Author Topic: Midrange resonance in large odd shaped room  (Read 9175 times)

Offline richidoo

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Midrange resonance in large odd shaped room
« on: April 27, 2007, 01:14:28 PM »
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

Offline bpape

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Midrange resonance in large odd shaped room
« Reply #1 on: April 27, 2007, 01:45:00 PM »
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
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Offline richidoo

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Midrange resonance in large odd shaped room
« Reply #2 on: April 27, 2007, 02:57:55 PM »
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

Offline Carlman

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Midrange resonance in large odd shaped room
« Reply #3 on: April 27, 2007, 05:10:54 PM »
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
I really enjoy listening to music.

Offline richidoo

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Midrange resonance in large odd shaped room
« Reply #4 on: April 28, 2007, 12:07:18 PM »
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

WEEZ

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Midrange resonance in large odd shaped room
« Reply #5 on: April 28, 2007, 12:30:15 PM »
I don't pretend to know a thing about acoustics...except that I DO know that my room is fairly 'live' also. (open concept floorplan)

I've wondered about using acoustic wall fabric like you see in some school rooms. It looks like wall carpeting, sort of. Or textured wallpaper.

WEEZ

Offline bpape

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Midrange resonance in large odd shaped room
« Reply #6 on: April 28, 2007, 12:57:49 PM »
If you JUST put up the fabric and nothing behind it of any substance, you'll kill the high frequencies and do nothing for midrange and bass response.  You'll also not do anything in terms of general broadband decay times.

Bryan
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WEEZ

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Midrange resonance in large odd shaped room
« Reply #7 on: April 28, 2007, 01:24:54 PM »
Good to know, Bryan..thanks. So much for that idea.... :oops:

WEEZ

Offline richidoo

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Midrange resonance in large odd shaped room
« Reply #8 on: April 28, 2007, 03:20:42 PM »
Some graphs:
Frequency sweeps from 20-600Hz, 600-20kHz
Impulse
Waterfall 20-750Hz, <1 Second

I did these with the small loaner speakers, but they seem to do OK above 30Hz. Black dotted line is calibrated mic at 75dB, where I set pink noise before running the sweeps. Mic is at center of my head at ear height.  Both speakers playing the sweep simultaneously. Sweep was set to 1M setting, kinda slow about 6-8 seconds for the run. The house was silent for a change. Speaker baffles were about 4 feet out from front wall, next to the Focus cabinets. I can't move those things out of the way.  :oops:  

It looks pretty good to me, a little better than last time when I had the big speakers, the small Cary amp and no acoustic treatment. The room now has fifteen 8th Nerve Adapts installed. I will run it again when the big speakers are back in order, but I am still getting the midrange reflection just as badly with these smaller speakers. Maybe you can see something on the data that shows that? I couldn't but I don't know better what to look for!! Let me know if you wanna see something else. Thanks Bryan!
Rich

Offline bpape

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Midrange resonance in large odd shaped room
« Reply #9 on: April 28, 2007, 11:32:01 PM »
FR looks decent except for a few small things that can be addressed with some bass control.

The decay times are way too high which is not unexpected consdiering the room and the treatments that are up and not up.  Most of your range is still not at -60db after a full second.  Yes it's a large room but we should be seeing closer to 0.5 seconds or so for a room that size and for a music setup.

I'd like to see the waterfall up to a couple kHz if you can just replot based on the measurements you saved (hopefully).

Also notice that about 500Hz there is an area that is in fact down 60db or more by 1 second.  IMO, that's making the midrange shout up higher sound even worse than what it is since probably the 700-1500 is most likely hanging on even longer in comparison to the range just below it.

Bryan
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Offline richidoo

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Midrange resonance in large odd shaped room
« Reply #10 on: April 29, 2007, 06:59:04 AM »
Thanks for looking it over Bryan and for your observations.

RoomEQWizard v3 only allows waterfalls up to 750Hz and only out to one second. Is ETF6 more flexible? Or can you recommend a better analysis tool?

When the sacred music show came on this morning it sounded fantastic, because the room sounds kinda like a church anyway. But I can only listen to that stuff for so long...  :?   haha

I am working on negotiating approval for putting up more panels. Is ceiling just as effective as walls for midrange attenuation? I might be able to disguise ceiling treatments better. I know I can do anything in the family room/listening area, but the kitchen is proving to be a greater challenge. Based on the position of the listening chair, on the edge of the kitchen area boundary, some attenuation in the kitchen area will probably be necessary?

Rich

Offline bpape

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Midrange resonance in large odd shaped room
« Reply #11 on: April 29, 2007, 07:20:02 AM »
Huh - never noticed that before about the waterfall restriction.  Guess that's 'cause usually we're more worried about the bottom end ringing.  Anyway, it's not a big deal - I can pretty well guess what it looks like.

