Best Acoustic Products for First Reflection Points

Ron Resnick

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What is your recommendation for acoustic treatment products to absorb or diffuse the sound from the loudspeakers hitting the first reflection points?

ASC, for example, makes sound-absorbing rectangles, around 1" to 3" thick, that can be mounted on the wall or just leaned against a wall at the points of the first reflection.

RPG has a bewildering array of products. What is the best RPG product for absorption and for diffusion at the first reflection points? Abfusor? BAD Panel? Absorbor? Broadsorbor? Diffractal? Diviewsor? Modfractal? Modfusor? Omniffusor? Skyline?

What about the Vicoustic Multifusor Wood 64 diffusor? How does this product compare to the RPG Skyline?

Do any products combine characteristics of absorption with characteristics of diffusion?

What acoustic product do you use at the first reflection points in your listening room?
 

microstrip

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Ron,

IMHO by far RPG- it is what I have in my room. They are the only products I know that supply full and complete technical information. However they are more expensive than most. If you get someone with good experience you trust to advise you SMT is also known for great sounding rooms.

You traveled a lot listening to equipment and systems - did you prefer the acoustics of any of the rooms you visited?

BTW, all diffusors are simultaneously absorbers. However the ratios between diffused and scattered sound are different between them.
 

Steve Williams

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Ron,

IMHO by far RPG- it is what I have in my room. They are the only products I know that supply full and complete technical information. However they are more expensive than most. If you get someone with good experience you trust SMT is also known for great sounding rooms.

You traveled a lot listening to equipment and systems - did you prefer the acoustics of any of the rooms you visited?

I agree.

SMT is very good but TBH in a room fully treated with SMT I get dizzy looking at their stuff on walls and ceilings.
 

microstrip

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(...) SMT is very good but TBH in a room fully treated with SMT I get dizzy looking at their stuff on walls and ceilings.

+1!
My RPG's are hidden behind acoustically transparent curtains.
 

Ron Resnick

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Thank you, microstrip! How does the RPG Diffractal compare to the RPG BAD Panel (which, I assume, does more absorbing than the Diffractal) or the RPG Abfusor for dealing with first reflections?

Does the answer depend in any way on the distance of the speakers to the side walls?

Actually I am sure the distance between the speakers and the side walls is very material to the decision of which diffusor or diffusor/absorber product to use.
 

microstrip

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Thank you, microstrip! How does the RPG Diffractal compare to the RPG BAD Panel (which, I assume, does more absorbing than the Diffractal) and to the Vicoustic Multifusor Wood 64 diffusor?

The BAD panel absorbs significantly, particularly at the higher frequencies, and has a cutoff around 800 Hz - it is often used for speech.

Vicoustic products (a very successful brand manufactured around 200 miles from me ...) represent great value for money, but the Multifusor Wood 64 looks like a well built common QRD 2D diffuser and they do not supply measurements of diffusion.
 

DaveC

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A horn... ;)
 

Ron Resnick

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The BAD panel absorbs significantly, particularly at the higher frequencies, and has a cutoff around 800 Hz - it is often used for speech.

Vicoustic products (a very successful brand manufactured around 200 miles from me ...) represent great value for money, but the Multifusor Wood 64 looks like a well built common QRD 2D diffuser and they do not supply measurements of diffusion.

Okay -- interesting.

Are you familiar with the RPG Abfusor (versus the Diffractal)?
 

Ron Resnick

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It looks likes Andy Payor uses RPG Diffractals between the speakers and on the sidewalls towards the front of the room and RPG BAD Panels at his first reflection points:



image.jpg
 

microstrip

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Okay -- interesting.

Are you familiar with the RPG Abfusor (versus the Diffractal)?

Yes, I also had a few Abfusor's in the front wall, close to the corners. They have complete absorption - once I built a box with 5 panels (they are 2'x4') to measure a few tweeters and for fun I entered my head in it. I almost got nausea - the complete absence of noise was really un-natural!

With the Soundlab's I needed to absorb some of the back radiation - the full range panel emits a lot of energy towards the front wall.

