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JBL STX-825 Power with ITECH-4000.


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Hello,

I just recently purchased the STX-825 speakers. I currently have the ITECH-4000 Crown Amp. I ried running the STX-825s in steroe mode on the ITECH-4000 (2000W per channel @ 4Ohms) but they sounded too sharp to me. I called JBL and they told me that i was under powering them. They are recommending I run them at 3600W per channel. That is too much power for one speaker.

Q) Am I realy under powering them?

Q) What is the down side of just providing 2000W per channel?

Q) if I buy a bigger amp and provide them with the 3600 am i going to hear more lower frequencies?

any what do you recommendations?

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My professional opinion...

 

1. 2000 watts per box is plenty. There is little to nothing to be gained by powering higher and lots to be lost.

 

2. There really is no practical real world downside. Not in the real world that most of us operate in.

 

3. A bigger amp is not going to do anything for the lower frequencies. Your box is limited based on the design. If you need more low end, you need to add the matching subs to the system.

 

4. The "sharpness" that you hear has nothing to do with the amp power. Of course they would like to sell you a bigger amp because that means they make more money, and that's the company way. Have you loaded the proper JBL factory preset processing into the DSP on your amp? This is the most important thing that you can do to improve your sound and get the maximum potential from your new speakers.

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I run 4 SRX 715's and sometimes 4 718's off one ITech 4000 and it sounds great. I'm not familiar with the new STX series, but can't believe they would be much different from the SRX series.

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Folks,

Thanks you for your responses.

agedhorse, I agree with you that 2000 W is plenty to run into one speaker. but when I called JBL they told me that by underpowering them (i.e below the rated 3200W) I am running them at the risk of damaging them. Is that true?

As for the tunings, JBL has not yet provided any tunings on thier website. I have a Drive Rack PA+ and once the Tunings are out. I will configure them into the DRPA+.

Do you guys recommend that or should I just use my amps to tune and cross over the system?

As for the subs, I do have a pair of the EV QRX 218 which sound great with the STX when I run them.

 

Thanks.

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agedhorse, I agree with you that 2000 W is plenty to run into one speaker. but when I called JBL they told me that by underpowering them (i.e below the rated 3200W) I am running them at the risk of damaging them. Is that true?


Thanks.

 

 

IMO (and this is a professional opinion), JBL/Harman has done a great disservice by promoting such high power recommendations but this has certainly improved my reconing business as the number of "unfortunate lacks of good judgement" has increased the number of damaged drivers considerably. If everything is configured perfectly, you have the proper (and verified with test equipment) dynamic protection, HPF's, etc AND you don'y have somebody who lacks good judgement AND you always bring enough rig for the gig, powering at 3200 watts can be acceptable. The problem is that 99% of their users fail in one or all of the above which under warranty terms constitutes misuse and/or abuse.

 

One conflict that may explain why they do this is that they also sell amps under the Crown brand, and when the amps are seperate from the speaker, it's MUCH easier to disclaim responsability for warranty coverage under an overpower incident. On the other hand, with their self powered where JBL is kind of "married" to the whole product, under technical analysis they generally power with a little over the RMS (or continuous) rating of the drivers, have all of the necessary protection built in so that the user "can't" make mistakes that would result in a warranty claim. Their engineers have a pretty good grasp of the real world failure potential, but where the marketing folks can get away with exaggerating, they do in spades.

 

This is the classic case of do as they do not as they say.

 

Incidently, this is not true just of Harman products, many manufacturers fall into this trap.

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Hello,

I just recently purchased the STX-825 speakers. I currently have the ITECH-4000 Crown Amp. I ried running the STX-825s in steroe mode on the ITECH-4000 (2000W per channel @ 4Ohms) but they sounded too sharp to me. I called JBL and they told me that i was under powering them. They are recommending I run them at 3600W per channel. That is too much power for one speaker.

Q) Am I realy under powering them?

Q) What is the down side of just providing 2000W per channel?

Q) if I buy a bigger amp and provide them with the 3600 am i going to hear more lower frequencies?

any what do you recommendations?

I was able to find SRX processor settings at dbxpro.com

That is as far as I dug into this.

