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Author Topic: Question about boxes and phase problems.  (Read 700 times)

Paul Lea

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Question about boxes and phase problems.
« on: August 10, 2009, 04:24:06 pm »

I have been part of this community for a little over 2 years and have seen different homebrew boxes, some seem better than others.

The one that always gets me is the RatTrap by Dave Rat. Cool system and I am sure that Dave has got this thing to just sing.

My question is this, how does he get around the HF phase problems with the boxes so close and so minimally splayed in both axis? I thought at first it was because he used narrow dispersion horns but in one of the setup examples, it is hung almost like a line array using a single column of speakers. That seemed to nix the narrow horizontal pattern control unless there are different boxes in different configs.

Is he using intensive processing to make it all come together?

Anyway, that system has always had a cool look to me but I never understood how he managed to make it all play together nicely.

Thanks for reading my ramble. Look forward to any answers.
Paul Lea

Owner - Midwest Sound and Production, LLC

Jeff Babcock

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Re: Question about boxes and phase problems.
« Reply #1 on: August 10, 2009, 05:04:10 pm »

While I have never heard the RatTrap, it is subject of course to the laws of physics.  With the box essentially being all front loaded, the individual boxes will not likely have much pattern control in the low mids (although the 2 horns appear to be quite focused which would help a lot for mids and HF).  Clearly there has been an effort made to account for the clustered setup.

Just because there is some interaction going on doesn't necessarily mean terrible sound.... given the clients who have used this system and been happy with the results, I'm sure it can sound very good.  But if it really were the be-all-end-all of systems, Dave wouldn't be using L'Acoustics products for his "A" clients.

In fact here is what Dave says about this (from Mix Mag):


I cannot imagine anyone designing a full-blown P.A. system that can compete with the current top manufacturers in today's market. The days of building a world-class, competitive main P.A. speaker system without a full engineering group, lots of expensive test gear and a hefty budget are over.

Greg Cameron

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Re: Question about boxes and phase problems.
« Reply #2 on: August 10, 2009, 05:19:38 pm »

There is definitely some combing going on box to box and how much depends on splay. Within a single box, the driver coupling is very good due to the tight placement in general, though there is some negative interaction between the 10" drivers due to the spacing (they go from 250 to 800Hz and are a little over a foot apart). Keep in mind these boxes were designed over 10 years ago. As for processing, there is nothing intensive at all. The original implementation used a 4-way stereo Klark Teknik DN8000 analog crossover along with a KT parametric EQ and a regular ol' graphic 1/3rd octave EQ. It sounded quite good and big tours with the Peppers, Peal Jam, and many others were run this way for a while. It wasn't until later on that the processing was changed to DSP due to the extra control. But for a long time Dave resisted because the sound quality of especially the high end wasn't up to snuff on the earlier processors. The 1" TAD compression drivers were quite good at showing those shortcomings. The newer BSS and XTA units seem to address that to the point that it was worth using them along with the benefits of driver time alignment. But even still, the amount of EQ required is very minimal and so is the amount of delay on the drivers to line them up.

So to summarize, there is combing going on in the larger arrays, just like any of the older designs. But it wasn't to the point of where it made things sound bad and the system actually sounded very good. There was even an occasion or two where tours that started on V-DOSC switched back to the Rat Traps because they hit harder for a particular type of music.  I was pretty amazed how good it sounded the first time I heard it with 24 boxes a side which is why I picked some up when I had a chance. They're still using them for one of the ground stacked Coachella stages though I think the days of flying them beyond permanent installs is over. Even though it's old school, it's still an impressive sounding rig and people using them have no complaints. I just wish the boxes weren't so heavy as well as the old Crest amp racks that power them Wink 6 drivers with heavy magnets even in a small box makes for a lot of weight.

Cameron Pro Audio.

"Procrastinators of the world - contemplate uniting!"
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