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Discussion Starter #1
Hello John,
I am using the "Find Resonances" in "Modal Analysis" to identify my room measured resonances.
I use the resonance selection to view the resonances on the chart.
I want to find the accurate bandwidth (or Q) of each resonance.
Can I do it by drawing a -3db lines on the specific resonance and identify the Bandwidth accurately?
Is there a better method to get the bandwidth (or Q) of each resonance?
Please advice,
Please see picture below:
 

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A figure for Q can be worked out from the modal decay times, though it is a little complicated and depends on gain and frequency. It is easier to use the decay times directly using REW's modal filter type: "Filters which accurately counter specific resonances can be generated by selecting the "Modal" filter type and setting the Target T60 value to the T60 time determined by REW. Modal filters are normal parametric EQ filters whose Q or bandwidth is adjusted by REW as their gain is changed to ensure they target the specified T60 value as closely as the equaliser settings resolution permits." (from the help). If you put the T60 values into a modal filter you can read the equivalent filter Q values for any particular gain setting from the filter panel.
 

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Discussion Starter #3
Hello John,
Hello everyone who is using DEQ2496

Many thanks for your fast replay.

I selected the "Model" filters to find resonances Q and in my case most of them came as narrow notch filters of about 10 for DCX2496.
I am using DEQ2496. DCX2496 Q of 10 equal to Q of 1/10 with DEQ2496.
DEQ2496 has both 31 1/3 octave graphic equalizer and 10 parametric equalizer with narrow q up to 1/10 octave.

I understood from the "Model Analysis" 'help' thet most accurate way to find the room resonance frequencies is to run the analysis at 500ms +/- ~20ms length and choose only the repeating frequencies.

I am using floor standing full range speakers that goes down to 27Hz in bass.
My listening room is ~(WLH)3.3*3.3*2.4 meter.

I want to suppress 20-400hz room resonances using the DEQ parametric narrow filters and balance the overall curve to target and ears listening using the 31 1/3 octave graphic equalization.

I am planing to do it in the following way, please tell me what you think about it:

1. Perform 4 longest measurements of 1M length (20-100Hz, 100-200Hz, 200-300hz, 300-400hz) to identify accurately my measured resonances and compar it also to room simulation analysis.

2. Use "model analysis" to find room modes by running each measurement with analysts length of 500ms, 520ms, and 480ms analysis length.

3. Select the repeating resonance frequencies that has long T60 time and high gain to be suppressed using
DEQ2496 10 narrow Q parametric filters and set it in the DEQ2496 parametric equalizer.

4. Perform 20-20kHz full range measurement and adjust the 31 Graphic equalizer for smooth target curve
with ~6db/oct roll-off from ~1khz.

5. Perform final Graphic Equalizer twink using periodic "pink noise" and listening to quality music material.

Please tell me what you think about this plan,

Many thanks,
Bertadora
 

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REW Author
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I would just make one 20 - 400 Hz measurement. Modal EQ is typically best applied below 100 Hz unless your room is very, very large. Make a measurement after setting your filters to see how well they have worked, and if I were you I'd make some loopback measurements of a few filter settings with the DEQ2496 to see how the shapes compare to any of REW's existing EQ settings, if there is an REW setting that matches you can watch how the filter adjustments affect the waterfall for the prediced EQ result and try some manual twekas ot the values to see what works best. The comment about DCX Q=10 corresponding to DEQ 1/10 sounds unlikely, you should check that.
 

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Discussion Starter #5
Hello John,
many thanks for your reply.
I checked again the about DCX2496 Q=10 corresponding to DEQ2496 1/10 of its parametric equalizer for notch filter and I think this is correct.
Please see below from their user manuals:

Regards,
Bertadora
 

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REW Author
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That just tells you what range each equaliser has, it doesn't mean Q=10 is 1/10 octave or Q=0.1 is 10 octaves. The actual relationship will depend on the Q definitions each equaliser uses. As an example, 1 octave on an FBQ2496 is the same as Q = 2 on a DCX2496 or the same as 0.5 octaves (30/60) on a DSP1124P. For the DSP1124P the bandwidth figure is the reciprocal of the DCX Q figure, but for the FBQ the the bandwidth is twice the reciprocal. I don't know if the DEQ behaves like the FBQ or the DSP.
 

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I would just make one 20 - 400 Hz measurement. Modal EQ is typically best applied below 100 Hz unless your room is very, very large. Make a measurement after setting your filters to see how well they have worked, and if I were you I'd make some loopback measurements of a few filter settings with the DEQ2496 to see how the shapes compare to any of REW's existing EQ settings, if there is an REW setting that matches you can watch how the filter adjustments affect the waterfall for the prediced EQ result and try some manual twekas ot the values to see what works best. The comment about DCX Q=10 corresponding to DEQ 1/10 sounds unlikely, you should check that.

that's for sure the quickest way to balance the low's and mid lows using the modal filter. Otherwise you have a nice frequency response but the decay is out of balance.

one more thing, the good thing about deq2496 is the digital in and out.

JohnM, i would appreciate if you could point in your opinion whats the best audio quality money wise option to process a system macbook pro > Maudio fast track 400 > analog active monitors?
FBQ2480 or DEQ2480 or?

Thanks in advance.

My actual setup is Jriver, dmg equick plugin to make the response flat, and then parametric filter to shape the house curve in jriver.
from 50hz +1.8 db to 120 at 0 dbs - from > +/-600hz each octave -.1 db the last octave -.2dbs.
 

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Sorry Claudio, in most cases my knowledge of the equalisers is limited to their bandwidth definitions and parameter ranges, not their audio quality. I have used several miniDSP products though, which have all worked well and are very well priced for the functionality they offer.
 

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Sorry Claudio, in most cases my knowledge of the equalisers is limited to their bandwidth definitions and parameter ranges, not their audio quality. I have used several miniDSP products though, which have all worked well and are very well priced for the functionality they offer.
Doble Thanks Mr. JohnM for your knowledge and all the effort put in the rew room eq wizard. It's a bomb!

Cheers from Portugal.
:T
 
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