Acoustic treatment for existing space

#1

Hello,

I would be very grateful for advice on my studio project which is to be a single space for recording (vocals, acoustic guitar, sax, flute, not drums), mixing and mastering music in the Pink Floyd genre. All mixing is done within Logic. Predominantly it will be just myself working in this space.

We have just moved to a very rural location in Shropshire (UK) far enough away from neighbours such that sound proofing is not an issue for my studio. I am considering one of 2 existing spaces at either end of a detached annex with an existing kitchen between them. The annex is of block construction with pitched tiled roof, concrete floors and plastered walls. The other alternative would be a new build in the garden.

L Shaped room incorporating existing bathroom
This will most likely entail removal of the bathroom in order to achieve a symmetrical shape and a reduction of the width dimension to improve baseline acoustics.

2 adjoining square rooms
This will entail removal of the structural wall between the rooms, installing a supporting RSJ and potentially reducing the length dimension.

My previous studio in Peterborough was of nearly square proportions (5.95 x 5.5 x 2.5) with floor to ceiling windows all along one side and with no acoustic treatment. There was a very considerable difference between the sound from my monitors (Focal SM9s on Isoacoustic stands) and the sound through headphones. So for example my "goto" Bosendorfer piano sample sounded rich, full bodied and natural on headphones but somewhat honky through the monitors. I did my best to find a compromise that translated somewhat passably to other consumer listening devices but by no means as consistently as my reference material (Pink Floyd).

So far in my research I have concluded in summary terms the following regarding acoustic treatment:

• The overall aim is a nearly flat frequency response with minimal reflections and a clear stereo image with well defined central phantom speaker
• The shape and relative dimensions of the room are the key limiting factor.
• The most difficult issues to fix are distortions in the low end.
• The listener and monitors should form an equilateral triangle mid way between the side walls.
• Monitors should be placed either several metres into the room or very close to the front wall, to avoid the worst boundary effects.
• Computer screen should be kept as far as possible out of the line of sight of the monitors and sitting on the smallest practical desk
• Low end acoustic absorption treatment is the first priority.
• Dispersion is used to prevent the room sounding too dead.
• Following acoustic treatment further flattening of the frequency response can be achieved using software such as Sonarworks SoundID Reference Monitoring & Playback Correction System. Also this system can be used to emulate consumer listening devices; as I currently only have one set of monitors (Focal SM9) this could be very useful if it is accurate.

Feedback to date
Most parties have advised the existing rectangular space to be most suitable. One party prefers the L-Shape space with the bathroom removed and width reduced to about 4.8 metres on the expectation that this space, with more overall cubic volume, will perform better with low end frequencies and hence be more suitable for the intended material.

I have been advised by a number of parties to reduce the length of the rectangular space from 7.3 metres to 4.5 to 5.6 metres by inserting a dry wall divider. However one party is of the view that this would not be of significant benefit and that any acoustic issues due to the length could be quite easily solved by treatment.

I have been advised by one party to remove at least 300mm off the back wall, 150mm off the ceiling, and 100mm of the side walls of the rectangular room.

I have been advised by a number of parties to cover or curtain the window that’s closest to the speakers and listening spot to minimize high frequency reflections.

Anticipated Process

1. Rectangular space: Remove existing internal structural wall and replace with RSJ. Potentially insert Dry wall divider to reduce length dimension.

