Systemic Development > Psycho-Acoustics

Midrange resonance in large odd shaped room

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richidoo:
Having exonerated all my electronics as the source, I am left only with the room as the source of the ringing and shouty sound. The room has 8thnerve Adapt corner treatments which has helped a lot with tonality, and seems to have helped with the shout a little too. But it is still there and I can't figure out what is going on. On Bryan's recommendation last year I tried some GIK 244s behind the speakers to reduce SBIR. I found it hard to live with the deadening of the soundstage. Maybe because the rest of the room is so live, the absorption behind was not balanced? Many aspects of the sound did improve with the 244s behind the speakers though and I ran them that way for a couple months. Maybe the 244s are just too powerful back there. Behind the speakers they don't effect the shouty sound anyway, and that is the biggest problem now.

It seems that the more I improve my electronics, the worse the sound gets. That is not a happy feeling, especially when I am only improving electronics to get rid of the shout sound which seemed to be coming from the speakers, but now I know better. I think it is because the harmonics and dynamics are being played back much clearer and louder and are able to excite the room that much better than with the low powered Cary integrated amp.

I also got a couple GIK tri traps to try to even out a bass suckout around 65-85Hz. The two dips are very low Q so I don't really hear it. The Focus speakers specifically address mid bass suckout with a 12" mid bass driver so maybe that's why I have no problem with the bass, sounds awesome to me.

There is a lot of comb filtering, some of it 30-40dB in amplitude, and I suspect this is the harshness I am hearing. Most surfaces are in the room are hard, so there is a strong unpleasant room sound even just talking in there. It is a combo family room, kitchen, breakfast area with open passageways to dining room and hallway.

I am thinking I need more soft stuff to absorb mids and maybe some absorption on the walls of some sort. But I am just guessing, and I sure don't want to keep experimenting with treatments. I'll try one more go at it then I guess I'll have to hire Rives to come in here and figure it out.

I tried placing the 244s in various places around the room to block out reflections from reaching the listening position to isolate a source of the resonance. I put pillows behind my head and on top of my head while my daughter laughed and wanted to "do it too". I put the traps on either side of one speaker playing in mono. The resonance is just coming from everywhere. It is not one reflection. I guess that's why they call it resonance - haha.

How much hard surface should be exposed compared to soft absorbent surfaces?

I will make some new freq responses of the room with and without the Adapts, maybe we can come up with a concensus what to try? Here is the floorplan.
Thanks!
Rich

bpape:
Rich.

Put up a response chart and a waterfall chart as well as a sketch of the room.  We'll try to get it figured out.

If it's a combo to the kitchen, the hard floor in there isn't helping anything.  Also, with interior walls, a secondary issue may be uninsulated wall cavities - they can produce the kind of issue you're speaking of at certain harmonics.

Bryan

richidoo:
Hey thanks Bryan.  Wall cavities, that is very interesting! A 16" wide x 1/2" thick piece of gypsum will have a resonance and I would not be surprised if it is right in that upper mid area. The un insulated stud spacings in this room vary from 12" to 30". I can treat ceiling and wall cavities, I just can't move walls.  :wink:  I will try to make a new graph tonight.

After last post thinking about SBIR I played around with the 244 panels again, with the small BG speakers. For kicks I put the panels 4" in front of the speakers. It was muffled and sounded terrible, but I could still hear overtones of the ringing. So then I figured I got em setup, I might as well try some things. So I put them directly behind the speakers, almost touching, just enough space to let the rear port chuff, and protruding 9 inches on each side and above. Pics -> 1, 2

Voila! Now I see what you are talking about with SBIR. That midrange resonance is reduced but still a little harsh on accents, but the soundstage exploded in size on the small speakers, so about what it normally is on the Focuses. Bass is bigger and tighter. mca, you should give this a try! Piegas are thin like the BGs so you might like it. Not sure if it is a long term solution, but temporary improvement for me anyway. Sometimes you get a little surprise!

Rich

Carlman:
I hate to tell you this but our family room used to be my sound room.... and I decided to move it all to a cublicle-sized and difficult room because I couldn't cure the slap echoes and general nasties I was getting.... not with or without wife-approved treatments.  It was just too much echo and what I called 'confusing sound'  

There was a fellow in town named Bruno that had a 'foam cocoon' as an experiment that really made me re-think how a system could sound.  I started down the road to dampening... and getting rid of the room... and to where I am now.

If I had a larger room, I'd try to work with it instead of deleting it like I am now.  The next house will be just that.  And I'll probably use a combo of 8th nerve-style treatments that I make myself and some GIK-style panels that I already have.  I may modify them slightly also to be better bass-traps.  We'll see.

In any case, I think we should try to find a balance of absorption and trapping in your room that's wife-friendly and makes the system sound nice.  More time at Rich's... woohoo! :)

-C

richidoo:
Glad you are so enthusiastic \:D/  At least one of us is! I was standing in there today for a half hour just staring, thinking of what I could in there to tame it. I have radical solutions, but those aren't practical in a family house.

This morning I started talking to Julie about the possibilities. I told her about your situation where you had to go hide in the closet to get the echos under control. She said that is a great idea, and her eyes lit up with a big smile!  :D  "Will you take those acoustic things in there with you?" (8thnerve Adapts)

She wants me to buy new smaller speakers for the "closet" so she can keep the Focus out in the big room to rock out with Tory Amos and Chris Daughtry. She doesn't hear the echo and doesn't care if she did. I told her that is a great idea, except for the electronics that would also have to be duplicated. So it's an idea in the festering stage.

I started looking around the house for closets to crawl into, found two rooms. My office, and the game room. Game room is upstairs and has an adjacent wall to a kid bedroom that we insulated for sound, thikning a HT would go in there. It is the larger of the two and has the best dimensional proportions. The office is where I will be most of the time working so I would listen most there. Of course, I can listen anywhere wifi will reach so either place would work. The office is truly a closet.

Not sure I am ready to give up on the big room yet though. I was thinking that the bass response is pretty good because of the large size of the room. I really only dislike the mids which should be easier to solve than bass problems. Maybe covering up some of the sheetrock on walls and ceiling could cut it way down? There is a 1 foot deep tray ceiling directly above the stereo triangle that can be filled with FG if necessary, or at least treated in some way. I can install 1" FG panels almost anywhere in the room area, including ceiling. It is a 10' ceiling overall so there is height enough to build some kind of trimwork grid to disguise the treatments. Just not sure what is necessary for treatment.  I hope to get freq sweeps today.
Rich

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