# How can I improve the acoustics in this room?



## accuton140 (Apr 11, 2009)

Hi All
How can I room acustics in this room?

All wall is concrete.


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## Prof. (Oct 20, 2006)

Can you supply some photos of the room? That would give us a better idea of what can be done..


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## sdurani (Oct 28, 2010)

accuton140 said:


> How can I room acustics in this room?


This is what I would do, so that left vs right is consistent, at least compared to your original drawing.


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## bpape (Sep 14, 2006)

The revised orientation is MUCH better for a starting point. That said, the echo and extremely long decay times in the room will be horrible. Some serious damping is going to be required to tame a room of that size with all concrete construction.

What are you using the room for? You seem to be laid out very nearfield. Is this for studio work or 2 channel listening in general and what speakers are you using?

Bryan


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## dsime42 (Mar 4, 2011)

Warning: This comment is from a clueless non-Acoustician.

Wow, what a room.
Pictures would be good, and ... ... are there any doors or windows or perhaps, heaven forbid, a large stairway coming into the middle of the room?

I look forward to the answers you will be getting, here are my suggestions they are probably wrong but I will profit from people telling me why. ;-}
Those side walls are going to be LIVE, my ancient thought is to hang some tapestries to absorb those high freq reflections. (that advice seems dated)
The speaker spacing seems odd to me too shouldn't they be closer? 2728 they only leave 1961/2 mm from speaker center to horrible concrete wall. If you moved them closer say 2000mm center to center you would have almost 1345 from speaker center to concrete.

What is the optimum speaker separation in a two channel set-up with a listening distance of 3659 mm?
Speaking of listening location. Is tat an overstuffed chair? An office chair? A love seat? (hmm how "wide" is the listening position?

I suppose I should have started with how much did you want to spend. :-o
If you put 2x4s on the walls and the floor using irregular spacing and then panel the room with plywood covered with fabric ... ... ... the answers might be somewhat different than if you are, shall we say, less serious.

Are you single? What kind of SAF do you need to apply to both the finished room and the process.

Sorry but being a totally clueless non-Acoustician, I am just not able to offer any "good" advice.
But I may be able to learn from your question.


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## sdurani (Oct 28, 2010)

bpape said:


> The revised orientation is MUCH better for a starting point.


Keep in mind that I re-did the OP's drawing not knowing whether he has any doors or other architectural impediments to orienting his set-up that way. As other posters have said, it would be nice to see pics of the room.


bpape said:


> You seem to be laid out very nearfield.


That's how it looks from the way he drew the speakers, but according to the numbers in the drawing, the room is 15.4 feet wide at that point. The drawing has him sitting 12 feet from the speaker plane, with a 9-foot spread. IF this is a 2-speaker set-up (no subs) and he places the speakers at the quarter points of room width (2nd width mode null location) for some mode cancelling in the low frequencies, then that's still 7.7 feet between speakers (not bad). 

Sitting 6.7 feet away from the speaker plane will give him a 60° spread (traditional equilateral triangle), while sitting 7.7 feet away from the speaker plane will give him a 53° spread. In either case, he doesn't have to listen in the nearfield if he doesn't want to. Even in the narrow section of that room, there is plenty of space to work with (barring impediments not in the drawing).


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## jim1961 (Apr 8, 2011)

As you can see, my room is basically shaped like yours and is about he same size (15.4'W x 25.75'L 8'H)

I am getting good results.

Black = Absorbers
Wood = Diffusers
Gray = Reflectors

Mine is a listening room.

(this is an older rendition, but it illustrates my basic strategy)


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## accuton140 (Apr 11, 2009)

I can't speak English well.
And it is not easy to understand but trying!
Please understand, even if I do not speak English well.

I'm trying to understand a good writing and information in here and always grateful to you.


I plan to begin construction of room acoustic.


Sooner or later, I'll attach a few pictures.


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## robbo266317 (Sep 22, 2008)

You can always use google translate for phrases you are unsure of. http://translate.google.com/

항상 Google이가 확실치 구문을 번역 할 수 있습니다.


