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Which amps should i use to run a stereo pa setup?


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#1 sbird

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Posted 13 February 2006 - 03:48 AM

hello! i am a new member to this forum, and i have a lot of questions! hopefully you guys can/will help me, because my brain hurts! blink.gif  Anyhow, here's the deal: i have a yamaha mg32/14fx non-powered mixer, and two jbl as4725anw 2-way pa cabs. i have been largely unsuccessful at obtaining info on the speakers, although i luckily stumbled across a pdf for the specs. i know less is more, but i'm not sure what specs you guys need for these items to proceed with helping me choose the right amp, so here goes...
********************************************************************
Specs for mixer:
Power supply:120v AC, 60 Hz
Power consumption:120w
Frequency characteristics(Master output):20Hz-20kHz+1 dB,-3dB@+dBu, 600(ohms? the little horseshoe thing [sorry, i'm a musician, not a sound guy!] unsure.gif )(with gain set at min)
Total harmonic distortion:</=0.1%(THD+N)@+14dBu, 20Hz-20kHz, 600(little upsid down horseshoes smile.gif )
Sensitivity:-60dBu
Hum and Noise:(20Hz-20kHz)
_____________________________________________________________________
Specs for cabs:
Nominal impedance:8 ohms
Power capacity: 600w con't. pink noise
Freq. range:35Hz to 18kHz(-10dB)
Sensitivity: 97 dB SPL(1 watt @ 1 meter)
crossover freq.:1.1kHz
DC resistance: 3.2 ohms+/- 8% Aluminum wire
Hi freq transducer:25mm. 1 in. exit pure titanium compression driver
********************************************************************
well, there you have it! cool.gif i hope that you can help me- i've never really had the responsibility of sound man(woman, actually smile.gif ), so any good advice would be greatly appreciated! i think(? dry.gif ) i have fairly good equipment and do not want to screw it up!my buddy has great sound for his band and not only reccomended that i go stereo as opposed to mono through the board, which i guess requires two power amps, but he also highly recommended you guys to get the job done. hope i gave you enough info, and if anyone knows a thing about those cabs, pass it on! i couldn't find anything but the spec manual online. (this whole rig is obviously brand new to me, tips or feedback appreciated!) i just want it to run perfect and sound like a million bucks! wink.gif not too much to ask, right? well, you guys are the experts, and as long as the advice is sound ( biggrin.gif and i can afford to), i'll take it! i don't want to keep upgrading as i go along or blow any of my equipment! thank you for taking the time to read this, hope i don't look too dumb (although, when it comes to this stuff, i sure ain't a genius or anywhere near it!) . i look foward to hopefully receiving a really helpful response or ten! thanks so much-
  ps jane dough rocks!                                                           -sbird

#2 sbird

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Posted 13 February 2006 - 10:16 AM

