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Letting amps clip or running a limiter?
Letting amps clip or running a limiter?
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Old 19th February 2020, 02:51 PM   #1
kipman725 is offline kipman725  United Kingdom
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Default Letting amps clip or running a limiter?

In a situation where your speakers would have a peak limiter set higher than the maximum peak output voltage of their connected amplifier would it be better to set a zero attack limiter with a short release time (4mS) just below the clip limit of the amplifier or to let the amplifier clip? if so how far below the maximum output voltage of the amplifier would you set the limiter?
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Old 19th February 2020, 03:57 PM   #2
conanski is offline conanski  Canada
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There is no point setting a limiter above the voltage output of the connected amplifier.. why would you do that? Clipping amplifiers sound bad and if there are high frequency drivers attached they can be overpowered with this clipped/compressed output, so I always set limiters just below amp clipping when that is what you have to work with.
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Old 19th February 2020, 05:44 PM   #3
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
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Why not to use a limiter previous to the amp? Clipping the amp will not cause problems to the amp itself, but may overheat the voice coil and harm the neighbors.
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Old 19th February 2020, 07:27 PM   #4
kipman725 is offline kipman725  United Kingdom
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Perhaps I was unclear. What I'm proposing is setting the limiter just below the amplifiers clipping point. This will have the effect of slightly reducing the maximum output power but more predictable behaviour. Also the limiter I have available has zero attack but a minimum release time of 4mS, or it can have longer release. The particular design of my speakers is such that there is no danger of overheating the voice coils using this amplifier, its not required for protection.
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Old 19th February 2020, 08:44 PM   #5
conanski is offline conanski  Canada
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You correct.. I misunderstood your first post. In that case then yes do as you describe and set the limiter release time based on the frequency range it is covering, longer for low frequencies and shorter for highs and strive for a balance between producing audible pumping and totally crushing the dynamics.
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Old 19th February 2020, 09:17 PM   #6
conanski is offline conanski  Canada
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Here are the recommendations from Powersoft for K series amps, other processors will behave differently so the numbers can and should be altered to taste.

[IMG]49558817552_fd65bda93b_o (2).png[/IMG]

Last edited by conanski; 19th February 2020 at 09:24 PM.
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Old 19th February 2020, 11:39 PM   #7
conanski is offline conanski  Canada
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Here is the data I was referring to..
[IMG]Click the image to open in full size.Powersoft limiting by paul, on Flickr[/IMG]
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Old 20th February 2020, 09:30 AM   #8
kipman725 is offline kipman725  United Kingdom
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would it be better to choose a zero attack time over the recommended attack release ratio?
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Old 20th February 2020, 09:32 AM   #9
TNT is offline TNT  Sweden
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Avoid clipping. Period.

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Old 20th February 2020, 10:19 AM   #10
JMFahey is offline JMFahey  Argentina
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Quote:
Originally Posted by kipman725 View Post
would it be better to choose a zero attack time over the recommended attack release ratio?
Many fear "losing power", worry about "the numbers", and so both set threshold at 99.99% of output power and attack time to ZERO.

Nice on a sheet of paper, a mess in the real world, in exchange of nothing.

1) PA amps are not driven by sinewaves but by Music Program, which has at least some dynamic range.
Which means short time peaks will trigger limiter, and average output will be significantly below that, by definition.
Worrying about how close narrow peaks get to rails is then not too significant, and itīs fine, we are amplifying Music here.

2) ZERO attack time means that waveform tops will be attenuated so flattened as soon as signal reaches threshold voltage, very similar to what plain clipping does, so whatīs the point?

3) ultra short release time combined with (2) means lower frequencies (within that band) will heavily modulate higher ones.
Maybe you are (sometimes) avoiding flatb tops, but definitely creating tons of intermodulation, the second distortion mchanism.

In a nutshell, use limiters in the tried and true way arrived at by years of experience, tying to squeeze down to the last Watt may be a self defeating goal.
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