Experimenting with room treatment

dragon1952

I recently read where my Martin Logans could benefit from sound absorbtion behind them. I really don't want to spend hundreds on anything at this point but thought I'd experiment with a less expensive option.
I bought 2 cases of these Auralex Acoustics SonoFlat Acoustic Absorption Foam, in the 2" x 12" x 12" size. They are only $80 for a case of 14 panels and with some rewards and rebates I had available on Amazon I got 2 cases for under $60.
The next step was to figure out how to attach them to the walls. I decided to go with some 1"x 24" x 48" styrofoam panels and mount the acoustic foam squares to them. They were the perfect size to fit exactly 8 of the 12 x 12 squares to and I figured I could possibly hang the styrofoam on the walls using some picture hangers or something like that so I wouldn't do any permanent damage to the walls. Plus it would allow me to move them around easily if needed. However, after some research I decided to go with 1 3/4" T-Pins. These make very small, pin-size holes in the wall and secure the styrofoam very well. I could then just glue the acoustic panels to the styrofoam.
Here are some pics of my progress so far. As you can see, the left wall is wider than the right wall so I'll have to come up with a solution on that side which will likely just involve some trimming.

dragon1952

The cool thing about mounting the panels onto the 1" styrofoam is that it gave me an extra inch of sound absorption.

vmaxer

Did improve the sound?

Joey_V

Which Logans do you have?

dragon1952

This is a project that isn't finished yet. I'll update with results later next week. I had to order more panels. Also, I'm not sure how well this set up might work for other speakers. Supposedly this particular 2" acoustic foam doesn't work well enough for bass traps as it doesn't absorb frequencies in the bass/sub-bass range all that well. I'm not sure how much the extra 1" of styrofoam might help in that area, if at all. I'm more concerned with the reflection from the panels off the back wall.

BlueMDPicker

I believe Roger Sanders is credited with the design of the curved panel ESL's at ML. I don't know what his placement philosophy is for them. But, with respect to his later designs (Innersound and Sanders Sound) hybrid ESL's (flat ESL panels), here is the placement philosphy from the products manual:

Joey_V

Be careful about absorbing an uneven frequency spectrum, thin panels or foam with poor absorptive characteristics will take the highs out of your room and leave you with an uneven low midrange and bass.

verb

dragon1952 wrote: »

This is a project that isn't finished yet. I'll update with results later next week. I had to order more panels. Also, I'm not sure how well this set up might work for other speakers. Supposedly this particular 2" acoustic foam doesn't work well enough for bass traps as it doesn't absorb frequencies in the bass/sub-bass range all that well. I'm not sure how much the extra 1" of styrofoam might help in that area, if at all. I'm more concerned with the reflection from the panels off the back wall.

Looking good so far!!! I plan to do something similar eventually.

dragon1952

BlueMDPicker wrote: »

I believe Roger Sanders is credited with the design of the curved panel ESL's at ML. I don't know what his placement philosophy is for them. But, with respect to his later designs (Innersound and Sanders Sound) hybrid ESL's (flat ESL panels), here is the placement philosphy from the products manual:

Yeah I did read that 1st part re: the sweet spot and that is the only position I listen from in this particular set up. As for distance to the walls, I'm not familiar with the Eros but just about 100% of what I've read on these says to give them lots of space. I've used the Cardas method of speaker placement in the past and he indicates a further distance from the back wall (the wall the back of the speaker is facing) quote, "Panel or dipole speakers such as Apogees and Magnepans cancel their side waves, so a formula of .618 x the ceiling height can be used for determining placement from the rear wall. Most box speakers radiate low frequencies in all directions thus a formula that places the speaker to rear wall distance at 1.618 the side wall distance should be used." As for the flat panel design Sanders says, "Using a flat panel also results in much less reflected sound, since the bulk of the energy is radiated directly at the listener, minimizing interference from the room's boundaries. "

Since these are hybrids I used a distance closer to the Cardas recommendation for 'regular' speakers and have them around 4.5 ft out from the wall, and a tad over 2.5 ft from the sides. Unfortunately the only room I have available to me is only 10 ft wide although it has good length of 19' and a 9' ceiling.

dragon1952

Joey_V wrote: »

Be careful about absorbing an uneven frequency spectrum, thin panels or foam with poor absorptive characteristics will take the highs out of your room and leave you with an uneven low midrange and bass.

