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Xti4002 with (2) JBL MRX518S


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#1 Gman598

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Posted 17 August 2012 - 07:17 PM

I just picked up an xti4002 to power my two JBL MRX518S.  I'm gonna run it mono summed input
With a stereo setup output,  4 ohms left, 4 ohms right output which should provide 1200w per speaker.


The other piece to the puzzle is I have a driverack PA that manages the signal.

Questions are....

Is the amp to much for the bins?
Should I use the limiter provided in the xti?
Any other advise would be appreciated.

Thx
Joe

#2 dakos

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Posted 17 August 2012 - 11:13 PM

Hello and welcome :)

No, it's not too much.
The rest depends on your usage of the bins, what type of music you run through your rig?
What other boxes and gear you have?

#3 Gman598

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Posted 18 August 2012 - 06:52 AM

Top 40's rock band.

I have the MRX515 for tops which I plan to replace the current ampl with a XTi2002 running that in 4 ohm bridged, a mackie CFX16 mixing board, a crown 402 (I believe) for the two Jbl jrx112 monitors.

The 402 took a dump and I'm deciding to upgrade my current gear with lighter more powerfull amps.

I started with the bass bin amp rotating my existing gear to the rest of the speakers.

The current amp are competitor products and so I don't post them here.

#4 dakos

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Posted 18 August 2012 - 08:47 AM

First of all, it's perfectly OK to discuss gear made by other brands especially if it's gear that you already own.

Now for the current issue, live rock music usually needs allot of headroom unless a compresser is used on the "problematic" channels but with the cost of changing the sound. Usually headroom upward of 10dB is needed for live rock so you need to limit your amp in a manner that would suit your needs. you can use the limiters on the XTI to achive this or in your favorite processor.

#5 Gman598

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Posted 18 August 2012 - 09:18 AM

Thx for response just wanted to be respectful to the board. My current setup is

mackie cxf16
Driverack PA
QSC 1450 bridge MRX515
QSC 2450 summed MRX518S left/right 4ohms subs
Crown xls402 JRX112M monitors

At the present all the gain levels are matched. So of the boards not clipping nothing else is.

Im the guitar player and run sound while playing (which is difficult)

The 402 started cuttin out so I bought the 4002 to replace the 2450 and so on taking the xls402 out of live play.

Which makes perfect sense (to me) because the subs are starving for power plus the poweramps weight like 45lbs a peice and there about 6 years old of heavy use. They have given me no problems but I think I'm on borrowed time with those amps.
And we play about 50-60 shows a year now. Was 80-95 but we are getting older lol.

So I'm upgrading to lighter more powerfull amps.

The speakers  were the first upgrade cause I used to have EV Eliminators tops/subs. They were heavy.

I'm not really sure where to set the limiter on the amp.

#6 Gman598

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Posted 18 August 2012 - 09:47 AM

Oh yeah. I have an alesis compressor in the kick drum.

I've been trying to use the other side of that compressor on the mains but it always seems to cause me some trouble. It's user errors I'm sure.

#7 Gman598

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Posted 20 August 2012 - 08:03 PM

AnyOne?

#8 dakos

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Posted 23 August 2012 - 01:16 AM

Hello again,
The RMX series are built like tanks but they also weigh like tanks. An amp has three characteristics, light, high quality, cheap, you can choose only two :)

So about the limiters, then yes, feeding the subs this amps continuous power would definitely damage them, so you have two choices, use the limiters on the DRPA or use the internal amps limiters. I would suggest in favor of the amps limiters because the amps DSP knows exactly what's going on with the output of the amp where as the DRPA is only guessing.

I think this link will provide you with lots of relevant info:
http://www.bennettpr...undamentals.pdf


#9 Gman598

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Posted 23 August 2012 - 02:57 PM

First thanks for response and please don't take my question as a discredit to ur answer. I'm Stilllearning the whole sound thing.

But isn't it always the theory you are supposed to have double the wattage amplifier than the speakers RMS.

Which the bins are 500rms and the amp is 1200 per side which is just slightly over.

The main reason for the amp was to have comfortable headroom for the PA.

#10 dakos

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Posted 23 August 2012 - 03:26 PM

That's exactly why I posted the link... It might be a bit technical but it's spot on.

Happy reading :)