Hi, I've been gigging with a Hartke HA3500 Head and 410XL cab for several years now and have been very happy with the sound. The system is not new, but has been used yet lovingly cared for (I bought it 2nd hand). Recently I have noticed a lack of bass depth in the projected sound and am working through the rig to see if anything is amiss during our gig downtime (volume is fine). I recently had a loud "crackling" during played notes at a gig which was stopped by turning off the amp, removing the volume pedal (my only pedal) and carrying on with a single lead from bass to amp head. I assumed muck in the volume pedal potentiometer or a dodgy lead. I've cleaned the former and replaced the latter - no more crackling, but I think I am hearing less bass depth in the projected sound since the episode. I've started by checking the cab first as the amp looks to be functioning correctly (visually anyway). All four speaker cones move in the same direction with the 9v battery test. One speaker seems to move slightly more than the others. I cannot see any visual tears on the aluminium cones. When gently pushed in and out the cones are all free to move. The speaker that has more cone movement on the battery test seems slightly easier to push in then the others than the others. I removed the above single speaker and tested it's DC resistance (whilst still connected to the cab internal wiring) and it was 4.8 ohms. This seems lower than I would expect, but I'm not sure if the fact it was still connected to it's internal wiring makes a difference? The DC resistance of the whole cab through the cab input jack socket is 6.8 ohms - which seems about right as DC resistance on an 8 ohm speaker seems to be about 2 ohms below impedance as a general rule. The cab impedance is rated at 8 Ohms and I understand it contains 4 x 8 ohm speakers connected in series/parallel to achieve this. Are my DC resistance measurements around what you would expect for this cab please? Is it normal for one speaker in a cab of identical speakers to have more cone movement / easier cone movement? Many thanks - I don't think there's anything wrong with the cab now but thought I'd ask people with more experience than myself!