Equalization using HTPCs ?

**rajdude** · **07-18-07, 11:08 AM**

I am trying to find some solution for equalization while using a HTPC.

Since a HTPC already is digital and all kinds of software / plugins are available.... I am wondering maybe there is some (graphic or parametric equalizer) software available which allows me to modify sound in the computer itself

This will do two things:

1. Eliminate the BFD from chain
2. Enable full range equalization, possibily for all 7.1 channels

If you can see where I am going....this will surely lead to improved sound quality.

The problem is to find a software based equalization solution. Is there anything out there?

The best option will be something which integrates a 7.1 channel parametric equalizer with REW. Now THAT will be REALLY sweet !

-Rajiv

PS: We will still need REW to see what we are doing!

**brucek** · **07-18-07, 11:44 AM**

Quote:

I am wondering maybe there is some (graphic or parametric equalizer) software available which allows me to modify sound in the computer itself

I'm not aware of any plug-in that allows that to be accomplished. But you're certainly not the first member to think of it....

brucek

**rajdude** · **07-18-07, 11:54 AM**

Actually there are at least a couple of plugins which I am aware of.

Look at fdshow and AC3Filter .
Both are directshow plugins (which MCE based HTPCs can use) and have graphic equalizers inside them. They sure are limited to a few, relative wide bands and the resolution is questionable.

Quote:

brucek wrote:

I'm not aware of any plug-in that allows that to be accomplished. But you're certainly not the first member to think of it....

brucek

**Alaric** · **07-18-07, 01:25 PM**

Hi There,

Have a read of http://www.duffroomcorrection.com/wiki/Main_Page

Its to do with Digital Room Corection and i think it is posible to use convolver as a direct show plugin - Its a slightly different method of equalisation techniques though as IIRC you create impulse response and the computer works out the filters rather than a more manual measure and tweak.

Cya,
Lee

**rajdude** · **07-18-07, 02:38 PM**

I dont understand what "convolving" means. I have tried to understand this thing earlier too.

From reading that page I understand it is able to do some sort of room equalization. I looked at the download pages.

Where are the controls?

Is there a page / manual which explains to a layman (or at least to a person who understands the usual tools used for equalization) what all this convolution and the process means ?

Quote:

Alaric wrote:

Hi There,

Have a read of http://www.duffroomcorrection.com/wiki/Main_Page

Its to do with Digital Room Corection and i think it is posible to use convolver as a direct show plugin - Its a slightly different method of equalisation techniques though as IIRC you create impulse response and the computer works out the filters rather than a more manual measure and tweak.

Cya,
Lee

**Alaric** · **07-19-07, 07:10 AM**

Hi There,

I *think* the concept is that you use something like Simple Automated IR Measuring Tool to create an Impulse response of your room - The basic send out a know signal and measure what comes back idea.

Then you analyse the results and calulate your filters via a pc, doing "A stereo 65536-tap filter" by hand could consiveably take a while ! - It seems you use DRC for this ?

The you use Convolver with Theatertek/Zoom Player / MPC etc

Simple eh !

I've yet to get round to actualy doing this....But its certainly something i want to play with. It also seems to be getting easier with time, ie the software and documentation is getting better....I remember having a look at this a year or two back !!!

Cya,
Lee

**JohnM** · **07-19-07, 09:20 AM**

REW measures the room's impulse response, that is how it produces the frequency response plots. You can export the impulse response REW measures for use with convolver and similar packages. You can also export the impulse responses of filter setups, which is probably more useful in this instance - i.e. you would use REW to make your measurements and set up the filters to correct the response, then export the impulse response of the filters to apply it with convolver (for example).

**rajdude** · **07-19-07, 11:08 AM**

Thanks for chiming in John!

For use with convolver, which Equalizer should I set in the Equalizer drop down menu?

Do I have to setup the filters manually or will REW do it automatically?

Quote:

JohnM wrote:

REW measures the room's impulse response, that is how it produces the frequency response plots. You can export the impulse response REW measures for use with convolver and similar packages. You can also export the impulse responses of filter setups, which is probably more useful in this instance - i.e. you would use REW to make your measurements and set up the filters to correct the response, then export the impulse response of the filters to apply it with convolver (for example).

**JohnM** · **07-19-07, 11:14 AM**

Use the Generic setting, it has the widest range of filter types and the best filter resolutions. You can automatically adjust the filters following the usual REW sequence.

**rajdude** · **07-23-07, 08:31 AM**

Oh my! I just spent a few days playing with DRC (http://www.duffroomcorrection.com/wiki/Main_Page) software.

This DRC software is insanely complicated! The manual is 150 pages long creating a filter file for use with the convolver is extremely complicated and involved.

I'd rather use hardware graphic equalizers.

Anyway, going back to REW....
Does REW will create a file which can be used straight in the convolver plugin....right?

John you said:

Quote:

You can automatically adjust the filters following the usual REW sequence.

Sorry but I am a newbie...what is the "usual REW sequence" ?
Is there a tutorial for this somewhere?

**rajdude** · **07-23-07, 08:37 AM**

Ok I found the helpfile at
http://www.hometheatershack.com/room...tml/index.html

sorry !

**rajdude** · **07-23-07, 08:50 AM**

Ok,
How do I assign filters for full range correction?

The find peaks works only upto 500 Hz.

Even there it keeps says "No peaks found"

**brucek** · **07-23-07, 09:33 AM**

Quote:

How do I assign filters for full range correction?
The find peaks works only upto 500 Hz.

You would enter filters manually into the EQ Filters panel where you can tweak the automatic filters suggested by REW and also you may enter values for full range. You also need to enter any filters with gain manually. Note that the results of the filters entered manually or automatically are dynamically reflected on the graph panel response.

Quote:

Even there it keeps says "No peaks found"

It will say that if it doesn't find any suitable peaks above the target line you have set.

brucek

**rajdude** · **07-23-07, 09:38 AM**

OK,
so I entered the filter parameters manually. But when I export out the filters as a WAV....and then use in in the colvolver DSP plugin in Windows Media player....the sound does not change at all.

What am I doing wrong?

Is there a helpfile for using REW with convolver ?

**brucek** · **07-23-07, 11:48 AM**

Quote:

Is there a helpfile for using REW with convolver ?

No, sorry. Maybe JohnM can help with this.......

brucek

**JohnM** · **07-23-07, 04:53 PM**

I haven't used convolver myself, but there's quite a bit of info on the author's website http://convolver.sourceforge.net/index.html. You can check the REW exported impulse responses by re-importing them and viewing them in REW. You can even play them directly in media player or similar, though generally there won't be anything usefully audible in them - if you made a file of a large number of 1kHz filters with 15dB gain and very high Q (50, say) then exported that impulse response and played it you would hear the ringing of the 1kHz tone in the impulse response, just for curiosity's sake.

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