REW and DRC help - Page 2 - Home Theater Forum and Systems -

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post #11 of 16 Old 07-10-12, 08:17 PM
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Re: REW and DRC help

- My advice to you would be to simplify and only test a single pair of filters to first confirm that you can create a pair of working filters for use in MC17 ( using just DRCdesigner for everything ). MC17s convolver doesn't require a configuration file to work when it is loaded with ( pointed to ) a single stereo wave file .
- After you have success with a single pair of filters, then add one more complication to the process ( & so on, & so on ) till you have the whole enchilada working .

FWIW, I created a set of stereo filters with drcDesigner and have listened to them through ( 3 different convolvers ), all hosted within MC17 ( ie; ConvoBoy, ConvolverVST, & MC17s own convolver ) All three are slightly different in how they handle normalisation levels , btw . I also hosted 2 of those convolvers within VSThost ( a stand alone host program, used primarily for testing VST plugins )

Then I took a look at the shape of the filter types ( within REW ) by sending a test sweep through these convolvers and capturing the results back within REW ( done via some soft-patch routing through VAC ). I did this to educate myself on how manipulating the different control settings (within DRCdesigner filter settings ) change the resulting filter shapes .

Anyways, back to you;
IMO, as it stands right now, your test system has too many variables, meaning , you don't know where you've pooched the assembly process.

It could be any ( or all ) of the following ;

(1) A SoX conversion of your IR , from REW to DRC , caused by poor syntax of some sort.
(2) A poor Audicity conversion when splitting tracks and resaving .
(3) Or another type of syntax error within the creation of your convolvers "configuration file" ( for use with your multiple Wave files ) .
(4) A clock error or two ( ie; drift ) caused by using too many soundcards at the same time when trying to track your creations .
(5) Sample rate problems ( though MC17 is supposed to resample auto-magically, including data within its convolver ) .

Anyways; Simplify, Simplify, Simplify !

Last edited by EarlK; 07-11-12 at 05:41 AM.
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post #12 of 16 Old 07-10-12, 11:14 PM Thread Starter
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Re: REW and DRC help

The last picture is the sweep capture. The first two are the result of applying the generated filters to a second sweep test. As a test I grabbed one of the generated WAV filter files (the LR one), loaded it into Audacity and Select All/Generate silence, then tried that directly in the Convolution engine (without the config file) & it still produced similar results, which leads be to believe it may be a sample rate issue.

edit: I did see in this post that you recommend running Estimate IR Delay/Shift IR which is maybe where I have gone wrong.

Last edited by dean70; 07-11-12 at 12:37 AM.
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post #13 of 16 Old 07-11-12, 07:56 AM
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Re: REW and DRC help

Dean wrote:
edit: I did see in this post that you recommend running Estimate IR Delay/Shift IR which is maybe where I have gone wrong.
- That could explain the comb filtering ( if you didn't first "Zero Up" your REW export ) EDIT: SEE NEXT POST ! ( If your filters aren't at T=0 , it's not REWs fault ) and your filters aren't centered to T=0 .

- FWIW, I imported ( & then looked ) at the IRs of the stock EQ filters generated by "DRCdesigner" . I alsolooked at the REW generated EQ filters.
- Both types are centered to "T=0" .
- FYI, the REW filter is super clean ( being minimum phase ) while the DRCd generated filter has the expected "preringing" ( before T=0 ) that is expected from a linear phase FIR filter . Some people hear ( & find objectionable ) this preringing component that is endemic to this class of filter ( btw ) .

- You should import one of your filters into REW and take a look at its impulse ( I'm sure it'll be educational for you ) .

Last edited by EarlK; 07-11-12 at 08:49 AM.
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post #14 of 16 Old 07-11-12, 08:35 AM
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Re: REW and DRC help

me wrote:
- That could explain the comb filtering ( if you didn't first "Zero Up" your REW export ) and your filters aren't centered to T=0 .
Oops, spoke too soon .

- It looks like REW automatically "Zeros" (to T=0 ) every version of an IR that it exports.
- So an export from REW couldn't cause a filter offset in your case ( assuming you actually have a filter offset deviating from T=0 )

Last edited by EarlK; 07-11-12 at 08:58 AM.
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post #15 of 16 Old 07-11-12, 10:00 AM
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Re: REW and DRC help

Sorry to bother in this thread but could you please take a look at my post EarlK and share your thoughts? I ve spend quite a few hours on some new testing.
EDIT: this post can be deleted

Last edited by THX-UltraII; 07-12-12 at 02:21 AM.
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post #16 of 16 Old 07-11-12, 04:20 PM
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Re: REW and DRC help


In post #12 you loaded a file with all zeros as filter in convolution engine? If this is the case then you should get nothing but zero as output. If you use as a filter a file that has 999 zero value samples followed by one sample with a normalized value of 1, then you should get exactly out what you play, but with delay of 999 samples.

And yes, EarlK is right: simplify. Baby steps. For the moment stick with stereo, or even single speaker. You must confirm that convolution engine is behaving. If you have small speaker, even horrid little computer speaker, try measuring it from about 1ft, build correction with flat target and measure result.

You may get lucky, but don't count on microphone that came with receiver to be flat.

I do two way active speaker that is ruler flat (no smoothing), using convolution and multichannel sound card. It is based on Linkwitz Pluto, and thus my results are posted there:

Be thorough, methodical, patient, and persistent and "the convolution goodness" can be yours!

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