Limiters - Finally understood

[yigba]

So after a few years of messsing around with setting the limiters I think I finally understand how to use them and better yet "read" them. This thread is more for noobs than anyone else.

So you set the limiter to reach the max voltage of the amp WITH GAINS WIDE OPEN that your speakers can handle. Easy, right? What I didn't fully comprehend is that the limiter kicks in based on the voltage from the board - it actually has nothing to do with the amps themselves. D'oh!!

What I had been doing during an actual gig was turning the amp knobs down a bit. So, in my ignorance, to get more volume at gigs I had been trying to turn up the mixer which would invariably hit the limiter. It was making me nuts that I kept glancing at my BSS-336 and would see the limiter being hit continuously. And I couldn't understand why because we weren't that loud. Instead I should have simply turned the knobs on the amps up and kept the mixer level the same. I found with my amps the voltage doesn't really develop significantly until the knobs are almost wide open. (Crowns XLS1500 AND XS1200) Stupid, stupid me.

How do I operate them now? Simple. Sub amp (XS1200) wide open, XLS1500 around 3 o'clock to balance out the sound, done. Pair of OTop12's and T39's (usually one T39 at smaller places). I know that there may be a bit more noise if I operate this way but if it's unbearable I simply turn the mixer up and the amp knobs down a bit more. But most of the time - if not always - the noise level in the bar is way higher than the system.

[doncolga]

This was a big thing for me to get when I started here as well. Accidentally hit my limiter at a recent gig as my amps were inadvertently way too low. Turned them up and the mixer down a bit and was where I needed to be.

[Charles Jenkinson]

New area for me too. I figure the output LED's on the mixer light up at the same voltages, whatever is coming into the mixer, so when theyre maxing, they max the same every time. I don't like large variances in input signal from different equipment, when i only have a cheap/small mixer, without channel gain knobs, but I guess that's the art of balancing everything to get good boom de de boom at the drivers. Note: the above is my assumption about how it works - do say if I'm off piste.

[BrentEvans]

Rather than adjust the gains on your amps to balance the sound, do it in the DSP. That way, you just turn the amps up to max, and enjoy the full capability thereof.

[yigba]

Only reason I like the amp knobs to balance is that they are easily adjustable. Just turn the knobs. On the DSP you have to go into the program, which is a PITA if you need to do it quickly.

And I also can't imagine hitting a limiter (with my setup at least) with these speakers in regular bars. That would be insanely loud. I figure it would feedback before it reached its output capability.

[Bill Fitzmaurice]

Only reason I like the amp knobs to balance is that they are easily adjustable. Just turn the knobs.

That's OK so long as the limiter was set with the gains wide open. If you set the limiter with the gains at -6dB, for instance, then if you do open the gains wide you've doubled the amps voltage swing capacity, and that's a recipe for magic smoke.

[yigba]

That's OK so long as the limiter was set with the gains wide open.

That's exactly what I do.

[byacey]

I remember years ago some speaker manufacturers had line level processors that had sense leads connected to the amplifier speaker outputs. Upon examination of the circuit, the sense leads were simply to activate the limiters. Not a bad idea, as the limiters would always clamp at the same output threshold, irrelevant of where the amp input gains were set. However, if someone left the sense lines disconnected, or removed them for whatever reason, there was no protection.

[escapemcp]

I remember years ago some speaker manufacturers had line level processors that had sense leads connected to the amplifier speaker outputs. Upon examination of the circuit, the sense leads were simply to activate the limiters. Not a bad idea, as the limiters would always clamp at the same output threshold, irrelevant of where the amp input gains were set. However, if someone left the sense lines disconnected, or removed them for whatever reason, there was no protection.

That's why I like onboard DSP on my amps - all the benefits of those 'sense leads' without the leads (or any danger of not connecting them). The onboard DSP (limiting) makes it even harder to blow stuff through incorrect wiring - the only danger being if I attach my tops to my sub amp (and that's pretty obvious anyway and you'll notice things aren't right before you start giving it the full beans). This way I am free to use volume controls and still be able to run things right up to my 50V limit even if my volumes are only at 3/4.

[Bruce Weldy]

That's why I like onboard DSP on my amps - all the benefits of those 'sense leads' without the leads (or any danger of not connecting them).

uhhhh.....what the heck is a sense lead?

The onboard DSP (limiting) makes it even harder to blow stuff through incorrect wiring - the only danger being if I attach my tops to my sub amp (and that's pretty obvious anyway and you'll notice things aren't right before you start giving it the full beans).

You are making a huge assumption that one would turn everything up to war volume then hit play...only to find out they hooked it up wrong and blew up a speaker. Any sane person brings up volume slowly when wiring up the system the first time. And once it's wired, it shouldn't be messed with again. I just don't see there being any advantage.

This way I am free to use volume controls and still be able to run things right up to my 50V limit even if my volumes are only at 3/4.

