P audio xmax

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   I may be wrong but I recall a post on here saying p audio measure their Xmas in an odd way so if they say 4mm it is more like 5 or 6, does anyone recall this. Cheers.

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concept-10 Members Profile Send Private Message Find Members Posts Add to Buddy List Young Croc Joined: 17 May 2016 Status: Offline Points: 1293	Post Options Post Reply Quote concept-10 Report Post Thanks(0) Quote Reply Topic: P audio xmax Posted: 14 May 2018 at 10:10am
	I may be wrong but I recall a post on here saying p audio measure their Xmas in an odd way so if they say 4mm it is more like 5 or 6, does anyone recall this. Cheers.

citizensc Members Profile Send Private Message Find Members Posts Add to Buddy List Young Croc Joined: 16 October 2015 Location: Perth,Australia Status: Offline Points: 532	Post Options Post Reply Quote citizensc Report Post Thanks(0) Quote Reply Posted: 14 May 2018 at 11:07am
	Old thread with some rare Rog posts! Not sure if the information is still up to date. https://forum.speakerplans.com/xmax-on-p-audio-sd-drivers_topic3747.html

concept-10 Members Profile Send Private Message Find Members Posts Add to Buddy List Young Croc Joined: 17 May 2016 Status: Offline Points: 1293	Post Options Post Reply Quote concept-10 Report Post Thanks(0) Quote Reply Posted: 14 May 2018 at 11:17am
	that's the one, cheers bud

Hemisphere Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 21 April 2008 Status: Offline Points: 2272	Post Options Post Reply Quote Hemisphere Report Post Thanks(0) Quote Reply Posted: 14 May 2018 at 11:29am
	P Audio, like Celestion, BMS and some other manufacturers, don't apply what's become an industry standard addition of [magnetic gap depth /4] to the xmax rating, but you can do it yourself from the spec sheet. FaitalPro (and possibly some other manufacturers - the method is usually stated somewhere in the footnotes) prefer to add [magnetic gap depth /3]. Their drivers all have low SD as well (1134cm2 for an 18" driver is typical from Faital while ~1200 is the norm). Shaving corners to make their products look better/increase profits etc, which they get away with as the quality despite the corner cutting and inflation is still good (and maybe some designs call for a 17.5" driver anyway ) This leads to some funny looking driver specs, so you can see why it's not a popular way of showing it - there's one Celestion mid woofer, 12", with "1mm" xmax but it works out at something like 5mm. Also a P Audio 18" with '2mm' xmax. Edited by Hemisphere - 14 May 2018 at 11:30am
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Andy Kos Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 15 May 2007 Location: Southampton Status: Offline Points: 3038	Post Options Post Reply Quote Andy Kos Report Post Thanks(0) Quote Reply Posted: 14 May 2018 at 10:11pm
	P-Audio post the true 'mathematical' xmax, which is the voice coil overhang. Most other manufucturers (as mentioned above) just add a nominal extra percentage of the amount and bump up the Xmax. It isnt complete fiction though, as the magnetic field doesnt just stop outside the gap, it's there, just weaker. A few manufacturers are starting to use Klippel Analysis to measure 'true' Xmax, so rather than an arbitrary extra few mm added on, they are actually measuring where the magnetic field reduction outside the gap actually has a noticeable effect. Im pretty sure Oberton did this with the 18XB1600 If in any doubt, have a read: http://www.speakerwizard.co.uk/driver-ts-parameters-xmax/ Edited by Andy Kos - 14 May 2018 at 10:18pm
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