New Build - T30s and then Otops to follow

[escapemcp]

doesnt matter if its barely at 0 db on your mixer. if its hitting the limiter (almost always), then your input is obviously too hot. the only thing the knobs on the front of an amp do is attenuate the *input* signal btw, so you are achieving the same thing as turning your mixer down.

Yeah, so setting the limiters with the amps fully open and then turning down seems to be the way to go for now - cause I ain't going to get DJ's stick to -10dB!

And being a little pedantic, if you set the limiter to 50V with the volume on half... it wouldn't matter. A 50V limit is a 50V limit whatever the attenuation is set to on the front of the amp... ooh hang on... it is like this when the limiter is BUILT IN to the amp... I can see now that with a separate limiter, you would HAVE to run the amps wide open to set the limiter. <to me

[escapemcp]

You have to set the limiter with the attenuation on the amps fully open, simply because, if you don't and "someone" turns up the attenuators, your drivers are going to get more than your driver protecting voltage.

See above

It's not exactly moot when you may introduce something like a DEQ, as any variable can possibly be changed. Not by you.

Again, the AMPS are limited to 50V, so I can chuck ANY signal into the amp and I will not exceed the 50V. I preferred the security of the limiter in the amp, as no amount of fiddling by people thinking they are helping (such as a major rewire by some bright 'spark') cannot mess up my system! As I said in my last post, I have been doing all my thinking with the amp based limiter, and you guys are doing all of yours with a separate limiter... hence why we are discussing the same point from different angles. I know how set the limit on my system, you know how to set it on yours... and that's all that's important

You have to know your system inside out to protect drivers, and set up up against people who might try to "help".

GODDAM "HELP"ERS!

If some drunken idiot comes up to you and somehow pushes everything to max, that is the point at which you have to know the limiter is set correctly, and none other.
Much more so for your subs than your tops...

Said drunken eedjut could unplug all my kit and use my amp wired up to his kit and he STILL couldn't damage my system...

But I do have to ask you guys are YOU protected in the same circumstance??

Sorry, couldn't resist

[Grant Bunter]

Again, the AMPS are limited to 50V, so I can chuck ANY signal into the amp and I will not exceed the 50V. I preferred the security of the limiter in the amp, as no amount of fiddling by people thinking they are helping (such as a major rewire by some bright 'spark') cannot mess up my system! As I said in my last post, I have been doing all my thinking with the amp based limiter, and you guys are doing all of yours with a separate limiter... hence why we are discussing the same point from different angles. I know how set the limit on my system, you know how to set it on yours... and that's all that's important

It doesn't matter if the limiter is in the box, or in another box before the amp, because in either case, the path is the same: Signal/limiter/amplifier.
The only difference, again, is that the limiter is one module in your box, and the amp another module. The limiter in your amp isn't an integral part of the amplifier module itself.

I get the feeling you think your amp is only capable of 50V of output (you said a little way back you had the limiter set to 0, ie the limiter IS NOT ENGAGED, so you haven't actually limited to 50V).
This doesn't account for momentary transients, which, as per the plans, may be in the order of 10 times the 50V output. It's the transients that have to be stopped by the limiter in order to fully protect your drivers.
Set the limiter with a single -0.5dB increment. You should be able to report back after doing this that, regardless of what you do to the signal chain, your measured output with a DMM is somewhere in the high 40's volts...

[sine143]

or you could just go out and buy yourself a cheap yammie mixer (http://www.musiciansfriend.com/pro-audi ... ompression) to put in between you and the DJs. I tried the whole Dj Mixer straight to the amp thing for a whole year, and let me tell you, either get a stiff yard stick to start smacking hands when they reach for the master, or forget about SQ, cause the first time you walk to the bar for a drink, or take a piss, your limiter is going to be full on active, and the limiters on the crowns sound like poo, I cant IMAGINE what the limiter on the Inuke must sound like....

[escapemcp]

I get the feeling you think your amp is only capable of 50V of output (you said a little way back you had the limiter set to 0, ie the limiter IS NOT ENGAGED, so you haven't actually limited to 50V).
This doesn't account for momentary transients, which, as per the plans, may be in the order of 10 times the 50V output. It's the transients that have to be stopped by the limiter in order to fully protect your drivers.
Set the limiter with a single -0.5dB increment. You should be able to report back after doing this that, regardless of what you do to the signal chain, your measured output with a DMM is somewhere in the high 40's volts...

