Hi,

Ive got an L shaped garage studio conversion with sloping ceilings all round. The size would roughly fit one and a half cars and ceilings slope at 25 and 15 degrees from 9ft2" to 6ft11". Its a proper awkward L shape. After reading here, I think it seems to be exactly the wrong shape for a music room but is all I've got (planning and wife wouldn't allow anything else)
I was going to try the room eq wizard as I've got an spl meter but after reading the help files on the site i was totally overwhelmed - I'm not very technically minded and struggle with computers. I've been using the sos bass staircase test to assess the peaks and troughs at my mixing position. I fire the speakers down the longest room length and have tried them at different positions from the wall and from each other but have found there is always a slight trough around ~80hz, a peak at about 125hz and then a ridiculously large peak at ~150hz, with almost as strong peaks occurring after this (plus some troughs). There is possibly a very small reduction in the severity of these by offsetting the mixing position by about 6" to the side walls but its nothing substantial.

I then decided to try the speakers down the opposite end of the room (again firing down the length) with approximately the same relative mixing positioning (as close as i could get it) and found there was a slight but noticeable improvement. I always have the garage door open and the new position is much closer to the door so I'm assuming that will be helping somewhat with the bottom end but there is also more ambient noise coming from outside here and i like to mix very quietly.

The problem i have with the new mixing position is that there is no wall to my left side to match (as far as symmetry) the side wall to my right, so there is no symmetry for the side walls for stereo mixing. There obviously is a wall to the left but it is much further away.

The dilemma is this: Do i stick with the old position and make the best of it with traps I'm building or am i better off changing to the new position and sacrificing any stereo imaging ? (i could build portable traps for the place where a wall should be to the side of the mixing position).

Regarding the traps, i am planning on building corner traps (super chunk or other) and wall and ceiling traps plus at mirror points - these will be 100mm depth. What is the lowest frequency this depth of trap will help with - any help below 100hz ?

Any help would be much appreciated as always.

cheers

Peter

I checked both room positions again this morning with fresh ears and it is not a small difference but a very noticeable one. Even when i close the garage access door (not a car garage door by the way, just a normal door) when in the the new position (the one without a side symmetrical wall) it still seems much flatter here on the sos bass staircase test.

I then went all around the perimeter of the room whilst listening to the bass staircase test and the worst place is definitely the walls around the old mixing position, the worst of these being the middle of the wall behind the speakers and particularly the corner to the right of this wall with its low sloping ceiling height (6ft 11"). In fact the whole right side of this part of the room, with its smaller dimensions relative to the left (which has a taller 9ft 2" ceiling at its sloping peak) is bad. This seems to make sense as the smaller the room dimensions the worse the problems can be in general i think.

I really didn't want to have to change the room the other way round and lose some symmetry as well as having to make and put up a side free standing trap to get back some symmetry for mixing (this will take up usable room space) but i can't deny the difference. Then there's still the issue of the increased ambient noise from the door being opened (i have to have it open when mixing to get fresh air into room as there are no windows).

What would the knowledgable folk around here suggest ?

Peter

I must admit that I find it hard to visualise the room layout from just a description. A floorplan would be a big help.

James.

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JRP Music - Audio Mastering and Restoration.
http://www.jrpmusic.net

Hi James,

I have found a simple art package and will try my best to get here as soon as i can.

Cheers for the help,

Peter.

Edited by Helmutcrab (07/07/12 02:27 PM)

Hi James, here is the plan. If you or anyone else wants more info please don't hesitate to ask and i will try my best.





The room walls are single skin 12.5 mm plasterboard with 100mm isowool behind and between an independent wooden frame with 600mm spacings. This frame is offset from the brick by 2". The garage is built with bricks. The ceiling/roof is 2 layers of 12.5mm plasterboard with 100mm rock wool behind between joists (400mm spacing) and roof tiles on top. Floor is 75mm celotex with 1" tongue and groove and underlay and carpet on top.

Cheers

Peter

Edited by Helmutcrab (09/07/12 05:25 PM)

As you say, the existing position looks best from a symmetry point of view. I would possibly try some bass traps in the corners behind the speakers and also find a way to break up the flatness of the walls either side as I suspect your main resonance problem is from these walls.

At least the sloping roof will help reduce the floor to ceiling resonance.

James.

--------------------
JRP Music - Audio Mastering and Restoration.
http://www.jrpmusic.net

Hi James,

I would certainly prefer to keep the mixing position where it is. The main problem is the noticeable peaks and troughs that are much less severe in the other proposed position. Im not convinced i will get a large reduction in them even with 6" 48kg/m3 and 6" gap absorption around the mirror points, although the corner traps I'm planning on making are close to 1/8th wavelength of the 150hz resonance which would help a lot except that this 150hz does seem to be more on the side walls and wall faced in the mixing position. It would just be a bit of a problem to put them up only to realise they have not been sufficient.

I should add that i work in mono for the bulk of my mixing but i still need an accurate stereo image for panning and fx towards the end. I could use headphones for this and so use the proposed mixing position but thats really not ideal.

I appreciate what your saying with regards to angling the side walls - maybe by angling a combination of wood faced bass, bass/mid and mid/high panel traps (with a layer of rock wool onto to stop reflections ? ) but I'm not really confident enough to do that.

I know its hard to say without actually hearing the room but just to clarify, are you thinking its better to have symmetry (even with these problems) over forced symmetry without them ?

Cheers

Peter

Helmutcrab,
I agree with James you really want to keep your mixing position where it currently is and look to deal with the frequencies causing you modal issues.

It appears to me that there is a very high chance that the relative flat response you are observing at your new mixing position is a result of sound waves cancelling themselves out as they are reflected from the back wall and the wall where your door is.This could result in you potentially over compensating for certain frequencies including your low end unknowingly and affecting the portability of your mix. The only way to test if this is the case is by carrying out a mix of an audio sample you know well and listening to it in another room.You could of course keep the door open which is helping because an open door is a perfect absorber and doesn't reflect any bass waves but as you mention this is not a productive set up.

suggestion
In my article "taking the boom out of your room" I suggest dealing with bass issues in three steps,
1- choose your mixing orientation - Speakers firing down the length of the room
2- Choose your listening spot
3- Isolate your speakers if they are not effectively decoupled and bass trap your room.

If you were to go with the old mixing position I would recommend you consider trying out having your listening spot (i.e where your head will be when you are listening to your mix) at about 1.7 m from the wall you are facing.

your monitors should be placed so that the front grill is about 0.85m from the wall you are facing

Proceed to bass trap your room front left and right corners top to bottom. In your case I would attack every corner with fibre glass including those at the back end of the room. 100mm of 96kg/m3 fibre glass has an absorption coeffient of about .8 at 100Hz so should serve quite well in helping reduce the significance of those troublesome bass frequencies.

Once you have nailed your low ends you can then work on treating your early reflection points to refine the sound to your taste. Once done you should be able to have a room that has great acoustic characteristics and is quiet enough to work in.

I hope this helps with your dilema, please shout if you need any further help or clarification

regards
David

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David
Hyped Up Acoustics

Hi David,

Thanks very much for spending the time to explain your reasoning. You and James have got me sold on staying where i am in the room and making traps for the corners and mirror points. I will also give that listening and monitoring position a try too !

Much obliged

Peter