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time alignment?
time alignment?
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Old 27th February 2006, 09:23 AM   #1
flaevor is offline flaevor  United States
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Default time alignment?

Can anybody point me in the direction of some good information regarding time alignment of chassis including measured results and how to go about it properly.
I have seen some designs that aimed at time aligning the drivers, but it seemed to me that they were only successful at the cost of what i would expect to be strange baffle step phenomena and/or the listener being off axis from at least one of the drivers.

Therefore I need more info to better understand the trade-offs.
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Old 27th February 2006, 09:58 AM   #2
sreten is offline sreten  United Kingdom
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a very complex issue.

For higher order c/o slopes time alignment is not an issue.

The best you can do is phase alignment at c/o.

Time alignment is a theorectical issue for 1st order
c/o's and near transient perfect 2nd order c/o's.

I say theorectical because the c/o's must be acoustic, not electrical, for
absolute time alignment to be considered a constructively valid issue.

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Old 27th February 2006, 12:11 PM   #3
flaevor is offline flaevor  United States
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Thanks for the reply. Do your know where I could read up on this a little more.
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Old 27th February 2006, 12:30 PM   #4
Vikash is offline Vikash  United Kingdom
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There are some pages in the Loudspeaker Design Cookbook IIRC.
"The human mind is so constituted that it colours with its own previous conceptions any new notion that presents itself for acceptance." - J. Wilhelm. (But I still think mine sounds better than yours.)
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Old 27th February 2006, 01:54 PM   #5
mazurek is offline mazurek  United States
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You can measure time alignment using digital delay, vary the delay of the tweeter mounted on the same baffle as the woofer. When an SPL meter reads highest, with a test tone at the crossover frequency, your drivers are in phase at the crossover frequency. Some people put the tweeter wired out of phase and measure for the lowest spl.

Generally your solutions to this problem are going to be sloped/displaced baffles, allpass filters, or digital delays. Some opinions on this subject are present at www.linkwitzlabs.com, sound.westhost.com.
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Old 27th February 2006, 03:10 PM   #6
banana is offline banana  Hong Kong
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Visit JohnK's old site.

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Old 28th February 2006, 08:25 PM   #7
PeteMcK is offline PeteMcK
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Default Rod Elliot's take...

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Old 18th August 2006, 12:51 PM   #8
Virtalahde is offline Virtalahde  Finland
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I've been reading about time alignment a lot lately, and somehow I have not got a clear picture of using time alignment with LR12 or LR24 crossovers. Sreten said time alignment is an issue only with lower order crossovers though.

One thing I think I've got right is that when using LR24 crossover (active in my case, and assuming we have the healthy 2 octaves response for the drivers below and above the crossover frequency) is that it brings in its own delay too (360 degrees of phase shift) and should be taken into account when physically aligning drivers. Am I correct with this?

The Rod Elliott article is good reading otherwise. Maybe I just didn't get it all.
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