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Thread: 4345 power requirements

  1. #1
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    4345 power requirements

    Hello,

    what is the optimum power of an amplifier to run the mid-high section of a 4345-monitor?

    The 4345 can be used with seperate amps for the 2245 and the mid-high section. There is a lot of talk about the 2245, but how much is actually required to run the midwoofer and horns? Assuming that a active-crossover is used between the woofer and high-mid section at ~290hz....

    Best regards,
    Olaf

  2. #2
    Senior Member BMWCCA's Avatar
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    Not sure what's "optimum" but for the past 10-years I've used a Crown PS200 (100-wpc) on the top end and PS400 (200-wpc) on the bottom. Remember Greg's advice to bypass the bi-amp switch for better performance.

    Mine play plenty loud and I've never seen the IOC lights on either Crown even flicker. JBL specs call for maximum input power on the upper end of 100-watts but—in typical JBL fashion—call for a 200-watt-per-channel amp to gain that 3dB of headroom.

    ". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."—Greg Timbers

  3. #3
    Administrator Robh3606's Avatar
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    100 watts should be fine. Ran my 4344 clones that way no issues at all. Would force me out of the room before the amps would clip.

    Rob
    "I could be arguing in my spare time"

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    100 watts is actually a lot more than I would´ve expected.

    I thought you could get away with something like 20-30 watts.
    The mid-high section has a higher sensitivity than the bass. And I´ve once read, that you need about 6db less of power in the midrange compared to the bass. In my assumption that would mean aprox. 10db less amp-power for the mid-high-section compared to the bass-section.

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    For a while I was using a 50w Krell KSA50S for the top end of my 4345 clone. I didn't think more was required.

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    Senior Member Ducatista47's Avatar
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    Nelson Pass Power.

    Twenty-five watt First Watt F5 here. I doubt it has ever been asked to put out five. Very efficient system.
    Information is not Knowledge; Knowledge is not Wisdom
    Too many audiophiles listen with their eyes instead of their ears


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    Senior Member markd51's Avatar
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    A little bit of headroom is always a nice thing to have on hand.

    Or go with the smaller brother, the 7B3.

    https://www.tonepublications.com/rev...er-amplifiers/

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    Junior Member speakermaker's Avatar
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    Name:  DSC_0001 (1).jpg
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    Ich nutze für den Bass eine Nakamichi PA 7 und für MHT eine Nakamichi PA 5 EII , ich benutze 2123H ,bei denen ich bis auf 200Hz mit der
    Ü-Frequenz runter gehe, durch die wandnahe Aufstellung ergibt sich ein durchaus glatter Frequenzgang . Meine 2123 laufen in 15 Litern Volumen.
    Grüße aus OWL

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    Senior Member markd51's Avatar
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    I was funnin a bit with my last post, and can understand if splitting the speaker system by bi-amping-etc of course the mids and tweets don't need 100's of watts of power. How much can they take, and as well, how much can your ears take? LOL

    Still, headroom (watts and current) provides enough clean power without worry of ever clipping.

  10. #10
    Administrator Robh3606's Avatar
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    200 watts is what is recommended on the JBL Techsheet including headroom for a 4345 above 290 Hz. At home? The difference between 25 watts vs 200 watts is about 9dB of additional headroom. So you could only hit 111dB instead of 120dB!

    Rob
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    Awesome to get to hear what everyone is using with their 4345, thanks!

    The Spec-sheet clearly states 200watts (including headroom), can`t argue with that.

    I totally believe the 10" midwoofer will handle this kind of power. But I actually doubt it will see this kind of powerlevels in realitiy.
    The 2245 is about 3db less efficient than the mid-high-section. Therefor 100watts for the top, 200watts for the bottom. But as I mentioned earlier, mid frequencies are supposed to need aprox. 6db less of power than low frequencies. Or is this snake-oil audio-talk?

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    Senior Member markd51's Avatar
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    Quote Originally Posted by Dr.db View Post
    Awesome to get to hear what everyone is using with their 4345, thanks!

