Placement options – Impacts of location, orientation and treatments

[Rich]

Which diffusors did you test in your setup?

They were the RPG Hemiffusers. Here is a link:

http://www.rpginc.com/products/hemiffusor/index.htm

I actually bought these for placement behind the rear speakers for surround field diffusion, but figured I would test them behind the front speakers just to see the different effects of diffusion vs. flat wall vs. absorption. I was expecting an improvement with diffusion and was surprised to find it as bad or worse than flat wall.

Probably RPG's abfuser would be better for placement behind the panels, because it provides absorption and diffusion. I think the Real Traps diffusors will probably work great as well for the same reason.

 

[DTB300]

With a Dipole speaker, not only is the placement into the room critical, but what’s behind (and to the sides) is almost as important to the sound you get at the listening position.

So even if you are limited as to where in the room the speakers can go, you can effect substantial changes to the sound by treating the surfaces behind and to the sides of the speakers.

This is exactly my problem in my room. VERY limited in regards to placement of speakers and equipment. So with much experimentation using tilt, toe-in, bass trap and first reflection treatments, I have been able to get some really good results. So for some of you where placement is an issue, do not get discouraged, as you can still get some great improvements.

BTW, Great post Jon

 

[benleeys]

Jon,

Thanks for the very interesting and informative lecture. Just wondering what the situation would be like with an absorbtive rear wall, like a heavy curtain or something.

 

[Bernard]

.............With a Dipole speaker, not only is the placement into the room critical, but what’s behind (and to the sides) is almost as important to the sound you get at the listening position............

I thought that with a dipole the sides were not quite as important as the back; note: I am not saying the sides have negligible effect.

 

[DTB300]

Thanks for the very interesting and informative lecture. Just wondering what the situation would be like with an absorptive rear wall, like a heavy curtain or something.

I have bookcases sitting 4ft behind my seating position. Using GIK 244 panels (3 of them) in front of the bookcases really helped my room response and overall sound. Each room is different and each person has different tastes, so trying out absorption and diffusion behind should be done to see which is the best solution.

I had thought I read that diffusion behind the seated position is only beneficial when seated further away from the rear boundary.

 

[David Matz]

I have some RealTraps diffusers (which also do absorption) on their way. I will update this thread when I get them..

JonFo, thanks for posting this great information - the charts speak for themselves. Just out of curiosity, why did you settle on Real Traps? Are they significantly better than their competitors - ASC, echobusters, etc.? Also, how many did you order, and where are your placement priorities? Stereophile seems to think highly of their new product, Mondotraps. Are there any objective tests comparing the products from the different companies?

Also, have you heard anything about golden acoustics? http://www.goldenacoustics.com/index.html

They are supposed to be a "revolutionary" product that uses gypsum. One guy even made the claim to me that by using their product, the limited sweet spot of the Logans can be greatly increased, and one could have more uniform sound throughout the entire room. A high end store in Chicago just bought $40k of their "deluxe" panels, and it does sound good! (The rest of their system is also very expensive - Vivid driven by Luxman).

Here's their claim:

Our Tuning Panel Systems(tm) work by preventing both modal and reflective distortion in any space, and by creating linear decay across the entire audible frequency spectrum. They accomplish this by naturally redirecting and scattering the sound waves which hit them without distorting those waves (unlike the distortions created by conventional room surfaces, absorption, and so-called diffusion products). Each panel is made from ultra-high density polymerized gypsum with a working mass density greater than 4 pounds per square foot so that virtually all of the sonic wave energy to 100dB that hits them is redirected back into the room (we have an elite series at 6 pounds per square foot which redirects to pressure levels to 120dB).

Our Tuning Panels do not distort because of the unique conically-based shapes which populate them. Unlike all other shapes, a cone's radius is constantly changing with respect to its height so the cone reflects sound waves in a non-distorting way (i.e., a non-linear and non-uniform way). Picture water waves on a beach hitting flat rocks, hemispherical rocks, and conical rocks: in the first two cases, the energy undergoes far more compression, acceleration, and chaos than in the case of the cone.

