Construction Material for soffits?

[LRRecords]

Hello - Brett here from LRRecords, Perth, Western Australia..

Have Finally built the studio room and am now building soffits for my JBL 620B powered speakers. Was wondering if I can use leftover 16mm gyprock (drywall/plasterboard) sheets for the soffit baffles (soffit front)? I have seen most people use mdf, timber or plywood for this application, but is plasterboard alright to use? From what i gather the main things we are after are a rigid front baffle, an extension of the speaker faces, preferably decoupled from the rest of the soffit frame and/or speaker stands and definitely decoupled from the speakers. Also the lower half of the soffit baffles to be insulated with a rigid insulation or similar to tackle audio reflections coming from the back of mixing console, racks, etc..

Im using the last bits of structural pine timber for the soffit framing and mdf and particle board bits for the speaker stands and cabinets. Aware of running low on the mdf and keen to save some peices for the panel absorbers to hang within the soffits.

cheers to everyone who inputs here on the forum....valuable...

[Soundman2020]

Hmmmmm.... Good question! Personally, I think that should work, if your framing is beefy enough to keep it rigid, but I'm hesitant to just come out and say "Go for it! No problem!", since soffit design and construction seems to be mostly science but with a small percentage of voodoo. And there also seem to be different schools of thought on the "best" way of doing it. So maybe one of the "soffit voodoo practitioners" can comment better on that, and tell you if you also need any eyes-of-newts or toes-of-frogs!

But from my point of view, I don't see why a couple of layers of 16mm drywall, firmly braced, shouldn't work.

the panel absorbers to hang within the soffits.

Panel absorbers? Inside the soffits? I don't see how that would work. What would be the purpose? What frequency would you tune them to?

- Stuart -

[LRRecords]

Thanks Soundman2020 for your quick reply...

Yep I will go ahead with using the plasterboard on the soffit baffles. I can still finish with a plywood over the top of the plasterboard, or even just a good paint-job?

Panel Absorbers? I meant Acoustic Hangers (Using the correct language/terminology on the forum is really important...) - as per Johns designs here:
http://www.johnlsayers.com/phpBB2/viewt ... p?f=1&t=66

awesome..

[Soundman2020]

I can still finish with a plywood over the top of the plasterboard, or even just a good paint-job?

Provided the plywood is very thick and rigid, then no problem. But I wouldn't use a thin veneer of plywood.

I think you already know this, but it doesn't hurt to recap: the front panel must be as massive and rigid as you can possibly make it. Some people have used brick and concrete ( ) That's the level you should be aiming for.

Panel Absorbers? I meant Acoustic Hangers (Using the correct language/terminology on the forum is really important...) - as per Johns designs here:

Ahh yes: hangers. They are just a little bit different from panel absorber! Yes, hangers are a good idea for the lower section of soffits. John swears by them!

- Stuart -

[BriHar]

I've come across numerous instances where people are using plasterboard for the soffit baffles.
I am also going to use it (Fermacell in my case) for my own - however I am not going for the full soffit effect.
The only problem with plasterboard is that it's brittle and easily scratched, so either a few coats of good quality hard enamel or a facing layer of other material. I've seen some face their baffles with ceramic tiles - looks very nice.

You mention saving MDF to use for making hangers. I assume you mean for use as cores. If you check out hangers on this site you'll see that the tendency plus the advice from John, is to use soft fiberboard (homosote) for the cores as opposed to heavier, denser cores - I believe the soft cores are more effective for deeper bass handling.

[LRRecords]

Cheers BriHar,

Yep, worked on the acoustic hangers today. Used cardboard boxes from neighbours cider cartons - compressed and stacked for the cores, with a layer of rockwool each side, built small frame to then finish with old bed sheets to pull/compress rockwool a little bit. Hung these in soffit using cable ties. Will get some pics up asap.!

Using left over plasterboard on baffles and will cover with a plywood or mdf...

All the input here - much appreciated.

[Soundman2020]

built small frame to then finish with old bed sheets to pull/compress rockwool a little bit.

Not sure I understand that part: Why do you want to "pull" and "compress" the rockwool? That will change its acoustic characteristics in an unknown manner...


- Stuart -

[BriHar]

I'm also a bit confused. It almost sounds like you've mixed up hangers with absorber traps.

I'm currently building my hangers and hope to post some pics soon, but that won't be for a bit as I'm off to Santorini for a week.