Hey Paul, I've seen the link that you've sent regarding gain of the low frequencies below 300hz in a sealed cavity. This is something that I've been thinking about for a while, why a breaking of seal would result in the large roll off of the low frequencies, or for example, why you smaller speakers can fill a small room but not a large one, losing the low frequencies in a larger or more open space. However, I think there is something to consider as well, and I'm sure that for yourself, given that you have some experience with measurements, you would understand what I'm saying. When you measure IEMs, if the seal isn't right, you get a bass roll off that can be huge, just like what the article says. However, when the seal is right, you're measuring the intended bass response. How I'm not doubting this gain thingy in an enclosed space, I don't perfectly understand it, but say it exists, your typical IEM measurement would pick it up as well. Thus, the frequency response measured would already take into account the bass gain, if you get my drift. It would thus be unreasonable to say that you would get a 60db emphasis in the bass frequencies like the article seems to suggest, because this has already been taken care of in the tuning. Unless you tell me that the IEM measures flat without sealing, then yes I can accept that sealing the IEM is going to give you that monster bass. However, if the IEM is tuned based on the sealed measurements, then there is no worry about an excessive bass response.