How many panel traps

mca · « **on:** 8 Nov 2005, 11:32 pm »

I just installed eight 2' x 4' x 4" panel traps in my 14' x 18' x 8' room. I have one in each corner of the room, one behind each main speaker and one on each side wall for the first order reflections. The room sounds better, but not as good as I had hoped. How do I know if I have enough panels in there? Or too many?

zybar · « **Reply #1 on:** 9 Nov 2005, 12:15 am »

Quote from: mca

I just installed eight 2' x 4' x 4" panel traps in my 14' x 18' x 8' room. I have one in each corner of the room, one behind each main speaker and one on each side wall for the first order reflections. The room sounds better, but not as good as I had hoped. How do I know if I have enough panels in there? Or too many?

What are the panel traps made of?

Do you have them spaced off the wall? They are most effective with 2-4" of space between the panels and wall.

How did the sound improve?

When I added into my room 8 MiniTraps from Ethan at www.realtraps.com I was able to hear and measure a difference.

In my room I have one trap in each of my three corners (fourth corner is an opening) plus one trap centered on the wall way behind me, plus two at the midpoints on the sidwalls angled between the ceiling and sidewall, plus two on the front walls.

George

mca · « **Reply #2 on:** 9 Nov 2005, 12:42 am »

According to the GIK Acoustics website "4" inch thick 8 pounds per cubic square foot acoustic mineral treatment.

The frame extends about 2" out the back, so the treatment itself is off the wall.

The sound got a little tighter and a little less "lively".

ctviggen · « **Reply #3 on:** 9 Nov 2005, 01:12 am »

The GIK stuff is interesting -- much cheaper than RealTraps, but not as nice looking (at least through pics). There's no data on their site about what the product's absorption is. There's reference to an NRC here:

http://www.gikacoustics.com/faq.htm

But there's not even an NRC I can find. They do seem to weigh close to the same, though.

mca · « **Reply #4 on:** 9 Nov 2005, 01:43 am »

The GIK panels are not that bad looking and for the price. I figured it was better than trying to make my own since I could not afford any of the big name stuff.

What is NRC?

I would like to take measurements with and without the traps in my room, but not really sure how to go about doing it

I figure I need a disk with test tones, my trusty rat shack meter and some graph paper. Is there somewhere online that explains how to do this? Is there a source I can download tones and make my own CD?

ooheadsoo · « **Reply #5 on:** 9 Nov 2005, 02:14 am »

Real traps are afaik much more than just a panel of acoustic absorbent material. It also combines resonating panel trap technology, I believe. All in all, quite different from a slab of fiberglass.

flatmap · « **Reply #6 on:** 9 Nov 2005, 04:34 am »

I looked here <http://www.gikacoustics.com/ordernow.htm>. It says there that the NRC is .60 for the GIK 242 and that it has the same NRC as the GIK 244 from 4000Hz down to 250Hz. I guess the 244 has a bit more NRC at 125Hz; it's the one recommended for corners.

mca, did you get a mix of the 242 and 244? Maybe it's worth trying all eight in the corners and seeing if that makes a difference?

Red Dragon Audio · « **Reply #7 on:** 9 Nov 2005, 07:37 am »

I like Flatmap's idea of trying all 8 of them in the corners only. (flatmap he has the 244's which are 2'x4'x4").

You'll end up with 8' tall, 4" thick corner bass traps but no first reflection point absorption.

Get a couple packs of the 242 panels to experiment further in your room.

Take your time and experiment with different arrangements. Live with one for a week. Change it up the next week. Get a feel for and handle on what different placements do for your particular setup.

You may also experiment with seating position as well as it may need to change with new treatments.

Acoustic room treatments are very worthwhile but do require a modest amount of work and experimentation. It would be nice if they could just be plopped in the perfect spot the first time. Ahh life would be easier...