QUOTE(sbird @ Feb 13 2006, 03:48 AM)
hello! i am a new member to this forum, and i have a lot of questions! hopefully you guys can/will help me, because my brain hurts! blink.gif  Anyhow, here's the deal: i have a yamaha mg32/14fx non-powered mixer, and two jbl as4725anw 2-way pa cabs. i have been largely unsuccessful at obtaining info on the speakers, although i luckily stumbled across a pdf for the specs. i know less is more, but i'm not sure what specs you guys need for these items to proceed with helping me choose the right amp, so here goes...
********************************************************************
Specs for mixer:
Power supply:120v AC, 60 Hz
Power consumption:120w
Frequency characteristics(Master output):20Hz-20kHz+1 dB,-3dB@+dBu, 600(ohms? the little horseshoe thing [sorry, i'm a musician, not a sound guy!] unsure.gif )(with gain set at min)
Total harmonic distortion:</=0.1%(THD+N)@+14dBu, 20Hz-20kHz, 600(little upsid down horseshoes smile.gif )
Sensitivity:-60dBu
Hum and Noise:(20Hz-20kHz)
_____________________________________________________________________
Specs for cabs:
Nominal impedance:8 ohms
Power capacity: 600w con't. pink noise
Freq. range:35Hz to 18kHz(-10dB)
Sensitivity: 97 dB SPL(1 watt @ 1 meter)
crossover freq.:1.1kHz
DC resistance: 3.2 ohms+/- 8% Aluminum wire
Hi freq transducer:25mm. 1 in. exit pure titanium compression driver
********************************************************************
well, there you have it! cool.gif i hope that you can help me- i've never really had the responsibility of sound man(woman, actually smile.gif ), so any good advice would be greatly appreciated! i think(? dry.gif ) i have fairly good equipment and do not want to screw it up!my buddy has great sound for his band and not only reccomended that i go stereo as opposed to mono through the board, which i guess requires two power amps, but he also highly recommended you guys to get the job done. hope i gave you enough info, and if anyone knows a thing about those cabs, pass it on! i couldn't find anything but the spec manual online. (this whole rig is obviously brand new to me, tips or feedback appreciated!) i just want it to run perfect and sound like a million bucks! wink.gif not too much to ask, right? well, you guys are the experts, and as long as the advice is sound ( biggrin.gif and i can afford to), i'll take it! i don't want to keep upgrading as i go along or blow any of my equipment! thank you for taking the time to read this, hope i don't look too dumb (although, when it comes to this stuff, i sure ain't a genius or anywhere near it!) . i look foward to hopefully receiving a really helpful response or ten! thanks so much-
  ps jane dough rocks!                                                           -sbird
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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
update:  ohmy.gif oops looks like i forgot some thing: for the speakers-
sensitivity:97dBl SPL*
*1 watt (2.83V RMS) @ 1 meter
********************************************************************sorry, I hope I'm in the right forum for this discussion! unsure.gif

#3 MichaelsAudio

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Posted 13 February 2006 - 01:04 PM

You should search through the JBL website for more info on your speakers, www.jblpro.com and then you need to decide whether you intend to run your speakers "passive" or to use an active crossover network and "bi-amp" your system.  Using the amplifier matching rules from JBL and from elsewhere in this forum, to run "passive" you need one stereo amplifier capable of producing 960 watts to 1600 watts per channel into 8 ohms.  [(Continuous power rating X 2) X (.8 to 1.25) for range].  Crown has several amplifiers in this range.  If you wish to "bi-amp" your system, you will need two stereo amplifiers and an active crossover network to feed them.  From the JBL website you will find the power ratings for the individual components in your speaker boxes and apply the same rules above for amplifier ratings.  If you ask me directly, I would steer you toward "bi-amping" your system, as your budget allows, and I would recommend the Crown I-Tech series.  I-Tech 6000 for Lows and I-Tech 4000 for Highs.  You can always buy the Lows amp first and use it to run "passive" until your budget allows you to purchase the other amplifier.  Good Luck...

Michael Oliver - Third Ear Sound Company, Richmond, CA

#4 sbird

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Posted 13 February 2006 - 02:19 PM

QUOTE(MichaelsAudio @ Feb 13 2006, 01:04 PM)
You should search through the JBL website for more info on your speakers, www.jblpro.com and then you need to decide whether you intend to run your speakers "passive" or to use an active crossover network and "bi-amp" your system.  Using the amplifier matching rules from JBL and from elsewhere in this forum, to run "passive" you need one stereo amplifier capable of producing 960 watts to 1600 watts per channel into 8 ohms.  [(Continuous power rating X 2) X (.8 to 1.25) for range].  Crown has several amplifiers in this range.  If you wish to "bi-amp" your system, you will need two stereo amplifiers and an active crossover network to feed them.  From the JBL website you will find the power ratings for the individual components in your speaker boxes and apply the same rules above for amplifier ratings.  If you ask me directly, I would steer you toward "bi-amping" your system, as your budget allows, and I would recommend the Crown I-Tech series.  I-Tech 6000 for Lows and I-Tech 4000 for Highs.  You can always buy the Lows amp first and use it to run "passive" until your budget allows you to purchase the other amplifier.  Good Luck...

