Rational Acoustics



Brandon
May 14th, 2010, 06:29 PM
How do I find time zero with subwoofers using IR ? The IR does not make it clear exactly when the sub information first arrives at the microphone.

Also has anyone come up with any interesting new V7 Smaart tricks ?

Regards,
Brandon

Arthur Skudra
May 15th, 2010, 12:11 AM
How do I find time zero with subwoofers using IR ? The IR does not make it clear exactly when the sub information first arrives at the microphone.

Also has anyone come up with any interesting new V7 Smaart tricks ?

Regards,
Brandon
You can try to find it using IR, but it is very difficult. Use the phase trace instead.

Brandon
May 15th, 2010, 07:13 PM
My problem is when the subwoofers are well behind the tops. I do phase align things but its tough when you have subs that are 20' behind the top boxes because you cannot get a "zero" point to delay the tops to.

I currently delay the the tops so that they are "behind" the subs, then find the delay for my measurement mic, then delay the subs to the already delayed tops. After I do that I subtract the subwoofer delay from the tops delay and apply the difference to the tops. (I hope that makes sence) I am looking for a better faster way.

Michael Häck
May 16th, 2010, 05:24 AM
My problem is when the subwoofers are well behind the tops. I do phase align things but its tough when you have subs that are 20' behind the top boxes because you cannot get a "zero" point to delay the tops to.

I currently delay the the tops so that they are "behind" the subs, then find the delay for my measurement mic, then delay the subs to the already delayed tops. After I do that I subtract the subwoofer delay from the tops delay and apply the difference to the tops. (I hope that makes sence) I am looking for a better faster way.

Brandon, my favourite for your example is: measure always on-axis and bring the mic in that position where you would like to sum the phase from top and sub (around the FoH for instance). Turn the top on with let say 3m delay offset in case your tops are 2m behind the subs.
Store the trace from the tops (if possible turn off the high section and store the phasetrace from the mid-speaker with 1/3 or 1/6 oct. smoothing).
After that turn on the subwoofer only, don´t change the dealy offset in Smaart and store the phasetrace from the sub.
Now you can turn on your top again and during live measurement with some noise you start to reduce the 3m delay offset until your actual phasetrace matches to the sub phasetrace in the acoustic-crossover region.
Hope that helps.

Michael

Brandon
May 16th, 2010, 12:28 PM
That is what I do, and typically you need to back the subs up to the tops. When its the other way around though, it becomes a longer process .....

Harry Brill Jr.
May 19th, 2010, 12:38 AM
My problem is when the subwoofers are well behind the tops. I do phase align things but its tough when you have subs that are 20' behind the top boxes because you cannot get a "zero" point to delay the tops to.

I currently delay the the tops so that they are "behind" the subs, then find the delay for my measurement mic, then delay the subs to the already delayed tops. After I do that I subtract the subwoofer delay from the tops delay and apply the difference to the tops. (I hope that makes sence) I am looking for a better faster way.

This is EXACTLY what I do and what I tell people in class to do. It's quick and effective. You could always add 50ms to the tops then once the subs are aligned. subtract the lower delay time from both.
Example: Mains 50ms, subs 40 ms, mains end up being 10 ms and subs are 0 ms. OR lets say mains are 50ms and subs are 65ms, mains end up being 0ms and subs end up being 15ms.