The only data I've found on these acoustic panels indicate a fairly even absorption between around 500 Hz to maybe 10K Hz but, quote " Riverbank Acoustical Laboratories is accredited to perform sound absorption coefficient measurements for the frequency range of 100Hz to 5,000Hz. However, we calculate sound absorption values at additional test frequencies as a service to our clients."
So their measured/calculated absorption coefficients between around 475-10K Hz appear to only vary within a range of 1 to 1.2 with a very sharp drop-off starting at around 500Hz and below.
I'm flying by the seat of my pants here and have no idea what I'm doing or what the effect might be but for under $100 I'm willing to experiment. But all indications from what I have read is that these speakers could potentially benefit from some sound absorption behind them.

SCompRacer

I had flat panel ESL's for several years and tried numerous combinations. Rear wall absorption will improve soundstage and focus at the expense of narrowing the sweet spot.

The further they are into the room, you deal with delayed rear reflections and comb filtering. InnerSound/Sanders ESL's had an active xover bass amp with an eight foot long folded transmission line bass enclosure that really delivered articulate low and accurate bass.

When boxed by corners they created a serious bass problem to deal with. No way could I have anything but amps between the InnerSound ESL speakers when boxed by corners. A turntable between the speakers boxed by corners would start to feedback around 70dB.

Yes, Roger did invent the curved panel but didn't have the coin to patent it. He preferred the flat panel rather than the curved.

I had to use stacked GIK bass traps in corners when they were corner loaded. They did best on an open wall. I experimented with vertical and horizontal panels behind the speakers too.



This setup had the right speaker on an open wall. There was just a small chimney corner by right speaker before opening into the rest of main level.



This shot gives you a glimpse of the main level beyond right speaker.

dragon1952

What's with the kangaroo? :^ )

dragon1952

But seriously........I don't quite get the concept of leaving open wall spaces between the panels? I know this is typical but wouldn't it be better to have the entire back wall deadened acoustically?

SCompRacer

dragon1952 wrote: »

What's with the kangaroo? :^ )

That's my listening buddy, Jasper. He is one cool cat. He is a Texas hybrid transplant, loves a warm amp.

dragon1952

He's got a really long tail!

SCompRacer

dragon1952 wrote: »

But seriously........I don't quite get the concept of leaving open wall spaces between the panels? I know this is typical but wouldn't it be better to have the entire back wall deadened acoustically?

I couldn't commit to full rear wall treatment. My buddy Norm (RIP) had the entire back wall treated with his ESL's and I didn't like it. No sparkle so to speak. I was in a listening room that was covered -ceiling and all four walls- with Owen's Corning with speaker fabric over it. He had ML ESL's. IMO think you can go too far with acoustic treatments. Room sweeps help identify frequency dropouts or accentuation which show what you need corrected. You may not achieve totally flat response, but can minimize the peaks and valleys so you don't get hints or severe over attenuation of specific frequencies.

ALL212

You think that wrapping his sound damping onto the other wall will help? That was what I was looking at. Might not create a "bass trap" but still might assist. Otherwise you've got the outside walls bouncing stuff around as well.

dragon1952

SCompRacer wrote: »

Room sweeps help identify frequency dropouts or accentuation which show what you need corrected. You may not achieve totally flat response, but can minimize the peaks and valleys so you don't get hints or severe over attenuation of specific frequencies.

Yeah, this is all likely pretty useless without knowing specifics.

ALL212

In order to do what Rich is suggesting you'll need equipment. Some kind of mic with analysis equipment. But I think you're on the right track with what you're doing. I would also add sound damping to the side wall as well. I don't think you'll need to come out more than 2 blocks of damping.

machone

My experience with room treatments is my room (19 x 23 x 9 on a slab) needed many panels before I got the desired results. I now have 18 panels total. 14 bass traps (4" thick) and 4 first reflection (2" thick). I used Owens Corning 705 on open frames (nothing covering the sides). Using open frames adds a lot of surface area (50% for bass traps if you only count the front of the panel) making it easy to kill the highs. Over half of my bass traps have FRK (foil back paper) on the outside face or faces to keep the room live.

It is a lot of work. A lot of trial and error. But now the room is under control and small tweaks now make a big difference in imaging.
-Bass is much improved; very tight and powerful.
-Imaging is amazing; speakers disappear and the sound stage is as wide and tall as the room.

I have never run a sweep. I have the mic and programs but never got around to it.......

http://forum.polkaudio.com/discussion/177293/acoustic-panel-build#latest