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I-Tech 4000 versus K2


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#1 mcangelo

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Posted 09 November 2005 - 12:52 PM

Hi to all,

Just to let everyone know, I've always used Crown amps and will continue to use them.

My problem is this....I recently purchased a pair of JBL SRX715's (800 watts RMS in 8ohms)....originally I thought I could power them using a Crown K2 (500 watts in 8 ohms stereo) in stereo......I'm a mobile DJ....hence I play top 40's music....sometimes such music can be very bass heavy. The few times I've used the K2 I found that it would peak rather quickly...hence I purchased an I-tech 4000 (1250 watts in 8 ohms stereo) believing that it would have enough power to drive these speakers. To my amazement.....I've found that the I-tech 4000 was not more powerful....peaking at the same levels, I use a mackie 1402vlz pro console. I even compared the k2 versus the I-tech 4000 in my warehouse (a side by side comparison) in stereo and found that the difference was so minimal that I've come to the conclusion that the I-tech 4000 does not have 1250 watts per channel in 8 ohms stereo.

Both amps were driven at 1.4 volts with gain set to maximum with no processors...straight power. And AC power from the wall is 120volts....15 amps (AC should not be the problem)

I've only just purchased the I-tech 4000....hence is there something i'm doing wrong??? I'm relying on my ears....no technical instruments.

Any help would be appreciated!
Angelo

#2 guyofsound

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Posted 09 November 2005 - 07:11 PM

i think that your under the impression that the bigger amp means your not going to clip ever. the only thing the bigger amp does is give you better clean power you can still clip any amp no matter what size if the speakers aren't able to put out what you want and your triing push it to get it, it will clip and eventually blow up.
the way power works you have to increase the power by double in order to get an increase of 3db which is barely noticeable. if you double the speakers you can also make the volume increase by 3db. the other thing you might want to try is putting them right beside each other in a line you will get a coupling effect and get an extra 6db.  huh.gif

jim

QUOTE(mcangelo @ Nov 9 2005, 01:52 PM)
Hi to all,

Just to let everyone know, I've always used Crown amps and will continue to use them.

My problem is this....I recently purchased a pair of JBL SRX715's (800 watts RMS in 8ohms)....originally I thought I could power them using a Crown K2 (500 watts in 8 ohms stereo) in stereo......I'm a mobile DJ....hence I play top 40's music....sometimes such music can be very bass heavy. The few times I've used the K2 I found that it would peak rather quickly...hence I purchased an I-tech 4000 (1250 watts in 8 ohms stereo) believing that it would have enough power to drive these speakers. To my amazement.....I've found that the I-tech 4000 was not more powerful....peaking at the same levels, I use a mackie 1402vlz pro console. I even compared the k2 versus the I-tech 4000 in my warehouse (a side by side comparison) in stereo and found that the difference was so minimal that I've come to the conclusion that the I-tech 4000 does not have 1250 watts per channel in 8 ohms stereo.

Both amps were driven at 1.4 volts with gain set to maximum with no processors...straight power. And AC power from the wall is 120volts....15 amps (AC should not be the problem)

I've only just purchased the I-tech 4000....hence is there something i'm doing wrong??? I'm relying on my ears....no technical instruments.

Any help would be appreciated!
Angelo
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#3 Bud Bolf

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Posted 10 November 2005 - 08:24 AM

Howdy,
A few thoughts come to mind.
Since the K2 is 500 watts @ 8ohms and the I-tech is 1250 watts @ 8ohms
you have more than doubled your Power to cab scenario by 1.5x's.
Which is a move in the right direction.

The I-Tech's have DSP (Digital Signal Processing) that the K2 does not.
If I read your post correctly, you are running your Signal directly from your Mackie
mixer to the Amp and on to the Speakers. No outboard Signal processing in place until you got the I-Tech.
Have you set up the DSP in the I-Tech for your Speakers?
Also since I am not familiar with the I-Tech DSP, but if it is anything like a DriveRack it may have your JBL Speaker settings installed, again I do not know.
A Crown rep or others that use I-Tech's can jump in here.

