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Small Club Gig Rack Amp Choice


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#1 MDArm

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Posted 30 August 2005 - 01:56 PM

I am putting together a small club PA.  I want to keep it simple - MackieCFX12, DriverackPA, Crown Amp.  I want to run monitors (4 @ 8 ohm each) on one side of the amp and the mains (2 @ 8 ohm each) on the other side.  Which is the best amp to handle the unbalanced load?  My choice would have been a MT2400, which is no longer available.  Which of these other choices would work best, if at all?  
Xs1200
CE4000
K2

#2 Bud Bolf

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Posted 30 August 2005 - 10:01 PM

QUOTE(MDArm @ Aug 30 2005, 02:56 PM)
I am putting together a small club PA.  I want to keep it simple - MackieCFX12, DriverackPA, Crown Amp.  I want to run monitors (4 @ 8 ohm each) on one side of the amp and the mains (2 @ 8 ohm each) on the other side.  Which is the best amp to handle the unbalanced load?  My choice would have been a MT2400, which is no longer available.  Which of these other choices would work best, if at all? 
Xs1200
CE4000
K2
View Post


Hi MDarm,
  Your question is way too generic!
There is not enough information, for a good response.
As important as Ohms are per cab, so is the rated Wattage of the cabinets.

  About the only thing that I can say, is that 4 Monitor Cabinets that are rated at
8 ohm's each, if put on 1 Channel (Paralleled / Daisy chained) together,
would be around 2 ohms. Two Main Cabs at 8 ohms each, paralleled together
and on 1 Channel would be around 4 ohms.

Now the next part of the equation is: Wattage rating's per Cab?
If you have the exact Make and Model numbers of your Monitors
and Main Cabs, that would really be helpful.

Post back with more Info.
     Thanks,
         Bud

Do you want all 4 Monitors to have the same Mix?
The XS1200,CE4000 and the K2 can ALL be operated with a different Ohms load per Channel and will put out the Power designated per that Ohm rating!

#3 DGlass

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Posted 31 August 2005 - 01:03 PM

MDArm,

As Bud has mentioned power specs on all the speakers would be needed to properly select an amplifier of the correct size.
The four 8-ohm monitor speakers on one side of an amplifier would be about a two ohm load. We would then need to select an amplifier that could drive that load with the necessary power. (Check out the other postings in this forum on amplifier selection to get an idea of what we are talking about.) When we select an amp big enough to handle the 4 monitor speakers, on one channel, we may have an amplifier that is to big for the two FOH speakers. In this case using two amps, one for monitors and one for FOH, may give a better power to load match.  smile.gif

#4 MDArm

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Posted 31 August 2005 - 10:37 PM

QUOTE(MDArm @ Aug 30 2005, 01:56 PM)
I am putting together a small club PA.  I want to keep it simple - MackieCFX12, DriverackPA, Crown Amp.  I want to run monitors (4 @ 8 ohm each) on one side of the amp and the mains (2 @ 8 ohm each) on the other side.  Which is the best amp to handle the unbalanced load?  My choice would have been a MT2400, which is no longer available.  Which of these other choices would work best, if at all? 
Xs1200
CE4000
K2
View Post

Thanks for the quick response.  The two mains are EV qrx/75 and the 4 monitors are all EV Eliminator Monitors.  Since I am going through only one channel, I am cornered into the same mix for all four monitors.

I currently run a larger system a follows:
MackieCFX16 - 16 channel snake
dbx DriverackPA Mains
dbx 1006 for snare and toms
dbx266XL and dbx Feedback Eliminator and dbx stereo 1/3 Oct EQ
Mains (2) EVqrx/75's and (2) Eliminator Subs through a MT2400 in stereo. I don't bi-amp, but run throught the subs to the mains.
Monitors (4) EV Eliminator Monitors through to Aux Sends through a MT1200 in stereo, one pair per aux send

EV QRX-115/75  Short Term EIA 400 watts, Long Term Peak 1600 watts
EV Eliminator Monitors Short Term EIA 350 watts, Long Term Peak 1400 watts

My intent is to have a smaller set up, no subs no snake, for small clubs, integrated into one rack case that is much smaller than the large set up I use.  I would use the EVqrx 115/75 for the mains and the 4 EV Eliminators for the monitors.  It would also significantly reduce the set up time.

With this more information, which amp would be the best fit for the application?

