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Can the L112 really take 300 watts ?

Discussion in 'The Lansing Legacy' started by qguy, Jul 24, 2018.

  1. qguy

    qguy Super Member

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    Can the L112 really take 300 watts ?

    Although I would not want to be in the same room if this happens, I am curious if manufacturers ratings are really accurate. I asked this as I have another loudspeaker rated at 200 watts, but the woofer bottomed out using a 160 wpc receiver, brand and model of said loudspeaker shall not be disclosed, it is not a JBL or a member of the Lansing family :)
     

     

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  2. spark1

    spark1 Super Member

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    There are no standards for speaker power ratings. Even when provided by the manufacturer, the ratings are often not specified as continuous vs peak. Also, it seems that when both peak and continuous ratings are provided, the difference between the two often seems questionable, given that peak power output from amp when reproducing a music signal will generally be 9-12dB greater than continuous power (which suggests that peak ratings should be much higher than the continuous rating).

    As for the JBL L112; the owner's manual does not claim the ability to handle 300 watts of continuous power. Rather, it recommends that for best performance, they be used with an amplifier with enough power to handle transients without clipping (or, more realistically, with minimal clipping), and suggests a maximum of no more than 300 watts (RMS sine wave rating)...which equals 600 watts at peak.

    To allow a reasonable amount of headroom for transient peaks in the music signal (thereby minimizing clipping distortion, as recommended by JBL), such an amp would need to be limited (via the volume control) to approximately 40-60 watts of continuous/RMS output. Effectively, this is probably not far from the L112's continuous power handling capability.
     
    Last edited: Jul 24, 2018
    Zonker92 and Alobar like this.
  3. qguy

    qguy Super Member

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    That explains all the burnt voice coil on ebay :)
     
  4. spark1

    spark1 Super Member

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    BTW; at a continuous output from the amp of 30 watts or so, in your living room and at 8-10 feet away, you'd be getting a steady output of 100dB or thereabouts, with peaks of 110dB or more (assuming the amp has the necessary power). That's painfully loud, and can damage your hearing.

    If the amp doesn't have the needed power and is heavily clipping instead, power to the tweeters will continue to rise disproportionately as the amp is pushed further into clipping, and if pushed far enough they will be damaged.
     
    Last edited: Jul 24, 2018
  5. Gibsonian

    Gibsonian Super Member

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    Bottoming out a woofer is frequency and amplitude related. Watts rating is strictly power the coil can handle before burning up.

    The 300 watt rating sounds like amplifier recommendation, and one I would agree with so you don't clip within the power handling range. I like to have 1.5 to 2.0x amp size to speaker handling, relatively speaking. Then it's all about knowing your limitations, and having a bit of self control.
     
  6. Chris Brown

    Chris Brown Super Member

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    My JBL L150s share many things in common with the L112 (Same woofer, "same" mid, similar tweeter) and I was able to push my Yamaha M-2 (240wpc) to it's limits with them. I switched to using bridged P2201 amps (approx 700wpc) and I believe it was an improvement. I push quite a bit of power through them on a regular basis.

    As has been said, bottoming out the woofer is more a matter of frequency. Lower frequencies require more woofer excursion and at a certain point you exceed the Xmax of the woofer. It's fully possible to bottom out a woofer without exceeding the max power the voice coil can handle, and conversely, it's possible to exceed the max power the voice coil can handle without bottoming out the woofer. In some cases, such as systems using a crossover that routes very low frequencies away from the speakers and to a subwoofer instead, it can make it more practical to push the speakers closer to their power limits without worry about bottoming anything out. It, of course, also depends a lot on what content you are playing and if you are using EQ, etc.
     

     

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  7. zebra03

    zebra03 All Audio - NO BS

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    I have run my L112' solo with my Adcom GFA 5500 with no problem . It actually made me realize what great speakers they were .
     
  8. yamaha53

    yamaha53 New Member

    Messages:
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    Location:
    Raleigh, NC
    I am currently pushing my JBL L112's with a luxman R117 with no problems. The specs say 160 watts per channel with 4.5 db headroom. So there is no telling what is going to them when I am really jamming. I was originally trying to push them with my Yamaha CR2020 but the Luxman edged out the Yammy
    in this battle. I will also agree on what great speakers they are. I would say YES

    . jblmomma.jpg
     
  9. toddalin

    toddalin Super Member

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    2,326
    I will say that an L112 needs lots more watts than an L200/L300/equivelent due to the difference in sensitivity.
     
  10. seamas

    seamas Active Member

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    I have had my l112's maxed out with both a yamaha m70 and sansui g901db and no probs.tweeters will smoke if albums have a lot of ticks.if you max the low end just crossover(bx63)to an inexpensive 4645.even my l7's can't handle low(20's)frequency maxed out without being crossed over.4645 takes the place of a chair though.doesn't matter cause when its cranked up,i am standing.
     
  11. spark1

    spark1 Super Member

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    Do you mean that you had the M70 volume (gain) all the way to max? If so, then by definition wouldn't you be clipping a music signal pretty severely?
     

     

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  12. Chris Brown

    Chris Brown Super Member

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    No, those are attenuation controls. They aren't meant to be used as volume control. Nothing wrong whatsoever leaving them at max (no attenuation) unless you have a reason not to. The M-70 is meant to be used with a preamp, which would control the volume for the system.

    You might use attenuation controls if you had multiple amps in stereo hooked up to the same preamp, and the speakers hooked up to one amp were louder than the speakers hooked up to the other amp; you could dial down the attenuation controls on the louder amp so that they match. Or if the system was getting loud too fast using only a tiny range of the volume control on the preamp, you might dial down the attenuation controls on the amp(s) to give you more useful range on the volume control. With the amp's attenuation controls at "max" it's simply passing along the signal from the preamp output without cutting anything out (no attenuation).
     
