[Arizona Dan]

Before I ask a question, I would like to say that I have enjoyed this forum immensely.  This question concerns the operating frequency range of a midrange driver used in a line array.  If you are using many drivers, for instance twelve, can the drivers be used at either a higher and/or lower frequency range than if just one driver is being used.  I might have more questions, but for now I will keep it short.

Dan

[S Clark]

Absolutely you can get more bass out of a smaller driver.  Let's say that a driver is down 6 db at 35 Hz, but if you have two groups in parallel, you get about a 6 db gain, so filter the drivers back, leaving the low gain and.... Voila! a driver that usually has little output at 35Hz is suddenly playing at full volume.  That's the idea anyway.

[planet10]

Well sort of... the midbasses won't go any lower, but the array will have more total output, so if 1 is straining down low, it is less likely that many will. The centre-to-centre spacing of the drivers will lomit how high you can take them -- in most cases this is less than a single can reach.

dave

[S Clark]

Well sort of...

I realize that I simplified significantly, but it is still legit to say that a speaker that has low output at a low frequency can have quite a bit more output if say 4 groups are wired in parallel.  Then the designer can use the crossover to lower the mids and highs until they match the bass. 

[Arizona Dan]

Thank you S Clark and planet10.  So, let me think this through.  Let's say that the design consists of many drivers and because the demand on each driver is small, the drivers could produce more bass than if there was just one driver.  So far, so good.  Here is the part that I do not know.  Pick a good midrange driver.  Start testing to determine frequency responce.  Start at a really low volume - say 40 decibles.  Then repeat the test in 10 decible increments.  Will the response curve be flatter (reach lower) at low volumes and then have less bass response as the volume is increased.  What I am really leading up to is equalization going to be required to get the drivers to produce more bass (assuming that the driver is still operating within its linear range of travel).  And, if equalization is required, can it be done in the crossover?

If this is confusing, just say so and I will try again.

Dan

[S Clark]

Each driver doesn't produce more bass, but the total amplitude increases.  So if a driver has a 90 dB output at 2K Hz dropping off to 70 dB at 30 Hz, several groups could increase the 2k Hz output to over 100dB and the 30 Hz output to 80 dB.  Now let us say that the crossover reduces the 2K Hz output to 80dB, then the result could be flat to 30Hz--- from drivers that individually have little output at the lower frequencies.  And yes, it can be done in the crossover.  Hope this helps.

[Arizona Dan]

Thanks S Clark.  You have been very helpfull.

Dan

[Taterworks]

For clarity:

Drivers that are already capable of producing significant bass relative to their overall frequency response curve but are limited by small displacement can be used to good effect in line arrays without any further tweaking.

Using more drivers in a line array won't get you any deeper bass because the +6dB increase in sensitivity of the system from doubling the number of drivers is effective across the entire spectrum. There's no magic in the radiation pattern or room loading or anything -- it's just more of the same driver.

However, it is possible to use passive frequency shading or equalization to get meaningful bass response from small drivers in large numbers.

(I have not heard a line array, but I would be very interested to see the impulse plot. Your ears are not a line.)