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REW from listening position


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Hi, I’m using REW extensively in combination with Xilica.  I understand the point of 1meter measurements to try to measure speaker only, with minimal room interactions.  I’m starting to also take measurements at listen position, which is a very different frequency response. Has anybody found listening position measurements helpful, either for adjusting EQ or understanding room interaction better?

thanks, Ted

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5 hours ago, BadChile said:

I used listening position measurements exclusively; but my usage is to develop a response curve for a MiniDSP HD to apply to my subwoofer feed.  Helped immensely.

 

Me too.  I used it exclusively to dial in my THT subwoofers.

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IMO, measuring at a considerable distance from the speakers and from just one position, even if it is the Main Listening Position, with REW is a mistake, unless, perhaps, you listen alone and keep your head in the same position during each listening session.  As you know, there are modes and nulls that alter bass response, different specular and diffuse reflections and different patterns of beaming, with different treble response.  See http://www.acousticfrontiers.com/wp-content/uploads/2015/03/room_mode_calc.gif

 

What Are Room Modes - GIK Acoustics

Moving your head a few inches might produce considerably different results.  This is the primary reason both Paul W. Klipsch and Edgar Villchur were against the use of graphic equalizers, because the ideal response in one position could result in lousy response if you moved to a slightly different one.  That may be the only thing Paul and Edgar ever agreed  on!😁😬  There are several ways to attempt to get around this.  One is to take an average of several positions.  How many?  The lowest number I've heard is 3.  Room correction devices often use considerably more; Audyssey uses 8, Dirac 9 to 17.  Rather than a simple average, room correction often uses proprietary "fuzzy logic" (a good thing) processing.  Because of this, it might be a good idea to start with one of these devices, then measure from multiple positions -- or just trust the device to provide smooth enough response.

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In my last HT I did all my measurements from about 6" behind my head and it sounded great...now I will say the room was fully soundproofed and treated to where it was just about to dead (straddle the line between dead and reflective to a very fine line, which some might say was too dead, but the ones who heard it thought it was perfect). This setup was with JBL 2360A, EV DH1a drivers, Qpies, and DTS10 subs.

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  • 3 weeks later...

Well, I’ve been working with REW / Xilica lately. Measuring on/off axis at 1m, and at listening position. Axis changes in FQ are not significant, due to k402 design no doubt. Listening position, oh boy! I always thought that my system didn’t sound as good as possible, but when I measured listening position I saw a 10 db hump centered at 1000hz, no wonder. When I made that go away, I got a big increase in clarity. Also, I don’t no why, but I had 1 speaker set 1.5ms delayed, correcting this also noticeable increased clarity.  
Now I want to get the phase cleaned up as @Chris A has recommended, I got rid of preset xo settings, but still have over 1000 degrees of phase.

not sure how to proceed.

Anyone with simple steps to help phase?

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20 minutes ago, VDS said:

oh boy! I always thought that my system didn’t sound as good as possible, but when I measured listening position I saw a 10 db hump centered at 1000hz, no wonder.

thats what I need... I am still struggling slightly with getting my 402's to sound how I want them to sound, though I know for sure it's only a matter of time.

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I’m sure more attention to room treatment would help reduce the buildup of certain frequencies, but Xilica gives the option to reduce the frequencies at the source.

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what is funny to me is that WHOLE SECTIONS of recordings are missing from music I listen to. I can put on a recording and play it back thru headphones or other speakers and here an accompanying instrument clearly and predominantly... and then I put on that exact same recording and the recording sound fairly good... HOWEVER, those accompanying instruments are COMPLETELY absent, just like they were never in the song. the only difference between the two playbacks is the introduction of the Xilica. it's not room modes.

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4 hours ago, VDS said:

Well, I’ve been working with REW / Xilica lately. Measuring on/off axis at 1m, and at listening position. Axis changes in FQ are not significant, due to k402 design no doubt. Listening position, oh boy! I always thought that my system didn’t sound as good as possible, but when I measured listening position I saw a 10 db hump centered at 1000hz, no wonder. When I made that go away, I got a big increase in clarity. Also, I don’t no why, but I had 1 speaker set 1.5ms delayed, correcting this also noticeable increased clarity.  
Now I want to get the phase cleaned up as @Chris A has recommended, I got rid of preset xo settings, but still have over 1000 degrees of phase.

not sure how to proceed.

