Amp watt = 1.5 x Speaker "RMS" or "Peak" Watt?

[aznwonderboy]

I am trying to buy an amp to match my loudspeakers. After a couple of hours searching the forums, I learned that I should get an amplifier that is 1.5 times the power handling of the speakers.

However, I didn't see any post mentioning if it should be 1.5 times the RMS power of the speakers or the Program/Peak power of the speakers. Please clarify.

--If I have a 250 RMS (400 Peak) watts speaker and 300 RMS (600 Program) watts speaker in PARALLEL both @ 8 ohm, then is that equal to 550 RMS watts @ 4 ohm?

--So, I should get an amp that can handle at least 825 watts/channel @ 4 ohm to play both speakers in parallel safely? If I get an amplifier that is somewhere between 550 to 700 watts/channel @ 4 ohm, will that still be safe?

--Should I use the "amplifier equation" using Peak or the RMS power of the speaker?

I appreciate you guys for reading, and thanks to those who can advise.

 

[karyoker]

The general rule of thumb is an amp rating of 2 x rms. If an exact match cant be found then use a range of .8 to 1.25 times the amp rating.
It is not recommended to parallel speakers as the speakers are reactive loads which means that different freq's see different loads. Remember that the heavy bass is whats taking the power and turning up the bass on the mixer is loading the amp more.... Running two speakers especially different ones in parallel if you are rockin wont last long...

 

[boingoman]

It is not recommended to parallel speakers as the speakers are reactive loads which means that different freq's see different loads. Remember that the heavy bass is whats taking the power and turning up the bass on the mixer is loading the amp more.... Running two speakers especially different ones in parallel if you are rockin wont last long...

Paralleling is actually the most common way to chain loudspeakers. Most speaker boxes designed to be chained together come from the manufacturer wired so they will be paralled when you chain them. This lets you get more power from your amp because of the lower total impedance. It also provides the benefit that if one speaker blows the rest still play. Paralleling your speakers will have no effect on the amp unless you drop below it's minimum impedance load.
Series wiring increases impedance. It is used a lot in guitar cabs, along with parallel, so for instance you can use four 8ohm drivers and still have an 8ohm box. Two sets of two 8ohms in series= two sets of 16ohms. Parallel those, it equals an 8ohm box.

So 2X8ohm boxes chained together usually gives you 4ohms. Get an amp that can push the power you need at the impedance you have and you will be all set.

 

[karyoker]

Yea it'll work I've installed 70 volt systems and hooked up speakers every way but loose including stacks & bins. It'll put out noise....

But since all speakers have unstable impedances, especially in the bass regions,
the impedance of 2 in par might be 2 ohms. Ok let's say your amp is rated to go down to 2 ohms. Now the ratio of power needed at bass freq's is 2:1 No bass so crank up more bass It'll work for awhile. Maybe even a few weeks or a year if you are careful. But in a system designed for best overall gain, and "flat" across the spectrum and if you are particular about what it sounds like I dont recommend putting speakers in parallel (of course that is just my opinion)

 

[boingoman]

Well, wonderboy is going to 4 ohms, well within limits for just about any PA amp. Modern amps take into account that loads drop below the limit at low freqs. The rating is nominal impedance, not actual. High damping factors also help control low end at low impedances. PA speaker boxes are designed to be paralleled.

I agree, don't go below your amp's limit. But there is no danger paralleling speakers. The system I use most is a QSC Powerlight 4.0 driving four 4ohm JBL sub boxes for low end. 2ohms a side, pushed hard, and no problems in five years.