Room treatment for a rented house?

[chrisgeary]

I have been using twin subs in my room for some time now, a REL Strata III and REL Quake. I used the quake to control resonance and even out the room. I have sold the Strata and now have an SVS 20-39PC+ tuned to 12hz. I also have a BFD.

It seems to me that trying to use a rear sub is more effort than its worth. I have attached a response chart (because I couldn't see how to insert the image)

All speakers set to small, xover @ 80hz, sine waves generated by processor, output to sub and mains only.

The orange line is the dry room response. Blue is the BFD'd version. Green is the BFD'd version plus the Quake at the back.

As you can see, the BFD does a nice job of taming my rooms 33hz peak, and the corresponding hump at 63hz. However, there is a huge dip at 125hz. I attempted to use the Quake to fill that area in, and sort of succeeded, but it shifted the dip up to 142hz. Anyway, it struck me that these are the kinds of frequencies that can be damped with Auralex? I know nothing about this stuff, so my question is:

Given that the Quake is not adding much value anymore, I think I should sell it and replace it with room treatment. However, I live in a rented house, so permanent fixture is out of the question. Is there anything I can do/use?

Room is about 6m x 4m or thereabouts. Any advice, gratefully received

[Ian J]

Custom Audio Designs are the experts in this field so have a look at their website here as there is a wealth of information on most types of acoustic problems

[Thunder]

Hi Chris, I have a dip at 55hz and was told by Ian from Tag when he EQ'd my room that he thought it was the resonant frequency of my plasterboard wall but he wasnt too concerned about it.

[Nimby]

Your curves aren't that bad Chris.

I don't think you can easily treat a room for a trough. It's interesting that you are getting a doubling effect @ ~30, ~60 & ~120 Hz. Seems like a harmonic of the 32Hz room fundamental.

Have you tried moving the SVS about (even just for testing) and forgetting the Quake? I can't help feeling that the Quake isn't up to the standard of the SVS. I wouldn't want to lose the effortless purity of an SVS. Ask yourself what you would do if the Quake wasn't available.

BTW Why have you tuned the 20-39+ to 12Hz? Would you care to share your thinking here? It may be possible, but why have done it?

Nimby

[chrisgeary]

aww Nimby.. shucks.. you little you flatter me

yep, they are definitely harmonics of the fundamental.

you are right about the Quake, it sounds wrong now, a different calibre altogether, so I have disconnected it.

i wondered about treating troughs though, is it not the same principle as a peak? a standing wave is created and either manifests itself as a peak or as a trough. thus if there was some absorption in the room, the reflected wave would have less of a chance to build - surely this would reduce peaks, and also reduce troughs since its the reflected wave that causes both eventualities?

moving the SVS, yes, I found it better front left of the room, previously the strata was front right. in all honesty, the frequencies i have most trouble with now are those above 125hz, which the SVS is not really doing much about.

as for 12hz tuning.. well why not! in my room, i don't need outright power as its not that large. to hear the thing moving air at helicopter like frequencies is, quite frankly, awesome! it doesnt even chuff with one port open. I have set the subsonic filter to 16hz though as it starts to really chuff at 10hz. but set to 16hz, it does not have a detrimental effect on output between that and 12hz. for movies like Master and Commander, when those canons go off, that extra depth is absolutely amazing. having said all that, i have been wondering about tuning it to 16hz instead, but i just love that depth!

[Nimby]

Do you have any large windows, doors or cupboards that vibrate at certain frequencies?

This might account for a trough if it's not a room dimension cancellation effect. If you do have a suspect surface you could do a slow frequency sweep while standing near the suspect to see if it's the problem.

I vividly remember a B&W subwoofer shop demo in a busy high street. The way the huge shop window was vibrating really made me fear for the lives of passers-by!

Moving the sub about should help with room size problems. But not with absorbing panels (of whatever type). Doors, windows, flimsy partitions, cupboards, etc.

Lots more fun to be had yet. Keep us informed of progress.

Nimby

[chrisgeary]

i have two windows, single glazed
the rear window vibrates alarmingly at 18hz and again a bit higher up too. the left window doesnt seem to vibrate at all. nothing else seems to vibrate particularly (superglue is a wonderful thing) .... im kidding
since you mention it, something in the sub itself rattles at 40hz. i've tightened some of the screws on the back which seems to have helped. i noticed it, though, when i knocked the cabinet with my knuckles, in the way you do when testing something new for strength. you know what i mean. anyway, when i did that, it rattled. not when i move it like something is really lose, but only when i kinda thump it on the side of the enclosure.

so, in short, do you guys reckon i am stuck with the upper bass dip?

[avanzato]

Originally Posted by chrisgeary

i wondered about treating troughs though, is it not the same principle as a peak? a standing wave is created and either manifests itself as a peak or as a trough. thus if there was some absorption in the room, the reflected wave would have less of a chance to build - surely this would reduce peaks, and also reduce troughs since its the reflected wave that causes both eventualities?

You are right Bass Traps tuned to the correct frequency will improve peaks and troughs. IME you hear the difference with the peaks due to reduced reveberation times easier than any change in the troughs.

'The Rattle' Can you not shine a torch inside the SVS to see if anything is obviously out of place.

[rOAdeh]

dont be afraid to open up the svs - it really is v simple...

iirc 4 screws holding in the base plate followed by 8 holding in the driver itself and then you get access inside the sub itself... literally a 10 min job to dismantle and do up again if your a dab hand with a screwdriver

[Nimby]

Chris

Before you hone your skills with a screwdriver why don't you e-mail Tom for advice about this rattle?

Can't do any harm and will save you opening up the beast unnecessarily. They usually answer so quickly that you won't have lost any time. They are the real experts on their products after all and might just point to the problem somewhere else than the driver.

I did the "chrisgeary Nuckle Test" and my PCi sounds dead. Until I turn it on!

Nimby

[Smurfin]

If the crossover is set to 80hz, how can the Quake be filling in with that 125hz problem? Unless I'm reading it wrong, it would seem you're EQ'ing your mains at this point rather than the subs...

[chrisgeary]

yep, think i will send an email over to Tom before DIYing it. its not an audible problem in operation, more an observation after performing the "knuckle test". hopefully tom will be able to advise me.

matt: yeah i cheated a bit with that, i wazzed the gain right up on the quake so it would output something at 125hz, then consequently used several filters to knock out the lower frequencies. of course below 20hz comes out unfiltered through the BFD so thats where the plan failed.

[chrisgeary]

Nimby: I have just run the frequencies with the SVS tuned to 16hz.. here is the graph:
Orange: Dry
Green: BFD'd (12hz)
Blue: BFD'd (16hz)

No BFD settings were changed.

[Nimby]

Hang on I'll fetch my microscope to see the graph!

Nimby

[Nimby]

Okay, I found my microsope but the image was a bit fuzzy.

There isn't much difference between the two tunings, is there?


Nimby