TSG wrote:
As a side question, with four t48's, can I go to 35hz or is 40hz recommended? and whats the impedance of the finished OT's and DR's?
Yes, 4 x T48's can be high passed at 35Hz. T48's impedance will be 2 ohms greater than the nominal impedance of the driver used, due to the horn itself, it's called acoustic impedance.
It's best though to consider the sub cabs to have the impedance of the driver, and simply know you have added a small margin of safety.
Your tops/mains impedance you can consider to be the same as the nominal impedance of the driver.
I've been pondering this for a while, and, I'm not sure it's of benefit, but part of your goal is "lowest possible amperage".
As you add more cabs to a given amp channel, overall impedance lowers (if wired in parallel).
The result of that is that output from the amp in amperes rises, and places more demand on the power supply of the amp, therefore, more power draw from your supply.
It would remain to be seen if only having 1 cab per channel, in other words, 2 amps for mains and two amps for subs, may lead to overall lower ampere demand than paralleling cabs on one amp. I guess it's worth considering.
One thing is certain though. If you series wire the cabs instead on each channel you raise, in the case of the tops/mains, the impedance to 16 ohms, which will be a significant reduction in ampere output.
Having said that, you now need an amp which can provide double the voltage swing. That would be around 90V for series wired DR280's, and 120V for series wired T48's. The Berry 6000 will just about do the 90V, but you would need another amp to provide 120V...
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Built:
2 x DR 250 (melded array) with March 2012 plans.
4 x 20" BP102 T39's, 2 x 28" 3012lf loaded underway.
3 x WH8 with melded array.
Bunter's Audio and Lighting "like"s would be most appreciated...