Monitor speaker problems

[RFR]

Do you fuse-protect on the speaker cables...or just watch your volume knob on the amp?

Neither one. Amp is always full bore. I watch my levels on the console. ANY time something is getting plugged in or out, fader is down to zero.

The only time I've ever blown a tweeter is when I was running an underpowered amp.
And that was only once.

Oh, and my NS10's are never used for tracking.
I use my KRKS. Parts are readily available and cheap.

 

[ecc83]

I'm in the camp that says more amp power than speaker rating is good. There are many anecdotes I can relate that support that (e.g. my engineering mate who used to drive a pair of 250 Watt EVs with a 1000watt Aussie Monitor amp).

Yes, that^ is the received wisdom I know and if peeps are actually listening to the speaker/amp combo it is 99% of the time ok (but this thread is about the 1%!).

To me it is the equivalent of running a 300BHP engine into a gearbox and clutch rated at 100BHP. Sure, running to and from Sainsburys day after day, week after week, never a problem. Then someone steals your motor!

It is notable that active monitors do not have amplifiers with 6-9dB of headroom? Of course the very expensive ones have sophisticated protection devices in them but with the budget stuff we rarely read of blown tweeters?

Dave.

 

[ecc83]

I would just like to add a comment in an area that I am very sure of. Guitar amplifiers.

Especially for valved power stages the speaker should be rated at AT LEAST 50% over amp watts and 100% is a better figure*. The guitar amp WILL be driven into distortion and some of the old nominally 100W Marshalls can push 200W when given the beans.

Almost all power amp designs are of course at the mercy of the mains voltage. The published ratings here "should" be for 230V in but most of us get 240V and the "allowed" top end is a valve frying 253 volts!

*This assumes Celestion drivers. Other brands are not as honest or conservative in their ratings and that is a general view throughout the industry.

Dave.

 

[rob aylestone]

My sound op always forgets to power on the graphic on the PA before the amp rack and he always shouts mind your ears before hitting the switch that goes crack. My please to not do this usually get a response of "sorry" but oddly so far nothing has died. This seems a bit odd to be honest, but at some point it will happen.

 

[RFR]

Yes, that^ is the received wisdom I know and if peeps are actually listening to the speaker/amp combo it is 99% of the time ok (but this thread is about the 1%!).

So I gather for monitoring, you're in favor of a power anp rated higher than the speakers?

From what I've gathered over the years from those much, much smarter than I, is that what causes the speakers to blow is distortion. I'm not talking about distortion from a recording of a guitar amp being overdriven, or an amp sim, but the power amp driving the monitors.
The power amp is working overtime and sending a clipped signal to the speakers and they blow. The theory is that with the higher power rated amp is that it's never working hard at all, so it's sending a very clean, free of distortion signal to the speakers.

I first picked up that 'wisdom' right or wrong from the store manager from a high end audio store I worked at for a summer job. (Remember those??? Freaking candy store for me. )

I could never understand why we'd sell 2OO watt amps with 50 watt speakers. And the above was the explanation.

Now with guitar amps, I'd never run a speaker cabinet with a lower rating than the amp!
(Ask me how I know )

 

[ecc83]

"
So I gather for monitoring, you're in favor of a power anp rated higher than the speakers?"

No Rob, or not much. It does not much matter WHAT clips or where, a square wave is effectively the DC rails of the amplifier (although of course it flips polarity twice a cycle) and that is a much higher power level than the "music" power of an amp. The tweeter IS vulnerable because mid band audio will give rise to harmonics at a higher level than it was designed to cope with in "normal" music spectrum. But I say, for high power systems the tweeter should be rated for the amp's power or protected in some way.

Sitting at a desk or listening to hi fi is one thing. You can have 50W speakers and a 100, even 150W amp because even pretty low sensitivity speakers, 85dB/Wmtr say, will chuck out over 100dB SPL for 50W, 'er indoors will shout! Then, since you are LOOKING for problems, even a mild degree of strain or distortion will be evident long before damage occurs. And finally, speakers don't die from a mild overload instantly, only a gross overload will pop things as this thread tells us.

The situation is very different in an auditorium. There the sound engineer might be many mtrs away fro the speakers, might have cans on for T/B or cueing? The sound level can creep up until something melts.

Guitar amps are different. We KNOW they will be driven into distortion and so the amp will deliver up to twice its rated power. For instance I never measured an HT-60 Stage that delivered less than 80W at visible clipping. If you take 10%thd as the standard for grotty gitamps the HT-100 easily qualifies as a 120 watter and goes on to produce even more as you press it. And those figures are tested for a measured 230V mains input! In practice stick another 2dB or so on them.

As I am wont to say quite often here...Shit Happens!

Dave.