Jasonstry wrote:
And it isn't a 2 Ohm Load as the boxes aren't covering the same frequencies and a single amp doesn't "know" that the crossover is there. It sees a 4 Ohm load up to the crossover point and a 4 Ohm load above the crossover point so, except for some anomalies around the crossover point, the amp just sees a 4 Ohm load.HTH. Andy |
Was thinking about this last week due to a project I was working on. I was unsure of the effect on ohmage load with a passive crossover. I couldn't come to a final conclusion but thank you, I think I've grasped it now. I've always avoided passive crossovers in subs etc due to only achieving half the power from your system. 1 of the first things I learned down my local PA shop was that using the passive cross over with say a 2x 400w amp @ 4ohm (ingnoring the tripple power rating rule) feeding 2 400w 4ohm subs and 2 400w 4ohm mid/tops you would get a split of the 400w between your speakers and not an actual 800w of power. I'd never realised that this was due to the passive not dropping the circuit down to 2 ohms until now.. If the passive wasn't there the power available would double as the ohmage has halfed. This gives you 800w a side @ 2 ohms. I'd not thought about this in reverse. If the passive is there and the ohmage dropped I would get the correct split of 400w bass and 400w mid/tops. I already know this is not true I only get the 400w full range then split. So of course the ohmage at the cross over must stay the same. Simply using a 2x800w 4 ohms (still ignoring the tripple power rule, trying to keep this simple) with the passive wouldn't get the full 400w per speaker. The peavey passive cross over is designed for 400w of full range signal which it divides into what ever ratio of bass and mid/tops to the speakers. Better speaker builds like the massive cross overs in the logic bins I used to have may handle this differently. They will no doubt be designed to take a power rating much higher than stated and divide it acordingly. I may be wrong on this though... The best soultion will always be. Using an active cross over and 2 2x400w (ignoring tripple power rule) amps would feed 400w to my subs and 400w to my mid/tops. Note for OP: If you are new to audio the tripple power rule is about using amplifiers tripple the rated power of the speaker. This is due to music having high crest factors. Over compressed music will have lower crest factors so most people stick to using amplifiers double the rated power of the speaker.
Having an amp with matched values means you will be driving the amp into clipping to get the needed power out of your system. This can cause more damage than using a larger amp and actualy over powering your system.
|