AudioControl Spike SPK-8 Box: Ported 8" Down Fire Enclosure Single 8" Ported enclosure

Sealed, the SPK-8 is listed in our sealed wedge at 0.50 cubic feet, Qtc 0.85, half power 59 Hz. Vented, the same driver reaches 32.1 Hz. AudioControl's own vented design for this driver is 0.9 cubic feet net tuned to 40 Hz; this cabinet is 1.04 cubic feet at 37.5 Hz through an 18.8 square inch port, sized against the driver's excursion and port speed at full power. The port runs 18.0 m/s in the channel and 15.3 at the mouth at the 350 W design power, and the cone peaks at 7.6 of its 8.5 mm. Passband ripple is 3.3 dB and the in-car spread from 25 to 60 Hz 11.5 dB. The SPK-8S4 (single 4 ohm) was run through the same cabinet: F3 32.4 Hz, passband ripple 2.1 dB, 7.1 of its 8.5 mm at 350 W. Tuning is chosen for in-car response rather than for an anechoic curve: a vehicle adds roughly 12 dB per octave below about 45 Hz, so a box tuned very low reinforces a region the cabin is already reinforcing and leaves 40 to 60 Hz thin. In this cabinet that lands at 11.5 dB of in-car spread across 25 to 60 Hz, which is where kick and bass fundamentals live.

No, and on this build in particular do not add any. Every sealed Proline X enclosure ships with polyfill pre-installed; a ported one must not, because damping material changes the effective volume the port is tuned against. The port on this cabinet is cut to 27.39 inches of centreline path for 37.5 Hz. Stuff it and you move the tuning without shortening the port, which gives you a mistuned box rather than a bigger-sounding one. The 3.30 dB passband you are paying for depends on it staying dry.

Yes, at 30 Hz, 24 dB per octave. Below tuning a vented box stops loading the cone and excursion runs away toward DC. With the filter in place this cabinet puts the AudioControl Spike SPK-8 at 90 percent of its usable travel at full rated power; without it there is no meaningful number to quote, because the excursion curve does not converge. On a sealed build a subsonic filter is an improvement. Here it is required equipment.

AudioControl rate the Spike SPK-8 at 350 W RMS and that is the thermal ceiling. The figures on the Performance Graphs tab are a different quantity: they are mechanical limits, the power at which the cone reaches the end of its linear travel in this specific cabinet. Here the cone sits at 90 percent of usable travel at the driver's own rating, so heat is what stops you, not travel. Final wired impedance and amplifier output are separate questions again.

Not one we can show you. We do not build a sealed enclosure for the AudioControl Spike SPK-8 and AudioControl publish no sealed volume for it, so the Performance Graphs tab carries no ported-versus-sealed chart: the only sealed box left to plot would be this cabinet stuffed and sealed, which nobody would build, and a comparison against it would tell you nothing you could buy. What a vented box gives up is the region below tuning, where the cone unloads and the 30 Hz subsonic filter takes over; around 37.5 Hz the vent carries the load and cone travel drops to its minimum, which no sealed alignment can do.

It is a slot port formed by one folded wall: a leg down the long side of the cabinet past the woofer ring, one faceted 90 degree bend, and a leg across the end opening through a chamfered corner. On this cabinet that is 27.39 inches of centreline path and 18.8 square inches of channel, exiting a 22.1 square inch mouth. Air leaves at 15.3 metres per second at tuning against a 17.0 threshold, and the channel runs at 43 percent of its turbulence limit. One wall and one bend rather than a serpentine's three means less wall area inside the box, fewer joints to leak, and one place for flow to separate instead of three.

V-groove and dado joinery in 0.75 inch Langboard Elite MDF with a double-layer 1.5 inch baffle. The driver mounts to a 9.375 inch ring bonded under the baffle in a machined recess, carrying eight #8-32 hurricane nuts so it threads into steel rather than MDF. A windowed brace sits 3.22 inches clear of the cutout edge and 2.15 inches clear of the port terminus; the window is not weight saving, a solid panel there would split the cavity and make the box a bandpass. Walls seat into dados in both the lid and the baffle. Square corners, plush black carpet, side-mounted terminal cup.

No. This is an enclosure only, cut and folded for the AudioControl Spike SPK-8 specifically. The 7.250 inch cutout, the 4.291 inch mounting depth allowance and the 1.04 cubic foot alignment all come from AudioControl's published parameters for this exact driver, and the port is sized against its Xmax and power rating. It is not a universal box with an 8 inch hole in it. Bring your own driver.