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Discussion Starter #1 (Edited)
Hi All,
I have been trying to go through the subwoofer distance tweak over the last few days, but I am not making any progress... if anything, graphs look worse.

My Equipment:
Pioneer SC-1523-K AVR
FL/C/FR - Polk RTi8/CSi6
SL/SR - Polk Monitor 30
Sub - Testing 3 different subs.
1 - PSA XS15se
2 - SVS PB-1000 (might up this to the 2000)
3 - Polk PSW505 (original)

I have a pretty wide null in 60hz-80hz range, no matter which sub I use.

Is this the correct way to do the distance tweak? I am only using 1 sub at a time.

1. Disable EQ and SWAVE on the AVR.
2. In REW set all speakers to 75db.
3. Take measurements
a. Front Left - by itself. Unplug the other speakers.
b. Center - by itself. Unplug the other speakers.
c. Front Right - by itself. Unplug the other speakers.
d. Sub - by itself. Unplug the other speakers.
4. In the AVR setup, change the SW distance 1' at a time.
5. Measure the SW alone, again.
6. Keep making changes until there are no nulls or peaks.


This is what I have already tried, but maybe I am missing something.

The MLP and the R/L/C can't be moved. I'm trying to avoid using any external EQ.

Any help or advice would be great.
 

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Sub distance setting doesn't work in isolation. That's the reason you don't see the dip in FR go away in REW. Distance tweaking for sub only works when you are phase aligning the sub with the mains and/or CC.

Put your avr in stereo 2.1 mode and run the sweep with mains and sub engaged and then +/- sub distance for the smoothest transition within the crossover region i.e. usually 80 Hz or whatever you set. Repeat the same step by putting your avr into Dolby PLII Movie mode to phase align CC with sub. You won't need to disconnect/reconnect your speakers.

If you have different distance setting for sub between mains and CC; take the average and use that sub distance setting in the avr. For stereo 2.1; only mains phase aligned with sub is fine. For 5.1, CC must also be in sync with the sub.

Let's throw a spanner in the work...........It is assumed that you have found the best spot for your sub without major peaks/dips before following the steps given above.
 
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Discussion Starter #3
Here are my latest L/R/C/Sub tests.

I'm a bit confused about putting the AVR into Dolby PL because I'm doing it over HDMI, which the AVR uses PCM. If I try to change it, it changes to things like THX Cinema or Auto Surround.

I've also tried to set Windows to Stereo, but the AVR still shows PCM. Maybe this is a 007 Shark's codec thing I have to work out...

Order of images:
Center + Sub with EQ ON
Center with EQ ON
Center NO EQ
Left + Sub with EQ ON
Left with EQ ON
Left NO EQ
Right + Sub with EQ ON
Right with EQ ON
Right NO EQ

I'll upload the sub graphs next.
 

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Discussion Starter #4
Here are the sub graphs.
I'm not sure which is the best one, they mostly look the same.

Previously there were very large nulls in the 50hz area, which by moving the sub a foot to the right seems to have resolved.

What do you think? Should I EQ the peaks down closer to the target line in the images? I'm not really sure what I should do next.
 

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Here are my latest L/R/C/Sub tests.

I'm a bit confused about putting the AVR into Dolby PL because I'm doing it over HDMI, which the AVR uses PCM. If I try to change it, it changes to things like THX Cinema or Auto Surround.

I've also tried to set Windows to Stereo, but the AVR still shows PCM. Maybe this is a 007 Shark's codec thing I have to work out...
Since you're using HDMI just output to CH3 (CC) and do the sub distance tweak. Is this system primarily used for movies or music? If movies, distance tweak using the CC, if music distance tweak using FR/L.
 

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Here are the sub graphs.
I'm not sure which is the best one, they mostly look the same.

Previously there were very large nulls in the 50hz area, which by moving the sub a foot to the right seems to have resolved.

What do you think? Should I EQ the peaks down closer to the target line in the images? I'm not really sure what I should do next.
What external EQ are you using?
 