Are you really sure that this is how the limiters work on the amp? If the dsp does the limiting, I'm sure that it falls exactly in the same place in line that an outboard dsp would - before the amp. That would mean that the dsp engages the limiter before the amp sees the signal and your amp at 3/4 volume would not see the full 50 volts.


If you like your dsp in the amp - that's great. But I really don't think any of the reasons you listed for doing so are valid. Someone correct me?

[escapemcp]

That's why I like onboard DSP on my amps - all the benefits of those 'sense leads' without the leads (or any danger of not connecting them).

uhhhh.....what the heck is a sense lead?

I'm just going by what byacey said!

The onboard DSP (limiting) makes it even harder to blow stuff through incorrect wiring - the only danger being if I attach my tops to my sub amp (and that's pretty obvious anyway and you'll notice things aren't right before you start giving it the full beans).

You are making a huge assumption that one would turn everything up to war volume then hit play...only to find out they hooked it up wrong and blew up a speaker. Any sane person brings up volume slowly when wiring up the system the first time. And once it's wired, it shouldn't be messed with again. I just don't see there being any advantage.

No, I mentioned that I WOULDN'T give it the "full beans" right from the off... I ALWAYS start with the volumes down low (i.e. -∞dB) and then slowly increase volume from there. I can wire my rack as perfectly as I want, but each and every time I setup requires plugging in speakers into the correct amps, and this is why I will start with the volume down low EVERY time.

This way I am free to use volume controls and still be able to run things right up to my 50V limit even if my volumes are only at 3/4.

Are you really sure that this is how the limiters work on the amp?

No

If the dsp does the limiting, I'm sure that it falls exactly in the same place in line that an outboard dsp would - before the amp. That would mean that the dsp engages the limiter before the amp sees the signal and your amp at 3/4 volume would not see the full 50 volts.

I'll test this weekend. IIRC the limiter on the iNuke is the LAST 'device' before the signal hits the actual power amp section of the amp. The 'volume' controls on amps are usually input attenuators, which puts them firmly BEFORE the limiters. I think I'm right, but I will test this to be sure and report back.

If you like your dsp in the amp - that's great. But I really don't think any of the reasons you listed for doing so are valid. Someone correct me?

Yeah, I LOVE my onboard DSP Maybe you will someday too

[byacey]

A sense lead is what I described above, a pair of wires providing feedback from the speaker terminals back to the line level limiter / processor. This essentially measures the speaker level voltage against a comparator so the limiter knows when to start clamping the line level signal.

Not mentioning Behringer, but a designer would have to be a moron to put onboard DSP limiting before the input attenuators unless it was sensing the output signal from the speaker terminals; by sensing the speaker output terminals limit threshold is not affected by where the level controls are set.

This is the only drawback to a line level limiter like the Driveracks and other similar products; they rely on the amp level controls being locked or wide open to maintain protection. Not a big deal, but one that needs proper attention from the person setting it up.

[Bruce Weldy]

Yeah, I LOVE my onboard DSP Maybe you will someday too

If I had a small system .... maybe. Or, even a huge system... probably.

But in my sized rig, I like being able to make quick changes to the whole system from the driverack without having to touch each amp....and since my amps are on the bottom of the rack - I don't like standing on my head to do it.

And I like cheaper amps that I can keep adding to my system without having to buy redundant dsp each time.

It's a choice everyone makes and I think there are some advantages each way - it's just important that everyone understand the differences and not think it's doing one thing when it's doing something else.

Knowledge makes us all better at what we do.

[Grant Bunter]

but a designer would have to be a moron to put onboard DSP limiting before the input attenuators unless it was sensing the output signal from the speaker terminals; by sensing the speaker output terminals limit threshold is not affected by where the level controls are set.

byacey,
would you explain this a bit more please (i'm not sure if I'm understanding).

After all if you use a non DSP amp with an outboard limiter, then the limiter is most certainly before the amp attenuator.

So why would it not make sense to build a DSP amp the same way?

[escapemcp]

After all if you use a non DSP amp with an outboard limiter, then the limiter is most certainly before the amp attenuator.

This would be due to the 2 box design... the signal can't go from the input attenuators on the amp, back into the DCX/Driverack (to limit) and then back out into the amp.

So why would it not make sense to build a DSP amp the same way?

No because the DSP amp can be designed with a more sensible signal flow. With a DSP amp you can ensure that the input attenuators are exactly that. These therefore come waaay before the limiter. The onboard limiter is the very last bit of signal processing performed before the signal hits the power amp section of the DSP amp. This is why I am saying that I like the all in one (DSP) amps - the signal flow is more logical (in my eyes).

As with a lot of things on here though, it comes down to personal preference/system configuration and setup. There is no right or wrong way to do it... both are valid ways to limit. Each method has it's positives and negatives. I was just trying to point out the positives of the 1-box (DSP amp) solution.