Exterior Drum Practice room build plan, Wales, UK

[badass_mcfunk]

The NORMAL way of dealing with that gap is to wrap a piece of OC-703 in black fabric and place that across the gap around the sides and top, and to also include silica gel under the fabric in some way across the bottom.

Thanks Stuart - thats what I'll do. Getting OC-703 is tricky in the UK but I believe that Rockwool do a product thats similar.

The other bit I'm still not quite sure of is the gap between the door frames, which will be the only area where air and moisture could get in. I was planning to close the gap between the two door frames with some strips of 3x1 timber to effectively make the gap much smaller (around 5mm) and then fill the 5mm gap with acoustic sealant- so the inner and outer frames are effectively sealed up but the join is via acoustic caulk. Is this the correct way to do it? I'll post some photos of this stage if the above hasn't made sense

[Soundman2020]

Getting OC-703 is tricky in the UK but I believe that Rockwool do a product thats similar.

That would work fine. Anything that is semi-rigid and not too dense would be good.

The other bit I'm still not quite sure of is the gap between the door frames,

Same thing! Semi-rigid slab of insulation wrapped in fabric, and press-fitted into the gap.

I was planning to close the gap between the two door frames with some strips of 3x1 timber to effectively make the gap much smaller (around 5mm) and then fill the 5mm gap with acoustic sealant

You could do that too, but set it backwards a bit into the cavity, skip the sealant, and put your fabric-wrapped insulation in front of it, with some wood trim on each side to make it look prettier.

so the inner and outer frames are effectively sealed up but the join is via acoustic caulk.

Unless you can find some "high elasticity" caulk, with a Shore 00 durometer rating of about 60 or less, then I'd skip that. Ordinary caulk is flexible, yes, but it can still create flanking paths for low frequency vibration, which might or might not be an issue, depending on how much isolation you are shooting for.

Oh, and Happy New Year!!!

- Stuart -

[badass_mcfunk]

Thanks as always for the excellent advice you've given over the past year Stuart - the time and effort you put into advising and guiding others is hugely appreciated. Hope you have a fantastic year.

[badass_mcfunk]

Hi

I need to bridge the gap somehow between the bottom of my door frames - picture below. I thought that cutting some timber to fit snugly between the two frames, resting on the 2x4 frame footers for each frame? To deal with the flanking issue, I have some 5mm hard neoprene strips, which I could put underneath this piece of timber - and also on both long sides of the timber where it makes contact with each door frame. This will effectively create a floating timber step in between the door frames, which will be flush with the bottom of the door frames.

door frame.JPG

Is this the right way to do this?

The sides and top of the door frames will have rockwool slab cut to size, wrapped in fabric and stuffed in the gap as previously discussed.

Cheers

[Soundman2020]

To deal with the flanking issue, I have some 5mm hard neoprene strips, which I could put underneath this piece of timber - and also on both long sides of the timber where it makes contact with each door frame. This will effectively create a floating timber step in between the door frames, which will be flush with the bottom of the door frames.

The concept is fine, but I wouldn't use hard neoprene for that. How hard is it? What is the durometer, Shore A? If you don't know, or if it is too high (anything above about 30 or so), then skip that and get some Sorbothane instead. That's the best stuff there is.

Put strips of that under the wood insert, leave a gap of a couple of mm between the wood and the door frame on each side, and caulk that with some high-elasticity caulk (not normal caulk), to seal the gap.

- Stuart -

[badass_mcfunk]

I have a little problem with my baffle boxes - I'm doing 4 of them (on outside and one inside for the inlet and outlet). I've done one of each so far, and I've realised that the inside box has the inlet and outlet in the right place for my requirements, but the wrong place to get 3 baffles in it in an alternating pattern. I have pasted a picture below.

baffle1.jpg

So - I'm guessing that 2 baffles (leaving out the middle one) would significantly impact on performance. However, would adding an additional one (as I have done in the below picture) work? There will be more of a squeeze for air to get around, which may be the issue?

baffle2.jpg

[Soundman2020]

I'm thinking that the entire silencer box needs a re-design! Once you add your duct liner on all the inner surfaces, there won't be anywhere near enough cross section left over.

The basic concept is that whatever cross sectional area you have inside the duct needs to be doubled inside the silencer box, and maintained for the entire length. So for example, if the area of the duct is 180 cm2, then you need at least 360 cm2 cross section throughout your silencer box. That could be, for example, 19cm x 19cm internal. Adding 25 mm on each side for the duct liner takes you to 24cm x 24cm for the internal dimensions of the wooden box itself, which also implies that your baffles would have to be spaced at least 24cm apart (since they will also have duct liner on them).

So sadly, I reckon you need to re-think your silencer plan, as I can't see it working out well like that. Air flow velocities will be way too high, there will be lots of turbulent flow, cause lots of air noise, plus the lack of impedance mismatch at the entrance and exit won't be providing the isolation that you are hoping for.

- Stuart -

[badass_mcfunk]

I've reconfigured the problem box so that the inlet is in the bottom (out of view) and the outlet will be in the top. I'm having a slight problem with the foam peeling back. I've used stronger glue in some places - the foam was self adhesive - but I'm concerned that it may peel in warm weather. I'm assuming a few tacks would be a bad idea as introducing hard surfaces on top of the foam would compromise the box?

image.jpeg

[Soundman2020]

That looks much better!

If you need to put a couple of tacks or staples in there to keep it firmly in place, that would not be a problem. It won't cause the box to not work: worst case, it will cause a bit of additional turbulence, but as long as you don't overdo it with dozens of tacks, you should be fine.

- Stuart -