Crossover frequency selection for line array

[goldyrathore]

In an array where the mids form a line and a single woofer is placed below it like
http://www.parts-express.com/project...oject=Colossi, how does one choose the woofer to mid crossover frequency (ie choose the highest possible crossover frequency, assuming a good overlap in mid and woofer driver responses)?

In case of two drivers side by side, the ctc determines the crossover, however, in the line array case how does one calculate the ctc between the line of mids and the woofer below the line ?

[goldyrathore]

http://www.parts-express.com/project...roject=Colossi

[Ferrit37]

Hey Goldyrathore,
to determine the crossover points between components you need the step distance (ctc) between components to equal a half wavelength of your operating frequency.

the formula L = C/F gives you the wavelength of the frequency and you need to divide this by 2 (C = speed of sound)

You need to make sure that all of the midrange components are included, you don't want the top of the array outside the step distance.

So given the design cited it appears that the top midrange is about 59.25" from the center of the woofer putting the values of C=13340" into the formula it would seem that 113Hz would have a half wavelength of 59.46".

The value of C changes for Temp/altitude/Humidity so you should enter one for your local.

Check out Christian Heil's paper on the L'acoustics page.

Hope this helps

[tinitus]

I agree
Due to array mids, the woofers should be crossed very low
I dont know the mid drivers, but 6" ought to be capeable of "running loose" with no highpass xo
With that many mid drivers there should be no problems with Xmax

Where to cross woofers would then depend on mids natural rolloff, which could be anywhere from 50-100hz
Some plateamps or standalone filter will have active highpass as well, and would be more flexible

[goldyrathore]

Isn't the crossover of Vista , from MartinLogan (http://www.in.martinlogan.com/specs/vista.html)
too high if the same rule is used? I am assuming the same
rule applies for line source too. Vista is crossed at 450Hz 'ween the woofer and the panel.

[Ferrit37]

Well I'm not that familiar wth the "Maggies" but it might be a case of the HF panel not going low enough.

Not having the X-over point at the stipulated frequency affects the vertical polar response.