Amazon.com: Facmogu 4in Solid Wood Speaker Enclosure, Speaker Cabinet Enclosure for DIY Car or Truck Audio Custom, Speaker Enclosure Unloaded Box with Sound-Absorbing Cotton & Speaker Terminal Cup : Electronics
Dali Phantom Back Can
BX Back Box | Stealth Acoustics
MartinLogan MC6-HT Retrofit Back-Box Create a sealed enclosure for select MartinLogan in-ceiling speakers at Crutchfield
Baffles & Back Boxes For In-Ceiling Speaker Model | AtlasIED
Amazon.com: KEMIMOTO Single 6.5 Inch Speaker Pod, Universal Angled Boxes Enclosure for 6.5" Speakers Compatible with UTVs, RVs, Cars, Boats, Trunks, Trailers - 9.56 Inch Surface Mount : Electronics