Best Acoustic Products for First Reflection Points

caliaripaolo

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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?


SMT without any doubt in my system.
I use Vicoustic, Acustica Applicata DAAD, Realtrap...but with SMT I got the best results.

I use the wing panels at the 4 primary reflecion points, as you can see here...

IMG_6491-30.jpg
 

bonzo75

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SMT without any doubt in my system.
I use Vicoustic, Acustica Applicata DAAD, Realtrap...but with SMT I got the best results.

I use the wing panels at the 4 primary reflecion points, as you can see here...

View attachment 36652

This is good feedback
 

jfrech

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Hi Ron,

Lots of good advice above. My room uses custom made front, side and ceiling diffusors built from pine planks and lined with differing types of fiberglass specified by my acoustic plan. The front and side wall diffusors are at a specific angle and built from 8ft x 18inch pine planks.

My dealer and I used Rives audio to build my acoustic plan. My dealer is using Vicustic to build and spec out his treatment methodology right now. I am sure their are several others to consider. My advice, hire someone to acoustically measure your room and spec out the types and placement of treatments. Rives cost me $2800 at the time and was money incredibly well spent.

Here is one of the drawings they output:

my room.jpg
 

Mike Lavigne

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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?

I followed my ears.

over a few week period I tried 5 or 6 different amounts of absorption/diffusion in that wall<->bass tower area, and another 3 or 4 combinations of things both in front of and behind that area. what I discovered was that when I had the same slightly absorptive cloth over the entire wall the sound was not balanced. some of the resonance continued, and overall I lost some life. then I tried to add more than the 3 stack of 2' x 2' T-Fusors and that was again dead sounding. the right balance was cloth ahead dealing with the opposite main tower reflection, the T-Fusor stack just opposite the bass towers, and bare wall behind. there is no substitute for the process.

is it possible just to throw the same wall treatment everywhere and miraculously have it be ideal everywhere? well....er.....it would be a miracle/accident. do you believe in miracles/accidents? OTOH if you tried multiple things in various places and the same treatment everywhere was best, then at least your ears led you to that conclusion. you followed the process.

it does look cool with the same treatment on all the walls, and maybe with some driver types it actually works that way. but remember; this is small room acoustics, where everything is interactive. and proximities are small in an acoustic sense, so each wall area is dealing with a different situation. looking back you may think you understand why something worked, but really.....you don't know for sure what lesson you learned. trust your ears always.

there are too many variables to know ahead of time.

I did experiment with foam taped to the inner edge of the bass towers near where the main tower mid and tweeter drivers are......thinking that I might have got some sort of reflection/distortion off that corner of the bass tower. it is quite near my ears. but I could not hear a difference with the foam there or not. so if there was an issue it was not audible to me. this is one of the last things I tried, and at that point my system was telling me everything. on this subject, obviously the speaker is voiced by the designer with those bass towers sitting next to the main towers; I was in his room in San Diego when he was finalizing the crossover design on the first pair of MM7's and heard it myself (which caused me to order the MM7's to begin with). so if that was an issue he would have dealt with it. I cannot say how that relates to your situation and different driver types of your main towers. I think you have to keep attacking any possibility.
 
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853guy

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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.

Partly. Mostly, it depends on the energy reaching the side walls and at what frequency, which itself is a combination of the dispersion characteristics of the speaker and the room’s dimensions. In other words, how much diffusion/absorption is required at the first reflection point is the non-linear result of the interaction between your speaker and room’s ability to deal with both the energy the speaker outputs at various frequencies combined with how much energy the room is able to deal with at a given frequency for a given output.