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## accuton140 (Apr 11, 2009)

*I have posted photos (Listening Room) now!*

Circumstances, I cannot change the speaker placement in the opposite direction (rear) of the room.


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## accuton140 (Apr 11, 2009)

I have posted photos (Listening Room) now!

Circumstances, I cannot change the speaker placement in the opposite direction (rear) of the room.


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## accuton140 (Apr 11, 2009)

I have posted another (REW Data) photos.

I plan to install acoustic panels as shown below.

Location of speakers and the listening position have not decided yet.

I would appreciate it if you could inform the appropriate location of the speaker.

I'd like to know in detail what problems exist in this listening room?

Thanks!


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## bpape (Sep 14, 2006)

The foam on the front wall is not doing anything except taking all the high frequency life out of the room and leaving the bottom end untouched. The front right corner needs some broadband bass control as that speaker is much more corner loaded than the left side is. Rear corners could use the same.

If the shelving directly behind the seating can be moved, that's another prime place for some bass control to help with your sitting back in the room relatively far.

Bryan


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## accuton140 (Apr 11, 2009)

Dear Bryan Pape!

Answers so quickly, thank you very much for your help.

Please tell me a little more information, I would appreciate it if you could for my room acoustics.


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## bpape (Sep 14, 2006)

The panels on the left are doing little to nothing. The right side is correct for the corners. The panels you show on the right according to the pictures are behind the reflection zone so not doing much.

Decay time is out of control in the bottom as to be expected - hence my recommendations.


L and R channel different down low - again to be expected due to lack of symmetry left to right.

When you look at frequency response, do it with no smoothing and scale the bottom to be just 30-400Hz or so. Very hard to see what's actually happening with full scale and 1/3 octave smoothing on.

Bryan


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## accuton140 (Apr 11, 2009)

Dear Mr. Bryan Pape!

I have posted another REW Data (30Hz ~ 400Hz pictures).


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## accuton140 (Apr 11, 2009)

How about this?


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## bpape (Sep 14, 2006)

That's better but not convinced you need full coverage on front and side walls like that. 

Also, would be nice to see both speakers together. While helpful to see each speaker individually, what you hear is both together.

Also, just plot the ALL SPL and the WATERFALL - both with no smoothing.


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## dsime42 (Mar 4, 2011)

An actual blackboard!!
Is that open cell foam around it?

And carpet squares on another wall, with a wall of "unfinished" slats.
With an area rug over shiny wood floor, where is all this concrete you mentioned?

With a hardwood floor laid on a concrete slab I would think that spikes would provide better bass that "rubber isolation casters". Do you roll the speakers "out of the way" and remove the pillows from the blackboard when you work, then re-place the speakers and place the pillows when you want to listen? seems like it might be difficult to get the speakers placed in the same position each time.

I can't wait till someone knowledgeable comments on what you might do here.

P.S.
I note a structure sort of separating the room into two parts, is that a bass trap or does it cover a structural beam that holds up the floor above?


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## accuton140 (Apr 11, 2009)

Dear Mr. Bryan Pape!

Thank you, once again, kind response.

Well, I have a question.

Do I need to re-measure REW with no smoothing mode or use existing measurement data?


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## bpape (Sep 14, 2006)

You can just turn off smoothing under the gear button in the upper right corner of the ALL SPL screen.

Bryan


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## dsime42 (Mar 4, 2011)

@bpape
If he removes that 40Hz (38?) left null will that also help with the one ~160? (40-80-160) ???
Also the majority of the right SPL looks ~6db lower than the left. Is that "correctable" with the balance knob or is it a job for room treatments?


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## bpape (Sep 14, 2006)

Probably not - 38 null, 76 peak, etc. They alternate IF modal and that's a big if.

Difference from side to side likely has more to do with boundary related bass cancellations from reflection points.

Bryan


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## accuton140 (Apr 11, 2009)

Dear Mr. Bryan Pape!

Thanks! I found.

I have posted All SPL & Waterfall no smoothing photos, etc.

To sincerely thank your efforts for me.


