Splayed Walls in Control Room

[jeremycox]

My control room is 16ft wide and around 27ft long. The wall behind the console will be splayed out. Is there a magic degree for the angle of the splayed walls? What percentage of the wall should be splayed?


Thanks,
Jeremy

[avare]

This is confusing how are you splaying the wall and why? your room is long enough for diffusion on the rear walls to be quite feasible. For flutter echo control, 6° is considered sufficient. For more on splayed walls read this thread.

Andre

[jeremycox]

Im talking about the walls behind the monitors. The ceiling is a drop ceiling covered with rockwool above the tiles. I've seen numbers like 22.5 degrees as a common angle for angling the walls behind the monitors.

Im talking about something sorta like this this:

/--------\


Where the console with be in front of the wall. (could use the google sketchup... but i like my ascii sketch).

[jeremycox]

[avare]

From what you are describing I am assuming you re soffit mounting your monitors. Otherwise there is no advantage to splaying those walls. The standard angle 30° per side, forming an equilateral triangle with your head at the third point. This is usually taken as 18" behind the edge of the console.

Andre

[Xavier L]

Originally Posted by avare

From what you are describing I am assuming you re soffit mounting your monitors. Otherwise there is no advantage to splaying those walls. The standard angle 30° per side, forming an equilateral triangle with your head at the third point. This is usually taken as 18" behind the edge of the console.

Andre

Hi Andre, Hi all,

Just a question and sorry if my english isn't perfect.
Last year I did some works in my CR, based on a lot of things I've read on the internet and in Philip Newell's book. And now that everything's done (splaying walls, acoustic treatment...) the room doesn't sound better than before, just different, different problems

One of the thing I did was splaying walls behind the console (35%) but without soffit mounting my speakers (they don't need to be, it's Focal Twins, nearfield monitors..)They are sitting on customs metal stands, filled with sand, with the back of the speakers nearly touching my splayed walls.

Those walls are made of 2x3 studs covered with a thin (3 millimeters) wood piece and everything between these walls and the real CR walls is filled with rockwool, floor to ceiling) and just next to my speakers I have a 2 feet x 4 feet 'hole' covered with fabric. This was supposed to be my DIY basstraps...

After all, when I bring my mixs in the real world I'm having trouble with the upper low end/low mids range (let's say 80Hz-300Hz) if I trust my ears. Other than that the room sound is great, I don't have problems in the high mids or highs.

To give you and idea of the room (sorry I don't have a plan) it's 20 feets wide and 15 deep, ceiling @ 8 feets. Here are some old pics to help. (now there is a Euphonix Console instead of the desk you see in the pics but it's roughly the same size and there is 2 primascoustic bass traps on the rear wall instead of the 4 panels shown in the pic)

In fact my question is, are the splayed walls part of the problem ? Is there any benefit without soffit mounted monitors ?

[avare]

Xavier Landry:

Welcome from Mainland North America!

There are several things going on in your room just from what you have written and shown in your pictures.

The pictures show your monitors definitely not in a near-field setup. 80-300 Hz is Forrests's "no man's land" of neither modal nor diffuse room acoustics. The thin walls are doing something, and it is almost certain it is not good.

Get REQ or another test program and shoot the room. Post the ETC, system response and waterfall graphs for further analysis.

ps: I hope Hurricane Igor was not bad on you.

Andre

[Xavier L]

Hey Andre,

Thanks for your quick answer, Igor wasn't as bas as in Newfoundland, just a lot of water in some basements and some trees down

I don't know anything about REQ, do you know a good free test program to run on a Mac ? I think I'll need a microphone in omni also ? Do the C414 will do the job ?

Thanks a lot

[Jens Eklund]

Originally Posted by Xavier Landry

Hey Andre,

Thanks for your quick answer, Igor wasn't as bas as in Newfoundland, just a lot of water in some basements and some trees down

I don't know anything about REQ, do you know a good free test program to run on a Mac ? I think I'll need a microphone in omni also ? Do the C414 will do the job ?

Thanks a lot

Room EQ Wizard - REW Home Page

Room Measuring for Beginners

/Jens

[Xavier L]

Thanks a lot Jens, I'll do the test today and post my results.

