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Studio Build 500-year-old French Basement
Old 24th October 2019
  #1
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Studio Build 500-year-old French Basement

I’m looking for an acoustician/studio designer who can help me build a new studio in France. I am in the planning phase.

The space is weird but I don’t have a choice. There is a 40m2 live room with high ceilings, and a 40m2 control room with a very low curved ceiling (2.2m at the center). It’s underground and completely enclosed in rock and dirt.

Is it possible to build a great-sounding control room in this space? I will attach some pictures. I apologize they are upside down, I don’t know how to fix it.
Attached Thumbnails
Studio Build 500-year-old French Basement-e694064b-3ccf-468a-b60b-5141b0f5ff23.jpg   Studio Build 500-year-old French Basement-69c4ec71-2e48-4f52-abb9-09c261bed0bd.jpg   Studio Build 500-year-old French Basement-3b8b92ec-e55c-499c-95bf-98ba44b69b94.jpg  

Last edited by chrismeraz; 24th October 2019 at 05:06 PM..
Old 24th October 2019
  #2
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Your photos are showing upside-down! Either that, or your room has a curved floor and flat ceiling...

It's going to be hard to get decent acoustic response in there. The two reasons are, as you already figured out: the concave ceiling, and the low height. There's a possible third issue: the length and width. You said 40m2, but didn't say how long and wide the room is.

OK, it's not impossible to use that room, but it's not going to be easy to treat it, and the results aren't going to be fantastic. But they can still be decent, and usable, depending on what you want to do in there. Is this going to be a high-end commercial facility, for turning out hit albums for A-list stars? Probably not gonna happen! Is this going to be a personal hobby studio for having fun with your own mixes, entertaining friends and family, and mixing occasional demos for acquaintances? Sure, it can work just fine for that! I'm guessing that the purpose is probably somewhere in between those two extremes. The more your needs are towards "high-end pro studio", the less likely this room will serve the purpose. But the closer your needs are to "personal hobby studio", the more likely it is that you can achieve success. I've done worse rooms (smaller floor area) with success, as wanted by the studio owner, so there is hope. It's all a matter of expectations vs. reality. There's also the issue of budget, time, and dedication; With a lot of money, plenty of time to design and build and treat and tweak, and real dedication to excellence in design and construction, it can be quite good. On a shoe-string budget, or if you need to have it running by next week, or if precision isn't your thing, then it's not going to be very good at all.

Sorry I can't be more descriptive and specific than that! But hopefully it helps a bit.


- Stuart -
Old 24th October 2019
  #3
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Yes I forgot to give you the dimensions! 10 m x 4 m x 2.2 m.

I have a big budget for this.

I figure the concave ceiling wouldn’t be a problem if I could completely cover it with 40cm of fiberglass. However, I can only put about 20cm of insulation before I’m bumping my head on the ceiling, so I’m looking for someone with more experience than me to help me come up with options.

My goal is to work in there every single day and to be able to hear exactly what I’m doing. It isn’t a hobby, it’s how I make my living.

Last edited by chrismeraz; 24th October 2019 at 10:59 PM..
Old 26th October 2019
  #4
Can you dig deeper?
Old 1st November 2019
  #5
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I tried! But it’s all rock underneath one inch of dirt.

I’m in touch with a professional designer. I’ll let you know what we come up with.
Old 27th January 2020
  #6
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Quote:
Originally Posted by chrismeraz View Post
My goal is to work in there every single day and to be able to hear exactly what I’m doing. It isn’t a hobby, it’s how I make my living.
If this is true, choose a space which reflects this. I know this is blunt and not what you want to hear, but it's the reality. As a studio designer, this is below the absolute minimum height I will agree to work on with a client. I would never advise investing time and money into a place with such low ceilings. The situation is also much worse than a room of typical residential construction since the problematic dimension is such a dense & thick mass, and worse again by the concave shape.
Old 13th February 2020
  #7
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Quote:
Originally Posted by TomStevens View Post
If this is true, choose a space which reflects this... I would never advise investing time and money into a place with such low ceilings. The situation is also much worse than a room of typical residential construction since the problematic dimension is such a dense & thick mass, and worse again by the concave shape.
Hi Tom, thanks for your input. The space is free, so that's why I want to try and make it work. The design concept is the Newell Non-Environment control room, with speakers built into a hard front baffle, and broadband absorption everywhere else. Here's a rough sketch of the floor plan (hallway to the recording space is on the left side):



Once the hard front baffle is built, the effective length of the room will be about 3.2m, which supports modes down to about 52Hz. A 1m deep membrane and waveguide absorber system (shown in brown in the drawing above) can be effective down to 30Hz, so that problem is manageable.

