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JBL SR4722 Power Ratings

Discussion in 'Sound, Music, and Intercom' started by Eboy87, May 5, 2006.

  1. Eboy87

    Eboy87 Well-Known Member

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    Ok, looked throught the technical manual on JBL's website. All it says for power rating is 600W @ 8ohms. It doesn't say whether this is program or peak. Is anybody familiar with these speakers who knows the power ratings? JBL's website wasn't much help, as the technical sheet was the only thing I could find. And no, I don't have the manual that came with them. I got them second hand from my church for free.

    Reason I ask is that I'm looking into new amps than my little dinky Soundtech thingy, and just realized that I had no idea what the continuous wattage is. Thanks in advance
     
  2. cutlunch

    cutlunch Active Member

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    I found a data sheet on the JBL website for the SR4722X/F which states that the 600 W was produced using continuous Pink Noise. So I would read this as 600W RMS. JBL is not likely to quote in anything but RMS figures.

    Hope this helps.
     
  3. Eboy87

    Eboy87 Well-Known Member

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    Yeah, that's what I thought. I didn't think of looking at other comparable models, as mine are quite old. I was hoping that it would have been peak, as it's gonna cost me an arm and a leg and perhaps my left hand to buy an amp that would power these running in stereo.
     
  4. soundman1024

    soundman1024 Active Member

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    I would probably consider bi-amping them before I would run them in stereo. That crossover is going to eat up some power. Is there a specific reason you want to run them in stereo?
     
  5. Eboy87

    Eboy87 Well-Known Member

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    Money. I can run in stereo, I found a QSC amp that will provide my power needs, but right now, all I can afford is one amp, and that's after I finish up the shows this summer. Right now most of my money is spent on gas and girlfriend.

    Eventually I'll bi-amp, I already have the DRPA as a x-over
     
  6. bryanr74

    bryanr74 Member

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    These speakers are rated at 600 watts.

    So you need an amp capable of generating 600 watts at 8 ohms or 1200 watts at 4 ohms.
     
  7. cutlunch

    cutlunch Active Member

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    This would just drive it but it would leave no safety margin to protect the speaker.

    Off the top of my head the common way of determining amplifier size is:

    Speaker wattage * 1.8 < amplifier wattage Range < Speaker wattage * 2.2

    For this case it gives an amplifier wattage range between 1000 - 1300 watts for 8 Ohms
     
  8. bryanr74

    bryanr74 Member

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    Giving the speaker more power to "protect" it is actually not exactly what you are doing. I typically pick amps that are a few like say 100 to 200 watts over the specs - and then back the amps down a bit - this is more to give the speaker headroom and protect the amp - more than the speaker.

    The only real way to protect a speaker is with a DSP/limiter. And a trained engineer that understands that you don't drive a speaker to it's limits. Instead if you need more SPL - add more speakers.

    You can just as easily hurt a speaker buy underpowering it and cranking the sound up above the headroom.
     
  9. AVGuyAndy

    AVGuyAndy Active Member

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    Right, so by suggesting buying a 600w amp is bad advice.
     
  10. Eboy87

    Eboy87 Well-Known Member

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    I'm shooting for at least a 1000W @8ohm amp. Right now the QSC PLX3402 is the highest I can get at 700 W @ 8ohm. Does anybody know of any comparable amps in the price range of the PLX that would do the job? I'm also trying to stay away from Behringer, even though their amps are exact copies of the QSC ones.
     
  11. AVGuyAndy

    AVGuyAndy Active Member

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    How about 2 RMX1450s bridged?
     
  12. bryanr74

    bryanr74 Member

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    No it isn't. Since 1200 watts is all that is needed.

    I guess it is up to them - if they want to listen to a teenager or a professional.

    All that is needed is an amp capable of 1200 watts at 4 ohms. It is fine if there are a few more watts.
     
  13. bryanr74

    bryanr74 Member

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    A good amp to look at would be Crown XTi. You should be able to find them around 450-700 range.

    The XTi 4000 is capable of 1200 watts at 4 ohms. Not sure what this amps sells for but the XTi at a local dealer here was $489.00 at our cost. I figure that in most dealers you can get it for around $550. So the XTi 4000 should be around 650 or so.
     
