ohms changed???

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   So I was at a gig the other night with the sound system and noticed somethin very strange. I'm using vz5000 on bass down to 2.66ohm a side (pd1850) 3cabs. Half way through the night one channel of the vz5000 started hard clipping and he other Chanel was fine. So I turned it down on that side and left it for 10 mins then turned gain back up and it ran fine for the rest of the night drivers still intact.  Very confusing. So here's what leads me to my next question. Is it possible that one of the pd1850  coil got hot and ohms changed? Changing the load on the amp? Then when I turned it down for some breathing space it cooled down and returned to 8ohms? Then ran fine. . Otherwise my amp may have thrown a wobbly. Is it possible for a driver to change ohms and go back to normal? It's the only thing I can think off as vz5000 been checked and drivers fine all reading around 8 ohms. Any advice welcome. Thanks by the way. The crown is limited  so it never hits clip. 

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msoundsystem Members Profile Send Private Message Find Members Posts Add to Buddy List Young Croc Joined: 10 November 2011 Location: wales Status: Offline Points: 625	Post Options Post Reply Quote msoundsystem Report Post Thanks(0) Quote Reply Topic: ohms changed??? Posted: 24 November 2016 at 5:39pm
	So I was at a gig the other night with the sound system and noticed somethin very strange. I'm using vz5000 on bass down to 2.66ohm a side (pd1850) 3cabs. Half way through the night one channel of the vz5000 started hard clipping and he other Chanel was fine. So I turned it down on that side and left it for 10 mins then turned gain back up and it ran fine for the rest of the night drivers still intact. Very confusing. So here's what leads me to my next question. Is it possible that one of the pd1850 coil got hot and ohms changed? Changing the load on the amp? Then when I turned it down for some breathing space it cooled down and returned to 8ohms? Then ran fine. . Otherwise my amp may have thrown a wobbly. Is it possible for a driver to change ohms and go back to normal? It's the only thing I can think off as vz5000 been checked and drivers fine all reading around 8 ohms. Any advice welcome. Thanks by the way. The crown is limited so it never hits clip.

kedwardsleisure Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 4947	Post Options Post Reply Quote kedwardsleisure Report Post Thanks(0) Quote Reply Posted: 24 November 2016 at 6:38pm
	When you say hard clip I'm guessing you mean the IOC light was on bright? The load characteristic shouldn't cause that, the light is saying the waveform between input and output is significantly different (ie distorted). If there's too much load on the amp such as an impedance that's too low the i-load/lim light should change from green to red, telling you the amp is current-limiting itself. Continued driving into current limit will trigger the ODEP to start limiting the gain down to prevent distortion or over-running the components. A driver's descent from 8 ohms down to something capable of overloading a macrotech will be a one-way trip for the driver. Edited by kedwardsleisure - 24 November 2016 at 6:40pm
	Kevin North Staffordshire

toastyghost Members Profile Send Private Message Find Members Posts Add to Buddy List The 10,000 Points Club Joined: 09 January 2007 Location: Manchester Status: Offline Points: 10919	Post Options Post Reply Quote toastyghost Report Post Thanks(0) Quote Reply Posted: 24 November 2016 at 6:42pm
	All drivers in all boxes change impedance with frequency, and change again at all frequencies as thermal compression sets in.

VentureSound Members Profile Send Private Message Find Members Posts Add to Buddy List Young Croc Joined: 18 October 2009 Location: London N20 Status: Offline Points: 950	Post Options Post Reply Quote VentureSound Report Post Thanks(0) Quote Reply Posted: 24 November 2016 at 6:59pm
	Could just be that the amp was getting too hot, have you cleaned it out regularly?

DMorison Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 14 March 2007 Location: Aberdeen Status: Offline Points: 1649	Post Options Post Reply Quote DMorison Report Post Thanks(0) Quote Reply Posted: 25 November 2016 at 3:57pm
	As Toasty says, the drivers will change impedance as you apply power for any length of time, however (in case you didn't already know) that change is an increase. It should therefore result in an easier load for the amp, and not cause your symptoms.