Case Study -Amplifier matching!?

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Thu Mar 03, 2016 1:57 pm

  • Hello!
    I'd like to hear what's your opinion on the Amp-Speaker combination I encounter at a certain facilities the other day. The system is for a small lecture/recital hall, which was installed by a local A/V contractor 10 years ago. I am trying to solve the issue, which is, we noticed that very slight but annoying cracking/vibration kind of distortion at certain notes in low-mid frequencies, when we play gentle piano music through the speaker. I assume that LF cone driver went bad in 10 years.

    Speaker EAW MK2394
    -Accelerated Life Test* 600W @ 8Ω *defined in the spec sheet, as Maximum test input voltage applied with an EIA-426B defined spectrum:
    -Calculated Axial Output Limit Avg:123dB, Peak 129dB

    Amplifier QSC CX302
    -200W 8Ω (per channel)

    I am sure the system is not intended for like a rock band concert. So I assume there are not so many occasions to push amps and speakers so hard. But I think the capability of Amplifier is too low if one wants to pull the maximum sound out of the EAW speaker. That attempt would cause the speaker failure due to the distortion from the amps, right?
    I know there is a great resource, Amplifier Selector on your website! But I'd like to hear more knowledgable insight!

    Thank you again for your attention!

    Hidenori Nakajo
    HJN Design
    Posts: 1
    Joined: Thu Mar 03, 2016 12:59 pm

Thu Mar 03, 2016 3:31 pm

  • Hi Hidenori

    The amplifier might or might not be inadequate for the application. The surest way to find out is to determine if it clips during the highest-level usage that the system will be put through. If it doesn't clip, than the amplifier still has headroom available, and additional power is not needed.

    The CX302 is an extremely low-distortion amplifier. It will not produce audible distortion unless it is pushed into clipping with the clip limiter disengaged. Not only is the distortion produced by the amplifier so low that it is negligible, but distortion will not damage the loudspeaker at all; the loudspeaker simply cannot distinguish between clean signal and distorted signal. The two ways in which a loudspeaker can be damaged in use are 1) excessive power (i.e., thermal damage) and 2) overexcursion (i.e., mechanical damage, typically from "bottoming out" due to excessive low-frequency energy).

    An installed loudspeaker that has been in place for many years might develop other faults because of things like dust accumulation, material deterioration, general fatigue, etc.
    Bob Lee
    Technical Communications Developer
    QSC, LLC
    Fellow, Audio Engineering Society
    "If it sounds good, it is good." —Duke Ellington
    User avatar
    Bob Lee
    QSC Audio Products
    Posts: 2518
    Joined: Thu Mar 06, 2003 2:01 am
    Location: Costa Mesa, California

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