2. L shape space: Remove bathroom. Potentially insert Dry wall divider to reduce length dimension.

3. Replace carpet with hard wood flooring or vinyl.

4. Position monitors in expected listening position set with equilateral triangle

5. Use software (e.g. Room EQ Wizard) to measure room response at listening position in untreated room. Save graphs.

6. Try moving listening position in a few locations closer and/or further from front wall.

7. Repeat measurements with Room EQ wizard.

8. Position monitors in best listening position as determined by Room EQ wizard from all the tested locations.

9. Interpret graphs to determine what acoustic treatment is required and at which locations to achieve target room response (e.g. decay time < 0.6 seconds, Nearly flat frequency response, stable stereo image). Q. CAN I REALISTICALLY DO THE ANALYSIS MYSELF AND DECIDE ON THE REQUIRED TREATMENT AND IF SO HOW? OR IS IT ADVISABLE FOR THIS TO BE DONE BY SOMEONE WITH DEEP KNOWLEDGE OF ACOUSTICS AND EXPERIENCE IN THE FIELD? OR IS THE TYPICAL APPROACH TO JUST INSTALL BASS TRAPS IN THE CORNERS AND ABSORPTION PANELS AT THE FIRST REFLECTION POINTS AND DIFFUSION PANELS AT THE REAR WALL AND CEILINGS WITHOUT MAKING SPECIFIC REFERENCE TO THE RESPONSE GRAPHS?

10. Purchase or make required acoustic treatment panels. Q. IS IT BEST TO BUY READY MADE PANELS OR MAKE THEM?

11. Install acoustic treatment panels.

12. Use software (e.g. Room EQ Wizard) to measure room response at listening position in treated room. Save graphs.

13. Compare actual room response graph with untreated room response graphs. If targets for decay time and/or frequency response not met re-interpret graphs of treated room and make appropriate additions/changes to acoustic treatment. Q. CAN I REALISTICALLY DO THE ANALYSIS MYSELF AND DECIDE ON THE REQUIRED TREATMENT AND IF SO HOW? OR IS IT ADVISABLE FOR THIS TO BE DONE BY SOMEONE WITH DEEP KNOWLEDGE OF ACOUSTICS AND EXPERIENCE IN THE FIELD?

14. Once targets for decay time and frequency response are met optionally install DSP system (e.g. Sonarworks SoundID reference) to smooth frequency response further by applying an active EQ curve.

15. Listen to reference material on monitors and headphones to ensure that there is consistency in tone, volume and stereo image.

#2

i would go with the longer room - you can see in the Benollo scale how much more even the mode distribution is per octave. then presuming the windows wall is the lower part of the pitch, i'd face that wall centered between the two windows.

#3

Hi Glenn,

Thanks for your feedback. Would you then recommend reducing the length dimension of the longer room from 7.2 metres to around 5.0 metres as has been suggested by others? If so then what kind of wall would you suggest inserting?

Kind regards
Jonathan

#4

no, i'd keep the longer room 7.2m as-is. the thing you will want to work on is the RT60 (or whatever it really is in a small room) and that can be via scattered absorption placement as well as the usual first reflection points, back wall, heavy drapes as needed etc. to get the room balanced.

#5

Hi Glenn,

Thanks for your feedback. The general rationale of shortening the length dimension seems to be based on having a more even distribution of room nodes. Do you think that issue can be fixed by acoustic treatment?

Based on my research I envisage the process of preparing my studio space as below. Is this sensible or OTT? how you would approach it?

1. Remove existing internal structural wall and replace with RSJ
2. Replace carpet with hard wood flooring or vinyl.
3. Position monitors in expected listening position set with equilateral triangle
4. Use software (e.g. Room EQ Wizard) to measure room response at listening position in untreated room. Save graphs.
5. Try moving listening position in a few locations closer and/or further from front wall.
6. Repeat measurements with Room EQ wizard.
7. Position monitors in best listening position as determined by Room EQ wizard from all the tested locations.
8. Interpret graphs to determine what acoustic treatment is required and at which locations to achieve target room response (e.g. decay time < 0.6 seconds, Nearly flat frequency response, stable stereo image). Q. CAN I REALISTICALLY DO THE ANALYSIS MYSELF AND DECIDE ON THE REQUIRED TREATMENT AND IF SO HOW? OR IS IT ADVISABLE FOR THIS TO BE DONE BY SOMEONE WITH DEEP KNOWLEDGE OF ACOUSTICS AND EXPERIENCE IN THE FIELD? OR IS THE TYPICAL APPROACH TO JUST INSTALL BASS TRAPS IN THE CORNERS AND ABSORPTION PANELS AT THE FIRST REFLECTION POINTS AND DIFFUSION PANELS AT THE REAR WALL AND CEILINGS WITHOUT MAKING SPECIFIC REFERENCE TO THE RESPONSE GRAPHS?

