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bajosexto12

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 #1 
Hey guys como andamos, good I hope. Anyways, I have 4 Jbl SR4733x and I was wondering what do I need to bi amp them and also what are the pros and cons. We have a few of the Crown Macro Tech 3600s and 2402s. I was told that to bi amp them I would need two of the 3600s both in Bridge Mono mode. One per pair for the mids and a 2402 for the 4 highs. What I don't know is if the 2402 for the highs has to be set in stereo or bridge mono mode. Im not an audio guy so please help me jeje

Gracias de antemano
Oscar

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Skweezboxmaniac

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 #2 
Yes, the 2402 will run in stereo with both sides of the amp each running a pair 8 ohm compression drivers (4ohms load per side).  The 3600s will be running a pair of mid-sections each also at a total of 4 ohms, but bridge-Mono.  You will need 4 conductor NL4 cables and you may need to make output panels so that each amp's output can go to the proper place within the NL4 connector...but let's leave that for the another discussion should you decide to biamp.

The people you got your information from are correct.  When you biamp, you bypass the internal passive crossover network in the speaker that can rob the system of power and inherently color the frequency response.  You can achieve better filtering through superior external active components for a smoother response and a boost in db SPL when properly configured.  That rig wouldn't sound too bad running passive (not biamped) and you could do it in a pinch, but if you have the stuff to do it, you really should try to do it.  You haven't heard them unless you've heard them properly biamped, filtered and crossed over.

Having said that, you need a Loudspeaker Management processor.  Forget the fact that plain old analog crossovers still exist.  The new DSP devices coming out today are priced cheap enough where there really is no excuse for a cheap analog crossover anymore.

You have MANY choices, but with the components you have, I'd stick with the Harman family and get a dbx Driverack.  The best one for a system like this is the Driverack 260.  It isn't cheap, but allows you a lot of flexibility in getting the system to sound just right where ever you happen to be.  But, seeing as how you say you're not really a sound guy, you can get the Driverack PA+ and not really sacrifice any quality.  Plus, the DRPA+ has a "Wizard" that will walk you through the whole setup process and allow you to just pick the components you have from a menu and it will crunch all the numbers and set the whole thing up for you!  Since you are using JBL/Crown, all the stuff you have is in the wizard already preset ready to go.  You will sacrifice some flexibility and the ability to have a Laptop UI, but I don't think you'll really miss that stuff.  If you want to just "set it and forget it", the DRPA+ is the way to go.  The 260 is for people that want to (and like to) tweak.

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bajosexto12

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 #3 

Yea we have a Driverack 260... I don't mess with it though the engineer does. So two 3600 in Bridge Mono, one per pair of towers and a 2402 in Stereo for the highs, 2 per channel? Then I just need to get the 4 conductor NL4 cables?


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Skweezboxmaniac

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 #4 
Great.  You're good to go then.  Sweet rig.... especially if you have the requisite 4719Xs for the bottoms.

Yes.  4 conductor cables are necessary because the 1+/- pins go to the mids and the 2+/- pins go to the highs on a Neutrik NL4 connector in biamp mode.  You'll need to have a way to send the output of the 2402 to the 2+/- pins and the outputs of the 3600s to the 1+/- pins all on two different connectors (one for left pair another for right pair).  You'll need the short 4 conductor cables as well to jump from one speaker to the other.

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-- Albert Einstein

"Knowledge is learning something everyday. Wisdom is letting go of something everyday."
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bajosexto12

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 #5 
What if I already have four banana cables with the four conductors each? Will I no longer need to acquire the short cables for bridging? I mean can I send the power to each cab each with its own banana cable or do I have to only use one per pair and then bridge them?  
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bajosexto12

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 #6 
That got me lost a little bit. In the beginning it says 1+/- for mids and 2+/- for the highs, the next sentence says send the output of the 2402 thru 1+/- and outputs of the 3600 on 2+/-  Was that a mistake? Backwards?
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MOOKIE_EE

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 #7 
Isn't that 2402 too much power for 2 tweeters ??
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bajosexto12

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 #8 
4 cabs, 4 tweeters
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Skweezboxmaniac

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 #9 
Gahh... my bad.  I fixed it.  You're right I buggered up the order. Usually the lower bandpass goes on the lower numbered pins.  Never seen it otherwise.

