The Goal: The client was interested in a wide response bandwidth, warm tonality suitable for a wide genre of music, and a considerable amount of output in his 1993 Honda Civic Hatchback. All this with a pair of DD1508 8″ woofers.
The Design: After performing some analysis of the cabin acoustics and geometry, I arrived at a chambered transmission line hybrid (T-Box) with the woofers firing up, and the back-wave firing off-axis toward the rear passenger side corner of the cabin. Predicted response at the driver side head rest: 29Hz – 75Hz (+/-3dB).
The Build: This was one of my first “Horizontally Screwless” builds. The idea was to bond all the vertical panels without the use of screws or counter-sinks which tend to be unsightly, even if patched with wood filler:
For an improvement in the overall velocity profile, the transmission line terminates at a 1.25″ radius flare. There’s also a horizontal waveguide running along the outer fold of the line to assure more even distribution of pressure in an event that the back-wave is fired against the back slope of the rear passenger side tire well:
I implemented a double-stack along the top of the enclosure so that I could inset the woofers for a flush mount along with some additional styling:
Now for a quick test-fit with some DD1508s that I happened to have on-hand: