Yes it was. The Sub was tuned to the Box.
I found out today that Alpine don't want to replace the sub because it's now out of warranty. I've told them straight. I don't expect the Subwoofer to blow conveniently after warranty has expired.
Exact same thing has happened to me and the subwoofer has been underpowered. I emailed Alpine directly. Not even been used for 2 years and this has happened. I was powering mine using the Alpine X-A90V 5 Channel Amp.