Using rugs for acoustic treatment

[seen-da-sizer]

Originally Posted by johnnyc

Obviously rugs will be terrible broadband absorbers. But how about using them at the side first reflection points in a room already filled with bass traps? Visually would give the room some character.

AFAIK at the 1st reflection points, there should be broadband absorbers. Therefore, if rugs are terrible at it, don't use them for that.

[johnnyc]

Hmm, I thought the corners were best for bass trapping. With the sides more for mid-high absorption to improve imaging and clarity. Perhaps I am mistaken.

[seen-da-sizer]

Originally Posted by johnnyc

Hmm, I thought the corners were best for bass trapping. With the sides more for mid-high absorption to improve imaging and clarity. Perhaps I am mistaken.

The way I understand it, you want to create a reflection free zone. That means no reflection of any kind (LF, HF, or Mid Band). A rug may absorb some mids, but I am guessing that it will also reflect some HF, depending on thickness, material, construction that was used. Not exactly what you want to achieve.

I am not a professional, but a rug would not be my first choice for the 1st reflection points. But I would try them in the further back of the room. Ultimately, taking before and after measurements may be the only way answer your question for sure.

[kasmira]

I would not recommend it. Rugs are not absorbers of any broad frequency range at ALL. They simply suck up a very narrow frequency range. It would be like putting a very narrow and deep notch/band reject filter at 1k in your early reflections. Carpet/rugs is usually suggested for helping combat floor-ceiling flutter echo in rooms, which it works great for.

[pardonmytone]

Originally Posted by johnnyc

Obviously rugs will be terrible broadband absorbers. But how about using them at the side first reflection points in a room already filled with bass traps? Visually would give the room some character.

I am wondering the same thing. I am aware that a lot of studios avoid the use of rugs to give a more "natural" sound to the room.

However, for a narrow frequency band as you say, I am wondering if it would be useful - particularly at known bands of cancellation frequencies from the speakers (due to their proximity to walls, etc.), say between 150Hz and 300Hz.

Anyone care to chime in?

[kasmira]

Originally Posted by pardonmytone

I am wondering the same thing. I am aware that a lot of studios avoid the use of rugs to give a more "natural" sound to the room.

However, for a narrow frequency band as you say, I am wondering if it would be useful - particularly at known bands of cancellation frequencies from the speakers (due to their proximity to walls, etc.), say between 150Hz and 300Hz.

Anyone care to chime in?

No, the carpet wouldn't absorb frequencies that low at all. Plus, usually, other than the main cube room mode with an epic decay time its not hard to tame peaks. Nulls are much harder to control.

[Sen]

Wrap a few 4" thick slabs of rockwool or semi rigid fibreglass in some fabric and hang on the side walls. It will take you much further than foam, rugs carpet etc, and won't break the bank either.
Usually RFZ is not treated for very low frequencies anyway, it's usually comb filtering you're trying to avoid in the mid and high frequency bands.
Having said that, while you're at wrapping some insulation in fabric, make a few frames with 3/6/9mm plywood front as well and fill them with insualtion.
Those (panel absorbers) will go down lower and will restore some liveliness in mid and high bands, should the wideband absorbers deaden the room a bit more than you'd like.
Good luck

[Glenn Kuras]

For early reflection points I recommend no less then 2" with a 2 inch gap. If you want to make sure then I would use 4".

[johnnyc]

So I put up 4" panels on the sides with a 3" gap. My original thinking with the rugs is I would need more help taming everything, and since the room was small the bass traps would be best utilized in the corners. But right now have 6 of the 4" panels in the room and an additional 3 3" ones. Liking the results. Might still buy some rugs, but might only need them for aesthetic purposes now.

Thanks for the advice guys.

[pardonmytone]

ok then. thanks for clarifying then guys! can't really have a 2" panel on the floor!

[localhost127]

Originally Posted by pardonmytone

can't really have a 2" panel on the floor!

block it via the desk or attenuate the indirect signal by means other than absorption.

[localhost127]

Originally Posted by johnnyc

Obviously rugs will be terrible broadband absorbers. But how about using them at the side first reflection points in a room already filled with bass traps? Visually would give the room some character.

broadband porous absorbers utilized to attenuate indirect specular reflections need to be broadband with respect to the bandwidth of the specular region. the lower cut-off in typical residential rooms is ~250-300hz; as such, you're porous absorber needs to be effective down to that range. since porous absorption is a velocity-based absorber, it needs to be sufficiently thick and/or spaced from rigid boundary such that the insulation is placed into areas of relatively high particle velocity for those lower (longer) wavelengths. you could also attenuate the indirect specular reflection by other means, such as redirection via a large (with respect to wavelength) flat reflective panel angled such that the reflection is redirected away from the listening position (eg, towards rear wall where it can be diffused and the energy returned to the listener as a laterally arriving diffuse-field).

carpet or any other thin porous absorber will merely attenuate the mid-HF specular band while the lower region is allowed to persist - which essentially colors/filters/eq's the reflection of which will still superpose at the listening position with the direct signal (albeit colored).

[DanDan]

broadband porous absorbers utilized to attenuate indirect specular reflections need to be broadband with respect to the bandwidth of the specular region. the lower cut-off in typical residential rooms is ~250-300hz; as such, you're porous absorber needs to be effective down to that range. since porous absorption is a velocity-based absorber, it needs to be sufficiently thick and/or spaced from rigid boundary such that the insulation is placed into areas of relatively high particle velocity for those lower (longer) wavelengths. you could also attenuate the indirect specular reflection by other means, such as redirection via a large (with respect to wavelength) flat reflective panel angled such that the reflection is redirected away from the listening position (eg, towards rear wall where it can be diffused and the energy returned to the listener as a laterally arriving diffuse-field).

carpet or any other thin porous absorber will merely attenuate the mid-HF specular band while the lower region is allowed to persist - which essentially colors/filters/eq's the reflection of which will still superpose at the listening position with the direct signal (albeit colored).

+1 Perfectly stated.

DD