ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: [1] 2  All   Go Down

Author Topic: How do I tell how much power?  (Read 6265 times)

Gregg Aleo

  • Newbie
  • *
  • Offline Offline
  • Posts: 7
How do I tell how much power?
« on: January 23, 2013, 09:34:31 am »

My band has a sound system we use for small gigs- it consists of (4) JBL EON powered speakers (each speaker says 175 watts)- tied to a Mackie board.  First question is- how do I find out roughly how much power this entire system puts out? Second question is this:
I've been tasked with "running the sound" for a high school show- THey want me to use their system- Here are the specs (from what I can tell):
They have a rack with (2)Yamaha power amps in it- a 12 channel mixing board, crossover, and 2 sets of non powered Yorkville speakers (which looks like a sub in one cabinet and then mid/horn in the other)- The back of the sub says 400 watts and back of mid cabinet says 300 watts.
I'm guessing the school system is more powerful than mine- but I wasn't sure how to calcuater total power and difference between powered and non-powered speakers- thanks
Logged

Tim McCulloch

  • SR Forums
  • Hero Member
  • *
  • Offline Offline
  • Posts: 20830
  • Wichita, Kansas USA
Re: How do I tell how much power?
« Reply #1 on: January 23, 2013, 10:58:19 am »

My band has a sound system we use for small gigs- it consists of (4) JBL EON powered speakers (each speaker says 175 watts)- tied to a Mackie board.  First question is- how do I find out roughly how much power this entire system puts out? Second question is this:
I've been tasked with "running the sound" for a high school show- THey want me to use their system- Here are the specs (from what I can tell):
They have a rack with (2)Yamaha power amps in it- a 12 channel mixing board, crossover, and 2 sets of non powered Yorkville speakers (which looks like a sub in one cabinet and then mid/horn in the other)- The back of the sub says 400 watts and back of mid cabinet says 300 watts.
I'm guessing the school system is more powerful than mine- but I wasn't sure how to calcuater total power and difference between powered and non-powered speakers- thanks

Before you get answers, you will need to go to your profile and put your real first and last names in the "Name" field or the mods will lock/delete your post.
Logged
"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Gregg Aleo

  • Newbie
  • *
  • Offline Offline
  • Posts: 7
Re: How do I tell how much power?
« Reply #2 on: January 23, 2013, 11:26:05 am »

ok thanks Tim!
Logged

Tim McCulloch

  • SR Forums
  • Hero Member
  • *
  • Offline Offline
  • Posts: 20830
  • Wichita, Kansas USA
Re: How do I tell how much power?
« Reply #3 on: January 23, 2013, 01:37:27 pm »

ok thanks Tim!

You're welcome.  The real name policy helps keep this place from becoming Harmony Central...

Systems don't "put out power" nor is the amount of current delivered to a speaker's terminals an absolute indicator of how much Sound Pressure Level the speaker will produce.

You should probably do some reading in the Lab Lounge forum (where this thread will be soon), as there are several current threads about loudspeaker performance and specifications.  Look for posts on "Understanding rig coverage..." and "Understanding speaker specs."  There is some bad info in them (corrected by other posters), but there is also a wealth of genuine info.  These threads may help you discover the answers to your questions.

Also the forums have a search engine, or you can use Google's advanced search to limit returns to these boards by using "forums.prosoundweb.com" as a filter.  The site also has preserved much of the contents that goes back to 2004 so you can have nearly endless hours of reading pleasure.

It's hard to say if the installed system at the school is better, equal or worse than yours.  The maintenance of sound systems in schools is a crap shoot, and it usually depends on who is responsible for it; regardless of their title, if the person in charge of the equipment cares, it might be okay... but it's hard to say for sure.  It might be a good idea to take a known-working mic and cable to the school, plug in and bark into the mic and see what it sounds like; also take a music player and run some tunes and check to see that all speakers in their system are putting out sound.

How "powerful" a system is perceived is also be very subjective as different folks have different expectations based on their musical preferences and culture.  In the scenario you present, if the installed system is in good working order I'd be inclined to use it for a couple of reasons.  First, it's already there and will save you the time and effort of transporting and setting up all your gear.  Second, it has subwoofers which will add greatly to the perception of power.  Third, the client wants you to.  You're providing a service so you're better off if you can do it the way they want.
Logged
"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Jerome Malsack

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1339
Re: How do I tell how much power?
« Reply #4 on: January 23, 2013, 03:03:01 pm »

What is the size of the venue.  I was in a single gym basket ball court that has 6 rows of bleachers on one side and the stage on the other long side.  We had standing room only for more than 1000 people. 

My system was 2 EV TL15-1 subs with 450 watt each and 2 EV S15-3A with 300 watts each for top.

I would not want to run a rock show with that power in that crowd.  For the middle school band and choir it was workable.  The school PA was a 500 watt amp.

If this is a theater type function the system is good once the crowd settles down.  More would be best. 
Logged

g'bye, Dick Rees

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 7424
  • Duluth
Re: How do I tell how much power?
« Reply #5 on: January 23, 2013, 03:22:55 pm »


My system was 2 EV TL15-1 subs with 450 watt each and 2 EV S15-3A with 300 watts each for top.




Jerome...