Michael Oliver - Third Ear Sound Company, Richmond, CA
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------------------------------------------------------------------------------------------------thank you- what are the advantages of "bi-amping" vs. "passive"amping? I'm confused about this stereo thing, but my buddy's band sounds great with this method... i currently have a Kustom amp (borrowing but afraid to apply) that rates as follows:4 ohm min. load, 120 v,200 w, 260 wrms.... no clue what this means- will it blow my system to test it through this ? i haven't tried it yet....the speakers are rated at 600w each...thanks for your interest in my multiple problems/questions!

#5 Bud Bolf

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Posted 14 February 2006 - 10:12 AM

Hi Sbird,
  
You have the Mixer and the Speakers, now you need a Crossover / Speaker Processor and Power Amps.

Lets check out some options available to you.

1) If you are just planning on running these speakers "Full Range"
    and not adding Subs at a later time, then you could get a Power Amp
    such as a CE4000 that has a (HPF) High Pass Filter and (LPF) Low Pass Filter.
    Set the HPF to 40 or 50Hz and leave the Low Pass Filter Flat.
    I would then run the amp Bridged at 4 Ohms.
    By running Mono and connecting your speaker cabs together in Parallel
    and to the Amp, instead of two 8 Ohm speaker cabs, the Power Amp will  
    now see a single 4 Ohm Load.
    The CE4000 is rated at 2800 Watts (RMS) 4 Ohms Continuous in Bridged Mono.
    Since both cabs are connected together they will share the output and
     each cab will get 1400 Wrms.
    Your Cabs are rated at 600 Watts Continuos (RMS) and
    with a formula of Power to Speaker ratio of approx. 1.5 to 2x's
   the Continuous (RMS) your cabs should be powered with between 900 and 1200
   Watts RMS.  
   Your 2 cabs together at 4 Ohms (not single cabs at 8 ohms) and  
   because together they now share the output, now need between 1800 to 2400
   watts RMS / Continuous.
   The CE4000 Bridged puts out 2800 Watts RMS / Continuous, so it is 200
   watts above the 2x rating of 2400 watts, but if you set your "Gain Structure"
   correctly and do not Clip the amp's inputs, you should be OK.
    The JBL's will take it.

2) You get a Crossover or a DriveRackPA or 260 and use them to Process your
    Output from the Mixer.
    For a little more than the cost of an Analog Crossover you can get a
    DriveRackPA, a little more than a DRPA and you could get a DriveRack 260.
   The DriveRack will set your EQ (RTA), Parametrics, Crossover,  
   Limiter, Anti Feedback, Delay's and let your speakers sound great.
   Also help if you add Subs later and or Bi-Amp your JBL Cabs.
   As far as Bi-Amping your JBL's, you will need a delay between your
   horn and drivers. Another DriveRack feature is that you can save
   to a preset each particular adjustment that you make from room
    to room, Venue to Venue.
   When you return to that room, Venue Bar, etc. you pull up that preset
   ( I name my preset after the Venue, like So and so's sportsbar)
    and you are good to go!
    You deserve to check this out for yourself.
     When I was in your position it is what I did and it was one of the single best
    decisions that I made for my Sound!
    You could then get any amp that fits your power needs.
   Such as a  XS900 Power Amp that has no Filters, HPF or LPF but that's
   ok, because your Crossover or DriveRack will handle the Filters.
   The XS900 is rated at 2500 Watts RMS in Bridged Mono, so in Parallel each of
   the JBL's would get 1250 Watts Continuous.
   I use the XS900 and I also have the CE4000 on my Subs

3) To run your JBL's in Stereo then you need a Power Amp
    that will put out between 900 to 1200 watts per Channel at 8 ohms
    For #1 above you need a Power amp with Filters or at least a HPF.
    For #2 above you just need a Power Amp.

