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Author Topic: Smaart subwoofer alignment  (Read 5483 times)

Ivan Beaver

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Re: Smaart subwoofer alignment
« Reply #20 on: June 05, 2017, 05:58:32 pm »

Regarding subwoofer placement in small venues. Instead of doing trial and error, reverse the roles.

Put the sub at the actual listening position where you want it to sound good, turn it on and start listening at candidate positions where the sub could end up.

The spot where it sound best or the the way you like, is where you'll put it. It's a matter of simple reciprocity.


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That is one of the best ways to do sub placement in a home theater.
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Ivan Beaver
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Peter Morris

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Re: Smaart subwoofer alignment
« Reply #21 on: June 14, 2017, 08:27:53 am »

The interesting thing that nobody has discussed is that he uses two different methods to phase align the subs Ė firstly he polarity flips the subs with no delay, then he delays the subs 8ms but without a polarity flip.  In both case the phase traces overlay each other - but itís not the same :-)
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Mark Wilkinson

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Re: Smaart subwoofer alignment
« Reply #22 on: June 14, 2017, 12:51:28 pm »

The interesting thing that nobody has discussed is that he uses two different methods to phase align the subs Ė firstly he polarity flips the subs with no delay, then he delays the subs 8ms but without a polarity flip.  In both case the phase traces overlay each other - but itís not the same :-)

Yes, and pls correct me if I'm wrong.... he's added 180 degrees of phase, a half a wrap, at 63Hz ( 8ms half wave). And relative phase additions to surrounding freqs (ie 360 deg @ 125Hz, 90 @ 31Hz)
Impulse of this phase-rotation-delay method vs a polarity swap will show it loud and clear, IME
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Peter Morris

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Re: Smaart subwoofer alignment
« Reply #23 on: June 14, 2017, 10:59:18 pm »

Yes, and pls correct me if I'm wrong.... he's added 180 degrees of phase, a half a wrap, at 63Hz ( 8ms half wave). And relative phase additions to surrounding freqs (ie 360 deg @ 125Hz, 90 @ 31Hz)
Impulse of this phase-rotation-delay method vs a polarity swap will show it loud and clear, IME

Exactly, what I try to do is ensure that all the separate pass bands have +ve impulses and then align.

I would be very interested in what others think about this polarity flip.

Itís also important to remember that we tend to run the subs with a little extra gain/SPL relative to the mids, so you could say the actual crossover is noticeable higher than the implied electronic crossover point, so it is especially important that the phase traces are aligned above the crossover otherwise you can end up with the subs cancelling some of the low mids.

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Doug Fowler

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Re: Smaart subwoofer alignment
« Reply #24 on: July 23, 2017, 03:12:58 pm »

Thanks Doug,

If I get what you're saying...the basic idea is to match group delays at crossover frequency for the coarse adjustment...
And that this should get rid of phase wraps...and then allow fine tuning via phase overlay.

Just trying to make sure it sinks in....

Mark

Sorry for the late reply, but yes that's the idea.
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Mark Wilkinson

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Re: Smaart subwoofer alignment
« Reply #25 on: July 23, 2017, 09:26:35 pm »

Exactly, what I try to do is ensure that all the separate pass bands have +ve impulses and then align.

I would be very interested in what others think about this polarity flip.

Itís also important to remember that we tend to run the subs with a little extra gain/SPL relative to the mids, so you could say the actual crossover is noticeable higher than the implied electronic crossover point, so it is especially important that the phase traces are aligned above the crossover otherwise you can end up with the subs cancelling some of the low mids.

Hi Peter,  I've been doing the same...trying to ensure the separate pass bands have +ve impulses and then align.

But what are your thoughts on  boxes like your DIY's, where the mid section port impulses arrive before the mid horn impulses......?
I've been tuning to the horn impulses so far...
I guess the tapped horn folks have this dilemma too...?

As far as subs running hotter and moving xover up, that's why I love lotsa FIR with 0 degree phase, cause then who cares what freq xover is...:)
damn shame the latency doesn't work for live :(
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Merlijn van Veen

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Smaart subwoofer alignment
« Reply #26 on: July 27, 2017, 04:29:37 am »

Maybe this video can help?

Sincerely,

Merlijn


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Timo Beckman

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Re: Smaart subwoofer alignment
« Reply #27 on: August 27, 2017, 05:01:06 am »

I'm currently researching the process of time aligning subwoofers to mains using Smaart, and came across the video linked bellow. I'm curious what those of you well versed in the subject think about his method, particularly his choice to not "delay locate". I assume he is referring to the process of delaying the reference signal to the mic signal? Please correct me if I'm wrong.

https://www.youtube.com/watch?v=j6Z_sIDrs8A&t=11s


Maybe this helps a little..... I did a screen capture on aligning a sub to mains but as said by many: using the delay locator makes thins easier to read. However setting the delay finder to another value can help. From 07.30 min in to the capture I'm using a trick Bob (606) McCarthy showed a couple of years ago during a SIM3 thing.

https://timobeckmangeluid.wordpress.com/2017/08/25/sub-top-alignment-delay-only/

By adding delay to the delay finder you can get the phase trace to go horizontal in for instance the x-over area. It can help a bit if you're in a concrete disaster area with no acoustic treatment like many of the so called concert venue's......
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