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In Reply to: RE: The energy content of music in the treble is usually pretty low posted by mhardy6647 on February 21, 2017 at 03:05:41
+1. There's more than one way to rate a tweeter. One is the actual power that it will take, the other is the system power that it will be used in. Power density drops by 3dB with each octave increase in crossover frequency, so a tweeter rated at 20w actual may also be rated for 200w system. The only way to know for sure how a specific tweeter rating was arrived at is to contact the manufacturer, but it's a pretty safe bet that a tweeter isn't rated for 20w system power.
that was the first thing i attempted to do, but the email field on their "contact us" page is blank. apparently they don't want to be bothered with pesky questions like this that no-one seems to have the answer for.
i'm quite familiar with the 3dB rules as it relates to both watts and doubling drivers as well as the difference between RMS & continuous power, but none of those rules really have anything to do with the fact that tweeters can be used in systems rated at higher powers than they're rated, again, including those 15w rated compression drivers in no way intended to be used in PA speakers laughably rated 15w.
i wouldn't be so concerned were it not for the fact that ribbon tweeters are notoriously fragile.
> i'm quite familiar with the 3dB rules as it relates to both watts and doubling drivers
I'm not so sure that you do with respect to power density, which drops by 3dB with each octave increase in frequency. Thus the power required at 1kHz is halved at 2kHz, halved again at 4kHz, and so forth. That's why some tweeter ratings are so low. In a typical 100w system a tweeter crossed at 5kHz might only see 5 watts. But since some manufacturers don't specify exactly how their power ratings are arrived at it can be confusing.
no, i'm not familiar with any specific formula that relates to power and frequency, but i always believed that bass requires more power, until i "unlearned it" in some article, possibly about bi-amping that DEMANDED tweeters get the same wattage as woofers assuming the same efficiency.
since then, i've treated THAT as "gospel".
looking at the same issue from a different perspective, i agree that seems bunk as woofers not only have to move a much larger surface area, but also at much greater excursions which clearly requires much more energy where tweeters move tiny amounts of air at imperceptible excursions... the physics behind the math you quote so to speak. (pun intended)
i should have trusted my intuition and NOT the magazine author that polluted my head with bad info. i've seen authors talk idiotic junk before. one, complaining about some issue regarding electrostats, thought it would be "a good idea" to put mids on both sides of a tweeter to improve imaging like an MTM, but the idiot didn't take into account that the only reason MTMs work is because they equally divide the planes of the ears which are on the same horizontal plane & NOT on the same vertical plane as would be needed to time align horizontally.
don't get me started on the popular science EDITOR who couldn't figure out why shower curtains bow inwards against the force of the water. apparently, he never heard of convection. LOL
anyways, thanks for breaking this bad bit of misinformation i got suckered into adopting for so many years even though it sounded wrong. the greater the mass moved and distance covered, the more ergs are needed. DUH! although... higher frequencies must get credited for their "extra reps" in the whole "conservation of energy" thing.
let's see... 40,000 (forwards AND backwards) x .000001mm x .05g = i'm not running the numbers
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