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#1 jameskerr87

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Posted 03 December 2005 - 02:32 PM

I need amps to power my speakers. I have...

4x JBL SR4733
4x JBL SR4715
2x JBL SR4719

its for a rock gig in a concert hall with a 2000 capacity.

this will be a great help.

cheers -james-

#2 DGlass

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Posted 05 December 2005 - 10:50 AM

I have gone ahead and deleted your duplicate post in the Amplifier Troubleshooting section of this forum.

I went to the JBL Web site and got their power and impedance specs for the SR-X speakers. The SR-X series power rating is listed as “Rated Power” with a foot note that says this is tested using “IEC filtered random noise with a 6 db crest factor”. The IEC and AES tests are basically the same so if you look around other JBL products you will see that this is also called their speaker “Power Capacity” rating which is the speaker’s “Continuous Power Rating”.  blink.gif

All three SR-X models mentioned are 4-ohm, 1200 watt Continuous Power rated.
Following the guidelines discussed in other postings of this forum for doing Amplifier Selection calculations……… and doing the math:

1200 watts x 2 (for 3db of headroom) (Program Power Rating)
2400 watts x .8 = 1920 watts
2400 watts x 1.25= 3000 watts

You would be looking for an amp that would do about 2400 watts/ch and be in the power range of 1920 watts to 3000 watts/ch with a 4-ohm load.

I would recommend only putting one speaker per amplifier channel keeping each channel to 4-ohms. This is to allow for the best power headroom as impedance is not a fixed number but is frequency dependant. For example: The 2241 cone used in the SR-X 4715 and 4719 is nominally rated for 8-ohms each in but from 150 to 250 Hz. they are about 6.5 ohms each. “Nominal” rating for the two cones in each box is what gives the 4-ohm rating provided for the speaker. But at 150 to 250 Hz two of these speakers in one box is closer to 3.25-ohms. Now….. if you put two boxes on one channel of an amplifier you would have about a 1-ohm load at 150 to 250 Hz.

In your case you would be looking at five two channel amplifiers.
For two channel amplifiers in this 4-ohm power range we make the IT-4000, the IT-8000 and the MA500vz.   smile.gif

#3 jameskerr87

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Posted 05 December 2005 - 02:22 PM

Thanks, this info is very helpfull to me.

cheers
-JAMES-