Small mixing room treatment project

[A.H.I.]

Hello!

First of all, I would like to thank everyone on this forum for everything I learnt from it! I helped a friend to build a little project studio in his basement and it worked really, really well, thanks to all the knowledge from this site and a few books I bought along the way.

Recently I moved to a new house in which there's a little room I would love to convert to a mixing room. The room's dimensions are 12' 1'' X 9' 5'' X 8' 7'' and I can't do any modifications because it will require major structural work. My goal is really to compose and mix, but I'm willing to go all the extra-miles to make it sound as good as possible. The acoustical isolation is not critical in my case, I usually mix and play around 75-85 db. An important detail worth mentioning is that the left wall has a glass block section in it (roughly 10' x 10').

I really would like to attempt to soffit mount my monitors and then acoustically treat the rest of the room accordingly (super chunks, cloud, broadband absorbers, etc.).
I recently acquired Presonus S8 monitors that would like to flush-mount (according to Mr. Sayer's soffit plans) and which seem to be compatible with that method of installation (adjustable LF EQ at -3 and -6db) + very low power consumption (25W input and 180W output: thank you Class D) which leads to lower heat output from the speaker enclosure. I also have a 2.1 kit of Mackies (MR5s with 10'' sub) and a pair of Avantones. I think of simply putting those on stands.

I'm adding a couple of Sketchup renders of the room to give you a better idea. As you can see both door openings get in the way of the super chunks, but I will figure something out.

The little wardrobe which is attached to the room will hopefully be converted into a vocal/amp booth. However it might be too small (5' 7'' X 5' X 6' 7'') but perhaps rendering it mostly ''dead'' will help.

Does my little project seems realistic? Did I miss something crucial?

Thank you in advance for your time!

[A.H.I.]

I've just read the very detailed Moto's thread and it is quite amusing how many similitudes our rooms share!
Is there anything that might differ in my case from that thread since we have a very similar dimensions and goals?
Thank you in advance!

[Soundman2020]

Hi there "AHI", and Welcome!

The room's dimensions are 12' 1'' X 9' 5'' X 8' 7''

It's a reasonable size. Even though it is small, it has a slightly higher-than-normal ceiling, which is good.

I really would like to attempt to soffit mount my monitors

Excellent idea!

I recently acquired Presonus S8 monitors

Coaxial! Nice. That should work very well. You'll need to be more careful with the ceiling, floor and desk, due to the higher vertical dispersion, but apart from that, they should be good for you room. The higher ceiling helps with that.

25W input and 180W output:

??? Not so sure about that!!! You can't get more power out of a system than you put into it! Laws of thermodynamics.... Maybe you mis-read the spec? Where did you see that?

The little wardrobe which is attached to the room will hopefully be converted into a vocal/amp booth. However it might be too small (5' 7'' X 5' X 6' 7'') but perhaps rendering it mostly ''dead'' will help.

For a small iso-booth like that, yes, you'll have to make it rather dead. Also, you'll need to put a very massive (heavy) door on there, to ensure that the closet does not affect the room acoustics, and damage the symmetry.

Does my little project seems realistic? Did I miss something crucial?

Looks fine to me!

Is there anything that might differ in my case from that thread since we have a very similar dimensions and goals?

Your speakers. They have much larger dispersion angles in the vertical plane, as they are coaxial. So your ceiling will need more attention (and your floor to, to a certain extent).

- Stuart -

[A.H.I.]

Thank you for your detailed reply Stuart!
Based on your answers, soffits would be the ideal way to mount those coaxials. So soffits it will be!
Before proceeding and making expensive mistakes I would like to ask a few more questions:

1) For the soffits I mentionned that I would like to adapt Mr. Sayer's design, but I keep going back to the simplicity of Thomas' one (Barefoot). So perhaps I will end up with a mix of both. Is it a good idea to substitute the acoustic hangers by a super chunk on the bottom part of the soffit to absorb even more bass?

