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Discussion Starter · #1 · (Edited)
I caught the upgrade bug this year and decided to go from 5.1 to 7.1 to 9.1 to 11.1 :gulp: and buy or build some larger subs. I sold my 7.1 pre/pro and one sub and bought some extra surround speakers. Long story short, I am now wired and "speakered" for up to 11.1, but have not yet purchased a new receiver or subs. I am stalled partially due to funding but also due to the realization that I need to improve my room acoustics first, or I may just be wasting money on equipment upgrades. I think now is the best time to do it, but I want to throw a few ideas out there and get some feedback before I start. For reference, there are some fairly recent photos of my room here (latest photos toward the bottom). The panels on the side walls are 2 inch thick OC 703 and they are flush mounted. The placement is based partially on aesthetics, and partially on the first reflection points of an earlier seating arrangement. To give you an idea of my starting point, I have included some REW measurements below.

Measurement Graphs
The graphs represent response from several different system configurations (including several different subs in different locations, several different receivers/processors, and a few different main listening positions). These measurements were all taken without EQ or room correction applied. The side wall panels were installed before all of these measurements.

Full Range Frequency Response


Bass Only Frequency Response


The waterfalls correspond to four of the FR curves on the graphs above

Waterfall 1


Waterfall 2


Waterfall 3


Waterfall 4



Based on listening/measuring, my target areas are (in this order):

1st - 30-60Hz
2nd - 100-200Hz
3rd - 200-1kHz (if it is still an issue after treating 1 & 2)


So here are some ideas I'm kicking around...

1. Double the 2" panels on the side walls (2 panels each in a 4" deep wood frame) and mount them with a 2"-4" air gap to the wall (meaning the frame is open front and back).

2. Add diffusers between existing panels on side walls. My initial thought would be the 2'x2' DIY wooden QRD "skyline" diffuser panels - 4 total.

3a. Triangular bass traps in the rear corners (can't do front corner placement due to existing doors). I'm thinking DIY, either mineral wool or pink fluffy, probably about 4' tall with a 24" wide face.

3b. OR move the side wall panels closest to the back wall into the back corners and make them thicker (i.e. like step 1 - 4" or 6" thickness) for bass trapping.

4. Add damping to the 1st ceiling reflection, probably 2 or 3 panels, 2" or 4" thick, something similar to what I end up with on the side walls.

5. Damping/Diffusion behind front speakers? This is a maybe since I plan to cover the entire front wall/doors with heavy curtains, mostly for aesthetics/light reflection.


Ideally I would have the budget and time to do all of these, and maybe someday I'll get there. I guess what I'm looking for in terms of feedback is - if I could pick two, maybe 3 to do first, which will give me the best bang for my buck? I'm thinking 3a, 1, and 2 in that order to start. I assume triangular corner traps are my best bet for the 30-60Hz range. Will they be effective in the back corners if my subs are at the front of the room? Will option 1 improve my 200-2kHz response, or will the difference be negligible?
 

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Re: Acoutic Treatment Phase 2

5a. Damp the entire front wall to address reflections from the surrounds messing up the front soundstage.

In the rear, stay with the triangular chunks. Better performance for the same $$$ as 6" straddling.

Side wall panels - going to 4" is good. Probably a 2" gap is fine.

I would do side wall and corners first. Diffusion probably last.
 

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Re: Acoutic Treatment Phase 2

Generally speaking, yes. 2' will be fine. You can go thicker but I'd want to know what else is going to be going on in the room overall.

Bryan
 

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Discussion Starter · #5 ·
Re: Acoutic Treatment Phase 2

Thanks again Bryan. I think I will start with options 3a and 1 as suggested, and decide what is needed from there. Front wall treatment would not be too difficult, and sounds as though it would be worth the effort. That may be phase 3 for me.
 

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Discussion Starter · #6 ·
Gave it some thought and kicked around the idea of building my own bass traps, but the longer I think about it the more he GIK tri-traps look like the way to go. I ordered a couple fabric samples this week, to get the color right. This will most likely be the next purchase for my HT. After that I'm going to get some pre-built 4" deep frames and 6 more 2" panels to expand my side wall absorption panels.

Bryan - what's the best way to mount tri-traps to the wall (sheetrock)?
 

