acoustic solutions for poor stereo image

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Submitted by louzin on Tue, 05/02/2017 - 23:54

Hello everyone!
for a mixing/control room, I know that Equal distance of the mix spot in terms of walls is very important for having great stereo image. But in case when it’s impossible to move the mix spot, what are the treatment solutions or ideas please? when you have the left speaker pretty close to the wall and the right speaker a bit far from the opposite wall of a small room?
The isolation of the rooms is very solid though / here are some sketches of the mixing/control room: http://imgur.com/a/t1jiy

Any general help?
Thanks

Define "a bit far".
Here's the thing...
Unless you can get those speakers closer to a fairly equal triangle, with you being at the downward point, it's gonna be very difficult for you to get "that" sweet spot you seek.
You've mentioned isolation, which is good, but isolation is different than acoustic treatment.
You need to measure your room both physically and sonically to find out what's happening right now
If there are problems (flutter echo, standing bass, nulls) then of course treatment will help, you might start with a cloud above your mix position, maybe some low end trapping or broad band absorbers, but it's all depending on what your room needs, you don't want to just randomly tack up a bunch of foam, and you don't want to overdo treatment either, but even so, those methods alone can't change the actual positions of the speakers or the shape of the room.
If your monitors also happen to have rear-firing ports, then you really need to get them away from walls and corners.
Wish I could help further. Unfortunately, we are dealing with the laws of physics and geometry, and while I consider myself to be a fairly decent engineer, when it comes to changing the laws of nature... I'm not that good. ;)
This may be one of those situations where you may want to consider investing in a really good pair of headphones for mixing, and then you can reference through your monitors occasionally for balances ( but likely not for imaging). For critical listening applications, you're going to want to look at cans that are designed for mixing.

Cheers thanks so much for replying. I have sketches and pictures (with measurements) in the link above!
I already have speakers and material for recording! I am building a desk for the moment but I am very worried about stereo imaging since my mix spot (the desk) is not in the middle (you can see pictures in the link). I was wondering if there are treatment solutions for stereo imaging in this case...
Thanks Donny

I can't say. Without being in the room, it's tough to tell. Doing a quick conversion of metric in my head, your control room is around 10' x 7'. Is that close?
How tall is your ceiling? (And I don't mean drop-ceiling but the actual ceiling)

It looks as though you'd still be in a fairly equal triangle between the monitors and your listening position, but it's your position in the room that will most likely give you problems, particularly the wall to your left.
Not only do you have a boundary in very close proximity to the left speaker, you've also got it in a corner, too.
All I can do is to suggest things. It's impossible to say for sure without being in the room.
Right now you are "short firing" your monitors, meaning that you are aiming them into the shortest distance of the room.
You may want to consider switching your orientation to the other direction, and pointing your speakers into the 3.3 meter distance instead of the 2.6.
The whole (basic) idea of accurate monitoring is based on time - the amount of time it takes for a reflected signal to hit your ears vs the amount of direct signal you hear from the speakers. Reflections will mess with your accuracy in terms of true or false frequency responses, but it will also mess with your imaging as well.
The shape of the room comes into play - due to corners, parallel surfaces, etc.
you should sonically measure your room to get the most accurate picture. At which point you can see what the room needs.
I don't know how you would treat that wall to your left. You may need to treat that wall, but I can't say if you need absorption or diffusion; you may also need a cloud above your mix position...it's really impossible to say without more data.
Paging acoustics guys...
@Brien Holcombe @Kurt Foster

Thanks Donny
Yeah, I pretty much have "equal triangle" btw me and the speakers, my worries are in the "unequal" distance between the speakers and the opposite walls: left speaker close to the corner and the wall and right speaker far from the right wall. I worry coz it may affect the stereo image in my opinion (or not I don't really know, this is the first time I treat a room) that's why I need suggestions.
You are definitely right about the problematic left wall, I guess I need BIG amounts of trapping to my left, large enough to make that left wall acoustically disappear as much as possible. I need also to remove any reflections coming from the more distant right wall. and since my rear back wall is not also far enough from the speakers, I guess I need to treat it a lot as well! I just need to know what traps or material needed that would make left and rear wall disappear acoustically as much as possible.
Thanks again

I'm forced to operate in the same kind of offset position in my room.
I have a wall at my left and more empty space at my right. Any pro will tell it's not good, but when there isn't any other choices we need to make it work.
Since there isn't immediat reflextion to one side, you need to treat the other side accordingly. That's what I did and it works well to a certain extent. I do reference to headphones once in a while to compare and make sure my mixes work.
But you have 2 alternative, you can install your mix position facing the side wall and have the window to one side of the mixing position. You will have the same distance each side of you, but the window will be a problem. The best thing would be to install yourself having the window behind you and face the wall. That way you can have the same distance each side and treat the early reflexion equally. Not cute but accousticly better.

