time allignment in serial crossover

Marcelinho · 1st July 2006, 10:58 AM

Can an all pass filter be embedded in a 6db serial crossover for time allignment porposes.

Any examples available?

kelticwizard · 1st July 2006, 11:23 AM

I have no idea.

But just for clarity's sake, are you talking about an active, (one amp per band), or passive, (one amp for whole audio range), filter?

Marcelinho · 1st July 2006, 11:44 AM

It's ment for a passive filter and one amp for the whole freq. range

skylar112 · 1st July 2006, 10:14 PM

if you have separates playing off one passive, then time alignment will effect both speakers the same. For example, if you have a pair of separates a 6.5"(165mm) speaker and 1"(24mm) tweeter both playing off the passive, and played thru each channel. So left channel two speaker, and right channel two speakers. You delay left side by 1mm then both speakers will be effected.

Dick West · 2nd July 2006, 02:19 AM

In a description of the serial crossover the first article I read in Audio (ca. 1978) by Neville Thiel stated that the first order serial circuit expects the acoustic centers of the drivers to be time aligned. Many approximate this time alignment by getting the voice coils of the two drivers aligned in the same vertical plane. Rather than using a stepped baffle many slant the baffle.

You can't use an all pass filter in a serial crossover

sqlkev · 2nd July 2006, 04:05 AM

In my TMM 2.5 way, I slanted the baffle about 7-10 degrees back. As measurements showed, I came very close to the tweeter and the mid time aligned with each other. The differences were a few milliseconds.

rabbitz · 2nd July 2006, 03:47 PM

Or you can use an inverted woofer layout on the baffle which cancels the downward polar tilt of the 1st order xo as this set up gives an upward polar tilt.

You need to work with the horizontal offset of the drivers and driver centres so it's about 15° from the midpoint of the driver's motor front plate.

Dick West · 2nd July 2006, 03:56 PM

rabbitz,

You need to work with the horizontal offset of the drivers and driver centres so it's about 15° from the midpoint of the driver's motor front plate.

Please explain the use of horizontal offset. Or, did you mean offset in the vertical plane. Thanks

rabbitz · 2nd July 2006, 04:16 PM

The angle is tan-1 × (Cd / Hd) where (Hd) horizontal offset is the horizontal distance between the drivers voice coil centres (midpoint of the frontplate on the driver motor) and (Cd) is the driver's vertical centres.

Just turn the pic upside down and you will see what I mean for the inverted approach.

Dick West · 2nd July 2006, 10:24 PM

I don't disagree with the tilt. But, horizontal follows the horizon left to right. Your diagram shows up and down relationships which to me is vertical. I need help in understanding why vertical tilt or lobing in the vertical axis is referred to as horizontal offset. I guess I would use different terminology to describe the difference in the distance of the acoustic centers to the target point (listener's ears).

But, to quote Dickason, "The exact location of the driver radiating center, or zero delay plane (ZDP), can be somewhat of a mystery."

Thanks for the clarity.

Cheers..........

1st July 2006, 10:58 AM	#1
Marcelinho diyAudio Member Join Date: Oct 2005	time allignment in serial crossover Can an all pass filter be embedded in a 6db serial crossover for time allignment porposes. Any examples available?

1st July 2006, 11:23 AM	#2
kelticwizard diyAudio Member Join Date: Sep 2001 Location: Connecticut, The Nutmeg State	I have no idea. But just for clarity's sake, are you talking about an active, (one amp per band), or passive, (one amp for whole audio range), filter? __________________ "A friend will help you move. A really good friend will help you move a body." -Anonymous

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1st July 2006, 11:44 AM	#3
Marcelinho diyAudio Member Join Date: Oct 2005	It's ment for a passive filter and one amp for the whole freq. range

1st July 2006, 10:14 PM	#4
skylar112 diyAudio Member Join Date: Jun 2006	if you have separates playing off one passive, then time alignment will effect both speakers the same. For example, if you have a pair of separates a 6.5"(165mm) speaker and 1"(24mm) tweeter both playing off the passive, and played thru each channel. So left channel two speaker, and right channel two speakers. You delay left side by 1mm then both speakers will be effected.

2nd July 2006, 02:19 AM	#5
Dick West diyAudio Member Join Date: Aug 2004 Location: Illinois	In a description of the serial crossover the first article I read in Audio (ca. 1978) by Neville Thiel stated that the first order serial circuit expects the acoustic centers of the drivers to be time aligned. Many approximate this time alignment by getting the voice coils of the two drivers aligned in the same vertical plane. Rather than using a stepped baffle many slant the baffle. You can't use an all pass filter in a serial crossover

2nd July 2006, 04:05 AM	#6
sqlkev diyAudio Member Join Date: Mar 2004 Location: 714	In my TMM 2.5 way, I slanted the baffle about 7-10 degrees back. As measurements showed, I came very close to the tweeter and the mid time aligned with each other. The differences were a few milliseconds.

2nd July 2006, 03:47 PM	#7
rabbitz diyAudio Member Join Date: Jul 2003 Location: Newcastle, Australia	Or you can use an inverted woofer layout on the baffle which cancels the downward polar tilt of the 1st order xo as this set up gives an upward polar tilt. You need to work with the horizontal offset of the drivers and driver centres so it's about 15° from the midpoint of the driver's motor front plate.

2nd July 2006, 03:56 PM	#8
Dick West diyAudio Member Join Date: Aug 2004 Location: Illinois	rabbitz, You need to work with the horizontal offset of the drivers and driver centres so it's about 15° from the midpoint of the driver's motor front plate. Please explain the use of horizontal offset. Or, did you mean offset in the vertical plane. Thanks

2nd July 2006, 10:24 PM	#10
Dick West diyAudio Member Join Date: Aug 2004 Location: Illinois	I don't disagree with the tilt. But, horizontal follows the horizon left to right. Your diagram shows up and down relationships which to me is vertical. I need help in understanding why vertical tilt or lobing in the vertical axis is referred to as horizontal offset. I guess I would use different terminology to describe the difference in the distance of the acoustic centers to the target point (listener's ears). But, to quote Dickason, "The exact location of the driver radiating center, or zero delay plane (ZDP), can be somewhat of a mystery." Thanks for the clarity. Cheers..........

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