Mr. Linkwitz's max_spl.xls

amo · 14th December 2003, 10:29 PM

Hi-

This is a question for those familiar with Mr. Linkwitz's work and website. I have been using his max_spl.xls spreadsheet to calculate the maximum spl availabe from a driver at a frequency in sealed/dipole configuration, but I am not sure how to calculate the "D" or acustic path length difference parameter. Mr Linkwitz does a great job explaining many things, but a few things he just assumes you already know... So when we look at a regular rectangular baffle with a driver in the middle, would the D parameter be the length from the center of the driver to the edge of the baffle, or from the edge of the driver to the edge of the baffle. Tiny variations in this parameter make a HUGE difference in the outcome, so this is vital. Thank you for your help!!!!

Davey · 15th December 2003, 01:59 AM

This explains it very well:

http://www.linkwitzlab.com/models.htm#B

Davey.

amo · 15th December 2003, 03:26 AM

Yes I have seen this. Based on the picture on that page, D is measured from the center of the driver to the edge of the baffle. And for a large driver, say a 16 inch, this is considerable. So much so that (based on max_spl.xls) one can get very respectible bass responce with little eq and tiny baffle (aside from the fact that the driver it self is large). If one can extend the baffle just a little further, no eq is required. This almost seems too good to be true, and I wanted to verify... This after I saw open baffle designs featureing a small driver on a HUGE baffle...

sreten · 15th December 2003, 11:27 AM

Without wading through the maths if its a small driver on a large
baffle then driver size is irrelevant and the model does not need
to consider driver size.
For a small driver the path lengths to the edge will be similar, and
the centre is a good approximation of the mean path length.

But if the driver size is not considered it is not safe to apply the
same model to a large driver on a very small baffle, the above
reasoning will not apply to the mean path length.

I can't see Mr. L analysis a single open driver, for the compound
driver case the parameter is d1 which he goes on to show for
equivalence 2d1 should equal D.

I'd suggest for the single open driver case either 2d1=D or root2*d1=D.
I don't think d1 will be equivalent to D.

Really you need an analysis that considers both d1 (driver radius)
and D (1/2 mean diameter of the baffle.)

sreten.

14th December 2003, 10:29 PM	#1
amo diyAudio Member Join Date: Apr 2003 Location: Texas - USA	Mr. Linkwitz's max_spl.xls Hi- This is a question for those familiar with Mr. Linkwitz's work and website. I have been using his max_spl.xls spreadsheet to calculate the maximum spl availabe from a driver at a frequency in sealed/dipole configuration, but I am not sure how to calculate the "D" or acustic path length difference parameter. Mr Linkwitz does a great job explaining many things, but a few things he just assumes you already know... So when we look at a regular rectangular baffle with a driver in the middle, would the D parameter be the length from the center of the driver to the edge of the baffle, or from the edge of the driver to the edge of the baffle. Tiny variations in this parameter make a HUGE difference in the outcome, so this is vital. Thank you for your help!!!!

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15th December 2003, 01:59 AM	#2
Davey diyAudio Member Join Date: Dec 2001 Location: Bremerton, WA.	This explains it very well: http://www.linkwitzlab.com/models.htm#B Davey.

15th December 2003, 03:26 AM	#3
amo diyAudio Member Join Date: Apr 2003 Location: Texas - USA	Yes I have seen this. Based on the picture on that page, D is measured from the center of the driver to the edge of the baffle. And for a large driver, say a 16 inch, this is considerable. So much so that (based on max_spl.xls) one can get very respectible bass responce with little eq and tiny baffle (aside from the fact that the driver it self is large). If one can extend the baffle just a little further, no eq is required. This almost seems too good to be true, and I wanted to verify... This after I saw open baffle designs featureing a small driver on a HUGE baffle...

15th December 2003, 11:27 AM	#4
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Without wading through the maths if its a small driver on a large baffle then driver size is irrelevant and the model does not need to consider driver size. For a small driver the path lengths to the edge will be similar, and the centre is a good approximation of the mean path length. But if the driver size is not considered it is not safe to apply the same model to a large driver on a very small baffle, the above reasoning will not apply to the mean path length. I can't see Mr. L analysis a single open driver, for the compound driver case the parameter is d1 which he goes on to show for equivalence 2d1 should equal D. I'd suggest for the single open driver case either 2d1=D or root2*d1=D. I don't think d1 will be equivalent to D. Really you need an analysis that considers both d1 (driver radius) and D (1/2 mean diameter of the baffle.) sreten.

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