What I'm concerned about in your position is that the room is very small... I also Wonder what material is on the walls, it's seems to be some absorbtion material often use in practice booth.. I fear it's gonna be too dead for recording AND for mixing...
You need to make measurments before waisting time asking yourself why your mixes don't sound good on different systems.

Hey there pcrecord, Thanks so much for replying.
Yea, the material used in the walls is perforated aluminum (the ones found in radio station broadcast studios around my city / It was intended for radio workstation at first but then it changed). My heart just dropped when reading your comments about my rooms being dead lol. But it might be true of course which worries me more now. All I can say is the rooms are pretty much isolated in 3 to 2 drywalls per wall. I thought about installing myself having the window behind me and face the wall but then again I'm afraid the sound coming frm speakers would bleed onto the live room easily... and yeah I'm trying to make measurements even before installing my desk (it is on construction now). I'm really worried and confused to be honest!
Thanks anyways for your reply it was very informative

louzin, post: 449970, member: 50551 wrote: My heart just dropped when reading your comments about my rooms being dead lol. But it might be true of course which worries me more now.

It's not that having a dead sounding room is all bad but with your material, the frequencies absorbtions may unbalance the Spectrum.. Thin material usually affect high frequencies and leave the lower end untouched. We would need to analise the complet wall composition to get a better idea of the frequency range.
When recording vocal with the mouth very close to a dynamic mic (like in most radio stations) I'm sure your rooms would be fine.. but if you record an acoustic guitar or a violin quartet.. I don't know..
Honestly, that's why I was talking about measuring the room sonicly. Rooms that small are hard to work in. We end up with compromises but it doesn't meen you can't record at all.
My booth is 11x10 and I'm able to make a decent drum sound. (altought not without the wise trickery of using carefully chosen added reverbs)

The best thing is to know your room very well and find ways to compensate the deffects you can't fix.
(maybe add reflective surface, diffusers and bass traps)

louzin, post: 449970, member: 50551 wrote: I thought about installing myself having the window behind me and face the wall but then again I'm afraid the sound coming frm speakers would bleed onto the live room easily

You could simply turn down the monitor's volume for critical recordings...
I'm used to do this, I have 2 rooms and when tracking a band, I get people recording in the same room as me. So while tracking I use headphones like they do, kinda joining the party.. ;)

pcrecord, post: 449973, member: 46460 wrote: It's not that having a dead sounding room is all bad but with your material, the frequencies absorbtions may unbalance the Spectrum.. Thin material usually affect high frequencies and leave the lower end untouched. We would need to analise the complet wall composition to get a better idea of the frequency range.
When recording vocal with the mouth very close to a dynamic mic (like in most radio stations) I'm sure your rooms would be fine.. but if you record an acoustic guitar or a violin quartet.. I don't know..
Honestly, that's why I was talking about measuring the room sonicly. Rooms that small are hard to work in. We end up with compromises but it doesn't meen you can't record at all.
My booth is 11x10 and I'm able to make a decent drum sound. (altought not without the wise trickery of using carefully chosen added reverbs)

The best thing is to know your room very well and find ways to compensate the deffects you can't fix.
(maybe add reflective surface, diffusers and bass traps)

pcrecord, Great insights!!! That's what I need to do now! To measure the room sonicly (which I have never done in all honesty) but I'm eager to learn. I'll check the software used for that for sure or tutorials online maybe that would help. This surely gives me some hope heh. Still, it's a bit unconfortable to turn your back to the live room during tracking if making the speakers facing the live room's glass but I guess if I had no choice why not! Thanks for everything really

Kurt Foster, post: 449974, member: 7836 wrote: i love the perforated walls. what is that product?

if this were my space i would use the smaller room as a drum / iso booth and the larger room for the control room.

