Understanding of Voltage

[djtrumptight]

according to the voltage calculator on www.the12volt.com:
400 W x 8 Ohms=56.5 Volts
400 W x 4 Ohms=40 Volts
300 W x 8 Ohms=49 Volts
300 W X 4 Ohms=35 Volts

So i was taught that with a parallel load,the voltage would be the same across both speakers but the parallel load also changes the impedance to 4 Ohms so for example:
If i'm using 1 DR 250 per side with my crown XLS 1500 i have 49 volts to work with but if i parallel 2 DR 250's per side i can only get to 35 Volts ?

[GirlyHandedDog]

according to the voltage calculator on http://www.the12volt.com:
400 W x 8 Ohms=56.5 Volts
400 W x 4 Ohms=40 Volts
300 W x 8 Ohms=49 Volts
300 W X 4 Ohms=35 Volts

So i was taught that with a parallel load,the voltage would be the same across both speakers but the parallel load also changes the impedance to 4 Ohms so for example:
If i'm using 1 DR 250 per side with my crown XLS 1500 i have 49 volts to work with but if i parallel 2 DR 250's per side i can only get to 35 Volts ?

I believe the problem is that you're not taking into account that the wattage changes with impedance when it comes to output from your amplifier. According to the spec sheet, the XLS is rated at 525 watts at 4 ohms and 300 at 8 ohms. Run those numbers through your voltage calculator and you'll get close to the same voltage.

[Michael Ewald Hansen]

You've kinda got it upside down. If your amp is capable of producing voltage swings of 50v it doesnt matter if the speaker is 4 ohm or 1000 ohm, it will still see 50v. However, the amount of wattage your amp is able to put into the speaker is dependent on the impedance - so that means, an amp that can produce a voltage swing of 50 volts and see an 8ohm impedance will output (50*50)/8 = 312,5 watt..

[djtrumptight]

ohhhhhhhhhhh,that makes a difference,i'm thinking 300 and disregarding the 525,thanks !!!

[GirlyHandedDog]

You've kinda got it upside down. If your amp is capable of producing voltage swings of 50v it doesnt matter if the speaker is 4 ohm or 1000 ohm, it will still see 50v. However, the amount of wattage your amp is able to put into the speaker is dependent on the impedance - so that means, an amp that can produce a voltage swing of 50 volts and see an 8ohm impedance will output (50*50)/8 = 312,5 watt..

Well put.

[Gregory East]

There's very little to be gained from exceeding 35v in a dr250. If you haven't got enough SPL at half power you need double the cab count, not double power.

[djtrumptight]

Thanks fella's,just trying to understand the math.Gregory,i keep my DR's limited to 35 volts,for now anyway.When i build my other set of T 48's i'm gonna go up to 40