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<blockquote data-quote="Art Welter" data-source="post: 215321" data-attributes="member: 52"><p>To expand on Caleb Dueck's reply to your duplicate thread, neither of the speakers offered to you will be sufficient for "loud" (110dB peak) music at more than a few meters.</p><p></p><p>An 8 ohm consumer speaker rated for 100 watts (28.3volts into 8 ohms) may be burned with as little as 3.125 watts (5 volts into 8 ohms), as I found with one of my 8 ohm Tannoy PBM 6.5 near field monitors.</p><p>The Tannoy PBM 6.5 speakers have similar sensitivity and power specifications to the Niles OS 7.3 speakers you burnt already and the Stylus 470 (even less rated power) that you are considering.</p><p></p><p>So how can a “100 watt” speaker that I used for over 20 years powered with a 200 watt amplifier be blown by 3 watts?</p><p></p><p>The difference between peak and average power, and the way speakers and amplifiers are rated provide most of the explanation.</p><p></p><p>Consumer speakers like the above that don’t specify how the power rating is done may be rated for peak power using a source with similar crest factor as music.</p><p></p><p>More professional speaker power ratings like the AES2-1984 use average, or RMS (Root Mean Squared) power with a 6dB crest factor for testing. A speaker with a 100 watt nominal AES rating should sustain 400 watt peaks for two hours.</p><p></p><p>The peak to average power ratio, or crest factor in dB is the difference between the RMS value and the peak amplitude of the signal.</p><p></p><p>Some heavily compressed music (like Metallica’s “Death Magnetic” album..) may have as little as 6dB crest factor, the same as used to test professional speakers.</p><p></p><p>A 6 dB crest factor is power ratio of 4. An amplifier producing 100 watt peaks (no clipping) with a 6 dB crest factor would average 25 watts, 100/4 =25.</p><p></p><p>With a crest factor to 12dB, typical of pink noise or less compressed music, the power ratio is x16, 100/16 = 6.25 watts average.</p><p></p><p>Dropping to the 15 dB crest factor of “normal” music, a speaker could be rated for 100 (peak) watts while sustaining just 3.125 watts on average.</p><p> </p><p>One side of a Hafler DH-200 amp (200w@8ohms) driving my Tannoy PBM 6.5 speaker had a little DC voltage on one channel that slowly grew from a small fraction of a volt to 5 volts over the course of 20 years.</p><p></p><p>5 volts into 8 ohms impedance is 3.125 watts, the “100watt 8ohm” speaker should have handled it, but as the woofer’s DC resistance was near 4 ohms, power delivered was double, 6 watts was enough to cause the voice coil to burn, as the DC held the voice coil in a fixed position, allowing no air cooling as the speaker sat powered, but idle.</p><p></p><p>Then there is the issue of “power compression”, but you can look that up easily..</p><p></p><p>Art</p></blockquote><p></p>
[QUOTE="Art Welter, post: 215321, member: 52"] To expand on Caleb Dueck's reply to your duplicate thread, neither of the speakers offered to you will be sufficient for "loud" (110dB peak) music at more than a few meters. An 8 ohm consumer speaker rated for 100 watts (28.3volts into 8 ohms) may be burned with as little as 3.125 watts (5 volts into 8 ohms), as I found with one of my 8 ohm Tannoy PBM 6.5 near field monitors. The Tannoy PBM 6.5 speakers have similar sensitivity and power specifications to the Niles OS 7.3 speakers you burnt already and the Stylus 470 (even less rated power) that you are considering. So how can a “100 watt” speaker that I used for over 20 years powered with a 200 watt amplifier be blown by 3 watts? The difference between peak and average power, and the way speakers and amplifiers are rated provide most of the explanation. Consumer speakers like the above that don’t specify how the power rating is done may be rated for peak power using a source with similar crest factor as music. More professional speaker power ratings like the AES2-1984 use average, or RMS (Root Mean Squared) power with a 6dB crest factor for testing. A speaker with a 100 watt nominal AES rating should sustain 400 watt peaks for two hours. The peak to average power ratio, or crest factor in dB is the difference between the RMS value and the peak amplitude of the signal. Some heavily compressed music (like Metallica’s “Death Magnetic” album..) may have as little as 6dB crest factor, the same as used to test professional speakers. A 6 dB crest factor is power ratio of 4. An amplifier producing 100 watt peaks (no clipping) with a 6 dB crest factor would average 25 watts, 100/4 =25. With a crest factor to 12dB, typical of pink noise or less compressed music, the power ratio is x16, 100/16 = 6.25 watts average. Dropping to the 15 dB crest factor of “normal” music, a speaker could be rated for 100 (peak) watts while sustaining just 3.125 watts on average. One side of a Hafler DH-200 amp (200w@8ohms) driving my Tannoy PBM 6.5 speaker had a little DC voltage on one channel that slowly grew from a small fraction of a volt to 5 volts over the course of 20 years. 5 volts into 8 ohms impedance is 3.125 watts, the “100watt 8ohm” speaker should have handled it, but as the woofer’s DC resistance was near 4 ohms, power delivered was double, 6 watts was enough to cause the voice coil to burn, as the DC held the voice coil in a fixed position, allowing no air cooling as the speaker sat powered, but idle. Then there is the issue of “power compression”, but you can look that up easily.. Art [/QUOTE]
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