# A Soundstage Enhancement Experience



## AudiocRaver

*A Soundstage Enhancement Experience*

One of the side projects during our recent High-End Amplifier Evaluation Event at Sonnie Parker's Cedar Creek Cinema was working on the soundstage and imaging with Sonnie's speakers. His MartinLogan ESL hybrid electrostatics were set up very nicely when we arrived, so we avoided moving them through the weekend. There were some improvements made to the soundstage and imaging by way of room treatments, and some interesting twists and turns along the way which turned out to be very informative.

I arrived a day ahead of the other evaluators to help with preparations and immediately we sat down to listen to the ESLs. They sounded excellent, with the wide, deep soundstage that we have learned to crave and enjoy. I did note that the imaging, while apparently very stable (although a test track would soon prove otherwise), was a bit broad and soft. A pinpoint source came across about the size of a beach ball, not terrible, but not what I knew the ESLs and the room were capable of.

The speakers were placed widely in the room. From the main listening position (LP), one could look past the inside edges of the panels and see the front corners of the room. I noticed that Sonnie had placed large diffuser panels under the movie screen on the left and right, as is commonly recommended. They were of the type of construction which ended up reflecting the majority of sound forward into the room, with much of those reflections going toward the LP.

I will go on record here as stating that this is NOT good for imaging. Apparently I am a lone voice in this regard. I recently had a discussion explaining this point with several other serious, experienced listeners and was unable to convince them of this, being counter to the accepted approach. Diffusion on the front wall is excellent for adding spaciousness to the room's sound, the reason it is recommended. But a design which reflects energy toward the LP, as Sonnie's diffuser was, and as most diffusers do, as far as I can tell, will have the effect of delivering energy from many points across the front wall to the LP. The result cannot help but be a softened image, as we heard in Sonnie's room at that time.

On the other hand, a diffuser which is constructed with angles so that all of the energy is deflected at angles away from the listening position, with no energy reflected directly at the LP, would be an excellent design for front of room. It would add spaciousness without softening the image at all. I have experimented with this in my own room and found it to be true, just as it was being confirmed in Sonnie's room.

Our conversation went to other topics, and before I had a chance to raise the point of this soft imaging we were discussing ways to set up double-blind tests for the amplifier evaluation to come. A quick way to hide amplifiers under test would be to use those very diffusers pulled forward and placed in front of the stage and in front of the amplifiers to hide them. We did this and to my delight the next time we heard music through the ESL speakers, the imaging was tight and sharp as I knew it could be.

We moved forward with preparation for the amplifier evaluation, which included setting up the Spacial Hologram M1 speakers loaned to us by Clayton Shaw of Spacial. The M1 gave us an amazing wide, deep sound stage with pinpoint imaging. Their coaxial driver design was instrumental in allowing this to happen. They have been reviewed separately (follow this link), so I will not go into detail here, other than to note that they also benefited from the absence of reflections toward the LP from along the front wall.

As we began the sighted tests and evaluations of amplifiers on Friday, the diffuser panels were moved to the back of the room. Most of the listening was done with the M1, but we did hear from the ESL from time to time, and both speakers gave crystal clear and very sharp imaging through that day.

Saturday, we started double-blind amplifier tests, and at this point the room arrangement changed somewhat. Diffuser panels were back at the front of the stage as planned to hide amplifiers under test, but there were also some sheets and blankets used to cover different areas of visibility, plus all of the amplifiers not being tested were placed in front of the stage with blankets covering them so we could not see which were there. The result of all this, as Dennis already mentioned in his comments, was that the sharp imaging and we had experienced on Friday was now somewhat cluttered and chaotic. It was quite distracting, but there was no quick way around it and we had to make progress, so we did not make a big deal of it. The lesson, of course, is that any objects in the front of the room are creating extra reflections and will disrupt the soundstage and imaging. Thinking in terms of home listening rooms, the "barren front of room" method is not good for those who prioritize room decor very highly. Good luck selling the idea to the _significant other._

Once the amplifier evaluation exercise was completed, all of the amplifiers and diffusers were moved from the front of the room, and imaging and soundstage returned to their best crisp, tight delivery. Pretty much.

One track which I had not listened to in that room before, but had relied upon as a test track Friday and Saturday, was the Nickel Creek song, _House of Tom Bombadil._ I noticed that the mandolin on the left and guitar on the right both seemed somewhat disembodied, the higher plucking sounds coming from close to the speakers and the lower range tones of the bodies of the instruments coming from closer to the center of the soundstage. This effect became very pronounced at the point in the song where a guitar solo starts in the high registers, progresses down to lower and lower notes, then goes back up to the high registers again. Through the solo, the lower tones of the guitar moved closer and closer to the center of the soundstage, then crept back out to the speaker again by the end of the solo. This occurred with both the Spatial M1 speakers and the MartinLogan ESL speakers.

