time alignment?

flaevor · 27th February 2006, 10:23 AM

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.

sreten · 27th February 2006, 10:58 AM

Hi,

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.

/sreten.

flaevor · 27th February 2006, 01:11 PM

Thanks for the reply. Do your know where I could read up on this a little more.

Vikash · 27th February 2006, 01:30 PM

There are some pages in the Loudspeaker Design Cookbook IIRC.

mazurek · 27th February 2006, 02:54 PM

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.

banana · 27th February 2006, 04:10 PM

Visit JohnK's old site.

http://www.geocities.com/kreskovs/TimeAligned1.html

PeteMcK · 28th February 2006, 09:25 PM

http://sound.westhost.com/ptd.htm

Virtalahde · 18th August 2006, 01:51 PM

Bump

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.

27th February 2006, 10:23 AM	#1
flaevor diyAudio Member Join Date: Jan 2005 Location: Germany	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.

27th February 2006, 01:30 PM	#4
Vikash diyAudio Moderator Emeritus Join Date: May 2003 Location: UK	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.)

28th February 2006, 09:25 PM	#7
PeteMcK diyAudio Member Join Date: Feb 2002 Location: Sydney	Rod Elliot's take... http://sound.westhost.com/ptd.htm

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
DIY Time Alignment.	clipto333	Car Audio	32	4th January 2011 06:48 AM
Time Alignment Dilemna	the apprentice	Multi-Way	4	5th November 2007 05:49 PM
Time alignment circuit?	Bad silver	Car Audio	4	30th January 2007 09:00 AM
is doing time alignment now a waste of time?	Beggar	Multi-Way	9	28th July 2003 06:45 AM


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

27th February 2006, 10:58 AM	#2
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, 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. /sreten.

27th February 2006, 01:11 PM	#3
flaevor diyAudio Member Join Date: Jan 2005 Location: Germany	Thanks for the reply. Do your know where I could read up on this a little more.

27th February 2006, 02:54 PM	#5
mazurek diyAudio Member Join Date: Aug 2005	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.

27th February 2006, 04:10 PM	#6
banana diyAudio Member Join Date: Feb 2003 Location: Hong Kong	Visit JohnK's old site. http://www.geocities.com/kreskovs/TimeAligned1.html

18th August 2006, 01:51 PM	#8
Virtalahde diyAudio Member Join Date: Jan 2006 Location: Kuhmoinen, Finland	Bump 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.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read