Each of our conically-based shapes is called a Tricon(tm) because it's a cone that's been halved, then one of the halves has again been halved into quarters of the original cone, and the two quarter pieces are then rotated and restored to the first half. This creates a cone with an edge that assists in controlling the redirection by preventing vortexing of the wave. The heights and spacing of the various cones are derived mathematically as fractals using the golden ratio and Fibbonacci series that are prevalent in nature (e.g., pine cones, pineapples, nautilus shells, etc.). Our technlolgy is the result of 8 years of work, following over two decades of work in high definition recording and development of high definition microphone technology by our founder.

Although a single panel will begin clarifying any area, multiple panels strategically placed will work systemically to balance and clarify large regions and entire rooms. The result is unprecedented clarity without deadness, or liveliness without distortion. There is no adverse affect to a few panels, and after approximately 20% of the total area of the room's walls plus ceiling are covered, the acoustics are so beautifully rich and pristine, and there is no discernable further improvement. Our 20% rooms are the finest sounding and most viscerally comfortable in the world. Depending on the room, beginnning around 12% coverage, spatiality and uniformity throughout the room are greatly improved (the entire room approaches becoming a "sweet spot"), and a perceived immersion in a rich, smooth sonic field takes place. Because our science is true and repeatable, we offer a money-back guarantee depending on the room and the Tuning level.


Just curious what your thoughts are.

Thanks,
David

 

[Joey_V]

They are supposed to be a "revolutionary" product that uses gypsum. One guy even made the claim to me that by using their product, the limited sweet spot of the Logans can be greatly increased, and one could have more uniform sound throughout the entire room. A high end store in Chicago just bought $40k of their "deluxe" panels, and it does sound good! (The rest of their system is also very expensive - Vivid driven by Luxman).

Thanks,
David

David,

This is OT, but I can guess what store you're describing there. Glenn Poor. I listened to their Vivid speakers and the Luxman, it's a real good combination. Not much gripe about them. I think they were actually a little more resolute than my Summits, albeit not as coherent.

 

[Sasha]

I have tried both absorption and diffusion behind the speakers just yesterday. Absorption killed a little bit of joy to the music, it sounded 'more informal', but diffusion helped too since the sound reflected was a bit harsh. That is logical, since curved panel is projecting wider image onto the narrow space on the wall which is reflected as it is. I guess 'abfusors' work well, but since we don't have that products over here, I will probably make some kind of diffuser out of heavy foam and maybe paint over it. I think the combination of the two is the thing we need for our panels

 

[Tj Bassi]

Great thread, Jon! I hope it keeps going....

Tj

 

[JonFo]

Jonfo,
I'm glad you are posting all of this information, nothing like a free lesson in acoustics from the resident expert. I hope to post some of my own thoughts/observations very soon from the suggestions you gave me in my room response thread.

One question: I noticed that your mic is pointing down. Is this the typical postion for mic measurements? I questioned some of the guys on HomeTheaterShack about my Radio Shack SPL meter and got the response that the accepted position is at a 45 deg angle (understanding that the SPL meter is probably much more directional than a mic). I'm comtemplating purchasing a Behringer ECM8000 mic and a Xenyx 502 or 802 mixer/mic pre amp to get better high frequecy measurements.

Kruppy, glad you are benefiting, with your pursuit, I figured this would help. I look forward to your results.

The mic is actually pointing straight up (cable is coming out the bottom). As this is the accepted configuration for using calibrated mics to measure acoustics.

For the SPL meters, the 45 degree hand-held variant is the right way to measure SPL.

The ECM8K and the pre you mention will do fine with REW.

I just got an M-Audio FireWire 410, which does everything I need for mesurements (including phanthom power for the mic), as well as being a great 8channel analog audio output card, and it has bit accurate (ASIO drivers) SPDIF I/O as well. So it's a really nice all-in one, and can be used with laptops as many of them have a IEEE-1394 (firewire/iLink) interface on them these days.