With both of the speaker models being dipole designs, there is a lot of energy coming from the rear of the speaker and reflected off the front wall. The lower the frequency, the wider the dispersion of that rear wave, allowing the apparent reflection point off the front wall to move inward toward the center of the soundstage.

The remedy for this was to place absorptive panels under the movie screen left and right, which completely solved the problem. Back to the previous point on the construction of diffuser panels, a design which directed all the reflected energy away from the LP would have worked just fine instead of the absorptive panels. Remember also that at lower frequencies the smaller angles and surfaces of a diffuser tend to look like one big flat surface due to the longer wavelength. While I have not experimented with it to verify, it might be that the ideal front wall diffuser is absorptive at frequencies below 1 kHz or so, and reflective with angles away from the LP at frequencies above that.

As Sonnie and I began working with soundstage refinements, those absorptive panels had been removed again. We discussed the progression of events and effects on the imaging and soundstage up until that time, and made a few final changes. All of this was done without moving the speakers.

At this point, we discussed some of the experiments I had done with my own ESL speakers over the last year, and Sonnie was very willing to try them in his room. The first step was to widen the reflection points for the rear waves so that they came from almost the same listening angles as the front waves. This was done using the back sides of the diffuser panels, placed almost behind the ESL speakers as viewed from the LP. The angles of those reflective panels were carefully adjusted using laser and mirror so the rear wave from the ESL was directed straight to the LP. Distance, or path length, was carefully adjusted using impulse diagrams with REW so the left and right reflected waves arrived at the LP within about 20 microseconds of each other (1/4 in path length match). Path length matching requires a non-USB omni mic and a 2-channel audio interface so REW can be run with a loopback timing reference.

The resulting impact from accomplishing that precise relative timing of the reflected waves was striking to say the least. Imaging, however, was less than ideal because of the original natural reflection points on the front wall. The absorptive panels went back into place below the center of the screen to solve that problem, as we had done before. (Again, given diffuser panels of the desired design, they could have been used instead.)

Now we had everything we wanted. With the direct and reflected phantom image lines (the direct phantom image line stretching from speaker to speaker and the reflected phantom image line stretching from reflection panel to reflection panel) almost perfectly overlaid from the LP point of view, their psychoacoustical sum became the most consistent, realistic soundstage we had yet experienced with any speakers in that room. It was wide, deep, spacious, had good depth acuity, and the kind of striking dynamic impact rarely experienced with dipole speakers, more like you usually hear from high-efficiency designs like horns. The elimination of any front wall reflections to the LP other than from the new reflection points created with the panels behind the speakers - as viewed from the LP - resulted in razor-sharp imaging from all points in the soundstage and complete freedom from any wandering instruments.


Additional Notes:

Audyssey xT32 setup was run after the final changes were made. This explains why the initial delay is over 40 mS on the impulse reaponse diagrams. Over 30 mS of that is processing time in the AVR.
ESL Setup Dimensions:
Speaker plane (between front center points) to ear plane = 69 in
Speaker spacing center to center = 108 in
Speaker plane to front wall = 85 in
Speakers to side walls = 60 in
Toe-in = 15 deg
Listening Angle = 21.5 deg off-axis
Room width = 234”
Front wall to listener = 156”

Alternate reflection surface:
For alternate reflection points, the back sides of the diffuser panels were used as a matter of convenience. That was what we had that was the needed size. It was covered with fabric, so high frequencies were somewhat dampened. The results:
Medium bright soundstage (before Audyssey or EQ).
Reflected impulse is short and wide.

In my experiments I have worked with a plain wooden surface, a 1x10 board standing 6 ft tall.
Very bright soundstage (before Audyssey or EQ).
Reflected impulse is tall and narrow.



The following diagrams show the final result.

Top view. The direct path lengths - A-left and A-right - are, of course, carefully matched. The original natural reflections off the front wall - B-left and B-right - are eliminated, in our case with absorptive panels, or else with the properly designed (see text) diffuser panels, so imaging is optimized. The new reflection lines - C-left and C-right - are made as wide as possible without getting blocked by the ESL panels, creating a reflected phantom image line which superimposes almost perfectly with the speaker phantom image line from the LP point of view.
 


Reflective and absorptive (or diffuser, if of proper design) panels from point of view of the LP.
 


Reflective panels, creating new reflection lines C-left and C-right, are placed as wide as possible without getting blocked by the ESL panels.
 


Reflective panels are aligned with laser and mirror so reflections C-left and C-right are directed at the LP. Their distance from the LP is carefully adjusted using overlaid impulse diagrams with Room EQ Wizard to ensure their path lengths match within 1/4 inch (approx. 20 uS).
 