Ok.. was thinking along those lines and did indeed run it at -0.5dBFS the other night. I was thinking along the lines of whether the limiter is permanently engaged - even at 0dB - as the limit light on the amp was coming on at pretty well much the same point whether at 0.5 or 0dB... i know that in a 'normal' amp A or AB you can easy get peaks but do these class D amps have to have some form of limiting on them to protect them?... anyway it is more out of theory as i just like to know how this stuff works -0.5 dB will do for me... i think you can only hear >1dB change anyway! Suppose it all comes down to supply rails... the amp cannot put out more than that
BTW my last post was written by my british humour with a smile on my face... hopefully to bring a smile to yours. i was in no way disrespecting your kit.. in fact i envy it! . Just thought i'd make that clear
Oh... am using an old analogue voltmeter.. this is bad, right? I knew that i purchased the amp as it put out just over 50V, but having just re-read the review on behringers website, http://www.behringer.com/EN/Products/NU3000DSP.aspx under reviews - looks like it can do up to 61V into 8 ohms and 59 into 4 - ideal for bfm subs, BUT i think i'd better check that limiter again with a proper digi voltmeter! 60V is the best part of 50% more power than the 50 i should be feeding them and 0.5dB isn't going to knock it down by 10V. :/ That review is great reading for anyone thinking about getting an inuke3000 btw

[Grant Bunter]

No worries with the humour, it's all good

Most class D amps have switch mode power supplies, which, in essence, will keep maximum power to the supply rails at all times.
Doesn't matter which amp type it is, all amps can produce transients well above expected output.

I'm not sure about the inukes in particular but plenty of amps nowdays will engage some form of protection circuitry, usually activated by heavy clipping. The protection circuitry decreases output power so that the show goes on because the amp doesn't shut down.
As to if this is evidenced by a limiter light on the inukes, once again, I don't know, but it's likely that is the case.
(edit: just read the review and indeed it's there in black and white on page 5, the reviewer called it power limiting, "under heavy load the power limiter activated after 3 seconds at 4 ohms". This power limiting should not be confused with setting the limiter to get the voltage you want, hope that makes sense.)

Nothing wrong with analogue meters, people got by with them for decades. They are however harder to read when trying to do what we want them to do in this situation. At a glance it's more difficult to tell if you have 50V, or in fact 49V or 51V, if you get what I mean. A digital readout is simpler in that regard, it gives you a figure.

If the inuke is capable of 61V, according to some, then you have to set your gains and while reading the meter, (with the attenuators fully on) keep reducing the limiter until you get your 50V. Then you can say you're limited to 50V

My (sub) amp does 450W/4ohms (roughly 42V). I had to limit around 6dB to get my output limit set to 35V (for my BP102's), so yeah, -0.5dB sounds a bit light on...

[escapemcp]

or you could just go out and buy yourself a cheap yammie mixer (http://www.musiciansfriend.com/pro-audi ... ompression) to put in between you and the DJs. I tried the whole Dj Mixer straight to the amp thing for a whole year, and let me tell you, either get a stiff yard stick to start smacking hands when they reach for the master, or forget about SQ, cause the first time you walk to the bar for a drink, or take a piss, your limiter is going to be full on active, and the limiters on the crowns sound like poo, I cant IMAGINE what the limiter on the Inuke must sound like....

Yeah.. that was my problem the other night. I just turned down the amp to ensure the limiter was rarely engaging. BTW Are you dissing my amp (well, limiter)? .. it didn't sound bad when i was hitting it.... maybe because the signal is in the digital domain already when it runs through the dsp, it may not suffer as much as on your crowns (dunno if they have dsp on them), or it may be that my ears are iron and not golden!
I was thinking of using a mini mixer, but luckily i will control the gain on the tops through the deq and the subs will be done via gain on the sub out of the mixer. That way i can have the mixer just touching the red (well orange as it is behringer!! ) and be just under the limiter of the amp.

[escapemcp]

No worries with the humour, it's all good

Good... I suppose with your cricket team you have to have a decent sense of humour

Most class D amps have switch mode power supplies, which, in essence, will keep maximum power to the supply rails at all times.
Doesn't matter which amp type it is, all amps can produce transients well above expected output.