9. Purchase or make required acoustic treatment panels. Q. IS IT BEST TO BUY READY MADE PANELS OR MAKE THEM?
10. Install acoustic treatment panels.
11. Use software (e.g. Room EQ Wizard) to measure room response at listening position in treated room. Save graphs.
12. Compare actual room response graph with untreated room response graphs. If targets for decay time and/or frequency response not met re-interpret graphs of treated room and make appropriate additions/changes to acoustic treatment. Q. CAN I REALISTICALLY DO THE ANALYSIS MYSELF AND DECIDE ON THE REQUIRED TREATMENT AND IF SO HOW? OR IS IT ADVISABLE FOR THIS TO BE DONE BY SOMEONE WITH DEEP KNOWLEDGE OF ACOUSTICS AND EXPERIENCE IN THE FIELD?

13. Once targets for decay time and frequency response are met optionally install DSP system (e.g. Sonarworks SoundID reference) to smooth frequency response further by applying an active EQ curve.
14. Listen to reference material on monitors and headphones to ensure that there is consistency in tone, volume and stereo image.

Kind regards
Jonathan

#6

if i was going to shorten it, i would go with 4.75m - 4.875m on the length as that will be a smoother distribution and overall metrics which are beneficial.

Computed Information:
Room Dimensions: Length=4.75 m, Width=3.5 m, Height=2.6 m
Room Ratio: 1 : 1.34 : 1.82
R. Walker BBC 1996:
- 1.1w / h < l / h < ((4.5w / h) - 4): Pass
- l < 3h & w < 3h: Pass
- no integer multiple within 5%: Pass
Nearest Known Ratio:
- "6) M. M. Louden: 1971: 2nd best ratio" 1 : 1.3 : 1.9
RT60 (IEC/AEC N 12-A standard): 225 ms
- ±50ms from 200Hz to 3.5kHz = 175 to 275ms
- ±100ms above 3.5kHz = 125 to 325ms
- <+300ms at 63hz = 525ms
- 300<RT60<600ms
RT60 (ITU/EBU Control Room Recommended): 188 ms
- ±50ms from 200Hz to 4kHz = 138 to 238ms
- <+300ms at 63hz = 488ms
- 200<RT60<400ms
Absorbtion to achieve ITU RT60: 396 sabins
Volume: 43 m^3
Surface Area Total: 74 m^2
Surface Area Floor: 16 m^2
Surface Area Ceiling+Floor: 32 m^2
Surface Area Front Wall: 9 m^2
Surface Area Front and Rear Wall: 18 m^2
Surface Area Left Wall: 12 m^2
Surface Area Left and Right Wall: 24 m^2
Surface Area 4 Walls: 42 m^2
Surface Area 4 Walls + floor: 58 m^2
(sabins - front wall - carpet) / Left+Right+Rear wall: 35 %
(sabins - front wall) / Left+Right+Rear wall: 84 %
Schroeder Fc: 125hz
Frequency Regions:
- No modal boost: 1hz to 36hz
- Room Modes dominate: 36hz to 125hz
- Diffraction and Diffusion dominate: 125hz to 500hz
- Specular reflections and ray accoustics prevail: 500hz to 20000hz
Count (36.2-222hz) : Axials=13, Tangentials=54, Obliques=72
Count (36.2-100hz) : Axials=5, Tangentials=5, Obliques=1
Critical Distance (direct = reverberant field): 3.90m

#7

yes, you can definitely do the REW measurements and pretty sure you make some analysis :geek:

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