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Author Topic: Fixing a Bad Installation  (Read 4157 times)

Rob Timmerman

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Re: Fixing a Bad Installation
« Reply #10 on: March 10, 2007, 07:07:15 pm »

Remember that the nominal coverage patterns are for the 6dB down points on the horns, and there is usually still some output beyond those points.  This can work to your advantage in some cases.

I'd be inclined to go with the 3-wide, rotated horn approach, aiming for the back of the room, and adding some lip-fill if possible and if needed.  You probably won't be missing more than the first couple of rows anyway.  Lip-fill can also help anchor the image to the stage when the cluster is almost overhead.

Another approach might be to contact EV, and see if you can substitute the horn from a Xi-1152A/94 into one of the boxes and use that box to cover the back of the room.  It looks like a drop-in retrofit, and shouldn't be that expensive.  Just some food for thought.
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Brad Weber

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Re: Fixing a Bad Installation
« Reply #11 on: March 11, 2007, 11:45:42 am »

Rob is absolutely correct about the nominal coverage being the -6dB points.  Along with that keep in mind that this is also only a nominal number and the actual pattern changes with frequency.  Based on the EV datasheets, the Xi-1152A/64 appears to actually be 60x40 only from about 4kHz and higher.  At 2kHz it looks more like 85x55, at 1kHz 90x60 and at 500Hz maybe 105x120 (yep, apparently the pattern flips from around 400-700Hz).  Looking at the directivity and response data, there also seems to be some rather significant issues in the vertical pattern right around the crossover point with the -6dB pattern jumping to 100x100 and lobing that causes some major drops in level from about 15 degrees to 30 degrees off axis.

Anyways, the point is that it isn't really a 60x40 speaker at all frequencies and one thing you may have to watch is the resulting levels on the stage for frequencies where the vertical coverage gets wider.  The front rows may get some direct sound from the live action and you may think about letting the level from the speakers drop down in the front rows in order to keep the levels on the stage down and then counting on the live reinforcement from the stage to offset that for the first few rows.

Another aspect to make sure you considered in your calculations is distance.  The front row is likely quite a bit closer to the speakers, so you may actually want the coverage down quite a bit at that point to offset the higher level from being closer.  It does get rather complex trying to envision the 3-D pattern and distance effects, which is why even quick direct coverage modeling can be so helpful as it does this math for you and then lets you see the predicted results a various frequencies quite quickly.
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Brad Weber
muse Audio Video
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