Alignment Tool — IR: What informs cursor position?

[mitchjrj]

Having developed some familiarity with the Alignment Tool phase section through crossover testing I’m trying to understand the IR function. To align IR at cursor, what cursor position would you select and why?

 

[jtalden]

Pick a point near the center of the XO range, but avoid any position that that has an SPL dip in either of the measurements. Select "Filter IRs at the cursor" then "Align IRs at cursor". If the first 5 large peaks do not overlap well move the cursor a little to another position that has good SPL support and try again.

 

[mitchjrj]

…move the cursor a little to another position that has good SPL support and try again.

Thanks, mate.

With that in mind is there an advantage one way or another (phase vs IR) for calculating sub alignment delays?

 

[jtalden]

I don't know. Either way can be difficult if the XO range is cluttered with room effects. I have always used the phase tracking method and only checked out the filtered IR method a few times to confirm it works.

 

[Foly83]

Hello
I am very interested in the new tool.
Are there any findings with the new impulse alianment method regarding subwoofer to subwoofer with a DBA?
The rear subwoofers have to be delayed. It shouldn't overlap, but be offset, right?
@jtalden, since you had already helped me back then in an understandable way.
I would be very happy if you would also take the time to do this.
I would upload a measurement and hope for an answer
Since I have a new preamp I am currently working on my setting again.
The subwoofers are the same at the front and rear. DB1 B&W
I have already adjusted the volume of the subs (see picture)
FL
FR
BL
BR

completely without EQ. BM controls at 110hz for my measurement, which is also the Xo.
Enclosed my measurement
LFE DBA is what I have set on my preamp including information in the notes.
I look forward to seeing and learning your now how. What you would do differently
Best regards Alex

 

[jtalden]

Well Done.
The timings between the 4 SWs is ideal.
The timing between the L,R mains and 4SWs is also ideal. It is the conventional target.
No changes are needed (with the possible exception of SWs level adjustment) prior to EQ to your selected house curve.

Option:
I also inverted the 4 SWs polarity and adjusted the SWs delay by -4.5 ms to see if the already good phase tracking is improved. The phase tracking was similar to the current setting and really didn't show much improvement, but there was a minor improvement in SPL support in the XO region. See below.

Red is current settings and blue is the optional one.

 

[Foly83]

Thank you again.
I ignored the polarity at first, both are facing each other and work as a push pull.
Perhaps the couch is also causing it in the rear area.
But as soon as I get home I will have another look and check if there is a positive change in the frequency response after the connection to the front speakers.
best regards Alex

 

[jtalden]

The option provided is still a DBA setup as all 4 SWs are inverted from their current DBA polarity settings.

 

[Foly83]

Many thanks for the information.
I had overlooked the fact that you meant all 4 subwoofers.
In other words, front L/R normal and rear L/R inverted to front L/R inverted and rear L/R normal.
If you still have the corrected .mdat on your computer, I would be happy to see it.
I thought that the rear ones must always be inverted as they absorb the sound wave.
best regards Alex

 

[jtalden]

I thought that the rear ones must always be inverted as they absorb the sound wave.

Yes, the rear polarity must always be opposed to the front polarity to absorb the sound wave.