Matching of the direct (A-left and A-right) and reflected (C-left and C-right) paths are matched to with 1/4 inch, 20 uS with impulse response diagrams. Path length matching requires a non-USB omni mic and a 2-channel audio interface so REW can be run with a loopback timing reference.


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## bkeeler10

Wayne, this is fascinating. Thanks for posting your results. You truly are an innovative thinker and experimenter in this area, at least in my experience. Pretty amazing that you were able to achieve the best you've ever heard in that room, considering the amount of time you've spent and the number of speakers you've set up and listened to in there. 

I also find it interesting how you can make the ESL sound almost horn-like in dynamic impact. That's one of those things that panels are not normally known for. :T


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## NBPk402

Thanks for the excellent write up Wayne. Did you by any chance re run Audyssey after the movement of the panels?


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## AudiocRaver

bkeeler10 said:


> Pretty amazing that you were able to achieve the best you've ever heard in that room, considering the amount of time you've spent and the number of speakers you've set up and listened to in there.


Thanks, Brian.

Our degree pf success came from a combination of factors: really getting to know the room and its speaker sweet spot - Sonnie's last 3 sets of speakers have all sat on that exact spot, unlimited time to make adjustments, changes made to the room over time for the sake of soundstage - stage and treatment modifications and eliminating the big gear rack from the front of the room, and gradually learning more about what to do to get there. Given all those factors, there are probably a number of speakers we have had in the room that might have delivered that kind of soundstage. I personally lean toward dipoles because the strength and directional nature of that rear wave gives you something specific to work with in constructing a soundstage.



> I also find it interesting how you can make the ESL sound almost horn-like in dynamic impact. That's one of those things that panels are not normally known for. :T


That was one of the surprises from a year or so ago. As near as I can tell, it is about getting the energy focused, directionally and in time, on the LP, which, when you think about it, is exactly what horns are doing anyway.


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## AudiocRaver

ellisr63 said:


> Thanks for the excellent write up Wayne. Did you by any chance re run Audyssey after the movement of the panels?


Yes, and I meant to add that to the writeup. I will do so.

That also explains why the initial delay is over 40 mS on the impulse response diagrams. Over 30 mS of that is processing time in the AVR.


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## 480dad

AudiocRaver said:


> That was one of the surprises from a year or so ago. As near as I can tell, it is about getting the energy focused, directionally and in time, on the LP, which, when you think about it, is exactly what horns are doing anyway.


As you know, this was precisely why I chose to move to the ESLs. To get horn-like directionality and the response and precision from electrostats. Your recommendations have served me well.

These diagrams are very helpful. Can you recap again distance between the ESLs and to the LP during your testing. And, if I remember right, you found a vertical sweet-spot somewhere around 31 inches from the floor. Did you adjust the panel vertical angle or keep it constant during this round of tweaks?

Also, is there a correllation of reflector angle to tow in angle? if angle of reflection equals angle of incidence, then I'm guessing you're atleast 5-10 degrees more than whatever toe in you've chosen?

Thanks and wonderful work (again). Tim


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## tonyvdb

Fantastic writeup Wayne :T

Do you think that this is something that would work with all speakers?


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## Lumen

:hail: Wayne, you've "exceeded expectations" once again. I can hardly wait to see what you're brewing next! Your overall philosophy of manipulating sound absorption, reflection, and diffusion in front of the listening position is of professional caliber. *Have you considered doing this for a living?* 

I have yet to solve all my soundstage problems; don't know that I ever will--at least until I become proficient with REW. But a lot of your experience is like looking in a mirror, and I'm just chomping at the bit to share some comments, so here goes (some of the quotes were rearranged for clarity, but content was not changed).



AudiocRaver said:


> I noticed that Sonnie had placed large diffuser panels under the movie screen on the left and right, as is commonly recommended. They were of the type of construction which ended up reflecting the majority of sound forward into the room, with much of those reflections going toward the LP.
> 
> I will go on record here as stating that this is NOT good for imaging. Apparently I am a lone voice in this regard. I recently had a discussion explaining this point with several other serious, experienced listeners and was unable to convince them of this, being counter to the accepted approach. Diffusion on the front wall is excellent for adding spaciousness to the room's sound, the reason it is recommended. But a design which reflects energy toward the LP, as Sonnie's diffuser was, and as most diffusers do, as far as I can tell, will have the effect of delivering energy from many points across the front wall to the LP. The result cannot help but be a softened image, as we heard in Sonnie's room at that time.
> .
> .
> .
> < snip >
> .
> .
> .
> Saturday, we started double-blind amplifier tests, and at this point the room arrangement changed somewhat. Diffuser panels were back at the front of the stage as planned to hide amplifiers under test, but there were also some sheets and blankets used to cover different areas of visibility, plus all of the amplifiers not being tested were placed in front of the stage with blankets covering them so we could not see which were there. The result of all this, as Dennis already mentioned in his comments, was that the sharp imaging and we had experienced on Friday was now somewhat cluttered and chaotic. It was quite distracting, but there was no quick way around it and we had to make progress, so we did not make a big deal of it. The lesson, of course, is that any objects in the front of the room are creating extra reflections and will disrupt the soundstage and imaging.


