Settings in REW for Nearfield Measurements - Page 3 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #21 of 25 Old 06-15-13, 06:19 PM Thread Starter
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Re: Settings in REW for Nearfield Measurements

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adjusting all windows to 12ms Blackmann-Harris 7, smoothing 1/6 octave,

Attachment 42568
Using Blackman - Harris 7, why use this?

Also how did you come up with the figure 12ms?

Thanks
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post #22 of 25 Old 06-15-13, 10:48 PM
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Re: Settings in REW for Nearfield Measurements

Blackman type windows are smooth and highly symmetrical. They introduce very little ripple in FR display relative to other types. "7" refers to number of terms in formula. This has smooth performance over very large dynamic range, four terms is really quite sufficient for 16bit data on CD; even exceptional speaker and measurement circumstance is typically <12bits of useful dynamic range.


In near field measurements, ratio of direct to reflected sound is very high. For Blackman-Harris 7 12ms window, weighting is 50% at 3ms, and falls off rapidly. Combination leads to very good overview. Exact shape of curve going down to 60Hz may be overly smooth, but likely captures realistic -6dB point of speaker with minimal interaction of floor and walls. This low frequency curve fall off as microphone moves closer due to relative spacing of dual woofers and port.

In summary: You don't like the low end of your speakers, so you got two subs, and apparently you are not happy with the high end either. I'd seriously consider a nice pair of active two-ways with sealed cabinets so they integrate well with subs.
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post #23 of 25 Old 06-16-13, 12:32 AM Thread Starter
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Re: Settings in REW for Nearfield Measurements

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Barleywater wrote: View Post
Blackman type windows are smooth and highly symmetrical. They introduce very little ripple in FR display relative to other types. "7" refers to number of terms in formula. This has smooth performance over very large dynamic range, four terms is really quite sufficient for 16bit data on CD; even exceptional speaker and measurement circumstance is typically <12bits of useful dynamic range.


In near field measurements, ratio of direct to reflected sound is very high. For Blackman-Harris 7 12ms window, weighting is 50% at 3ms, and falls off rapidly. Combination leads to very good overview. Exact shape of curve going down to 60Hz may be overly smooth, but likely captures realistic -6dB point of speaker with minimal interaction of floor and walls. This low frequency curve fall off as microphone moves closer due to relative spacing of dual woofers and port.

In summary: You don't like the low end of your speakers, so you got two subs, and apparently you are not happy with the high end either. I'd seriously consider a nice pair of active two-ways with sealed cabinets so they integrate well with subs.
Thanks

The low end is ok on there own, combined with with the 2 x REL Stratas 5s and i am happy with the low end.
With the high end looking at the nearfield measurements what are the characteristics of the speakers in your opinion e.g. lacking, bright etc. Wonder if it is my ears or room, has quite a bit of soft furnishes?

So i would use Blackman Harris 7 with 12 ms for all my future nearfield measurements?

Thanks again
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post #24 of 25 Old 06-16-13, 01:00 AM
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Re: Settings in REW for Nearfield Measurements

12ms is good for general overview; shorter windows more fully limit room interactions, and require little if any additional smoothing when concentrating on HF performance; even 1ms for working above 1kHz.

Try running some near field measures (<1m) at small angles off axis, vertical and horizontal and see how peaks and dips shift. Also do at listening position. Sometimes small changes to speaker location, and toe-in can bring significant changes to perceptions at listening location. Even though speakers are floor standers, sometimes feet or small stands that add small amount of tilt can be used for focusing alignment at listening position too.

I used to have floor standing speakers with four drivers that where very difficult to get right. Getting a friend to tweak toe-in while listening always worked better than using a tape measure and repeatedly getting up to bump a speaker a fraction of an inch this way or that.
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post #25 of 25 Old 06-16-13, 06:35 PM Thread Starter
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Re: Settings in REW for Nearfield Measurements

Quote:
Barleywater wrote: View Post
12ms is good for general overview; shorter windows more fully limit room interactions, and require little if any additional smoothing when concentrating on HF performance; even 1ms for working above 1kHz.

Try running some near field measures (<1m) at small angles off axis, vertical and horizontal and see how peaks and dips shift. Also do at listening position. Sometimes small changes to speaker location, and toe-in can bring significant changes to perceptions at listening location. Even though speakers are floor standers, sometimes feet or small stands that add small amount of tilt can be used for focusing alignment at listening position too.

I used to have floor standing speakers with four drivers that where very difficult to get right. Getting a friend to tweak toe-in while listening always worked better than using a tape measure and repeatedly getting up to bump a speaker a fraction of an inch this way or that.
Thank you very much

I originally looked at 2.7 ms.

The speakers are currently sitting on there spikes which tilt the speakers back slightly.

Toe in effect which frequencies?

Thanks again
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