[Xavier L]

First I tried to get REW working but I wasn't even able to download it, broken link etc... so I ran a small test with fuzzmesure Pro (the free trial)

It was done with a C414 in omni placed at mix position.
What do you think ?

Thank you very much for your help

[Xavier L]

Well I did a lot of tests this afternoon, I moved the speakers a lot, I added 2 more primacoustic fulltrap and dispite some minor changes I still have -10db holes @ 140-150Hz and 500-600Hz
can somebody help ?

[avare]

Originally Posted by Xavier Landry

Well I did a lot of tests this afternoon, I moved the speakers a lot, I added 2 more primacoustic fulltrap and dispite some minor changes I still have -10db holes @ 140-150Hz and 500-600Hz.

Dimensions of your room and current pictures. The 140-150-Hz dip could be reflections from your high angled surface.
The 500-600 Hz SBIR depending on your speaker/boundary postition. AN ETC and waterfall will help.

Andre

[jhbrandt]

Tilting the large desk forward will help too.

What are the front to back measurements? It is possible to still have SBIR issues where your speakers are positioned in spite of the treatment behind the panels.

Cheers,
John

[Xavier L]

Originally Posted by avare

Dimensions of your room and current pictures. The 140-150-Hz dip could be reflections from your high angled surface.
The 500-600 Hz SBIR depending on your speaker/boundary postition. AN ETC and waterfall will help.

Andre

Do you mean the angled ceiling above the desk ? I have some 2" rigid fiberglass here, I'll try tomorrow.

I'm sorry not to provide waterfall and ETC but I can't find a free software for Mac, every link for the REW download seems to be broken

t Tilting the large desk forward will help too.

What are the front to back measurements? It is possible to still have SBIR issues where your speakers are positioned in spite of the treatment behind the panels.

Cheers,
John

I'll post new pictures tomorrow, the desk isn't there anymore and some things had moved since the posted pics

Thank you very much for your help and please forgive my english mistakes

[avare]

Originally Posted by Xavier Landry

Do you mean the angled ceiling above the desk ? I have some 2" rigid fiberglass here, I'll try tomorrow.

2" fiberglass is effective for incident sound absorption down to around 1 kHz.

Congratulations on getting several great people involved with your project here.

Andre

[Xavier L]

Originally Posted by avare

2" fiberglass is effective for incident sound absorption down to around 1 kHz.

Congratulations on getting several great people involved with your project here.

Andre

Hi Andre,

So it's useless ? The manufacturer specs says it effective from 500Hz. Specs : (Primacoustic Acoustic Solutions) I have 2 of those bass traps : Primacoustic Acoustic Solutions for spare, should I put them on my angled ceiling above the console ?

I'll get fuzzmesure complete and do some more analysis soon.
Thanks for your help, very appreciated !

[avare]

Originally Posted by Xavier Landry

So it's useless ? The manufacturer specs says it effective from 500Hz.

The 500 Hz is for sound coming from all angles. For stopping direct soound waves it effective to ~1 kHz. Think of it in terms of your problem. You have isses at ~ 150 Hz and 500 Hz. The first one is too low regardles of the type of sound. The second one is too low for direct sound.

Thin absorbers are not recommended by me, and many other people, for that reason.

Andre

[Xavier L]

I've done a few more tests with more precise scale, here are the results





So I added 2 bass traps above the console and there was little to no change then I moved the mic back 1 feet from the mix position and it was a whole new world in terms of results : the 80Hz dip moved to 75Hz, and so on...

I'm going nuts with this thing.
anybody want to take a plane for St Pierre and fix this for me ?

[avare]

Originally Posted by Xavier Landry

So I added 2 bass traps above the console and there was little to no change then I moved the mic back 1 feet from the mix position and it was a whole new world in terms of results : the 80Hz dip moved to 75Hz, and so on...

I'm going nuts with this thing.

Why? Without giving us dimensions you just identified the 80 Hz dip is SBIR. thumbsup Treat the front wall or flush mount the monitors to solve that one.

Move the test mic up 1 foot and see if the upper dip moves.

