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Author Topic: JBL SRX-728 or EV QRX-218? Which best for my music style?  (Read 36765 times)

Tom Reid

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Re: JBL SRX-728 or EV QRX-218? Which best for my music style?
« Reply #10 on: October 06, 2009, 01:50:25 pm »

Adam Schaible wrote on Tue, 06 October 2009 12:48

What I'm getting at is more than 3kw what?  Peak, RMS?

It's a weird thing to say - 3kw RMS would be way over the peak rating of the cab assuming a 6db crest factor (which it's probably closer to 10db on average).

The thermal rating on the drivers is 800w based on a 6db crest (if memory serves me correctly).


SRX728 is rated 1600/3200/6400.
SRX718 is rated 800/1600/3200.
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Adam Schaible

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Re: JBL SRX-728 or EV QRX-218? Which best for my music style?
« Reply #11 on: October 06, 2009, 01:52:32 pm »

Right, so the thermal is 800w per driver
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Tom Reid

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Re: JBL SRX-728 or EV QRX-218? Which best for my music style?
« Reply #12 on: October 06, 2009, 02:50:12 pm »

Adam Schaible wrote on Tue, 06 October 2009 12:52

Right, so the thermal is 800w per driver


Yup, and *2 would equal 1600w thermal.

JBL offers an amp in their VRX918P.
The amp peaks at 1500w.
The 918 is a single 2268H (same as the 718/728).
So if we doubled a 918 cabinet it would be a 728 cabinet give or take a few cabinet tuning features.
And if we doubled the 918 power it would be 3kw peak.
I do 3200 peak give or take.
2000w peak just didn't have the stopping power, left me dull, lifeless, in need of more quiet in-between my boom.
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Vinny D'Agostino

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Re: JBL SRX-728 or EV QRX-218? Which best for my music style?
« Reply #13 on: October 06, 2009, 03:00:49 pm »

I have been very pleased with my QRX218s subs, I have them powered with a QSC RMX4050HD run in dual mono (1400w ea. sub @ 4ohms).
They get more then loud and low enough for the venues I work in.

Adam Schaible

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Re: JBL SRX-728 or EV QRX-218? Which best for my music style?
« Reply #14 on: October 06, 2009, 03:04:22 pm »

2Kw is serious power.  I don't disbelieve the results you have had, but I would be very surprised if they were strictly voltage based.

I'm using the I-Tech 5000Hd's on them and they really move air.  They peak at 3200w or so burst, rated at 2500w.  When I'm monitoring the amps input/output, I rarely see it get close to -3db.  At -3db, the output is intense.  According to the specs of the amp, this is just 1250w.

I can set the I-Tech to not clip the output stage and drive it harder and harder.  I'll give that a shot and see if it keeps getting louder until it limits (100v).  I've never really worried about it before - but it might be worth checking out.
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Dave Rickard

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Re: JBL SRX-728 or EV QRX-218? Which best for my music style?
« Reply #15 on: October 06, 2009, 03:10:49 pm »

How many are you going to use?
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Dave
Yorkville dealer

"The wrong piece of gear, at the right price, is still the wrong piece of gear."

"If you don't have good stuff at each end of the signal chain, (mics and speakers) what you use in between is just turd polish."--Dave Dermont

Brian Wynn

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Re: JBL SRX-728 or EV QRX-218? Which best for my music style?
« Reply #16 on: October 06, 2009, 03:29:07 pm »

I have owned both SRX and Currently QRX.  If your playing that "music" that I heard on the video then I would go with the LAB subs they go low and are very loud.  The tuning of the LAB box will help you get into that lower 808 stuff.  Just my 2 cents.
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Brian Wynn
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jack smith

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Re: JBL SRX-728 or EV QRX-218? Which best for my music style?
« Reply #17 on: October 06, 2009, 04:22:32 pm »

To Tom Reid,

What do you mean 2k is asking for heat? I've been told by people on this very forum (cant remember who) that 2k each sub is about right. Any more than that and its too much power for the seriously bass heavy music i'll be playing through them. I always set system gain structure by using a pink noise test tone and making sure all equipment clips at the same level, then back off on the 1st piece of equipment to 0db on the mixer, and then not exceed that level all night. Surely 3k into an SRX-728 while playing the kind of music i'll be playing is way too much power.

If I set the gain structure, then keep the level at or below  all night, but...I put 3000k through each sub, it'll blow them to bits wouldnt it?
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Adam Schaible

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Re: JBL SRX-728 or EV QRX-218? Which best for my music style?
« Reply #18 on: October 06, 2009, 04:34:53 pm »

I don't think 3k peak is too much - 3k RMS is, but you really can't run 3k RMS with any production amp outside an ITech 12000HD and you need electricity in the grid to support it.

The point I'm making is that 3k watts is only 1.5 db more than 2k watts.  To get 3k watts from a 3k amp is basically on the edge of clipping, so you're probably getting 1500-2k watts from a 3kw amp.
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Tom Reid

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Re: JBL SRX-728 or EV QRX-218? Which best for my music style?
« Reply #19 on: October 06, 2009, 05:33:37 pm »

Adam Schaible wrote on Tue, 06 October 2009 15:34

I don't think 3k peak is too much - 3k RMS is, but you really can't run 3k RMS with any production amp outside an ITech 12000HD and you need electricity in the grid to support it.

The point I'm making is that 3k watts is only 1.5 db more than 2k watts.  To get 3k watts from a 3k amp is basically on the edge of clipping, so you're probably getting 1500-2k watts from a 3kw amp.


Subsequently IF using a 2k amp you're getting 750-1.5k watts.
Now do ya see my point?
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