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How Much Do Room Acoustics Matter To The Performance Of Your Speakers, Amps & Cables

Dennis Foley September 16, 2014 No Comments

In the following video and transcript Bruce and I discuss how much room acoustics matter to your ability to enjoy the performance of your Amps, Speakers and Cables. We were just kind of sitting in his room and Bruce asked me a few questions about some of the things we’ve done, and the technologies I’ve developed and the first question is about the foam.

Why did I create our acoustic foam?

There’s a lot of foams out there. They do certain things well but most of the time they don’t do the right thing well and the right thing is frequencies below 500 cycles. When I developed the foam for the conference rooms with the development company, I realized that the human vocal range was from 100 cycles to about 800 cycles and current foam technologies on the market place were just not doing that.

They did everything about above 500 cycles really well, everybody can do that with their foams but below 500? Not so good and that’s really the most important part from 100 to 500. Its where we really need to focus because that’s what 60, 65 percent of the activity in the human vocal range, both female and male, occurs. So I made a concerted effort, after trying many of the foams that were in the market place, trying to figure out a better way to do it.

Why foam?

Well foam is very lightweight, it’s easy to ship, it’s easy to form and make into different shapes. It’s not so easy to build but it’s not that bad either. We have kind of a special process we use and it’s fairly economical.

The main thing that I was after was a smooth transition from 100 cycles to 500 cycles and we’ve achieved that with our acoustic foam and you can look at the performance data in the below graphic. So I wanted something that was lightweight, economical, easy to work with. I didn’t want mineral wool, I didn’t want fibers, I didn’t want people breathing fibers that we’re working on the material. So I stayed with the foam because that was the way to go to meet all the parameters that we had for our upper end conference rooms and offices.

Foam Comparison

Foam Comparison

And then we started to realize that the foam really worked well for music and absorbing a little bit more energy at a 125 cycles and a nice transition to 250 really worked well for vocals but really worked well for music also. So thus, we’ve started to tell people about it for music and some of the local studios here in town have actually torn out their Auralex and Sonex and put our foams in. So we’re slowly catching on, people are slowly realizing that the absorption curves in our foams are different, they’re unique and they’re really smooth and they really work well for voice and music, both. So we’re excited about our foam technology.

What about the carbon?

Well the carbon technology took us a while to figure out. We built so many rooms, I think 116 in our database and I wanted to come up with a way to take that construction methodology and the vibration free systems that we developed and making it in a freestanding unit that people could put in their houses, in their hi-fi rooms and not obviously build walls. Although we can do that and sometimes I prefer doing that, but a lot of times people don’t want to put walls and tear out walls and add new things into their home so I understand that.

So it took us about six years to figure out the construction techniques that we wanted to use and inside each one of our units is a structural representation of what we did in a permanent build situation. There are seven different layers, vibration damping compounds between each layer, so we have a cabinet that is built, in all honesty better than most speaker cabinets and probably equal to your high end speaker cabinets in terms of vibrational characteristics.

So we have a very inert cabinet. And then I’ve tried to figure out, “okay I need a fill material because I want to raise the Q value inside the cabinet. I want to get this thing to be really powerful. I want to create a really high, low pressure area inside the cabinet” and that’s what I finally discovered with the carbon which, as we were talking the other day, was strictly by accident.

I had a water filter on the office faucet blinking and I couldn’t figure out how to get it apart, so I hit it with a hammer and out comes all these little granules of charcoal. So I have a magnifying glass, one of those that the jewellers use because I’m always looking at things closely, and I put it under there and looked at it and saw the carbon is full a holes. So I started doing a lot of research on activated carbon, or charcoal as it’s called, and found it filters water and it filters air. Well sound is in both of those medium.

So lo and behold we started testing it and working with it and found it was finally the material we needed. We did use one material before that was kind of promising. It’s called Zea-light which is a filtering agent. We even used diatomaceous earth. We even tried those but activated carbon, pound-for-pound, gave us the best performance and we’re real happy with the performance of the units.

ACDA-12 Unit Is A Bass Absorbing Beast

Our ACDA 12-unit is a really powerful sponge at 30, 40, 50 cycles because that’s what our data in our room database told us was needed. In 96 or 97 percent of the rooms we had researched, 30, 40 and 50 cycles were all problems so that’s the reason for the ACDA 12. And then the ACDA 10 is a broad band absorber from 30 cycles to 200 and it’s about 24, 25 percent absorption through that range and its real, it’s not linear but it’s pretty close, and it’s a nice broadband absorber to kind of fill in the gaps with the other frequencies.

So we have two powerful sponges so to speak, for low frequency energy with the activated carbon charcoal on the inside. We use 65 pounds of it in each unit. Bruce’s units are custom, they’re bigger, they’re 30 by 60 so he’s actually got 85 pounds in his units. So we want to keep the ratios and everything together. It really does a great job. Now you need more than one unit, you need more than two units in an average room. Four units is probably a good start point and some rooms need a little bit more. It just depends on how big of a low-frequency problem you have and most people have big low-frequency problems and you’ve got to get the low frequency energy right first because that’s the foundation for your mids and highs to ride upon.