As far as your friend's recommendation of a Stereo vs Mono PA system.
I do not see a real reason to beat yourself up over it and your pocket book
or purse as the case may be, to make this happen.
Unless you have some special stereo effects needed with your music
or you play a lot of canned music, such as a DJ,
in which Stereo could be a nice effect.
If you play "Live Music" then Mono is just fine.
I have Stereo tops and Mono Subs in my R&R Band, but I only
have Stereo tops because I happen to have the Amp to drive my cabs that way.
I would have no problem running pure Mono and many do!
I have a Mackie 24/4 VLZPro Mixer and everything is fed wether straight to L&R or via my Sub Faders
ALL channels end up going evenly to the Left and Right Main Fader.
In other words there is no Stereo imaging in my PA, it's what you could say is a MONO / STEREO. You know what I mean?
I do not have Channels fed more to the Left or Right, both sides
are getting the exact same feed, thus a Mono feed to a per channel amp.
You and I can call that Stereo tops, but it really is not!
Not what you truly think of as Stereo, as is the case when you put on some Headphones and listen to a CD,
and hear Stereo nuances that were created in the Studio and panned Left and Right.
I'm sure that you understand what I'm saying.

I see that you play Acoustic Guitar and sing.
What type of Music do you / Band play?

For either scenario listed above, now is the time for you to decide
what the future holds for you and your PA's needs.
It will help you in your decision's today, and in the Future.

I hope this helps,
       Bud
PS. I need to add that there are others that would say, that you can rent a $30,000 PA and Engineer per gig for less than it takes for you to do it yourself.
Decisions,decisions,decisions.
There are many here to help, as well as at other Forums such as Pro Sound Web
should you embark on your Quest for Great Live Sound.
We are ALL after the same thing!!!
Here is a link to PSW, the Lounge is a good place to learn.
PSW The Lounge

#6 sbird

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Posted 14 February 2006 - 10:57 PM

QUOTE(Bud Bolf @ Feb 14 2006, 10:12 AM)
Hi Sbird,
 
You have the Mixer and the Speakers, now you need a Crossover / Speaker Processor and Power Amps.

Lets check out some options available to you.

1) If you are just planning on running these speakers "Full Range"
    and not adding Subs at a later time, then you could get a Power Amp
    such as a CE4000 that has a (HPF) High Pass Filter and (LPF) Low Pass Filter.
    Set the HPF to 40 or 50Hz and leave the Low Pass Filter Flat.
    I would then run the amp Bridged at 4 Ohms.
    By running Mono and connecting your speaker cabs together in Parallel
    and to the Amp, instead of two 8 Ohm speaker cabs, the Power Amp will   
    now see a single 4 Ohm Load.
    The CE4000 is rated at 2800 Watts (RMS) 4 Ohms Continuous in Bridged Mono.
    Since both cabs are connected together they will share the output and
     each cab will get 1400 Wrms.
    Your Cabs are rated at 600 Watts Continuos (RMS) and
    with a formula of Power to Speaker ratio of approx. 1.5 to 2x's
   the Continuous (RMS) your cabs should be powered with between 900 and 1200
   Watts RMS. 
   Your 2 cabs together at 4 Ohms (not single cabs at 8 ohms) and 
   because together they now share the output, now need between 1800 to 2400
   watts RMS / Continuous.
   The CE4000 Bridged puts out 2800 Watts RMS / Continuous, so it is 200
   watts above the 2x rating of 2400 watts, but if you set your "Gain Structure"
   correctly and do not Clip the amp's inputs, you should be OK.
    The JBL's will take it.

