@limomangus - why would the same number of decibels hitting your ears from headphones be any worse than the same number of decibels coming from speakers? The SPL? The speakers in headphones are miniscule compared to those in loudspeakers. I’ve been deafened by speakers in homes and venues, but can’t say the same about headphones.
Just spit-balling, headphones are a very tight & unforgiving acoustic environment; those drivers are firing right into your ear canals. I think certain resonant peaks could get real bad in a hurry, and are not easily nor repeatably measurable, especially since what matters here is your very specific head. Especially dangerous are higher frequencies IMO. A single SPL number (averaged or at a specific frequency) isn’t nearly the whole picture. I just know that for me on average headphones are more fatiguing at the same perceived SPL than speakers (over a large trial number of both). But of course there are exceptions - some speaker setups have been fatiguing to me, and e-stat headphones in particular are a huge relief to my ears, even those with tipped-up frequencies responses that on-paper look like they would be horribly fatiguing (e.g. Stax SR-009). By far by FAR, Grado headphones have been the most fatiguing listening devices on earth in my experience. My right-ear is particularly sensitive to this, and I just can't anymore with Grados.