Distance of the speaker to the side wall is not in-and-of-itself enough of a contributing variable to ascertain the amount of diffusion/absorption required. That the first reflection point will affect certain aspects of reproduction relating to soundstage and imaging is of course dependent again on the speaker’s dispersion characteristics, and how linearly/non-linearly it interacts with that first reflection point. The interaction between speaker and room is unique in every case, and the relationship between them is always non-linear (where a change in the room affects the speaker's performance and a change in the speaker's placement affects the room’s ability to deal with it). This is why I personally would experiment with a non-permanent solution allowing continual fine-tuning in combination with speaker placement like the SMT wings having heard them several times and been impressed with the way they deal with frequency and phase.

This is a helpful thread if you wish to explore more: http://www.whatsbestforum.com/showthread.php?15043-SMT-Wing-Diffusors-vs-QRD-Diffusors-Effective

On a related but lesser note, many rooms I’ve been in that have treated the first reflection points via a mix or diffusion/absorption have achieved impressive soundstaging/imaging, but often at the expense of centre fill, dynamics and time coherence. Basically, treating one variable in isolation usually results in a compromise over many more.

Best,

853guy
 

microstrip

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(...) 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. (...)
This is one of my embedded points - is Ron looking for advice to keep busy for the next 138 months? :)

But we addressed the key point before - in small room acoustics each case is a different case. And Ron, IMHO poor decisions or materials are hyperbolic - once you make a mistake, it is difficult to go back in the proper way. It is not like changing cables ...

Remember that marketing strategies of most manufacturers of acoustic treatments are not very different from those of high-end. If you have the time read F. Toole on acoustic treatments - there are some wise words in his famous book.
 

Ron Resnick

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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

I agree. I have and use many 16" rounds.
 

Mike Lavigne

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This is one of my embedded points - is Ron looking for advice to keep busy for the next 138 months? :)

120 months = wandering in the desert making a little progress here and there.

then; the speaker designer visits. takes things as far as they can go with the room as it was.

9 more months later = visited friend with same speakers and amps and heard a reference of things my system was not doing.

1 month later = started experimenting with that reference in my head

8 months later = completed much of my room-re-boot and re-adjusted my speakers by ear for the corrected room.

so yes, it was 138 months......but the magical moment was acquiring the sonic reference of where I needed to go. I was fortunate to have all the pieces already that I needed to have to attain the reference. the 120 months of wandering did allow me to evolve and learn.

my message would be to either have that sonic reference, or trust someone else who has it. but it's the sonic reference and working toward that that is key.

But we addressed the key point before - in small room acoustics each case is a different case. And Ron, IMHO poor decisions or materials are hyperbolic - once you make a mistake, it is difficult to go back in the proper way. It is not like changing cables ...

Remember that marketing strategies of most manufacturers of acoustic treatments are not very different from those of high-end. If you have the time read F. Toole on acoustic treatments - there are some wise words in his famous book.
 

caesar

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Ron,

Good to see you on the right track of questions for your killer-to-be system! A lot of good advice in this thread!!!

As I mentioned in the "We are There" thread, there is no perfect formula for this due to differing preferences and approaches. You will have to experiment with diffusion, or maybe the magic curtain Steve has will meet your goals? Nevertheless, here are a few points:

1. SMT wings come in acrylic (transparent looking ones in the pictures in this thread) and wood. Word on the street is that wood works better, but I assume the acrylic ones can be moved around easier in a multi-purpose room. So if you ultimately don’t like them, you an easily sell on the used market. Likewise, I think your ASC bass traps may be moved as well. FLEXIBILITY is key to this process!

2. As Bonzo mentions above, SMT recommends a 48 -72 inch-wide “wall” of panels a few feet behind the listener (the rest of the space in the back is wide open). In my experience, that wall alone is better than any speaker or component upgrade you can have (assuming you already like the lesser-priced model from the same designer), let alone some dumb fukc spending big bucks on still point –type footers, cables, power cord upgrades, etc., that may cost more than the room treatments. We all get addicted and conditioned to buying gear, but the room is where the ultimate magic comes from

3. Finally, at the last Axpona there was buzz among acousticians that Magico was dumping their RPG stuff and trying SMT (after spending $300K-$500K on the RPG room!). So the person who would know about direct compares of SMT to is Alon Wolf.