Hi Kurt! yea they look good! they are basically perforated platter and painted as stainless steel/aluminium (they feel like steel at touch as well just for decoration I guess). They help isolating the room (they are used in the isolation process). They are from this company (It is in french unfortunately...) : https://www.knauf-batiment.fr/solutions/isolation-plaquiste-plafiste/mur-plafond-acoustique-plaque-platre?keys=&items_per_page=12

replacing the live room for the mixing room is a great Idea! Thanks! I think this would be my last resort if I couldn't get the sound right otherwise! Thanks

+1 on trying the other orientation for the speakers, especially before you build the desk. There is no better place to start than optimal speaker positioning.

Apart from that, the imaging is going to come from frequencies roughy 1-200hz and up, and much more in the 1-10k range. So if you can make your listening posisiton acoustically symmetrical where the sense of directionality comes from, mission accomplished. It may never be ideal as a well treated and physically symtetrical listening position, but you can make significant improvements. You still also have the opportunity to try the synergism physical location. A simple curtain over the window, or removable lightweight absorber would help.

If you make some basic diy rigid fiberglass panels 8"thick, and spaced them off the wall a little, and mounted the others on stands (if your room orientation stays as pictured) then you can have something that gives some symmetry at the listening position. Whether On stands or walls, the basics of covering the mirror spots, and bass trapping, don't change for a basic small room, absorbsion based treatment.

kmetal, post: 449983, member: 37533 wrote: +1 on trying the other orientation for the speakers, especially before you build the desk. There is no better place to start than optimal speaker positioning.

Apart from that, the imaging is going to come from frequencies roughy 1-200hz and up, and much more in the 1-10k range. So if you can make your listening posisiton acoustically symmetrical where the sense of directionality comes from, mission accomplished. It may never be ideal as a well treated and physically symtetrical listening position, but you can make significant improvements. You still also have the opportunity to try the synergism physical location. A simple curtain over the window, or removable lightweight absorber would help.

If you make some basic diy rigid fiberglass panels 8"thick, and spaced them off the wall a little, and mounted the others on stands (if your room orientation stays as pictured) then you can have something that gives some symmetry at the listening position. Whether On stands or walls, the basics of covering the mirror spots, and bass trapping, don't change for a basic small room, absorbsion based treatment.

Hey kmetal, Thanks a lot for the infos!!
I guess you are right, since everyone I talk to just told me how symetrical my desk must be at first and with symetrical positions between walls and speakers I will only be left with placing traps and panels... I decided that that's what I should do! I'll rotate the console 90 degrees so it is facing the left wall. That way the window is to my right when mixing. This will also put the rear wall much much further behind, which will help the sound quality I suppose. But as you said, this will create a new problem which is treating the reflections at the window. Do you think a curtain would help? what kind of curtain? or what are the suggestions for treating reflection points at the window?
Thanks again

Yeah that's more like what I mean. Here's a couple sketches of what I'm thinking. Your gonna need tons of bass trapping, so make use of your ceiling/wall corners the entire perimeter of the room if possible. A simple straddled panel with fluffy fiber behind will go miles, I mean decibels in the right direction. Opening those doors will help alleviated some bass pressure levels too.

As far as the window. Angle the glass at the floor as much as possible. And a simple panel that you remove and insert into the window cavity would work, or mount it on a mic stand. You could get a nice thick theater curtain and even double that up. You could also have some absorbsion panel/material on some sort of roll or sliders, and have them come up or down in front of the window. This gives things a more purpose built look.

If your so inclined to could rig up a servo motor or modify powered blinds and you can have full automated/remote control of the window plug.

This is one of the studios I designed and built. In this case the booth was already framed, and the owner wanted to keep it as is.

Anyway the walls are about 10' apart at the listening position. Due to the angled/absorbative walls, and the windows angle, there are no issues/complaints with imaging in that setup. Still not idea, but works okay, since this is mainly a tracking studio.

The layout is similar to your initial one where the desk is off to one end of the room, facing the tracking room. If it weren't for the support poles holding up the gigantic outer structure, we would have fired the speakers the long way. Due to the reasonable size of the room 16x24 roughly, w 10' ceilings, the bass response is easy to work with.

