How to stop sub vibrating?

[CAPP0]

We've bought a low-level cabinet which sits underneath the (wall mounted) TV and sound bar. The sound bar has a sub, which was previously sat on the floor in the corner.

I'd like to put the sub out of sight in the cabinet, and it fits, but having tried that out today, it vibrates the cabinet at certain frequencies of bass. (It wasn't doing that before, it was on the solid floor next to the cabinet, and the vibration doesn't happen). I've put felt pads under the shelf which the sub sits on in the cabinet, and another set of felt pads under the sub between it and the shelf, but that hasn't cured it.

Any other things I can try?

TIA.

[Caddyshack]

I don’t think you will stop it, you have probably just found the resonance that makes the cupboard vibrate badly at.

[Ledaig]

You will need to change the mass of the cabinet to modify its resonant frequency. Steel plates stuck to the inside could help, but could also just find the cabinet seeking out another frequency to harmony with.

Edited by Ledaig on Tuesday 27th September 23:01

[darreni]

Try blutak order the sub & under the cabinet

[CAPP0]

Thanks all - will look into those, bearing in mind Caddy’s point too.

[stevoknevo]

Sub bass frequencies are rather long and essentially you've just put a massive sub in a tiny room by putting the sub inside the cabinet - even a powerful sub in a large room is capable of rattling its surroundings at certain frequencies - but you've also increased the relative size of the subs cabinet into being bigger than it is in relation to your room.

If the sub is ported you could try blocking the port with a pair of rolled up socks and sitting the sub on a concrete slab or speaker pad or rubber isolation footers intended to go under washing machine feet (I use these on my sub but it's in open space and rather large) You'd then need to isolate everything within the cabinet that's either suspended on the structure or capable of being resonated (shelves/doors/drawers and drawer bottoms etc)
I'm not saying it's impossible but it could take a helluva lot of trial and error to get it to stop vibrating especially given the sub likely covers a wide spread of lower frequencies to support the sound bar (potentially 120hz and below, possibly starting a fair bit higher than that depending on the soundbar)

Ask in the PH HiFi and Home Cinema forum as there's very knowledgeable folk, including speaker designers, in there.

[lufbramatt]

Resonant frequency of the cabinet will be affected by it's weight and stiffness. Could try adding braces to the cabinet or stick something heavy in it- paving slab etc. to move the resonance out of the range of the subwoofer.

[Paul Drawmer]

I reckon you need to change the cabinet into a cover.
If the sub is downward facing, sit it on the bottom of the cabinet, but remove most of the floor.
Otherwise remove the back of the cabinet.

In either case, beef up the cabinet with 18mm ply for as much of the internal structure as you can. If you can, get a small paving stone in there.

It's never going to work really well, but as a compromise, make it heavy, give the sub plenty of air.

[TonyRPH]

Fixing some Dynamat into strategic areas around the cabinet will likely damp out the resonance.

[CAPP0]

Thanks again all. I've had to take it out of the cab for now, as I've been too busy to try and sort it but the noise is irritating! I'll look at the suggestions above and see whether any of them are viable.

stevoknevo said:

Ask in the PH HiFi and Home Cinema forum as there's very knowledgeable folk, including speaker designers, in there.

Thanks for that, I had it in my head that there was a forum for this but couldn't see it - because I have my "view" filtered to Favourites only!