Soundman2020 - Studio Design Forum

so - the thick material in the box - good.
on the buzzing - the noise is related to the speaker output and not the air flow?
if the space around all of that is filled with insulation (which is will be evenutally), i'd suggest in most cases this eliminates the problem.
one other option is to make a "hard duct" using the duct board to create the ducting (a couple of right angles), as this tends to be more damped and less prone to vibration the resonant frequency will be much higher and thus more easily attenuated. a short section of flex to connect to the bottom of the speaker box connector.

Thanks Glenn. Yes, definitely related to the speaker output, it's fine with airflow.

Cheers!
Jennifer

I removed the "plastic barrier between the duct and the glass wool". It's that brittle crinkly type plastic, really noisy when it moves, like a crisp (potato chips for USA?) packet. I replaced it with food wrap (cling film) round the duct and that is silent. Problem solved.

Cheers!
Jennifer

eggsellent! yes, we call "crisps" = "chips". handy reference: https://www.mashed.com/279089/is-there- ... nch-fries/

Good article. Also in Scotland, "A fish supper" is what you ask for when you'd like "fish and chips"

good to know as me thinks our daughter wants to do some touring of the UK

I stuck the cooker hood filter material to the inside of the soffit speaker box with contact spray glue. Unfortunately there wasn't as much room at the top so I couldn't fit the duct liner there as I'd hoped to do.
Duct flanges on the plenum and bottom of the speaker box.
I've added some more horizontal framing to the soffit structure to make it stronger and more rigid. I'll do something similar round the sides soon. Nice to be able to re-use some old table legs I've been keeping for years in case I found a use for them one day
I wanted to make sure the horizonal soffit structure beams did not pull the soffit face inwards or push it outwards when it was screwed into them. So I attached these beams from behind with these pocket holes when the baffle face was in place
Soffit on the other side done the same way, and also has some of the flex duct attached. The top flex duct comes out the back of the speaker box and will emerge on the side of the soffit.

very nice! the extra rigidity should help as it raises the resonant frequencies which are more easily damped when you layer in MLV and/or fill up the space with insulation.