Absorption Panels

[JBP]

How do you determine the placement and the amount of wall you need to cover when using absorption panels, Auralex Pro Panels or similiar?

I have seen applications where panels seemed to be placed in random positions and other examples where the entire wall is covered. Since there not cheap, I was wondering if they can be put on the wall spaced?

You could save a considerable amount of money if they can be placed, say 6 inches apart or more. At what point would exposed wall between the panels defeat the purpose of using them? Are there any other types of wall treatments to consider? Thanks.

[artto]

Spacing the panels out as opposed to side by side will expose the edges allowing more area for absorption per panel (not to be confused with the cumulative result of covering the entire wall).

Where the sound absorption is best placed is dependent on the proportions of your room, speaker location, & listening position.

For most typical situations, the first thing I would do is get a small mirror, 6 will do. While you sit at the listening position, have someone place the mirror flat against the wall & ceiling surfaces, moving it around until you can see the speakers reflection in the mirror. Mark these locations. These are areas of first near term reflections which can interfere with imaging & definition and should be treated with sound absorption first.

If you are sitting close to a rear wall, the rear wall should also be treated for the same reasons. This is a starting point only!

You can tell if and to what extent the rear wall is interfering by placing your hands behind your ears (not cupping them). If you can hear a substantial change in the sound, in particular, if you can hear the sound 'tighten up', you have a substantial rear wall reflection problem.

[Colin]

that's if the room is too bright, right? What about bass humps and dips?

[cjgeraci]

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On 6/11/2004 11:00:54 AM JBP wrote:

Auralex Pro Panels or similiar?

Are there any other types of wall treatments to consider?

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Not necessarily other types. Fiberglass is good. As I understand it, Auralex Pro Panels consist of fabric-wrapped, absorptive 1 inch thick fiberglass panels. Just be aware that the absorptive property of the panel is affected by its thickness. In my case, I went with two-inch thick fiberglass panels because I had a challenging room and wanted more absorption in certain places.

Depending on your room (and where you are placing them), one inch thick panels may do you just fine.

Colin, you bring up a good point with respect to bass. In my case, I simply e-mailed Ethan Winer and he told me the most effective place to put his RealTraps.

Some of the general rules of thumb I seem to remember are "corners" where bass may accumulate. However, my analysis is entirely too simplistic (and therefore, is probably incorrect). I would like to read Artto's recommendations on where to put bass traps (and similar devices).

Carl.

[JBP]

The 2" thick fiberglass panels you used, are they basically the same as the Pro Panels, same size and wrapped in fabric? Or did you use panels that cover the entire wall, something like 4'x 8' sheets that take the place of sheet rock?

Is using heavy, hanging fabric an option? Thanks.

[cjgeraci]

I did three things. First, the main fiberglass panels I used are fabric covered and are probably pretty similar in size (and relative function) to the Auralex pro panels (2 feet by 4 feet), except they are thicker. As Artto suggests, I used a friend with a mirror and looked for my angles of first reflection on the walls. I also put one next to one of my rear surrounds at its angle of first reflection. Initially, I wanted to make my own fiberglass panels. If you search through this section, there is some excellent advice on buying raw panels (such as Owens Corning 703/705) and making your own. It was my preference to go that route. I just had difficulty locating the raw panels to begin with in my town (St. Louis).

Luckily, the high-end audio/video store in town where I purchased my separates from (Rotel, Classe) does a lot of in-home theater installations. They contract out with a local company that makes finished panels. I went in to my AV dealer, picked out the type of panel, the type of fabric, the color, paid some $$$$, and voila, they came in in about a week. I use four of these panels. Also, aside from the covered fiberglass, the company supposedly "treats" them with something to make them either absorptive or refractive. I do not know whether that helps them or is just marketing "stuff."

Next, I bought some panels from a company called RealTraps (www.Realtraps.com). I bought two microtraps, which are also cloth-covered hi-frequency fiberglass panels (2 foot x 4 foot). I seem to recall that these panels are one inch thick. I hang one from my ceiling (that angle of first reflection), and one on my rear wall (the rear behind the speakers, TV, etc.) I also purchased four minitraps. These are essentially two-inch thick fiberglass panels (2 foot X 4 foot) that are mounted in aluminum frames. The frames allow you to put them in corners and where your walls meet your ceilings. That way, both sides of the panel works, and the panels act as sort of bass traps, in a way.