1.1) Is it a good idea to angle to top part of the soffit? I would like to do it for ''cool-looking factor'' alone, but is there any acoustic benefit of doing so in my situation?

1.2) I kept reading about the soffits and one thing kind of puzzles me: the width of the bezel. There's a formula that Eric Best sites: f3 = 4650/x where x is the baffle width in inches. I checked in the PreSonus documentation and they mention 250Hz being the cutoff frequency for the bass attenuation. Would it make sense to create a rigid baffle of 18.6'' that would match that 250Hz? Or should it even be 500hz, since the formual gives us the -3db point?.. I'm a bit confused...

2) I have a preference of working with rockwool insulation and around Montreal, Roxul Safe N Sound is readily available. But that particular board has a density of 40kgs/m2 (with absorption coefficients of 0.52 (at 125Hz) and 0,96 (at 250Hz) per 3'') (http://www.roxul.com/files/RX-NA_EN/pdf ... EET_EN.pdf). My question is: would it be advisable to use denser kinds of rockwool, at least in the superchunks, to increase overall absorptions in a small room like mine? For example this kind of rigid board: http://www.roxul.com/files/RX-NA_EN/pdf ... EET_EN.pdf (with absorption coefficients of 0.75 (at 125Hz) and 0,82 (at 250Hz) per 3'').

Thank you once again in advance!

Pavel

[Soundman2020]

but I keep going back to the simplicity of Thomas' one (Barefoot).

Don't be fooled by the diagram! Thomas is only showing a very small part of the entire soffit: just the part that actually supports the speaker.

Is it a good idea to substitute the acoustic hangers by a super chunk on the bottom part of the soffit to absorb even more bass?

I would stick with the hangers, to be honest. They are very effective, since they combine a couple of different acoustic actions into one.

1.1) Is it a good idea to angle to top part of the soffit?

Angle in what way?

1.2) I kept reading about the soffits and one thing kind of puzzles me: the width of the bezel. There's a formula that Eric Best sites: f3 = 4650/x where x is the baffle width in inches. I checked in the PreSonus documentation and they mention 250Hz being the cutoff frequency for the bass attenuation. Would it make sense to create a rigid baffle of 18.6'' that would match that 250Hz? Or should it even be 500hz, since the formual gives us the -3db point?.. I'm a bit confused...

That equation is for figuring out the center point of the baffle step response issue, that's all. It is not related to the cutoff frequency of the speakers, but to the frequency where the power imbalance starts to be significant. It's the mid-point of the transition from full-space radiation to half-space radiation. If you use that equation on the width of your speakers, you will know where the center of the baffle step problem occurs. If you then apply it to the width of your soffit, you'll know how much lower down the spectrum you are forcing that baffle step to happen. If you are able to force it down below the bottom end of the speakers extension, that's great, but you'd need a large soffit to do that.... unless you are also using a sub along with your two mains, in which case you only need to get the soffit baffle wide enough that the baffle step center frequency is significantly lower than the cross-over frequency that you are using for your sub. In most small rooms, that might not be possible either. But even if you can't get things to go down low, the soffit is still a great idea, and will definitely improve the overall room acoustics.

2) I have a preference of working with rockwool insulation and around Montreal, Roxul Safe N Sound is readily available. But that particular board has a density of 40kgs/m2 (with absorption coefficients of 0.52 (at 125Hz) and 0,96 (at 250Hz) per 3'')

That''s fine. A bit more dense would be better, but there's no problem with that stuff.

My question is: would it be advisable to use denser kinds of rockwool, at least in the superchunks, to increase overall absorptions in a small room like mine? For example this kind of rigid board:

Don't go too dense! Many people assume that higher density will be better for low frequencies, but that's wrong. There's an optimal density for each application in acoustics, and if you go higher than that you start losing low frequency performance. More dense is actually better for high frequency absorption, and worse for lows.... At 128 kg/m3, that stuff is really dense. That's about twice as dense as the optimal. I would go with the 40 kg/m3 stuff, or see if you can find something around 50 to 60.

- Stuart -