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hpf + limiter for tham 12 12lx60v2 + t-racks DSP

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Category: Plans
Forum Name: New Projects Forum
Forum Description: Forum for new speakerplans projects, in memory of Tony Wilkes, 1953 - 2014
Printed Date: 28 September 2020 at 8:14pm
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Topic: hpf + limiter for tham 12 12lx60v2 + t-racks DSP
Posted By: Angelow
Subject: hpf + limiter for tham 12 12lx60v2 + t-racks DSP
Date Posted: 07 November 2019 at 7:11am
Hi everyone, I'm having trouble setting up the processor for my tham 12 with beyma 12lx60v2.

I use it on a channel of the m50d old version-no-dsp (750w) amplifier, and I can't limit so that the red LED doesn't light up!

I use a t-racks DSP 4x4 Mini , and I set a 40hz high pass, and a limiter mode compressor:
4ms connection
reposition 128ms.
but any value I put in db, even -10db, (amp gain 32db) raising the master the final goes to red anyway! something that does not happen with installations that I use in the premises (normally they use xta) where even saturating the mixer (a practice that is not correct but I want to be sure of not doing damage if I get distracted when I play) the ending never goes red even if the limiter is red steady !!!

regards :)

Posted By: fatfreddiescat
Date Posted: 07 November 2019 at 8:17am
Limiter set to -10dBfs or -10dBu? The Behringer  dcx2496 limiters for example refer to dBfs which is +22dBu, there is no one standard as to what 0dBfs is referenced to, so you would need to check user manual or measure the output
+22dBu is approx 10 Volts
The output at 0dBfs is whatever the manufacturer decides on.

Posted By: Angelow
Date Posted: 07 November 2019 at 9:39am
The dsp interface indicates only "dB"

Posted By: fatfreddiescat
Date Posted: 07 November 2019 at 11:22am
Try starting with:

Threshold -90dB
Attack 1ms
Ratio 'Limit'
Release 3000ms
Knee 0dB

If that doesn't do it then something is very wrong.

Posted By: fatfreddiescat
Date Posted: 07 November 2019 at 11:29am
Just looked at the manual, input impedance of 500K to 1MegShocked
Not going to affect the limiter settings though.

Posted By: Angelow
Date Posted: 07 November 2019 at 11:54am
-90dB !!!!!

Posted By: fatfreddiescat
Date Posted: 07 November 2019 at 12:50pm
Should stop the red light! Basically work your way up from there, be careful not to cook your drivers as you experiment.

Posted By: fatfreddiescat
Date Posted: 07 November 2019 at 12:58pm
Just to add that the XTA has 'look ahead' limiters, the signal on the outputs is delayed a little so that the limiter senses the overload and reacts ahead of the main signal path, the way you are setting the t-racks it is 4ms behind the signal so there is 4ms before the limiter will react.

Posted By: Angelow
Date Posted: 08 November 2019 at 11:37am
I set: release at 240 ms, attack 1ms, threshold 8.5db.
the amp does not go red now!

looking at the xta menu I noticed an auto function that limits based on the input by varying the times, a function that does not have the t.racks :)

now I was wondering, since the woofer supports 700w rms and 1400 of the program, if I should put the two channels in bridge (1500w), and set the limiter to 10 / 11db (1200 / 1400w)
I should have more current but less square wave, what do you think?

Posted By: toastyghost
Date Posted: 08 November 2019 at 4:37pm
Just be aware that a 1ms attack for a subwoofer doesn’t let a full cycle complete before clamping down.

This may help protect stuff, but very much at the expense of the overall sound.

I don’t know if the T Racks use a Peak RMS limiter, or something else, but it is worth investigating this, as sitting in limiters all night increases long term average power trying to get the output from the system, which is a recipe for cooked coils.

The XTA auto function is based off your chosen crossover filters, not the actual content being analysed.

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Posted By: Angelow
Date Posted: 09 November 2019 at 8:54am

so better to put a more powerful amplifier?

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