And yes, you could use the 4 conductor cables with the 2 bananas on each end on the amp side.  There's nothing really wrong with doing it that way, it's just a thing I have.  I don't like anything except twist lock connectors on speaker runs.  Hence the output panel suggestion...it's neater and more secure.

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Skweezboxmaniac

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 #10 
Quote:
Isn't that 2402 too much power for 2 tweeters ??


As Oscar clarified, it's 4... but yea that's a common thought.  It would seem like it's a lot of power for high frequency compression drivers, but I would actually consider it even slightly underpowered.

The 2447J Compression driver in the JBL SR4733X is rated for 150W RMS @ 16 ohms (I had to look up the impedance, i misquoted it in the first post)
That means each side of the amp is going to see an 8ohm load with two per side. 
The Crown MacroTech 2402 is rated at 505W per side @ 8 ohms (20-20KHz).
Since the rule of thumb is around 2X RMS power rating for the speaker, the amp would need to be ideally rated at 600W @ 8 ohms per side.

Now the reason I don't think that is a problem is because first of all, he has the Driverack 260 which should be set up for proper gain structure, limiting, and filtering.  That helps prevent any harmful square waves produced (due to running out of headroom on the amp) over-voltage, etc... from reaching the driver.  Second, the MacroTech amp is a little more forgiving in this regard and they are great pro amps all around.  And third, the 2402 only has to dedicate all its power to producing high frequencies.  This is easier on the amp than having to deal with a full range signal.

Even though I personally am not a fan of dual 15" cabs (Tejanos LOVE em! ... they're EVERYWHERE).  I've heard similar rigs and they sound nice when set up correctly.

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Aaron

"I must be willing to give up what I am so that I may become what I will be"
-- Albert Einstein

"Knowledge is learning something everyday. Wisdom is letting go of something everyday."
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bajosexto12

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 #11 
Yea that's pretty much all we see here too, 15s. Except for the occasional small line array setup once in a while that just blows us away haha There's and older band here, they carry some of the older SR4731A. 4 of them, the 12s. They run them with two 2402s bridge mono for the mids and what I think is a  Peavey CS800X for the highs. So THAT would be under powering right?
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Skweezboxmaniac

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 #12 
Not necessarily.  Technically, yes...the reserve of clean power could be more ideal.  But think of it this way...

If you had an amp that put out 5 watts into a speaker, you could still get that speaker to a certain volume (db SPL) without distortion.  It probably wouldn't be very loud, of course, but it will still work to some degree.

It's all about knowing your system's limits and working within its boundaries.

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"I must be willing to give up what I am so that I may become what I will be"
-- Albert Einstein

"Knowledge is learning something everyday. Wisdom is letting go of something everyday."
-Zen Proverb
MOOKIE_EE

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 #13 

Squeezbox you're right !!!  We love em.   Here is what were running.   We used to bi-amp but with these newer crossovers,  DBX Driverack +   we just run our sound FULL RANGE.   It's hard to tell the difference.  I might be slightly under powered but it sound awesome.  And since we play Christian Corridos we don't go as loud on our sound.   I'm running 2 QSC RMX 4050hd in stereo for our subs and 2 QSC RMX 2450  for our mids.    This is just the left side the right side is exactly the same.

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Skweezboxmaniac

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 #14 
Wow... do you really hook up all the subs?  How is your mid-range with that rig?  Do you find yourself EQing out a lot of 80Hz-200Hz?  I once played a gig in Florida where the poor sound guy was having a hell of a time controlling feedback and boomy-ness in a tiny club that held about 200 people.  I asked if I could help.  When he nodded his head, I went and unplugged 3 of 6 (six!) Cerwin-Vega Earthquakes that he had setup.  Voila! problems instantly solved and PA sounded great after that.

Not sure if yours is that way, but it looks like there would be an abundance of low end.

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Aaron

"I must be willing to give up what I am so that I may become what I will be"
-- Albert Einstein

"Knowledge is learning something everyday. Wisdom is letting go of something everyday."
-Zen Proverb
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