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Author Topic: Crown XTI & JBL 725 Biamp  (Read 7333 times)

Robert Conner

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Crown XTI & JBL 725 Biamp
« on: August 23, 2011, 09:14:21 am »

Hello all!

I am 'rediscovering' the joys of setting up a new system after a 15 year absence from the sound system community.

I'm the director of a new outdoor ribfest in Omaha, Nebraska and I have the personal budget to buy, instead of rent, the PA for the music part of the festival.  I'll be buying just the PA - no monitors or lighting or mic's, etc.  Those things I WILL rent for the 3 day festival.

The 'starter system' I'm building will be comprised of 4 JBL SRX 725's and 2 JBL SRX 728S per side.  The amplifiers will be XTI 4000 and XTI 2000 - 2000's for the horns of the 725's and 4000's for each of the mids and sub  sections.

I just unwrapped my XTI 4000's, downloaded both Band Manager and the JBL presets and have already hit a snag.  Band Manager wants to run each 4000 as a 2 channel amp, with channel 1 for the mid/lows and channel 2 for the highs.  I want to run each amp in stereo/2 channel mode, each one dedicated to mids OR highs without using an external crossover.

What am I missing?

Robert Conner
www.aksarbenribfest.com
Omaha, Nebraska
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Todd Novosad

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Re: Crown XTI & JBL 725 Biamp
« Reply #1 on: August 23, 2011, 06:41:16 pm »

click on the 'independent' tab in the xover section.  you can set LP and HP for each channel separately, as well as choose the slopes for each.

edit... sorry, this would be in System Architect 3.  Try it if you can't find a solution in Band Manager.

http://hiqnet.harmanpro.com/
« Last Edit: August 23, 2011, 06:42:51 pm by Todd Novosad »
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Steven Gustafson

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Re: Crown XTI & JBL 725 Biamp
« Reply #2 on: August 24, 2011, 09:32:28 am »

Robert,
I know you're under a budget, but read some facts about low amplifier power.  Pat Brown of AudSynCon has some good reading.  JBL has a white paper about the dangers of low amplifier power.  Many others besides myself here would agree, XTI is short of correctly powering SRX models.  Also consider reading some interesting stuff from Lab Gruppen.  I know it's alot more money, but consider IT-5000HD or MA-5000 at minimum.  I just don't want to see you burn your coils being under powered.   Good luck.


Hello all!

I am 'rediscovering' the joys of setting up a new system after a 15 year absence from the sound system community.

I'm the director of a new outdoor ribfest in Omaha, Nebraska and I have the personal budget to buy, instead of rent, the PA for the music part of the festival.  I'll be buying just the PA - no monitors or lighting or mic's, etc.  Those things I WILL rent for the 3 day festival.

The 'starter system' I'm building will be comprised of 4 JBL SRX 725's and 2 JBL SRX 728S per side.  The amplifiers will be XTI 4000 and XTI 2000 - 2000's for the horns of the 725's and 4000's for each of the mids and sub  sections.

I just unwrapped my XTI 4000's, downloaded both Band Manager and the JBL presets and have already hit a snag.  Band Manager wants to run each 4000 as a 2 channel amp, with channel 1 for the mid/lows and channel 2 for the highs.  I want to run each amp in stereo/2 channel mode, each one dedicated to mids OR highs without using an external crossover.

What am I missing?

Robert Conner
www.aksarbenribfest.com
Omaha, Nebraska
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Steven Gustafson

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Re: Crown XTI & JBL 725 Biamp
« Reply #3 on: August 24, 2011, 09:48:17 am »

http://www.jblpro.com/catalog/support/getfile.aspx?docid=246&doctype=3
or
http://www.prosoundweb.com/article/it_depends_deciphering_amplifier_power_ratings/
or
http://www.electrovoice.com/sitefiles/downloads/Safely%20Driving%20Your%20Sound%20System%20v2.1.pdf

Either way, if you're stuck with XTI, do NOT run the amps into clipping.  It's a sure bet, you'll learn who the best re-coners are in your area.  Another thing, be careful if you are using only one amp channel or a bridged amp into two SRX 725 cabinets.  2 ohm loads are hard on the amp.
Again good luck.

Hello all!

I am 'rediscovering' the joys of setting up a new system after a 15 year absence from the sound system community.

I'm the director of a new outdoor ribfest in Omaha, Nebraska and I have the personal budget to buy, instead of rent, the PA for the music part of the festival.  I'll be buying just the PA - no monitors or lighting or mic's, etc.  Those things I WILL rent for the 3 day festival.

The 'starter system' I'm building will be comprised of 4 JBL SRX 725's and 2 JBL SRX 728S per side.  The amplifiers will be XTI 4000 and XTI 2000 - 2000's for the horns of the 725's and 4000's for each of the mids and sub  sections.

I just unwrapped my XTI 4000's, downloaded both Band Manager and the JBL presets and have already hit a snag.  Band Manager wants to run each 4000 as a 2 channel amp, with channel 1 for the mid/lows and channel 2 for the highs.  I want to run each amp in stereo/2 channel mode, each one dedicated to mids OR highs without using an external crossover.

