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Author Topic: confused by power ratings!!!  (Read 6054 times)

Bryan Booth

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confused by power ratings!!!
« on: January 25, 2011, 12:37:27 pm »

We currently have 2 Yamaha sv115 for our tops, and 2 Yamaha Br12s and 2 Wharfdale powered 12s for monitors.  Power wise we have: 1 QSC GX5, 1 QSC 1450, and 1 QSC 2450.  We want to add a Subwoofer to the mix, and possibly down the road add another.  We think that the best set up for what we currently have is running the tops bridged mono out of the 1450, and the BR12s in parallel out of the GX5.  That leaves us with the 2450 to power the sub(s).   I guess our question are: What sub would you recommend to match the 2450, and does our current set up look ok?   Thank you in advance.   
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Doug Fowler

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Re: confused by power ratings!!!
« Reply #1 on: January 25, 2011, 03:34:19 pm »

We currently have 2 Yamaha sv115 for our tops, and 2 Yamaha Br12s and 2 Wharfdale powered 12s for monitors.  Power wise we have: 1 QSC GX5, 1 QSC 1450, and 1 QSC 2450.  We want to add a Subwoofer to the mix, and possibly down the road add another.  We think that the best set up for what we currently have is running the tops bridged mono out of the 1450, and the BR12s in parallel out of the GX5.  That leaves us with the 2450 to power the sub(s).   I guess our question are: What sub would you recommend to match the 2450, and does our current set up look ok?   Thank you in advance.

Check it out....

http://www.qscaudio.com/products/amps/advanced_amp_selector.htm
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Bryan Booth

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Re: confused by power ratings!!!
« Reply #2 on: January 25, 2011, 04:11:33 pm »

on the Qsc specifications chart for the rmx series amps...does the term Stereo mode(both channels driven) mean that the listed watts are per channel or would you divide that by 2?
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Patrick Tracy

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Re: confused by power ratings!!!
« Reply #3 on: January 25, 2011, 04:13:20 pm »

on the Qsc specifications chart for the rmx series amps...does the term Stereo mode(both channels driven) mean that the listed watts are per channel or would you divide that by 2?

Per channel.

Rob Spence

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Re: confused by power ratings!!!
« Reply #4 on: January 25, 2011, 05:42:58 pm »

We currently have 2 Yamaha sv115 for our tops, and 2 Yamaha Br12s and 2 Wharfdale powered 12s for monitors.  Power wise we have: 1 QSC GX5, 1 QSC 1450, and 1 QSC 2450.  We want to add a Subwoofer to the mix, and possibly down the road add another.  We think that the best set up for what we currently have is running the tops bridged mono out of the 1450, and the BR12s in parallel out of the GX5.  That leaves us with the 2450 to power the sub(s).   I guess our question are: What sub would you recommend to match the 2450, and does our current set up look ok?   Thank you in advance.   
In general one chooses an amp to properly power a speaker, not the other way around.
Figure out what speakers you need, then see if you have an amp already. If not, you do some trading (sell/buy).
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rob at lynxaudioservices dot com

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Bryan Booth

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Re: confused by power ratings!!!
« Reply #5 on: January 25, 2011, 06:59:02 pm »

In general one chooses an amp to properly power a speaker, not the other way around.
Figure out what speakers you need, then see if you have an amp already. If not, you do some trading (sell/buy).

so I guess i would need to figure out how much power I would need that sub to push?  In your opinon, taking into account our current set up and the fact that venues vary greatly, how much sub do we need...I am sooo new to this... please be patient w/me:)
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Patrick Tracy

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Re: confused by power ratings!!!
« Reply #6 on: January 25, 2011, 10:26:43 pm »

so I guess i would need to figure out how much power I would need that sub to push?

No, choose a speaker that meets your needs in terms of SPL and coverage, then choose an amp to adequately power it. Other things to factor in are size, weight, cost and efficiency.

Rob Spence

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Re: confused by power ratings!!!
« Reply #7 on: January 25, 2011, 10:50:00 pm »

so I guess i would need to figure out how much power I would need that sub to push?
Subs don't push power!

Ok, slowing down here....

