Prefab 18 inch sealed boxes?

[Blackout67]

Panels larger than 16" in length I like to add bracing. Doesn't even have to go panel to panel just another piece in the middle of the panel either flat against it or like a T.

If I notice any resonance I'll just go ahead and throw some CLD to help out.

Interesting thing I noticed though; when you go to buy the HT-18s, it links you to a PayPal for Sundown Audio. The shipping confirmation email also game from a Sundown Rep. I know both companies are nearby each other and have collaborated in the past, but I didn't know that Sundown made any subs for them. I thought they just provided the baskets and maybe some soft parts. The SQL12 I bought was they SI's website not an external link to Sundown