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Morison View Drop Down
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Joined: 05 November 2004
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    Posted: 05 September 2005 at 10:17am

Hi all,

Has anyone found the 2.5mm Xmax on the SN15MB to be a problem? WinISD seems to think it'll be pushed well past that in a lot of likely box sizes/tunings. But, maybe it's efficient enough that you don't have to push it that hard?

Also, what do people think of the way Ciare spec Xmax, adding 1/4 of the top plate thickness to the normal calculation? Does the magnetic field really extend out from the gap strongly enough to be useful like that? Clearly, if it does, then lots of drivers (inc SN15MB ;-) that have apparently short Xmax's are going to be more useful than modelling suggests.

Cheers,

David.
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mobiele eenheid View Drop Down
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Points: 1568 		Post Options Post Options   Thanks (0) Thanks(0)   Quote mobiele eenheid Quote  Post ReplyReply Direct Link To This Post Posted: 05 September 2005 at 1:38pm

Quote Also, what do people think of the way Ciare spec Xmax

Ciare too?? The Ciare fitted in the Punisher btw. doesn't.

Beyma, B&C, RCF, 18sound, DAS, JBL, Precision devices, etc. etc. all use that newer calculation in most models. Normally not much credit for Eminence, but they don't. Some manufacturers use a gapheight of only 9 mm, here the BL-drop will be greater as with for instance 18sound that uses a gapheight of 15 mm and a Xmech that is 25 mm one-way to make it rather safe. Same goes for the SD-18. The SD-21 even has a 20 mm gapheight.

So it will be different from model to model. Most models have kinda proved themselves in practice already without people knowing the real deal.

Quote WinISD seems to think it'll be pushed well past that in a lot of likely box sizes/tunings

WinISD uses a sine-wave (+/- 3 dB) to predict cone excursion. But music isn't a sine-wave. Tekno, gabba, etc. will have more like 4-6 dB for the bass. Higher tones are generally in the range of 10-12 dB.

So reaching excursion theoretically with 125 Watts, for 150 hz and up can well mean 375 Watts in practice.



Edited by mobiele eenheid
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Timber_MG View Drop Down
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Points: 1454 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Timber_MG Quote  Post ReplyReply Direct Link To This Post Posted: 05 September 2005 at 1:50pm
Until you band-limit the range and all of a sudden you can find peaks of -3dB fs (which is a good guideline). As I understand it, WinISD calculates excursion from a sine-wave at 0dB fs.
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Morison View Drop Down
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Points: 20 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Morison Quote  Post ReplyReply Direct Link To This Post Posted: 06 September 2005 at 6:39am
Originally posted by mobiele eenheid mobiele eenheid wrote:

Ciare too?? The Ciare fitted in the Punisher btw. doesn't.

Beyma, B&C, RCF, 18sound, DAS, JBL, Precision devices, etc. etc. all use that newer calculation in most models.

Oops, think it was 18sound I was thinking of. Thanks for the heads up about the other manufacturers who do it though.

Quote WinISD uses a sine-wave (+/- 3 dB) to predict cone excursion. But music isn't a sine-wave. Tekno, gabba, etc. will have more like 4-6 dB for the bass. Higher tones are generally in the range of 10-12 dB.

So reaching excursion theoretically with 125 Watts, for 150 hz and up can well mean 375 Watts in practice.

WinISD will model rms or peak excursion, whichever you ask it to. I've been using peak cos that tells me where the absolute limit is. Thing is,  even if I end up putting lower average levels into the system, if it has a high dynamic range (I agree 10dB is a useful figure to work with) the peaks could still end up problematic.

Cheers,

David.
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