SpeakerWorkShop and drivers offsets

crazyhub · 2nd November 2007, 04:20 PM

Hi all,

If I enter:

Bass: -35mm
Mid: -15mm
Tweeter: 0mm

instead of:

Bass: -40mm
Mid: -20mm
Tweeter: -5mm

Thus same relative offsets between all the drivers BUT the phase tracking is very different from 5 to 20Khz.

Do you know WHY?

Thanks.

Jay_WJ · 3rd November 2007, 02:47 AM

Relative phase (degree difference between drivers) should not be different. The resulting SPL sum should not be different, either. By using extra -5mm offset (i.e., drivers farther from mic), acoustic phase of each driver will have a faster turn. That's why they look different. Fast phase turns make it harder to look at phase tracking.

crazyhub · 3rd November 2007, 01:21 PM

Jay wrote:

Quote:

Relative phase (degree difference between drivers) should not be different.
*** exact

The resulting SPL sum should not be different, either.
*** exact

By using extra -5mm offset (i.e., drivers farther from mic), acoustic phase of each driver will have a faster turn. That's why they look different. Fast phase turns make it harder to look at phase tracking.
*** OK, what I understand is that the total frequency phase remains almost identical but because of the shorter wave-lenghts in the high frequencies the total phase goes far away from that of the tweeter. Thus it seems that SWshop does take into account not only the relative offset of the drivers but also the relative position of each driver to a virtual fixed position of the microphone. Am I right?

Ron E · 3rd November 2007, 03:47 PM

Without pictures, I would assume that the issue is "excess phase"

crazyhub · 3rd November 2007, 05:05 PM

Ron e wrote:

Quote:

Without pictures, I would assume that the issue is "excess phase"

I don't know how to copy the graph from SWshop.

Ron E · 3rd November 2007, 09:17 PM

With a PC, you just hold down Ctrl and press the Print Screen" button.
Then you open "Paint" and select edit\paste from the menu, or just press Ctrl+V.

If you have some other computer, do a search on "print screen" or "screen capture".

crazyhub · 3rd November 2007, 11:22 PM

Thanks Ron for my computer education! 50 years old and 47years without computer doesn't help

Here are the two pictures

Ron E · 4th November 2007, 01:27 AM

Just excess phase. The extra 5mm of time of flight causes the high frequencies to be delayed for a greater proportion of their wavelength, which is why there is little to no effect at low frequencies and a larger effect as frequency increases. As simple as that. If there were inter-driver "phase tracking" problems, the frequency response would change.

Jay_WJ · 4th November 2007, 01:34 AM

Ron's explanation is correct, and your understanding also seems correct. SW adds/subtracts delay to each driver's acoustic phase across frequencies before computing the SPL sum of drivers. When the offset is set to 0, it uses the phase in each driver's FRD file as is.

-jAy

crazyhub · 4th November 2007, 07:49 AM

Jay and Ron,

Thank you for your helpfull explanations.

2nd November 2007, 04:20 PM	#1
crazyhub diyAudio Member Join Date: Nov 2005 Location: alsace	SpeakerWorkShop and drivers offsets Hi all, If I enter: Bass: -35mm Mid: -15mm Tweeter: 0mm instead of: Bass: -40mm Mid: -20mm Tweeter: -5mm Thus same relative offsets between all the drivers BUT the phase tracking is very different from 5 to 20Khz. Do you know WHY? Thanks. __________________ crazyhub

3rd November 2007, 03:47 PM	#4
Ron E diyAudio Member Join Date: Jun 2002 Location: USA, MN	Without pictures, I would assume that the issue is "excess phase" __________________ Our species needs, and deserves, a citizenry with minds wide awake and a basic understanding of how the world works. --Carl Sagan Science is a way of thinking much more than it is a body of knowledge. --Carl Sagan

3rd November 2007, 09:17 PM	#6
Ron E diyAudio Member Join Date: Jun 2002 Location: USA, MN	With a PC, you just hold down Ctrl and press the Print Screen" button. Then you open "Paint" and select edit\paste from the menu, or just press Ctrl+V. If you have some other computer, do a search on "print screen" or "screen capture". __________________ Our species needs, and deserves, a citizenry with minds wide awake and a basic understanding of how the world works. --Carl Sagan Science is a way of thinking much more than it is a body of knowledge. --Carl Sagan

3rd November 2007, 11:22 PM	#7
crazyhub diyAudio Member Join Date: Nov 2005 Location: alsace	Thanks Ron for my computer education! 50 years old and 47years without computer doesn't help Here are the two pictures __________________ crazyhub

4th November 2007, 01:27 AM	#8
Ron E diyAudio Member Join Date: Jun 2002 Location: USA, MN	Just excess phase. The extra 5mm of time of flight causes the high frequencies to be delayed for a greater proportion of their wavelength, which is why there is little to no effect at low frequencies and a larger effect as frequency increases. As simple as that. If there were inter-driver "phase tracking" problems, the frequency response would change. __________________ Our species needs, and deserves, a citizenry with minds wide awake and a basic understanding of how the world works. --Carl Sagan Science is a way of thinking much more than it is a body of knowledge. --Carl Sagan


	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

3rd November 2007, 02:47 AM	#2
Jay_WJ diyAudio Member Join Date: Mar 2006 Location: Indiana	Relative phase (degree difference between drivers) should not be different. The resulting SPL sum should not be different, either. By using extra -5mm offset (i.e., drivers farther from mic), acoustic phase of each driver will have a faster turn. That's why they look different. Fast phase turns make it harder to look at phase tracking.

4th November 2007, 01:34 AM	#9
Jay_WJ diyAudio Member Join Date: Mar 2006 Location: Indiana	Ron's explanation is correct, and your understanding also seems correct. SW adds/subtracts delay to each driver's acoustic phase across frequencies before computing the SPL sum of drivers. When the offset is set to 0, it uses the phase in each driver's FRD file as is. -jAy

4th November 2007, 07:49 AM	#10
crazyhub diyAudio Member Join Date: Nov 2005 Location: alsace	Jay and Ron, Thank you for your helpfull explanations. __________________ crazyhub

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

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
FFT size in SpeakerWorkshop	jm_kzo	Multi-Way	2	9th July 2008 07:48 AM
phase compensation due to driver offsets	DcibeL	Multi-Way	51	1st June 2008 06:35 PM
Speakerworkshop question	kro5998	Multi-Way	2	25th June 2006 06:18 PM
SpeakerWorkshop again	Dave Jones	Multi-Way	19	17th June 2004 05:34 PM

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