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post #1 of 7 Old 12-13-12, 06:59 PM Thread Starter
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Q Factor

Why are Q factors in EQs different from each manufacter?

I would think that e.g. Q 4.3, would be the same standard?

Thanks in advance
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post #2 of 7 Old 12-14-12, 02:00 PM
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Re: Q Factor

Q is the ratio of centre frequency to bandwidth, but there are differences in how bandwidth is defined. Sometimes it is measured at the half gain point (e.g. at -4dB on a -8dB filter - REW uses this for its Generic EQ setting), sometimes at the -3dB points (but then what is the bandwidth of a -2dB filter?). Robert Bristow-Johnson wrote a paper that addresses this, see http://www.musicdsp.org/files/EQ-Coefficients.pdf
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post #3 of 7 Old 12-15-12, 12:47 PM
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Re: Q Factor

Quote:
Phillips wrote: View Post
Why are Q factors in EQs different from each manufacter?

I would think that e.g. Q 4.3, would be the same standard?

Thanks in advance
You are undoubtedly talking about band peak- and dip-type filters. Then there are questions like what is the Q for a shelving filter, or a low-pass or high-pass filter, and how is the shape of the filter response affected by Q. Sometimes there are different filter implementations possible. As John stated, it is not always as simple as we would like it to be, and it is not necessarily just manufacturers being contrary, but actually having multiple variables to deal with.

Edit: here is a link to a handy Q/bandwidth conversion calculator.

Last edited by AudiocRaver; 12-15-12 at 12:59 PM. Reason: additional info
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post #4 of 7 Old 12-17-12, 04:39 AM Thread Starter
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Re: Q Factor

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JohnM wrote: View Post
Q is the ratio of centre frequency to bandwidth, but there are differences in how bandwidth is defined. Sometimes it is measured at the half gain point (e.g. at -4dB on a -8dB filter - REW uses this for its Generic EQ setting), sometimes at the -3dB points (but then what is the bandwidth of a -2dB filter?). Robert Bristow-Johnson wrote a paper that addresses this, see http://www.musicdsp.org/files/EQ-Coefficients.pdf

Thanks John i will have a read

What would be the advantage between the Omnimic vs UMIK?
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post #5 of 7 Old 12-17-12, 04:41 AM Thread Starter
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Re: Q Factor

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AudiocRaver wrote: View Post
You are undoubtedly talking about band peak- and dip-type filters. Then there are questions like what is the Q for a shelving filter, or a low-pass or high-pass filter, and how is the shape of the filter response affected by Q. Sometimes there are different filter implementations possible. As John stated, it is not always as simple as we would like it to be, and it is not necessarily just manufacturers being contrary, but actually having multiple variables to deal with.

Edit: here is a link to a handy Q/bandwidth conversion calculator.

Thank you i will download the calculator.
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post #6 of 7 Old 12-17-12, 03:20 PM
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Re: Q Factor

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What would be the advantage between the Omnimic vs UMIK?
Bit off-topic for this thread, but UMIK has SPL calibration data in the file so REW does not need SPL calibration when using UMIK. REW V5.01 beta 10 can also automatically recognise that UMIK is connected and configure itself correctly to use it for measurement.
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post #7 of 7 Old 12-17-12, 03:21 PM
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Re: Q Factor

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Thank you i will download the calculator.
Bear in mind it is only useful for equalisers which define filters by the bandwidth at the -3dB points.
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