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[Wayne Smith2]

This would be a first time out with the Mini running on this Crown - or bridging this amp. Looks straight forward enough, I just wanted to get a cross check here.
High and Low pass filtering will happen upstream rather than the amp's filters.
Thanks

[Frank Koenig]

This would be a first time out with the Mini running on this Crown - or bridging this amp. Looks straight forward enough, I just wanted to get a cross check here.
High and Low pass filtering will happen upstream rather than the amp's filters.
Thanks

I doesn't matter where in the signal path those filters are so long as they are there. I would follow Danley's guidance on the high-pass. That driver is rated at 700 W AES, as I recall, so I wouldn't set your average power limiter any higher than 700/3 or 233 W. When the police show up the second time because of bass complaints -- relent    --Frank

[Neale Watson]

I wouldn't set your average power limiter any higher than 700/3 or 233 W

^^^
this

[Steve Crump]

I wouldn't set your average power limiter any higher than 700/3 or 233 W.

Frank,


I need educating here. Why do you pick 1/3 of the continuous rating for the average power limiter setting? I understand that you are protecting the driver, but couldn't the driver with that rating safely handle a higher average. My main reason for asking is that I am about to pull out some of my gear and make some changes to the amp configuration and I will be setting up limiters during this process and now I am questioning my original setup.


Thanks,

Steve

[Wayne Smith2]

I was going to follow these two guide points from Danley--
'TH Mini - 700 watts continuous 1400 program' (..add, in another part of the spec they use '700 continuous 2800 peak)
and
 "We recommend choosing an amp that is rated no less than continuous and no higher than program. "
The XLS2500 seems to drop right in there at 1500/8ohms bridged.
I won't have a limiter but neither will it be called to go anywhere near max.

[Frank Koenig]

Why do you pick 1/3 of the continuous rating for the average power limiter setting?

Steve,

The AES power /3 guidance comes from Powersoft. I've heard others suggest AES power /2, but why look for trouble? Powersoft also has suggestions for time constants based on type of driver and the size of the voice coil. I'd reproduce it here but don't want to run afoul of fair use. Go to the Powersoft Website and download any of their amplifier user manuals, I think it's in all of them.

Be mindful that there are different kinds of average power limiters. Some measure true power (integrate v*i over time) while others use RMS voltage as a proxy. If each amplifier channel powers only a single driver, the true power limiter is the most accurate. If an amplifier channel powers multiple drivers in parallel, then RMS voltage should be used as otherwise one driver going open-circuit will make more power available to the remaining drivers -- not good. You must take the driver impedance into account when using an RMS voltage limiter. If in doubt, measure with the amplifier open circuited.

Ideally we'd measure the voice coil temperature directly and avoid all this nonsense. I assume some of the better integrated system makers use a more sophisticated predictive thermal model of the driver to do their limiting. I've got some ideas on the subject but I'll put them in a separate post under Audio Measurement and Testing.

--Frank

[Frank Koenig]

I won't have a limiter but neither will it be called to go anywhere near max.

Peak voltage limiters are not for normal operation but to guard against accidents like dropped mics and phantom power pops. They might also serve as a warning that you are on the verge of clipping, which is not normal operation, or shouldn't be anyway. --Frank

[Ivan Beaver]

Steve,

The AES power /3 guidance comes from Powersoft. I've heard others suggest AES power /2, but why look for trouble? Powersoft also has suggestions for time constants based on type of driver and the size of the voice coil. I'd reproduce it here but don't want to run afoul of fair use. Go to the Powersoft Website and download any of their amplifier user manuals, I think it's in all of them.

I used to be in the 1/2 continuous power for a thermal limit.

But after seeing to many drivers burnt with that setting, I now recommend 1/4 continuous power.  Or 6dB down.

I do agree with different attack times for different size voice coils/different power ratings.  What burns coils is energy over time, and larger coils can take more energy than smaller ones.

The power ratings are often misunderstood.  They are NOT continuous, they are for a specific signal for a specific time.  As soon as either changes, the ratings change-higher or lower.

Regarding attack time, it is important to understand how the particular limiters are reacting. 

For thermal protection, the attack time needs to be in seconds, not milliseconds.

But it depends.  In my opinion, a proper limiter should start to engage as soon as the threshold, and the time constant is how long it takes to bring the signal down to the threshod. 

One particular brand of amps have the thermal where it does nothing, until the time constant has been exceeded, and then it starts to bring it down.

I disagree with this, but that is my opinion.  While it can allow more short term peaks, I don't think it offers the protection needed.  So whenever I have to use these limiters, I set them even lower than I normally would.

Limiting is a complicated subject, with a lot of variables, and one answer does not fit all applications. 

I will use different limiter settings if I know specific program materials.  Some to allow more peaks, others for shear "idiot" protection.  Often this depends on the operator.

[Neale Watson]

... I won't have a limiter but neither will it be called to go anywhere near max.

Wayne - I tried this using a Powersoft M30 (similar rating) and surprisingly fried the TH-Mini driver pretty quickly.  I didn't think we were rockin' at the time

[Wayne Smith2]

It came to me a little later, how on earth did I (we?) ever make it through the last 40 years in audio with w/o limiters?
:>)

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