If you don’t get the low end right, your mids and highs are going to suffer. So if you don’t get the low end right the mids and highs are going to be blurred by room modes and low-frequency pressure areas and we don’t need that. We’ve all heard those, we’re all frustrated by those and that’s what we’ve decided to do something about.

This Adventure All Started Back In The 60’s

I started my hi-fi journey back in the 60s, back then, if you remember, was the Sansui’s amplifier and the Sansui speakers and the guys who went to Vietnam would buy those and ship them back to the States. If you remember the Sansui speakers they had the wood working on the grill, the lattice work and the fabric and actually I also had a quad system so I had four speakers, remember the quads system? The double advents? The quadraphonics?

So you had the four speakers and basically they sat in the room. So that’s kind of how I started and then I got more interested in the 60s and went to the components in the Ceper. I think I had a dual 12, 29 turn table, sheer cartridge and Marantz amplifier, I think model 30 and some JBL 100’s I believe. It was the speakers that I started with on my first album. I remember that to this day was James Gang rides again, I just watched an interview on guitar center the other day with Joe Walsh. And it was a great interview and he was telling about being in the James Gang and how he came about to be the singer because the singer they had at that time quit so he had to sing and this is how it all came about.

So it was a really funny to hear all that but since that time I’ve owned numerous equipment. Cello Music and Films performance two amplifiers I’ve probably had 10 of those model blocks, hundreds of thousands of dollars in those amplifiers. Krells, Dan D Agostino’s amps the old reference series with the kind of a round eye in the middle with the meter on it. I’ve had four of those BMW 800’s. I’ve had Mark Levinson’s cello big towers, multiple array systems. And BMW, I think I’ve had the 800s the 801s, the 803s, the 805s, just all kinds of gear but I think I totalled it up the other day it’s about $400,000 in gear that I’ve bought over the years.

And yet I always had room modes like we all do. I always had those areas that, when you play in certain parts of the music, it was like: “Oh no! There’s that big massive bass pudding” so to speak in the room. So when you were giving demos to your friends you try to avoid that, you try to not play that particular song because it emphasize the bad parts of your room but no matter what the gear was that I bought, I could never get the room to sound the way I want it so I started focusing on the room.

BRUCE: I didn’t have the kind of money that Dennis did. I know that after my Pioneer double advent system in the late 60s in Chicago I went directly to the stereo 70 PAS3X. So I was a tube guy and ELS35AS, I went through that whole thing and then I chased the dream from there and went through Magnapants and anyway.

DENNIS: Oh you had magnapants?

BRUCE: Yeah and I was still chasing what I thought was really good sound. I’ve been chasing it for… as long as I have. Yeah for a long time and the difference now is I’ve realized that if I was chasing something else in room acoustics, in room treatment, and what Dennis has been talking about, and technically I have no idea what he’s even saying, but I can tell you what my ears hear. And we were just talking tonight, I just went through almost a $20,000 pair of speakers to a worn speaker that is 10 percent of the price of that. And we’ve got a room going on now that absolutely blows by otherwise.

DENNIS: There you go…

BRUCE: Yeah. End of the story.

DENNIS: It’s not the price of your gear. You can get that emotional connection with your music. You can make that music part of you if you treat your room correctly. 50, 60 I’m almost going to say in some cases seventy-five percent of what you’re after is getting the room out of the way. Getting rid of those acoustical distortions of your room, comb filtering, speaker boundary interference reflection, room modes and poor diffusion. You didn’t know anything about diffusion before?

BRUCE: No, but in the last few weeks, I promise you, we have added $20,000 cartridge, $40,000 preamp and it’s unbelievable what’s happened in this room in the future and I’m being very serious.

DENNIS: And people just don’t understand that. There’s a reason poor diffusion is one of the four major room acoustic distortions in small rooms. They don’t understand how important good diffusion in a room is, how important it is to voice. I mean even our vocals, even our voice is better, you know, next to the diffuser. They don’t understand how important diffusion is.

Quadratic Diffusion Is Our Favorite

Quadratic diffusion is one form of diffusion. There’s others that you can try. I like quadratic because it’s consistent and it’s predictable and you can get at least two dimensions of diffusion. You can get horizontal and vertical diffusion. And that’s important and having the proper diffusion in a room especially in a room where music is played is critical. And if you don’t know that and you have never experienced that, we’ve all been in rooms that are over damped that just drain the energy out of the music in.

If you calculate what our music cost with the price of amplifiers today, my gosh, amplifiers, 20, 30, 40 thousand dollars, I saw some past live amps the other day, $85,000. I mean and speakers that are equal in price, what does that equate to per watt? Well that’s a lot of money. So you want to make sure you’re hearing all of that because we have made great strides in amplifiers and speakers but people don’t understand the power of the room and room acoustics are kind of left behind.

