Using REW to setup B&K PEQ and notch filter - Page 3 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #21 of 30 Old 10-06-09, 08:25 AM
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Re: Using REW to setup B&K PEQ and notch filter

If you do go the route of the SMS-1, I've found that room measurement and filter calculations are better handled by REW, then manually entered into the SMS-1. That way you can even do an average of several mesurement positions and use REW to average them. You also have extra memory slots for doing house curves etc.
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post #22 of 30 Old 10-09-09, 06:14 PM Thread Starter
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Re: Using REW to setup B&K PEQ and notch filter

My replacement woofer arrived this afternoon. I installed it and the new sub is working now

To remind folks of the setup here: I've got a small 8" Velodyne subwoofer located at the front of the room (I'll call this location 3). My new sub is an Outlaw LFM-1 EX and I'm testing it in two locations (I'll call these locations 1 and 2). Location 1 is on the left wall, about 8' from the front wall (red traces). Location 2 is on the left wall, about 5' from the front wall (green traces).

To increase the number of variables further, the outlaw sub has two user-selectable tunings: 25 Hz (Maximimum output mode - I'll just use "MO" for short) and 20Hz (Maximum extension mode - I'll just use "ME" for short).

All of the measurements are done with L+R fronts plus the subwoofer, using an 80Hz crossover.

Here is the trace for the little Velodyne sub at location 3:

Using REW to setup B&K PEQ and notch filter-velo-location3.jpg

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Here are the traces for the Outlaw sub with the MO tuning at the two locations described above:

Using REW to setup B&K PEQ and notch filter-ex-mo.jpg

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And here are the traces for the Outlaw sub with the ME tuning at the two locations described above:

Using REW to setup B&K PEQ and notch filter-ex-me.jpg

As expected from the measurements I posted several days ago for the little Velodyne sub at location 1, you can see that the new subwoofer has some big room cancellation going on from between 35 and 50Hz. My hope is to integrate the old sub (at location 3) to fill in this hole. So here we go....

Here are the traces for both subs playing simultaneously, with the Outlaw sub in MO tuning at locations 1 and 2:

Using REW to setup B&K PEQ and notch filter-both-mo.jpg

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And here are the traces for both subs playing simultaneously, with the Outlaw sub in ME tuning at locations 1 and 2:

Using REW to setup B&K PEQ and notch filter-both-me.jpg


I am feeling pretty lucky at this point! It seems obvious which setup I should use as the baseline for setting the B&K notch filter (both subs on, Outlaw in location 1 with ME tuning - the last graph in this post). And the even better news is that location 1 has the most WAF.

Last edited by Jarrod; 10-10-09 at 02:20 AM.
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post #23 of 30 Old 10-09-09, 08:52 PM Thread Starter
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Re: Using REW to setup B&K PEQ and notch filter

This will give you a feel for what the Ref50 pre/pro gives you to work with. It has a notch filter which can be set in 2Hz increments from 20Hz up, with a variable "width" of up to +/- 17% of the frequency it is centered on. It also has a low-pass shelf filter, which lets you specify a frequency below which will be boosted by as much as 6db, or cut by as much as 18db. Here is what that looks like using 30Hz as the cutoff frequency (the red graph is no shelf applied).

Using REW to setup B&K PEQ and notch filter-shelf30.jpg

So what I'm thinking I want to try to do is boost the frequencies below ~50 Hz and apply the notch to tame the peak at 60Hz.
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post #24 of 30 Old 10-09-09, 10:26 PM Thread Starter
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Re: Using REW to setup B&K PEQ and notch filter

Botched attachment - see next post
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post #25 of 30 Old 10-09-09, 10:30 PM Thread Starter
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Re: Using REW to setup B&K PEQ and notch filter

With the sub crossovers defeated, I get the smoothest response with the notch filter set at -11dB centered on 62Hz with a width parameter of 51.7-72.3Hz (the max width for the notch), and the low-pass shelf set for +3dB below 70Hz.

Using REW to setup B&K PEQ and notch filter-eq1.jpg

The sweep sounds pretty smooth with the EQ set like this. I can hear the peak at 25-30Hz, but it isn't that bad and everywhere else sounds great to my ear. I'll play some music and movies for awhile and see what I think.

I do not know what the drop out at 111Hz is about - this appears any time I engage the notch filter, and seems to be independent of the location or amount of correction applied. Strange, but it doesn't seem to be audible.

Last edited by Jarrod; 10-10-09 at 01:23 AM.
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post #26 of 30 Old 10-10-09, 03:24 PM Thread Starter
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Re: Using REW to setup B&K PEQ and notch filter

I watched Transformers this morning and decided I wanted more infrasonics. So I spent several hours tweaking the shelf, notch and crossover filters, as well as the relative gain on the two subs to achieve that, as well as an even smoother response. New settings are +6dB below 40Hz for the shelf, -9dB at 62Hz for the notch, and a crossover of 60Hz.

Here is the response with the mains playing:
Using REW to setup B&K PEQ and notch filter-eq2.jpg

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And here it is for subs only:
Using REW to setup B&K PEQ and notch filter-eq2-subsonly.jpg
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post #27 of 30 Old 10-10-09, 05:21 PM
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Re: Using REW to setup B&K PEQ and notch filter

Quote:
Jarrod wrote: View Post
I do not know what the drop out at 111Hz is about - this appears any time I engage the notch filter, and seems to be independent of the location or amount of correction applied. Strange, but it doesn't seem to be audible.
Maybe a phase interaction between the filter and your crossover? If there is a phase or distance adjustment on your crossover, that might help. Fortunately, deep and narrow notches like that are often inaudible...

Regards,
Wayne




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post #28 of 30 Old 10-11-09, 05:45 AM
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Re: Using REW to setup B&K PEQ and notch filter

What are you doing to time align everything.
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post #29 of 30 Old 10-11-09, 11:12 AM Thread Starter
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Re: Using REW to setup B&K PEQ and notch filter

Quote:
What are you doing to time align everything.
Other than making sure that speaker distances are accurate in my processor (impossible for two subs), I haven't even considered it at this point.

What should I be doing? Here is a waterfall plot of the setup as it sits currently:

Using REW to setup B&K PEQ and notch filter-eq2-waterfall.jpg
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post #30 of 30 Old 10-11-09, 12:05 PM Thread Starter
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Re: Using REW to setup B&K PEQ and notch filter

Quote:
Wayne A. Pflughaupt wrote: View Post

Maybe a phase interaction between the filter and your crossover? If there is a phase or distance adjustment on your crossover, that might help. Fortunately, deep and narrow notches like that are often inaudible...
I don't know, Wayne. My processor has no such adjustment and this goes beyond my basic, qualitative understanding of how a crossover works.

The more plots I do, the more I think this dip at around 100Hz be a real cancellation effect. I'm not sure why it seemed to be correlated with the notch filter when I first noticed it (doesn't seem to be now), but if it indeed is related to the filter then whatever detrimental effect this may represent is more than offset by the benefit I'm getting from engaging the filter.
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