Question about the relationship between watts and volume on PA system...

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flobeeblow45

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Probably a very, very stupid question, but I'll ask anyway...
Ok, so let's say I have a PA system (mixer outputting to a pair of speakers), and the maximum output power is 600 watts (300 watts for each speaker). Let's say there are 6 inputs on the mixer, and I connect a microphone to one of the inputs and turn the volume for that input up to 70% of the maximum volume for that input and I start singing through the microphone (while all the other inputs are unused). Would this mean that I'm using 70% of the 600 watts of maximum output power the PA system allows (i.e., .7 x 600 = 420 watts)?? Or am I not understanding things correctly?
 
It's not that simple. Watts makes more sense with a continuous signal, but typical musical signals are variable.
 
bouldersoundguy said:
It's not that simple. Watts makes more sense with a continuous signal, but typical musical signals are variable.
Click to expand...
Thanks. Here's the reason I ask. I've been using a 600 watt PA system for years, and it seems like it might be broken. I only ever use it for singing by myself with a microphone (with nothing else plugged into the other inputs), and I typically turn the input for the microphone up to about 70%. I really don't want to spend $500 on another PA system. But I do have another pair of speakers, and so I was thinking that maybe I could simply buy a new mixer without getting a new full PA system and then just plug the mixer into my other speakers. However for my other speakers the maximum output power of each speaker is 150 watts (so 300 watts in total, which is 300 watts less than the speakers I'd been using). So the question becomes: if I buy a new mixer and plug into my other speakers, would I be able to get the same volume as I did with my old PA system? To simply things, let's say I realized that on my broken PA system it was actually just the speakers that were broken. If I took the mixer from the PA system and plugged it into my other speakers with less maximum output power, could I still get the same volume?
 
Well, it's not that simple. Watts doesn't equal volume from the speaker. Some speakers get louder than others with the same watts. If you're talking about passive speakers with separate amplifiers, you need to look at the sensitivity rating of the speakers to figure out the volume you get from a given input wattage (or more precisely, volts). If you're talking about active speakers, they have input gain on them, so it's more a matter of their maximum continuous SPL rating.
 
bouldersoundguy said:
Well, it's not that simple. Watts doesn't equal volume from the speaker. Some speakers get louder than others with the same watts. If you're talking about passive speakers with separate amplifiers, you need to look at the sensitivity rating of the speakers to figure out the volume you get from a given input wattage (or more precisely, volts). If you're talking about active speakers, they have input gain on them, so it's more a matter of their maximum continuous SPL rating.
Click to expand...
So the PA system that has broken is the Yamaha Stagepas 600i (it's actually 680 watts - 340 for each speaker) (specs below):
usa.yamaha.com

STAGEPAS 400i/ 600i - Specs - Yamaha USA

The new STAGEPAS 400i and 600i are the successors of the renowned STAGEPAS 300 and 500 which earned worldwide acclaim as compact, yet high-powered, portable PA systems with exceptional sound quality.
usa.yamaha.com usa.yamaha.com

And the other speakers I have are ADAM A7X (I have 2 of them; each 150 watts; so 300 watts total):

Can I get the same volume I was getting using the Stagepas speakers if I use the Adam A7X speakers instead?
 
I couldn't find SPL numbers on the Stagepas system, but it probably gets a bit louder. I suspect the Adam speakers will get loud enough (they're rated to get to 114 dB peak), but I'd hate to damage a nice pair of studio monitors using them as stage monitors.

If you were using the same speakers, cutting the watts in half would reduce your volume by a mere 3 dB.
 
bouldersoundguy said:
I couldn't find SPL numbers on the Stagepas system, but it probably gets a bit louder. I suspect the Adam speakers will get loud enough (they're rated to get to 114 dB peak), but I'd hate to damage a nice pair of studio monitors using them as stage monitors.

If you were using the same speakers, cutting the watts in half would reduce your volume by a mere 3 dB.
Click to expand...
Thank you very much for taking the time to look at this. Very helpful.

Yeah, what you say about hating to damage a nice pair of studio monitors is what's keeping me from doing it.
I would get another Stagepas, but somehow the price of that PA system has doubled since I bought mine years ago, and that's just not worth it for me.
Do you know of any good PA systems in the $300-$500 range that can get me the same volume and sound quality as the Stagepas? I really only need a couple of channels and reverb capabilities; I really only ever use it to practice singing.
 
This is very similar to why you don’t buy heating products based on Watts. It has very little to do with how hot your room gets. In your case we are comparing apples with pears. A microphone generates Volts, not Watts. Watts is really about consumption. We can’t even agree about what Watts means in speaker systems. Is it the measurement of the snare in a thump crack four in a bar rhythm or is it your voice singing the word forever that lasts the same time? You could measure both and get different results. The drum could sound louder but measure less or the other way around. The manufacturers of lesser systems might measure the one that makes their product sound better? It would not be incorrect. If your Pa runs out of steam at say 50Hz then there wouldn’t be much point measuring the kick drum, would there? The only measurement as to volume is sound pressure, and nobody really uses that. 1KW at 1m at 1KHz = so many Pascals? This would let you compare. 1KW into a big but inefficient driver might be quiet, but 1KW into a really sensitive speaker might be earth shattering. With your system, the limit is often feedback. At some point, you push the fader and it feeds back. That might be 3 on one system or 5 on another. It’s only a problem when you reach 10 and it’s not loud enough
 
In the good old days, amps were rated at Watts RMS.
Today they are rated at Peak Momentary Power, giving ratings of many hundreds of Watts. If RMS were still used, the amps would probably be under 100 Watts.
 
