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Test gear for room nodes - parametric equalizers

I have recently taken a serious interest in understanding room acoustics and nodes. I have read some great, easily understandable material from www.harman.com, and some from frequent Audiogon poster Rives at rivesaudio.com. I have come to believe that my system has a great deal of untapped potential that may be masked by room nodes, and that use of bass traps, etc, are not answer. The skinny I am getting is that we could all benefit from high resolution room acoustic measurements and the judicious use of parametric eq's to cut the nodes down to size. FYI - my room is rectangular 17 feet by 19 feet, with 9 foot ceilings. Three questions:

1. Does anyone know of a reasonably priced, high resolution room measurement system? Rives Audio sells a system for $600.00, but is that the low end? Can you rent this stuff? After all, you probably only need it for a short while.

2. In a multi-channel system, how few channels of eq can you get away with to tame room modes? I would think perhaps three would work for stereo music(one for subwoofer and two for the main channels since they produce the most bass), or do you really need the center and surrounds eq'd?

3. What about reasonably priced eq's that won't defile a good system? Some high end parametrics run $4000-$5000.00. On the other hand, one well recognized pro-gear manufacturer, Ashly, makes some where you could get 3 channels for about $900.00. Would they be a mistake, introducing noise or something? Meyers Sound makes one for a bit more. Above that, it gets pretty crazy, at least for my budget.
jswarncke
4 responses Add your response
wrcraw38b6
1 posts
 
ETF is a great tool for room and loudspeaker measurements. It is best to use a calibrated microphone. ETF sells a good one. It comes with calibration data for the individual mic. on a floppy. This is read in and can be used by the measurement program.
ETF constucts the impulse response of the room from the measurement and from that it generates a wide range of displays of the processed measurement data which includes a 3D presentation of the modes in the room.
Demo is available for free.
I am a happy user and have no connections with ETF.

Ordinary equalisers will not correct room resonances. Save your money.

Bill
kgveteran
377 posts
 
I own an ashly parametric model SC-66.It's probable twenty five years old.This thing sold on ebay for 75.00.It is a dual ch. four band.Which means you have two sub bands per ch.You can use it as a notch filter but,never boost.Only cut.If you have a dip in freq. in your room you must try everthing first(moving it all over the room).Until the response is as smooth as you can.Then you cut the bumps(room modes out).Boosting bass freq. in an area in which there is a black hole will over drive your sub driver and ruin the amp or the driver it's self.If you understand the parametric you can widen or narrow the cut,adjust the freq. , and reduce the gain by about 15db.A true notch filter will reduce by 30db.15db is usually enough.Most rooms have two modes in their sub range 20hz-80hz.You could get by with a mono but what the heck the other ch. is alway availible.Eq's on all the ch. will also help.Most modern eq's are quiet and add and subtract what they are suppose to.Ashly is made in my home town and I swear by them.Call the tech guys and they will set you strait.There will always be a fierce difference in opinion when it comes to eq's.Both camps have good points and valid ones.What you must ask youself is what works for you.Careful eq's on all ch. will smooth out room modes along with room treatments.Bass absorbers(pressure absorbers).High freq. absorbers(velocity absorbers) are a must.The room must be "treated " well first to avoid over eqing.Wish you well.
p_ullman
1 posts
 
Behringer makes a two channel tube based parametric equalizer which is available for about $150. I do not know how good it is.
onhwy61's avatar
onhwy61
5,137 posts
 
Parametric EQ is not a cure all. To fully address room mode induced bass problems you will need a combination of approaches. Careful speaker/listener placement and bass traps are an essential first step. You also have to realize that traditional EQs will not correct for time related distortions. You might want to consider the TACT TCS -

http://www.tactaudio.com/TCS/index.html

The TACT is not perfect, but it does correct for time based distortions and it is also an excellent measurement system.

An excellent stand alone measurement device is:

http://www.terrasonde.com/default.htm
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