Group Delay in TL speaker design.

christophorus · 15th January 2004, 11:27 AM

Hi all,
I'm going to build TL speaker, but I wonder about Group Delay for this system.
I already asked it in the "Perfect TL with MJK mathcad graph?" thread, but it seems nobody answer it, so I open this new thread.
I read from this article:

http://www.adireaudio.com/tech_papers/sub_gd.htm

On ported enclosure, even with T/S optimum design, it gets around 4 times longer than closed box and it gets more longer when we tune the box lower than Fs.

How about in TL design? is it shorter same or longer than ported enclosure? or just ignore it?
Can we calculate it for TL design?
Is there any graph showing it in MJK mathcad?

thankyou.

Chris.

Timn8ter · 15th January 2004, 04:06 PM

I don't think it worth it to get overly concerned about group delay in a vented enclosure unless it's doing some very strange things. A vented enclosure will always have a larger group delay than a sealed enclosure, it's just the nature of the beast and a TL is still a vented enclosure. It's just tuned to 1/4 of Fs. That doesn't mean it's going to sound bad. In a correctly built enclosure the GD occurs at an undetectable level. The corresponding graph in Martin's worksheet is the impulse response graph. As long as your line is resonably flat after the pulse you should be ok. This is IMHO of course.

christophorus · 18th January 2004, 10:53 AM

Hi Tim,
thank's for the reply,
Is Group Delay in TL box has the same behaviour as Ported box?
Or we can just ignore it?

I used MJK mathcad to calculate TL box, all the graphs looks OK and it came up with Vb 4x than optimal ported box calculated with WinISD.
Then I looked at Group Delay in WinISD, the GD was over the top of the graph! It was above 45ms I guess, since the peak was cut off.
Is it still OK?

Chris.

15th January 2004, 11:27 AM	#1
christophorus diyAudio Member Join Date: Dec 2003	Group Delay in TL speaker design. Hi all, I'm going to build TL speaker, but I wonder about Group Delay for this system. I already asked it in the "Perfect TL with MJK mathcad graph?" thread, but it seems nobody answer it, so I open this new thread. I read from this article: http://www.adireaudio.com/tech_papers/sub_gd.htm On ported enclosure, even with T/S optimum design, it gets around 4 times longer than closed box and it gets more longer when we tune the box lower than Fs. How about in TL design? is it shorter same or longer than ported enclosure? or just ignore it? Can we calculate it for TL design? Is there any graph showing it in MJK mathcad? thankyou. Chris.

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15th January 2004, 04:06 PM	#2
Timn8ter diyAudio Member Join Date: Jul 2003 Location: Seattle, WA	I don't think it worth it to get overly concerned about group delay in a vented enclosure unless it's doing some very strange things. A vented enclosure will always have a larger group delay than a sealed enclosure, it's just the nature of the beast and a TL is still a vented enclosure. It's just tuned to 1/4 of Fs. That doesn't mean it's going to sound bad. In a correctly built enclosure the GD occurs at an undetectable level. The corresponding graph in Martin's worksheet is the impulse response graph. As long as your line is resonably flat after the pulse you should be ok. This is IMHO of course.

18th January 2004, 10:53 AM	#3
christophorus diyAudio Member Join Date: Dec 2003	Hi Tim, thank's for the reply, Is Group Delay in TL box has the same behaviour as Ported box? Or we can just ignore it? I used MJK mathcad to calculate TL box, all the graphs looks OK and it came up with Vb 4x than optimal ported box calculated with WinISD. Then I looked at Group Delay in WinISD, the GD was over the top of the graph! It was above 45ms I guess, since the peak was cut off. Is it still OK? Chris.

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