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Questions about maximum output and loudness range

ghostwriter

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Feb 21, 2021
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I've been looking for some speakers and one of the metrics that I've been keeping an eye on is the maximum output so that I can have an idea of how loud I'll be able to go at certain distances. I'd like to know if my assumptions are correct or if I'm misunderstanding how the dynamic range would relate to the max output of a speaker.

This is my current understanding of maximum output and loudness range:
  1. Maximum output is measured at a distance of 1 meter
  2. Dialogue in movies is calibrated to an average of -27dBFS
  3. Sound level reduction is 6dB for every doubling of distance
Putting those together, I can find the expected maximum usable output at a different distances.

For example:
KEF LS50 Meta has a maximum output of 106dB. Assuming I want to make use of the full loudness range of movies, I would need to calibrate the speaker's sound level to be 27dB less than the maximum output which is 106dB - 27dB = 79dB at 1 meter. This will allow the loudest sounds in movies to reach the maximum rated output level for the speaker. Given 79dB at 1 meter, I can calculate the expected average dialogue sound level for other listening distances:

Code:
Maximum usable sound level for full loudness range
| meters | decibels | feet |
| 1      | 79       | 3.28 |
| 2      | 73       | 6.56 |
| 3      | 67       | 9.84 |

These seem a bit low for maximum usable levels at those listening distances. The current top three speakers sorted by preference score are at or under 110dB max output, which isn't much of an improvement. Are these speakers unsuitable for listening to movies at the full loudness range? Assuming I did go higher than the calculated maximum usable sound level, wouldn't I have clipping, distortion, or damage during parts of a movie where the loudness reaches peaks?
 
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RayDunzl

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Sound level reduction is 6dB for every doubling of distance

The direct sound may fall off at that rate, but reflections from the walls/ceiling/floor will reduce the rate of perceived (and measured) SPL loss.

You can also add 3 to 6 decibels for two speakers (stereo) instead of one (usually what produced the published measurements) at the listening position.
 
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ghostwriter

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Thanks for the replies, I ended up using my UMIK-1 to measure SPLs for my pair of JBL LSR 305s to figure out my typical listening levels.

You were right about the additional decibels for a pair of speakers. I didn't measure how many dBs were added by having them near a wall but when I measured single versus the pair, SPLs increased by about 3dBs.

As for my listening levels, "comfortably loud" was around 60-65dBA for me when listening to music and the same for movie dialogue, with loud parts of a movie reaching mid 70s and explosions reaching around 80dBA. So it looks like I really overestimated how high I'd need to go with my SPLs.

From what I've seen, many studio monitor manufacturers measure max output per pair, not single, so the extra 3dB is already factored in, but assuming I have them near a wall, I'd probably be fine with any speakers that have a max output of 95dBA, which should be enough for 27dB of headroom at my listening levels and distance without reaching max output for sounds that are near 0dBFS.
 
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