2) You get a Crossover or a DriveRackPA or 260 and use them to Process your
    Output from the Mixer.
    For a little more than the cost of an Analog Crossover you can get a
    DriveRackPA, a little more than a DRPA and you could get a DriveRack 260.
   The DriveRack will set your EQ (RTA), Parametrics, Crossover, 
   Limiter, Anti Feedback, Delay's and let your speakers sound great.
   Also help if you add Subs later and or Bi-Amp your JBL Cabs.
   As far as Bi-Amping your JBL's, you will need a delay between your
   horn and drivers. Another DriveRack feature is that you can save
   to a preset each particular adjustment that you make from room
    to room, Venue to Venue.
   When you return to that room, Venue Bar, etc. you pull up that preset
   ( I name my preset after the Venue, like So and so's sportsbar)
    and you are good to go!
    You deserve to check this out for yourself.
     When I was in your position it is what I did and it was one of the single best
    decisions that I made for my Sound!
    You could then get any amp that fits your power needs.
   Such as a  XS900 Power Amp that has no Filters, HPF or LPF but that's
   ok, because your Crossover or DriveRack will handle the Filters.
   The XS900 is rated at 2500 Watts RMS in Bridged Mono, so in Parallel each of
   the JBL's would get 1250 Watts Continuous.
   I use the XS900 and I also have the CE4000 on my Subs

3) To run your JBL's in Stereo then you need a Power Amp
    that will put out between 900 to 1200 watts per Channel at 8 ohms
    For #1 above you need a Power amp with Filters or at least a HPF.
    For #2 above you just need a Power Amp.

As far as your friend's recommendation of a Stereo vs Mono PA system.
I do not see a real reason to beat yourself up over it and your pocket book
or purse as the case may be, to make this happen.
Unless you have some special stereo effects needed with your music
or you play a lot of canned music, such as a DJ,
in which Stereo could be a nice effect.
If you play "Live Music" then Mono is just fine.
I have Stereo tops and Mono Subs in my R&R Band, but I only
have Stereo tops because I happen to have the Amp to drive my cabs that way.
I would have no problem running pure Mono and many do!
I have a Mackie 24/4 VLZPro Mixer and everything is fed wether straight to L&R or via my Sub Faders
ALL channels end up going evenly to the Left and Right Main Fader.
In other words there is no Stereo imaging in my PA, it's what you could say is a MONO / STEREO. You know what I mean?
I do not have Channels fed more to the Left or Right, both sides
are getting the exact same feed, thus a Mono feed to a per channel amp.
You and I can call that Stereo tops, but it really is not!
Not what you truly think of as Stereo, as is the case when you put on some Headphones and listen to a CD,
and hear Stereo nuances that were created in the Studio and panned Left and Right.
I'm sure that you understand what I'm saying.

I see that you play Acoustic Guitar and sing.
What type of Music do you / Band play?

For either scenario listed above, now is the time for you to decide
what the future holds for you and your PA's needs.
It will help you in your decision's today, and in the Future.

I hope this helps,
       Bud
PS. I need to add that there are others that would say, that you can rent a $30,000 PA and Engineer per gig for less than it takes for you to do it yourself.
Decisions,decisions,decisions.
There are many here to help, as well as at other Forums such as Pro Sound Web
should you embark on your Quest for Great Live Sound.
We are ALL after the same thing!!!
Here is a link to PSW, the Lounge is a good place to learn.
PSW The Lounge
View Post


hi bud thanks for the great input! i have been in a discussion forum at harmony central (these guys know their stuff, but converting it to english? consider me a preschooler! i got called clueless! )well, like i told them, when it comes to this stuff i am, which is why i am on these forums to begin with! don't want to blow myself or my equipment up! help from the pros? i'll take it! i'm a chick- i ain't afraid to ask for directions!  biggrin.gif wait till i start asking for wiring diagrams!  blink.gif  anyhow, my band's name is jane dough, newly expanded from an acoustic duo to five freaks playing acoustic plugged-in mayhem! our two newest members (the percussion / keys section go figure dry.gif)(no offense !)  want funk not folk but we currently do some dylan, grateful dead, bluegrass/ old time , blues, and originals, as well as other stuff along those lines. the boys in the back want funk, and i mistakenly picked up a bass at practice the other day- oh boy, here we go! with three leos in the mix, everyone's trying to drive! (luckily, i'm one, too! cool.gif  ) we're usually a little harder than coffee shop stuff, people who hear our demo often think we're on electrics, but we aren't! those are really callus driven riffs! tongue.gif  i can put a cig out with my fingers on my left hand! anyhow, gotta run! i'll absorb all your advice and return to the trenches here in a bit ! cu there!