Gobsmacked by Acoustic "Tweaks"

Here goes:

RPG Systems

Alex,

I'm considering doing something similar and currently wondering about cost. I was thinking of going for a complete 'Skyline' ceiling and 'Diffractal' (or similar) rear wall. (Its okay, I have a dedicated listening room.)

How much are the 'Skylines' individually ? If you are saying 12 sheets of foam and 6 skylines comes to almost £500 that seems quite expensive. Still, if the end result justifies the price I guess its money well spent.

Allan

Just to say that the Profoam absorbs unwanted sound and the Skylines diffuse extraneous sound.

Allan,

A single Skyline cost about 50UKP, a box of Foam about 170.

I think 6 Skylines has been ample for me. I doubt if you would need to do the whole ceiling although it would doubtless look better and I do like a slightly live sound.

I will probaly need one more box of foam and 2 base corners (100UKP-ish) to be totally happy.

It is expenseive for what it is but you're paying for mathematics as well as polystyrene - and boy does it work!

My total cost will be about 750UKP - less than the cost of a Hi-Cap - and the benefits are not far short of magical (I should get money for selling this stuff!), in my case at least.

I had a look at your system and it seems to me worth spending a few bob on the acoustics, but I don't know what your listening room is like presently.

If you think they're no good RPG would buy the Skylines back off you - so long as you mount them on the T bar/Velcro method rather than gluing them on.

Their promo copy is certainly entertaining:

quote:

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To solve this problem, RPG® utilized advanced primitive root number theory to design the most powerful and aesthetic two dimensional omnidirectional diffusing surface in the acoustical industry.

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I really like the part about "advanced primitive". Do you know whether they send stuff to Canada?

-=> Mike Hanson <=-

Do you not have foam between your ears in the picture?

I do agree that "advanced primitive" is a novel departure from recognised English useage. Must be North American or Antipodean. Apparently they sell a lot of this fancy foam to the Belgians.

I'm not criticizing the product. I'm merely poking fun at their promotional stance. They're attempting to inundate their potentional customers with techno-babble, with the hopes of stunning them into a buying stupor.

Their products probably work very well, but I don't know whether it's any better than a few bats of Sonnex foam panels and/or tube traps from ASC. Maybe a few rugs plonked on the floor and hung on the walls would provide many of the same benefits.

For a much cheaper way to obtain the similar gains, check out http://www.ethanwiner.com/basstrap.html. It would depend on your ability to build the things, of course, and the end result may not look as pretty.

BTW, there are a couple of dealers for RPG's stuff here in Toronto, so I'll probably take a look. I've got to get the gear into my listening room first, though, so that I can determine what the problems are. I'll start with rugs and such, then tweak from there as necessary.

-=> Mike Hanson <=-

This is nothing against Mike but despite the fact that this is the Naim forum I find it odd that so many extol and accept without audition the virtues of adding two grand power supplies but become sceptical and jokey as soon as room acoustics are discussed.

I speak only for RPG products, I'm sure there are others just as good, and only for my own listening room but I am neither exagerating nor joking when I say that 470UKPs worth of foam absorption and diffusion gives me more sonic improvement than the CDPS and the 2 Hi-caps added together - I've just tried it.

Since I also wrap all furniture in blankets during transport I have been able to experiment with up to 15 at vaious levels on various walls. I tried this before foam purchase and it does not work. I also tried cushions on the floor and that doesn't work either. When I say doesn't work I do not mean that there is no sonic difference. Some of the echo went but it was very inefficient and also deadenend the room. I do't want a dead room which is why a combination of absorption and diffusion is important.

I speak with the zeal of a convert because that is what I am. 2 weeks ago I too only considered plug in boxes with the word Naim on them to be value for money and the way to improve my listening pleasure. I still want a Supercap and 135s instead of 250s and perhaps an XPS instead of a CDPS, but if and when I get them I can rest easy that they will sound their best (Fraims in place by then of course).

I urge the sceptics to try improving their listening rooms and to trust their own ears when judging the results. That's how I bought Naim instead of Marantz in the first place.