Now again, tastes will vary. Jason Victor Serenius, the Stereophile show reporter, paid a visit to the Magico factory and called the sound too analytical for his taste. https://www.stereophile.com/content/visit-magico-factory

Yet “Sterile” Jon Valin paid multiple visits to the Magico factory listening room to review several speakers like the Magico Ultimate, he called that speaker Best in the world and most-lifelike. There is a reason “Sterile” Jon has earned a nickname of “Sterile”, so that room may have sounded PERFECT for his analytical tastes, whereas guys like Serinius find it dry.

Yet there is also a history of TAS guys not being fully forthright in their reviews – calling the product under review as Perfect as God, and only identifying weaknesses of a product like Berkeley Ref v1 only when reviewing v2, and identifying weaknesses of Magico Q series when M Professional model comes out. So, because of mis-aligned incentives of getting that next, new Magico speaker for a long-term free loan, unfortunately, one cannot know if comments from Valin can be trusted to make a decision for one self.

So although Serenus wasn’t hot about the room, while Valin was crazy about it, what ultimately matters is the fact that Wolf is not happy with the room. So the ideal thing to do is to ask Wolf. Not sure if he will be a good “citizen of our culture” and help out but it may be worth asking him.

Wish you all the best!
 

Folsom

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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?

Ron, a typical cone & dome dipole looks like a circle/apple coming out of the speaker on each side, but yours will look close to a cone shape most of it's bandwidth. You don't get much reflections directly to the side of the Pendragon towers because they are too directional to project much of anything straight out the sides of the baffle. Even if you did, they won't be directed at you so by the time they get to you they are not 1st reflections. The problem they can represent is comb filtering, where interactions with other frequencies causes an EQ effect. But I don't think this is of any real concern given the directionality of them, and the distance between the two channels. (so long as they are not directly against a wall)

There's no reason to have the bass tower beyond the panel tower towards the listener. In fact you can push it back some as needed. You could even overlap them slightly to the point where you could only see the drivers of the bass panel on each side. There's plenty of room to tweak about for the frequency ranges they play. Mike is suggesting to try and get them optimal because you don't want problems with bass, and you've got the ability to move them a bit to figure that out. There is no amount of measuring and preconceived planning that can trump what will sound natural to the ear. You'll simply have to move them around a little and play with phase. Set phase with them in a reasonable position, then move around till you find what you like, and then set phase again. Probably repeat, repeat.

For distances between the bass and panel tower, imagine drawing a line from the center of the ribbon (center of panel) to the inner dome of the bass driver. That line can be any direction within 4.3ft, probably 4ft for safety, with the two towers having any placement desired that keeps that connection. The frequencies the bass towers play lose directionality sharply as they lower, allowing the grace to move them about in conjunction with the wavelength distance needed to make the two towers sound like one speaker.

Your first reflection point might be closer to the listener than with traditional cone & domes, actually. I would get some SMT's and move them along the walls towards you till you find the sweet spot. Then you can install them more permanently if that's your wish. Then you could have a second pair and do the same thing, to catch lower frequencies, if you were not satisfied. But that might give some diminishing returns where you just can't tell or care.
 

caesar

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caesar

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Does anyone have any insight into the time delayed diffusion of smt vs. the type of diffusion performed by rpg products?
 

Folsom

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Does anyone have any insight into the time delayed diffusion of smt vs. the type of diffusion performed by rpg products?