No you're not alone. It'll come across here as a "Me Too" knee jerk reaction, but I became a proponent of eliminating front-end reflections when I put my first big screen (refrigerator) TV between the speakers. Yikes! I later learned that glass surfaces anywhere in the room were bad, as were any objects between the LP and the speakers. And then when I first treated my room, I discovered through research and installation advice that "head-end ringing" was to be avoided at all costs. But it was a tradesecret for which they expected $$$ compensation. I believe your method(s) address this issue, and your thread takes the mystery out of it.

Here's how Art Noxon of ASC describes head-end ringing:
_"We do rooms all day, every day, all over the world, for twenty years, and the first reflections are not what we fix first. The first thing we attack is something we call “head-end ringing.” We shorten the vertical and lateral reverberation time in the bass by treating the space to the side of, and behind, the speakers. It’s one of our trade secrets. By cleaning up head-end ringing, we dramatically expose low-level detail in the midrange and treble. I agree that absorbing first reflections improves imaging, but without treating head-end ringing, there’s this slug of vertical and lateral shaking of air that oozes past the listener about a twentieth of a second after the direct signal and blurs musical detail and imaging. After we’ve addressed head-end ringing, then we control first reflections."_



AudiocRaver said:


> Thinking in terms of home listening rooms, the "barren front of room" method is not good for those who prioritize room decor very highly. Good luck selling the idea to the _significant other._


Yet another "Me Too!" And I'm blessed with a wife that gave up her living room for my system. But now that I stole an extra bedroom for the HT, I think I'm pushing the envelope. Maybe it's time to morph the two systems into one.



AudiocRaver said:


> One track which I had not listened to in that room before, but had relied upon as a test track Friday and Saturday, was the Nickel Creek song, _House of Tom Bombadil._ I noticed that the mandolin on the left and guitar on the right both seemed somewhat disembodied, the higher plucking sounds coming from close to the speakers and the lower range tones of the bodies of the instruments coming from closer to the center of the soundstage. This effect became very pronounced at the point in the song where a guitar solo starts in the high registers, progresses down to lower and lower notes, then goes back up to the high registers again. Through the solo, the lower tones of the guitar moved closer and closer to the center of the soundstage, then crept back out to the speaker again by the end of the solo. This occurred with both the Spatial M1 speakers and the MartinLogan ESL speakers.
> 
> With both of the speaker models being dipole designs, there is a lot of energy coming from the rear of the speaker and reflected off the front wall. The lower the frequency, the wider the dispersion of that rear wave, allowing the apparent reflection point off the front wall to move inward toward the center of the soundstage.
> 
> The remedy for this was to place absorptive panels under the movie screen left and right, which completely solved the problem. Back to the previous point on the construction of diffuser panels, a design which directed all the reflected energy away from the LP would have worked just fine instead of the absorptive panels. Remember also that at lower frequencies the smaller angles and surfaces of a diffuser tend to look like one big flat surface due to the longer wavelength. While I have not experimented with it to verify, it might be that the ideal front wall diffuser is absorptive at frequencies below 1 kHz or so, and reflective with angles away from the LP at frequencies above that.


Okay, now this is THE MOTHER OF ALL "Me Too's!" And me be looking in the mirror. Thank you, Wayne, for following up on this. I can't find the exact post, or am too lazy to try--you be the judge! My system reproduces the same anomaly during the opening guitar solo on the Eagles' _Hotel California_ song off of the "Hell Freezes Over" album. Higher notes stay on the speaker, but lower notes wander off toward the middle of the stage and back again. The notes are played so quickly that without listening closely, it can sound like two separate instruments. My speakers aren't dipole, but they do have a rear tweeter that's adjustable in level. Maybe your laser-aimed panel would help in my case. Would like to try, but need to know more about the panels. I don't expect an answer here, as my post has been a work-in-progress throughout the day; so someone may have already touched base on that. *If not, can you share specifics of the panels/diffusers you used? I think at one point, you mentioned using the back side?!* I must have misunderstood. Does GIK carry anything for this type of application?



AudiocRaver said:


> On the other hand, a diffuser which is constructed with angles so that all of the energy is deflected at angles away from the listening position, with no energy reflected directly at the LP, would be an excellent design for front of room. It would add spaciousness without softening the image at all. I have experimented with this in my own room and found it to be true, just as it was being confirmed in Sonnie's room.


