Subwoofer w/ most SPL's For Music Only System

Of the subs you mention, only the Velodyne HGS 15 will be of excellent musical quality (around 1% THD). The other two are more for movies, the Earthquake has a passive radiator and is almost certain to have 20% harmonic distortion at the lowest frequencies....although it will probably go very loud at LF.

The only concern I might have with the Velodyne is thermal compression => it uses an elaborate voice coil system to get extreme linear extension....this is fine for an occasional movie earthquake but it might heat up on music with continuous LF demands...(voice coil heat needs nearby mass to dissipate otherwise resistance increases)

Since thermal compression and dynamic behaviour is very speaker/designer dependent...you really should consider a sub from the same people that make your main speakers ( the match at various SPL levels is likely to be much better if you stick to the same manufacturer - it is no good having an amazing sub if your speakers mid range compresses at high volumes levels and vice-versa is ture too - mismatch will just lead to frustration to get it to sound right as you change SPL level).

I auditioned many subs, but only one of the three you mentioned, Sunfire. I ended up with an ACI Titan - the most musical sub of all of the ones I heard. And it has plenty of power. I have mine turned down so low, at times I wonder why I even got one. But when I turn it off it becomes immediately obvious how well it does its job. Superb.

Thanks Tvad: I tried the ACI Titan II LE. And it is high quality and seamless. The only drawback for me was that in my system and room it was too light in the low end.

I second the Bag End comment from Bob.

I have tried all the subs you mentioned and of the 3 I would probably go HGS-15 1st, Earthquake 2nd and the Sunfire Sig last.

The Earthquake 15 is an excellent sub though for music as well and hits harder than any of the above mentioned subs. The Velo is more musical though.

The Bag End goes lower than all of them though as confirmed by my Velodyne SMS-1 EQ and is the best music only sub of the bunch.

The Bag End does not hit as hard as the Earthquake though. The bass from the Earthquake can get scary if you want it to and with a EQ like the Velodyne SMS-1 you can tame it for music as well. I have heard 2 other systems with Supernova 15's and no eq. Both sounded very impressive with music so I guess an EQ is not mandatory. Most people think that since it has a passive radiator and can hit crazy levels of 117+ db at 35 hz that it can't sound good for music but that is just not the case.

I hope this helps some.

Good luck.