 

[JonFo]

They were the RPG Hemiffusers. Here is a link:

http://www.rpginc.com/products/hemiffusor/index.htm

I actually bought these for placement behind the rear speakers for surround field diffusion, but figured I would test them behind the front speakers just to see the different effects of diffusion vs. flat wall vs. absorption. I was expecting an improvement with diffusion and was surprised to find it as bad or worse than flat wall.

Probably RPG's abfuser would be better for placement behind the panels, because it provides absorption and diffusion. I think the Real Traps diffusors will probably work great as well for the same reason.

Rich, yes, 3D diffusion behind the diploes doesn't really work too well. One of the reasons is that it immediately engages floor and ceiling (especially), as it radiates diffused energy in all directions. The additional reflections off the ceiling add additional energy in the <20ms range to the main signal from the panel, thus causing even more comb filtering.

3D diffusion works well on the wall between the rear speakers (as can be seen in the pics of my system below) Those are RPG Skylines, and they take the energy that has traveled 24’ or so from the fronts and diffuses it so the listener get a greater sense of space and not a strong rear-wall reflection (although those reflections are >20ms, and therefore not perceived as part of the ‘main’ impulse.

Using 2D diffusers, like the Auralex you see behind those Sequels, work really well for the rear channels. But as noted in other posts above, probably not so good for fronts. I’d agree the RPG Abfusor or the RealTraps diffuser (which is a combo of diffusion grating over an absorber) should work really well.

The benefit of 2D diffusion is it reduces the intensity of the primary solid surface reflection by re-radiating much of the energy in a horizontal arc. With none of the energy arriving at ceiling or floor, the only thing to worry about is the side-wall reflections and their relative arrival times.

For instance, I recall recommending for Kruppy that he use an RT Difusor behind his SL3’s coupled with a MiniTrap along the side wall. I guess the questions now is: should the side wall mini trap be an HF variant or the normal one (which is reflective in the highs). That might a 'season to taste' item.

 

[Audioseduction]

Jonathan,

Thanks for the data you’ve collected. It actually reflects my experience in my den with the Odyssey’s. I appreciate you taking the time applying your knowledge and tools in presenting the information so we all can gain a better understanding of sound reproduction. I must say this forum is the Best with people like your self being part of it. Peace! :rocker:

 

[benleeys]

I have bookcases sitting 4ft behind my seating position. Using GIK 244 panels (3 of them) in front of the bookcases really helped my room response and overall sound. Each room is different and each person has different tastes, so trying out absorption and diffusion behind should be done to see which is the best solution.

I had thought I read that diffusion behind the seated position is only beneficial when seated further away from the rear boundary.

Jon,

I am sorry. In my hurry I missed some words in my post. What I really meant was "behind the speakers", not behind the listener. I was wondering what your charts would look like with an absorbtive wall in front since there would be little or no reflection at all from the front wall. Wouldn't that be ideal?

 

[Kaboomnash]

I am still experimenting and tweaking. Added spike cups. I use the flashlight method to get my toe in. Might try raising the rear of the Vantages a tad. I have searched for nice wall absorbtion treatments online, rather expensive. I might end up DIY'in them. I did something similiar behind my dartboard.

Lee

 

[JonFo]

JonFo, thanks for posting this great information - the charts speak for themselves. Just out of curiosity, why did you settle on Real Traps? Are they significantly better than their competitors - ASC, echobusters, etc.? Also, how many did you order, and where are your placement priorities? Stereophile seems to think highly of their new product, Mondotraps. Are there any objective tests comparing the products from the different companies?

Also, have you heard anything about golden acoustics? http://www.goldenacoustics.com/index.html

They are supposed to be a "revolutionary" product that uses gypsum. One guy even made the claim to me that by using their product, the limited sweet spot of the Logans can be greatly increased, and one could have more uniform sound throughout the entire room. A high end store in Chicago just bought $40k of their "deluxe" panels, and it does sound good! (The rest of their system is also very expensive - Vivid driven by Luxman).
...

