Sounds ideal, but.......
Any comments
Tom R.

If you haven't read my Near Field Line Array White Paper, you need to do so. It is located at the link below. This paper will explain what happens to a line of drivers as you approach center to center spacing of a wavelength and greater. Essentially, the comb lining starts to impact your performance but the worst of it is that the array gain (or sensitivity of the array) begins to decrease. For most drivers in the 4 to 6 inch diameter--spaced so that they touch--this is usally in the 2000-3000 Hz area. Hence, the sensitivity starts to be reduced and only via heavy equalization can you overcome this reduction. Bottom line when you space a line of drivers (even the very best full range drivers) close together they interact such that their performance is governed by the array spacing properties and not by their individual frequency plots.

Darren Kuzma of Parts Express built an array a couple of years ago with 2.25" square flange size Tang Band full range drivers. See:

http://www.partsexpress.com/projectshowcase/Kuze3201/Kuze3201.html

Look at his performance plots and observe the unequalized sensitivity reduction as you go into the 5000-10,000 and 10,000 to 20,000 Hz octaves. Larger drivers will have performance impact even lower in frequency.

Jim

• Near Field Line Array White Paper

Thanks,
Tom

Thanks,
Tom R

"the system's upper f3 frequency by a factor of 0.7 with every doubling of radiating plane area"...

Does this still happen when using a true line source for the hf drivers. I am guessing that the pro sound setups do not have the mutual coupling for the tweeters due to tight spacing not being practical.

-Linc

I don't support Bill's rule of thumb as an always true result. The best answer is to measure the performance of the array. This is because the array performance depends upon the overlap of the radiation patterns of the individual drivers (also whether you are in the near and far field). I'm finding that even for well behaved individual drivers that the array effects are hard to predict without measurements so rule of thumb thinking isn't always valid.

Note that some drivers--most notable are ribbon and planar tweeters--have reduced vertical axis pattern overlap vs. frequency. Hence, little vertical radiation interferences or mutual coupling occurs between the arrayed drivers. Arraying doesn't really impact the bandwidth for this case. Therefore, Bill's rule doesn't apply for this example.

Jim

My2c
Jorge