BillFitzmaurice.info

If you set the search function on volts and ohms you'll find some old posts of mine which lay out the relation to power pretty clearly.

Yup, if the RMS on the speaker is 250, then buy an amp that does 250 watts RMS per channel. For now, keep it simple. There, all done.

That was eazy.

If you have multiple drivers in ones speaker then I just add all the RMS values together to calculate total amps needed?
If the speakers are in paralel the ohms will lower and RMS will get higher.(and the formula for this was ?)
If they are in serial the ohms will get higher and the RMS will do what?(any formula for this?)
And rule of thumb is to add little for amp overhead.

Well I think that sums it up

u4david wrote:That was eazy.

If you have multiple drivers in ones speaker then I just add all the RMS values together to calculate total amps needed?

As long as it's the same type of driver and the connection is sensible, yes.

u4david wrote:If the speakers are in paralel the ohms will lower and RMS will get higher.(and the formula for this was ?)

P=SQR(U)/R (or P=SQR(U)/Z, if you want to be picky), which means half the impedance => twice the power

u4david wrote:If they are in serial the ohms will get higher and the RMS will do what?(any formula for this?)

Same formula means half the power in total, which amounts to 1/4 of the power to an individual driver for two drivers in series.

u4david wrote:And rule of thumb is to add little for amp overhead.

Well I think that sums it up

u4david wrote:That was eazy.

Calm down there Skywalker.

This thread wouldn't exist if it was that easy. ...and we're literally skimming over the very basics of AC circuits here. Wait until you get an amp and try to set up gain structure, figure out appropriate limits, etc...

Learning this material, most of which is beyond the scope of this forum, is not impossible of course, but it isn't just a "walk in the park" either.

All I need is mathematical formula that are written mathematically correct withe explanation of values used.

Thanx.

u4david wrote:All I need is mathematical formula that are written mathematically correct withe explanation of values used.

Thanx.

http://www.scribd.com/doc/3642960/Elect ... planations
Page 5/16 gives you what you require.

Wow ... an ant hill turning into Mount Everest!!!

You buy an amp loosely based on the RMS power handling of your speaker circuits. If your speaker load handles 500w @ 4 ohms, you GENERALLY want an amp that will deliver roughly the same ... HOWEVER, some peoples' needs may not require that much power, yet some other people will want MORE power to allow headroom. There IS no clear-cut RULE to it!

These days, many power amps include DSP with various functions. So, now your DSP needs are another reason for selecting a particular amp.

Proven reliability is also a very important aspect of your amp choice. What good is an amp that stands a good chance of shutting down at a gig?

Last but not least is budget.

Your decision is made by balancing all of the above factors, not just power.