Just curious what your thoughts are.

Thanks,
David

David, thank for sharing the info on Golden, they have a very intriguing product line. I definitely dig the look of their panels (see pic), as I love fractals.
The one thing I’d like to see is the independent testing and analysis results of their products. So far, none of that is posted.

Also, I'm somewhat suspect of claims to be able to ‘diffuse’ low-frequency (below 100hz) as those wavelengths are huge (measured in feet) and in small rooms, are mostly pressure artifacts (which is why one needs diaphragmatic absorbers to deal with them), not waves that can be reflected. But then, my knowledge in this field is entry-level at best.

I can definitely see how they could be effective at all other frequencies though. And by recommending fairly large surface area covering, they are bound to substantially change the higher-frequency modal reflections.
The positive about using diffusion products over just throwing absorbers everywhere is that we can manage to preserve spatial imaging, and just as important, the right balance of energy in the room to maintain a uniform frequency response.

However, the science of deciding where to put the diffusion is tricky, and complicated even further by the dipole nature of our speakers. Most of the research and literature on these topics uses point-source monopoles for the sound generators. And as we see in the graphs I published earlier, diploes can have very different impulse responses depending on placement and wall (the ones behind/side of the speaker) treatments.

As for what I’ve ordered: I’m going for three RealTraps diffusers (which are absorptive as well), two will replace the Auralex diffusers behind the Sequels. The other goes behind the Center (which also has Auralex diffuser+ and HF absorber blanket over it) .
There are two additional HF MiniTraps to go on the wall behind the Monoliths.
The LENRD traps in the rear corners will be replaced by 4x MondoTraps.

I’ll be adding two to four more Mondo traps hanging from the ceiling at strategic high-pressure bass modes in the room. But this might get scratched for a room-long custom DIY ceiling / side wall trap Triangular profile, offset form the boundary by a few inches. But calculating how to make an effective diaphragmatic absorber oneself is daunting (yes, even for me )

Once all the above is in place, I’ll see how that works and go from there if needed with more diffusion and or absorption.

One of the things I do want is a half-way decent aesthetic balance as well, so side wall absorbers will be DIY with my artiste wife doing the look and feel. Oh, you guys will LOVE the special ML centric touch we’ll give those Just wait and see.

 

[JonFo]

Jon,

I am sorry. In my hurry I missed some words in my post. What I really meant was "behind the speakers", not behind the listener. I was wondering what your charts would look like with an absorbtive wall in front since there would be little or no reflection at all from the front wall. Wouldn't that be ideal?

Ben,

The comparison in the first few posts go between untreated (bare wall) and treated. The treated surface is an RPG product that is absorbent in the mid and high frequencies.

So that's what the frequency and impulses will look like. As you can see, it's much improved over a bare wall.

Again, the toe-in will dramatically affect how much this comes in to play as well. So these two interact.

 

[DTB300]

The one thing I’d like to see is the independent testing and analysis results of their products. So far, none of that is posted.

I see their site says "they are coming soon" - but how soon??? Always makes me skeptical when companies do not show their data results for acoustical treatments. Hopefully they will post their data to show the real benefits of their devices.

Also, I'm somewhat suspect of claims to be able to ‘diffuse’ low-frequency (below 100hz) as those wavelengths are huge (measured in feet) and in small rooms, are mostly pressure artifacts (which is why one needs diaphragmatic absorbers to deal with them), not waves that can be reflected. But then, my knowledge in this field is entry-level at best.

I would agree with you here on both points of diffusing low frequencies (always read what you stated about the large wave sizes and diffusers not being large enough to deal with them - that is diffuser sizes we are familiar with ) and being a newbie in this room acoustics stuff. But like you have experienced and other should too, treating our rooms is a great benefit.

I can definitely see how they could be effective at all other frequencies though. And by recommending fairly large surface area covering, they are bound to substantially change the higher-frequency modal reflections. The positive about using diffusion products over just throwing absorbers everywhere is that we can manage to preserve spatial imaging, and just as important, the right balance of energy in the room to maintain a uniform frequency response.