On first read, another "Me Too!" Turns out not to be, so it's last in my list.
My panels absorb sound on their flat face, but diffuse it on their angled sides. The soundstage quality owes itself in part, to moving two such panels from the LP's sides to the front wall. It did sound better (not just different), but only slightly. FWIW, I never tried moving more of them to the front, because that would mean giving up 1st and 2nd reflection points. It may be worth forfeiting the 2nd points, but losing the 1st points would swamp any gains made treating the front wall IMO. In Mr. Noxon's opinion, it's the other way 'round. In any case, my panels are probably too narrow (physically) and too limited (spectrally) to be effective for midrange control. *Any tips on buying or building appropriate versions?*



AudiocRaver said:


> At this point, we discussed some of the experiments I had done with my own ESL speakers over the last year, and Sonnie was very willing to try them in his room. The first step was to widen the reflection points for the rear waves so that they came from almost the same listening angles as the front waves. This was done using the back sides of the diffuser panels, placed almost behind the ESL speakers as viewed from the LP. The angles of those reflective panels were carefully adjusted using laser and mirror so the rear wave from the ESL was directed straight to the LP. Distance, or path length, was carefully adjusted using impulse diagrams with REW so the left and right reflected waves arrived at the LP within about 20 microseconds of each other (1/4 in path length match). Path length matching requires a non-USB omni mic and a 2-channel audio interface so REW can be run with a loopback timing reference.


Way beyond my REW capabilities at the moment, but nice to know it's here for reference. KUDOS! :T


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## AudiocRaver

Some notes were added at the end of the article, covering setup dimensions, Audyssey/EQ, and reflective panel material.



480dad said:


> ...if I remember right, you found a vertical sweet-spot somewhere around 31 inches from the floor. Did you adjust the panel vertical angle or keep it constant during this round of tweaks?


We did not make any changes to the vertical angle. We were very happy with the "raw" sound and soundstage/imaging from the ESL. Plus the LP was far enough away from the speakers that normal head movement covered a very small angle and we experienced no shift in tonality, the main reason to pursue that sweet spot.



> Also, is there a correllation of reflector angle to tow in angle? if angle of reflection equals angle of incidence, then I'm guessing you're atleast 5-10 degrees more than whatever toe in you've chosen?


Not that I have found. There is still work to do in that area.


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## AudiocRaver

tonyvdb said:


> Fantastic writeup Wayne :T
> 
> Do you think that this is something that would work with all speakers?


Yes, in varying degrees. I am doing some work on that right now with speaker types I have available. It seems natural that more rear energy - dipoles - gives more soundstage enhancement. But I have heard dramatic improvement with regular tower speakers, too.

Horns, with their higher directivity, seem to give the least effect, but even with them there is significant soundstage improvement.


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## Lumen

BlueRockinLou said:


> ...And then when I first treated my room, I discovered through research and installation advice that "head-end ringing" was to be avoided at all costs. But it was a tradesecret for which they expected $$$ compensation. I believe your method(s) address this issue, and your thread takes the mystery out of it.
> 
> ...Here's how Art Noxon of ASC describes head-end ringing.


Now with a clear head this morning, I re-read my somewhat hurried post--and realized I incorrectly compared your method--which address midrange anomalies and higher. ASC's method addresses bass issues. Apologies. :R


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## AudiocRaver

BlueRockinLou said:


> No you're not alone. It'll come across here as a "Me Too" knee jerk reaction, but I became a proponent of eliminating front-end reflections when I put my first big screen (refrigerator) TV between the speakers. Yikes! I later learned that glass surfaces anywhere in the room were bad, as were any objects between the LP and the speakers. And then when I first treated my room, I discovered through research and installation advice that "head-end ringing" was to be avoided at all costs. But it was a tradesecret for which they expected $$$ compensation. I believe your method(s) address this issue, and your thread takes the mystery out of it.
> 
> Here's how Art Noxon of ASC describes head-end ringing:
> _"We do rooms all day, every day, all over the world, for twenty years, and the first reflections are not what we fix first. The first thing we attack is something we call “head-end ringing.” We shorten the vertical and lateral reverberation time in the bass by treating the space to the side of, and behind, the speakers. It’s one of our trade secrets. By cleaning up head-end ringing, we dramatically expose low-level detail in the midrange and treble. I agree that absorbing first reflections improves imaging, but without treating head-end ringing, there’s this slug of vertical and lateral shaking of air that oozes past the listener about a twentieth of a second after the direct signal and blurs musical detail and imaging. After we’ve addressed head-end ringing, then we control first reflections."_





BlueRockinLou said:


> Now with a clear head this morning, I re-read my somewhat hurried post--and realized I incorrectly compared your method--which address midrange anomalies and higher. ASC's method addresses bass issues. Apologies. :R


Not a biggie. The techniques actually dovetail nicely. I was already headed in the direction of LF absorption front-of-room, and reducing the LF ringing makes perfect sense and with a little care can be done at the same time with techniques I am suggesting. Thanks for mentioning it, we'll chalk it up to serendipity. I will certainly give credit to ASC for the idea.