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Tri Traps have no provision to mount. They're designed to sit on the floor and stack. If you need to get them up, you'd just need to build a small corner shelf for them to sit on.

Bryan
 

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Discussion Starter · #8 ·
Old thread here but I'm finally ready to pull the trigger on some acoustic updates. I want to get this done correctly before the subwoofer and Atmos upgrades I'm hoping to do possibly early next year. I'm going to forgo the DIY option and get GIK 244 panels for the side walls first and re-evaluate. Next step will be tri-traps in the back corners if needed.
 

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Both are good things to do. Which first is personal preference.
 

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Discussion Starter · #11 ·
My panels arrived last week and I installed them over the weekend. Installation was pretty easy. I used two screws with Sheetrock anchors per panel. The only real time consuming part is measuring for screw/hook locations on the wall and keeping them lined up and level. Each panel hangs with a wire across the back like a large picture frame (which also allows for easy height tweaking). As you can see I have three panels on each side wall positioned to catch first reflections from the left, right, and center channels for all seating positions. I kept my 2" thick DIY panels and have them stacked in the back corners to see if they'll help a bit with bass trapping as well. I have not had a chance yet to do any listening or measurements but I plan to do that pretty soon and post results here. Stay tuned! In the meantime, enjoy some poorly lit phone camera pictures!




image-2594718269.jpg



image-4195889246.jpg
 

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Discussion Starter · #12 ·
Ok, I've hung my new panels, moved some things around and taken some new REW measurements. With reference to my original post, I'm still focusing on my first target (30-60Hz range), even though it's not the only issue.

First - what I've changed. As stated above, I mounted 6 GIK 244 bass traps and moved my existing 2" panels to the back corners (stacked 3 deep for 6" thickness in each corner). I currently also have the privilege of borrowing a pair of Chane SBE-118 subs for an upcoming review, so I decided to see if dual subs could help with some of my problems. Turns out it helped more than anything I've tried so far, but I'm not convinced I'm anywhere near done with acoustic treatments. After trying a bunch of different configurations and EQ settings, I settled on placing the subs in the back corners of my room, and adding a boost at 18Hz on the Dayton amp. Below is a comparison of the single sub responses (various locations in the room) to the dual sub response I'm getting now.

Measurement Graphs

Single sub, 2" panels (x6)


Dual sub/rear corners, GIK 244 (x6) plus 2" panels (x6)




The good news: response from 20Hz up to almost 70Hz is about +/-3dB (compared to +/-10db worst case before). It sounds much better at the MLP too, of course.

The not great but not surprising news: this confirms my suspicion that dual subs are basically a necessity for me.

The bad news: issue #2 (100-200Hz) response looks awful, if not worse than before. Moving the mic around the seating area didn't make any major improvements in this area. I had anticipated the 244 panels to improve response in the 100-300Hz range a bit more than I'm seeing. How much do panel quantity, panel placement, speaker placement, and seating placement effect response in this region? I guess what I'm getting at is, do I need to add more panels/bass traps or is the room arrangement at play? Just to clarify, I have not bothered trying to EQ the big dip. I have tried 2 or 3 different speakers with similar results here too, which makes me think it's almost completely a room issue. I know room correction and EQ is always an option, but I personally want to get the room as good as I can without the use of EQ.


edit: I should add that I have tried different sub crossover and phase settings as well, and nothing made much of an improvement without messing up response above or below. I also added a waterfall graph for the current setup.
 

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Looks to me like the bottom end of your current trough might be a phase issue between mains and sub(s). Try reversing the phase on 1 then on both of them and see if you can at least get a part of it better. Above that it's likely boundary related phase issues (SBIR).
 

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Discussion Starter · #14 ·
Bryan - thanks for your quick response last week. I had some time last night to move things around a bit and take more measurements.

First, I tried reversing polarity on just one and then both subs. It did nothing to help the trough from crossover up to about 200Hz, and made things below 50Hz much worse. I played some more with the crossover settings and PEQ but couldn't get even marginal improvement in that area.

Since you mentioned SBIR, I took a quick look at GIK's page on the subject. I tried moving my loose 2" panels behind and beside the main, in the front corner, and on the side wall at the front of the room. It didn't seem to help much, but I wasn't being very scientific about it. Throughout the process I have tried two different types of speakers for the mains and a few different mic positions within the seating area.