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## dsime42 (Mar 4, 2011)

@Accuton140
In the first jpg you posted, you had room dimensions listed.
On the left side, at the rear, the wall slants and you posted a width of 5599mm.
Was that at the back wall or some semi-arbitrary point on the wall? Maybe next to the book case?
Also the ceiling height is 2800mm. That at the highest point, not at the support beam right?
5600 which would be the width not too far from your measurement point on that slanting wall, seems to be exactly twice the 2800mm height. 

The "width of the back wall", the "length of the straight portion of the left wall", and the "length of the wall on the left with a door" would allow better information about that slanting wall.

Nodes?
61.5 H W
123.0 H W
184.5 H W N
246.0 H W
307.5 H W

(H) (L) (N) (W)
Height Length Width Width
Nomnal Wide
mm 2,800 7,158 4,689 5,599
Feet 9.19 23.48 15.38 18.37


61.5 24.1 36.7 30.8
 123.0 48.1 73.5 61.5
 184.5 72.2 110.2 92.3
 246.0 96.2 146.9 123.0
 307.5 120.3 183.6 153.8
 369.0 144.4 220.4 184.5
 430.5 168.4 257.1 215.3
 492.0 192.5 293.8 246.1
 553.5 216.5 330.5 276.8
 615.0 240.6 367.3 307.6
 676.5 264.6 404.0 338.3
 738.1 288.7 440.7 369.1
 799.6 312.8 477.4 399.8

(sorry about the ugly table) onder:


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## cuby (Feb 18, 2012)

I think what guys are trying to tell you is that, your listening room should be symmetrical and that is to accomplish even reflection times off the either wall.
In my opinion, if you'd like to keep the room orientation, you may consider to:
1. Separate the room recess, which would be 910 x ~2,400 (e.g. make hallway there)
2. Position speakers symmetrically in the room
3. At least, treat the first-reflection points. Hold a mirror against ceiling and walls: wherever you see the speaker from the listening position, put absorption material there (rigid fiberglass is the best).
4. Put bass traps in corners (esp. tri-corners)
5. Use sound diffusion on the wall behind speaker and the opposite wall.


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## allrawk (Feb 3, 2013)

As has been mentioned a good rule of thumb is sound diffusion up front, and absorption (especially bass) in the back. 

It looks like there isn't any treatment on the ceiling, most of the best rooms I have heard have diffusion directly over the primary listening position (something like RPG's offerings) and absorption for the rest of the ceiling. 

The rear wall "egg crate" absorption could also be upgraded to a thicker (2" deep is a bare minimum) and denser material. Many people use framed up fiberglass with a fabric (NO backing on the fabric, make sure it "breathes") covering.


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## bpape (Sep 14, 2006)

If you're going to get this under control, you're going to have to balance the room better. I know you can't change things around and are resistent to walling off the left area in the front but that would really help.

Even so, you're going to need some pretty thick treatment on the wall behind you, in the front corners, etc. Side wall on the right will need at least 4". Not as concerned about the front wall and nook reflections other than the corners.

Also, to save you time, space, etc. - just post the ALL SPL and use the LOG across the bottom - not the one you're labeling frequency axis. The other ones we would want to see would also use the LOG across the bottom and that would be L, R, and both channel waterfalls. The distortion, spl/phase, etc. aren't really relevent and something is wrong with it anyway - never seen an spl/phase graph without the phase portion....

Bryan


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## dsime42 (Mar 4, 2011)

@cuby
1) The recess idea. would that work? Wouldn't the bass wave go through the "make shift" gypsum wall board and still reflect off the concrete? Where did you come up with that approx size? (Just wondering. If I could have deduced the size I wouldn't have asked him to measure it. I tried to guestimate using the foam on the wall but I couldn't tell how may sheets he was using. :-( I thought about counting the floor boards but felt it wouldn't have any sort of reliability. Plus I am unsure it is needed.)

I thought that if he could determine where that 40 Hz null was coming from perhaps moving the speaker forward or back a relatively short distance might help. Of course if he were to use that odd shaped recess to build a 40Hz trap it could help, but a trap tuned to 40Hz seems to need to be seven feet deep. :unbelievable:

@bpape
If he walled it off would sheet-rock work or would he need to go with a cement board (Handi-backer)? (Trying to rent a clue here)
Does he need to do more for that door on the right side? Could it be acting as some sort of resonant panel?
Do the castors under the speakers make sense to you?
Would a waterfall @120ms tell you more that the ones he has already posted?
I get SPL/Phase graphs with no phase info too. I am probably misusing REW. 

