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Warning on cd


sadie777

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I picked up this cd at the local Goodwill yesterday,

The Very Best of Erich Kunzel and the Cincinnati Pops

On the back is has a warning: Caution: Digital Sound Effects of high levels with infrasonic frequencies to 5 Hz. Please establish safe playback levels before playing. Excessive playback levels could result in damage to equipment.

Has anyone seen this warning on a cd before? This is the first time I've bought a cd of this type before, so I don't know if this warning is normal or not.

post-58077-0-55500000-1420527722_thumb.j

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Has anyone seen this warning on a cd before? This is the first time I've bought a cd of this type before, so I don't know if this warning is normal or not.
Product liability marking and marketing hype.  Many loudspeakers and subwoofers on the market, particularly those with direct radiating drivers, cannot handle concert-volume playback of low frequencies (where loudspeakers are always the least efficient) even in a small listening room. 
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When you have a bass reflex woofer, they absolutely can respond to subsonics. When they "unload" from the port they can be pushed to maximum travel pretty easily by a 5Hz tone with some power behind it.

 

QUOTE

Another trade-off for this augmentation is that, at frequencies below 'tuning', the port unloads the cone and allows it to move much as if the speaker were not in an enclosure at all. This means the speaker can be driven past safe mechanical limits at frequencies below the tuning frequency with much less power than in an equivalently sized sealed enclosure. For this reason, high-powered systems using a bass reflex design are often protected by a filter that removes signals below a certain frequency. Unfortunately, electrical filtering adds further frequency-dependent group delay. Even if such filtering can be adjusted not to remove musical content, it may interfere with sonic information connected with the size and ambiance of the recording venue, information which often exists in the low bass spectrum.

END QUOTE - source-http://en.wikipedia.org/wiki/Bass_reflex

 

How about horns?  Do speakers with horn loaded bass (Like Khorns, La Scala, Belle) "unload?"  What happens to a 5 Hz tone with these?  Is it just inaudible, but safe, or does it move past safe mechanical limits?

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I think limits are limits for excursion horn or otherwise. The horn would create some mechanical resistance just like a sealed enclosure as compared to a ported one. I have bottomed my THT's out before. Thud thud thud... It's a wonder I didn't have to buy new drivers.  :)

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Yes, horns unload but the Klipsch products have a sealed back volume that controls the cone motion below the horn's cut-off, limiting cone motion. Many years ago Paul told me that a high-pass filter for the Klipschorn at 28 Hz would be correct. He didn't mention slope but my feeling is that 18 dB/octave would be right.

 

My Cornwalls crossover to a subwoofer at 60 Hz and so don't see anything close to infrasonic.

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