Which leads to the kind of treatments to use. My experiments have been very willy-nilly, grab or stick together (Velcro, gaff tape, hot glue) whatever is nearby to discover what happens... I will soon be looking at specific types of panels & materials on the market or easy to construct that lend themselves to this work. The first solution I will be looking for is something that has LF absorption (implying thickness for one thing) and at MF and HF either diffuses ALL energy AWAY from the LP or absorbs (like the panels you mention using) the portion of energy that would otherwise reflect toward the LP. Easy!

Just how to prioritize placement of treatment material can be debated in different directions. First reflection off the side wall seems like top priority with first reflection of the rear wave off the front wall (the one from the "natural" reflection point which we are eliminating from the LP point of view, *B* in the diagram in the first post) being a close second. Second reflection off the sidewall would be next.

Reflections off the ceiling, with a flat ceiling, I do not have a problem with, because they are, in terms of listening angle, right in line with the direct wave from the speaker, so imaging is not pulled left or right. That reflection may be seen as a little on the early side for ideal, but is least destructive of any of the reflections we have talked about. Actually, it has the effect of hightening the soundstage, enhancing its 3D-ness, which is very cool. Carpeting or a throw rug usually takes care of floor reflection, which tends to be a little on the early side to not treat at all.

The backside of the panel we worked with was simply a matter of convenience. At home I have used unfinished wood for reflective surfaces. This is something to be experimented with more in the future. In my case, as with Sonnie's, the MartinLogan ESL is set up with very little toe-in, so the listening angle is quite a bit off-axis. That means some loss of high frequencies above about 2 kHz. The rear wave reflection off of a plain board ends up brightening up the soundstage quite a bit, so need for EQ of the high frequencies ends up being minimal.

There is still much to be learned in the area of ideal toe-in and listening angle, and brightness of the direct vs. brightness of the reflected wave and what works best, and how to support that with bare wood or fabric-covered wood or whatever. Having some high frequency loss due to the listening angle for the direct wave and a fairly bright reflected wave has the effect of creating a soundstage which stretches from the speakers back to the front wall and beyond, which has worked well in the rooms I have tried this in.


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## Lumen

AudiocRaver said:


> ....I will soon be looking at specific types of panels & materials on the market or easy to construct that lend themselves to this work. The first solution I will be looking for is something that has LF absorption (implying thickness for one thing) and at MF and HF either diffuses ALL energy AWAY from the LP or absorbs (like the panels you mention using) the portion of energy that would otherwise reflect toward the LP. Easy!


Hi Wayne. Any update. I'm sure you've had nothing but time to look into this! :bigsmile:


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## Blacklightning

> AudiocRaver said:
> 
> 
> 
> I have only heard a few examples of in/on-wall speakers in use, and have heard at best only mediocre soundstage development - decent width but imaging not great and no soundstage depth at all. If soundstage and imaging are a priority, I would recommend staying away from in/on-wall speakers.
> 
> Of course there are rooms and situations where they are necessary or are strongly preferred for aesthetic reasons. If that is the case, you might consider a design where the enclosure floats so it can be aimed for the purpose of finding the best imaging and clearest soundstage.
> 
> But it is the delayed reflections coming from the front of the room that give the soundstage its depth, and they do not exist with a normal in/on-wall design.
> 
> Another possibility is to create the equivalent of those delayed signals electronically. Another future project.....
> 
> 
> 
> 
> 
> 
> Blacklightning said:
> 
> 
> 
> Or two speaker sized metal sheets two feet from the wall on each side of the speaker sending sound back to the wall. The other side of the sheet could be absorbent material. :unbelievable::rubeyes:
> 
> Click to expand...
> 
> 
> 
> 
> AudiocRaver said:
> 
> 
> 
> Of course you are joking. But it is just the kind of crazy experiment I might try. You would not believe...
> 
> Think I will stick to the electronic version this time, the cleanup will be much simpler!:bigsmile:
> 
> Click to expand...
Click to expand...

Looks like I was not far off. I look forward to testing out your way... I am having trouble figuring it out. Any chance of adding real photos?


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## Talley

I'm not done with my stuff at all... built some panels and just have them laying around to listen to them. Still working on my details with what I'm doing. My room will be very uniquely done when complete though and will probably not pass anyone here approval since many go for "looks".

However I will say that any and all speakers will improve with diffusion along the front wall between the speakers. My setup will have some panels that I can place in front of the screen when listening to two channel music then I can put them out of the way for movie watching. Best of both worlds is really all I can come up with is movable stuff.

