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Phase Alignment - Smaart

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Grubbah View Drop Down
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    Posted: 25 March 2016 at 8:03pm
I've been trying to phase align a mid cabinet to a low mid using the transfer function on Smaart. Got a couple of questions

Do I align the phase traces to the processor xover point (in this case 250Hz) or to the point these cross on magnitude? (which seems to be about 290Hz!)



Also is there a standard smoothing I should be using? 

Is there anything that looks particularly wrong? I was quite surprised how much more the box responds past the processors xover point! Could this be down to room reflection or cabinet resonance?

I positioned the reference mic about 10 feet away, mic positioned at a 45 degree angle.


Edited by Grubbah - 25 March 2016 at 8:05pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 25 March 2016 at 8:49pm
The acoustic crossover point should be where the two boxes -6dB points overlap, your filter choices will affect this and should be based around making that happen. Once you have that in place, you want the phase traces to overlap for a full octave either side of the acoustic crossover point for smooth summation. You may then end up with a small hump in response when you measure both channels running together, this can be EQ'd out on the input EQ of your processor to get it back to flat.

First point I'd mention though is that your measurement delay setting is way off, the traces should really be flat phase for at least one of the passbands. After that you save traces of each passband, and you want to delay the box with the gentler slope.

A slope down from left to right means the signal is behind in time compared to your reference signal, a slope up from left to right means it is ahead of time. If they both slope the same way, you want to delay the one with the gentler slope to match the steeper sloped response.

As a general rule I tend to use minimal smoothing, 1/48 or 1/24 at most, because I'd rather see the data for myself. I also tend to set the coherence blanking to 45%, anything below this and there's more noise than signal so the data is worthless.

Here's an example from when I aligned one of Stable Audio's midtops for DSR in Glasgow. This has no smoothing on phase and 1/48 on magnitude:


Edited by toastyghost - 25 March 2016 at 9:04pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Grubbah Quote  Post ReplyReply Direct Link To This Post Posted: 29 March 2016 at 8:02pm
Thanks Toasty, before I comment back and Im going to try my traces again etc so I can refer directly back
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shortrope Quote  Post ReplyReply Direct Link To This Post Posted: 29 March 2016 at 8:32pm
This is great!
Just what I've been reading up on to try and learn!!
More info on the delay setting would be invaluable, layman's sterns?
Sorry for the hijack.

Edited by Shortrope - 29 March 2016 at 8:38pm
My Tinnitus is coming along nicely!!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 29 March 2016 at 10:00pm
The delay setting will vary depending on measurement conditions - distance to source, source type, soundcard/interface, etc etc.

You can often use SMAART's auto finder when doing midtops but it's pretty useless on subs because of the lack of useful data when measuring subs (low SnR ratio) and the fact that EVERY sub is stretched across a very broad period of time in it's usable passband.

Your best bet for sub alignment is to start using tape measure or laser measure for subs, and then add on the processing delay of your soundcard, processor/LMS and if in use, mixing desk. Then tweak up or down using the manual controls until the trace looks reasonably flat - really it's a matter of setting something in the right ballpark and then sticking with it when you measure the other passbands so that the reference doesn't change.

When doing midtops I would also strongly recommend going outdoors and putting the cab on its back, firing up into the sky, and then dangle the measurement mic above it at a reasonable distance - much easier to avoid reflections from buildings that way.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shortrope Quote  Post ReplyReply Direct Link To This Post Posted: 29 March 2016 at 10:52pm
Thanks a mill Toasty!!
My Tinnitus is coming along nicely!!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Timo Beckman Quote  Post ReplyReply Direct Link To This Post Posted: 29 March 2016 at 11:29pm
I have some video's online regarding phase alignment if you're interested.
Some are measurement at the x-over output where you might find this one interesting:



There are a lot more video's at my blog or Vimeo and more is to come in the future when i'm done with my seminar measurement room

enjoy
The sound will be as good as the band play's
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tthorsten Quote  Post ReplyReply Direct Link To This Post Posted: 23 April 2016 at 8:50am
www.satlive.audio - SATlive from Thomas Neumann could help also - try it
www.tb-audio.de

LEVELchek www.levelcheck.de
SPL tracking

SATlive www.satlive.audio
best Measurementsoftware for Live People

DBlimits
www.dblimits.com

Isemcon EMX7510 measurment Microphon

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Abe The Babe Quote  Post ReplyReply Direct Link To This Post Posted: 28 April 2016 at 12:39pm
Hi Timo,

Your links are broken unfortunately.
There's a time and place for acoustical reflection.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cravings Quote  Post ReplyReply Direct Link To This Post Posted: 28 April 2016 at 12:45pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Abe The Babe Quote  Post ReplyReply Direct Link To This Post Posted: 28 April 2016 at 1:36pm
Don't we all.
There's a time and place for acoustical reflection.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tthorsten Quote  Post ReplyReply Direct Link To This Post Posted: 20 May 2016 at 2:53am
www.tb-audio.de

LEVELchek www.levelcheck.de
SPL tracking

SATlive www.satlive.audio
best Measurementsoftware for Live People

DBlimits
www.dblimits.com

Isemcon EMX7510 measurment Microphon

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