I'm not sure about the inukes in particular but plenty of amps nowdays will engage some form of protection circuitry, usually activated by heavy clipping. The protection circuitry decreases output power so that the show goes on because the amp doesn't shut down.
As to if this is evidenced by a limiter light on the inukes, once again, I don't know, but it's likely that is the case.
(edit: just read the review and indeed it's there in black and white on page 5, the reviewer called it power limiting, "under heavy load the power limiter activated after 3 seconds at 4 ohms". This power limiting should not be confused with setting the limiter to get the voltage you want, hope that makes sense.)

Perfect sense <insert joke about the criminality of ancestors here>

Nothing wrong with analogue meters, people got by with them for decades. They are however harder to read when trying to do what we want them to do in this situation. At a glance it's more difficult to tell if you have 50V, or in fact 49V or 51V, if you get what I mean. A digital readout is simpler in that regard, it gives you a figure.

If the inuke is capable of 61V, according to some, then you have to set your gains and while reading the meter, (with the attenuators fully on) keep reducing the limiter until you get your 50V. Then you can say you're limited to 50V

My (sub) amp does 450W/4ohms (roughly 42V). I had to limit around 6dB to get my output limit set to 35V (for my BP102's), so yeah, -0.5dB sounds a bit light on...

Yeah... seeing that 61V figure has me a little worried. With -0.5dB the needle is at about 47V. If i change the limit value to 0dB, i have to change range to 250V and it could be 50V or it could be 61!! If i leave it on 50V range it hits full scale, but not with much force and imho not enough to suggest that the needle would be jumping up to 61V - not the ideal basis for measuring my amp... thank god i only have to get to 50V and not 60 with this meter. I think a DMM should be top of my list (after a deq.. oh and a few powercons... and the 2nd amp rack of course.... &...)... but first it's time for a nice cup of tea and some scones to help me repress my public school memories

[88h88]

For the record I have that little Yamaha mixer that was linked above. Great little thing and perfect for DJ setups.

[byacey]

Judging by the ranges on your meter, it's a cheap hobbyist type meter with questionable accuracy; even if you could read the scale within a 1 volt resolution. Better get a digital.

I've posted previously what probably is classified as a rant. Amplifiers don't just produce unpredictable transient spikes. The highest peak voltage you can possibly get is within about 1 volt of whatever the amp power supply rails are running at in a class AB2 output topology. This means if the amp output is capable of 60V RMS absolutely flat out, the highest peak you can ever realize is 1.414 times this value, and in this example, it happens to be 84.84V peak. That's it, the absolute ceiling. If you can realize a transient signal of 10 X 50V, your amp would have to have a power supply rail of at least 500 volts.

Now if you set your limiter, which usually is designed to detect peak voltage, to the RMS value of the signal, to 50V, your speaker will see peaks of 70.7V, and this is normal unless you are trying to reproduce square waves.

Many limiters have what is termed "overshoot" which means the limiter can't react fast enough to clamp the signal fully, so initially a slightly higher level may sneak through for the first half millisecond or so until the limiter can react. Even so-called brick wall limiters have a little bit of overshoot, but not enough to do any damage.

Really fast transients could possibly get past the limiter, but in the case of subs, two things are working in your favor: A) the driver cannot react fast enough to produce these transients due to the inertia of the cone, B) If your crossover is doing it's job, fast transient spikes which are essentially high frequencies, get filtered out before the amp.

Regarding class A amps, I don't know of anyone using them in pro audio applications, or even why the would do so, unless they were trying to heat the building too. They are very inefficient.

Class D amps, or any other class used for audio, will try and faithfully reproduce whatever line level signal you send, transients, spikes, mush, whatever. If it didn't, this would be considered distortion.

[escapemcp]

Judging by the ranges on your meter, it's a cheap hobbyist type meter with questionable accuracy; even if you could read the scale within a 1 volt resolution. Better get a digital.

Yes, I'd better!!

Now if you set your limiter, which usually is designed to detect peak voltage, to the RMS value of the signal, to 50V, your speaker will see peaks of 70.7V, and this is normal unless you are trying to reproduce square waves.

