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Message: [QUOTE="Queen, post: 90508, member: 27"] Beyerdynamic rates the DT 275 PRO at up to 22 dBA of passive noise isolation, a number that reads like a comfort feature and works as a safety one. A dBA rating describes [B]the amount of room noise a sealed cup keeps out[/B] before the sound reaches your eardrum. The A weighting means the measurement gets filtered to match how human hearing responds across frequencies, so it leans on the mids and highs where your ears are most sensitive. One averaged figure, standing in for a curve. Take a stage running at 100 dBA. Strip 22 dBA off that and the room arrives at your ear near 78 dBA, quiet enough that you can hear a click track at a sane level instead of fighting the wash. That is the whole case for [B][URL='https://goldmidi.com/community/threads/beyerdynamic-adds-dt-275-pro-for-loud-set-monitoring.75919/']closed-back headphones aimed at loud sets[/URL][/B], and it holds up. [HEADING=2]Quieter monitoring buys back your exposure time[/HEADING] NIOSH sets its recommended exposure limit at 85 dBA averaged over an eight-hour shift. Above that, the clock runs on a 3 dB exchange rate, so every 3 dB increase cuts the safe duration in half. Run the arithmetic, and it gets uncomfortable fast. At 88 dBA you have four hours. At 91 you have two, at 94 you have one, and by 97 dBA you are down to thirty minutes. Now think about what happens with weak isolation on a loud gig. The room hits your ear at 92 dBA, so you push the cue mix past that to hear anything useful, and your working level lands somewhere near 100. Fifteen minutes of safe exposure, on a six-hour call. Nothing in the hardware stops you from getting there. beyerdynamic quotes a nominal sound pressure level of 105 dB for these, and most monitoring headphones sit in similar territory. The driver will hand you a level that costs you hearing inside of fifteen minutes, and it will do it cleanly, with no distortion to warn you off. Isolation breaks that loop. When the room is already down at 78, a cue mix at 82 or 84 is plenty loud and sits well under the limit for a full day. You are not turning things down out of discipline. You are turning them down because you can finally hear. [HEADING=2]Your seal decides how much of that number survives[/HEADING] Passive attenuation is not flat across the spectrum. Cups and pads block high frequencies well, because short wavelengths are easy to stop with a bit of mass and a tight seal. Low frequencies are a different problem. Bass energy is long, and it moves through a pad, a temple arm, or your skull without much trouble. So a kick drum three meters away still reaches you clearly, even in headphones rated at 22 dBA. Cymbals and stage chatter will not. That mismatch is normal, and it is worth knowing before you blame the headphones for a bass note you cannot separate from the room. The seal is where the rated figure lives or dies. Glasses arms break it. Thick hair breaks it. Pads that have compressed over two years of gigs break it slowly enough that you never notice the day it stopped working, and the low end goes first. Which is why the words "up to" are doing real work in that 22 dBA claim. Lab attenuation figures come from a controlled fit on a measurement head, not from your ears at hour five of a wedding reception with sweat under the pads. Treat the number as a ceiling, not a promise. Test your own fit by pressing the cups gently against your head with both hands while the room is loud. If the outside noise drops noticeably when you do that, your everyday seal is leaking, and your real isolation sits well below the spec. On a set with replaceable pads, that is a five-minute fix, and it restores more attenuation than any tweak you can make to the cue mix. [/QUOTE]

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