My thoughts are maybe that the DSP is set in a manner that will not let the I-Tech
perform to it's potential. Also even with full range, you will still need to set the I -Tech per your Speakers specs, ie. Filters

Another thought on stacking speakers (side by side or one over the other) is that you need to find out what the Horn and speaker dimensions (Dispersion) are outside the speaker cab, JBL would be great for that.
You would not want to stack two speakers (side by side) with wide dispersion horns say 60X90 because the Horns would cross into each other causing Freq cancellations. Even over each other the top Horn from the lower speaker cab and the lower Speaker from the top cab above can get into it.
They will fight for Freq. control and cause cancellations, not good.
Some speakers are plain and simple not meant to be in a stacked array.
This is something that you decide on when purchasing speaker cabs, how will they be used and setup.

Another thing to consider is Speaker cab SPL (sound pressure level) and what your cabs are rated at. This is kind of an efficiency rating.
I have heard great things about the new JBL SRX725's and that they really kick!
Besides throwing money at the Power end, look at the Speaker cab end,
and will it and or was it designed to perform to the specifications that you want?

The match of Power Amp to Speaker cab is the marriage of choice in "Live Sound"
JBL does list the prefered match of Power Amp rating to this speaker.
If you have matched that and you are still not satisfied, then you need to look elsewhere for your answers.
Power is Power and once you are there (as in the I-Tech, which is a great Amp and you should keep it!! I wish I could afford one) then you need to start backwards and re-check everything about your SETUP!

Good Luck, just my 2c, hope it helps,
      Bud

#4 mcangelo

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Posted 10 November 2005 - 11:44 AM

Hi all,

Thanks for the replies.....I was hoping to get someone from Crown to give me a more specific response!

Furthermore, I must add that when doing the comparison with the K2 versus the I-tech 4000....I went a step further.....I bridged mono the K2 hence giving me 1500 watts in 8 ohms and compared that to a stereo channel of the I-tech 4000 which gives 1250 watts in 8 ohms. Hence K2 bridged mono on 1 speaker (left channel) and I-tech 4000 stereo on 1 speaker (right channel). To my ears the K2 with a difference of 250 watts in 8ohms...was much louder!

How could this be??? Someone from Crown help?

Thanks,
Angelo

#5 helicool

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Posted 10 November 2005 - 04:27 PM

Mcangelo -

I found the complete oposite to what you are saying -

How many boxes in total do you have to run?

If you are only using a total of (2) Of the JBL SRX715's, I think I have good news for you.

If you use a 4-conductor speakon cable with 4-conductor cable, swith the speakers to "biamp" mode [http://www.jblpro.co...x700/BiAmp.htm] and use the DSP inside the IT4K, I think you'll be very happy with the results, although it would be in mono.

In theory, you would have 2000W available to your Lo's and 2000W available to your hi's and you could use the DSP inside the amp.

You can follow the DSP settings from http://www.jblpro.co...700 ...260 (PDF).pdf and all should sound great.

***NOTE: NON-TECHNICAL OPINION TO FOLLOW***
On a side note, myself as well as many others that use my rig w/ IT's have all come to the same conclusions - these amps are very "clean" and "accurate" sounding, and unlike the K2 don't get a little "dirty" when you push them - that "dirt" can make things sound bigger and louder then they actually are - maybe this is what you are hearing as additional volume? (every once-in-a-while, I enjoy subs running off a nice, old,heavy Macro5000, and while I wouldn't want to move them around, they sure do sound nice!)

I'm sure you'll come around to the IT's - It may take a while for you to realize what you've got in that nice, light 2U package......


Ryan

#6 MichaelsAudio

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Posted 03 February 2006 - 05:06 AM

Here you may have missed something entirely.  Your JBL Mid/High Boxes are being used in "Passive" Mode.  In this case you will run into the limit that the passive crossover network can take before the sound pressure level drops off and any more power is just turned into heat.  Using the I-Tech 4000 DSP you could convert your system to Bi-Amped and get loads more gain and clarity.  However, one I-Tech 4000 could safely drive a maximum of three JBL-725s and would be in mono, (only one signal line to the I-Tech).  In our JBL700 system here we have Six 725s and Four 728s though we drive them all with QSC 3400s and are using an analog crossover network.  We would love to upgrade to the I-Tech amps for this "B" Rig.     Michael Oliver - Prime Time Entertainment, Tracy, CA