If you look at the SMT's, basically waves go in and come out late compared to a direct reflection. RPG's just use forms of staggering so that waves will comb filter a lot with each other, as the same frequency is hitting different delayed time reflections and will cause a canceling mix. Sometimes diffusion just sounds bland to me, but delay keeps more integrity.
 

bonzo75

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Ron,

I am not familiar with the other products. But with SMT, one can get the speaker very close to the side walls with only the positive benefits of a larger soundstage(!!!), but no downsides. Look how close to the walls this guy has put his MBL Extremes:

http://www.whatsbestforum.com/showt...g-is-your-room&p=474313&viewfull=1#post474313
The
They are kept close because the wings are 1.5 to 2 feet deep, so the waves are supposed to be traveling that much and coming out
 

microstrip

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Does anyone have any insight into the time delayed diffusion of smt vs. the type of diffusion performed by rpg products?

I have never seen a detailed mathematical analysis and simulation of the SMT wing diffusers. The RPG products supply a lot of detailed data on models, measurements and simulations.

Please note that my comment does not mean anything about performance or imply any opinion on them!
 

Ron Resnick

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microstrip, Out of all the listening rooms I have visited Steve's room has the most extensive acoustic treatment. None of the manufacturer's rooms I visited were heavily treated.

Kedar, That all makes sense, thank you.

Folsom, My listening position will be close to the back wall. I will have to experiment with pulling the listening chair toward the speakers in an equilateral triangle to get the listening position more than three or four feet from the back wall. In the past I have used absorption on the back wall because my listening position has been close (too close) to the back wall.

caliaripaolo, In my particular set-up I place no treatment behind the speakers. I want a clean, unadulterated rear wave bouncing off the front wall. This is one reason I am inclined to use absorption at the first reflection points rather than diffusion -- I want an unadulterated reflected back wave so I want to make sure no first reflection mixes with that back wave.

jfrech, What was the evolution of your room design process? Did your acoustician measure an empty room and then design the treatment plan? Or was the room measured and the treatment plan designed after your equipment was already placed in the room?
 

microstrip

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(...) caliaripaolo, In my particular set-up I place no treatment behind the speakers. I want a clean, unadulterated rear wave bouncing off the front wall. This is one reason I am inclined to use absorption at the first reflection points rather than diffusion -- I want an unadulterated reflected back wave so I want to make sure no first reflection mixes with that back wave.

Ron,
It seems to me you are focusing excessively on the seating place and forgetting the overall situation - unadulterated reflected waves can create standing waves with large decays, that color sound. Your ribbons are long, but do not have the large area of the Prodigy's - the ratios between reflected and direct sound will be very different. Probably one of the reasons F. Rasmussen likes a lot of diffusion is because he knows diffusers absorb significantly and break stranding waves.
 

caesar

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Gentlemen, thank you. Does anyone have any insight or ideas on why SMT would recommend a 4-6 foot wide wall a few feet behind the listener's head, regardless of how far the listener is sitting away from the back wall? In instances of a large room, there could be a fairly large open space behind and around the listener. As I mentioned above, this wall could make a ginormous improvement in sound quality in helping to carve out the acoustic space of the recording in one's room. Thanks .
 

Folsom

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Sounds like you're going to need treatment behind you. This is a place where I'd be interested in absorbing materials or intense diffusion.

Delaying the 1st reflection may just enhance the back reflection from the dipole a bit, but I can see your point in being interested in only having the rear reflection. I just don't know if I believe you can absorb enough not to give a slightly odd bland sound. Also your 1st reflections may be rather close to you, making them not as likely to comb with the rear.
 

Ron Resnick

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. . . On a related but lesser note, many rooms I’ve been in that have treated the first reflection points via a mix or diffusion/absorption have achieved impressive soundstaging/imaging, but often at the expense of centre fill, dynamics and time coherence. Basically, treating one variable in isolation usually results in a compromise over many more.

Best,

853guy

Thank you, 853guy!

I am not clear what you are intending in your last paragraph. Are you suggesting that it was the mix of absorption and diffusion that achieved impressive soundstaging/imaging, but that that same mix diminished center fill and dynamics, and that that audiophile would have achieved a better balance of soundstaging/imaging and dynamics if he had selected absorption or diffusion at the first reflection points (rather than a mix of absorption and diffusion)?
 

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