advice on sound treatment

[alexidoia]

Hi,
I have almost finished the room regarding sound insulation, I am now starting to think about the sound treatment.
According to this image, the red drawings are where I will put sound absorbers: 2 bass trap corners and three side wall absorbers tuned to the frequencies sticking in my room.

My ceiling is hard wood added to rock whool. And I have a hard floor.
Any advices or thoughts ? Have I taken the right choices regarding the place of my absorbers ? do I need to add more, say on the right wall for example ?
Thanks
Alex

[knightfly]

Alex, if this is a mix area can you add the speaker/desk location? Looks as if you may have symmetry problems if it's going where I would assume... Steve

[alexidoia]

No that is not the control room but the drum room.
thanks

[alexidoia]

I will construct my absorbers according to John's DIY Wall Units.
I have a couple question regarding the side wall units:
- can I do the timber slats in a parallel line or must I give them an angle like on this photo ?

- John recommends to vary the slats' width but how can I calculate the frequencies I want to target since the calculator (HELMHOLTZ RESONATOR CALCULATIONS) only take one input for the slats width ?
Thanks for your input.
Alex

[knightfly]

In your square room, it's even MORE important to build the absorbers with an angle as shown.

Varying the slot width isn't as important with these angled absorbers, because the DEPTH is varying as well - all you can get from the helmholtz calculator is to use the AVERAGE depth to get a CENTER frequency, adjusting slot and slat width (and thickness) for a center of around 300 hZ for a drum room (this is the typical kick drum's primary mode frequency)

With a square room, you should put a couple of those absorbers on TWO ADJACENT walls; this will kill flutter in the room, except for floor-to-ceiling - that should be treated with a "cloud"; look in the Acoustics forum in the sticky's under DIY acoustic projects, there are a couple of examples there... Steve

Try entering values into the calculator of 15,131,150,19 (top to bottom) - this is a unit that's 300mm deep (using half the depth as an average) and standard "1x6" lumber for slats, spaced 15mm apart...

[alexidoia]

except for floor-to-ceiling - that should be treated with a "cloud"

Thanks a lot Steve for your precious advices again.
I have lowered the (already low) ceiling for insulation purposes, I don't think I can't do anything else I'm affraid.

Try entering values into the calculator of 15,131,150,19 (top to bottom)

150 for the depth from wall would mean that the longest depth of the absorber is 300mm right ? Knowing that my room is already small I could also do 15,200,100,19, correct ? Should I do all my absorber with those value ? What about the corner absorber ?

[alexidoia]

Steve,
Would that be better ?

[knightfly]

Those numbers would also work; but your ceiling, from the sound of it, is still a hard surface, right? You'll get flutter between ceiling and floor if you don't put at least some 50mm or thicker absorbent over the kit - you will also get high frequency comb filtering effects from your overhead mics without this so I wouldn't recommend leaving your entire ceiling bare; there should be a cloud over the kit.

You can try it without; but don't be surprised if your high frequency doesn't please you.

With that many slats in the room, you may want to first try just standing some insulation batts across your corners; especially with a square room. If that sound good, all you'd need to do is either just cover them with cloth or build light frames, depending on which absorbent material you're using... Steve

[alexidoia]

there should be a cloud over the kit.

If you remember my first thread presenting the room, the ceiling is very low and made of plain concrete. I was about lowering it down leaving some air+insulation and adding a leaf made of 200mm of plain wood creating the mass+air+mass system needed for insulation. With that solution, I would not be abe to add a cloud on my very low ceiling.

The second solution I have, since I want to build a wooden terrace on the outer sideof it is to build it "air-tight" so that it stands as another leaf. That way I would still have a mass-air-mass system but the newest leaf would be outside and I could put my cloud inside without problem. What do you think of that ? This is quite another job, as the wood outside even thought it is made to resist to bad weather will always "work" and might loose its air tight capacity with time.

With that many slats in the room, you may want to first try just standing some insulation batts across your corners; especially with a square room. If that sound good, all you'd need to do is either just cover them with cloth or build light frames, depending on which absorbent material you're using... Steve

My step father is carpenter so wood is not really a problem.

[knightfly]

Putting your second "mass" outside instead of inside could work; I'm not familiar with your climate so I'm not sure what materials would be best; maybe a covering that's designed for flat roof use, such as one of the rubber sheet products?

I didn't suggest non-slats for corners because of trying to save wood; only your sound - my point is, maybe too MANY slats for that size room - you may like it better with a bit more high frequency absorption. You won't know for sure til you test... Steve

[alexidoia]

Back to the absorbers (while working on the roof ),
I have a question about the way to orient my absorbers, I am not sure it matters that much but each time I think something is not important, I realise on this forum it often actually is. so,

here we go with 3D representations:
on the following illustration, my absorbers allow me to save space and are more in harmonie with the room

here in two dimension view from the top


on this one, the esthetics is not at best but will it be more effective for the sound ?



I would prefer the first option but I would really like your input on that.
Would both work the same ?

Thanks
Alex