Subwoofers, MiniDSP and compressor settings

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I'm playing around with the compressor in MiniDSP Flex to avoid my subwoofer power amps clipping and/or go into voltage- and current-protection. They do clip very hard, and when a protection event occur they tend to produce a very loud "click" sound from the speakers. The MiniDSP also clips quite hard.

My power amps clip at 3.46V input, while the max output of the MiniDSP is 4V, a relative difference of 1,26 dB

The subwoofers are crossed over at 80 Hz.

My current compressor setting is like this:

1691398487948.png


Any thoughts/suggestions.... ? Do the attack and release times make any sense?
 
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The question is whether my compression attack and release settings makes sense for subwoofer use in the frequency range below 80 Hz.

My subwoofers don't need voltage limiting, as I'm not overloading them. What needs to be done is to avoid protection and hard clipping in the ICEpower amp and MiniDSP output, as I also said in my original post.

The woofers driven by the ICEpower 2000AS2 are six SEAS L26ROY in 35 liter closed boxes, connected in two series of three.

The resulting impedance is 12 ohms nominal per channel. Since I use both channels of the 2000AS2, the module can deliver around 2x700W in short bursts (150 ms). That, divided over six woofers, is no more than a little over 200W per woofer.

The problem I want to solve comes when there are peaks exceeding 2x700W, where the amp goes into protection with very audible results. There is no soft-clip or limiter in the amp module itself.
 
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Hi,
20ms is a bit long for the attack setting imho.
Something in the 10/ 13ms range is usually ok with bass ( my starting point, at 80hz a sinus cycle is circa 12ms).
For the release try 100ms.

Do you know at which value of dbfs the dsp start to clip? If so then use this as a basis for your threshold. From there lower it until the amp never goes into protection. You might need to use a steeper ratio, 20 or more to really have a limiter, 10/1 is at the border between compressing and limiting.
 
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These are my current settings, adjusted by ear. It's like you say half-way between compression and limiting. I found it better to lower the threshold a little than using a greater ratio.

1692704437887.png


I will try to visualize the levels where the MiniDSP and amp starts to clip and protect.
 
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Yes limiting can be audible ( greater ratio). Lowering treshold will have sort of same effect anyway, all in all what matter is the outcome and if you find a more gradual effect is more pleasing: so be it.

The issue i see is you have 2 clipping points ( dsp and amp). You'll have to identify the lowest one and focus on it.

Do you enter the dsp analog or digital?

About release time: it'll depend of how often you expect clipping to occur. For limiters usually i look for fast attacks and release as the purpose is to 'grab' peaks if/when they happen. That said it can sound a bit oppressing if you need it to work often ( you are a bit too loud in rms).

Anyway you'll hear if it need to be faster.
 
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The points are, related to 0 dBFS (4V RMS) on the output of the DSP :

DSP output clipping : 0 dB (of course)
ICEpower 2000AS2 clipping : -1,25 dB (max output voltage ~105V)
ICEpower 2000AS2 protection : -4,06 dB (2x700W @ 6 ohms)

I set my threshold at -6 dB, which is 2 dB below the protection point of the amp. I cant really hear the compression, other than that the amp no longer is complaining. When it enters protection, a very loud "click" is heard.


Input signal of the DSP is analog. I have made sure that the input is not clipped at any time, as I gain up the signal in the DSP, so the outputs are always some dB higher than the input.
 
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Perfect! 👍

One thing though: don't rely blindlessly on 0dbfs being ceiling for dsp out, it can happen some tenth of db below the theorical value. Usually it is dac related but it can happen in digital domain too ( it depend of the gain structure of the device and treatments used).
When/if you have choice of a 'ceiling ' digital value for ouput choose something like -0.1 or -0.2 dbfs it usually protect from dac nastys.

If issue still arise then check if there is no 'over' into the processor ( digital gain structure: usually seen as squared peaks on outputs) and if so lower the first digital gain stage (or dsp input) until it disappear.
 
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I never encountered clipping playing music. With movies however, where the LFE channel is 10 dB louder than the other channels, it did occasionally happen, maybe once or twice during a movie. I don’t want to roll off the low end either, as movies loose impact. With my current compressor/limiter setting I avoid the clipping with no audible side effects.
 
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I used to have ICEpower 1000ASP amps powering my subwoofers. This amp has soft clipping, and it can output its max power of 1000W for at least half a minute before it goes into protection. Perfect for subwoofers. The ICEpower 2000AS2 can’t… and I am a little disappointed with it, although it sounds better than the 1000ASP. It’s supposed to be 2x2000W, but in reality it’s more like 2x300W with continuous output.
 
I never encountered clipping playing music. With movies however, where the LFE channel is 10 dB louder than the other channels, it did occasionally happen, maybe once or twice during a movie. I don’t want to roll off the low end either, as movies loose impact. With my current compressor/limiter setting I avoid the clipping with no audible side effects.
Maybe you could try EQ for the lowest bass and see if there's a perceptible difference. The power needed for very low notes (or sounds... like the audiophile railroad recording of yesteryear) rises dramatically for small gains in loudness.