[machineage]

Hi there

First post here so be kind to me

I've just moved to my new home and I'm having a problem with my living room. The room is 23' x 16' x 8'. It's construction is concrete floor - brick / aircrete walls with dabbed on platerboard - plasterboard ceiling under trussed insulated roof.

My floor standing speakers have been with me in several different locations - and have always been fantastic in their low frequency output. So much so that I have had to attentuate them at times. However this new room is a different matter!

However much I boost the low frequency output - to the point of reaching the woofers excursion limit there is just no / very light bass reproduction?!

Having read a little about room acoustics - it would seem I have a problem with reflection and cancellation of the lower frequencies. Currently the room is pretty sparse save for some thin carpet with no underlay - and an old oak frame three piece suite.

I have read that bass traps would reduce the cancellation and allow me to hear the low frq's. However I would like to try some heavy soft furnishing first to see if that has any effect.

My initial question is regards to the carpet underlay. Would anyone be able to advise which would be best for absorbing the low frq's? I've looked at Cloud 9 and simlar PU foam - heavy (130lbs) rubber - and the very thick felt / pure wool type which appear to have the best thermal isolation properties. Wasn't the felt stuff similar to what was used in speaker cabinets to dampen the reflected waves?

Anyway - which is best - PU Foam - Rubber or Felt / Wool?

I'm not bothered about reducing sound transmission or impact noise by the way - the house is detached. Just helping with my bass reproduction.

Thanks!

[amioa]

if you play a bass tone and walk around the room, do you hear the bass in some areas and not others? if your listening position is flat then move forward 1 meter, hear much change?

I suspect though, that the dot and dab is sucking it all out.

[machineage]

Hi

Thanks for the reply.

Yes if I stand against the opposite wall and in the opposite corners to the speakers the bass is present - albeit not as prodigious as what I have been used to.

As I move around the room there is a clear difference in bass reproduction - again though it is pretty lightweight.

I have tried many positions with the speakers - 6 - 8 - 10 - 12 ft apart - at different distances from the wall etc...

Is dot and dab plasterboard known to suck the life out of low frequencies?

Thanks again

[amioa]

flimsy plasterboard will suck the bass out, if you put your hand on the wall and give the system something heavy to play, you will probably feel it more in the wall than you might expect, if you dont even have strong bass in the corners then something is definately sucking out the bass.

[AndyST]

With regards to bass trapping I don't think carpet underlay will be of much help. It just doesn't have the depth or mass to trap wavelengths at bass frequencies. Placing absorption at a boundary (walls, floor) is also the worst place as the particle velocity is lowest there, making it much less effective.

Is the placement of dedicated bass traps in the room a possibility?

It does sound like your walls/ceiling could be resonating and converting a lot of the bass energy into mechanical vibrations.

There's also the obvious question of are the speakers wired up correctly? If they're out of phase the bass will sound particularly weak.

[amioa]

Originally Posted by AndyST

Placing absorption at a boundary (walls, floor) is also the worst place as the particle velocity is lowest there, making it much less effective.

touching on this, you dont have to move the materials very far forward to make an improvement for 'normal' use, but for bass, you want to be looking at the front of the trap AT LEAST 4" from the boundary, ideally across a corner is best, makes good use of the theory without taking loads of space..the other option is to use well designed (but sadly expensive) bass traps.

dead right about the carpet and underlay too.