Hard to believe they would not release processor settings on this line of loudspeaker or any of their pro loudspeakers for that matter

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IMO (and this is a professional opinion), JBL/Harman has done a great disservice by promoting such high power recommendations but this has certainly improved my reconing business as the number of "unfortunate lacks of good judgement" has increased the number of damaged drivers considerably. If everything is configured perfectly, you have the proper (and verified with test equipment) dynamic protection, HPF's, etc AND you don'y have somebody who lacks good judgement AND you always bring enough rig for the gig, powering at 3200 watts can be acceptable. The problem is that 995 of their users fail in one or all of the above which under warranty terms constitutes misuse and/or abuse.


One conflict that may explain why they do this is that they also sell amps under the Crown brand, and when the amps are seperate from the speaker, it's MUCH easier to disclaim responsability for warranty coverage under an overpower incident. On the other hand, with their self powered where JBL is kind of "married" to the whole product, under technical analysis they generally power with a little over the RMS (or continuous) rating of the drivers, have all of the necessary protection built in so that the user "can't" make mistakes that would result in a warranty claim. Their engineers have a pretty good grasp of the real world failure potential, but where the marketing folks can get away with exaggerating, they do in spades.


This is the classic case of do as they do not as they say.


Incidently, this is not true just of Harman products, many manufacturers fall into this trap.

 

 

Thanks for the response. I guess that yo uare answering my question indirectly, but I just wanted to ensure that under powering these speakers is NOT a direct cause of damaging them. Right?

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The SRX tunings are available on the JBL and DBX sites. the STX is not yet available. When I asked JBL they said it will be soon. I will try to use the SRX tunings but I noticed that the horn cross over point for the STX is higher than the horn on the SRX.

Also, should I use BRPA+ or should I eliminate it and use the DSP on th eamps?

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Use the ITech processing. It is much more powerful and has much better limiting capabilities. You will need to download Systems Architect to a laptop or computer and enter the processing into the amp. Are you biamping the STX?

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The SRX tunings are available on the JBL and DBX sites. the STX is not yet available. When I asked JBL they said it will be soon. I will try to use the SRX tunings but I noticed that the horn cross over point for the STX is higher than the horn on the SRX.

Also, should I use BRPA+ or should I eliminate it and use the DSP on th eamps?

 

 

Dont' worry about this if you are running the boxes passive. The internal crossovers should work fine. What you need to worry about is your HPF's for both your subs and tops.

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I was running a pair of SRX722's off a single stereo PLX3402. That's 1100w per box and had plenty of headroom. I guess according to JBL I should have cooked them! LOL

 

 

+ 1! I had to run my 722's off a QSC RMX 2450 last month outside in 105 degrees for 3 hours! Somehow everything was fine?

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I was running a pair of SRX722's off a single stereo PLX3402. That's 1100w per box and had plenty of headroom. I guess according to JBL I should have cooked them! LOL

 

 

JBL has NEVER claimed that under powering a cab would "cook" them. That is simply your misinterpretation of their reccomendations.

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JBL has NEVER claimed that under powering a cab would "cook" them. That is simply your misinterpretation of their reccomendations.

 

 

I was told this same thing by a salesman when a Crown XLS402 failed on me a couple of years ago. Apparently, it's something that the Harman corp has adopted as a general line of defense.

 

I've still never figured out how "underpowering" a cabinet could cause the amp to fail.........

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I was told this same thing by a salesman when a Crown XLS402 failed on me a couple of years ago. Apparently, it's something that the Harman corp has adopted as a general line of defense.


I've still never figured out how "underpowering" a cabinet could cause the amp to fail.........

 

 

It's a profitable position IF you also happen to be an amp manufacturer. QSC is no better from this perspective IMO BUT they too power their own powered speakers at slightly more than the continuous rating of the drivers and that's also with factory engineered protective processing. The real engineers are not dumb but some of them get their balls crushed by the marketing folks and if they want a job they have to play by the company rules. Marketing engineers are a whole different breed.

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JBL has NEVER claimed that under powering a cab would "cook" them. That is simply your misinterpretation of their reccomendations.

 

 

This:

 

http://www.jblpro.com/BackOffice/ProductAttachments/lowpower.pdf

 

Is close enough to saying that to get a lot of people in trouble. In theory, that are correct, in practice with non-professional users, they are not.

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