Performance Optimized Down Fire Sealed Dual 8" Enclosure Ampere Audio AA-2.75 8 · Dual 8" Sealed enclosure

The AA-2.75 8, yes, in the dual 4 ohm version. The baffle is cut to 7.28 in, Ampere's published cutout, under the 8.66 in frame. The 6.42 inch motor clears the cabinet with 0.75 inch to spare. Run two of the same coil so the chambers match. This cabinet is listed for the AA-2.75 8 dual 4 ohm only. Ampere's dual 2 ohm version reads Qtc 0.56 in the same airspace, too damped to sound right sealed, so it is not offered in this enclosure.

Any other 8, no. The airspace is engineered around the AA-2.75 8's own Qts and Vas, and a different woofer that happened to drop into the hole would not see the alignment printed on this page.

0.53 cubic feet net per chamber on Ampere's published figures: the dual 4 ohm reads Qtc 0.617 with resonance at 51.8 Hz and half power at 60.4 Hz. That is a slightly over-damped alignment: a gentle, early rolloff and tight transients rather than a flat top.

The 6.42 inch mounting depth sets the minimum cabinet height here, so the airspace is what the motor allows rather than a free choice.

Ampere rates the AA-2.75 8 at 800 watts RMS per driver, so target 560 to 800 watts RMS per driver at the final load.

This cabinet is for the AA-2.75 8 dual 4 ohm; a matched pair should share a coil. A pair of dual 4 ohm drivers lands on 4 ohms with each woofer's coils in series and the woofers in parallel, or 1 ohm with everything in parallel. Anything under 1 ohm, and many amplifiers at 1 ohm, is outside what the amplifier is built for, so series wiring is the safe default. Confirm your amplifier's minimum stable impedance first.

The cabinet is 7.92 inches tall measured in the down fire position, and that figure excludes the standoffs. The standoffs hold 1.75 inches under the baffle, so plan your space around a finished stack of roughly 9.67 inches.

The footprint is the standard Performance Optimized down fire platform, 30.00 inches wide by 15.00 deep. Height is the only dimension solved to the driver, and here it is the AA-2.75 8's 6.42 inch motor that sets it.

Two drivers sharing one sealed volume load each other: each driver's compression stroke becomes the pressure the other works against, which blurs the alignment either would have alone. A bonded full-height 3/4 inch divider gives each driver its own 0.53 cubic feet and its own polyfill.

It also means a failure in one driver does not unload the other, and the alignment on this page is the alignment in each chamber, not an average across a shared box.

Anechoic F3 is 60.4 Hz per chamber. Below Qtc 0.707 the rolloff is gentle and F3 sits above fc, which is what an over-damped sealed box does.

Those figures exclude cabin gain. In a car the cabin's transfer function adds real output below 50 Hz, so in-vehicle response runs deeper than the numbers above.

No. Polyfill is already installed in both chambers as a light wall lining to control internal reflections, and the quantity is chosen so it does not change the acoustic volume.

Do not add more. Packing a sealed box with fill makes it behave as though it were larger, which walks the alignment away from the 0.53 cubic feet per chamber this cabinet was built to.

No driver. This is an enclosure only. You receive the cabinet finished in plush black carpet, one side-mounted pre-wired terminal cup to both positions, the polyfill lining already in place, the standoffs, and a threaded insert kit with stainless machine screws.

The inserts ship loose on purpose: Ampere prints no bolt circle for the AA-2.75 8, so you set the driver in the recess, mark its holes, drill and press the inserts. The pair of Ampere Audio AA-2.75 8 is purchased separately, and the cabinet is cut direct fit to it, not a general purpose 8 inch box.