    The Spec-sheet clearly states 200watts (including headroom), can`t argue with that.

    I totally believe the 10" midwoofer will handle this kind of power. But I actually doubt it will see this kind of powerlevels in realitiy.
    The 2245 is about 3db less efficient than the mid-high-section. Therefor 100watts for the top, 200watts for the bottom. But as I mentioned earlier, mid frequencies are supposed to need aprox. 6db less of power than low frequencies. Or is this snake-oil audio-talk?
    What it all basically comes down to in a nutshell, is power handling capacity, and perceived volume at different frequencies.

    It's like, walk into a small venue to play guitar in some group with a 85w Fender Twin Reverb cranked to 9, and they'll throw you out of the place on your ear because you'll be killing everyone in the place.

    Whereas, it wasn't uncommon for bass amps to be throwing out 600, 800,1000 watts.

    Besides too little wattage where you might risk making an Amp clip, which is dangerous for any driver, too much wattage will toast-fry drivers, x-overs, and even L-Pads aren't immune either.

    Besides "quantity", good sound does benefit from quality amplification. I'm not of the camp that believes all amplifiers sound the same.

  13. #13
    Senior Member Ian Mackenzie's Avatar
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    Hi Olaf,

    The responses are correct.

    It depends on a number of factors such as your listen preferences and the genre of music you listen to. If you have a small room and you only listen to folk music the power demands are going to be relatively small. But if you have a large room and play heavy metal then a margin of headroom is common sense. For example if you play quite loud continuously in a big room the program power could be 50 watts. But the peaks might be 6 dB higher. So that means a 200-300 watt amplifier rating to avoid the possibility of clipping and sending damaging square waves to the drivers.

    Technically the mid Lpad gives a -3 dB cut on the zero position. There is also a fixed pad on the output of the 2122. The 2122 filter has some passive voltage gain of about 2db because it’s a bandpass filter.

    If you turn the mid L pad up full you reduce power needed for the same sound level by 3 dB or 50%.

    I would suggest a minimum of 100 watts be default. But it’s a case by case situation beyond that.

  14. #14
    Senior Member Ducatista47's Avatar
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    Whenever these massive monitors are discussed re: headroom and clipping avoidance, my first and last thoughts are about being cautious about listening volume. It is not a great idea to drive JBL monitors in the home to any point where you have to worry about clipping. The standard warning in the handouts was that your hearing will be permanently damaged before the monitors will distort. Think about it.

    The other thing, those old white papers about clipping damage to the drivers were penned in the early solid state amp era. Those crappy amps would produce really damaging signal when cranked. Use something better and you likely would not hear distortion before the onset of hearing damage no matter how careful you think you are being.

    I confess that at many listening volumes I have heard, the first thing I reach for is earplugs.
    Information is not Knowledge; Knowledge is not Wisdom
    Too many audiophiles listen with their eyes instead of their ears


  15. #15
    Senior Member markd51's Avatar
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    Quote Originally Posted by Ducatista47 View Post
    Whenever these massive monitors are discussed re: headroom and clipping avoidance, my first and last thoughts are about being cautious about listening volume. It is not a great idea to drive JBL monitors in the home to any point where you have to worry about clipping. The standard warning in the handouts was that your hearing will be permanently damaged before the monitors will distort. Think about it.

    The other thing, those old white papers about clipping damage to the drivers were penned in the early solid state amp era. Those crappy amps would produce really damaging signal when cranked. Use something better and you likely would not hear distortion before the onset of hearing damage no matter how careful you think you are being.

    I confess that at many listening volumes I have heard, the first thing I reach for is earplugs.
    Rock Concerts, I've been to quite a few. An ELP concert with the introduction of their Brain Salad Surgery release will make 20 pairs of those 4345 Speakers sound like a 9V Battery Pocket Transistor Radio. Ask me how I know!

    https://www.youtube.com/watch?v=wz6Mj8cROJw

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