Yes - a soft ceiling over a hard floor is very effective.  If you're up for a construction project, a coffered ceiling with 4" OC703 panels in the coffer centers makes for an exceptional sounding ceiling without getting too dead.

The kitchen is what it is - not much you can do about it.  If you have a closet availalbe, you may consider a couple panels on stands to put up when you're really serious about listening - they'd sit back closer to the kitchen doorway.

You'll need some things on the side walls of the space too.  You're better to put more, smaller treatments spread throughout the room rather than a couple big gobs in just a couple of places.

Bryan
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Offline richidoo

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Midrange resonance in large odd shaped room
« Reply #12 on: April 29, 2007, 09:37:02 AM »
Thanks Bryan. That is a lot of absorption! I assume you mean covering the whole ceiling, or as much as possible? Plus some more on the walls. Can it be 1" more discreet panels or should it all be 4" to shorten bass overhang also?

If I were to go with the moveable panels you suggested, exactly where would they go, you mean at the rear wall of the listening space where the cabinets are, or somewhere in the middle near the back door to the outside? Would this be as effective as the panelled ceiling?  I would guess not.  

The construction project part of it is not a big deal, but my wife has already exnayed the coffered ceiling. So I we are considering just clean square edged panels in bright white covering. I would say the chances of that are 1:100 at this point.

What about a retractable vinyl drop down sound barrier above the half wall between kitchen and LR? Did you ever see anything like that? I know Rives has done them occasionally. I could also turn the stereo 90 so the speakers are either side of fireplace.

I have another possiblity by moving the stereo to another room. If I build a rear wall I can have 1:1.14:1.39 proportions as recommended on ModeCalc.  But the total volume is only 1555cuft, compared to my current 7000cuft plus openings to other areas totalling >10kcuft. If I don't build that rear wall I would have a weird rear wall, with three different lengths but it could be treated with acoustic dampening. I can make a dwg for you if you want to see? I assume I would need new smaller speakers as I think the Focus would be too much for a smaller room. Is that necessarily true? Supposedly I would have complete and total control of this room (I am so naive)
Thanks a lot Bryan
Rich

Offline bpape

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Midrange resonance in large odd shaped room
« Reply #13 on: April 29, 2007, 11:19:04 AM »
The movables would be behind the listening position about where there would be a wall - if there was one.

On the ceiling, I'd do it primarily over the listening position.  Hang a cloud maybe 3-4" thick spaced a couple inches off the ceiling.  The idea with the coffer was that only about 1/2 of the ceiling would be absorbtion and the rest would act as a crude diffusor.  On the walls, I'm talking about maybe 3 panels on the front wall and a couple on each side wall.  We don't want it too dead but with a hardwood floor and the kitchen in play, that'll be no problem.

What would the dimensions of the new room be?  Having a dedicated controllable space is always nice but space is nice too...

If you can post a pic of the new potential space as is and where you'd put the wall with dimensions, that would help to see what we have.  Don't get too hung up with perfect dimensions - there aren't any.  All you can do is try to avoid really bad overlapping modal issues.  If it's a little less 'ideal' but gives you more space, go for it.

Bryan
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Offline richidoo

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Midrange resonance in large odd shaped room
« Reply #14 on: April 29, 2007, 07:59:16 PM »
The cloud in the listening area sounds good. I have a tray ceiling above the stereo triangle, it rises up a foot higher (11') than the rest of the downstairs ceiling, making a pocket which could contain treatment very inconspicuously, even coffer could work there.  You can see the line where the 11' ceiling tray is, would cloud inside there be sufficient? Would you recommend 100% cloud coverage, or spaced out to a lower percentage of coverage? Would there be too much deadening with 4" FG on ceiling?

I am more worried about deadening the front wall where you mentioned you would place 3 panels. That seems to the the magic area where hard and flat makes the music come alive. When I tried 244s against the front wall behind speakers I lost the soundstage completely, even though the actual direct sound was improved. tritraps on the floor same thing. That front wall wants to be bare ass naked. So not sure how absorption on the front wall would best be applied to avoid the deadening and loss of soundstage. It really all comes down to the waterfall, that is the teller. Do you use RplusD Bryan? What do you use to see waterfall at 2k?

I'll get some pics and a drawing of the other space up tomorrow. Carl thinks it is a winner too, he has seen it. The dimensions are roughly 21'10" (total length including foyer at rear, wall could be at 16' 1" or less) x 11'8" wide x 9'11" tall. Semi vaulted ceiling with a 5'+ wide flat at top. Open staircase at rear.

I wonder if the Focus speakers won't be too much for that small space. They can easily fill 7500cuft with clean loud sound, this is only about 2000cu max. Some Focus users have had to sell their monsters because they couldn't tame the bass in a small room. Other rave reviews were in a tiny room. I will haul them up there to find out eventually. I'll have a small system up there tomorrow for a test drive :)
Rich