REW Alignment tool - Guides or Manual?

lexicon

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Tricky to get your head around this concept I agree.
Delays in ms work conversely to distance in metres or feet. 1ms delay does not quite equate to 1ft closer in distance (speed of sound related) but it’s close enough - 88.5ms = 100ft.
By decreasing sub distance the receiver will see the sub as closer to the other speakers.
As it is seen as closer, the receiver will apply MORE DELAY in ms to slow it down to give the other speakers more time to catch it up.
At least that’s how I understand it.
 

jtalden

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May 22, 2017
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447
Location
Arizona, USA
My AV System  
Preamp, Processor or Receiver
Marantz AV7705 Pre/Pro
Main Amp
Rotel RMB-1066 6 chnl P-amp x 2
Additional Amp
Behringer DCX2496 x 2
Universal / Blu-ray / CD Player
OPPO BDP-103 Universal Player
Front Speakers
DIY SEAS H1456/H1212 Spkr x 5
Subwoofers
DIY JBL 2235H 15" SW x 2
Video Display Device
JVC DLA-X790R
Screen
Da-Lite Da-Snap 39105V - 92"
I get confused all the time so it is good to question. In this case I think No. 9 statement is correct.
A decrease in the SW distance setting (relative to mains distance settings) in a AVR is the same as increasing the SWs delay in the DSP. In your particular case however we needed a reduction of SW delay in the DSP instead of an increase, so we needed to increase the SWs distance in your stereo preamp.

Because we sometime get it wrong we then remeasure after making the change to confirm the timing. The phase tracking should then be as predicted and the impulse overlay chart of the SW and mains impulses should show the relative positioning that we targeted.
 

jtalden

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Joined
May 22, 2017
Messages
447
Location
Arizona, USA
My AV System  
Preamp, Processor or Receiver
Marantz AV7705 Pre/Pro
Main Amp
Rotel RMB-1066 6 chnl P-amp x 2
Additional Amp
Behringer DCX2496 x 2
Universal / Blu-ray / CD Player
OPPO BDP-103 Universal Player
Front Speakers
DIY SEAS H1456/H1212 Spkr x 5
Subwoofers
DIY JBL 2235H 15" SW x 2
Video Display Device
JVC DLA-X790R
Screen
Da-Lite Da-Snap 39105V - 92"
Cross post above. We are in agreement now.

Note that the REW tool indicates the change needed in both ms and distance for us so we don't need to manually do the conversion. REW does not indicate the direction of the distance change only the magnitude. It is bit confusing to me, but it's easy enough to just confirm any change with measurements.
 

Harrycr

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Thanks
So we just enter whatever REW suggests into the AVR.

For time alignment of 2 x subs:
Match level of sub A to sub B
Time align of the 2 x subs
Eq as one (combined mono) with same filters entered into each sub.

With time alignment of the 2 x subs what speaker is used as the reference?

Thank you
 

lexicon

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What equipment are you using? Doesn’t matter which speaker you use as the timing ref as long as you use the same one for all. I use 1.8.
 

jtalden

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Joined
May 22, 2017
Messages
447
Location
Arizona, USA
My AV System  
Preamp, Processor or Receiver
Marantz AV7705 Pre/Pro
Main Amp
Rotel RMB-1066 6 chnl P-amp x 2
Additional Amp
Behringer DCX2496 x 2
Universal / Blu-ray / CD Player
OPPO BDP-103 Universal Player
Front Speakers
DIY SEAS H1456/H1212 Spkr x 5
Subwoofers
DIY JBL 2235H 15" SW x 2
Video Display Device
JVC DLA-X790R
Screen
Da-Lite Da-Snap 39105V - 92"
Thanks
So we just enter whatever REW suggests into the AVR.
Sort of...
We use the REW alignment tool to select favorable setting changes for; DSP delay timing (AVR distance settings), gain, and polarity for the 2 SWs. The tool allows us to save these settings as a measurement and records the changes applied in the measurement notes.
For time alignment of 2 x subs:
Match level of sub A to sub B
We are looking to provide a relatively smooth SPL response that will respond well to EQ. Matching levels at the LP is usually fine. Matching SW gain settings is also usually fine. It can sometime be beneficial to use other gain settings. Relative SW levels is often not a big factor. Often all that is needed is to adjust the timing. The room setup and SW capacity are significant factors so there may sometimes be benefits to adjusting gain settings. The REW tool allows us to evaluate the impact of timing, gain and polarity setting changes to chose a favorable combination.
Eq as one (combined mono) with same filters entered into each sub.
This is the conventional approach.
 
Last edited:

Harrycr

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Apr 22, 2020
Messages
32
Thank you
To time align subs to work together as mono, one sub placed up front of the room and other behind the couch.
Do I use a speaker (a main) as a reference to align to each sub or use the other sub?
To time align doesn't the reference speaker have to have a tweeter?

Thanks again
 
Last edited:

jtalden

Senior Member
Joined
May 22, 2017
Messages
447
Location
Arizona, USA
My AV System  
Preamp, Processor or Receiver
Marantz AV7705 Pre/Pro
Main Amp
Rotel RMB-1066 6 chnl P-amp x 2
Additional Amp
Behringer DCX2496 x 2
Universal / Blu-ray / CD Player
OPPO BDP-103 Universal Player
Front Speakers
DIY SEAS H1456/H1212 Spkr x 5
Subwoofers
DIY JBL 2235H 15" SW x 2
Video Display Device
JVC DLA-X790R
Screen
Da-Lite Da-Snap 39105V - 92"
Use the same main speaker for both SW measurements.
 

jtalden

Senior Member
Joined
May 22, 2017
Messages
447
Location
Arizona, USA
My AV System  
Preamp, Processor or Receiver
Marantz AV7705 Pre/Pro
Main Amp
Rotel RMB-1066 6 chnl P-amp x 2
Additional Amp
Behringer DCX2496 x 2
Universal / Blu-ray / CD Player
OPPO BDP-103 Universal Player
Front Speakers
DIY SEAS H1456/H1212 Spkr x 5
Subwoofers
DIY JBL 2235H 15" SW x 2
Video Display Device
JVC DLA-X790R
Screen
Da-Lite Da-Snap 39105V - 92"
Adjust and verify...

For timing of 2 SWs I would not expect any timing change would be needed as a result of mono EQ. We select the timing that results in the best phase relationship pre EQ. The EQ impacts the phase of both SWs in similar manner thus retaining the same relationship after EQ.

For timing of XOs, the 2 independent EQs can change the relative phase tracking across the XO range. I haven't seen a case where the timing was significantly changed in my limited DIY setups, but there are a wide variety of setups so it may be significant in some cases.
 
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