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QSC MX1500a or RMX2450 for JBL2226H ?

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sicoroots View Drop Down
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    Posted: 21 February 2017 at 5:37am
hello community

I've been building my first soundsystem in the last weeks, so far I have completed 2 Cubo 15 extended design with a 15" JBL 2226H 600W 8ohm driver.

Trying to understand what would be the best solution to power them.

They will be connected in parallel.

One option i'm thinking about is using a QSC MX1500A ,which I own already, and running it in bridged mono with its 1500W at 4ohm.
This will give me a bit of headroom over the 600w x 2 of the drivers although it may not be a lot.

In stereo mode the amp will have only 400W  at 8ohm ,not enough for the two 600W / 8ohm JBL.

I have also available a QSC RMS2450 , in stereo 650W at 8ohm / 450 W at 4ohm....falling short here too
In bridge mode it goes up to 2400W at 4ohm which is double the power of the JBL combined.

I've tested the speakers as part of a 3 way system with the help of a friend , the Cubo were run in parallel stereo and powered by a QSC PLX2402 which has 700W in stereo mode at 4ohm.
Used as the bass part of the system , the overall sound result was good...the amp driving the Cubos wasn't clipping or distorting of any kind...

any thought on it would be greatly appreciated...

bless
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Elliot Thompson View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 21 February 2017 at 6:10am

Hi.

 

If you Bridge the QSC MX 1500 amplifier, you will attain 1500 watts (750 watts per driver) @ a 4-ohm load. The JBL 2226 maximum power is 600 watts. JBL never recommended anything beyond 600 watts. A lot of people assumed they could feed the 2226 two times their Program Rating and ended up destroying them during the process.

 

Going from 750 watts per driver to 1200 watts per driver yields only a 2 dB gain which falls under a little bit louder from your ear's perspective. However, you do have a higher probability of damaging the woofers during the process. 

Best Regards, 



Edited by Elliot Thompson - 21 February 2017 at 6:13am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sicoroots Quote  Post ReplyReply Direct Link To This Post Posted: 21 February 2017 at 9:23pm
Hi Elliot ,


thanks a lot for the reply...this actually makes more sense in the light of the testing I did with my friend and the sound results using the QSC PLX2402 in stereo with 700W @ 4 Ohm load....

Do you think it would be better to use the QSC RMX 2450 in stereo with its 450/500W @ 8ohm and use right and left channel to power up each JBL ?

or...If I run it at 4 ohm with the 2 JBL connected in parallel it goes up to 650W but that would be around 325W per driver...which is more or less what we fed them with during the test with the QSC PLX2402...

thanks!


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Post Options Post Options   Thanks (0) Thanks(0)   Quote _djk_ Quote  Post ReplyReply Direct Link To This Post Posted: 22 February 2017 at 1:21am
The JBL VGC power ratings are dependent on cone travel pumping air through the structure for cooling.

I have seen the 2226 burn the ends of the coil (middle part still copper colored) when used above 80hz with only 450W on them.
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Elliot Thompson View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 22 February 2017 at 3:57am

Instead of worrying about how much power you can step down to, ask yourself how many times have you seen the clip light activated during your events.

If the clip light is never on using the RMX 2450 in stereo mode, you can feed loudspeakers without fear of damaging them. If you periodically, or constantly clipping the RMX 2450 in stereo mode, you need more headroom for the amplifier needs to play at maximum levels in order to attain the sound pressure levels you are trying to accomplish. 

The whole idea of bridging the MX 1500a is to have 500 watts of non-clipped power at your disposal with, 250 watts of headroom just in case it is needed for musical peaks under a longterm basis. With the RMX 2450, it will be 450 watts of clipped power if you find yourself periodically or constantly clipping the RMX 2450 in stereo mode.

Best Regards,  



Edited by Elliot Thompson - 22 February 2017 at 3:58am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sicoroots Quote  Post ReplyReply Direct Link To This Post Posted: 22 February 2017 at 5:12pm
ok thanks for the comment, I will keep an eye on it and try different configuration.

on next event we'll be running them out of the PLX2402( in stereo @ 4ohm ) which has more or less same power rating as the RMX2450. 700W @ 4ohm, so about 350W per driver.
The RMX2450 is just slightly below that.

which is the set up used during the test few days ago. There wasn't clipping signals on and sound wise we were satisfied.

My main focus is trying to reduce the amount of amps I need to bring with me at a regular event I do once a month as everything will need to be loaded in a car...

This is also driving the type and size of speakers I will use. So far Cubo15 seems a good match for the bass part but depending on the sound results at the venue I may step down to cubo 12 and add some 12" kicks on top with compression drivers.

still a work in progress...


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Post Options Post Options   Thanks (0) Thanks(0)   Quote sicoroots Quote  Post ReplyReply Direct Link To This Post Posted: 22 February 2017 at 5:15pm
I see...hope this is not going to happen to us !

I've been reading about the robustness of the JBL drivers , this is something the surprises me
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Marko Quote  Post ReplyReply Direct Link To This Post Posted: 22 February 2017 at 7:38pm
QSC MX 1500 will overheat when used on 4 ohm/bridge.
If I remember correctly since I did not used one since 1998.
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