AudioControl Spike SPK-8 Dual Box: Sealed 8" Down Fire Enclosure Dual 8" Sealed enclosure

The Spike SPK-8, yes, in the SPK-8S4 (single 4 ohm) version. The baffle is cut to 7.250 in for AudioControl's 8.425 in frame. The 4.29 inch motor clears the cabinet with 2.47 inch to spare. Run two of the same coil so the chambers match. This cabinet is listed for the SPK-8S4 (single 4 ohm) only. AudioControl's SPK-8S2 (single 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 Spike SPK-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.

0.50 cubic feet net per chamber on AudioControl's published figures: the SPK-8S4 (single 4 ohm) reads Qtc 0.852 with resonance at 68.2 Hz and half power at 58.6 Hz. That is AudioControl's own recommended sealed size for this driver, 0.5 cubic feet, between their 0.25 minimum and 0.75 maximum. That is well above maximally flat: a clear lift near resonance and extra midbass, the way AudioControl voices it in this size.

Cabinet gain in a vehicle lifts the bottom end further, so in the car this reads deeper than the anechoic figures.

AudioControl rates the Spike SPK-8 at 350 watts RMS per driver, so target 244 to 350 watts RMS per driver at the final load.

This cabinet is for the Spike SPK-8 SPK-8S4 (single 4 ohm); a matched pair should share a coil. A pair of single 4 ohm drivers lands on 2 ohms in parallel or 8 ohms in series. 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 7.51 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 9.26 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.

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 0.50 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 58.6 Hz per chamber. Above Qtc 0.707 F3 sits below fc, so the response carries a small lift near resonance before it rolls off.

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 0.50 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 are not pre-installed: AudioControl publishes no bolt circle for the SPK-8, so set the driver in its recess, mark its holes, drill and press the inserts. The pair of AudioControl Spike SPK-8 is purchased separately, and the cabinet is cut direct fit to it, not a general purpose 8 inch box.