materials at 36” from the wall.
Again, we see that the least resonances come from the minTrapHF, and the most from a bare wall. The profoam is in-between.
The waterfall plots again show that the MinitrapHF let’s the sound decay much quicker than the others do, and the additional distance is beneficial to all three surfaces.
Best Option: MiniTrapHF
