Trap Boxes?

[Bennett Prescott]

Re: Trap Boxes?

I don't understand why a "line array" as commonly deployed would be expected to produce sound level that drops off like 1/R rather than 1/Rsquared.

George, I agree. Line arrays as we are familiar with them may appear to behave as though they lose energy at the 3dB per doubling distance rate up close, but that is only because as you step back from the array you come in to the pattern of more drivers. Nothing at any point is behaving any differently from any array of point sources (think: subwoofer arrays). This effect becomes clear once you're far enough away that you're more or less on axis from all elements (maybe 4x array length) and the sound clearly begins to fall off at the 6dB/octave rate. Of course the magic of a line array is handling well all those elements acting in concert over such an enormous bandwidth, and being able to aim the majority of the energy at the back of the audience (especially in the HF, on both accounts).

 

[Helge A. Bentsen]

Re: Trap Boxes?

The problem isn't that the array is stacked, but that when it is the angles used are often set to 0 degrees, or whatever. When using a small number of boxes, the splay must be set so the pattern of the HF approximates that of the MF/LF. Any array stacked close to audience head height is going to suck anyway, everyone up front is just getting nailed.

IMHO you hit the nail on the head here. All awful sounding linearrays I've heard, flown or stacked, have one thing in common; 0 degrees between elements. I've heard several good sounding groundstacked linearrays where the angles matched the intended coverage.

 

[Ivan Beaver]

Re: Trap Boxes?

Ivan, I certainly don't disagree with you on that point.I have been involved in side by side tests and in terms of wide and long coverage there ARE situations where line arrays ARE preferable over (most) trap rigs. IMHO of course. ~~:smile:

My point is essentially what Kristian said.

As with anything-it depends on the particular products involved in the "test".

I was simply address the often heard statement that a line array will provide better coverage because it drops off at a slower rate than "point source" boxes.

Well if improperly used-I "might" agree over a limited freq range-but not broad band. But then tell me how the many hundreds of installs I have done with point source boxes provide THE SAME level (within a couple of dB or less) at the front row and the rear row? So there is NO drop off.

We had a side by side last week with a VERY POPULAR "line array" product. The system tech was explaining how he had set the levels on the HF boxes. The upper boxes were +3dB, middle ones 0dB and the front/down -3dB.

He did this so as to provide more HF to the rear (at the further distance) and less to the front/closer. This sounded like a good idea to him. But when I brought it up about what was he doing about the low freq and they were all getting the same level. So the low freq was louder in the front than the rear (natural rolloff), and since the HF was turned down (on the bottom), the ratio of highs to lows from the front to the back were completely out of whack.

So much for "even coverage". Exactly what does that mean?

Strange but the single point source had the same balance of highs to lows throughout the coverage range and the levels (between boxes) were (give or take-based on freq) equal. So which one is "better"? So how come the rate of rolloff is supposed to be VERY different-yet it was the same. After a couple of doubling of distance (if there was a 3dB difference between rates of "rolloff"), then after a little bit-the line array "should" be waaayyy louder-yet it wasn't.

For what is worth-the line array cost more money-was physically larger-required more cabling-weighed more, took longer to rig, had much less bass and had waayyyyyy more sound on the backside. Not to even start to talk about the difference in sound quality-clarity etc.

And we won't even talk about the side to side coverage (which is where line arrays are also "supposed" to be better)-----------------------

But it is "better-everybody knows that".

But that is just my opinion-sorry.