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post #1 of 10 Old 07-19-16, 06:58 AM Thread Starter
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First REW measurements

Hello HTS community!

First of all congratulation for the vast amount of good informations present on this forum! Very impressive!

Im new here and new in REW users world, maybe you can help me with some info.
Just trying to get the best sound from my system and I hope REW and maybe in the short future a miniDSP will help.

I bought a ECM8000 mic + M-audio fast track and made my first measurements (after reading a lot of forum posts, calibration, level matching and so on).
The first thing I wanted to check is the subwoofer phase, so I made a 15-300 Hz measurements for sub (SVS SB2000) and front L+R (Jbl studio530) with Audyssey On, Dynamic EQ off (Denon AVR X1000) and the crossover @ 80Hz.

Until now I only used the subwoofer phase at 0 degree and also the initial Audyssey calibration was made for phase 0.
The results are strange for me:
1- The original phase=0 give a nice flat response until 45Hz but after that I see a lot of dips (room modes maybe), including at the crossover frequency of 80Hz.
2- The phase = 180 its also not very smooth but the dips are smaller and the crossover @80Hz looks better to me.
3- I also dont understand why the frequency response above 80Hz is influenced so much by the subwoofer phase (should be only the front speakers working here)

Any advice would be appreciated guys!
Thanks for your time!
Attached Thumbnails
First REW measurements-180phase.jpg  

First REW measurements-0phase.jpg  

First REW measurements-0-180phase.jpg  


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post #2 of 10 Old 07-19-16, 09:10 AM
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Re: First REW measurements

Welcome!
> As you noted, the XO range looks good with the phase set to 180. That is the far better setting. Overall with the 180 phase setting the response is reasonable.
> The impact of the SW above the XO (80-160 Hz) is normal. The SW is rolling off in that range, but still has some influence.
> Below the XO range is a bigger question. The impact of the Mains should not be much influence at 40 Hz. Is the AVR set for "Mains = Small"? If not, then setting them to "Small" may help smooth out the range below the XO a little.
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post #3 of 10 Old 07-19-16, 10:04 AM Thread Starter
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Re: First REW measurements

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jtalden wrote: View Post
Welcome!
> As you noted, the XO range looks good with the phase set to 180. That is the far better setting. Overall with the 180 phase setting the response is reasonable.
> The impact of the SW above the XO (80-160 Hz) is normal. The SW is rolling off in that range, but still has some influence.
> Below the XO range is a bigger question. The impact of the Mains should not be much influence at 40 Hz. Is the AVR set for "Mains = Small"? If not, then setting them to "Small" may help smooth out the range below the XO a little.
Thanks for the reply jtalden!

All speakers are set as small with individual XO (front @ 80, center @ 90 and surrounds @ 120Hz).
In this case a first step would be to keep the phase at 180 and maybe rerun Audyssey calibration (because the initial calibration was for 0), or would not make a big difference?

After reading The Science of Audio - a series of lectures by Floyd E. Toole I made some calculation and found the first-order resonance at around 32, 41, 68 Hz (l, L, H). Maybe thats the reason for the big dip around 40hz?! Maybe moving the subwoofer would help but I cant because of the furniture ; I attached a picture.
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post #4 of 10 Old 07-19-16, 10:14 AM
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Re: First REW measurements

You're going to have to experiment and measure... see what happens. You can most certainly change the response of the sub at your seating position by simply moving the subwoofer around the room.

By the way... great picture! Beautiful set-up.

Would you mind starting a thread over in the Finished Room Photos section... detail your gear and post some pictures? I'm sure others would love to see it.
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post #5 of 10 Old 07-19-16, 11:42 AM
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Re: First REW measurements

..."keep the phase at 180 and maybe rerun Audyssey calibration" ?
I don't know enough about Audyssey to predict that impact on the response. Just based on the SPL the current 180 setting is pretty good through XO range. It doesn't appear that there is much room for improvement.

Yep, moving the SW has a big impact on bass response. A new Audyssey calibration will be needed for the final position, but you could choose what position to use with Audyssey turned off.
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post #6 of 10 Old 07-19-16, 03:06 PM Thread Starter
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Re: First REW measurements

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Todd Anderson wrote: View Post
By the way... great picture! Beautiful set-up.
Would you mind starting a thread over in the Finished Room Photos section... detail your gear and post some pictures? I'm sure others would love to see it.
Thanks Todd!
It will be my pleasure to share with others, will start a new thread asap!

