Page 1 of 2 12 LastLast
Results 1 to 15 of 21

Thread: Rethinking "Danger: Low Power"

  1. #1
    Senior Member Ducatista47's Avatar
    Join Date
    Jul 2005
    Location
    Peoria, Illinois
    Posts
    1,886

    Rethinking "Danger: Low Power"

    Remember this old JBL Pro white paper? http://www.jblpro.com/catalog/suppor...=246&doctype=3

    I always thought it flawed because it warns against, amongst other things, tweeters blowing out from clipped waveforms. Bipolar transistor amps I could see doing this, but tubes don't clip like that. So if you turn it way up and the tweeters blow anyway, what is doing it? This 1991 Rane paper wants us to believe another answer, and it makes sense to me. http://www.hotsound.com.br/clipping_effects.pdf Why would using a more powerful amp help? Because clipping is not destroying anything. Power is, through compression of the lower frequency output. It is when turning up the amp has insufficient energy to increase woofer loudness - but beau coup to feed more and more energy to the tweeters. If the amp is big enough, poof. Oddly, it means a tiny amp would lack the power to kill the tweeters, but a bigger amp could.

    A properly sized amp, by JBL standards, would not because the lower frequencies, indeed all frequencies, would keep getting louder. The theory is the listener would cry Uncle before the energy was sufficient to fry the tweeters. But it has little to do with the quality of the signal, just the quantity.

    Makes sense to me, how about you? Unrelated, I find this page to be very interesting. It is an almost zero BS take on amplification, listening, design and common sense sound engineering. All in the service of elucidating Gainclone amps. http://www.adx.co.nz/techinfo/audio/gainclone1.htm I enjoyed every word.
    Information is not Knowledge; Knowledge is not Wisdom
    Too many audiophiles listen with their eyes instead of their ears


  2. #2
    Senior Member Mike F's Avatar
    Join Date
    Feb 2011
    Location
    Montreal, Canada
    Posts
    279
    Would`nt the capacitors in the crossovers take care of any clipped/dc signals coming from an overdriven amp?

  3. #3
    Senior Member Ducatista47's Avatar
    Join Date
    Jul 2005
    Location
    Peoria, Illinois
    Posts
    1,886
    No doubt they would stop DC. I don't think they would stop Justin Bieber or other forms of distortion. Definitely would not stop the overpowering watts the Rane paper points to. It seems to be simple power - too much energy - that is the killer.
    Information is not Knowledge; Knowledge is not Wisdom
    Too many audiophiles listen with their eyes instead of their ears


  4. #4
    Senior Member
    Join Date
    Feb 2007
    Location
    Christchurch, NZ
    Posts
    1,400
    I cant say that I ever blew a high frequency driver from supplying too much power. In my experience I have found that things tend to blow when they are overdriven. Plenty of good clean power never hurt.

    Allan.

  5. #5
    Senior Member Ducatista47's Avatar
    Join Date
    Jul 2005
    Location
    Peoria, Illinois
    Posts
    1,886
    Quote Originally Posted by Allanvh5150 View Post
    I cant say that I ever blew a high frequency driver from supplying too much power. In my experience I have found that things tend to blow when they are overdriven. Plenty of good clean power never hurt.

    Allan.
    Yeah, overdriving is what this is all about. When the amp is not powerful enough to keep increasing the low frequency power with increasing gain, but has enough power to keep increasing the high frequency power (what amp doesn't?), the tweeters are overdriven. A really big amp is in theory going to make your ears bleed before too much energy goes to the tweeters. But I say never underestimate the "ability" of some JBL lovers to turn it WAY up despite things like pain and heart palpitation. The JBL literature usually included a warning that the speakers were capable of damaging hearing before speaker damage occurred, if the speakers were driven with sufficient clean power.
    Information is not Knowledge; Knowledge is not Wisdom
    Too many audiophiles listen with their eyes instead of their ears


  6. #6
    Senior Member BMWCCA's Avatar
    Join Date
    Feb 2006
    Location
    Virginia
    Posts
    7,743
    I blew an 075 back in 1969 or so. Back then JBL had that unconditional life-time warranty. They repaired it with a new coil and shipped it back for free with a note to check for a "high-frequency oscillation" in my amp. At that time it was a Kenwood receiver. I traded it in on a Fisher SA1000 which I played even louder with no problems, including playing my Gibson EBO bass through the system.

    Next was a Crown D150 which played those same speakers all through college including many a weekend when we'd put them out on the porch and play them to the Blue Ridge mountains so loud one time the Crown went into thermal shutdown (the old D150 without the faceplate so I just stuck a pencil underneath it to increase airflow and played for several more hours without incident). I have never fried a tweeter since, and that includes many "fragile" 035Ti's.

    I think I'm with JBL on this one.
    ". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."—Greg Timbers

  7. #7
    Senior Member grumpy's Avatar
    Join Date
    Oct 2003
    Location
    SoCal
    Posts
    5,742
    Interesting idea. I think things are not so simple, but I'm not selling limiters.
    Key is too much HF energy will indeed fry tweeters. I prefer adequate
    amplification (which IMO -can- vary by amp type) and education to limiters at home.