Mark Levinson (and now Audio Research in their listening rooms) used to put the Abfusors in the center of the front wall and the Difractals/QRD 734's in the lateral positions of the wall. Keith Yates "A matter of diffusion" is always a mandatory and great reading about these subjects : http://keithyates.com/a-matter-of-diffusion/
 

Folsom

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SMT would be my first product to try. But I wouldn't line the room, like Steve is talking about. I don't think lining the room would give Ron what he's after anyways.
 

Mike Lavigne

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I have a completely different take on this question.

there are multiple cases to consider. first is driver type. obviously dipoles and horns interact differently with side walls and ceilings than cones.

I think for Ron's question we are speaking about cones mostly.

next is local and global. local is where there is relatively close distance between the speaker and wall, global is where the distance from speaker to wall is farther. and the actual issue is the reflection time (from driver, off the wall, and then to the ear, compared to the direct sound) and whether that reflection will be considered a smear or separate from a smear. this difference will change the type of treatment you choose. the local needs a more aggressive approach with possibly some absorption too. global might then be better with less aggressive treatment to retain more energy.

then there is the issue of speaker cabinet<->side wall resonance. your bass towers will have close proximity with the sidewall and there will be resonance between that sidewall and the bass tower cabinet which will need treatment independent from the 1st reflection treatment. sound bouncing from the cabinet to a flat wall surface and back again; creating distortion. this situation likely needs some sort of aggressive diffusion to break up that resonance.

lastly there is the balance between diffusion and absorption on the sidewall, and the balance between diffusion and just surface texture. surface texture will knock down reflective hash without changing tonality. I use cloth thumbtacked to walls as surface texture. it can be particular paint, or wall paper. I have built in diffusion in my room, and found I needed to treat the surfaces of that diffusion. eventually I had to place a towel over the meter bridge on my Studer A-820. I put cloth treatments on the ceiling 6-7 feet behind my listening position.

it all matters.

until you start to control the worst of your 'wall related issues', you won't even know about the next level of issues (that 1st refection hash covers the second reflection issues). and until you fix those, the deeper ones are not evident, and so on, and so on, and so on. like doors that get revealed as doors, once you remove the wall you didn't know was there. and in my case I needed a stack of three RPG Skylines in the center wall behind the speakers to begin with for proper center focus, but after I properly controlled first reflections, that Skyline Stack became a detriment messing up center focus, so I got rid of it. turned out it had been a band aid on a larger problem. so progress is not always linear.

and once the first reflection issues are somewhat treated, you need to keep going into places that your intuition tells you are not a factor. forget logic, keep chasing the reference in your head until you do things that your ears tell you don't matter. ignore your eyes and brain. they are not helpful.......as you peel layer after layer of the onion. big speakers, lots of driver surface, lots of energy, problems where you least expect it.

until you get the room controlled, speaker set-up will be provisional. I was in my room for 10 years when my speaker designer visited and fine tuned everything. then 18 months later once I fixed my room, I had to start over. and it was night and day better....with just me doing it.

you spend high 6 figures on gear; that gear deserves a relentless approach to getting the room fully out of the way of the musical message.

sorry to blather on and on, but this subject is very passionate for me. YMMV and all that.

good luck with this stuff.
 
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Ron Resnick

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The advice is very warmly received!

How far is your left full-range column from your left side wall? How far is the left side of your woofer tower from the left side wall?
 

Mike Lavigne

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The advice is very warmly received!

How far is your left full-range column from your left side wall? How far is the left side of your woofer tower from the left side wall?

the room is symmetric. so each side has the bass tower sitting on the outside of the radius at a toed in angle with the rear of the bass tower 28" from the actual wall, and 23" from the closest point of the Aural T-Fusor diffusor panel. the main towers are inside the bass towers 7"-8" on slightly different angle.

it took a few weeks of experimenting to get the right combination of open wall behind the bass towers, 3 stacked 2' x 2' T-fusors adjacent to the bass towers, and cloth in front of the bass towers handling first reflections from the opposite main tower (since the bass towers block first reflections from the near main tower). and the side-wall 1st reflection treatment is minimal, cloth only, since it's from that opposite tower and the reflection times are so long you don't need much in those spots.

imagine a 7 foot tall, 750 pound, 30" long 18" wide massive post 2 feet from the side wall with all that acoustical energy bouncing around. you will have unpredictable things going on unrelated to any other things, and that must be controlled, but without deadening the overall musical flow. but until you calm other problems this 'mess' will be buried in the other reflective hash.....and you won't know it's there. it's one of those things that you start hearing as the other issues get resolved and stands in the way of ultimate resolution.
 
