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  Topic Review (Newest First)
02-13-09 10:37 AM
Anthony
Re: First up graphs, advice appreciated

It definitely improved your 200 Hz response. Still got that nasty resonance at 55 Hz or so. 1/4 Wave for that is about 5', full wave is 20'. You mentioned a 20' deep room. It looks like you may need some absorption to break up that standing wave.

To me, that resonance would sound more objectionable than the lower bass output.

But that being said, 8dB is pretty low for the bass. I would say, the speaker designer might have counted on some room gain to boost the bottom end, but if these are nearfield monitors, that wouldn't have been the case.
02-13-09 06:56 AM
dodittydada
Re: First up graphs, advice appreciated

Ok, with much hassle, been moving speakers around. Hows she looking now in your experience?
02-10-09 07:14 AM
JimP
Re: First up graphs, advice appreciated

I'm just saying that before you make yourself crazy fixing the room, be sure that you don't have something else going on with your electronics/sub/speakers. Unfortunately, if near field testing doesn't give you a flat response curve, then dragging it all outside to test it would be about the only other way to check it. How many feet of snow do you have?
02-10-09 03:53 AM
dodittydada
Re: First up graphs, advice appreciated

Quote:
JimP wrote: View Post
Have you calibrated your sound card and do you have any graphs of what the room was doing before adding any acoutic panels and bass traps.

I think another worthwild question is are we really sure that your amplifier speaker combination is not causing these dips?

unofrtunately, no testing before treatment. What possible things amp/speaker wise could cause a dip like this? At least then I know where to start investigating. thanks.
02-10-09 03:04 AM
JimP
Re: First up graphs, advice appreciated

Have you calibrated your sound card and do you have any graphs of what the room was doing before adding any acoutic panels and bass traps.

I think another worthwild question is are we really sure that your amplifier speaker combination is not causing these dips?
02-10-09 02:07 AM
dodittydada
Re: First up graphs, advice appreciated

Quote:
Anthony wrote: View Post
What are your exact room dimensions and relative speaker placement from wall/side/ceiling?

200 Hz 1/2 wavelength is about 5.5 ft. If you have an 11' dimension in the room and the speakers are right at this point, they'd be at a null.

Is there anything in the room that could be an accidental helmholtz or panel resonator? Sliding glass door, open doorway to another room. Dozens of empty water jugs in the corner? Originally my riser was acting as a panel resonator and sucking out a lot of bass until I added more insulation and doubled up on the plywood.

but that response is odd.

hmm, how about a fridge? Got one of those centre of the back wall. Could it possibly be sucking bass? with a closed door probably not. Width of the room MAY be around 11ft, not sure. Ill go measure it.
02-09-09 10:26 AM
JohnM
Re: First up graphs, advice appreciated

Try measuring forwards and backwards of your current position, 38% is not gospel, it is only a reasonable starting point to begin measuring to find the actual optimum for the room. Try moving the speakers also, as far as your space can accommodate. Easiest to use the RTA and the Pink PN generator when moving around, so you get immediate feedback of the effects.
02-09-09 08:40 AM
Anthony
Re: First up graphs, advice appreciated

What are your exact room dimensions and relative speaker placement from wall/side/ceiling?

200 Hz 1/2 wavelength is about 5.5 ft. If you have an 11' dimension in the room and the speakers are right at this point, they'd be at a null.

Is there anything in the room that could be an accidental helmholtz or panel resonator? Sliding glass door, open doorway to another room. Dozens of empty water jugs in the corner? Originally my riser was acting as a panel resonator and sucking out a lot of bass until I added more insulation and doubled up on the plywood.

but that response is odd.
02-09-09 06:40 AM
thewire
Re: First up graphs, advice appreciated

Quote:
dodittydada wrote: View Post
hmm, Im real suss on my chart. I mean, Im trapped to the * in here. Two front corner traps are a foot thick each, the ones behind the speakers 8 inches, rear traps are 6 inches thick....they are all 6ft tall and nearly reach to the ceiling. yet I still have a massive dip at 200hz in a rectangular room nearly 20ft deep??? I didnt expect flat of course, but this dosent seem right. I guess Im especially suss seeing its a dip and not a peak. Im sitting at the 38% point towards the front, I should be out of the way of any major modes.I just dont know what to do next besides start looking at slot resonators.
Have you tried some trapping on the ceiling between the LP and the mains before?
02-09-09 06:20 AM
dodittydada
Re: First up graphs, advice appreciated

hmm, Im real suss on my chart. I mean, Im trapped to the * in here. Two front corner traps are a foot thick each, the ones behind the speakers 8 inches, rear traps are 6 inches thick....they are all 6ft tall and nearly reach to the ceiling. yet I still have a massive dip at 200hz in a rectangular room nearly 20ft deep??? I didnt expect flat of course, but this dosent seem right. I guess Im especially suss seeing its a dip and not a peak. Im sitting at the 38% point towards the front, I should be out of the way of any major modes.I just dont know what to do next besides start looking at slot resonators.
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