And we need more education in that area. We need more people experiencing diffusion. And this whole week we’re going to be playing that, we’re going to have some people come in on Thursday and Friday and bring some new amplifiers in and we’re going to try those but we’re taking this week to really address the room in its entirety and work on the issues that the room acoustics have.

BRUCE: Yeah and really, begin to understand and hear what all of this means. You know, I can’t put it into technological terms but I can put it into what my ears hear and I would love to hear what my LS 358, my stereo 70 and my PAS3X and my regular one turn table and my sheer type 5 micro-ridge cartridge would sound like. Seriously, Dennis, it sounded good then, oh my goodness, so I look forward to the future.

This Week Is Critical Listening Week

DENNIS: Yeah. It’s going to be a fun week for us. One of the things you have to realize with room acoustics, it’s a combination of a bunch of little things that produce big sound. Controlling the sidewall reflections so that the direct sound and the reflected sound arrive at the listening position in balance you know. That’s going to be a little different for everybody because everybody;s tastes are a little bit different but you’ve got a time frame to work with and you need to do it and rate and level of absorption on the side wall is critical.

With diffusion, front and rear walls very important in hi-fi rooms, people just don’t understand that. How important it is. We have six diffusers, 6 of our QDA series in here and we still need some more and we’re going to talk about actually building Bruce a wall of diffusers for his front wall. And then I want to build him a wall of diffusers for his rear wall but we’re not going to be able to do it permanently.

So we’re going to build individual units that he can move in and move out as conditions dictate so this gives him a little bit of a flavor. I only had six units in inventory right now to bring but he’s really had his ears opened with diffusion. Tell us a little bit about the sound of diffusion? What’s different? Remember when we had them right up against the chair the other day and then I moved them back, tell us a little bit about that.

BRUCE: First of all, no matter where they are in the room, you adjust the chair and the distance with the diffusers behind you, in front to really accommodate the sound stage and whatever you’re looking for. But all of a sudden with these here you know it was a very simple test and I’ve done it before, just put your hands behind your ears and you listen into your music. Well all of a sudden everything becomes more articulate but you can’t listen to it because it’s so bright because you’ve get your hands.

Well, simple as it sounds that’s exactly what the diffusers do only the articulation, and that’s the only way I can say, is something I’ve never experienced before. I do think that a lot of the tonal color and the musicality and all this kind of stuff does come from your system but there’s no question in my mind that the diffusers bring all of that out and you know, it makes a $5,000 system a $20,000 one and it’s really unbelievable. So you know the hard part was here’s my room, and it was the worst room in America as we all know, and actually the person that I bought the speakers from, my old speakers, he walked in here and said what are you doing with this room? This has got to go but nobody had the answer. They knew it was bad but okay well what do I need to do? And so, this idiot (Dennis) came and so it’s been a pleasure.

Absorber Blinds Coming Next

DENNIS: Yeah it’s been a great project because this is a big room. We’ve got 16, 18-foot slanted ceilings of all kinds of alcoves and stuff and we’re actually doing our absorber blinds which are going to come out with next year. Bruce is getting the first two right out of our shop and those will be ready in about a week, oh, about a month and then we’ll do a video on those for you. Those have our half inch foam on both sides of the vertical vane with fabric on both sides and works just like a vertical and you cover your windows with it.

You get an inch of foam absorption so you get that bounce off the glass into the foam. You get any reflections from the room into the foam on the other side and then you can open them and then close them and Bruce has the standard 8 foot by 7 foot sliding glass Arcadia door that we all have in our homes and the whole thing will cover the window close to 15 inches.

So it’s going to be a great product for glass because glass is a pet peeve of mine. I firmly believe that sound takes on the characteristics of the surface that it strikes. Don’t ask me to prove that scientifically, but we all know what our sound in our car sounds like and that’s a real good example of glass sound. It’s like listening in a fishbowl. No matter where the manufacturer puts the speakers in the car, the reflections off the glass are hideous and it’s brittle, it’s bright and you always get that with glass. So absorbable blinds are going to take care of that for you. So well enough talk, we’re going to do some listening so thank you very much.

In Summary

If you want to learn more about this subject please sign up for our free room acoustic treatment videos and ebook which provide step by step instructions on all major room acoustic issues. Get instant access by signing up now. And if you would like your room acoustic issues analysed for free by me then please fill in the form here and I will be happy to take a look for you.


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Dennis Foley

I am an acoustic engineer with over 30 years’ experience in the business. My technology has been used in Electric Lady Land Studios, Sony Music of New York, Cello Music and Films founded by Mark Levinson, and Saltmines Studios in Mesa, Arizona, along with hundreds of others. Connect with me on Google+

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