Settings in REW for Nearfield Measurements - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 25 Old 05-31-13, 06:53 PM Thread Starter
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Settings in REW for Nearfield Measurements

Hi can someone please tell me the settings.

Thanks in advance
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post #2 of 25 Old 06-01-13, 01:05 AM
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Re: Settings in REW for Nearfield Measurements

Do you mean "narrow IR window" settings?

Mic distance needs to be close but far enough away for transducer integration - 0.5 m for small 2-way, 1 m for 3-way or small floor standing, 2 m for large multi-way floor standing - on tweeter axis or, if really close, on axis midway between tweeter and midrange driver.

In REW > IR Windows > Right Window: try values between 2 ms and 5 ms, then click on Apply Windows.

REW smoothing 1/24 oct or 1/48 oct.
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post #3 of 25 Old 06-01-13, 03:02 AM Thread Starter
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Re: Settings in REW for Nearfield Measurements

Quote:
AudiocRaver wrote: View Post
Do you mean "narrow IR window" settings?

Mic distance needs to be close but far enough away for transducer integration - 0.5 m for small 2-way, 1 m for 3-way or small floor standing, 2 m for large multi-way floor standing - on tweeter axis or, if really close, on axis midway between tweeter and midrange driver.

In REW > IR Windows > Right Window: try values between 2 ms and 5 ms, then click on Apply Windows.

REW smoothing 1/24 oct or 1/48 oct.
Thank you very much.

I am trying to get a near field measurement for my Energy Veritas 2.3i floor standers. The 2.4i were the biggest in the range.
I am trying to determine what the manufacturer intended them to sound like characteristics etc.

For this size speaker which would you recommend distance wise etc?

For the REW settings i am trying to setup the program to give me the near field results without room interference etc. I don't want to take the speakers outside.

Currently the IR window left and right is set to Tukey 0.25, is this ok?

Thanks again
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post #4 of 25 Old 06-01-13, 12:06 PM
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Re: Settings in REW for Nearfield Measurements

Unfortunately, no one can tell you what gate settings to use in your room.....you need to take a measurement with the speaker and mic in your desired position and look at the impulse to see where the first reflection happens. When you click on the IR Windows button, don't worry about the "Left" and "Right" window setting at the top. Leave that where it's set. What you need to change is the "Left Window (ms)" and "Right Window (ms)". In order to set those right you need to make a measurement.

In my picture is an impulse from my speaker, which is on a stand and the mic is about 6 feet from the speaker. You can see I have the first reflection marked. It will be the first major blip after the initial impulse from the speaker flattens out. This is a reflection from the room, and you don't want that. In my case shown, I set the left window to about .5ms before the initial rise of the impulse and the right window to a little less than 3ms. This will set the gate and window out the room influence. The only caveat here is that since we are truncating the impulse of the speaker we can't see all the information. A 3ms gate will give you info from about 300hz up. IMO the data below 1Khz is questionable because the frequency resolution is quite low to see the detail of what's actually going on, but it will give you a good idea of the basic trend. You can't set the gate long enough to get LF data without the room swamping the response.
Attached Thumbnails
Settings in REW for Nearfield Measurements-rew-gate.jpg  

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post #5 of 25 Old 06-03-13, 11:06 PM Thread Starter
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Re: Settings in REW for Nearfield Measurements

Quote:
natehansen66 wrote: View Post
Unfortunately, no one can tell you what gate settings to use in your room.....you need to take a measurement with the speaker and mic in your desired position and look at the impulse to see where the first reflection happens. When you click on the IR Windows button, don't worry about the "Left" and "Right" window setting at the top. Leave that where it's set. What you need to change is the "Left Window (ms)" and "Right Window (ms)". In order to set those right you need to make a measurement.

In my picture is an impulse from my speaker, which is on a stand and the mic is about 6 feet from the speaker. You can see I have the first reflection marked. It will be the first major blip after the initial impulse from the speaker flattens out. This is a reflection from the room, and you don't want that. In my case shown, I set the left window to about .5ms before the initial rise of the impulse and the right window to a little less than 3ms. This will set the gate and window out the room influence. The only caveat here is that since we are truncating the impulse of the speaker we can't see all the information. A 3ms gate will give you info from about 300hz up. IMO the data below 1Khz is questionable because the frequency resolution is quite low to see the detail of what's actually going on, but it will give you a good idea of the basic trend. You can't set the gate long enough to get LF data without the room swamping the response.
Thank you

How did you determine the 6 feet for measurements, the same as above posts?