#5 DGlass

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Posted 01 September 2005 - 09:27 AM

QUOTE(MDArm @ Aug 31 2005, 10:37 PM)
QUOTE(MDArm @ Aug 30 2005, 01:56 PM)
I am putting together a small club PA.  I want to keep it simple - MackieCFX12, DriverackPA, Crown Amp.  I want to run monitors (4 @ 8 ohm each) on one side of the amp and the mains (2 @ 8 ohm each) on the other side.  Which is the best amp to handle the unbalanced load?  My choice would have been a MT2400, which is no longer available.  Which of these other choices would work best, if at all? 
Xs1200
CE4000
K2
View Post

Thanks for the quick response.  The two mains are EV qrx/75 and the 4 monitors are all EV Eliminator Monitors.  Since I am going through only one channel, I am cornered into the same mix for all four monitors.

I currently run a larger system a follows:
MackieCFX16 - 16 channel snake
dbx DriverackPA Mains
dbx 1006 for snare and toms
dbx266XL and dbx Feedback Eliminator and dbx stereo 1/3 Oct EQ
Mains (2) EVqrx/75's and (2) Eliminator Subs through a MT2400 in stereo. I don't bi-amp, but run throught the subs to the mains.
Monitors (4) EV Eliminator Monitors through to Aux Sends through a MT1200 in stereo, one pair per aux send

EV QRX-115/75  Short Term EIA 400 watts, Long Term Peak 1600 watts
EV Eliminator Monitors Short Term EIA 350 watts, Long Term Peak 1400 watts

My intent is to have a smaller set up, no subs no snake, for small clubs, integrated into one rack case that is much smaller than the large set up I use.  I would use the EVqrx 115/75 for the mains and the 4 EV Eliminators for the monitors.  It would also significantly reduce the set up time.

With this more information, which amp would be the best fit for the application?
View Post

According to the specs you have provided two EV/qrx boxes per side of an amplifier would be looking for a single channel of amplification that could do about 1600 watts at 4-ohms (for 3db of headroom ) and should in the range of 1280 to 1920 watts.

Two 8-ohm speakers = 4-ohms

400w ea. x 2 (for 3db of headroom) = 800 watts
800watts x 2 speakers = 1600 watts

1600 x .8 = 1280 watts
1600 x 1.2 = 1920 watts

The four EV monitors would be looking for a single channel of amplification that could do about 2800 watts at 2-ohms and should in the range of 2240 to 3360 watts.

Four 8-ohm speakers = 2 ohms

350w ea. x 2 (for 3db of headroom) = 700 watts
700watts x 4 speakers = 2800 watts

2800 x .8 = 2240 watts
2800 x 1.2 = 3360 watts


If we match up the power for the monitor power requirements you would be looking at either an I-Tech 6000 or a Macro-Tech 5002vz as each will do 2500 watts with a 2-ohm load. I would recommend the I-Tech 6000 as it works with a 20-amp AC receptacle and the MA5k needs a 30-amp receptacle. Knowing most clubs this could be mission critical. Also the I-Tech is lighter. Matching this way, however, would give us a lot more power than we need for the qrx boxes.  sad.gif

Matching up to the qrx boxes power requirements you would be looking at the I-Tech 4000 or the MA-3600vz. Again I would recommend the I-Tech as it works with a 20-amp AC receptacle and the MA3600 needs a 30-amp receptacle. With the I-Tech 4000 you would have a little more than 4db of head room for the qrx boxes. You would, however, now be low on power for the four monitors on one channel with both amps rated 1800 watts at 2-ohms. sad.gif

As mentioned earlier when selecting an amplifier big enough to handle the four monitor speakers, on one channel, we run into the problem of having to much power for the two FOH boxes. sad.gif  When we match up for the two FOH boxes we are underpowered for the monitors. smile.gif  For the best power matching I would recommend you use two amps. This would also give you some redundancy in the system.

With two amps we can recalculate the amp requirements. The qrx boxes would be looking for an amplifier that could do 800 watts per side with an 8-ohm load and should in the range of 640 watts and 960 watts.

8-ohms each
400w ea. x 2 (for 3db of headroom) = 800 watts

800 x .8 = 640 watts
800 x 1.2 = 960 watts


The Monitor speakers could be divided into two speakers per side for a 4-ohm load per side. You would be looking for an amplifier that could do 1400 watts per side with a 4-ohm load and should in the range of 1120 watts and 1680 watts.

Two 8-ohm speakers = 4-ohms

350w ea. x 2 (for 3db of headroom) = 700 watts
700watts x 2 speakers = 1400 watts

1400 x .8 = 1120 watts
1400 x 1.2 = 1680 watts

Now you would be looking at an Xs1200 or even possibly a CE4000 for the qrx boxes. The CE4000 would be slightly below 2 db of head room but would work.  smile.gif

For the monitors you would now be looking at the Xs1200, the CE4000 and the MA-3600vz.  smile.gif