You can see me playing around with my room as it sits right now like this image. I'm really enjoying the sound of the poly diffusers and the fact they are very simplistic to build, are very lightweight I will end up with these on the ceiling.

It's unbelievable the sound changes that are made when placed in the center area between the speakers. Really hides the speakers and creates depth in the sound.


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## AudiocRaver

Blacklightning said:


> Looks like I was not far off. I look forward to testing out your way... I am having trouble figuring it out. Any chance of adding real photos?


The diagrams in the first post are all I have for now. When I update the speaker setup guide, there will be more, but I'm not sure how soon that twill be.:huh:



> I'm not done with my stuff at all... built some panels and just have them laying around to listen to them. Still working on my details with what I'm doing. My room will be very uniquely done when complete though and will probably not pass anyone here approval since many go for "looks".
> 
> However I will say that any and all speakers will improve with diffusion along the front wall between the speakers. My setup will have some panels that I can place in front of the screen when listening to two channel music then I can put them out of the way for movie watching. Best of both worlds is really all I can come up with is movable stuff.
> 
> You can see me playing around with my room as it sits right now like this image. I'm really enjoying the sound of the poly diffusers and the fact they are very simplistic to build, are very lightweight I will end up with these on the ceiling.
> 
> It's unbelievable the sound changes that are made when placed in the center area between the speakers. Really hides the speakers and creates depth in the sound.





Lumen said:


> Hi Wayne. Any update. I'm sure you've had nothing but time to look into this! :bigsmile:


My question would be what does it do to the imaging? Any arrangement I have tried with diffusion on the front wall or anywhere away from the speaker direction, while it added spaciousness, it also made the imaging softer *if it reflects directly at the listener.* That was the first thing noticed in Sonnie's room. If the diffuser is physically shaped so all sound is diffused in other directions, reflecting off walls and/or ceiling and getting a bunch more delay before reaching the listener, then it is interpreted differently, adds even nicer spaciousness, and does not mess up imaging at all. Finding material to do this has proved difficult. The panels which are made up of 3" pyramids looks right, but is mainly absorptive. I have considered taking a few of those and spray-painting them to make them more reflective, interspersing them with unpainted ones. It could get ugly, literally. That is my best idea so far. I may try it soon.


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## Lumen

tonyvdb said:


> Do you think that this is something that would work with all speakers?





AudiocRaver said:


> Yes, in varying degrees. I am doing some work on that right now with speaker types I have available. It seems natural that more rear energy - dipoles - gives more soundstage enhancement. But I have heard dramatic improvement with regular tower speakers, too.


While a rear-firing tweeter matches neither the spectral range nor the radiating surface area of the ESL, it can have a significant impact on perceived ambience. My rear-firing tweets have been disabled for quite some time, because I feel they tend to confuse the performance with extraneous, distracting sounds. But that only manifested itself after I installed and tweaked my traps/diffusers. Re-tuning them with rear-reflection in mind may very well produce superior results. If memory serves, the rear tweeters on my Salons are adjustable in two -0.5dB increments (0dB, -0.5dB, and -1.0dB). Does it make sense to ask which level of attenuation you would choose if any and why? Can you see an advantage to using that level adjustment to help manipulate any parameters affecting SS&I?




AudiocRaver said:


> Reflections off the ceiling, with a flat ceiling, I do not have a problem with, because they are, in terms of listening angle, right in line with the direct wave from the speaker, so imaging is not pulled left or right. That reflection may be seen as a little on the early side for ideal, but is least destructive of any of the reflections we have talked about. Actually, it has the effect of hightening the soundstage, enhancing its 3D-ness, which is very cool. Carpeting or a throw rug usually takes care of floor reflection, which tends to be a little on the early side to not treat at all.


This makes me want to experiment with my ceiling traps. I originally installed them to help tame ceiling-to-floor room modes, and to eliminate the ceiling's first reflection point. Now I wonder if I inadvertently sabotaged the height element of my stage - something I've struggled for. Do you have any tips on _increasing_ perceived soundstage height? Do you mean to infer that ceiling diffusers would prove beneficial in that regard?


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## AudiocRaver

Lumen said:


> While a rear-firing tweeter matches neither the spectral range nor the radiating surface area of the ESL, it can have a significant impact on perceived ambience. My rear-firing tweets have been disabled for quite some time, because I feel they tend to confuse the performance with extraneous, distracting sounds. But that only manifested itself after I installed and tweaked my traps/diffusers. Re-tuning them with rear-reflection in mind may very well produce superior results. If memory serves, the rear tweeters on my Salons are adjustable in two -0.5dB increments (0dB, -0.5dB, and -1.0dB). Does it make sense to ask which level of attenuation you would choose if any and why? Can you see an advantage to using that level adjustment to help manipulate any parameters affecting SS&I?


