Rational Acoustics



RayS1
April 28th, 2019, 11:53 AM
One of the venues I regularly play in has discovered recent or not so recent issues with their Main M1D rigs used as orchestra support for ballet /operas..

Right side was found to have 5 boxes out of the 11 with defective/dead tweeters, I don't know where these are located in the hang, and i don't know how many inside each box were found to be defective.Left side was ok!...these boxes feature 3 x tweeters per box along with 2 x 5" woofers crossovers are at 1900 hz....obviously the system didn't sound as pristine as it once did and is scheduled for replacement with a meyer CAL ...but my question is, would it not have been quite evident that that side of the PA was missing highs? regardless of where the missing tweeters were located ? or would it just be a few dbs low over the high spectrum (less than -3db as it still had its tweeters in the other 6 boxes??) or. ??? what if they were the top 5 in the array, wouldn't that be evident on the orchestra level for ex.?

And what could cause this ? again I don't know which processor output was driving which set of M1Ds ...

All I was told was that the 2 sides sounded different enough (nothing drastic though) to warrant further investigation, and that eventually each box (they're all on separate breakers ) was sent signal and compared to a known good box.....

The bad ones were sent out for repair and replaced with spares they had on hand.....

Thanks



Ray

gluis
May 23rd, 2019, 04:16 PM
One of the venues I regularly play in has discovered recent or not so recent issues with their Main M1D rigs used as orchestra support for ballet /operas..

Right side was found to have 5 boxes out of the 11 with defective/dead tweeters, I don't know where these are located in the hang, and i don't know how many inside each box were found to be defective.Left side was ok!...these boxes feature 3 x tweeters per box along with 2 x 5" woofers crossovers are at 1900 hz....obviously the system didn't sound as pristine as it once did and is scheduled for replacement with a meyer CAL ...but my question is, would it not have been quite evident that that side of the PA was missing highs? regardless of where the missing tweeters were located ? or would it just be a few dbs low over the high spectrum (less than -3db as it still had its tweeters in the other 6 boxes??) or. ??? what if they were the top 5 in the array, wouldn't that be evident on the orchestra level for ex.?

And what could cause this ? again I don't know which processor output was driving which set of M1Ds ...

All I was told was that the 2 sides sounded different enough (nothing drastic though) to warrant further investigation, and that eventually each box (they're all on separate breakers ) was sent signal and compared to a known good box.....

The bad ones were sent out for repair and replaced with spares they had on hand.....

Thanks



Ray

Hi Ray,

Burned HF components within a line array will cause havoc with the vertical polar of the system, and the effect will be different depending on where those tweeters are positioned. But the general effect, specially in a closed space (as believe yours is) will be lower HF energy as it will also excite the reflections with less HF. In a free field situation, for example if all the top boxes had their HF burned, it will be only noted far away, but will make little or no effect on the front.

It might had been evident to somebody with knowledge and experience enough to have this happened to him in the past, but again, with a diffuse field, it will be hard to pinpoint where the problem comes from. the best way to find it in your scenario without tearing down the array would be to listen to each pair of boxes, one from left and one from right that correspond to the same place (firsts from bottom, second from bottom, etc) individually to find out which sounds different from the other. Of course if both are burned the same way that might be a problem LOL.

I hope this helps. GS