11-Aug-2019, 10:50
David - Thanks for the link, both interesting and potentially useful.
I thought it would be fun, and perhaps informative, to put whatever information we can glean from the video linked in the OP into the calculator, to see what number come out.
Some factors we know quite well, per the Stereophile measurements posted earlier in the thread, the Harbeth's have a sensitivity of about 84.5dB/1w/m. From the video, it is also clear that the speakers are within 4 feet of the back wall, but not within 24 inches of the corners of the room. It is also clear that there are two speakers. This much is good data. Of course, we also know that the amps were peaking at over 750w, and regularly running at over 500w.
The listening distance is a trickier one. To me it looks like they are listening from about 12 to 15 feet, but later in the video they move to within about 2 feet of one speaker, so listening distance clearly varies. Another unknown figure is what the SPL's are in the room. Back in post #63 I speculated, or perhaps guesstimated, a figure of 90dB with 95dB peaks, to me it is just not credible that it could be any louder than this if three guys could happily approach to within 2 feet of one speaker.
Putting these numbers into the calculator gives these results:
Assuming 84.5 efficiency, 750w, 12 feet distance, within 4 feet of wall, not in corner. Putting these numbers in the SPL calculator gives a result of 108dB. To me, this cannot be accurate. If the SPL was 108dB, then it would not be comfortable in the room, you would not hear the attendees voices over the music, and for sure nobody would move to within one or two feet of the speaker.
So lets do the calculation backwards, how much power would you need to achieve the 95dB peak I estimated earlier? According to the calculator, 40 watts. 40 watts is a full 710w less than the amps in the video were displaying.
So there are clearly other factors involved here. Earlier posts covered the power required to produce powerful bass heavy music, and the whole system of music production is complex and dynamic. I think these calculators are a useful guide, but there is a more complex picture to consider.
I thought it would be fun, and perhaps informative, to put whatever information we can glean from the video linked in the OP into the calculator, to see what number come out.
Some factors we know quite well, per the Stereophile measurements posted earlier in the thread, the Harbeth's have a sensitivity of about 84.5dB/1w/m. From the video, it is also clear that the speakers are within 4 feet of the back wall, but not within 24 inches of the corners of the room. It is also clear that there are two speakers. This much is good data. Of course, we also know that the amps were peaking at over 750w, and regularly running at over 500w.
The listening distance is a trickier one. To me it looks like they are listening from about 12 to 15 feet, but later in the video they move to within about 2 feet of one speaker, so listening distance clearly varies. Another unknown figure is what the SPL's are in the room. Back in post #63 I speculated, or perhaps guesstimated, a figure of 90dB with 95dB peaks, to me it is just not credible that it could be any louder than this if three guys could happily approach to within 2 feet of one speaker.
Putting these numbers into the calculator gives these results:
Assuming 84.5 efficiency, 750w, 12 feet distance, within 4 feet of wall, not in corner. Putting these numbers in the SPL calculator gives a result of 108dB. To me, this cannot be accurate. If the SPL was 108dB, then it would not be comfortable in the room, you would not hear the attendees voices over the music, and for sure nobody would move to within one or two feet of the speaker.
So lets do the calculation backwards, how much power would you need to achieve the 95dB peak I estimated earlier? According to the calculator, 40 watts. 40 watts is a full 710w less than the amps in the video were displaying.
So there are clearly other factors involved here. Earlier posts covered the power required to produce powerful bass heavy music, and the whole system of music production is complex and dynamic. I think these calculators are a useful guide, but there is a more complex picture to consider.
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