AudioKinesis is a company that, at the last couple of RMAF events, has had speakers with either rear-firing drivers or separate units altogether firing backwards and upwards specifically to add spaciousness to the sound. They were very effective. There are also Omni models by Axiom with rear-firing mids and tweeters, like the LFR880 that I reviewed last year, that do this well. You mention rear-firing tweeters, and that alone, without support through the midrange down to a couple hundred Hz, would seem to simply add harshness, or shall we call it harsciousness. The LFR880 has carefully tailored the frequency response via DSP for the rear drivers, which include two mids and two tweeters, so it is a well-tuned design, with an omni sound power goal, and an adjustment for the level of the rear firing signal on the DSP. As far as the amount of that rear-firing signal, the effect is so subjective that it will be different in every room with every speaker and every speaker setup combination.



> This makes me want to experiment with my ceiling traps. I originally installed them to help tame ceiling-to-floor room modes, and to eliminate the ceiling's first reflection point. Now I wonder if I inadvertently sabotaged the height element of my stage - something I've struggled for. Do you have any tips on _increasing_ perceived soundstage height? Do you mean to infer that ceiling diffusers would prove beneficial in that regard?


I have played with this specifically in only one room, an attic room with a low ceiling where the listener did not want any treatment on the ceiling. I was experimented anyway just to see what the result might be, and found that leaving the ceiling reflection completely untreated added a touch of spaciousness without sacrifice to the imaging or soundstage, and seemed to enhance the height of soundstage just a little bit. I have almost no data to work with for making any kind of specific recommendation. Even with dipoles like the Martin Logan ESL, height of soundstage is very noticeable simply from the design of the speaker itself with the lower mids coming mainly from the bottom and all the highs coming from ear level. There are sounds that I hear clear up at the ceiling level sometimes.

Diffusers on the ceiling? If there is a principle in all of this, it is that if one is working with a reflection that is constructive to imaging and soundstage, then coherence is key and one should not diffuse it. Experimentation has confirmed this. If one is working with reflections that are intended for spaciousness only, they should be directed away from the listener and diffusion is a good thing.


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## Lumen

AudiocRaver said:


> As far as the amount of that rear-firing signal, the effect is so subjective that it will be different in every room with every speaker and every speaker setup combination.


You can say that again. And nobody needs to tell you how quickly an experiment can escalate into unmanageable proportions. For instance: If we wanted to optimize SS&I by manipulating three variables (LP and speaker location/toe-in), how many combinations would need to be auditioned? Well, we're interested in three groups of varying elements each whose order is unimportant. That defines a mathematical combination expressed as 
n! / [ k! (n-k)! ] ... for k <= n ; where n = number of elements, and k = number of groups

Returning to our example, we'll assume:
there are 3 decent listening positions
acceptable speaker locations have been limited to 9 discreet coordinates (four to either side of centerline through tweeter axis)
speaker toe-in has, say, 10 discrete angles from 0° to 45° (i.e. 5° increments)
Plugging k=2 and n=(3+9+10)=22 into the formula yields a total of 1540 combinations! Unmanageable.

Instead, say we assume we've already found the optimal location of the speakers and LP, and now merely want to fine tune toe-in and rear tweeter level (three distinct level settings). Plugging k=2 and n=(3+10)=13 still yields a high number of combinations at 78. Clearly, that many trials would tax the acoustic memory of even the most talented of golden ears. I am impressed with your ability to converge on a "solution" (defined here as your personal preferences related to psychoacoustic phenomena such as stage depth) so quickly. No doubt your experience with numerous rooms and systems plays a role, as does your expertise with experimental methodology and repetition. I imagine the process of elimination helps guide tuning for SS&I. For example: starting with speakers 6 feet apart, first move them away from each other in 0.5 inch increments. When the sound gets "worse", return to the last known position. Then try locations 0.5/2=0.25 inch to either side of that. Repeat until no discernable difference can be heard.


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## AudiocRaver

I had not really thought about it much. It is interesting how the human mind can learn to quickly chunk down an exercise into big pieces that would seem to require a lot of tedium on the surface. Once you have done this with a bunch of different speakers, especially in one room where you have a lot of experience, you tend to grab and make big movements, quick changes, and get there pretty fast.

It is not unlike an outfielder being able to tell from the first second of the flight of a pop fly about where he needs to go to be under it when it comes down. I often marvel at how the brain is able to make those kinds of calculations, based partly on experience and partly on some really advanced projection/calculation abilities buried in the brain cells somewhere. Anymore, if we don't have a speaker into a pretty good position within four or five moves, we almost automatically dub it a “problem” speaker, then we switch to a more tedious mode, as you suggest.


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