# How do I analyze the effect of room correction?



## GrandeBoma (Feb 4, 2012)

I probably missed it from the tutorials, but after measuring and creating my filters for the room, how can I check the effect? Is there a way to remeasure the room with filtered sweeps?


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## SAC (Dec 3, 2009)

You simply generate a full range frequency response sweep in REW and display the waterfall from 10 Hz -~250 Hz.


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## GrandeBoma (Feb 4, 2012)

I do not get what you mean, sorry

I obtained my filters by mathematical calculations, and I can see the effect that they *theoretically* have on the sweep , how do I retrieve experimental evidence that they actually flattened the response? I saw a lot of comparisons before/after, how do I measure the after?


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## robbo266317 (Sep 22, 2008)

Do you have a pc and microphone suitable for use with REW? 
This is free software that lets you measure before and after graphs of your system.
Have a look here:- http://www.hometheatershack.com/roomeq/

Cheers,
Bill,


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## EarlK (Jan 1, 2010)

> I obtained my filters by mathematical calculations, and I can see the effect that they theoretically have on the sweep , how do I retrieve experimental evidence that they actually flattened the response? I saw a lot of comparisons before/after, how do I measure the after?


> The "theoretical" correction filters ( generated by REW ) must be applied/implemented within an external Equalizer .

> Once those filters are part of the signal chain / you retest your system ( with REW ) to check the effect of the applied filters .

:sn:


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## GrandeBoma (Feb 4, 2012)

but my eq is vst software based


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## EarlK (Jan 1, 2010)

> REW can export its recommended Correction EQ Filters as a Wave file for you to host within a Convolver ( which is in turn hosted within your VST Host ) .

> The trick is to then route REWs outputted test signal through the software acting as the VST host .

> Sometimes that is accomplishable by a clever patchup of VAC ( Virtual Audio Cable ) / though sometimes it's impossible .

> Generally the easiest way to test the effectiveness of REWs ( VST Filters ) is to export ( as a Wave file ) 5 minutes of Pink Noise PN ( using REWs Signal Generators export function ) . 
> Then play that custom Test Tone wave file, back through your hosting software, all the while monitorng the acoustic results using REWs' RTA window .

:sn:


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## GrandeBoma (Feb 4, 2012)

I tried exactly to route rew signal through VAC and it gave me a format error. I will post the error later on maybe you have a clue what the problem may be

thanks for helping you are kind


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## SAC (Dec 3, 2009)

Let me ask you a question...

How do you normally route an external source through your system so that the equalization is applied to the signal?

REW should be no different. The output of REW could be an external CD player, iPod, or tape deck or similar input to the receiver/system under test.

REW is simply functioning as an external source generating a test sweep that it i splayed through the system which it then receives via the microphone allowing it to measure the, in this case, frequency response of the test signal input.


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## GrandeBoma (Feb 4, 2012)

yes but it turns out that any source i use can channel audio through vac to my vst host except rew which gives me an error. I am here because of this error reported, other wise i would have solved the problem already


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## SAC (Dec 3, 2009)

Who supports the vst host???


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## GrandeBoma (Feb 4, 2012)

I use freeware "vst host"


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## EarlK (Jan 1, 2010)

> yes but it turns out that any source i use can channel audio through vac to my vst host except rew which gives me an error. I am here because of this error reported, other wise i would have solved the problem already


> I did some "Proof-of-Concept" explorations with VAC last spring / so you know, VAC is no longer on my computer because the interaction between it & my "flakey" M-Audio drivers resulting in too many BSODs for my comfort level . Something had to go ( & at least for the short term, it had to be VAC ) .

> That said, you need to treat VAC as simply another Audio Device choice within the Windows environment .
> IE: One chooses to use VAC like any other interconnect to an exisitng soundcard .
> For instance ; I found it a simple matter to connect REW with Audacity ( using VAC ) since both are setup to ask you where to you want to send audio to ( or receive audio from ) . Selecting VAC from the list of choice ( which is usually populated by only soundcards ) made the routing easy .