  8. #8
    Senior Member Don C's Avatar
    Join Date
    Apr 2003
    Location
    Santa Rosa CA
    Posts
    1,722
    A clipped waveform has a lot of harmonics that were not in the signal at the amplifier input. These can blow your tweeters with frequencies too high to even hear. Your speakers have a high pass filter to keep the low frequencies from getting to the tweeter, but no low pass filter to block higher frequencies.

  9. #9
    Senior Member 1audiohack's Avatar
    Join Date
    Jul 2007
    Location
    Las Vegas Nevada
    Posts
    3,092
    I remember reading the attached link by Charlie Hughes some time ago describing the formation of square type waves due to increasing distortion caused by lack of headroom in power amps. I don't remember if this article goes into the dramatic increase in heating the load/driver has to dissipate when driven with a clipped signal. I didn't reread it tonight but I remember having an AhHah moment near the end.

    All the best.


    http://www.excelsior-audio.com/Publi...DC_Content.pdf
    If we knew what the hell we were doing, we wouldn't call it research would we.

  10. #10
    Super Moderator yggdrasil's Avatar
    Join Date
    Dec 2004
    Location
    Våle, Norway
    Posts
    1,014
    Quote Originally Posted by Don C View Post
    A clipped waveform has a lot of harmonics that were not in the signal at the amplifier input. These can blow your tweeters with frequencies too high to even hear. Your speakers have a high pass filter to keep the low frequencies from getting to the tweeter, but no low pass filter to block higher frequencies.
    +1

    The effect of clipping is the creation of high frequency harmonics, hence more energy to the tweeter.
    Johnny Haugen Sørgård

  11. #11
    Senior Member Hoerninger's Avatar
    Join Date
    Jul 2005
    Location
    Germany
    Posts
    1,892
    Quote Originally Posted by Don C View Post
    .. but no low pass filter to block higher frequencies.
    Sometime somewhere I read that it is wise to include a series coil with a guitar speaker to acoid damage when clipping - but that is not a tweter.
    ____________
    Peter

  12. #12
    Senior Member rdgrimes's Avatar
    Join Date
    Aug 2008
    Location
    New Mexico, USA
    Posts
    2,216

  13. #13
    Senior Member DavidF's Avatar
    Join Date
    Apr 2003
    Location
    Sonoma County CA
    Posts
    946
    Quote Originally Posted by Ducatista47 View Post
    "...don't think they would stop Justin Bieber or other forms of distortion...."
    Jeez, you caught me off guard with that one. That would a bring a harsh resonance to the ear, indeed. Easy enough to remedy, thankfully.
    David F
    San Jose

  14. #14
    Senior Member Mike F's Avatar
    Join Date
    Feb 2011
    Location
    Montreal, Canada
    Posts
    279
    Quote Originally Posted by Don C View Post
    A clipped waveform has a lot of harmonics that were not in the signal at the amplifier input. These can blow your tweeters with frequencies too high to even hear. Your speakers have a high pass filter to keep the low frequencies from getting to the tweeter, but no low pass filter to block higher frequencies.
    That makes sense. A steep low pass filter ought to help in filtering out inaudible ultrasonics.

  15. #15
    Administrator Mr. Widget's Avatar
    Join Date
    Apr 2003
    Location
    San Francisco
    Posts
    9,720
    Quote Originally Posted by Don C View Post
    A clipped waveform has a lot of harmonics that were not in the signal at the amplifier input. These can blow your tweeters with frequencies too high to even hear. Your speakers have a high pass filter to keep the low frequencies from getting to the tweeter, but no low pass filter to block higher frequencies.
    Sure all of us know this... the point that Clark and the Rane Note is making, beyond possibly Rane's desire of selling limiters, is that this "fact" about clipping that we all ascribe to is really a theory and the fine people at Rane are proposing an alternative theory.

    That said, theory or not and clipping or compression aside, the fact is enough people have fried expensive tweeters with under powered amps that simply using a bigger amp if you must play it louder is the safest way to go. I'd suggest the point Rane is making is almost more of a semantic argument than a practical one.

    I fried my first set of LE85s back in the '70s with a 40wpc integrated amp... bought a Marantz 510 with over 300wpc and then proceeded to scare many a roommate and undoubtedly didn't do my ears any favors but never blew another tweeter.


    Widget

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Altec Santiago "A" to "B" surgery (perhaps)?
    By mhardy6647 in forum Lansing Product Technical Help
    Replies: 10
    Last Post: 11-25-2009, 12:08 PM
  2. c-56 model """dorian""" marble
    By colonne in forum Lansing Product General Information
    Replies: 4
    Last Post: 02-17-2006, 05:20 AM
  3. "The Tent Sale Blues' (sung to the tune "they don't ship to Canada no mo")
    By luxmanlover in forum Lansing Product General Information
    Replies: 11
    Last Post: 07-07-2003, 09:07 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •