Hello

Hi everyone,
Sune from Denmark here. Good to meet you. I'm looking forward to learn from the Seeing sound course. I've have worked in live sound since the mid 90's and have done most every step from packing houseboxes and trucks, rigging PAs, mic'ing, patching, babysitting, sys-tech'ing, mixing monitors and FOH. I have toured a lot and mixed hundreds of shows so I'm a confident sound engineer, but I have recently taken a new steady job that involves designing and tuning medium to large systems and I lack experience in those fields, so I'm hoping to hone my skills. I'm also not great with math (I sort of understand most but easily forget) so always good to refresh some theoretical stuff. Cheers

Hey Sune, welcome aboard. Nice to have you. Share a photo of something you've worked on some time.

One of the most fun this year was a sunset show on a mountain i Abruzzo in Italy. The show was timed so the sun set at exactly the last encore. It was a Meyer system (Lina and 750 i think) that at first I was worried it was a bit too small, but conditions where perfect – outdoor, crowd sitting on the ground, no wind - and the sub array was well configured by the local PA guy. It was great.

And in AV world I recently did a corporate award show with a Coda system. Viray mains with subs flown behind, NRay side arrays and TiRay delays. A horrible room! My buddy had to leave in the middle of setup because his wife went into labour, so it got a pretty stressed, but it went well thanks to our great crew that came in last minute to substitute and the client was happy.

Wow, very nice! Any idea what kind of sub array design was used in the first one?

I haven't used any CODA, yet. I hear about it more, so they must be growing.

Those six subs where just in a horizontal line with delays added to sides. I suppose you would call it an In-line beamforming array? It's hard to see in the photo, but there are front fills on top of four subs.

CODA is good. Especially the high freq. response is very transparent, defined, detailed and has even coverage.

In-line beamforming array

That typically called a sub arc.

But of course. Sub arc. I would usually just call it a sub array, but suppose that not so specific. Sub arc.. 😀

I think I started calling it that after some LA training. I like it. Some people say physical arc or digital arc or delayed arc to be more specific. One mistake, though, is to put your subs so far apart that they are no longer coupled. I see this sometimes. Then they are just individual point sources.

Makes sense. That’s what got me here - to get sharper in configuring for example sub arcs. What’s the rule of thumb for the distance between elements in the arc?

An easy rule of thumb is about 6ft (1.8m), which is 2/3 wavelength at about 125Hz.

But, if you have time before the gig, find out the maximum frequency required by the alignment with the mains. To do this you'll need the transfer functions. The is easy to do in MAPP3D, where you have a virtual measurement viewer. If you can't do that, you can use the top of the operating range from the spec sheet, but of course this won't account for the hay stacking you'll end up doing in the field. :)

Once you know that frequency then you can calculate the maximum spacing at which you'r directivity will stop.

Put this into mathnotepad.com
c = 345; # speed of sound
operating_range = [50, 112]
spacing_max = (2/3) / (operating_range[2] / c)

In this example, 112Hz will give you 2.05 meters. Add some hay stacking, reduce this to 125Hz, and your max spacing is reduced to 1.84 meters.

Seeing Sound is the course you want. After get Bob McCarthy's Book Sound Systems: Design and Optimization and you will already know most of what he talks about.