Performance Optimized · Datasheet
Dayton Audio Ultimax II UMII8 Quad Box: Sealed 8" Wedge Wide Enclosure Quad 8" Sealed enclosure
- Net volume
- 1.137 cu ft per driver, 4.55 cu ft total, after the divider and an estimated 0.059 cu ft displacement per driver
- Max mounting depth
- 5.67 in required; 11.51 in clearance above the motor against the raked rear panel
- External dimensions
- 44 in W × 13 in at the seat face H × 23.00 in at the base D
- Front baffle
- 1.5 in double baffle, outer layer machined as a flush recess
- Best For: Quad Dayton Audio Ultimax II UMII8 SUV Cargo-Floor Builds
- Net Volume: 1.137 cu ft per Driver (4.55 cu ft Net Total)
- Driver Match: Four Dayton Audio Ultimax II UMII8 (Dual 2 Ohm), matched
- Construction: 2 Chambers | 44" Wide Wedge | V-Groove/Dado | Double 1.5" Baffle | 2 Terminal Cups
Spec of record
Technical specifications
| Specification | Value |
|---|---|
| Series | Proline X Performance Optimized Wedge Wide |
| Compatible Driver | Dayton Audio Ultimax II UMII8, quantity 4, matched. Direct fit |
| Configuration | Quad 8 inch sealed wedge, 2 chambers, 2 drivers per chamber |
| Mounting Position | SUV cargo floor, raked face against the rear seat back |
| Firing Direction | Rearward toward the liftgate. Not a down fire design |
| External Width | 44 in |
| External Height | 13 in at the seat face |
| External Depth | 23.00 in at the base, tapering to 18.27 in at the top |
| Internal Volume, Gross | 4.87 cu ft total |
| Internal Volume, Net Acoustic | 1.137 cu ft per driver, 4.55 cu ft total, after the divider and an estimated 0.059 cu ft displacement per driver |
| Driver Mounting Depth | 5.67 in required; 11.51 in clearance above the motor against the raked rear panel |
| Alignment Per Driver | UMII8-22 Qtc 0.842, fc 51.7 Hz, F3 44.7 Hz anechoic |
| Woofer Openings | 4 at 7.311 in |
| Woofer Layout | One row across the face |
| Frame Outer Diameter | 8.425 in |
| Fs / Qts / Qes / Qms | 46.0 Hz / 0.750 / 0.990 / 3.100 |
| Vas / Sd / Xmax | 8.4 L / 200 cm2 / 18 mm |
| Driver Power Handling | 400 W RMS per driver, 1600 W RMS for the set of 4 (thermal rating) |
| Recommended Amplifier | 280-400 W RMS per driver, 1,120-1,600 W RMS for the full set, at 4 ohms |
| Parameter Source | Dayton Audio published specifications |
| Material | Langboard Elite MDF |
| Construction | CNC cut, V-groove and dado joinery |
| Panel Thickness | 0.75 in |
| Front Baffle | 1.5 in double baffle, outer layer machined as a flush recess |
| Internal Bracing | One full-height 3/4 in divider |
| Driver Mounting | Threaded inserts, stainless machine screws included |
| Terminal Cups | Two Proline X ABS and carbon fiber composite, side mounted, one per chamber, pre wired 12 gauge OFC |
| Acrylic Insert | Gloss black acrylic baffle insert standard |
| Damping | Light polyfill wall lining in every chamber, does not alter acoustic volume |
| Carpet | Plush black |
| Shipping Weight | 85 lb |
| Warranty | 1 Year Limited |
| Built In | Tullahoma, Tennessee |
Modelled response
Performance in this enclosure
00Sizing the amplifier
Every wattage on this panel is per driver. This cabinet holds four, so the amplifier feeds all four at once.
01Is it a sealed driver?
Efficiency bandwidth product places the motor before anything else is decided.
02What the box does to it
1.137 cu ft against an 8.4 L Vas.
03The watts that reach Xmax (in this enclosure)
Travel scales with the square root of power, so there is one wattage that puts the cone exactly on 18.0 mm — and a bigger one once a subsonic filter stops it wasting travel below the passband.
| Param | Value | Unit | Note |
|---|---|---|---|
| Fs | 46.00 | Hz | free-air resonance |
| Qts | 0.750 | Dual 2 Ohm | |
| Vas | 8.40 | L | equivalent compliance |
| Sd | 200.0 | cm² | effective piston area |
| Xmax | 18 | mm | one-way linear travel |
| Pe | 400 | W | continuous RMS |
| SPL | 81.0 | dB | 1 W / 1 m, derived from T/S |
Driver parameters as published by Dayton Audio UMII8-22 published specifications. Curves computed against this enclosure’s actual net airspace.
From the shop floor
Installer's take
Start with the size. 1.137 cubic feet per driver puts the Ultimax II UMII8 at Qtc 0.842, resonance 51.7 Hz, half power 44.7 Hz anechoic. The wide platform stops at 23 inches deep, so this box lands a little above flat: a small lift near resonance and firm midbass.
