Too much absorption on the real wall?

Nils · « **on:** 24 Jan 2008, 09:38 pm »

When listening to my system, I notice a livelier, more enjoyable sound when standing up than sitting down. By listening with my head cocked to one side, I've figured out (99% positive) that it's due to the 2' x 4' MiniTrap HFs on the real wall behind me. When I sit down, my head is positioned exactly halfway up the trap height. That is, there's virtually no audible reflection from the rear wall. When I stand, my ears are closer to the top of the trap, and I hear some indirect reflections from the upper wall behind me.

What to do? My seating position is 5' from the rear wall, so perhaps I can use standard MiniTraps? Pure diffusion is too reflective, but I'd like a semi-diffusive surface (a la RPG BAD panels)? Any recommendations?

Thanks,
Nils

bpape · « **Reply #1 on:** 24 Jan 2008, 10:12 pm »

A panel that still assists in minimizing low mid/bass frequency absorbtion but reflects more of the highs sounds like what you want. A standard mini-trap (not HF) will do that.

Bryan

Ethan Winer · « **Reply #2 on:** 25 Jan 2008, 05:35 pm »

Quote from: Nils on 24 Jan 2008, 09:38 pm

When listening to my system, I notice a livelier, more enjoyable sound when standing up than sitting down.

My usual advice is to live with the HF absorption behind you for a while and see if over time you come to appreciate that the sound is actually cleaner and more pure. My other usual advice

is to line that wall with two to four diffusors. With diffusors you can retain the liveness while avoiding the more damaging aspects of comb filtering.

--Ethan

8thnerve · « **Reply #3 on:** 25 Jan 2008, 08:55 pm »

Or you could try treating the corner areas and leaving the rear wall plain.

Onlythat · « **Reply #4 on:** 20 Feb 2008, 06:51 pm »

I noted a similar effect. I recently took delivery of a pair of 244 panels and two tri-traps-- just gtetting my feet wet in Gik-land. I put the tri-traps in the front corners as suggested by the guru himself, Bryan. And I have placed the 244's on the wall behind me. No issues with the corners as I already HAVE the Eighth nerve corner pieces in place and a few seams as well!!
I have noticed a smoothing out of the bass response and more definition thus far but may-- and I repeat MAY- be troubled by a slight diminution of midrange/treble energy/'smoothing' of the proceedings. Things certainly sound more 'relaxed' and less confused though-- just a bit dull for my tastes perhaps.
Now-- one could argue I am used to an untreated rear wall and therefore the 244's are simply smoothing things out and making them more neutral and I need to get used to this-- Maybe. I'll play a bit more this weekend.
I really wanna try the 244's behind each of my speakers as that is supposed to be my next move according to the the good Mr. Pape. We shall see...
I have also tried placing one 244 horizontally on the floor to act as a bass trap behind my seat (a tri-trap wont fit) and a 244 behind my head (havent yet nailed anything to a wall). I may prefer the 244's end to end behind my head to this arrangement.
Wish I had a frequency response meter and some aptitude for measurement-- that'd serve to confirm or deny what exactly I'm hearing. Bryan-- I had a very pleasant chat with Glenn yesterday-- another Gikster and a very friendly guy. But feel free to jump in here if you will...
Ethan's advice to 'live with things a while' may be a good idea as well...

bpape · « **Reply #5 on:** 20 Feb 2008, 06:56 pm »

Yes - it can be a very different effect than you're used to. Something behind your head other than a purely reflective surface is a matter of preference. Some people like it, some people don't. The idea was to help minimize bass buildup since you're close to the rear boundary.

Live with them a while and see what you think. Then, pull them down and listen. After you understand the differences, I'd agree to try them straddling the wall/floor behind your seating. That may be a good compromise depending on your personal taste.

Bryan

Onlythat · « **Reply #6 on:** 20 Feb 2008, 07:38 pm »

Bryan-- I'm gonna try them behind the front speakers this weekend as well-- that may help with any "comb filtering" effects as I understand it (partly-- mostly from ASC website). The Tri-traps in the front corners do seem to improve things.

Not sure if the 244's will fit behind the couch straddling the wall/floor interface as they are supposed to. (couch more than say 8 or so inches from the wall makes the room look tiny and me sit right up near the speakers)
Would they work as well just sitting horizontally on the floor flat against the wall? Or do I need to kinda lean them up against the wall to straddle the interface?

I could also try them in the two rear corners, eh? So I'd have two tri-traps up front and the 244's in the rear corners. You didnt recommend anything for the rear corners in our mini 'plan'-- just possible bass trapping behind the couch and my head; then tri-traps up front in the corners and 242's behind each speaker and in between them (that may not be possible owing to the flat screen and rack between them).

