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-   -   Filter Types and Q (https://www.hometheatershack.com/forums/rew-forum/71891-filter-types-q.html)

jcmusic 12-22-13 10:14 PM

Filter Types and Q

When using the REW EQ feature it list different type filters e.g. PK,PA, BP and under Q it has a BW/60.
Can some one explain what these are/mean to me so I can understand?

Wayne A. Pflughaupt 12-23-13 03:48 PM

Re: Filter Types and Q

The filter types will be different depending on the specific equalizer chosen. A few common filter-type designations are:
PK – peak
LP – low pass
HP – high pass
LS – low shelving
HS – high shelving
BP – band pass

Since you mentioned BW/60, it appears you’ve selected the Behringer DSP1124 as the equalizer? With that one PA means “parametric;” not sure what “Modal” is an indication of. BW/60 is reference to the BFD’s bandwidth designation. Behringer defines bandwidth as a peculiar “xx/60” designation for this equalizer, with the “60” figure as an indicator for “one octave.” So, a filter assigned with a bandwidth of 60/60 would be a one-octave filter. A filter designated as 30/60 would be a half-octave filter, 20/60 would be 1/3-octave, 10/60 is 1/6-octave, etc. Conversely, 120/60 would be a two-octave filter, and so forth. Make sense?


jcmusic 12-23-13 04:55 PM

Re: Filter Types and Q

Hey Wayne,
Thanks for the reply yes it does make sense but, I can't figure out how to apply it as a Q number?
When I put in the parameters I get results like this: 108.8 hz, -5 db, BW/60 21
166.0 hz, -6 db, BW/60 6
186.0 hz, -6 db, BW/60 5
So on and so on???

Wayne A. Pflughaupt 12-23-13 05:31 PM

Re: Filter Types and Q

The BFD doesn’t designate filter bandwidth as Q, only xx/60, so no Q figure is needed. However, here’s a handy Q to bandwidth converter. Just keep in mind that that there is no universal standard for filter Q. It’s different from one equalizer to the next, as you can see in this post.


jcmusic 12-23-13 05:58 PM

Re: Filter Types and Q

Thanks Wayne I see what you mean. Ok got any tips on how to use the RTA? When I looked at it once I had a hard time trying to set anything

Edit: Wayne if you would have a look at my other thread (Advice and Opinions) just below this one page 2 the flat measurement from today, try applying some EQ to it and tell me which EQ you think works best.

Wayne A. Pflughaupt 12-23-13 08:01 PM

Re: Filter Types and Q

Not much to it, really. For starters, make sure you’re using PN pink noise see here for details and other RTA tips).

If you’re trying to take out a peak, for instance, first determine what the frequency center is. This is easy to do; just dial in a tight filter, say 1/6-octave, boost a few dB, then sweep the frequency knob. You’ll see a response peak caused by the equalizer to move across the graph. When it gets to the center of your peak in response, you’ve found the correct frequency center.

From there cut the gain as needed to reduce the peak, and adjust the bandwidth so that the filter does not extend beyond the width of your peak.

That’s about it. :T


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