Boffa
Joined: 27/03/08
Posts: 27
Loc: Essex
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Wattage ratings?
#781246 - 22/10/09 05:29 PM
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How do you work out the output from a PA system? I have been given a rider to do the sound
for a band and they have specified at least 3K for the Venue. I know a lot of people say
that it is all about SPL and to be honest it has never been an issue for me as my gear
seems plenty loud enough for the clubs I do. My two foh amps put out 900w a side into 4
ohms and my 2 subs are 350w rms at 4 ohms, 700 continuous, 1400 peak, as are my two
tops.(That is each amp drives a pair of cabs) So what power do I have there as this band
seem to think that its important. I am thinking of upgrading my cabs and getting a HK
Actor active rig, but although it's rated at 3200w I cant work out how they arrive at
this. Any help would be apreciated.
Steve
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Bob W
Joined: 30/09/09
Posts: 17
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Re: Wattage ratings?
[Re: Boffa]
#781250 - 22/10/09 06:09 PM
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It is all about SPL, speaker efficiency, speaker coverage (dispersion angle of speaker
covers the seating area of the venue and minimizes reflections?), - not watts. We have
responded to these types of riders with: We can cover XX+% of the seating area at XYdBA or
greater volume level. For example -3dB efficiency of a speaker difference to another
requires doubling the power to get the same volume. A 1500 watt system can be louder or
equivalent to a 3000 watt system, neither of which seems like a lot of power in the first
place.
--------------------
Bob
cascadingwatersaudio.com
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Paul Soundscape
Joined: 27/06/06
Posts: 722
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Re: Wattage ratings?
[Re: Boffa]
#781252 - 22/10/09 06:16 PM
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just add it up... The actor has 2 tops at 600w each so thats 1200w and 2
powered subs at 1kw each so thats 2000w totals 3.2kw What impedance are
your speakers? Wattage a poor way of measuring "loudness". Spl is where it's
at, and efficiency of the speakers, Don't worry too much about rider specs,
they're normally a load of BS and normally written by someone clueless or just taking the
piss!
-------------------- Live Sound and Studio Engineer
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GaryM
Joined: 06/11/08
Posts: 618
Loc: Dundee, UK
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Re: Wattage ratings?
[Re: Boffa]
#781253 - 22/10/09 06:16 PM
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Yep. Measuring the electrical power coming out of the amps doesn't tell you how the PA
system will sound. You could turn up with just some amps and dummy loads and have
satisfied a demand for a 3 kW rig.
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Boffa
Joined: 27/03/08
Posts: 27
Loc: Essex
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Quote PaulEvansMusic.co.uk:
just
add it up...
The actor has 2 tops at 600w each so thats 1200w
and 2 powered
subs at 1kw each so thats 2000w
totals 3.2kw
The Actor also has two passive 500w subs. So is it based around
the amps, obviously not. There must be some sort of formula for this sort of thing but
agreed, its all BS
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Zan Man
Joined: 21/12/08
Posts: 41
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Re: Wattage ratings?
[Re: Boffa]
#781262 - 22/10/09 06:45 PM
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I couldn't "do the maths" either, as as Boffa states the Actors have a 500 watt passive
cab. I need help on that one too......Speaking about the HK Actors..... Does anyone know
what the difference between the Mark 1 and the Mark 2 versions? I have tried researching
this, but even the HK website does neither mention nor explain it. Having never yet heard
either version, just how good sonically are they? If we were to go down the active route,
and possibly "opening up a can of worms", what would be an alternative F.O.H. active
system with the same, if not better, spec. and price? 
-------------------- It's my most vivid memory - and you're telling me it never happened?
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Zan Man
Joined: 21/12/08
Posts: 41
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Re: Wattage ratings?
[Re: Zan Man]
#781263 - 22/10/09 06:47 PM
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Forgot to ask for an equivalent sonic quality too.....
--------------------
It's my most vivid memory - and you're telling me it never happened?
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Paul Soundscape
Joined: 27/06/06
Posts: 722
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Re: Wattage ratings?
[Re: Boffa]
#781279 - 22/10/09 09:53 PM
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total wattage output is down to the amps, though it is also dependant on the
impedance of the speakers, Some of my subs run at 4ohm and my sub amp's output
at 4 ohm is 1500watts per channel, 2 subs = 3kw though my tops run at 8ohm and
my top amp's output at 8ohm is 500 watts per channel. 2 tops = 1kw total 4kw, HK stuff sounds nice but IMO unnatural. Active alternatives could be the
forty and fifty line systems or the fohhn xperience slightly pricier though.
-------------------- Live Sound and Studio Engineer
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Boffa
Joined: 27/03/08
Posts: 27
Loc: Essex
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Thanks Paul, so if both my amps put out 900w per channel at 4 ohms and I have 2 subs at 4
ohms and 2 tops at 4 ohms then am I right in thinking, that, that equates to 3600w?
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Paul Soundscape
Joined: 27/06/06
Posts: 722
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Re: Wattage ratings?
[Re: Boffa]
#781282 - 22/10/09 10:18 PM
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yes, I'm assuming this is all RMS figures? did they state that on their rider? other wise
you could turn up with a 1000w RMS system and say its rated at 4kw "peak" power.
-------------------- Live Sound and Studio Engineer
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Boffa
Joined: 27/03/08
Posts: 27
Loc: Essex
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Like I said Paul, They simply said a 3k rig, and having done the venue a few times before
and knowing it can handle the size, I know it'll be, no problem. I was curious as to what
my rig would put out, in this "my rig is 10k" world. It really dosn't matter what the
figures say, but what it sounds like, surely?
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Paul Soundscape
Joined: 27/06/06
Posts: 722
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Re: Wattage ratings?
[Re: Boffa]
#781287 - 22/10/09 10:55 PM
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certainly is, we had 20k at glasto on the park stage, but that was 16 boxes of EAW
per side, and not just 4 times louder than a "5k" rig.
-------------------- Live Sound and Studio Engineer
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