Good luck and have fun! Report back with pictures and your experiences.

ctviggen · « **Reply #8 on:** 9 Nov 2005, 11:46 am »

NRC:

Noise Reduction Coefficient (NRC)

The NRC of an acoustical material is the arithmetic average to the nearest multiple of 0.05 of its absorption coefficients at 4 one-third octave bands with center frequencies of 250, 500, 1000, 2000 Hertz. The NRC rating can be viewed as a percentage (example: .80 = 80%) of what soundwaves that come in contact with the acoustical material are absorbed by the material and NOT reflected back within the room.

From http://www.acousticalsolutions.com/education/glossary.asp.

The NRC is basically a simple way of saying how a material absorbs sound, but it's only good at those certain frequencies. It's better for things like how wall construction will affect sound absoption than for traps for music. RealTraps is good because you can go look at the data for each of the products you might buy.

ScottMayo · « **Reply #9 on:** 9 Nov 2005, 02:01 pm »

Quote from: heavystarch

Acoustic room treatments are very worthwhile but do require a modest amount of work and experimentation. It would be nice if they could just be plopped in the perfect spot the first time. Ahh life would be easier...

They can be - though I don't know about "easier". It's possible to model the response of a room and then simulate the effect of adding traps. In my experience, the result tracks reasonably well with what really happens.

It beats hauling around traps; it doesn't save much time otherwise, though. I've spent an awful lot of time hunched over the computer, modelling and tweaking some rooms.

woodsyi · « **Reply #10 on:** 9 Nov 2005, 02:20 pm »

I just did what was recommended on Ethan's site. I did use the mirror trick to line up the early reflection points for his micro panels. I also stuffed all four ceiling corners with 12" bat above the ceiling tiles and changed all ceiling tiles with 1/2" thick ones that are rated at .55 NRC (I would think of 1k and 2k Hz). I know the treatment absolutely improved the sound in my room.

Ethan Winer · « **Reply #11 on:** 9 Nov 2005, 04:39 pm »

mca,

> What is NRC? <

Bob gave you the definition, and I'll add this:

NRC is much like an absorption coefficent, except it considers the "speech" frequency range only. An absorption coefficient is basically a percentage of absorption, but it has a serious failing - a panel that's only 1 foot by 1 foot will have the exact same value as a panel that's 8 feet by 8 feet. That is, AbsCo does not take into account the size of the device, and by extension doesn't tell you how much total absorption you'll really get.

The base unit of absorption is the Sabin, and absorption coefficients are derived by dividing Sabins by the square feet of front surface area. Using Sabins has the advantage of stating exactly how much absorption a given device really offers.

Another failing of absorption coefficients is they do not include the edge surface, which can increase a trap's absorption quite a lot. For example, with a panel that's 2 by 4 feet and 4 inches thick, the edges add 50 percent more absorption compared to the front surface alone. Sabins tells this, but absorption coefficients do not.

> I figure I need a disk with test tones, my trusty rat shack meter and some graph paper. Is there somewhere online that explains how to do this? Is there a source I can download tones and make my own CD? <

There's a "CD" you can download on the RealTraps site. Note that this tells only the raw low frequency response. Just as important is measuring low frequency ringing, but that requires more sophisticated tools like ETF.

--Ethan

ctviggen · « **Reply #12 on:** 9 Nov 2005, 04:53 pm »

Ethan's right, and this is one reason I'm waiting to make the jump to electronic room response correction -- the latter cannot get rid of modal ringing. I'm going to wait until I'm happy with my room's reponse, then make the jump to room correction.

warnerwh · « **Reply #13 on:** 9 Nov 2005, 11:39 pm »

Bob: Recently I purchased the Behringer DEQ 2496. My room is LEDE with 3 large bass traps. The improvement with the DEQ 2496 was as dramatic as the room treatments. Very important and for the 300 bucks including a mike I know of no other deal in high end audio that does so much for so little. I can't imagine the sound really getting any better until my system can read my brain waves and alter the recording engineers opinions to my own. My point is that even with good room treatment that even the lowly Behringer made a large difference. It's my opinion at this point that no system should be without one and for people in who's system they can't add room treatment for whatever reason that the Behringer is a gift from heaven.