In a recent thread someone talked about measuring SPL levels on a Komet Constellation at the grillcloth. I'm not inclined to doubt the measurements (I've never heard a Connie, but my AC30 TBX could get painfully loud), but it got me thinking about charts you see of different loudness levels, and why guitar amps SEEM to be louder than some of the sound sources in those charts. My questions are: 1. How loud can guitars amps get? 2 How loud do guitar amps seem to you, when compared to other sound sources? AND 3. Is there something else (Fletcher-Munson or anything else frequency dependent?) that makes guitar amps seem louder than other sound sources? Here's a typical chart of sounds and their relative loudness levels: http://www.sfu.ca/sonic-studio/handbook/Decibel.html Threshold of hearing - 0 dB Rustling leaves - 20 dB Quiet whisper (3 feet) - 30 dB Quiet home - 40 dB Quiet street - 50 dB Normal conversation - 60 dB Inside car - 70 dB Loud singing (3 feet) - 75 dB Automobile (25 feet) - 80 dB Motorcycle (30 feet) - 88 dB Foodblender (3 feet) - 90 dB Subway (inside) - 94 dB Diesel truck (30 feet) - 100 dB Power mower (3 feet) - 107 dB Pneumatic riveter (3 feet) - 115 dB Chainsaw (3 feet) - 117 dB Amplified Rock and Roll (6 feet) - 120 dB Jet plane (100 feet) - 130 dB To measure just how loud a guitar amp can get, I did this calculation: I'm using the Connie because it's a 4xEL84 amp, an amp type that hopefully most of us have had access to (feel free to comment with specs of any other amp type if you feel it helps). Since Komet measures the Connie at 33 watts before clipping, here's what SPL levels should be possible clean through 100 dB sensitivity speakers (that includes Celestion Blues, G12H 70th Anniversary and Heritage and Vintage 30): For a 100 dB sensitivity speaker, the loudness levels at 1 foot would be to: dB - Watts required 100 - 1 103 - 2 106 - 4 109 - 8 112 - 16 115 - 32 118 - 64 121 - 128 124 - 256 127 - 512 130 - 1024 Or that's why you see loudness levels written roughly on a 10x scale for every 10 dB increase in loudness: db - Watts required 100 - 1 110 - 10 120 - 100 130 - 1000 So by my calculations, the answer to question 1 is: It would seem that a 32 watt amp clean should be able to create 115 dB at 1' distance using 100 dB sensitivity speakers. Since doubling the distance from a source drops the level by 6 dB (just like when you double the amplitude of a sound you increase it by 6 dB), moving away from speaker any distance would drop those levels substantially. Since a Connie at max power (clean) at 8 feet with 100 dB speakers should be about 33 watts (I'll substitute 32, just because the 32 watts is found in the chart above): Here's the loudness levels that should be found as you move away from the speaker Feet - dB 1 - 115 2 - 109 4 - 103 8 - 97 16 - 93 For question 2: Does a Connie (or assuming other 4xEL84 amps) at max clean power at 8 feet away with a 100 dB speaker sound like 97 dB? Remember, this is halfway between: Subway (inside) - 94 dB Diesel truck (30 feet) - 100 dB I think an AC30 with Blues at 8 feet away sounds louder than that clean. What do you think? For question 3: Are my calculations wrong? If it does seem louder, what is causing it? (Fletcher-Munson, maybe?) Are reflections adding to the perceived loudness? What's going on? Am I going deaf?