OHMs are every bit as important to keep in mind as watts when pairing speakers to an amp.

Here's a little snippet on considerations when adding speakers to a existing amplified system
 
Indeed - actually, Mr Ohm was a clever chap wasn't he. Ohms, Volts, Amps and Watts - and Watts in AC circuit behave differently to DC circuits. We've used Amps X Volts = Watts for years, but it was never really that simple when transformers were involved. Close, but wrong sort of!
 
Your single mic input Flo' should be capable of driving the amplifier section to full power. As (Rob?) said, microphones produce "volts" (rms but we WILL come back to that later!) and the mixer will have an LED display showing the level at the monitor (not PA) outputs. Normally 0VU means a voltage out of +4dBu about 1 volt rms and the maximum output is likely +22dBu =10V rms. Power amplifiers, for technical reasons usually have a sensitivity of 1 to 2 volts rms for full output so you can see that one mic in one channel is easily capable of the full output of the mixer.

If you have the power output of am amp and the sensitivity* of the speakers and know how far they will be from the listener you can get a ball park SPL from https://mehlau.net/audio/spl/

Those Adam speakers are studio monitors not PA speakers and very good though they are would not produce enough level at distance for your purpose I am sure. If you ran them close to their limits they would probably just about work but I cannot see them lasting long. "Proper" PA speakers generally produce sound levels in excess of 120dB at one metre.

In the GOOD old days of hi fi amplifiers power levels were NOT specified as "rms watts" because there is no such thing. 'Watts into a resistive load (speakers are mostly resistive but just not quite enough to be bloody awkward!) is given by Vrms X Amps (I) or Vrms sqrd/R or Irms sqrd X R . The result is just watts. What SHOULD be specified is "watts continuous sine power" into a resistive load. I will admit though that this is a battle I have virtually given up on!

"rms" by the way is short for "Root Mean Squared" and is a way to represent the 'working' quality of a voltage or current. It is different for different waveforms. Sine wave rms is peak voltage x 0.707 For a square wave the peak and rms are the same.

*Speaker sensitivity is defined as Sound Pressure Level at one metre for one watt of input power. Speaker manufactures tend to use different input waveforms, often one of several noise "colours" and so it can be difficult to compare brands. The other problem is that speakers not being pure resistances it is difficult to define an input of exactly one watt. Often a voltage is quoted instead.


Dave.
 
Thanks everyone for the responses. All of this making somewhat more sense now.
 
ecc83 said:
Your single mic input Flo' should be capable of driving the amplifier section to full power. As (Rob?) said, microphones produce "volts" (rms but we WILL come back to that later!) and the mixer will have an LED display showing the level at the monitor (not PA) outputs. Normally 0VU means a voltage out of +4dBu about 1 volt rms and the maximum output is likely +22dBu =10V rms. Power amplifiers, for technical reasons usually have a sensitivity of 1 to 2 volts rms for full output so you can see that one mic in one channel is easily capable of the full output of the mixer.

If you have the power output of am amp and the sensitivity* of the speakers and know how far they will be from the listener you can get a ball park SPL from https://mehlau.net/audio/spl/

Those Adam speakers are studio monitors not PA speakers and very good though they are would not produce enough level at distance for your purpose I am sure. If you ran them close to their limits they would probably just about work but I cannot see them lasting long. "Proper" PA speakers generally produce sound levels in excess of 120dB at one metre.

In the GOOD old days of hi fi amplifiers power levels were NOT specified as "rms watts" because there is no such thing. 'Watts into a resistive load (speakers are mostly resistive but just not quite enough to be bloody awkward!) is given by Vrms X Amps (I) or Vrms sqrd/R or Irms sqrd X R . The result is just watts. What SHOULD be specified is "watts continuous sine power" into a resistive load. I will admit though that this is a battle I have virtually given up on!

"rms" by the way is short for "Root Mean Squared" and is a way to represent the 'working' quality of a voltage or current. It is different for different waveforms. Sine wave rms is peak voltage x 0.707 For a square wave the peak and rms are the same.

*Speaker sensitivity is defined as Sound Pressure Level at one metre for one watt of input power. Speaker manufactures tend to use different input waveforms, often one of several noise "colours" and so it can be difficult to compare brands. The other problem is that speakers not being pure resistances it is difficult to define an input of exactly one watt. Often a voltage is quoted instead.


Dave.
Click to expand...
The calculator you sent is extremely useful. Thanks so much!
 
flobeeblow45 said:
The calculator you sent is extremely useful. Thanks so much!
Click to expand...
You are very welcome but be aware that it is only the most approximate guide. As said, speaker sensitivities are not consistent across brands, amplifier outputs are subject to, shall we say, 'massaging' we won't say lies!

Then rooms vary in their sound absorbent qualities and of course, audiences are not at one distance from the speakers.

But, you has to start somewhere!

Dave.
 
ecc83 said:
You are very welcome but be aware that it is only the most approximate guide. As said, speaker sensitivities are not consistent across brands, amplifier outputs are subject to, shall we say, 'massaging' we won't say lies!

Then rooms vary in their sound absorbent qualities and of course, audiences are not at one distance from the speakers.

But, you has to start somewhere!

Dave.
Click to expand...
Got it, makes sense, thanks.
 
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