Never a thump from my 350 either.

My EP500s do not thump when I turn them off. My EP800s do thump when I turn them off. I did not have a problem where it sounded like air was going through them when they were not playing music though.

Quick questions though... Has anyone else noticed the lack of the trim dial (flat, half full) and more importantly the fuse holders? Where are the fuses for the EP800, on the inside?

Ahh, I didn't even notice the lack of trim. The fuses pull out below the power plug.

Thanks for the info CV! I guess the voltage regulator houses the fuses. On the EP500 and EP600 there were 4 additional round plugs (3 black, 1 gray) below the trim dial which I assumed to be fuse holders. They are not present on the EP800. Do you know what they were?

Yeah, they were fuse holders. The first amp I had for my EP600 had the same location for the fuses as the EP800s, but I had to get my amp replaced at one point, and the new one had them in those screw plugs. I remember being confused when I was troubleshooting as the manual showed those screw plugs, but I didn't have them.

Been playing guitar most of my life. Just about every amp I've ever heard has some sound when NOTHING is plug into it. In other words no signal feeding it. You state your system was off. The only thing you are getting from your system is a low level signal like a guitar in a guitar amp or even a mic into a PA System. Sutting it off is like unplugging a mic or guitar. Your amplifier is still on in the sub. The more power the amp is the more that sound of "air".
My guitar amp is tubes and I don't notice a thump. My son's bass amp and my PA ampsa are all solid state. They all thump when they are turned off. I've heard some amps thump when they turn on. The more power the amp the bigger the thump. I don't use the bass amp, but when I pwoer down my PA I try to remember to turn down the attenuators to lower or eliminate the thump.

After your sub has been off a few minutes, turn it back on while the system is still off. I would bet that you heard a thump when turning it on also. Probably wouldn't hear it under normal operation because the system is up and running when the sub usually comes on. I wouldn't think it's a big deal especially since these subs don't seem to be design to be turning the attenuators on the sub amps up and down upon turning on and off. Best thing is to of course call Axiom Tech Support.

I have NO experience with HT subs and amps!


PS I would also bet that if you turn up the volume knob while the system if off (and the sub amp on) that you will hear that "air" sond increase in volume. I would also bet if you turned down the volume before shutting off the sub amp (also while the system is off) that you would not hear any thump.