I don't mean to pick on you as the OP was asking about "power" and you and many others will respond with talk of watts.  As Tim pointed out, it's

SPL

not watts. 

Watts have nothing to do with power delivered over a given area. That is figured out with the amount of sound whatever wattage is involved will put out.  SPL.

While all this is helpful, sooner or later one of the real masters of measurement and application like Ivan Beaver will come on and further illuminate the issue by explaining the efficacy of measurements, even SPL. 

But basically, propagation of sound through the air falls off at the same rate for all speaker systems, so the nominal SPL capability of the speaker(s) will allow you to figure out what you need to cover a given area with the desired amount of sound.......SPL.

It matters not whether you use a 100W speaker capable of producing 120dB SPL or an 800W speaker capable of producing 120dB SPL.  They both put out the same "amount" of sound, one requiring more power measured in watts than the other to produce the same result. 
Logged
Pay no attention to the man behind the curtain...

Art Welter

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1620
Re: How do I tell how much power?
« Reply #6 on: January 23, 2013, 04:06:13 pm »


Jerome...

I don't mean to pick on you as the OP was asking about "power" and you and many others will respond with talk of watts.  As Tim pointed out, it's

SPL

not watts. 

Watts have nothing to do with power delivered over a given area. That is figured out with the amount of sound whatever wattage is involved will put out.  SPL.

But basically, propagation of sound through the air falls off at the same rate for all speaker systems, so the nominal SPL capability of the speaker(s) will allow you to figure out what you need to cover a given area with the desired amount of sound.......SPL.
 
Dick,

Sound pressure level may also be  measured in acoustic watts:
140 dB SPL = 100 acoustic watts
130 dB SPL = 10 acoustic watts
120 dB SPL =1 acoustic watt
110 dB SPL =.1 acoustic watt
100 dB SPL =.01 acoustic watt
90 dB SPL =.001 acoustic watt

When one notices that a speaker with a 100 dB 1 watt one meter sensitivity (fairly high) driven with one watt is putting out .01 acoustic watt, one realizes how much power is converted to heat rather than sound.

Although the inverse distance law dictates a 6 dB SPL loss for doubling of distance outdoors from a omnidirectional source, the propagation of sound does not fall off at the same rate for all speaker systems.
A well designed and arrayed system can show as little as 3 dB SPL loss for doubling of distance.

That said, air attenuation can reduce HF level by 10 dB or more in addition to the inverse distance law.
 
I don't mean to pick on you, but it is more fun than picking on noobs :^).

Art
« Last Edit: January 23, 2013, 04:26:46 pm by Art Welter »
Logged

g'bye, Dick Rees

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 7424
  • Duluth
Re: How do I tell how much power?
« Reply #7 on: January 23, 2013, 04:14:05 pm »

Dick,

Sound pressure level may also be  measured in acoustic watts:
140 dB SPL = 100 acoustic watts
130 dB SPL = 10 acoustic watts
120 dB SPL =1 acoustic watt
110 dB SPL =.1 acoustic watt
110 dB SPL =.01 acoustic watt

Although the inverse distance law dictates a 6 dB SPL loss for doubling of distance outdoors from a omnidirectional source, the propagation of sound does not fall off at the same rate for all speaker systems.
A well designed and arrayed system can show as little as 3 dB SPL loss for doubling of distance.

That said, air attenuation can reduce HF level by 10 dB or more in addition to the inverse distance law.

I don't mean to pick on you, but it is more fun than picking on noobs :^).

Art

You can pick on me as much as you want, old timer.  I'll just go b**** to your brother about it.

In re the falling off of sound over distance:  I didn't want to get into the exceptions to the rule, which is why I prefaced that remark with "basically".  Still, it's good to go by the rule.

The thrust of my reply was to disabuse both the OP and the particular respondent of using the watts figures quoted for amps and speakers as a basis for figuring out the ability of their system to provide sound for a given area.

Thanks for the acoustic watts citation, though.

I'll say hi to Roy for you.
Logged
Pay no attention to the man behind the curtain...

Art Welter

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1620
Re: How do I tell how much power?
« Reply #8 on: January 23, 2013, 04:24:49 pm »

You can pick on me as much as you want, old timer. 

The thrust of my reply was to disabuse both the OP and the particular respondent of using the watts figures quoted for amps and speakers as a basis for figuring out the ability of their system to provide sound for a given area.

Old timer? I'll dance on your grave :^).

If one uses the watt figures quoted for amps and speakers and sensitivity, and use the inverse distance law and coverage pattern, you have the basis for determining SPL in a given area.

Then, use an inverse age formula with around 100 dB maximum SPL required for old timers, and 130 dB for young know it all types.

10 acoustic watts or .01 acoustic watts, simple.

Art
Logged

g'bye, Dick Rees

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 7424
  • Duluth
Re: How do I tell how much power?
« Reply #9 on: January 23, 2013, 04:29:22 pm »

Old timer? I'll dance on your grave :^).

Art

Get in line.  Dime a dance.

PS

Ant says to say hi.
Logged
Pay no attention to the man behind the curtain...

ProSoundWeb Community

Re: How do I tell how much power?
« Reply #9 on: January 23, 2013, 04:29:22 pm »


Pages: [1] 2  All   Go Up
 



Page created in 0.142 seconds with 22 queries.