What am I missing?

Robert Conner
www.aksarbenribfest.com
Omaha, Nebraska
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Tim McCulloch

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Re: Crown XTI & JBL 725 Biamp
« Reply #4 on: August 24, 2011, 10:26:47 am »

http://www.jblpro.com/catalog/support/getfile.aspx?docid=246&doctype=3
or
http://www.prosoundweb.com/article/it_depends_deciphering_amplifier_power_ratings/
or
http://www.electrovoice.com/sitefiles/downloads/Safely%20Driving%20Your%20Sound%20System%20v2.1.pdf

Either way, if you're stuck with XTI, do NOT run the amps into clipping.  It's a sure bet, you'll learn who the best re-coners are in your area.  Another thing, be careful if you are using only one amp channel or a bridged amp into two SRX 725 cabinets.  2 ohm loads are hard on the amp.
Again good luck.

<SIGH>

We've had this discussion several times.  Clipping, in and of itself, does NOT kill speakers.  Overvoltage and mechanical over excursion kill speakers.  Period.
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Tim Burkhart

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Re: Crown XTI & JBL 725 Biamp
« Reply #5 on: August 24, 2011, 06:02:01 pm »

If you are careful, and don't get too aggressive, the power you are using will be fine. Don't expect the same results that Midwests KF750 rig or Audio Visions Vertec rigs will get you in Omaha. Set the limiters on the XTI's. They seem to be pretty decent (I would have looked at the XTI'2's though).

BTW, the best reconer is Midwest in Omaha because I am the JBL transducer tech there and I've been at this audio thing for over 30 years. ;)
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Doug Fowler

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Re: Crown XTI & JBL 725 Biamp
« Reply #6 on: August 24, 2011, 06:35:12 pm »

If you are careful, and don't get too aggressive, the power you are using will be fine. Don't expect the same results that Midwests KF750 rig or Audio Visions Vertec rigs will get you in Omaha. Set the limiters on the XTI's. They seem to be pretty decent (I would have looked at the XTI'2's though).

BTW, the best reconer is Midwest in Omaha because I am the JBL transducer tech there and I've been at this audio thing for over 30 years. ;)

"Burtim", please read the rules and fix your display name.

Thank you for your cooperation.

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Jamin Lynch

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Re: Crown XTI & JBL 725 Biamp
« Reply #7 on: August 24, 2011, 07:00:20 pm »

Hello all!

I am 'rediscovering' the joys of setting up a new system after a 15 year absence from the sound system community.

I'm the director of a new outdoor ribfest in Omaha, Nebraska and I have the personal budget to buy, instead of rent, the PA for the music part of the festival.  I'll be buying just the PA - no monitors or lighting or mic's, etc.  Those things I WILL rent for the 3 day festival.

The 'starter system' I'm building will be comprised of 4 JBL SRX 725's and 2 JBL SRX 728S per side.  The amplifiers will be XTI 4000 and XTI 2000 - 2000's for the horns of the 725's and 4000's for each of the mids and sub  sections.

I just unwrapped my XTI 4000's, downloaded both Band Manager and the JBL presets and have already hit a snag.  Band Manager wants to run each 4000 as a 2 channel amp, with channel 1 for the mid/lows and channel 2 for the highs.  I want to run each amp in stereo/2 channel mode, each one dedicated to mids OR highs without using an external crossover.

What am I missing?

Robert Conner
www.aksarbenribfest.com
Omaha, Nebraska


4-SRX725's per side?
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Mike Christy

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Re: Crown XTI & JBL 725 Biamp
« Reply #8 on: August 24, 2011, 08:49:22 pm »

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Randall Hyde

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Re: Crown XTI & JBL 725 Biamp
« Reply #9 on: August 25, 2011, 07:15:20 am »

It's a ribfest.

(I assume you're talking about the nulls and lobes, not the event) :)

To the OP:
Putting four SRX725s on each side is going to be self-defeating. I've modeled it and I can't get anything good from the models. I have modeled three cabinets per side with the center cabinet at 0 degrees (pointing straight at the audience) and the left/right cabinets at 45 degrees and -45 degrees (cross-fired). The result isn't as good as two cabinets, but the cancellation is probably acceptable for a multi-speaker arrangement. You can find the SPL field graphs here:
http://homepage.mac.com/randyhyde/webster.cs.ucr.edu/AudioStuff/3Cabs.html

The only way I could see 4 cabs per side working is if they're all splayed; still you'll get a lot of interference in FOH. If you really need to use 8 cabinets, I'd recommend two per side (cross-fired) and then two pair as delay stacks.

Honestly, I think you'd do better with twice as many subs and half the tops.
And be sure the subs are all together, not split on each side of the stage.
Cheers,
Randy Hyde


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ProSoundWeb Community

Re: Crown XTI & JBL 725 Biamp
« Reply #9 on: August 25, 2011, 07:15:20 am »


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