I realize that rugs are not as good, as they handle on a small range of frequencies. However, when you try a couple of different rugs, and a piece of furniture, and a few bits of furniture, art, shelves, etc., the variation in "shape" of the room deals with many of these issues.

However, filling your room with stuff is not always an option. My dedicated room is very small (9.5x13 feet), so I can't fit much more than the electronics, speakers and chair. Therefore, I'll have to do something to damp the flutter reflections that are currently predominant. I'll start with a big rug and curtains on the windows, but then I'll have to look to other methods. RPG's products (or similar DIY techniques) are likely the way I'll go.

-=> Mike Hanson <=-

Cripes, even for my fairly modest, 11ft x 14ft listening room, and allowing for a generous untreated border around the outer edges, I would need about 40 tiles. Perhaps something a little less ambitious to start with.

I still think diffraction is the way to go. As a bit of an experiment I recently put up a rack in the listening room to hold my CDs that were previously in a cupboard. The rack covers about 14 square ft and consists of approx 6" x 6" pigeon-holes populated randomly full. Even though the rack wasn't directly covering one of the reflection points and 14sq.ft is a tiny fraction of the total room surface area it made a noticeable improvement.

However, I have noticed over the years that following upgrades of the equipment, room problems seem to matter less. Probably something to do with psyco-acoustics. The better the sound gets, the easier it is for the brain to lock-in to what it knows to be 'right' and ignore anything else that is going on that is a distortion of, or distraction to, the original signal. After all, I'm sure you would still recognise the sound of a live band if it was playing in your listening room, regardless of how bad the acoustics are.

Allan

Forget the ceiling and put 6 Skylines infront of the speakers and behind your listening position - it worked for me.

Quote:

"However, I have noticed over the years that following upgrades of the equipment, room problems seem to matter less. Probably something to do with psyco-acoustics. The better the sound gets, the easier it is for the brain to lock-in to what it knows to be 'right' and ignore anything else that is going on that is a distortion of, or distraction to, the original signal. After all, I'm sure you would still recognise the sound of a live band if it was playing in your listening room, regardless of how bad the acoustics are."

I have posted almost identical remarks before foaming. To an extent you are right but you are wasting so much of your system's potential.
I don't want to keep going on but I would be surprised if my CDX/82 did not sound better in an acoustically treated room than your CDSII/52 in an untreated one.

I would be interested to know the views of the moderators.

A less - expensive alternative to RPG Skylines are the "T - Fusors" by Auralex Acoustics. Engineer Jon Risch suggests that the back of the T - Fusors can be filled with expanding insulation foam (the stuff that comes in aerosol cans and is used to fill gaps around windows etc.) to lower the effective frequency range of the devices. My basement listening dungeon has a stone wall on the left side and a long built in closet on the right. The stone wall has wonderful random diffusion off the stones; to balance the diffusion I put 2 foam - filled T - Fusors at the first reflection point on the right side. The increase in spaciousness on the right was immediately apparent. Auralex doesn't sell direct to consumers, but the big music and pro sound retailer Sweetwater does. For comparison, they sell a set of 2 Skylines for US$260 and a box of four T - Fusors for US$183.

I have no connection with either of these firms other than as a satisfied customer.

I notice that noone has commented that had I really done a comparison test which involved removing both Hi-caps from the 82 I would have heard nothing at all.

But I have a more serious point:

I note a sort of grudging acceptance that this RPG foam will probably work but that there are other cheaper products available. Fine. But if RPG produce one of the best products (and most recording studios et al seem to think so) it seems churlish to complain of its expense so long as it does an excellent job and represents value for money. Surely Naim products are exactly the same.
Many of us complain of their expense but very few of us choose not to buy them since we believe that they do an excellent job and represent value for money.

Unfortunately my foam will not hold its value (or its shape) like my Naims.

I really appreciate this thread right now. As I've already mentioned, I'm soon to embark on the tuning of my own room. Some of the information mentioned in this thread will really help me along.

As far as the price goes, the RPG stuff seems too expensive for what it is. They've attached a bunch of fancy words to the product, supported it with seeming pseudo-science, then slapped on a big ticket price. In the end, I think that cheaper products can be had that are similarly effective.

