# Applying filters within filters



## marty1 (Jun 29, 2010)

Okay Sit tweakalot is at it again :R

I'm trying to bring the low end down to 10hz up using bfd, as seen in another thread I applied a big wide boost at 20hz and a big wide cut at 30hz. Through further tests I've found I didn't even need the boost at 20hz, the big cut at 30hz brings it down to near enough the same level, something I believe Wayne was advising me on.

Next problem is although I have a wide cut at 30hz to bring that huge wide peak I used to have down there is a lot of ringing at 30hz still there, I can't add anymore cutting to that particular filter as I found it sucks the bass energy out completely if I apply too bigger cuts, -6db will be the maximum I will use. What I have tried and seemed to work when I looked at the waterfall, was applying another narrow filter at 30hz, this has reduced the ringing.

What I'm interested to know is is it a bad thing or detremental to the sound in any other ways by applying a filter within a filter?

The first measurement is without the narrow cut at 30hz, the second is with it applied.


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## Wayne A. Pflughaupt (Apr 13, 2006)

marty1 said:


> What I'm interested to know is is it a bad thing or detremental to the sound in any other ways by applying a filter within a filter?


We can’t hear it, so you’ll have to tell us yourself: Which way sounds better?

The “ringing” in the first graph, I have my doubts that it’s ringing at all. Anytime you see something “protruding” out of the waterfall like that, that shows no indication of decay - that’s some kind of steady-state noise. Typically we find it’s something in the room, like an air conditioning unit or refrigerator. However, the fact that you were able to equalize it away tells me it’s coming from your system.

To make the determination, you might try using the RTA feature, with no signal source playing.

Regards, 
Wayne


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## marty1 (Jun 29, 2010)

Wayne A. Pflughaupt said:


> We can’t hear it, so you’ll have to tell us yourself: Which way sounds better?
> 
> The “ringing” in the first graph, I have my doubts that it’s ringing at all. Anytime you see something “protruding” out of the waterfall like that, that shows no indication of decay - that’s some kind of steady-state noise. Typically we find it’s something in the room, like an air conditioning unit or refrigerator. However, the fact that you were able to equalize it away tells me it’s coming from your system.
> 
> ...


I will have to try and find a movie scene where 30hz is quite prominent in order to figure out if it is having a negative effect if I'm to find out which sounds better, unless you have any suggestions?

I've been reading about RTA and it looks kind of tricky but then I found reading about rew quite daunting to start with, it was only when I actually had a go at it that I got to understand it. Are there simple instructions for RTA?

Thanks Wayne.
Marty


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## Wayne A. Pflughaupt (Apr 13, 2006)

Just click the “RTA” tab and you should get a display. If you’re not generating a signal (like pink noise), the mic will simply be picking up noise in the room, and showing its frequency content on the graph. If it's not, clicking the red button should get things going.

Regards, 
Wayne


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## marty1 (Jun 29, 2010)

Okay thanks Wayne, sounds simple enough, even for me.


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