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Author Topic: Convolution volume issues  (Read 2688 times)

natehansen66

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Convolution volume issues
« on: November 19, 2012, 08:46:25 pm »

Lately I've been trying to figure out how to use the convolver and .wav files for my active crossover. I can get the configuration file correct (AFAIK) so the channels are routed properly and the filter files are implemented correctly. However, I'm having some volume issues. I had my crossovers and eq done in the PEQ, and set the level for each driver at the amp (6 channel diy amp with attenuators on each set of inputs). After copying my eq settings to .wav files generated with REW, turning Convolution on and the PEQ off the levels are way off. I'm barely getting any sound with the volume in MC maxed. I need to turn the volume pots on my amp up past 12 o'clock, whereas when I use the PEQ to do the filtering I'm closer to 8 o'clock. I'm running horns here so there's no need for the excessive volume. Working on a new speaker today, I couldn't get the compression driver past 80db or so with my amp and the software maxed.

I keep the levels on my interface maxed, and set the levels at my amps to set the gain structure so I'm making use of most of the bit-depth of my interface. For whatever reason MC is doing some serious attenuation somewhere when I use the convolver.

Here's how my config file looks, is there anything wrong here?

48000 2 6 0
0 0
0 0 0 0 0 0
C:\Users\Nate\Desktop\Woofer EQ 11-19.wav
0
0.0
0.0
C:\Users\Nate\Desktop\Woofer EQ 11-19.wav
0
1.0
1.0
C:\Users\Nate\Desktop\Celestion EQ 11-19 3.wav
0
0.0
2.0
C:\Users\Nate\Desktop\Celestion EQ 11-19 3.wav
0
1.0
3.0
C:\Users\Nate\Desktop\4524 EQ 11-19.wav
0
0.0
4.0
C:\Users\Nate\Desktop\4524 EQ 11-19.wav
0
1.0
5.0


Typically these things come down to operator error, at least when I'm involved  ::) . What am I doing wrong here?
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mojave

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Re: Convolution volume issues
« Reply #1 on: November 20, 2012, 09:10:12 am »

What are you using to generate the convolution filters? I just started using Audiolense and it attenuates my filters by 25 dB. I'm trying to figure out ways to reduce that attenuation, but I think it is due in part to a mismatch in efficiency between my surrounds (105 db 1w/1m) and mains (90 dB 1w/1m).
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natehansen66

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Re: Re: Convolution volume issues
« Reply #2 on: November 20, 2012, 12:04:37 pm »

I'm using REW to generate the filters. There's a guy on DIYA that has free software for generating linear phase filters I may give that a shot and see if there's any difference.
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LesC

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Re: Convolution volume issues
« Reply #3 on: November 21, 2012, 06:42:07 am »

try restarting j river. either 17 or 18, i think there are quirks in their convolution engines. if you create a filter with audiolense and restart convolution in mc 17 to load the new filter without restarting j river, the volume gets screwed up.

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LesC

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Re: Convolution volume issues
« Reply #4 on: November 21, 2012, 06:59:46 am »

mojave, i have gone through that route and if you don't follow the natural roll off of your system you will have attenuation like what you're experiencing now.. add to that j river's issues with convolution you'll have little volume left.
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natehansen66

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Re: Re: Re: Convolution volume issues
« Reply #5 on: November 21, 2012, 07:29:39 am »

try restarting j river. either 17 or 18, i think there are quirks in their convolution engines. if you create a filter with audiolense and restart convolution in mc 17 to load the new filter without restarting j river, the volume gets screwed up.

Yeah, I tried killing MC as well as the media server with no luck.
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LesC

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Re: Convolution volume issues
« Reply #6 on: November 21, 2012, 07:43:13 am »

i haven't played with REW but if it works like audiolense does, you might have to try tuning your filter / target curve.
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natehansen66

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Re: Re: Convolution volume issues
« Reply #7 on: November 21, 2012, 11:58:35 am »

What do you mean by that.....the level of the FR I'm working with in REW?
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LesC

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Re: Re: Convolution volume issues
« Reply #8 on: November 21, 2012, 04:08:52 pm »

What do you mean by that.....the level of the FR I'm working with in REW?

that and the curve... in audiolense, if you make the target curve boost frequencies too much it would lower the overall volume by just as much. also the level at which your target curve is will influence the volume.
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natehansen66

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Re: Re: Convolution volume issues
« Reply #9 on: November 21, 2012, 05:14:16 pm »

that and the curve... in audiolense, if you make the target curve boost frequencies too much it would lower the overall volume by just as much.

Protecting us from ourselves.........


I think I said something in my OP about operator error  ::). In the config file I had the mid filter on the tweeter and the tweeter file on the mid. That changes things just a bit! The file swap, and turning off "Normalize filter volume" in the Convolver helps a lot. I still have to attenuate the mids -27 in the interface compared to my amp settings with the PEQ settings but this is totally usable now.

In REW the relative levels of the response from the tweeter and the mids I'm working with are the same so that shouldn't change things, though my mids should be a bit more sensitive than the tweeter. Certainly not +27 though.....
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LesC

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Re: Convolution volume issues
« Reply #10 on: November 22, 2012, 04:20:06 am »

since i got my feet wet with audiolense, i'm going to give REW a try. thanks nate !
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LesC

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Re: Convolution volume issues
« Reply #11 on: November 22, 2012, 04:54:45 am »

i've been playing with REW. it only does one measurement for the whole 5.1 system ?
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natehansen66

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Re: Convolution volume issues
« Reply #12 on: November 22, 2012, 09:33:46 am »

I've never used Audiolense, so I have no idea how it works. I think it can do linear phase filters, right?  REW is really just a measurement package. It can create basic IIR filters geared towards room correction, but it has no integrated functionality as far as setting up a multi-channel system. You would have to measure each speaker independently to come up with a filter set tailored to each speaker, but it won't set levels or distances for you. Levels could be set by overlaying measurements from each speaker after correction is applied. You could use it to figure the delays needed I think, but it would be much more work than a software package that would do that for you.

I use it mainly for the EQ section. It's pretty convenient because it allows you to see the effect of the filters on the fr you are working on. I use ARTA for the actual measurements though.
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