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post #7 of 10 Old 07-19-16, 03:10 PM Thread Starter
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Re: First REW measurements

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jtalden wrote: View Post
..."keep the phase at 180 and maybe rerun Audyssey calibration" ?
I don't know enough about Audyssey to predict that impact on the response. Just based on the SPL the current 180 setting is pretty good through XO range. It doesn't appear that there is much room for improvement.

Yep, moving the SW has a big impact on bass response. A new Audyssey calibration will be needed for the final position, but you could choose what position to use with Audyssey turned off.
I will discuss this issue with the customer support of SVS, they are very responsive and helpful in those problems. Also I will try to switch Audyssey off and move it around the room to see different results.
A big improvement would be a second subwoofer and a miniDSP....but I need to save so money first

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post #8 of 10 Old 07-26-16, 02:50 AM Thread Starter
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Re: First REW measurements

Hello,

I did discused with Ed Mullen from SVS about my phase settings of the subwoofer and his advices are very good and detailed; I will try to make some new tests according with his advices and come back with feedback. Bellow his answer about this matter:

"The first thing I would check is the polarity of the JBL mains with a 9V battery. Touch the battery terminals to the binding posts (+ to + and - to -) and observe the direction the woofer moves. It should move outward. If it pulls inward, then reverse the wiring at the speaker and re-run Audyssey.

The phase integration of the speakers and the subwoofer is a complex subject. The acoustic phase response of the speakers and the subwoofer both above and below the selected crossover will affect the combined FR.

In addition to that, the AVR is imposing asymmetrical filter slopes - 12 dB/octave on the high pass applied to the speakers and 24 dB/octave on the low pass applied to the subwoofer. This can also create phase-related anomalies.

Even though the slope on the subwoofer channel low pass is 24 dB/octave, it' not a brick wall and there will still be speaker/subwoofer interaction above the crossover frequency.

Looking at just the subwoofer FR and just the speaker FR can also be revealing as it relates to either room modes or possibly the interaction between the speakers themselves. After all, there are two speakers in the room at different locations both getting the same signal - so the FR of each speaker measured individually and both speakers measured together will also look different.

In the end, if all your speakers test out with positive polarity with the battery test and the combined FR looks better (and more importantly sounds better) with the subwoofer phase set to 180, then by all means leave it that way.

As a precaution, I would also check the combined response of the subwoofer and the center channel in a similar manner to see what's happening there."

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post #9 of 10 Old 07-26-16, 07:38 AM
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Re: First REW measurements

Yes, All good comments from SVS.
What is bothering you about the setup? Is it the fact that that the response is better with a 180 SW setting? Your response is pretty good that way. The important part is getting the SPL through the XO range to be as flat as possible. Finding a 180 setting advantageous is not an uncommon condition for all the reasons SVS stated. Many of us find the this condition.

We can choose the best speaker/SW/LP positions by experimentation with different locations and adjustment of the SW phase or SW distance settings to find the most advantageous result for each option. Acoustic Room treatments or adding a 2nd SW can also be very helpful. Even doing that, almost everybody still has nulls in or near that range that can't be avoided. Without significant changes to the room setup the 180 setting is probably as good as can be achieved and should be used. I suggest listening to it for a while if you haven't done that yet.
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post #10 of 10 Old 07-26-16, 08:25 AM Thread Starter
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Re: First REW measurements

Quote:
jtalden wrote: View Post
Yes, All good comments from SVS.
What is bothering you about the setup? Is it the fact that that the response is better with a 180 SW setting? Your response is pretty good that way. The important part is getting the SPL through the XO range to be as flat as possible. Finding a 180 setting advantageous is not an uncommon condition for all the reasons SVS stated. Many of us find the this condition.

We can choose the best speaker/SW/LP positions by experimentation with different locations and adjustment of the SW phase or SW distance settings to find the most advantageous result for each option. Acoustic Room treatments or adding a 2nd SW can also be very helpful. Even doing that, almost everybody still has nulls in or near that range that can't be avoided. Without significant changes to the room setup the 180 setting is probably as good as can be achieved and should be used. I suggest listening to it for a while if you haven't done that yet.
It's trange to find a better result @180. Considering that Chris Kyriakakis from Audyssey always said to set the phase to 0 (quote: " Phase controls on subs are not useful because they only change the phase at one frequency and thus leave the remaining frequencies unchanged.")
But in the end the way it sounds is the most important factor; so I will continue to listen to them in both ways and choose the best sounding phase.
And yes, will be adding a second subwoofer soon for better overall sound.

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