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Junior Varsity
Compact Power Subs for Stick mains
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<blockquote data-quote="David Gunness" data-source="post: 121993" data-attributes="member: 1032"><p>Re: Compact Power Subs for Stick mains</p><p></p><p>OK, here we go. Once more into the breach. The reason I hate this is that in the process of explaining how our industry does specs, it appears that I am justifying practices that I actually don't agree with. </p><p></p><p>One of the reasons I don't like peak SPL specs is that "SPL", at least in textbooks, is defined as the RMS sound pressure (referenced to 2x10-5 pascals). So theoretically, there is no such thing as "peak SPL". OK, maybe that's too pedantic: we could interpret it as "peak sound pressure, expressed in units of SPL". Let's go with that.</p><p></p><p>The point is that "Peak SPL" as it is treated in the professional loudspeaker industry, is peak pressure, not "highest reading of an SPL meter" (SPL meters only measure RMS; even if there is a peak hold function, it is the "highest rms reading observed", and that includes the selected averaging time). Anyway, peak pressure is calculated using the peak voltage of the amplifier. With non-powered systems, the assumption is that a user will supply an amplifier with twice the power rating of the loudspeaker, and that the peak voltage of the amplifier is 3 dB higher than that, because amplifiers are rated with sine waves. Hence, the peak pressure <em>should </em>be 6 dB higher than the maximum continuous SPL.</p><p></p><p>Keep in mind that maximum continuous SPL is a survival rating, not a useability rating. Of course what would be more useful is "maximum useable SPL", but that would be signal dependent and would have to be subjectively determined. So we're stuck with a calculated value that serves only as a point of comparison: "This one's red line is 2 dB higher than this one's red line."</p><p></p><p>As for the TS215ac, here is the math (with one more significant figure than the whole numbers on the spec sheet):</p><p>Equalized Sensitivity: 99.2 dB</p><p>Maximum Peak Voltage of the Amplifiers: 150 V</p><p>"Peak Power" into 2 ohms (actually two channels driving 4 ohms each): 11,250 W</p><p>Peak Power, expressed in decibels: 40.5 dB</p><p>99.2 dB + 40.5 dB = 139.7 dB, which rounds to 140 dB</p><p></p><p>Dave</p></blockquote><p></p>
[QUOTE="David Gunness, post: 121993, member: 1032"] Re: Compact Power Subs for Stick mains OK, here we go. Once more into the breach. The reason I hate this is that in the process of explaining how our industry does specs, it appears that I am justifying practices that I actually don't agree with. One of the reasons I don't like peak SPL specs is that "SPL", at least in textbooks, is defined as the RMS sound pressure (referenced to 2x10-5 pascals). So theoretically, there is no such thing as "peak SPL". OK, maybe that's too pedantic: we could interpret it as "peak sound pressure, expressed in units of SPL". Let's go with that. The point is that "Peak SPL" as it is treated in the professional loudspeaker industry, is peak pressure, not "highest reading of an SPL meter" (SPL meters only measure RMS; even if there is a peak hold function, it is the "highest rms reading observed", and that includes the selected averaging time). Anyway, peak pressure is calculated using the peak voltage of the amplifier. With non-powered systems, the assumption is that a user will supply an amplifier with twice the power rating of the loudspeaker, and that the peak voltage of the amplifier is 3 dB higher than that, because amplifiers are rated with sine waves. Hence, the peak pressure [I]should [/I]be 6 dB higher than the maximum continuous SPL. Keep in mind that maximum continuous SPL is a survival rating, not a useability rating. Of course what would be more useful is "maximum useable SPL", but that would be signal dependent and would have to be subjectively determined. So we're stuck with a calculated value that serves only as a point of comparison: "This one's red line is 2 dB higher than this one's red line." As for the TS215ac, here is the math (with one more significant figure than the whole numbers on the spec sheet): Equalized Sensitivity: 99.2 dB Maximum Peak Voltage of the Amplifiers: 150 V "Peak Power" into 2 ohms (actually two channels driving 4 ohms each): 11,250 W Peak Power, expressed in decibels: 40.5 dB 99.2 dB + 40.5 dB = 139.7 dB, which rounds to 140 dB Dave [/QUOTE]
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