# Measuring software EQed response



## fitzwaddle (Aug 25, 2010)

I measured my speakers' frequency response using REW - found a couple peaks that I could address with parametric EQ. In this system (home office), the source is foobar2000, using Easy-Q VST plugin for EQ. I applied the EQ, works well. I'd like to remeasure with REW to see what the result is - is it possible to do so when the EQ is a VST plugin? Or is there an alternative software based parametric EQ that REW can work with (apply filters when sweeps are played)?


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## EarlK (Jan 1, 2010)

> The easiest method ( by far ) is to simply use REW's ( waveform ) generator to export a 1 minute long Pink PN file ( as a .wav ) that you then playback with ( & through ) the media player of your choice ( which also happens to "house"/host your VST based EQ filters ) . 
> You then use REW's RTA window ( to monitor the mic input ) to "look at" the consequences of the applied EQ .

:sn:


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## jdebonth (Aug 25, 2011)

Yes this would work but does not allow you to do detailed before/after comparison (stacked graphs) or allow the computation of decay waterfall plots to see how the EQ has improved this aspect.

Until something is realized within the software this is unfortunately the best work-around.

This feature is also requested and discussed in this post.


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## EarlK (Jan 1, 2010)

EarlK said:


> *WARNING :* Using *Any or All* of the following products ( IME ) is a great way to trigger BSOD(s) / more commonly known as "Blue Screens Of Death" .
> 
> -
> 
> ...


So, that said;

- One can always ( temporarily ) house your VST based EQ in a stand alone VST host ( such as  ) and then find a way to run REW into it and then out, over to your speakers . 

- You will also need  *ASIO4ALL*  ( to cobble together, a stable composite-driver ) and  *Virtual Audio Cable*  ( used within ASIO4ALL to create a virtual signal path into VSTHost from REW) . 

- Here are a few pics ( showing a "proof of concept" ) with REW sending its output into VSTHost ( through a vst based PEQ ) and then looped back into REWs input . 

- All the pertinent settings ( that worked for my gear ) are displayed .










































The second last pic shows the waveform obtained after sending REW's calibration signal through the VST based EQ and then back into REW ( in a cabled loopback ) . Now we all know that REWs soundcard cailbration file starts out flat , so the software based EQ must have worked ! .


:sn:




EarlK said:


> *WARNING :* Using *Any or All* of the above products ( IME ) is a great way to trigger BSOD(s) / more commonly known as "Blue Screens Of Death" .
> 
> So if you aren't in the habit of backing things up or are squeamish about reformatting a hard-drive , then tread carefully with this stuff .
> 
> *- YOU'VE BEEN WARNED !!! ( AGAIN )*


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## fitzwaddle (Aug 25, 2010)

Thanks Earl!! I am using ASIO4ALL on my desktop, will get that installed on my laptop (which I use to drive the system where I want to use PC based EQ). I am using Easy-Q parametric EQ, a VST plug-in, via foobar's VST host - so I'll try a standalone VST host. Read a little about Virtual Audio Cable, sounds like that might be the missing piece of the puzzle that I need - will see if there's an eval version I can try before I buy.


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## fitzwaddle (Aug 25, 2010)

Thanks again, got it working - as you stressed, only temporary - that girl saying "trial" every 10 seconds would drive me nuts! As well as the odd clicks and pops I'm getting, not sure why, but I didn't fiddle with too many options other than following your example. Was able to verify that both foobar and REW were passing output through the EQ - by setting up some really obvious ugly EQ settings, and (a) listening to output from foobar; and (b) measuring response in REW and noting the effects. Fun stuff! Pain in the rear to set it up though, so many fussy moving parts. But with short sweeps, I think I can get by with the trial version of VAC well enough to measure and set EQ for the speakers.


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## EarlK (Jan 1, 2010)

You're welcome ! I'm glad it worked for you .

Yes, there's no doubt this setup is a "lash-up" / kludge . A better solution would be if REW could host VSTs ( just before outputting it's signal ) .

This approach does work quite well when the "Yin & Yang" of all those mysterious soundcard/software settings ( buffers ) are balanced against each other.

I've streamed music originating from Windows Media Player through jRiver's MC17 ( since it has an open front end to ASIO inputs ), then through it's VST hosting engine & finally out through my soundcard over to my stereo . ( simply done as a "Proof of Concept" )

Once dialed in , I never heard a sputter, click or pop, even after an hour of continous . I think the reason ( mostly ) for this is because the 2 soundcard(s) are only being asked to output signal ( it's much easier, it seems to keep two freewheeling clocks synched when they are just outputting . I say soundcards because VAC is really a virtual software based soundcard . 

:sn:


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## fitzwaddle (Aug 25, 2010)

Tweaked some random settings and now the pops are gone - no idea which one did the trick! :rolleyesno:

I also tried setting the default sound output device to Virtual Cable 1, and tested it out, Spotify and Pandora play through the VST hosted software EQ via fine too. Pretty cool.


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## fitzwaddle (Aug 25, 2010)

Used the aforementioned configuration to measure response, set filters in REW, apply those filters to Easy-Q VST plugin, and remeasure the results - worked great, thanks again Earl.

before:










after (w/ house curve):










I didn't bother trying to boost the L below 80, will likely eventually add a sub and crossover there - difference probably caused by some room and LP/mic assymetry.


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## EarlK (Jan 1, 2010)

Thanks for the pics Brad , it's nice to see the configuration actually being implemented .

Good Stuff ! <> :sn:


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## fitzwaddle (Aug 25, 2010)

One last tip for posterity, in case someone else runs across this looking to get this configuration working. I was getting periodic dropouts - every minute or so - I changed the following Virtual Audio Cable settings to nail it down good, no more dropouts in the last hour of continuous music through Spotify:

- changed "Ms per int" from 7 to 20
- changed "Stream fmt" from "Cable range" to "Cable format"

(found clues to this from this Google result - about 1/3 of the way down the page: http://kc.flexradio.com/KnowledgebaseArticle50230.aspx)


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