The waterfall looks not bad at all. Some modes, but that is that what makes sound like rooms.

Andre

[Xavier L]

yes ... after lots of tests I finally moved my speakers 50cm inside the room and the mixing desk too.
The 80Hz dip is almost gone, and the 100Hz-400Hz really improved .
The only real mess left is around 450-550Hz (-20/30db) but I guess these come from the desk reflections.

Red is with additional bass traps speakers and board close to front wall
Blue is in the exact same situation with speakers and board moved back







Xavier

[Xavier L]

any comments ? I'd love to hear from people who "know" if I'm on the right path.

Thanks a lot.

[avare]

Originally Posted by Xavier Landry

any comments ? I'd love to hear from people who "know" if I'm on the right path.

Well, I don't know if you conseider me someone who knows, but...

Yes you are on the right path. You have igonred requests for dimensions etc. Without that we are guessing. What is your height dimension? There are significant drops in RT at 80 and 160 Hz. Unless that RT plot is before moving the speakers? The upper midrange could be from the console. Put a thick blanket on it and test again.

Andre

[Xavier L]

Originally Posted by avare

Well, I don't know if you conseider me someone who knows, but...

Yes you are on the right path. You have igonred requests for dimensions etc. Without that we are guessing. What is your height dimension? There are significant drops in RT at 80 and 160 Hz. Unless that RT plot is before moving the speakers? The upper midrange could be from the console. Put a thick blanket on it and test again.

Andre

Yes I do consider you as someone who know and I really appreciate the help found here. I hope to be able to help back one day on something i know thumbsup
RT is after moving the speakers.
Sorry but I didn't catch that you wanted to know the room size.
The outer walls are :
From front to back : 15 feet
From side to side : 17 feet
Height : 8,5 feet

there's also the splayed walls and some false ceiling panels (seen on the previous pics)

Thanks

[jhbrandt]

Xavier,

Are those dimensions exact to the inch and from hard wall surface to hard wall surface? - Not from thin panel walls or drop ceiling. Thanks.

If these are your exact dims, then you have double incidences starting at, 66.47Hz, 76.40Hz, 100.47Hz, 131.10Hz, 132.94Hz, 138.17Hz, 148.63Hz, etc...
And if your RT-60 (term) is approximately 0.4sec - your 'no man's land' will be from 152Hz to 611Hz. --- But I seriously doubt this is correct, because your graphs do not show this.

You are definitely on the right track now and if you can get me some very exact measurements, I can recommend some targeted treatment.

Cheers,
John

[Xavier L]

Hi John,

Yes those dimensions are from hard wall to hard wall and exact (maybe half a inch less or more....).
This is an all wood room, with cedar, birch and pine surfaces. 2 outer walls (left and back walls) and two inside walls (front to live room and right to machine room). The house is made of wood also (no concrete). And the control room is in the middle of the bulding (above the basement and there's an upstairs story )

Hope that helps, sorry for the english once again.
Thanks a lot for your help.

Xavier

[Xavier L]

just a tought, I have lots of bass traps in this room, and behing the thin surfaced walls on each side of the desk I have tons of rockwool from floor to ceiling with a large hole covered by speaker fabric... maybe that's why my low end is acceptable ?

In fact now I feel that my no man's land is after 300hz.
And the graphic does'nt look good, even in the 600-1000 area. There's no smoothing on the graphic but antway, my ears don't lie, at least I hope so...

[rcb4t2]

Sorry if I missed this, but I didn't think I saw mention of your rear wall treatment? Lots of talk about the front wall (or are my reading skills slipping again?) (ps I can see the diffuser of course...)

[Xavier L]

Originally Posted by rcb4t2

Sorry if I missed this, but I didn't think I saw mention of your rear wall treatment? Lots of talk about the front wall (or are my reading skills slipping again?) (ps I can see the diffuser of course...)

I have a DIY 8ft X 4ft diffuser and 2 primacoustic fulltrap on the sides (in place of the soft absorders shown in the pic)

[andrebrito]

Have you ever tried to place a small carpet on the floor ? I am usually against carpets but that floor is very very reflective