Also, I think many (but not all) of their products are obtrusive and ugly. BTW, I feel the same way about Mana. In the case of Mana, however, I'm going to be using it, but it's being hidden due to its unappealing appearance.

Unfortunately, I can't hide the acoustic treatment products. Therefore, I will try many other possible solutions before I start gluing RPG Skylines throughout my room.

-=> Mike Hanson <=-

Seems like we must soon agree to disagree. . .
but not quite yet. . .

I am certain that a man of your immaculate dress sense and good humour may learn to love Skylines (although I agree that they seem even pricier in your part of the universe).

In my opinion a few, well placed, clean lined foam blocks may well look better than an explosion of rugs, blankets, cushions, cheaper foam tubes, panels etc. Unless you wish to be fine tuning ad infinitum and living in an expanded laundry basket you may consider the efficiency and therefore the minimalism and cost of RPG products to be more attractive than you first perceived.

I will now leave you in peace with your interior decoration and Mana hiding, (until you force me to continue of course)

Regards Alex

By the way "pseudo-science" is science that is bogus, hyperbolic and ineffectual and therefore not the case here no matter what you think of their choice of language. Like you, I have no time for pretentious trash but a little more for pretentious erudition.

Perhaps calling RPG's approach "pseudo-science" is somewhat inaccurate.

What I want to know, though, is what do fractals have to do with diffusion/absorbtion? It sure sounds cool, but I believe a truly random surface would do the job just as well or better. Of course, only a certain level of randomness is really necessary to create the desired effect, so it shouldn't matter whether the shape is based on fractals, or just some piece of foam scratched up by the neighborhood tabby. Focusing on the factal aspect is, therefore, both misleading and inapplicable. Perhaps pseudo-science is a valid monicker after all.

WRT having a few well placed bits, it will not eradicate problems in a generally reflective room. You must add enough material to prevent the reflections from propagating in a negative fashion. Considering how much RPG stuff I would need, I'll only go that way if absolutely necessary.

As I mentioned earlier, I'll start with a big rug on the floor, maybe one or two small rugs on the walls, some curtains on the windows, my chair, the CD case, some statues, pictures, etc. If I've still got a problem (which I'll check by ear and with an SPL meter), then I'll determine what other things need to be tweaked. Maybe I'll end up with a couple of bits of foam from RPG to deal with near reflections, or maybe a Tube Trap from ASC to handle bass in the corners. I'll cross that bridge when it comes.

-=> Mike Hanson <=-

Before anyone accuses RPG of using "pseudo - Scince" in their diffusor design, take a look at F. Alton Everest's "Master Handbook of Acoustics". He explains how some of RPG's products work. Or you could order Dr. D'Antonio's paper "The QRD Diffractal: A New 1 or 2-Dimensional Fractal Sound Diffusor" from The Audio Engineering Society. It's preprint No. 2938.

Mike, a better tool for evaluating room reflection problems than an SPL meter is the ETF Acoustic measurement software package. It's awesomely powerful and a bargain at US$149. ETF can do "time sliced" acoustical measurements that show the secondary arrival sound without the direct sound. You'll be able to easily see how bad your room reflections are and the effectiveness of any changes. ETF runs on any Windows PC with a duplex soundcard, even a cheap "game quality" card. The ubiquitous Radio Shack / Tandy SPL meter can be used as a microphone; ETF can supply a correction file to compensate for the meter's frequency response errors. More information can be found at ETF Acoustic.

When you're adding acoustic treatment to your room don't forget the reflection off the ceiling. Depending on the size of your room the path from speaker to ceiling to your ears may be shorter than the one off the side walls. Treating the ceiling can make a dramatic improvement in the sound.

Thanks, Rob. I'll check them out.

I realize that all of these various treatments have their own "science" behind them, and I know that there are better ways and worse ways to do it. In my case, I'm looking for something that isn't too visually and physically jarring, yet still gives the necessary sonic benefits. If I end up with something ugly, I want to minimize its impact. That's why I'm hiding the Mana in the closet.

-=> Mike Hanson <=-