The power of the amplifier which feeds an active (internally amplified) subwoofer by low level connection (phono cable) is not relevant. The output voltage from LFE, Sub-out, Sub or Pre-out does not change with external AVR or amplifier power. It is a very low voltage to an agreed international standard.
An active subwoofer can overdrive itself if fed with a very high level input signal. This could be achieved by turning up the subwoofer's gain in the AVR's menu to maximum then playing films with very heavy and deep bass at very high levels. The driver will probably be damaged by the voicecoil hitting the endstops.
If a very powerful external amplifier drove a subwoofer by high level (speaker level) connections I suppose there might be some danger to the active subwoofer amplifier. But the input section of the subwoofer's own amplifier has a very high impedance. Which suggests the subwoofer would be safely protected from very high input voltages simply by turning the input gain control down.
In the case of this thread the fuse is probably blowing because of an unfortunate fault in the subwoofer's own amplifier.
In such cases one should not proceed to try more and more fuses. One should contact the dealer who sold the item. Or the manufacturer if no dealer is involved.
The item should be unplugged and the family warned not to use it.
One should never use a stronger fuse (with a higher amperage rating) than the manufacturer's own supplied fuse.
The fuse is there to protect the item and the user. If any other fuse is substituted for a weaker fuse (that keeps blowing) then a fire or electrocution is possible.
If a fuse keeps blowing then there is a fault. Which must be attended to and the item not used until the item is professionally repaired. Or replaced.
Opening an item without the permission of the dealer or manufacturer will probably void your guarantee. This simple rule will hopefully protect you or your family from electrocution.
I didnot understand most of your comments, as I am still disgesting the Audio stuff being a newbie. But being comfortable with electronics and computers generally, I did make it out as a fault in some electrical part of Sub, i.e. BASH AMP most likely.
Having said that, I did use MCACC setup on Rcvr to adjust channels, and distances etc. though Sub went thru all that conveniently, only to blow the first fuse when I put some music on it. The 2nd and 3rd fuse, though didnot take that long, blown in less than a second of being switched on. Which confirmed my doubts.
Furthermore, I have spoken to SVS Sales today, who have been kind enough to get my sub replaced with a new one in next 2 days ..... just in time for xmas holidays...
Well hopefully, I will get over this trouble now.
Surprisingly, I remember only one fellow telling me about blowing his fuse, due to some [i cannt remember] reason on his much powerful 12-Plus/2 sub and that was only once. Even Ian himself at SVS Sales has been surprised by this trouble of consistently blowing fuses. According to him, he has never had this trouble ever before with any SVS sub.
Never mind, it will go down as another day, another experience...
And life goes on...