# My first REW measure



## gnoto (Mar 21, 2013)

Below is my first measurement (red without Audyssey, purple with Audyssey Flat).
Welcome comments.

One question: the measure that I expose is on ​​the left channel. Is it possible to make a measurement with both the front channels?

thanks


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## AudiocRaver (Jun 6, 2012)

First of all, Welcome to Home Theater Shack! Glad you could join us.:bigsmile:

When measuring with sine sweeps, it is normally recommended that each channel be measured separately. When both channels are measured at once, slight variations in microphone positioning can result in phase cancellations at different frequencies, causing dips in the measurement curve and making its accuracy suspect. Both output channels cannot be activated withinn REW at the same time for this reason. Each channel can be measured separately and both curves displayed together on one chart.

It is possible to send the measurement signal to both channels at once using a "Y" cable or adapter of some sort, but be aware that the measurements taken will be of limited usefulness.


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## gnoto (Mar 21, 2013)

Thank you for answer.
Of course this does not apply in the measure of a channel and subwoofer (front or surround). Correct?


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## AudiocRaver (Jun 6, 2012)

You are absolutely correct, I should have mentioned it. While it can be useful to measure a speaker and sub combination separately to see how they each act around the speaker-sub crossover frequency without the other interfering, it is just as important, and as you suggest totally valid, to measure each speaker-sub combination together to see how well thy "mesh" and work together with crossover filtering applied.

The previously mentioned problem of phase cancellations measuring multiple speakers at once with sine waves becomes significant above 1 KHz (wavelength = 1 foot) or so where wavelengths are approaching the dimensions of

relative mic placement for repeated measurements
the human head and ear spacing (8 in)
the amount a listener might move around or be positioned differently at the listening position
For practical purposes, speakers are measured separately above subwoofer frequencies.

Going a step further, in a system with multiple subwoofers, the opposite rule applies. Since the wavelengths involved are in the range of tens of feet (11 feet at 100 Hz), it is convenient and accurate to measure with all subs running together at once.


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## jaypeecee (Mar 31, 2008)

Hi gnoto,

Looks like Audyssey is doing a good job over the majority of the audio spectrum. However, I do notice that it seems not to have done a great deal to smooth the peaks and troughs from 200Hz to 1kHz. Just an observation.

All the best.

JPC


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## gnoto (Mar 21, 2013)

Hi, thanks for the reply. Unfortunately Audyssey is fully automatic and this is the result. I would try to use the "design" mode to correct the problem. Do you have some experience?


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## AudiocRaver (Jun 6, 2012)

jaypeecee said:


> Hi gnoto,
> 
> Looks like Audyssey is doing a good job over the majority of the audio spectrum. However, I do notice that it seems not to have done a great deal to smooth the peaks and troughs from 200Hz to 1kHz. Just an observation.
> 
> ...


Good point. It would be useful to see plots of the Left and Right (each with sub) taken individually. Then we might have further suggestions.


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## gnoto (Mar 21, 2013)

Here is the measure for the front L & R channels (Audyssey Flat on).
Audyssey has done a good job if you consider the two channels.
Also attach the file .Mdat for those who have the patience to give it a look. Thank you.


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## AudiocRaver (Jun 6, 2012)

Good job with the last measurements. It does appear that Audyssey is doing a "minimalist" correction job, but the correction looks adequate. What version of Audyssey MultiEq are you using? It looks like MultiEQ standard, not XT, is that correct?

Your RT60 looks high, close to a second, a very reflective, live room. Some broad band room treatment is probably the most important thing you could do to improve your sound.


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## gnoto (Mar 21, 2013)

Audyssey MultiEQ XT32 calibrated with Audyssey pro kit.


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## AudiocRaver (Jun 6, 2012)

This is purely a curiosity question. I would have expected MultiEQ XT32 to do more detailed flattening of the frequency response curves. The midrange from 200 Hz to 1 KHz was left untouched by MultiEQ for both the left and right main speakers, and I have usually seen those areas quite smoothed by MultiEQ. Have you specifically selected Pro options to minimize the amount of flattening performed by XT32, or are you using default option settings?

Also, it does appear that mic position was not moved from the time of running MultiEQ to the time of taking the resulting measurement with REW, is that correct?

Not indicating that there is any problem at all, just a little stumped that MultiEQ did not flatten out those curves a little more, as I have typically seen it do. Just curious.


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## gnoto (Mar 21, 2013)

First of all I would like to point out that in the graph the two responses are a right channel and the other the left channel.
I used the default Audyssey setting (during the REW session I used the Audyssey Flat profile).
My interpretation of the Audyssey behavior in the central frequencies is that the two speaker have an opposite behavior and therefore the equalization works to optimize both.
The Audyssey microphone is different from the REW microphone (UMIK-1), however, they were placed in the same position (MLP) with 90deg orientation (ceiling oriented).


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