All of the panels have made a tremendous difference with my awkward-shaped and sized room (look at my profile for details). If you want to see some pics, go to my thread in this section entitled "People do not know what they are missing." Feel free to shoot me a PM if you want if you want to know what I paid, etc.

From all that I had read, the old traditional wisdom of hanging heavy fabric, drapes, will probably not give you the absorption you are looking for. It may help a little bit, but most of us need much more help than that!!

Good luck.

Carl.

[artto]

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On 6/11/2004 12:34:42 PM Colin wrote:

that's if the room is too bright, right? What about bass humps and dips?

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Not necessarily. There are many things that can cause a room to sound 'bright'. Reverberation time is just one of them (which is essentially what the absorbption is controlling). How and where the reflections are controlled and diffused, the rate of decay, the characteristic of the decay (linear, logarithmic, etc) and so on are equally important.

The bass humps and dips are typically best controlled by first getting the room proportions correct. The smaller the room, the more problems there will be & the more difficult it will be to control. The vertical corners are then the first place to begin applying bass traps. Don't forget that the room has horizontal corners too which when treated with corner absorption and can aid in bass trapping. With Klipschorns its obviously not advantageous to apply bass trapping around or near the bass horn. However bass trapping can be installed above mid/high frequency top unit. Klipsch (at Indy) uses Auralex MegaLENRD, one each, on top of the Khorns. I use a stack of MegaLENRD in the rear vertical corners.

In my own room, as part of the current acoustic upgrade project underway, I'll be installing Roxul RHT80 rigid mineral wool insulation (thank you Mike Hurd, I finally located this stuff, should work great) behind the large curved diffusors in the corners above the Khorns. These will be about 1.5 feet deep max. This should improve the effect of bass trapping even more.

Remember, what you are really doing by installing bass traps is absorbing the bass where it builds up most, in the far corners of the room so it doesn't cause cancellations in other parts of the room. Where there's a peak in the corner, there is a null in the middle of the room. By absorbing the bass 'peak' in the corner, you are essentially cancelling the null in the other area.

[DrWho]

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On 6/11/2004 11:00:54 AM JBP wrote:

How do you determine the placement and the amount of wall you need to cover when using absorption panels, Auralex Pro Panels or similiar?

I have seen applications where panels seemed to be placed in random positions and other examples where the entire wall is covered. Since there not cheap, I was wondering if they can be put on the wall spaced?

You could save a considerable amount of money if they can be placed, say 6 inches apart or more. At what point would exposed wall between the panels defeat the purpose of using them? Are there any other types of wall treatments to consider? Thanks.

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I read an article about this somewhere written by that Ethan Whiner guy (or some name close to that). Anyways, there was this long technical reason for not covering the whole wall in panels. My basic short rehash of it was that too much panels sound unnatural and make the room too dead. He also suggested that the ideal was a room with a wood floor and place the panels at "every other location"...so in the smallest space that you could fit 10, put in 5 panels evenly spaced. Doing this keeps the natural sound of the room, while also reducing the reflections and echoes and watever other terms you wanna throw out there that the panels are trying to help with

Anyways, the idea is to use as few as possible until the expected result is achieved...not only does it sound better (at least according to the dude that wrote that article), but it's also the cheapest route

[cjgeraci]

Yes, I read that article somewhere, and it was written by Ethan Winer (you nailed his name perfectly). You are right, in the perfect world, Ethan recommends fiberglass panels in the size of 2 foot by 2 foot squares evenly spaced so as to allow for some reflective surfaces and some absorptive surfaces. There is always some risk of over-treating a room versus adequately treating it to deal with how serious some of your reflection, standing wave issues are (how small the room is, the shape of the room - ideal length, width, height ratio?)

When I did my room, I tried to avoid overtreating it by leaving some gap between the panels and some wall space at the top and bottom. However, I was not that worried about too large of panels on the long wall because part of the opposite wall opens up into an "L."

Also, Ethan suggested to me to leave the rear of my room "live" without panels (behind my couch) so we would not engage in overkill unless we really had to treat that back wall. Artto, thanks for your tips on that subject because I checked yesterday and indeed, I do not currently need any treatments on my back wall.

Carl.

[JBP]

Thanks for all the input. I'm going to do a search to see if I can find the article mentioned.

What's the general rule when determining how high up the wall you treat? I'm going to have between 10' to 12' ceilings, would I need to take the panels up the entire wall? What about the bottom of the wall, at what height would I need to start treatment? Thanks for the info.

