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Daisy chain JBL STX 818S with XTI4002


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#1 Lowell2k9

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Posted 15 April 2014 - 11:24 AM

Hello all. I've recently purchased a pair of JBL STX818S and have a XTI4002 amp. I believe im under powered here a bit.
#1 Can i daisy chain the JBL STX818s? By doing that will the ohm load drop, is that safe for the amp?  #2 If daisy chaining is
not a good idea. What amp would you recommend for these subs?

#2 dakos

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Posted 15 April 2014 - 12:22 PM

Hello Lowell,
This is actually one of the simplest questions I've had in a long time :-)

You are indeed underpowered, you can work with the XTi 4002, it will be reliable, but you wouldn't utilize your subs to their full potential so that depends on how much low end you need.

What do you usually play through your rig? Dj? live? What kind of live music? Indoor or outdoor?

When you daisy chain 2 similar speakers, you're connecting them in parallel thus halving their impedance. It's not recommended to do that if you go below 8 ohms in bridge mode or below 4 ohms in stereo/parallel mono modes on current Crown amps, there's no reason to anyway.

I'm guessing you wanted to daisy chain them in bridge mode to maximize the amps output, that would put you at 4 ohms, like I said, not recommended.

On top of that, despite the XTi being a great amp, it doesn't excel on sub duty. You could either buy another XTi and connect them in bridge mode, one XTi per 818 or get a proper sub duty amp such as the itech HD 12000 or if used is an option for you the itech 8000 is just as powerful.

What other gear do you have (amps, speakers, processors...)?
Avi

#3 Lowell2k9

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Posted 15 April 2014 - 12:37 PM

Thanks for reply Dakos. I'm a mobile DJ (indoors). Yes I wanted to daisy chain to get max power out of amp using bridge mode. I'll
stay away from that setup tho.  Gear: I have and additional XTI4002, (1) 6002 that im using for SRX722 tops. & 3 QSC PLX3602.
and a driverack pa+.

#4 dakos

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Posted 15 April 2014 - 01:44 PM

I don't know why you have so many amps, are you biamping the 722? Even if you are it sounds like you have too many.

I would suggest you sell ALL your amps AND the DRPA+ and buy two itech amps, the best and most expensive option is to buy 9000HD/12000HD combo or if you're a bit tight on the budget then the least expensive option is to sell the DRPA+ and four amps except for the XTi6002 and buy a used itech 8000 and upgrade later. The processing on the itechs (HD or not) is much better then the DRPA+ and the XTis processing is a tad better so no reason to keep it.

Have you tried a bridged 3602 on each of the 818, this sounds like what you should have done and it might be "good enough"?
Do you live in the US?
Avi

#5 Lowell2k9

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Posted 15 April 2014 - 02:03 PM

Yea i agree, I bought them for other speakers that ive own in the past (azz backwards) .. No im not biamping 722, running in stereo.
That's what ive been thinking here of selling those amps to upgrade. No I havent tried the 3602 in bridge. I will shortly.  Thanks for feedback.

#6 dakos

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Posted 15 April 2014 - 03:54 PM

3 X used QSC PLX 3602 = 3 X $750 = $2250
1 X used XTi 4002 = $700
1 X used XTi 6002 = $1200
1 X used DRPA+ = $250
Total sale: $4450

1 X used i-Tech 6000 for the SRX722 = $1600
1 X used i-Tech 8000 for the 2 X STX818 (will handle up to 4 boxes) = $1800
Total purchase: $3400

You end up with a great upgrade and some cash in your pocket :)

The prices are my estimation by following ebay used amps for a long time.
The newer itech HD option 9000/12000HD is more then twice as the used 6000/8000 option.

Here's one for you at a good price and still under warranty:
http://cgi.ebay.com/...em=390812251653
Avi