In one of the shots you can see the front wall before we covered it with fire treated fabric from guilford of Maine. There's rigid fiberglass with an airspace behind it. Walls and ceiling cloud. The absorber frame and cloud were attached to the rough finished drywall/isolation wall.

Just food for thought.

Attached files

Hi kmetal! I'm so grateful to you really for giving all these hints and solutions! thank you and The studio looks spacious and great! great job!
I will try this immediately! I have to cancel the desk construction and go for a smaller one in this case which is not a big deal I suppose (The building just started yesterday/ I mean the cutting of wood). for the window, when you said: "Angle the glass at the floor as much as possible", did you mean that I should rebuild another glass for this purpose? coz I already have it built unfortunately... I believe I shoud go for a double thick theatre black curtain that I could readily open and close at will. I don't think I can go for a full automated/remote control motor and plug for now coz apparently I need more money to buy traps and panels this time. I'm so happy you replied kmetal I can't thank you enough...
I'll post pictures of the ongoing work here throughout he whole process if I may...
ps: just a quick question: In the place I'm from, I could only find Primacoustics products for sale on stores. If I want to go for Gik acoustics or auralex I need to ship it. are primacoustics absorbtion panels and traps any good?

louzin, post: 449995, member: 50551 wrote: Hi kmetal! I'm so grateful to you really for giving all these hints and solutions! thank you and The studio looks spacious and great! great job!
I will try this immediately! I have to cancel the desk construction and go for a smaller one in this case which is not a big deal I suppose (The building just started yesterday/ I mean the cutting of wood). for the window, when you said: "Angle the glass at the floor as much as possible", did you mean that I should rebuild another glass for this purpose? coz I already have it built unfortunately... I believe I shoud go for a double thick theatre black curtain that I could readily open and close at will. I don't think I can go for a full automated/remote control motor and plug for now coz apparently I need more money to buy traps and panels this time. I'm so happy you replied kmetal I can't thank you enough...
I'll post pictures of the ongoing work here throughout he whole process if I may...
ps: just a quick question: In the place I'm from, I could only find Primacoustics products for sale on stores. If I want to go for Gik acoustics or auralex I need to ship it. are primacoustics absorbtion panels and traps any good?

If the window is made it's probably best to just live with it. If given the chance again, you may consider putting the glass at an angle to help visual glare and acoustic relftscioms.

Prime acoustic stuff is from what I know is as good as any of the others you mentioned. By no means a compromise.

Please do yourself a favor and plan on some bass trapping around the ceiling perimeter. Straddle the corners, just like the front.

Kurt Foster, post: 449996, member: 7836 wrote: i am not sure but i think you won't need a lot of treatments as that wall board i went on about is an acoustical product. actually the build looks pretty cool.

http://knaufdanoline.com/product-post/stratopanel-wal/

I've been interested in this type of thing myself, lately, acoustic tiles ect.

Not being familiar with this product, but in general, stuffing that cavity or stuffing it leaving an airspace between wall and insulation, would make the walls more efficient in the lows.

I wouldn't modify a manufactures product or installantiion methods without proper care and diligence. I couldn't see any mention or reference to insulating that cavity in a quick look at the install instructions and spec sheets.

Cool link Kurt.

Kurt Foster, post: 449996, member: 7836 wrote: i am not sure but i think you won't need a lot of treatments as that wall board i went on about is an acoustical product. actually the build looks pretty cool.

Pretty cool Kurt! Thanks for the reminder! actually I always thought it was only for isolation since at first, the studio was built with the intention of being for broadcast/radio at first and the one who chose this product (I were willing to work together) was intending to use the studio for broadcasting and he was the one telling me this. Now that I'm left with it and he is gone, I also think it's a good add! I also like the look so much. Now if it's acoustically dependent and absorb some of the laws as stated. I believe I should take that into consideration as well! which means less absorbtion panels: not painting the whole walls with panels maybe... thanks!

kmetal, post: 449999, member: 37533 wrote: Please do yourself a favor and plan on some bass trapping around the ceiling perimeter. Straddle the corners, just like the front.

I will! I'll basstrap the hell out of every corner and ceiling parameter. and put absorbtion panels in the rear and in front of the desk as you stated. Thanks again Kmetal :)