Anyone with simple steps to help phase?

VDS,

Getting phase  flattened made a a more noticeable difference than a really flat SPL.

Here are a couple of references -

https://audiophilestyle.com/forums/topic/30035-using-rew-and-rephase-to-generate-amplitude-and-time-domain-corrections/?tab=comments#comment-604620

https://audiophilestyle.com/forums/topic/30035-using-rew-and-rephase-to-generate-amplitude-and-time-domain-corrections/?do=findComment&comment=678965

Here is my modified K-Horn where I have flattened the phase.

Phase smoothing requires FIR filters which may not be available on the Xilica. I bet that the DSP for the new Jubilee is using FIR filters.

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  • 1 month later...
On 4/24/2022 at 5:23 PM, Wirrunna said:

VDS,

Getting phase  flattened made a a more noticeable difference than a really flat SPL.

Here are a couple of references -

https://audiophilestyle.com/forums/topic/30035-using-rew-and-rephase-to-generate-amplitude-and-time-domain-corrections/?tab=comments#comment-604620

https://audiophilestyle.com/forums/topic/30035-using-rew-and-rephase-to-generate-amplitude-and-time-domain-corrections/?do=findComment&comment=678965

Here is my modified K-Horn where I have flattened the phase.

Phase smoothing requires FIR filters which may not be available on the Xilica. I bet that the DSP for the new Jubilee is using FIR filters.

I’ve been working on phase but I’m stuck at about 400 degrees. I don’t have access to FIR filters with my Xilica XP. Phase seems so touchy. @Chris A seems to have done it w/o for, but I can’t quite get it yet.

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On 4/24/2022 at 6:23 PM, Wirrunna said:

VDS,

Getting phase  flattened made a a more noticeable difference than a really flat SPL.

Here are a couple of references -

https://audiophilestyle.com/forums/topic/30035-using-rew-and-rephase-to-generate-amplitude-and-time-domain-corrections/?tab=comments#comment-604620

https://audiophilestyle.com/forums/topic/30035-using-rew-and-rephase-to-generate-amplitude-and-time-domain-corrections/?do=findComment&comment=678965

Here is my modified K-Horn where I have flattened the phase.

Phase smoothing requires FIR filters which may not be available on the Xilica. I bet that the DSP for the new Jubilee is using FIR filters.

I disagree with that .

 

The first priority is to get the amplitude spectrum to be fairly flat. After that, then worry about the phase spectrum. There are some obvious targets including a speaker accidently wired out of phase, or a time delay (group delay) due to physical alignment - but those are easy fixes with DSP. BTW,  Most DSP does not have FIR filters. Devote your energy to the amplitude spectrum first. 

 

I have tried some of Chris's suggestions (he has provided useful guides on this forum). While the improvements (when "flattening" the phase spectrum), are noticeable, I find them a bit subtle. IMHO, I would not call them "night and day differences". That said, I will be employing them in my next "forever speaker"

Edited by PrestonTom
clarification
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28 minutes ago, VDS said:

I’ve been working on phase but I’m stuck at about 400 degrees. I don’t have access to FIR filters with my Xilica XP. Phase seems so touchy. @Chris A seems to have done it w/o for, but I can’t quite get it yet.

send a PM to @Chris A  with your questions ,u Chris is not  on the forum regularly , but he checks his PM's from time to time

 

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11 hours ago, VDS said:

I’ve been working on phase but I’m stuck at about 400 degrees. I don’t have access to FIR filters with my Xilica XP. Phase seems so touchy. @Chris A seems to have done it w/o for, but I can’t quite get it yet.

If you check one of Chris's threads look at his signature line and he has links to several archival threads that he created. In those he has good guides on how to set up the time alignment, filters and crossovers in order to minimize any large shifts in phase (using DSP units that do not provide FIR filters).

 

Give that a try (his directions are clear and concise). If you want to take it the next step then the Xilica XD series (not the XP series) can be employed (note, they are more expensive) or a more affordable box might be something from mini-DSP (OpenDRC hardware with re-Phase software). 

 

Good luck,

-Tom

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Tom, I sent @Chris A a request for help. Currently I'm going in circles checking Group Delay, Spectagram, delay and FR, trying to figure out their relationship to phase.
Phase so far is kind of a moving target!

Ted

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