  13. spark1

    spark1 Super Member

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    I read the post to say that he was running the amp such that the speakers were getting its full output...in which case there would be little left for transient peaks.
     
  14. seamas

    seamas Active Member

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    Location:
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    Back in the 80's I ran a CD player into my Yamaha c-70,m-70 and I would run it up to where it would show maxed out(300w I believe)for a second or two on peaks.I wouldn't do that with sub 30 hz.Only time I destroyed a woofer was in 83,I set my turntable on the speaker and at low volume regenerative feedback pushed the cone past it limits before I could shut it off.Sent the whole speaker to fix as it was under warranty.
     
  15. twiiii

    twiiii Addicted Member

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    If you can find a detailed manual for the L112 there should be an explanation. It will give the bandwidth of the test and the crest factor of the filtered pink noise used. Most of the time the crest factor is 6 db or 4 times the true rms rating. Plus the rating is with the power distributed across the drivers, not to just the woofer or mid for example. So depending on the efficiencies of the individual drivers the woofer usually receives the biggest share of the power of the 300 watts, the mid second and the tweeter 3rd, but not always so again refer to the JBL info sheet. Most likely the woofer may take the full power for a brief time, but if all the power is concentrated on either the mid or tweeter the drivers will fail if the levels remains high. Fortunately music normally has a HF roll-off and that saves tweeters . I admit it is rare to see speakers from that period of time that can handle that much power using a single woofer, mid and tweeter. Another issue is what percentage of the spectrum each drive covers and relative to the other drivers. Keeping the amp from clipping is very important for the life of the tweeter, mid and crossover. JBL has been making woofers that can handle well over 300 watts for a long time, but they are usually 15 or 18 inch models with large 4 inch voice coils and very tough suspension parts and voice coils. They can take a beating and keep on, and it looks like some of the technology has drifted down to the L112. That said JBL had some creative ways of measuring their speakers back in the 70's that really didn't measure up that well.
     
    Last edited: Oct 6, 2018
  16. Chris Brown

    Chris Brown Super Member

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    The woofer itself, the 128H, is only actually rated for 100 watts according to JBL Pro documentation: http://www.jblproservice.com/pdf/Thiele Small Parameters/Theile Parameters.pdf

    My L150 and 4412 (128H-1) speakers use that woofer also and I'm pretty sure I've put more through it than that on a regular basis (even taking into account loss via the crossover, etc). It's just important to keep in mind that the thermal limits of the voice coil and the mechanical limits of the suspension are two different things. As you increase the power to the woofer, you are increasing the risk to both (depending on content, EQ, and other variables of course). If you were to use a subwoofer with an external crossover or similar that directed the lowest frequencies away from the woofers in the speakers, then the risk of exceeding mechanical limits would be drastically reduced and you could get away with getting much closer to, or even exceeding the voice coil's official thermally-limited maximum electrical input limit.

    I'm only saying that because it seemed that bottoming out the woofer was the thread starter's primary concern, as opposed to how much power the speaker can actually handle. You could probably bottom out a 128H with significantly less than 100 watts if the person was listening to bass-heavy content using unreasonable levels of bass-boost or similar. The 128H is an amazing woofer; not a subwoofer. Many don't seem to understand the difference.
     
    Last edited: Oct 6, 2018

     

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  17. sKiZo

    sKiZo Hates received: 8642 Subscriber

    I would qualify that with "300 watts of clean, instantaneous power". Probably a good idea to have a fire extinguisher handy if you try that with "continuous power". <G>

    PS ... a lot of power goes into making silence as well.

    ?

    Watts are also about control. It can take 10 times the watts to STOP a cone at that exact moment that a note achieves perfection.
     
  18. spark1

    spark1 Super Member

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    Can you elaborate on this, please? I don't understand how this would be the case?
     
  19. sKiZo

    sKiZo Hates received: 8642 Subscriber

    OK - you've got a static woofer cone just sitting there. Apply watts to get it moving and create a specific frequency. Now throw a new frequency at it in the same range. More watts are applied to both overcome the existing momentum of the driver cone AND convert it's movement to create the new frequency. The more complex the audio passage, the more power may be required to control the cone exactly for sonic purity. The more power applied at that point, the greater the impact, definition, and clarity in that range.

    I think that kinda sorta made sense? ;-}
     
  20. spark1

    spark1 Super Member

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    Unfortunately, it did not...at least not to me. I probably don't know enough to understand.

    What is "a new frequency in the same range"?

    In any case it seems to me that a change in frequency does not necessarily change amplitude. But when it does, it would seem that amplitude (and therefore power) may go up or down. I don't see how transitions in frequency imply more power...it depends upon the amplitude of those signals.

    As for controlling the cone for sonic purity...not sure what this means, but in my simple view it would seem that power drawn is pretty much a function of amplitude and impedance. I've seen claims that having power beyond what is required to accommodate desired amplitude (including transient peaks) somehow delivers better performance, but have never understood how power not drawn can have any effect.

    I certainly understand the need for enough headroom to accommodate transients at a given level of continuous/average output, but just can't grasp how unused power results in better sound quality (again, assuming enough power to avoid any clipping). I think one of the supporting arguments has to do with claims that running the amp closer to its maximum capabilities results in increased THD, but I don't know if this is truly the case.

    As I said, I probably just don't have enough fundamental knowledge to grasp these more complex topics.

    EDIT: corrected a typo
     

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