@accuton140
What is the function of the hole in the back of the top section of the speaker? Is is a Bipole?
I asked in a previous post about how serious you are on this room's treatment. Is this a temporary fix until you build a new home or something similar?
Or is this a full-on room revamp for your new speakers.:T


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## bpape (Sep 14, 2006)

What I asked for is what I need from him. The wall on the left would be standard construction but not sure if he can/wants to do that. It would create symmetry and make the room more predictable as well as having both speakers' response be more similar.

Not too concerned about the door on the right other than it makes treating reflections on that side more difficult.

Bryan


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## cuby (Feb 18, 2012)

In reply to: dsime42
You are right. Assumption is that the wall would be a gypsum board with fiberglass behind it. This would do only a little for very low frequencies, but those are everywhere anyway and I don't see that anybody is planning to tame those. The advantage would be in the higher frequencies. I've estimated the recess area, so so it's clear which part I mean. Plus, there are TOO MANY things is in room, too many corners (not only 12 as usual), too many tri-corners (not only 8 as usual), but most importantly the speakers are MOVABLE. The green "black-board" in the front, should be replaced/covered with diffusors (QRD the best). So I think this is going to be a challenge and impossible to calculate.


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## bpape (Sep 14, 2006)

Just please remember that the space has a functional need. Just replacing things to make it a purely listening space is not what he's looking for. We're trying to make the space as good as we can while still allowing it to function for his primary purpose.

What makes you suggest diffusion on the front wall with a non-dipole type of speaker? What is that buying him? Any problems on the front wall would be from SBIR which would be better handled by absorption. That said, it's a moot point as the blackboard is staying as far as I know.

Bryan


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## cuby (Feb 18, 2012)

Yes, I had in mind the reflections rather then speakers itself. Wouldn't this diffusion help the frequencies in that 200-300Hz range?


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## cuby (Feb 18, 2012)

.. but I agree, this would not align with the intention and will be quite pricey.


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## bpape (Sep 14, 2006)

cuby said:


> Yes, I had in mind the reflections rather then speakers itself. Wouldn't this diffusion help the frequencies in that 200-300Hz range?


Maybe 300 if the diffusion was at least 6" deep - even then, the SBIR problems will likely be lower than that based on the distance to the front wall.

Bryan


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## accuton140 (Apr 11, 2009)

Dear Mr. Bryan Pape!

I did not understand your message (LOG), so I had a hard time all day. ha ha!

I lack the skills ...

I have posted REW Data photos.

Is that correct?


To sincerely thank your efforts!


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## bpape (Sep 14, 2006)

Yes - that's correct now aon the bottom scale. It's just that musical notes and scales are more logrithmic in nature rather than linear.


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## accuton140 (Apr 11, 2009)

Dear Mr. Bryan Pape!

1. left and the right balance problems at the 30 ~ 400Hz frequency band.

2. at the left side of 39Hz, 175Hz, 266Hz, 392Hz and at the right side of 82.4Hz, 105.5Hz, 266Hz, 302Hz frequency band issue on the ALL SPL graph.

3. long decay time problems at about 30 ~ 200Hz frequency band on the waterfall graph.

How do I fix it when you analyze?

I'll be looking forward to a wonderful answer.

Thank you!


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## bpape (Sep 14, 2006)

And you will continue to have differences side to side as long as the room is unbalanced. Best we can do is absorb the reflections and help where we can based on the restrictions.

Long decay times are easier to address as long as you're flexible about large thick treatments.

Bryan


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## accuton140 (Apr 11, 2009)

I'm very much obliged to you.


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## dstr212 (Feb 10, 2013)

This is almost the exact shape of my room


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## dsime42 (Mar 4, 2011)

This thread just sort of petered out.

accuton140: Did you apply any treatments? Did you get any improvements?


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