Measure the base depth, not the top. This cabinet is 23.00 in deep where it meets the floor, 18.27 at the top, 44 wide and 13 tall. In an SUV the 44 has to clear between the rear wheel wells at floor height, the base depth is measured from the seat back with the seat upright and latched, and the 13 has to clear the cargo cover.
The two terminal cups are on the side panels, one per chamber, so they sit close to the wheel wells. Land the speaker wire on both before the box slides into its final spot, with slack to pull it forward again.
Two drivers share each chamber, so they have to match: same model, same coil, wired in phase. One driver reversed in a shared chamber pushes against its partner and the pair cancels instead of adding. Check polarity at each cup with a battery tap before the box goes in.
Impedance. UMII8-22: wire for 4 ohms (coils in series, each chamber's pair in series, both cups in parallel), the load most monoblocks are built to deliver full power into; 1 ohm is the other clean option (coils in series, each chamber's pair in parallel, both cups in parallel). Work the load out before you buy the amplifier, not after.
Power. Size the amplifier for the set, not one driver: 280 to 400 W RMS per driver is 1,120 to 1,600 W RMS across all 4 at 4 ohms. At 1,600 W the charging system is part of the install: alternator output, the big three, and a battery that holds voltage under load.
Dayton Audio's Qes and Qms reproduce the printed Qts within 3 percent, so the alignment rests on a self-consistent set. Dayton Audio do not publish driver displacement; we deduct an estimated 0.059 per driver, so true net can sit a few hundredths either way.
Polyfill is in as a wall lining in every chamber. Do not add more: it makes the box act larger and walks Qtc off 0.84.
Before you order
Questions
Does this fit the Dayton Audio Ultimax II UMII8, and its coil versions?
Yes. Each opening is cut to 7.311 in for the 8.425 in frame, and the 5.67 in deep motor clears the raked rear panel with 11.51 in to spare. Coil versions of the Dayton Audio Ultimax II UMII8 share the frame, cutout and mounting depth, so any of them drops in. The alignment on this page is computed on the UMII8-22 parameters.
Run four matched drivers, same model and same coil, so every chamber sees the alignment on this page.
Why 1.137 cubic feet per driver, and what alignment does it target?
On Dayton Audio's published Fs 46.0 Hz, Qts 0.750 and Vas 8.4 liters, 1.137 cubic feet per driver gives Qtc 0.842, system resonance 51.7 Hz and half power 44.7 Hz.
The wide platform stops at 23 inches deep, so this box lands a little above flat: a small lift near resonance and firm midbass.
What amplifier power should I run, and how should I wire it?
Dayton Audio rates the Ultimax II UMII8 at 400 watts RMS per driver. Recommended amplifier: 280 to 400 W RMS per driver, 1,120 to 1,600 W RMS for the full set of 4.
Each UMII8-22 has two 2 ohm voice coils, 4 ohms in series or 1 ohm in parallel. Wire every driver's coils in series. With the two drivers in each chamber in parallel and the two cups in parallel, the four present 1 ohm to a mono amplifier. With the two drivers in each chamber in series and the two cups in parallel, they present 4 ohms. Use the lower load only on an amplifier rated stable there.
Will it fit my SUV?
It is 44 inches wide, 13 tall and 23.00 deep at the base, tapering to 18.27 at the top. Measure between the rear wheel wells, the floor depth with the seat upright, and the height under your cargo cover.
The raked face goes against the seat back and the woofers fire toward the liftgate.
Why two drivers per chamber instead of four chambers?
Four chambers would need three dividers, and on a 44 inch face that space is needed for the woofers. Two matched drivers in one sealed chamber move together and see the same pressure, so each behaves as if it had half the chamber to itself: 1.137 cubic feet per driver here.
It also gives two terminal cups, one per pair, which keeps the wiring to the amplifier simple.
What is the expected low-frequency extension?
Anechoic F3 is 44.7 Hz per driver with system resonance at 51.7 Hz.
Those figures exclude cabin gain. An SUV cabin adds real output below about 50 Hz, so in-vehicle response runs deeper than the numbers above.
Do I need to add polyfill or damping?
No. Polyfill is already installed as a light wall lining in every chamber, and the quantity is chosen so it does not change the acoustic volume.
Do not add more. Packing a sealed box makes it behave as though it were larger, which moves the alignment away from 1.137 cubic feet per driver.
Are the drivers included?
No. This is an enclosure only. You receive the cabinet finished in plush black carpet with the gloss black acrylic baffle insert, two side-mounted pre-wired terminal cups, the polyfill lining in place, threaded inserts and stainless machine screws.
Bring four matched Dayton Audio Ultimax II UMII8 drivers. The cabinet is cut direct fit to them, not a general purpose 8 inch box.
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