As I commented recently in Guy's thread involving his EP500, the reason for deleting the Trim control(but still showing it on the site)is unclear, since in my own use(older EP500)I've found it to be quite useful in balancing the mid-bass with the amount of room gain which varies with room size(smaller rooms have more gain at very low bass frequencies).
The subsonic filter which is now switchable in or out(previously I understand that it was fixed at about 18Hz)has no apparent connection with the disappearance of the Trim control. They affect different frequencies. The subsonic filter sharply cuts response below about 18Hz to protect against very low frequency rumble causing a problem. Except in the rare case that it does cause a problem the filter should be left off. The Trim control boosted response in the mid-bass above about 35Hz by variable amounts to balance variable amounts of room gain at lower bass frequencies.
As to the increased volume control setting on the EP500 which is now apparently required as compared with the previous version, this can result from two possible changes: 1. the gain of the sub amplifier has been reduced; 2. more likely the volume control has been modified so that it lets less of the incoming voltage in at its lower rotation, and so a higher setting is necessary to let the same amount of voltage into the amplifier to be subjected to its gain. Whatever the reason might be, if adequate volume can be achieved with less than the max setting it shouldn't be a cause for concern.
