Smoothing function in new REW version? - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 14 Old 06-21-09, 11:52 PM Thread Starter
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Smoothing function in new REW version?

so... in the minimal filtering/hard knee house curve thread there was talk about in a later version of REW there may be functionality to smooth the response curve rather than just the waterfall (use + and - gain on the automatic eq); is this possible yet?

EDIT: I have a Crown USM-810 (ok, actually 3 of them for various systems basically 128 filters in a box (over 8 channels but can do 64 on 2 channels)... I am looking to use RoomEQWizard to (hopefully) find the most effective filter frequencies, gains, and Q's automatically... Hopefully that gives you an idea of what I am trying to accomplish

Last edited by Chester; 06-21-09 at 11:58 PM.
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post #2 of 14 Old 06-22-09, 06:53 AM
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Re: On Minimal EQ, Target Levels, and a Hard-Knee House Curve (long)

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use + and - gain on the automatic eq); is this possible yet?
REW offers cut filters. If you want boost filters, you must enter them manually into REW, although the results may not match what REW will show as the corrected trace (for obvious reasons).

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post #3 of 14 Old 06-22-09, 09:55 AM Thread Starter
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Re: On Minimal EQ, Target Levels, and a Hard-Knee House Curve (long)

are there any programs *like* REW that provide this functionality? I have had little luck finding one...
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post #4 of 14 Old 06-22-09, 12:27 PM
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Re: On Minimal EQ, Target Levels, and a Hard-Knee House Curve (long)

I'm unsure what you're looking for exactly?

You want a program that recommends gain filters?

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post #5 of 14 Old 06-22-09, 12:44 PM Thread Starter
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Re: On Minimal EQ, Target Levels, and a Hard-Knee House Curve (long)

I am looking for a program that will analyze the measurement data find the 'line of best fit' (target response) and then 'design' filters that will best achieve the desired response. It would be even nicer if the amount of filters were programmable.

Ex. I tell the program I have 5 filters that I can place (between 20 and 20khz); I give it the measurement data (the frequency response data) and it finds the 'optimal' frequencies, Q's and gains to achieve the deisred response (basically whatever values bring things closest to 'flat' with the limited resources).

Something similar to what I am describing (that I have used before) is the RTA function on the DBX Driverack PA <http://www.dbxpro.com/PA/PA.php> however the Q's and frequencies are locked (so it only will change gains) I am looking for something that will 'preform' the RTA function but for a given number of parametric eq's rather than a 28 band eq
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post #6 of 14 Old 06-22-09, 12:58 PM
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Re: On Minimal EQ, Target Levels, and a Hard-Knee House Curve (long)

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I am looking for a program that will analyze the measurement data find the 'line of best fit' (target response) and then 'design' filters that will best achieve the desired response.
But that's exactly what REW already does. It only does so within the modal response bandwidth of a room, but I can't see what REW doesn't do that you feel is missing?

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post #7 of 14 Old 06-22-09, 01:00 PM Thread Starter
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Re: On Minimal EQ, Target Levels, and a Hard-Knee House Curve (long)

perhaps its just that I am not used to using only negative gains on my filters :/ I understand where you are coming from though... probably operator error here

EDIT/just thought: so basically, I would be best off setting the target response slightly above (+1 to3 db) the 'bottom' (lower) peaks so the higher stuff gets pulled down to it... correct me if I am wrong here.

The only thing I can think of as a plus to using positive and negative filters, it may be 'easier' to achieve a given response with adding and subtracting rather than just subtracting; if one needs to subtract a lot, will this not cause greater phase distortion than if one were adding and subtracting 'a little'?
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post #8 of 14 Old 06-22-09, 01:11 PM
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Re: On Minimal EQ, Target Levels, and a Hard-Knee House Curve (long)

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perhaps its just that I am not used to using only negative gains on my filters
There's usually little sense in using gain filters other than using them sometimes to shape a cut filter.

A gain filter is simply a waste of energy at the dip frequency. Dips are caused by phase cancellations, where the sound reaching the measurement point is a combination of an original direct soundwave and a reflected sound that is 180 degrees out of phase at the dip (one half wavelength).

When you add a gain filter at that dip frequency, not only does the direct sound increase by the number of dB of the filter, but unfortunately the 180 degree out of phase signal also applies an equal and opposite signal to counteract. The result is that your dip is still there and you have wasted the gain you've thrown at it.

Consider what creates a peak. The direct signal arriving at the measurement point is combining with a reflected signal that is in phase at the peak. When we apply a cut filter, not only does the direct signal drop, so does the reflected signal drop at the same time. The peak is easily reduced.

The best solution for dips is placement of the sub itself.

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post #9 of 14 Old 06-22-09, 01:32 PM
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Re: On Minimal EQ, Target Levels, and a Hard-Knee House Curve (long)

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Chester wrote: View Post
I am looking for a program that will analyze the measurement data find the 'line of best fit' (target response) and then 'design' filters that will best achieve the desired response. It would be even nicer if the amount of filters were programmable.
REW V5 will offer that, in addition to the more targeted modal EQ filters. Not until later in the summer though.
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post #10 of 14 Old 06-22-09, 01:35 PM Thread Starter
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Re: On Minimal EQ, Target Levels, and a Hard-Knee House Curve (long)

If I do a near field measurement wouldn't phase cancellation not be much of an issue?

edit (just saw JohnM's post): John: I would be more than glad to beta test for you Thank you for all of your work on this great program btw
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