Wiring a line array: altering wiring schemes for matching levels w/woofer

[dave251]

I've built a couple of line arrays so far as an experiment on the viability of using these as a small club system. I've had these together for a couple of years and have been most pleased with the results. These have been used with my western swing/jazz band with great success. Our typical room is less than 200 seats, and I'm able to place these BEHIND the band, and eliminate the use of monitors. I do mic everything through small backline amps, with an overhead and kick drum mics thrown in; three vocal mics.

The next project will be of much higher quality speakers, and with the design goal of keeping size to a minimum. To that end , I have my choice of speakers for the line array, using eight or nine units per column. This will yield impedances between 4, 8, or 16 ohms. The woofers(subs) are at eight ohms. Here's the problem, according to spec on the components, using eight or nine small cones is MUCH more efficient than the single woofer.

So here's my thinking: can I balance the sensitivity of both the line array AND the woofer cabs by adjusting the impedance of the line array? For example, using a 16 ohm impedance of the line array to drop the efficiency by 3dB? This would put them much closer in sensitivity to the woofer? Or do I have it backwards and need to go to a 4 0hm impedance? I'll be using a simple 1st order passive crossover at 250hz....

All suggestions are welcome. Thanks

[Jim Griffin]

The answer is on page 17 of my "Near Field Line Array White Paper". The NFLAWP is at:

http://www.audioroundtable.com/misc/nflawp.pdf

Lowering the overall array impedance increases the sensitivity while if you raise the impedance, the sensitivity goes down.

Now this is a theoretical calculation and your best bet is to measure your specific array to verify your case.

[dave251]

Thanks, just what I was looking for.

[bear]

well, yes, but why?

the ideal situation is to biamp.
running them as a PA/SR it is nutz not to use separate amps for the line arrays and the subs. Then just set the levels.

Wire the arrays for maximum SPL vs power in - you need SPL, and there is a limit to how much power you can put into them, even if you have a iNuke amp (for example).

An active xover is pretty much a must for this sort of application.

Also in terms of coverage and freq response, it is better for the array to be longer and taller - reach the floor for best low mid response, and go high so that the audience is not shaded by the highs...

imo.

_-_-

Assuming for the moment that you are really into high quality amplification, use the high quality amp for the line array, and a high power class D thing for the bass. Done.

[Jim Griffin]

I agree with Bear on bi-amp'ing a situation like Dave's. In fact I bi-amp (two-way) or tri-amp (three-way) where I can with line arrays so the adjustment of sound levels can be easily made.

[dave251]

In a word.....simplicity. These will be used in cafe/small club/lounge situations. I carry a self contained PA/mixer amp. With the design of the system, and my particular application, I don't need a separate monitor system. I can just stack the two arrays on my pair of subs(total about 8ft tall) and get GREAT coverage. I do prefer a 1st order crossover. Again, simplicity is the order of the day. I'm in the Kansas City area; most gigs are three and four piece jazz/blues groups....where ease of setup and simplicity of operation are required.

I got the inspiration for this design from the Bose small line array system...which is of course WAY too much money for most folks, since you need at least TWO complete systems(and then add a decent mixer) to cover even a three piece band at more than quiet lounge volumes.

[bear]

yeah Blose... thump and sizzle... nvm.

The size and cost of a digital amp is so low today as to not be significant.
In fact you can build it/them (a few could be used) into the array itself. PE sells dual and quad 100w and 200w Class D for example...

Gonna be as good as that self contained PA/mixer amp.

The simplicity you speak of I think is a false economy...

_-_-