Now we come to the ceiling. We can do some ray tracing and see that the slightly concave shape will not have much of a focusing effect. The model below is to scale (though ray tracing was admittedly done without a protractor):



Because the ceiling is so low, we are limited in the amount of absorption that can be placed on the ceiling. An average of 20cm (30cm near the center, 10cm near the edges) is the maximum that can be installed. Since the incident energy is coming into the fiberglass at an angle, the 20cm fiberglass will act as if it were thicker. It should approximate the performance of 30cm of low-density fiberglass. The performance of both is shown below:



So, some of that reflected energy will be absorbed by the ceiling, but what about the remainder?

The remaining 20% of sound energy reflected at 100Hz (and up to 60% reflected at 40Hz), will of course cause interference at the engineer's position. However, on this occasion, the low ceiling is an advantage, because the path length difference between the reflected and direct sound is only 0.8m. Knowing that phase shift (in degrees) is:

Phase shift = 360 x path length difference / wavelength

we can calculate that the phase shift for sound energy at 100Hz will be only 85 degrees. The phase shift for a 40Hz signal will be even smaller, at 33 degrees.

Fortunately, any phase shift below 90 degrees is near enough to a minimum-phase shift and can be corrected using EQ! (Newell, Recording Studio Design, sections 11.5.1, 23.3.3, and 23.5); a HPF EQ with a slope of 6dB/octave and a 3db adjustment range will be sufficient to correct this problem.

There is one last acoustical problem to be solved in this room. We have discussed the first reflection, but we have not discussed the resonant energy in the vertical mode. As the room is 2.1m tall, on average, the lowest mode that can be supported is 83Hz. We have a minimum of 50% absorption in the vertical mode at 83Hz. I have tried to estimate how many vertical round trips the sound would have to make before being attenuated to -60dB, but I think it is impossible to calculate. If it takes less than 500ms to make all those trips, I would say we're in good shape.
Attached Thumbnails
Studio Build 500-year-old French Basement-floor-plan.jpg   Studio Build 500-year-old French Basement-concave-ceiling.jpg   Studio Build 500-year-old French Basement-porous-absorber-calculator-2.jpg  

Last edited by chrismeraz; 14th February 2020 at 10:32 AM..
Old 13th February 2020
  #8
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Quote:
Originally Posted by chrismeraz View Post
I’m in touch with a professional designer. I’ll let you know what we come up with.
What happened if you don't mind?
Old 13th February 2020
  #9
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Quote:
Originally Posted by JayPee View Post
What happened if you don't mind?
Well, I decided I'd better wait before spending money on that, so I didn't bring him in yet. I'll decide in three months whether to proceed or not. But I'm still thinking about it, making engineering studies, and making the plans in 3D to see if I can fit in this space. I have a one-room studio right now, it makes tracking decisions very difficult because I have to work on headphones while tracking.
Old 13th February 2020
  #10
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"The 4m length of the room supports modes down to 21Hz, ... " Misprint? Lowest mode should be: c /4 m / 2 => about 43 Hz. Pressure mode should start to be noticeable slightly below that with solid walls.
Old 14th February 2020
  #11
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Since you don't have a rectangle regular room, I wouldn't bother with calculating room modes and such. You should measure your room.
Old 14th February 2020
  #12
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Quote:
Originally Posted by Adhoc View Post
"The 4m length of the room supports modes down to 21Hz, ... " Misprint? Lowest mode should be: c /4 m / 2 => about 43 Hz. Pressure mode should start to be noticeable slightly below that with solid walls.
Hey, you're right! That means the lowest vertical mode will be around 82 Hz, which is much more manageable. I'll correct that in my post above.
Old 14th February 2020
  #13
That'll be an interesting studio for sure.
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