While I would agree that both products are the usual way to go, but don't you think that each room is different hence there is no real "best way"? Going through some trial and error with both products in ones room, and then listening and/or testing will show the best results. Yes?? No???

However, the science of deciding where to put the diffusion is tricky, and complicated even further by the dipole nature of our speakers. Most of the research and literature on these topics uses point-source monopoles for the sound generators. And as we see in the graphs I published earlier, diploes can have very different impulse responses depending on placement and wall (the ones behind/side of the speaker) treatments.

Agree. When talking with people in the know and you spurt out the word Electrostatics, they usually come back and state their experience is very limited with them and their products. Have you considered sharing your charts and graphs with people like Ethan to help him sell his products to other ML people - then sign the contract for your percentage of the profits!!! Seriously...I do think they would be very happy for the information on planar speakers and the results of acoustical treatments with them.

As for what I’ve ordered: I’m going for three RealTraps diffusers (which are absorptive as well), two will replace the Auralex diffusers behind the Sequels. The other goes behind the Center (which also has Auralex diffuser+ and HF absorber blanket over it) . There are two additional HF MiniTraps to go on the wall behind the Monoliths. The LENRD traps in the rear corners will be replaced by 4x MondoTraps.

I suspect you will hear a great improvement in your room when switching over from the stated products to the Real Traps products. The change from the LENRD's to the Mondo's will really help out the low end. I used the GIK to replace some LENRD's and the change was really nice.

Please make sure to get back with all of us on the changes you hear. Again I suspect that it will be very positive.

One of the things I do want is a half-way decent aesthetic balance as well, so side wall absorbers will be DIY with my artiste wife doing the look and feel. Oh, you guys will LOVE the special ML centric touch we’ll give those Just wait and see.

The products from Real Traps and GIK really look nice and do not give our rooms that recording studio look. Considering most of our rooms double as living spaces, this is a real plus.

 

[Rich]

As for what I’ve ordered: I’m going for three RealTraps diffusers (which are absorptive as well), two will replace the Auralex diffusers behind the Sequels. The other goes behind the Center (which also has Auralex diffuser+ and HF absorber blanket over it) .
There are two additional HF MiniTraps to go on the wall behind the Monoliths.

Jonathan, please do a test for me when you get your products in and start placing them. Please do a comparison between placing just the two HF mini traps behind your monoliths and then place the real traps diffusers in front of the HF mini traps (still behind the monoliths). I am have a theory that this would provide some ambiance by diffusing some of the higher frequencies of the rear wave, while providing even greater absorption of the mid and lower bass frequencies. Or just a comparison between the HF mini trap vs. the diffuser alone behind the monoliths would be great. For these tests, I am primarily interested in two-channel sound and imaging. Depending on your results, I may decide to purchase a couple of those diffusers as well. Thanks so much.

 

[Kruppy]

Jonathan,
Can you please post the manufacturer and name of the diffusers you used for your measurements in the first couple of posts. The white one looks like an Auralex MetroFusor. The darker/black one I can seem to place, looks like an Auralex product.

Right now I'm looking for a combo diffuser/absorber but I don't see anything that is more my (insert deep voice) "budgetary style".....specially if this is something that is experimental/trial and error and may not be permanent.

 

[benleeys]

Ben,

The comparison in the first few posts go between untreated (bare wall) and treated. The treated surface is an RPG product that is absorbent in the mid and high frequencies.

So that's what the frequency and impulses will look like. As you can see, it's much improved over a bare wall.

Again, the toe-in will dramatically affect how much this comes in to play as well. So these two interact.

Jon,

I thought you would say that. Unfortunately, my experience with heavy curtains covering the wall behind my Summits was a sonic disaster. Vocals sounded very much like the singer had a bad cold. Push the curtains aside and the cold disappeared. I wish I have the facility to take measurements like you do to find out the reason why. Obviously heavy curtains was the wrong idea for an absorbent.