> As SAC noted, you still haven't "fessed-up" as to what software is currently hosting your convolverVST . If that software is not allowing you to connect to REW , then that could be your problem . Edit ; I see now that you are using vstHost .

> One can't patch two applications together ( using VAC ) if they both don't follow the SoundCard model ( of each one passing audio to or receiving from a typical "audio device" ) . _I do fear I'm not getting my point across ._
> As a for instance, "Media File Players" such as ( jRivers )Media Center , FooBar, WMP, typically aren't setup to support an open ( front-end ) architecture allowing one to stream audio content from a separate source application through the player application and then out to soundcard . ( Again, I don't know what application you are trying to interconnect with VAC so I guess we're at a stand-still ) . 

:sn:


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## GrandeBoma (Feb 4, 2012)

If that answers your question, once i succeed sending audio to VAC it gets processed by vsthost and output to the sound card. I can do this with any software, powerdvd to foobar including videogames, but REW (with java drivers) won't send audio to VAC. I am not sure if this is a known issue or have i screwed up something in the rew preferences


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## EarlK (Jan 1, 2010)

> Have you tried the Beta version of REW that supports ASIO drivers ?

> If not, follow the links at the top of the page to download the newer version .

:sn:

edit; here's the file 

 http://www.hometheatershack.com/fo...eta-asio-support-wizardinstallv5.01beta7.exe


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## GrandeBoma (Feb 4, 2012)

selecting ASIO I do not get the correct output mapping, I cant select which of the 5.1 channels to send from, instead I get spdif output left or right


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## EarlK (Jan 1, 2010)

> selecting ASIO I do not get the correct output mapping, I cant select which of the 5.1 channels to send from, instead I get spdif output left or right


> I'll assume you mean that you don't see the correct mapping from within REWs preferences page ( please be more precise in your language ) .

> Anyways, that's a bit weird .

> Try ASIO4ALL as your ASIO driver . It's auto-mapping functions ( of WDM drivers ) have never failed me .

>  *ASIO4ALL_2.10_English Version* 

> One possible limitation ( I see with using vstHost ) is that it only supports one audio device at a time ( as far as I can tell ) . 


:sn:


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## GrandeBoma (Feb 4, 2012)

these results are already with asio4all. my sound card asio driver can not be routed to vst hosts as this creates a feedback amplifying the signal like an infinite loop, so i can use these only to make the measurements, but not to see the results


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## EarlK (Jan 1, 2010)

> I think you need to rethink what you want to accomplish and prioritize your goals here .

> I've mentioned above that one can test the effectiveness of the filters ( one creates using REW ) by hosting those filters within a media player like Foobar or Media Center and playing back a 30 sec. Pink Noise PN wave file ( created by REW as an export ) . One simply monitors the results using REWs RTA window .

> The only successful full "soft-patch" system ( that I'm aware of ) allowing a user to run REW sweeps that were then convolved through hosted "Correction Filters" , employed an Emu soundcard that came with a fully-functioning version of "DirectWire" ( found within "PatchMix" , the driver software that comes with the bigger EMU soundcards ) .

> It's the flexibility of "DirectWire" that allowed that user to setup the necessary patching of the audio-streams .


:sn:


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## GrandeBoma (Feb 4, 2012)

I will play the file with foobar and measure the result

it is not true you need an emu soundcard to achieve that... vac + asio4all does it properly as far as i know


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## EarlK (Jan 1, 2010)

Here are a couple of older threads for you to read ( to gain some inspiration ) ;

(A)  *Using Convolver Universally* 

(B)  *"Digital Room Equalization"* 



> it is not true you need an emu soundcard to achieve that... vac + asio4all does it properly as far as i know


> VAC can easily connect 2 applications together ( as you say ) but that is not the hard part .
> The hard part ( without using DirectWire ) is finding a way to insert the convolver in between REW & the soundcards output .

:sn:


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