So when the voltmeter is measuring 50V RMS and you will get transients of up to 70V hitting the speaker?? Is this correct (the facts, not the setup)? So I am effectively setting the peak limiter to 70V? This would explain why in the iNuke remote control program on the PC, the voltage values were nothing like what I was expecting when I adjusted the dBs (if you enter the impedance you can see the voltage as you adjust, or even set the limiter based on voltage )

Regarding class A amps, I don't know of anyone using them in pro audio applications, or even why the would do so, unless they were trying to heat the building too. They are very inefficient.

I just meant 'heavy iron' ones.. I thought they were A and AB, but maybe it's just AB (and a 'little' H to boot )

[byacey]

So when the voltmeter is measuring 50V RMS and you will get transients of up to 70V hitting the speaker?? Is this correct (the facts, not the setup)? So I am effectively setting the peak limiter to 70V? This would explain why in the iNuke remote control program on the PC, the voltage values were nothing like what I was expecting when I adjusted the dBs (if you enter the impedance you can see the voltage as you adjust, or even set the limiter based on voltage )

I just meant 'heavy iron' ones.. I thought they were A and AB, but maybe it's just AB (and a 'little' H to boot )

Correct, except they aren't considered transients. Transients are typically a non-periodic, random waveform, usually considered a spike with a fast rise and fall time. Perhaps this may clear things up:
http://www.ee.unb.ca/tervo/ee2791/vrms.htm

A reasonable quality digital meter reads RMS on AC voltage, whereas an analog meter provides an average reading minus any inaccuracies inherent in the meter. Best you can hope for is a ballpark reading unless it's a service bench quality analog meter with higher resolution scales. When testing with a sine wave, the peak voltage is always 1.414 times the RMS voltage. I imagine the control software you are using displays the RMS voltage as well, unless it indicates otherwise. If it displays peak voltage, multiply that value by .707 to calculate the RMS voltage.

Best is to get a true RMS digital meter and base you settings on that meter; then you're not guessing or making assumptions about anything.

Class H amps are essentially class AB2, except they switch the rail voltages higher according to the demands of the signal. This makes the amp more efficient at lower levels as less heat is developed by the output transistors.

[escapemcp]

A reasonable quality digital meter reads RMS on AC voltage, whereas an analog meter provides an average reading minus any inaccuracies inherent in the meter. Best you can hope for is a ballpark reading unless it's a service bench quality analog meter with higher resolution scales. When testing with a sine wave, the peak voltage is always 1.414 times the RMS voltage. I imagine the control software you are using displays the RMS voltage as well, unless it indicates otherwise. If it displays peak voltage, multiply that value by .707 to calculate the RMS voltage.

Best is to get a true RMS digital meter and base you settings on that meter; then your not guessing or making assumptions about anything.

Yeah.. it is marked Vpeak on the inuke rc app. The realization of this earlier was another one of my 'eh?' questions answered And YES.. i get it.. digi multimeter on order It will be interesting to compare the voltmeter readings with what the amp thinks it should be putting out (allowing for the 1.141 multiplier - from the 3dB crest factor right? )

Class H amps are essentially class AB2, except they switch the rail voltages higher according to the demands of the signal. This makes the amp more efficient at lower levels as less heat is developed by the output transistors.

Yeah... hence the 'little' comment

I reckon i have about 90% of the theory stuff on here sussed... even if i do sometimes use the wrong terminology!!... of course the more you know, the more you realize you don't know, so that figure can only go down!!!

[Grant Bunter]

Good... I suppose with your cricket team you have to have a decent sense of humour

We were No 1 in World cricket for a long time, and will be there again.
Enjoy it while you can. One day you too will bemoan the almost constant defeat of your team.

<insert joke about the criminality of ancestors here>

Are you absolutely positive none of your ancestors came here for stealing a loaf of bread?
We might be related bwahahahahaha

but first it's time for a nice cup of tea and some scones to help me repress my public school memories

There there young chap, the cup of tea and scones may be lovely, but nothing will help you repress those memories

[byacey]

It will be interesting to compare the voltmeter readings with what the amp thinks it should be putting out (allowing for the 1.141 multiplier - from the 3dB crest factor right? )


I reckon i have about 90% of the theory stuff on here sussed... even if i do sometimes use the wrong terminology!!... of course the more you know, the more you realize you don't know, so that figure can only go down!!!

I'm not sure what sussed means, but you're off to a bad start if you use 1.141 instead of 1.414.