Currently working on an 18" flat pack for TD18 to go with a Unity horn:
1. Sealed 90L - designed specifically for Acoustic Elegance TD18H (shown with S3)
This enclosure is designed to allow the box to be pushed into a corner with a horn on top. This design also makes the box more rigid. As used with S2 and my own woofer boxes previously:
When combined with Acoustic Elegance TD18H, this is the ultimate bass box. For a lower cost, it may be used with a Celestion 18" which I can supply at a good price. This is a good bang for buck option.
2. Vented version - 150L with a Celestion 18" woofer
This is a good choice for systems that don't have a subwoofer and don't require extension below 40 Hz.
Other versions available on request. Unless you already have drivers, I recommend a choice between TD18 and Celestion. The Celestion drivers are great bang for buck, but the Acoustic Elegance is the ultimate if you are willing to pay a premium for the best.
Shown below is S2 with my own 60L sealed boxes. These were built manually, but flat packs will all be CNC cut.