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Folsom

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Mike, Ron doesnt have cones in the frequency range where 1st reflections are problematic, the Pendragon panelz have ribbons from 250-18khz, and AMT tweeters to top off the extra bit. His bass towers are 250hz down so they will have to be within 4.3 ft cone center to ribbon center, but the phase is adjustable and will play a key roll. That and they dont have to aim on axis.

Ron, you ribbons are somewhat directional, an acoustic treatment for just 1st side reflections may be all you need. Although having heard Mike's room, the clothe is a good tool for anywhere that is emphasizing high frequencies. But I dont think you'll have that issue unless your chair is near the back wall.
 

bonzo75

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Rodney Gold

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Ron ASC tube traps are ideal .. they do diffusion or absorption depending on rotation .. you can do a blend of both and they work exceptionally for the bass.. they can be moved around to suit.. can be covered with a print or a colour cloth to suit your decor
 

Ron Resnick

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Mike -- It is interesting to me that the closest part of the speaker is just two feet from the acoustic treatment and that you still chose diffusion at that distance rather than absorption for the first reflection because the bass tower blocks the first reflection from the near main tower.

I think, actually, the Pendragons put me in the same place. Flemming recommends the four columns to be positioned on a radius with the pair of towers for each channel right next to each other.

But the question that occurs to me next is: when your bass tower blocks the first reflection from your nearby main tower doesn't that blocked sound wave bounce off the bass tower and zing across the room and create a reflection somewhere on the opposite wall?
 

bonzo75

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Ron, I have been to 3 complete SMT rooms - one flyer's, one an MBL one in Sweden, and one a MCH one. I have also ABed the SMT wings behind the listener at flyer's, at first reflection points at Elberoth's (though many moons ago when I was not convinced of Lampi, if you can remember such a time, and had gone to Elberoth to check), and at first reflection points, behind the speaker, and on the floor at Jazzhead's (his is a partial SMT room).

To start with, none of the SMT dealers themselves will necessarily recommend a full SMT room like the one they have for display purposes.

Now, the wings do create a soundstage and better focus - without them you lose the soundstage and things become fuzzy. Putting it behind the listener also adds to the 3d, without it soundstage falls to the plane of the speakers.

Regarding their varicoustic helmholtz, I do not know. I think the full SMTs have a flatter bass response that can be tuned (my preference will be to have more midbass).

I am by no means saying this is the way to go, as I do not know what RPG does. I have also been to a Rives built room. But it is easy to get 4 SMT panels and see what they do for you, and then add on in pairs if you like them. I guess same would be with RPG. I have thought about this many times and there isn't one solution, so there isn't a way to hatch it. You have to get and try.

I will say that nothing will compare to the rooms you will see at Mike's and Marty's - unfortunately those rooms won't teach you anything about a product like SMT, RPG, or other traps. It will just show you what space combined with an audiophile's experience can do. It is kind of like a digital guy saying I want to set up an analog system, so should I go idler, belt, DD, and linear or unipivot? Maybe the analog is a bit farfetched, but point is it cannot be hatched.

Personally as I cannot go the whole hog like Mike or Marty, I will prefer to keep my living room a bit live, putting a carpet part of the floor (can be extended if required), maybe some corner traps if they don't deaden, which I doubt, it is choosing the lesser evil, and if room allows it SMT wings on wheels at first reflections, behind the speakers, and behind the listener, and I really doubt I will be able to do all that. Also open to look at some RPGs. I do think the microsorbers in Joel's room are good too for the roof or over glass http://zero-distortion.org/microsorbers-and-pyt-audio-panels/

With horns I doubt I will need anything more than corner traps and carpet.
 

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