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XTI limiter question...


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#1 dakos

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Posted 24 September 2011 - 05:08 AM

Hello,
I keep reading that XTI series amps have a problematic limiter operation scheme meaning that the first step when the limiter kicks in is -3db and it's audible for everyone, especially on sub duty but for tops as well.
Doe's the newer PeakX limiters solve this issue? How are they different from the older XTI limiters?

How are the limiters on the i-tech/i-tech HD's different from those on the XTI/XTI2?

What I plan to do is run four old Cerwin Vega ProStax series II (the specs are at the bottom of the page) as my tops on a single XTI 4002
I didn't know which sub and amp combo to get, I need something that sounds great and that would be easy to upgrade so after allot of reaserch I want to get one used IT9000HD or IT6000 (I need the DSP) to power one cab of JBL SRX728, I'm on 240V if it matters.

Am I overpowering things? Would the XTI 6002 be enough for sub duty considering the problematic limiters?

Thank you

#2 Kevin Heber

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Posted 26 September 2011 - 11:24 AM

The XTi limiter wasn't very useful because it didn't offer any better resolution than -3dB (50% power), -6dB (25% power) or -12dB (6% power).

The XTi2 limiter is much better because now you can set it in steps of 0.01dB. You can also set threshold and attack.

Since the 728s wants 3200W and the XTi6002 supplies 6000W, you could dial in the limiter to give you exactly 3200W (-2.73dBFS).  

The iTHD limiters are much more precise because they are in terms of peak voltage, RMS voltage, and thermal voltage.  In short, this gives you finer control over dynamics.

#3 dakos

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Posted 28 September 2011 - 02:20 AM

QUOTE(Kevin Heber @ Sep 26 2011, 11:24 AM) View Post
The XTi limiter wasn't very useful because it didn't offer any better resolution than -3dB (50% power), -6dB (25% power) or -12dB (6% power).

The XTi2 limiter is much better because now you can set it in steps of 0.01dB. You can also set threshold and attack.

Since the 728s wants 3200W and the XTi6002 supplies 6000W, you could dial in the limiter to give you exactly 3200W (-2.73dBFS).  

The iTHD limiters are much more precise because they are in terms of peak voltage, RMS voltage, and thermal voltage.  In short, this gives you finer control over dynamics.

Dear Kevin,
The XTI 6002 has a maximum output of 6000W at 4 ohm bridged, but it's rated at 1% THD and not at 0.5% THD like the rest of the ratings, would it be correct to calculate as if the real wattage is a little lower, say around 5000W?
Thank you

#4 Kevin Heber

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Posted 28 September 2011 - 01:19 PM

I would say no, you're not going to notice 1%.  When the amp clips, the distortion jumps up to ridiculously high levels, like 20%, and you will hear it plainly.

The half-percent difference is probably due to other factors in the circuitry, but it won't be clipping at 1%.