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Thread: How loud can I play an Alnico driver?

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    How loud can I play an Alnico driver?

    I have read on this forum that the Alnico drivers demagnetize due to large voice coil currents. This means that I could possibly demagnetize the driver if playing too loud.

    However, I haven't found on the topics how much would be loud enough? What are the large currents for these drivers to demagnetize?

    Can I drive a JBL L300 (with 2231A) with a McIntosh MC402 at loud levels? I like to play loud and usually the power meter goes to the 40-400W range.

    How long for can I drive these speakers at very loud levels without ruining anything?

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    Heat

    It's all about heat, not necessarily about loud. If the voice coil heats the pole piece and thus the magnet till it's hot, then you have an issue.

    Loud peaks on wide dynamic range material may very well result in less average wattage dumped on the magnet than moderately loud highly compressed material.

    Back in the day a simple Altec A-7 pair would cover a 400 seat movie house and last for decades before the magnets had to be charged.

    Kent

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    Senior Member Lee in Montreal's Avatar
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    A small amp that clips continuously will send DC. Then DC will turn the coil into a toaster wire. That will heat up the Alnico magnet, which will lose its charge over time.

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    If I use 400 watt clean power there would be no DC sent, but could still heat up the Alnico?

    The L300 brochure states 300W power handling for the Alnico 136A and 400W for the Ferrite 136H. This means I could use 300 watt continously without heating up?

    Quote Originally Posted by Lee in Montreal View Post
    A small amp that peaks continuously will send DC. Then DC will turn the coil into a toaster wire. That will heat up the Alnico magnet, which will lose its charge over time.

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    Heather [Senorita member] hjames's Avatar
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    Quote Originally Posted by otenmsa View Post
    If I use 400 watt clean power there would be no DC sent, but could still heat up the Alnico?

    The L300 brochure states 300W power handling for the Alnico 136A and 400W for the Ferrite 136H. This means I could use 300 watt continously without heating up?
    You would soon have hearing issues running 300 watt continuous power (at serious volume) on those speakers.
    2ch: Oppo, Acurus RL-11, JBL 240ti, Heath AS101, Carver TFM-25,Von Schweikert VR4
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    I didn't say I would listen to the L300 driven by 300 watts continuous power. I asked if the driver would be capable of handling this amount of power/current, since it is on official JBL L300 specifications/brochure. If that is correct, would be some sort of guarantee from JBL that the Alnico wouldn't demagnetize if kept driven under this rated power.

    Quote Originally Posted by hjames View Post
    You would soon have hearing issues running 300 watt continuous power (at serious volume) on those speakers.

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    Degmag?

    Quote Originally Posted by otenmsa View Post
    I have read on this forum that the Alnico drivers demagnetize due to large voice coil currents. This means that I could possibly demagnetize the driver if playing too loud.

    However, I haven't found on the topics how much would be loud enough? What are the large currents for these drivers to demagnetize?

    Can I drive a JBL L300 (with 2231A) with a McIntosh MC402 at loud levels? I like to play loud and usually the power meter goes to the 40-400W range.

    How long for can I drive these speakers at very loud levels without ruining anything?
    This is a trick question, right?

    You can play a loudspeaker with an AlNiCo magnet as loud as one with a mud magnet. The question is, why would anyone play a loudspeaker so loud as to worry about degaussing the magnet? Before that happens your voice coil would suffer a melt down if not disassociate itself from the gap.

    I have never heard of completely degaussing a magnet structure due to excessively high levels, and I don't believe it's possible to do so. AlNiCo magnets do get warm, and over time under abuse they would lose a bit of their flux density, but not completely. I'd say, over a span of forty years under normal use a decrease might be measured on a Gauss meter, but nothing the human ear would detect.

    I used to own four L300's that I rescued from a Disco, and the most chronic problem they had were the load resistor leads in the networks breaking off at the circuit board due to vibration because they cranked the speakers up to the threshold of pain, and the occasional blown 136A. Frankly, I wouldn't want to be in a situation where four L300's were focused six feet from my head loud enough to part my hair. They ran them without the slant plate lens.

    My advise, use the L300's for what they were intended, for the living room, not a forth of July block party. The last thing you want to do is force a 136A or 2231A, or any loud speaker past it's excursion limit. That would be just silly!

    Good luck, H.F.

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    Senior Member ratitifb's Avatar
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    Quote Originally Posted by otenmsa View Post
    How long for can I drive these speakers at very loud levels without ruining anything?
    including your ears or not

    FYI a level of over 100 dBA is loud enough to begin causing permanent damage after just 5 minutes per day!


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    Senior Member martin2395's Avatar
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    This.

    I bet that you would go deaf before you reach 300W's on the L300's (i guess you'd also toast the networks way before reaching 300W)
    But again, we are talking about 300W continuous power, a 300W peak for a short period can't be a problem.

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    Senior Member rdgrimes's Avatar
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    ^^^
    Ditto, I'd like to see anyone tolerate continuous 300W with ANY speaker. 100W maybe.

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    Demag?

    Quote Originally Posted by rdgrimes View Post
    ^^^
    Ditto, I'd like to see anyone tolerate continuous 300W with ANY speaker. 100W maybe.
    Heck. Putting a single ended 300B on a set of horn speakers is enough to part the Red Sea!

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    Quote Originally Posted by rdgrimes View Post
    ^^^
    Ditto, I'd like to see anyone tolerate continuous 300W with ANY speaker. 100W maybe.
    You should ear the jbl 4731x , I am hitting 117db 12 ft away. 100 db is loud ? Maybe for old farts , lol .

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    Administrator Robh3606's Avatar
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    I think this an over exaggerated issue.
    In your setting with multiple boxes and drivers in the dozens yeah it would be. At home definately more noticeable with single driver pairs. It's a fact it happens. Only the K's count the E's would be fine.


    Rob
    "I could be arguing in my spare time"

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    In the Great Alnico / Ferrite Debate, there's a quote on Greg Timbers saying that a peak of current could instantly drop 3dB on a 2231A response and that these drivers were designed for tube amps. He says: "With the advent of big solid state amps, the current levels went up and the problems started to surface."

    This means I could demag the Alnico with only peaks of high power/current?

    Say, listening to a 40W continuously and having dynamic peaks of 200W or maybe 300W on certain passages.

    http://www.audioheritage.org/vbullet...Ferrite-Debate

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    Senior Member Audiobeer's Avatar
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    Quote Originally Posted by otenmsa View Post
    I have read on this forum that the Alnico drivers demagnetize due to large voice coil currents. This means that I could possibly demagnetize the driver if playing too loud.

    However, I haven't found on the topics how much would be loud enough? What are the large currents for these drivers to demagnetize?

    Can I drive a JBL L300 (with 2231A) with a McIntosh MC402 at loud levels? I like to play loud and usually the power meter goes to the 40-400W range.

    How long for can I drive these speakers at very loud levels without ruining anything?

    The only way your gonna hurt an Alnico is dropping it. Driving a pair of L-300s with the Mcintosh MC402 is going to destroy your ears before it has any effect on the magnets of the Alnico.

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