I'm assuming you wanted to save me some dough (thanks)-- but I also assume you feel treating all four corners as well as the front wall is best when/if possible, eh?

richidoo · « **Reply #7 on:** 20 Feb 2008, 10:28 pm »

I borrowed a couple 2'x6'x2" BAD panels from the local dealer on demo. I put my face into them and yelled, and clapped. It was not dead, it just sounded natural, smooth, almost like outdoors, but with very warm fuzzy feeling of bass absorbtion. I put them against the front wall between the speakers. No midrange reflections, and no dead feeling. The increase of low level detail was very surprising even with the rest of the room mostly untreated except for some corner bass trapping. When I put it only a couple feet behind my head it was fine. No dead feeling, and greatly enhanced details. Listening with my head 3 feet in front of it was not a problem, I couldn't hear it at all. The problem with BAD is the price.

It is great for special spots, but maybe not for covering all walls.
Rich

bpape · « **Reply #8 on:** 20 Feb 2008, 10:56 pm »

Try leaning them behind the couch as much as you can. You can also try them straddling the rear corners but that'll be dealing with a different issue.

Take a good long listen to the same stuff with each of the positions so you understand fully what each is doing. I wouldn't do any more until you have a better handle on what YOU like and what works for you in your room with the seating position limitations

Bryan

youngho · « **Reply #9 on:** 21 Feb 2008, 01:34 am »

Clearly, some of these acoustic panels need break in. The principle is not unlike that in cable, electronics, and speaker break-in. Simply play the system at high volumes for 100+ hours. As you listen over time, you'll notice significant changes in detail, soundstaging, "air," pace, rhythm, and tempo.

Happy listening,

Young-Ho

(edit) I'm sorry about any confusion, I meant to add the following characters to my post to clarify: ^_^

bpape · « **Reply #10 on:** 21 Feb 2008, 01:43 am »

satfrat · « **Reply #11 on:** 21 Feb 2008, 01:57 am »

The only thing breaking in here is the listeners ears.

mcallister · « **Reply #12 on:** 21 Feb 2008, 02:32 am »

Quote from: bpape on 20 Feb 2008, 10:56 pm

Try leaning them behind the couch as much as you can. You can also try them straddling the rear corners but that'll be dealing with a different issue.

Take a good long listen to the same stuff with each of the positions so you understand fully what each is doing. I wouldn't do any more until you have a better handle on what YOU like and what works for you in your room with the seating position limitations

Bryan

Hey Bryan,
What different issues would straddling the 244's in a corners deal with?

bpape · « **Reply #13 on:** 21 Feb 2008, 02:37 am »

Straddling the rear corners will deal (based on close seat proximity) with width related issues and some length axials and some tangentials. Behind the couch is more height related and general boundary issues. Flat on the rear wall behind the head is for boundary issues and specifically nulls off the rear wall.

Bryan

Onlythat · « **Reply #14 on:** 21 Feb 2008, 05:45 am »

Bryan-- check this pic out:

http://stereophile.com/musicintheround/706mitr/index1.html

just scrolldown a bit after clicking the link and check this panel placement.

Makes me realize that when I first placed the panels along the rear wall, side by side, just above the back of my couch (on makeshift stands) they were actually above my ear level-- as the back of my couch/pillow already comes up higher than my head/ear level (it's one of those deep couches you sink in to). This arrangement seemed decent enough.

However-- I noticed more dulling of things when I let one panel rest on the floor (as a 'bass trap') and stacked the other on top of it horizontally. This puts the upper panel partly behind the couch and partly above it. It's possible then then that since I've got a thick pillow AND padded couch-back behind my head already-- a panel in addition is just a bit much, no? This does gel wth some peoples' rec for a 'bit' of absorption behind the head if close to a wall (I know it's down to preference and that, as always).

Finally, does arranging acoustic panels on the rear wall ABOVE the listeners' head as in the picture in the link deal with anything in particular?

thanks.

bpape · « **Reply #15 on:** 21 Feb 2008, 06:23 am »

If you already have a pillow and chair back behind your head, it's not the normal issue people have which is the negating the higher frequency reflections off the rear wall - which you've already killed.

If it was me, I'd try the 2 BOTH on the floor behind the couch straddling a bit and see what you think.

Bryan

Onlythat · « **Reply #16 on:** 21 Feb 2008, 08:38 pm »

Thanks Bryan-- will do.

This weekend I'll have some time to screw around with them and I'll try them behind the couch as well as placing them behind the speakers along the front wall and in the rear corners while I'm at it.

If I like it-- I'll order some more from you-- maybe another set of tri-traps or something for the rear corners or whatever.

BTW-- I am still curious what you think of that picture I posted a link to-- does that placement treat anything in particular?

nathanm · « **Reply #17 on:** 21 Feb 2008, 10:40 pm »

You really should notice a difference in the "air" as the panels break in. The music should be loud enough that a cloud of fiberglass dust emanates from the panels.

GregN · « **Reply #18 on:** 22 Feb 2008, 05:22 pm »

ok, "BAD" stands for what now? Guessing, is it "broad absorption dampening"? I must've missed the forum FAQ sticky on this.

GregN · « **Reply #19 on:** 22 Feb 2008, 05:40 pm »

Nevermind. I figured it out. My friend Google hooked me up.