Subs consume power. Specs for a sub will talk about how loud they can go (max SPL) and how loud they will be with 1 Watt (sensitivity).
If you have 2 subs next to each other they will be 6dB louder than just one sub (assuming they are getting enough power).

So, as Patrick says, choose a sub (or set of them) that gets loud enough, is the size you need, and is priced within your budget. Then figure out how much power is needed to drive the sub to the levels you need. Since not everyone has to drive their speakers to the max, you may find that your existing amp will do for now until you can afford a larger one.
Also note that the "power" doesn't come without side effects.  If you want or need monster subs running loud, then you will need lots of electricity to make it work.

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rob at lynxaudioservices dot com

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Bryan Booth

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Re: confused by power ratings!!!
« Reply #8 on: January 26, 2011, 11:55:07 am »

Right, excuse my layman verbage...Subs consume power.   I guess I was basically just looking for conformation that the way we are running our equipment is optimal for what we have.  At the same time looking for advise, from people more experienced than I as to the next step in expanding our rig.   So, I have taken into consideration that I should find a sub to fit our needs and then fit an amp to that.  That being said, or needs vary greatly as we play very small rooms to outdoor events, so I guess I am looking for a "general purpose" sub. ( I realize that probably sounds ridiculous to you guys).   Knowing what little I do...Subs consume more power than full range speakers, so I am guessing that I would need a sub that should handle more power than my mains.  Mains are 1000w peak, we run them at 700w, so we need a sub that can handle more than 1000w.  Is my train of thought on the right track?
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TJ (Tom) Cornish

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Re: confused by power ratings!!!
« Reply #9 on: January 26, 2011, 12:35:00 pm »

Watts are not [necessarily] an indiation of volume.  In other words - a 1000 watt speaker may not be louder than a 500 watt speaker.

When comparing speakers, the best information comes from a frequency plot of the box's output at a certain power level, which can be multiplied by the speakers power capacity to get a guestimate of the speaker's real-world performance.

There are many pitfalls here - this is not a simple problem. Some subs go louder than others, some have flatter frequency responses, some play lower than others.

In addition to this, you don't necessarily want the loudest speaker.  Size and weight are large factors - if the loudest sub weighs 350lbs and is a 4' cube, you're probably going to think twice about putting that in the back of your minivan.

I would start with this question:

"Our usual gig is for [v] number of people in an [indoor/outdoor] environment.  Our transportation is [w], so we have certain size constraints.  Our budget is x, our existing equipment is [y], and our electrical power capacity is [z].  Are there any speakers that could work well within these limits?"

Once you get some feedback, you can revise your criteria and expectations depending on what the real-world choices really are.
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Paul G. OBrien

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Re: confused by power ratings!!!
« Reply #10 on: January 26, 2011, 12:44:59 pm »

  Knowing what little I do...Subs consume more power than full range speakers, so I am guessing that I would need a sub that should handle more power than my mains.  Mains are 1000w peak, we run them at 700w, so we need a sub that can handle more than 1000w. Is my train of thought on the right track?

Yeah you're on the right track though you made another common statement that probably doesn't reflect reality. "Mains are 1000w peak, we run them at 700w". The running them at 700w part is only true if the amp is pushed to maximum output all the time, at anything below this the actual power level the speakers are dissipating could be as little as 1/2 to 1/4 of that level.

And while it is true in general that low frequencies take more power to reproduce this only holds true if the subs have the same sensitivity as your mains, if they are more sensitive then it is entirely possible they will require equal or less amp power than the mains to achieve the desired sound balance. For example your Yamaha mains have a 98db sensitivity, if you want 3db more sub output than your mains you need 98db subs that can handle 3db more input power than your mains, or subs with 102db sensitivity and the same power handling, or subs with 105db sensitivity and 1/2 the power handling.
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Patrick Tracy

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Re: confused by power ratings!!!
« Reply #11 on: January 26, 2011, 12:55:05 pm »

What TJ said. To simplify, watts is the number you consider last, after you've chosen your sub or at least narrowed the choices to the ones with the required output, size, weight, cost etc.

ProSoundWeb Community

Re: confused by power ratings!!!
« Reply #11 on: January 26, 2011, 12:55:05 pm »


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