Horrible clipping at ~70% amp volume - why?

Discussion in 'Archived Threads 2001-2004' started by Bill Bennett, Jan 4, 2003.

  1. Bill Bennett

    Bill Bennett Auditioning

    Jul 15, 2002
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    I have a Marantz PM4200 amp driving a pair of Tannoy MX3 floorstanders.

    I'm extremely happy with this budget HiFi system, don't get me wrong, but I'm curious: Normally, I have the volume at between 10-30% on the dial at home and the sound fills our small living room very nicely. The one time I've cranked this system up (at a party in a large room), the volume dial reached about 70%, and the distortion on the speakers was pretty obvious and horrendous. I rushed to turn it down, naturally, but it got me thinking.

    Assuming this distortion is what they mean by "clipping", can I ask what this actually implies? Is it that the amp is under-powered for these speakers, or that the speakers are in some other way inappropriate for this amp?

    From the specs for the system:

    recommended amplifier power 10-90W RMS
    continuous power handling 120W RMS
    sensitivity 89dB
    nominal impedance 8 Ohms

    Amp power output at 8 Ohms
    RMS 30W
    DIN 35
  2. John Garcia

    John Garcia Executive Producer

    Jun 24, 1999
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    Yes, it sounds like the amp is not sufficient to drive these speakers at higher levels. While this amp is likely honestly 30x2, that may not be enough for these speakers. I really think you should be considering something closer to 80-100 true wpc.

    My rule of thumb is roughly 50% more power than you need, meaning that at 50% of output, you should not reach distortion. This gives you headroom for dynamic peaks and reduces heat build up, which is much more likely if you frequently drive an amp at or near it's limit (heat will also reduce an amps max output capability). I read a review of that amp, and it was noted that it heated up quite a bit with a pair of floorstanders (I forget which speakers).

    Clipping refers to the "clipping" of the peaks of the sound waves when the amp runs out of power. The incorrect wave forms become distortion in your speakers, and can quickly damage them, particularly the tweeters.

    Speakers do not clip, only amplifiers. Speakers only reproduce what they are fed. The combination of an underpowered amp with a given pair of speakers can create a situation where clipping is likely though.

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