[DrWho]

I would do treatment based on where you hear a need for the panels...generally around the middle of the wall and up. As artto suggested, use the mirror trick and put panels at your first reflection points (perhaps on the cieling too). One panel where you see the right speaker in the mirror on the right wall, and one panel where you see the right speaker in the mirror on the left wall and then one panel where you see the right speaker in the mirror on the cieling. Do the same thing for the left speaker. Already you'll have 6 locations for panels where it should have an audible effect (good or bad).

Granted these are just ideas and I would suggest doing a pair at a time and move them around a bit before you permanently fixate them. If possible, find a way to mount them so that you'll always be able to move them. Sometimes it takes a while for you to soak up all the changes you've made and you will most likely want to do some tweaking once your ears have settled into the new sound. We do a lot of acoustical panel installations at work and it's always unnatural when you first start hearing the changes the panels make. You get so adjusted to the acoustics of the room before it's treated that everything (including your own breathing) sounds different after you're done and you feel like you're in a totally different room. This of course means that it will take some time again before you start wanting more from the system which means adding another pair of panels until you're satisfied.

And for the record, I would by no means consider myself an acoustical expert, but I do feel the understanding I've tried to share is for the most part correct.

[JBP]

Construction won't be finished for sometime and I'm getting the impression there isn't anyway to know to what extent the walls will need treatment until everything is set-up. I was hoping I'd be able to get a general idea of the costs for my particular room, see if I could work it into the budget, but I guess I'm just getting too far ahead.

Thanks again for all the info and advice! I'm sure I'll have many more questions further down the road. Thanks

[dbflash]

I have this saved in a folder.

I have seen these things made by a real company ($700 and up) and John Risch's website.

I am redoing my system placement and I will be placing my speakers 3 feet in front of a set of French Doors.

I was thinking about trying this, but I'm not sure.

Can someone explain if these will do anything.

Thanks,

Danny

Three evenly spaced PVC tubes behind speakers to tune them

Reference # Submitted by Submitter rating Cost

319 Wes Excellent $10.00

Source Brand

I saw this at audioasylum but can't find the link again Sort of Room Lenses

Construction

I bought a 8ft length of 2", 1 1/2" and 1" PVC pipe and two flat caps for each of these sizes. I cut the pipes into 4ft lengths so I had three 4ft sections of each pipe diameter. Then I screwed one of each size cap, using wood screws, into two 16" long pieces of 2"x6". I placed the caps about 3" apart. Just insert each pipe into its cap and you have two room lenses that you can place behind your speakers. You can stuff some insulation in the pipes if you want to keep them from resonating.

Setup

Just place behind your speakers and experiment. Believe me you will immediately hear a big difference.

Use

You will need to experiment to decide on the best placement for your room/speakers

Performance

Allows for very fine tuning of mid/treble frequencies and made a dramatic difference with slap echo in my room. If you feel your system is bright, or if you here wall reflection when you clap your hands in your listening room, try these things they are just amazing.

Other

Not my idea, wish it were.

[artto]

I will go on record right here and now saying that IMO Jon Risch is a half-baked ****** bag. He tends to slant data to suit his own priorities. And the twerp actually thinks he's developed the first fundamantally new acoustical device in 50 years. Furthermore, in my discussion with him, he claims to be in the process of recieving a "fundamental patent" on this acoustial device. There is no such thing as a "fundamental patent". Not in manufacturing, not in acoustics, not even in nanotechnology. He's all hype and little substance. Just because someone has an EE degree doesn't mean they're not capable of selling snake oil.

A simple, cheap piece of Masonite, bent into a curve will provide better performance and it's performace has been documented for over half a century. Some people seem to be hell bent on trying to 'reinvent the wheel'.

And another thing, Jon Risch doesn't seem to be able to do the math either. I've seen plenty of "kind" documentation on this from sources more knowledgeable than I.

[dbflash]

Artto,

Thank You. I was hoping you would respond.

When I get to redo my other room I plan on doing masonite curves on my walls.

I hooked up my system yesterday in front of the windows and it doesn't sound as bad as I thought it was going to. I just have to live with this for a year and then I start gutting my other den.

I was going to put curtains up over the doors, but again from an earlier post of your's I know that will be a waste of money.

I wish you would post your hourly rate on room design so I can add that into my budget for my den upgrade.

Thanks again for the ideas you have given me and to others on the BB.

Danny