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Show us a CC+sub measurement with these limits, with your AVR's auto EQ on and off:

Vertical: 55b-105db
Horizontal: 15hz-300hz
No smoothing

Your sub only response looks pretty good, need to see the speaker/sub interaction now. ;)
 

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Could you please re-post the graphs with the proper limits I posted above?

There's something weird going on with your R+sub graph....you're losing about 5db on the low end, makes no sense. :confused:

Do you have your mains set to "small"?
 

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Discussion Starter #12
Could you please re-post the graphs with the proper limits I posted above?

There's something weird going on with your R+sub graph....you're losing about 5db on the low end, makes no sense. :confused:

Do you have your mains set to "small"?
Yes, the L/R/C are set to small.
I will try to get more graphs later tonight or tomorrow. Crazy week for me!
 

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Discussion Starter #13
This might be overkill, but here you go. No smoothing and the specs you requested.
 

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OK, are these before or after the distance tweak?

Where is your crossover set?

Depending on where your crossover is set, you should be able to improve on that big dip at 100hz....do the distance tweak and see if you can't get the crossover area to look more like the blue line I drew below. :)

You may want to measure about 10db higher. Your waterfalls and spectrograms will be pretty meaningless with measurements that low.

It looks like you are running the subs about 10db hotter than the other channels, is this correct? Also, it seems strange that your mains and center (measured without the sub) are only down about 10db at 15hz....are you certain you performed those measurements correctly and the sub was turned off??

HUGE null (~25db) at 150hz on your right speaker.

Looks like your EQ isn't doing much to help your response...like, at all.



 

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Discussion Starter #15
Alan,
Maybe I am not taking the measurements correctly.

Do I need to turn off the sub when taking measurements of L/R/C? I don't flip the switch to turn it off.

I also got a MiniDSP 2x4 with Advanced 2.1 plug-in.

I did a quick measurement last night and used the auto-eq feature in REW, which I then uploaded the config to the plug-in.
After that I did another quick measurement, looked pretty good for the sub. Pretty tight to the target line.

I should have some time tonight to check some more. I'll also re-run the EQ setup in the AVR.
 

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Yes, you need to turn the sub off (or set the speaker to LARGE) IF you want to measure just the response of each speaker alone (L/C/R). You don't really need these measurements unless you are trying to find where certain nulls & peaks are coming from and for adjusting placement of the speakers for the flattest response.

Let's see that post-MiniDSP graph! :)

You never answered my questions above.

- Did you do the sub distance tweak?
- Where is your crossover set?
 

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Discussion Starter #17
Yes, you need to turn the sub off (or set the speaker to LARGE) IF you want to measure just the response of each speaker alone (L/C/R). You don't really need these measurements unless you are trying to find where certain nulls & peaks are coming from and for adjusting placement of the speakers for the flattest response.

Let's see that post-MiniDSP graph! :)

You never answered my questions above.

- Did you do the sub distance tweak?
- Where is your crossover set?
Oh- sorry about that.

Crossover = 80hz
Sub distance tweek = I tried, but didn't get anywhere. A big part of that problem is you have to go to the GUI of the AVR to change the distance. I'm using REW through that AVR, which means I have to constantly switch back and forth. I can probably attach a 2nd monitor to the machine, so maybe that is the next step.

I am doing some home renovations (minor) so sorry for the delays. I may be able to get a graph of the MiniDSP later tonight.
 

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You can't see the AVR's GUI when using REW?? Why is that?
 

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Discussion Starter #19
You can't see the AVR's GUI when using REW?? Why is that?
When using the AVR GUI it is a full screen overlay. So you have to go into this view/mode to make the changes to distance.

Check out this video at 49 seconds.

You can see how it takes up the whole screen. Once you exit, then you can see your source again (PC).
 

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Discussion Starter #20
One more thing... when I was taking measurements of speaker + sub, in REW preferences I was setting output to channel 3 (center) and then the timing output to 4 (sub).

I guess this is wrong! :)
 
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