PMA - 60; New arrayable double 12 and horn.

Peter Morris

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May 8, 2011
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This is more or less an up date of my double 10 and horn design. It’s the same height and when multiple boxes are packed front to back it takes up about the same amount of truck space.

I often see people wanting use 2 or more boxes together to get more power, but they never array very well. The idea was to build a 60 x 40 degree box that could be tight packed and array with a lot less issues.

It’s a MTM design in a trapezoidal box. It has uneven angles - 25 degrees and 15 degrees. By doing this I can place 2 boxes side by side and have a total splay of 50 degrees with all the drivers very close together minimizing comb filtering issues.

It’s necessary to have the other side at 15 degrees to get enough volume in the box. There is not enough room on the front of the box for reflex ports and they are located on the back, one on the top, and one on the bottom. They also work as a handle and add bracing to the walls.

You can array 3 or more boxes with 40 degree splay between the boxes.

To get 25 degrees it’s necessary to machine the inside wall of the box on one side to fit the compression driver in.

It uses:

2 x B&C – 12HPL76 (I had these in stock and it was too difficult to get other drivers due to COVID-19)

1 x B&C DCX464

1 x Ciare PR614 horn

Processing – I’m using Linea Research ASC48 with LIR crossovers and FIR processing, but it should be very easy to get good results with other processors.

It designed to operate from 80Hz to 20K with a mid crossover frequency around 675Hz and 3250Hz for the VHF. In my case the mid crossover overlap by 100Hz (at the moment).

The plan is to build some MID-HI passive crossovers eventually ... more to come :)
 

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Jeff Manning

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Jan 23, 2020
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Dang, and I just started ordering components for a double 10 and horn build...
Will be following this thread with great interest.
Thank you so much for sharing this and your other projects!
 

Peter Morris

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May 8, 2011
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A couple more pictures - bottom rear port and top mounted fly track with internal aluminium bracing seen through top rear port (the box is upside down and its to be painted black)

... and DCX464 - very close fit.
 

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Peter Morris

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May 8, 2011
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So, why build & lug 4 cabinets if 2 PM90s can do the job. 😉
These are smaller and lighter ... and you can array 2 or more boxes to get 110 - 120 degrees of coverage - perfect for front fill on a medium size rig or a small show that needs wide coverage :)

The idea behind the PM90 was the loudest best sounding box you could put on a stick, it was not deigned to array ... The idea with the PMA60 is a smallish arrayable box that can be used as one, two or three per side.

BUT most of all, a COVID-19 project while waiting for work to resume ...
 

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Malcolm Brown

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Dec 31, 1969
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Again, nice work.
I personally don’t understand why a commercial manufacturer doesn’t offer something like this.
If you ever go «commercial», I’m up for six of these :)
Helge, Renkus used to. Maybe they still do... but as much as these boxes would work for me, promoters want to see line array looking things... regardless of performance. JBL VRX and company sorta poisoned the well...

That said, I have 6 old Renkus Trap 40/60's that are simply too heavy for me with out a three man crew. If I go back to live sound after covid, if I can't do it with 1 crew guy - I ain't doin it. These boxes look super cool to me as I expect they would be light enough to one guy to get onto scaffold.

I live in a very high wind locale and do a lot of wind sports event support. I'm a ground stacker. Anybody flying a rig here in either nutz or uncaring and well insured ;-)

6 of these might be perfect for me. I would build out of 12 mm VF euro ply.

I've been think about boxes exactly like this for a while. could these be done so 2 boxes arrayed would cover 80 degrees ?
 
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Joris Wijgerde

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Nov 29, 2019
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Looking good!
Out of curiosity, which 12" drivers would you have gone for in an ideal situation?
What about the FaitalPRO 12PR300 for example?
 
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