  14. AVGuyAndy

    AVGuyAndy Active Member

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    Running a speaker that is 600W RMS, off a 600w amp will likely clip the amp on the peaks. Clipping kills speakers. And that is why you don't match speakers like that. All of my speakers are run off amps with 1.5-2x the RMS power of the speakers.

    Your comments regarding young people on this site are out of line. This forum is for high school tech students. Take your negativity elsewhere.
     
  15. Eboy87

    Eboy87 Well-Known Member

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    I'm taking a long hard look at them, but I already have a DRPA for signal processing.

    Also, when they say an amp is rated at x number of watts at 8 ohms, is that 8 ohms per channel? Basically what I'm asking is if I put speakers rated at 8 ohms, one into channel 1 and two into channel 2, into the amp, will I be running at 8 ohms or 4 ohms?
     
  16. Mayhem

    Mayhem Senior Team Emeritus Premium Member

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    Headroom is to protect your speakers. Under powering a speaker is the easiest way to destroy it. The amp will most likely clip when trying to get the speakers to drive to an adequate volume and this will destroy the speakers.

    Once you have the headroom however, you can also damage speakers by over driving them but since the volume will be there, you should be able to hear this easier and correct it.

    Also, because the amp is rated at 600 Watts @ 8 Ohms, you will not necessarily get 1200 Watts @ 4 Ohms. The power to impedance ratio is not directly proportional and doubling one will not always halve the other. This is why amps will often list the output for different loads and you may see 375W @ 8 Ohms and 600W @ 4 Ohms; or 800W @ 8 Ohms and 1200W @ 4 Ohms.

    The best thing to do is look at the minimal load on an amp as this is the important factor. Thus if you have 1200 Watts at 4 Ohms as the minimal loading, it is a safe bet that you will have slightly more than half the available power if you double the speaker impedance.

    Going below the minimal load value is going to damage your amplifier.

    You amp is putting our power and expecting the speaker to “absorb” a certain percentage of this, with a small amount returning to the amp. Once the speaker impedance drops below the rated level, the amp gets more power back and will begin to overheat. It is important to remember also that a speaker is not a resistive load. Its characteristics will change depending on what is happening to the audio signal.

    The load only changes when speakers are added together on the same channel. So if you have an 8 ohm speaker on channel A and an 8 ohm speaker on channel B, both channels have an 8 ohm load.

    If you wired both 8 ohm speakers together in parallel, you would now have a 4 Ohm load and if you wired them together in series, you would have a 16 Ohm load.
     
  17. tenor_singer

    tenor_singer Active Member

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    I had a TD friend humorously use this analgy for underpowering an amp. I was young, cocky and was arguing with him that I should get a less powerful amp because I didn't want to crank things up and ruin the speaker by putting more energy through it that it could handle. He said...

    "Donny (I HATE that form of my name) just because you have a higher wattage amp driving a lower wattage speaker doesn't mean that you'll damage the speaker... unless you're stupid. You can put a V-10 turbo charged engine in a Honda Civic and be fine. Your issues will happen when you decide to drive with a lead foot. Just like you wouldn't want to attempt to drive that same Civic with a 33-cc weed eater engine on a freeway."

    I miss him.
     
  18. BillESC

    BillESC Well-Known Member Premium Member

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    The rule of thumb for touring systems is twice the amp for the speakers RMS rating.

    Therefore your 600w RMS speakers should be driven by an amplifier capable of delivering 1200w.
     
  19. fosstech

    fosstech Active Member

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    I'm not sure how much it costs (I'd guess it's about the same as the PLX3402), but I'll vote for the Crown CTs2000. [email protected] 8 ohms. And less current draw from your wall sockets (7A 1/8 power pink noise @ 4 ohms as opposed to 12A). And it's exactly 1000W @ 8 ohms.
     
  20. Eboy87

    Eboy87 Well-Known Member

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    Dale, that would have been perfect, but I don't think I can scrounge up $2000, and if I could, I'd buy a bigger board.

    Thanks Mayham. I didn't think that it would be different, I just assumed (correctly) that each side would draw 8ohms. But basically all I knew about amps was to buy one that's almost double the rating of your speakers
     

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