I'm joining late into this love fest, but to the owners of the 15H...why does it matter? You all seem pleased with your sub?
From the outside looking in:
Intuitively, it's a ported 15in sub with a 350W amp...a lower output number at lower frequencies compared to its competition in the same price range shouldn't be a surprise.
Buyers of this sub aren't the 'bang for the buck buyers'. I would think they place more emphasis around functionality, form, warranty, etc. versus pure output.
I guess my point is; I don't think HSU will lose many sales just because it doesn't reach the output number posted by the mfg...