Putting sub on fat rockwool panel, good for reducing transmission to neighbours?

[aquinox]

Hi! Is it a good idea to put a subwoofer on a 30cm fat panel rockwool, roughly 6x the area of the sub with the intent to lower transmission to neighbours downstairs? should I put a piece of wood on top of the rockwool so the material doesn't degrade by the weight of the sub?

[Drew Stephenson]

Yes it should help a bit in terms of decoupling and reducing direct transmission.
Whether it will help enough to make a difference is a matter with far too many variables to be determined by anything other than 'try it and see'.

[Sam Spoons]

This is one instance where foam might be better, definitely put a piece of MDF/ply on top to spread the load. I did the same with a bass practice amp and a single 50cm square egg box acoustic panel with MDF on the back, it was very resilient and definitely helped transmission through the floor.

[MarkOne]

funnily enough, I've just set up my home theatre sub (BK P12-300) on an MDF slab backed with 2 inches of acoustic foam, because it turned out it was causing a resonance on one of the floor beams that ran under my wife's seat. I was enjoying movies at theatre levels and she was complaining it was literally shaking her seat. We swapped places and it was true, her side of the lounge was really OTT.

decoupling it from the floor has made a huge difference.

EDIT: I should add I have calibrated the system with the receiver's ARC system with the measurements taken at 3 spots so the bass isn't turned up too much

[Wonks]

You can buy ready-made isolation pads for subs and guitar and bass amps.

E.g. Auralex do them. https://auralex.com/shop/iso-series/ and
https://www.amazon.co.uk/Auralex-Monito ... PMO1W?th=1

Definitely foam rather than rockwool for this application.

Like any isolation pad with foam, the foam needs to be within compression limits - not too lightly loaded or it will wobble, not too compressed so there's no resilience left in it. So don't go too large with the platform and amount of foam. I'd choose the smallest maximum weight one that you can fit the sub on. E.g. with an 80lb sub, go for a 200lb platform rather than a 300lb one.

If you go DIY, have a look at the commercial units for construction hints and foam thicknesses. The thicker the foam, the more weight is needed to get it compressed enough to work properly.

[Tomás Mulcahy]

As far as I understand, it doesn't work very well because the cabinet itself doesn't produce much vibration in the first place. Most of the vibration is through the air. If you can make the wall between you and your neighbour stop vibrating, that would work.

Some info on isopads here (bit messy, missing diagrams and as he points out some inaccuracies in the results due to methodology. But the principle is demonstrated).
https://ethanwiner.com/speaker_isolation.htm

[Sam Spoons]

Easy enough to test whether the sub is making the floor vibrate, just put your fingers on the cabinet when it's playing. If you can feel it vibrating then some of that vibration is going to get through to the floor. I guess you could also do the old glass on the wall (but on the floor) trick at the other end of the room too as a before and after test. A single piece of foam is cheap enough to risk giving it a go if you don;t have anything you can subvert. As Wonky says the trick is to get enough compression but not too much so the mass of the sub is floating.

[Hugh Robjohns]

Hi! Is it a good idea to put a subwoofer on a 30cm fat panel rockwool, roughly 6x the area of the sub with the intent to lower transmission to neighbours downstairs? should I put a piece of wood on top of the rockwool so the material doesn't degrade by the weight of the sub?

Short answer: no.

Longer answer: I wouldn't use rockwool in this application. High density foam would be more effective and cleaner! And it wouldn't need to be 30cm high either... 10cm would be more than enough, and 5cm might be okay if it has the right density. Basically, you need the foam to be compressed slightly (by maybe 15% or so) when the subwoofer is placed on top.

And yes, a board on top to spread the load is a good idea (and would also help to protect the foam.

But while an isolation platform like this will help by reducing the direct transmission of mechanical vibrations from the subwoofer into the floor, and thereby into your neighbour's room below. However, the LF from the sub is still going to cause other things in the room to vibrate sympathetically, especially the drywall panels and other fittings, and once that energy is in the walls it will find a way through the building to your neighbours.

So it will undoubtedly help... but don't expect a miracle cure!

[DanDan]

High density fibre boards are indeed used to float floors and such. But there are much more targeted products available for speaker or machine isolation. Polyester is sort of in between foam and fibre, e.g. Autex or Caruso Isobond. Subs are typically on the floor so airborne transmission from cone to floor is strong. Most speaker designs strive at great lengths for no cabinet vibration. So results from isolation are very limited. That said, a local club had 9 serious subs under the stage. Doors and windows at the other end of the building were moving...... We installed Mason isolators with the correct specs for the weight of each subs. Big improvement. https://www.mason-uk.co.uk/all-products/

[Sam Spoons]

The issue I helped a mate deal with was a bedroom in a semi with joists that butted into the party wall, an vibration, be it footsteps or a bass amp, transmitted directly into the wall and thus through to the neighbours bedroom. Putting the bass amp on an MDF platform on top of an egg box acoustic foam panel made a noticeable difference, LF sound will be transmitted much more efficiently through a structure than it is through the air so decoupling the amp from the floor had a disproportionate effect.

[aquinox]

Thanks for all the replies! I had it on a piece of black felt insulation material, now I used some different material and then some hard wooden material on top, all on top of a carpet. Would further height increase help more? or top it off with soft material again abvoe the wood?

[Martin Walker]

Hi aquinox!

I'm afraid your Google image doesn't show up here (even after I logged into my Google account), but I suspect that we would find it difficult to advise on which combination of layers would have the greatest effect.

The important thing is to 'decouple' your sub from the floor, so I suspect that several inches of high density rockwool (probably 100Kg/m3 or greater) would be needed - under carpet felt insulation tends to be much thinner than this.

Martin

[aquinox]

Take 2!

[Wonks]

The important thing is to 'decouple' your sub from the floor, so I suspect that several inches of high density rockwool (probably 100Kg/m3 or greater) would be needed - under carpet felt insulation tends to be much thinner than this.

Martin

I thought we'd all agreed above that acoustic foam would be a lot better than Rockwool? And Rockwool will need to be enclosed in fabric to stop it shedding fibres even if just on a wall, but the vibrations from a sub are likely to keep breaking bits off that will then make their way out through the fabric due to the vibrations.

[zenguitar]

Take 2!

Sorry, the link doesn't work. You appear to be linking to a web page rather than the image direct. And when I access the link direct to test I am directed to an error 403 page.

Andy

[Martin Walker]

The important thing is to 'decouple' your sub from the floor, so I suspect that several inches of high density rockwool (probably 100Kg/m3 or greater) would be needed - under carpet felt insulation tends to be much thinner than this.

Martin

I thought we'd all agreed above that acoustic foam would be a lot better than Rockwool? And Rockwool will need to be enclosed in fabric to stop it shedding fibres even if just on a wall, but the vibrations from a sub are likely to keep breaking bits off that will then make their way out through the fabric due to the vibrations.

Sorry, you're right, acoustic foam it is

I hadn't been keeping up with all the answers, but mainly posted to point out that relatively thin felt insulation wouldn't do the job, because you'd need several inches of decoupling