Did you position the mic between the tweeter and mid range?

Thanks again
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post #6 of 25 Old 06-06-13, 06:36 PM
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Re: Settings in REW for Nearfield Measurements

My speakers are Synergy horns, so the mid and tweeter radiate from the same "point" in the horn. I determined the 6' because that's about as far away as I feel I can get in room and still get good data. I'd like to go outside and go 12' or so ideally.

In your case positioning between the mid and tweet 1 meter from the speaker should do it if you're trying to see how well it matches up to the manufacturer's anechoic response. 1 meter distance is typical.
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post #7 of 25 Old 06-07-13, 08:33 AM
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Re: Settings in REW for Nearfield Measurements

Quote:
natehansen66 wrote: View Post
My speakers are Synergy horns, so the mid and tweeter radiate from the same "point" in the horn. I determined the 6' because that's about as far away as I feel I can get in room and still get good data. I'd like to go outside and go 12' or so ideally.

In your case positioning between the mid and tweet 1 meter from the speaker should do it if you're trying to see how well it matches up to the manufacturer's anechoic response. 1 meter distance is typical.
Hello Nate,

Would you be willing to share a bit more info on Synergy horns? Are these DIY?

Above posted IR is very tantalizing. According to theory, you should be able to get good measurements even with microphone in plane of horn opening.

-----------------

With my DSP based clones of Linkwitz Pluto, driver setup allows referencing at 23cm. Inverse transfer functions of each driver become basis of EQ/crossover with convolution setup. First reflection becomes floor bounce that is essentially directly below speaker/microphone, with round trip of about 6ms.

Measured FR at 23cm, no smoothing and very big window:



Measured FR at 107cm, no smoothing very big window:




Using same 107cm measurement, with same very big window, but gating data to 3ms the response looks like this:



No additional smoothing is applied to above result. Dips in raw 107cm result are really what happens when reflections come into play, but human perception is much more like gated result. Only tones with significant sustain allow hearing the dips that are setup. The direct sound of speaker is single most important in playback. Equalizing for room gain and peaks/dips for listening setup then follow, if really needed/desired.

Normalized full scale view of 23cm measure of IR:

Settings in REW for Nearfield Measurements-ir-23cm-overview.png

And above zoomed in:

Settings in REW for Nearfield Measurements-ir-23cm-zoom.png


View of 107cm measure of IR:

Settings in REW for Nearfield Measurements-ir-107cm-zoom.png

In last picture reflection a bit past 1ms is seen. This is reflections from microphone body mounted to tripod. This reflection is present, but very hard to pick out in 23cm measurements, and do to geometry of closer setup occurs a little earlier.

Similarly, little peak in Nate's pic at about 0.8ms may partially be microphone related reflection.

Regards,

Andrew
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post #8 of 25 Old 06-07-13, 04:53 PM
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Re: Settings in REW for Nearfield Measurements

To keep from derailing the thread too far....I should have said "DIY" Synergy horns, and Paralines at that. These are no way indicative of anything from Danley. As you can see mine have their issues
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post #9 of 25 Old 06-07-13, 06:25 PM Thread Starter
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Re: Settings in REW for Nearfield Measurements

Quote:
natehansen66 wrote: View Post
In your case positioning between the mid and tweet 1 meter from the speaker should do it if you're trying to see how well it matches up to the manufacturer's anechoic response. 1 meter distance is typical.
Thank you

I can't find the manufacturer's anechoic response, i have emailed Energy but because of changes they haven't got records of this. Any ideas would be appreciated.

I will give this a go and post the results.

Thanks again
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post #10 of 25 Old 06-07-13, 06:32 PM Thread Starter
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Re: Settings in REW for Nearfield Measurements

Quote:
The direct sound of speaker is single most important in playback. Equalizing for room gain and peaks/dips for listening setup then follow, if really needed/desired.

Thank you

Interesting, i have heard that equalizing for the direct sound can be preferred.

Also seen that equalizing using the Anechoic response as a target can give the listener the true response the manufacturer intended, or close as possible.
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