After a while of that, I took measurements of the subs alone and the speaker alone. The sub-only curve looked very good up to 120Hz or so. The main-only curve still had the awful dip. I tried moving the main side-to-side a couple feet, and even about 2-3 feet into the room (very unpractical placement) and it did change, but I wouldn't call it better. See the graph below for before and after. The pink trace is the normal spot, pretty close to the front wall, on either side of my TV. The blue trace is probably about 30-36" out from the front wall, and probably about 2-3 feet from the mic.



I'm coming to the conclusion that my room dimensions combined with speaker placement are causing some major issues. Is it too much to correct with more bass trapping? I don't have much freedom with placement of the main speakers. Sub location is pretty flexible, but they seem happy in the back corners.
 

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If the sub is OK and the mains are bad, then either positioning or you need to work with thicker panels on the front wall or side walls pending where it's coming from. It's possible that you had problems in that general range for both front and side that were somewhat cancelling. When you fixed one, the other was no longer cancelled. It happens sometimes. Need to try something much thicker than 2" to try to fix that on the front wall.
 

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Discussion Starter · #16 ·
Even with the improved response of the subs being placed in the back corners, I wasn't satisfied, so I did some more rearranging. Turns out placing on sub at the center of the front wall and the back wall improved response even more. Still not perfect, but much better. Two PEQ filters and I'm a pretty happy camper considering what I started with. Too bad these subs aren't mine :sad:

Anyway, here is the resulting response up to 200Hz. Target response was around 75db with 20Hz being about +6db compared to 100Hz. Again, you can see the 100-200Hz range still needs some improvement.
edit: just want to point out my target curve was based on FR graph and listening/tweaking.


For comparison:
Blue - subs in rear corners
Purple - subs centered F&R
Green subs centered F&R with EQ


Relocating the subs seems to have compensated for the mains dropping off so steeply around the crossover point (80Hz in this case). I also found that putting 4"-6" thickness of damping material directly behind the mains and on the side walls directly adjacent to the mains seemed to even things out a bit above the crossover point, but that area still needs some work. Another huge benefit of this placement is that the bass is very consistent between the front and back rows now. Previously there was a huge variation.

I think the next step is indeed to get some substantial damping on the front wall, and possibly still do some corner traps. Making progress though.
 

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Looking good. 5db range from 20 to over 100 is great.

BTW, that's one of the suggested positioning strategies identified in the Harman white paper. The other is the center of the 2 side walls.
 

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Discussion Starter · #18 ·
Looking good. 5db range from 20 to over 100 is great.

BTW, that's one of the suggested positioning strategies identified in the Harman white paper. The other is the center of the 2 side walls.
Yep, that's where I had originally heard of it. Initially I hadn't planned to try it for a few reasons. First, I had tried the centers of the side walls and it didn't work any better than the rear corner placement. Second, the dual Chane subs are powered by a single Dayton SA1000 which makes for a long exposed wire run. Last, I had to slide the rear seat up a few inches to fit one behind it. Having tried most everything else I figured I'd at least give it a shot. I'm glad I did. Supposedly one sub centered on each of the four walls is a good option too.
 

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As is 1 in each of the 4 corners - but you found the one that works best for you which is good.
 

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Discussion Starter · #20 ·
Ok, moving on to the next step with the assumption that I'll settle on a dual sub setup for good response below 100Hz and maybe add corner traps in the back later. Now looking at the response of the mains from 80Hz to 400Hz. It appears I need treatment on the front wall now since moving the mains side-to-side or out into the room isn't practical and didn't provide a measurable improvement. So I'm looking at GIK 242 panels compared to 244 panels, for the front. The test graphs look to be given with different units, so I'm not sure what the difference is between the two in the range I'm concerned about. Do I...

1. move some or all of my existing 244 panels to the front wall and get some 242 panels for the side walls? (easy on budget)

2. leave 244 panels on side walls and add 242 panels to the front wall? (easy on budget)

3. leave 244 panels on side walls and add 244 panels to the front wall? (stretching budget)

4. something totally different?

Couple details - I can't do corner traps in the front vertical corners, and I don't want to go too thick with treatments on the front walls since I currently have a curtain hung for aesthetics. 244 panel thickness might be pushing it there.
 
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