# Can REW be used to EQ Center channel?



## MadFloyd (Apr 18, 2011)

I have an EQ problem with my center channel and have been trying to figure out a way I can get a test tone (e.g. pink noise) through it so I can measure how it's doing and then EQ it with my processor's built in EQ (I have a Classe SSP-800). I normally use RTA for my stereo but was hoping that REW could be used for the center.

Any help/advice appreciated!

Thanks!


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## Ile (Nov 23, 2010)

Use processor's 5.1/7.1 analog inputs when measuring, then you can connect left/right channel to where it's needed.


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

Welcome to the Forum Floyd!

You can use the 5.1 inputs like Ile suggested, or switch the receiver to Dolby Pro Logic and unplug the other speakers. That’s just for getting a signal to play from the speaker, however. Measurement is a bit trickier. For accurate full-range measurements you’ll need a calibrated mic and a mic pre-amp w/ phantom power. The latter can be a USB interface such as the Tascam US122 (or similar), or a separate unit like the Behringer ZENYX 502 that can be connected to a regular sound card.

Regards,
Wayne


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## MadFloyd (Apr 18, 2011)

Thanks for the replies.

I'll go with the method Ile suggested - I didn't think of that. I can just use RTA that way (which I already have installed with calibrated mic etc).


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## paulspencer (May 11, 2007)

What kind of EQ are you planning to use? If you take a listening position ungated measurement of a fullrange speaker, then EQ it to try to get it flat based on that, you can end up with a mess! There are some things that should be corrected, and some that shouldn't. You can tame the room below about 300 Hz with such a measurement, and you can do a little voicing full range if you use a 1m gated measurement. But it's probably not a good idea to try to do both at once. Each needs a different measurement technique, and even different software. I don't know if that's what you are planning or not.


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## MadFloyd (Apr 18, 2011)

paulspencer said:


> What kind of EQ are you planning to use? If you take a listening position ungated measurement of a fullrange speaker, then EQ it to try to get it flat based on that, you can end up with a mess! There are some things that should be corrected, and some that shouldn't. You can tame the room below about 300 Hz with such a measurement, and you can do a little voicing full range if you use a 1m gated measurement. But it's probably not a good idea to try to do both at once. Each needs a different measurement technique, and even different software. I don't know if that's what you are planning or not.


Good questions, Paul.

I use RTA which can output pink noise and measures the room response real time. I use this method to flatten bass for my 2 channel setup (which employs a Rives PARC bass EQ). I also use it to help voice my 2 channel system (I can see dips or peaks at various frequencies as I reposition the speakers). My intention was to get the bass somewhat flat on my center channel because the intelligibility of it is currently lacking (i.e. dialog in movies is a little muffled sounding). I was hoping that I wouldn't have to EQ any of the mid or high frequencies - just tame the bass, but seeing the EQ graph would also tell me if something was amiss above 300hz.

Does all of this make sense to you or do you think I should be doing something differently?

Thanks in advance.


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## paulspencer (May 11, 2007)

I've used a method like that in the past, but it's far from ideal. To do it right requires good measurements to start with. At the very least you need two measurements and they need to be done differently. Below 300 Hz or so (the Shroeder frequency transition point), you want a farfield ungated measurement taken at the listening position. REW is ideal for that. You are dealing with boundary interference and modes in this region, and this is where it is appropriate to adjust room effects with EQ. Above 300 Hz, you should only touch the direct field, which is what you would measure in an anechoic chamber. What you are doing here with pink noise is mixing the direct and reverberant fields, it's like trying to drive in the fog. You need to use a program like Holm Impulse, Arta of Fuzz measure for this - they will all gate out room reflections so that you can see through the fog and only deal with direct speaker response, not the room. A full range far field measurement might have it's uses, but it's certainly not a measurement to use for working out how to do EQ.


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