Proline X

Dayton Audio Ultimax II UMII15 Box: Ported 15" Professional Series Enclosure

Q: Do I need a subsonic filter?

Yes, at 25 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 Dayton Audio Ultimax II UMII15 at 39 percent of its usable travel at 1080 W.

Q: Would a sealed box be better for me?

Not one we can show you. We do not build a sealed enclosure for the Dayton Audio Ultimax II UMII15 and Dayton Audio 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 25 Hz subsonic filter takes over; around 32.0 Hz the vent carries the load and cone travel drops to its minimum, which no sealed alignment can do.

Q: How does the front port work?

It is a vertical slot beside the woofer, the full height of the cavity, 1.75 inches wide and 28.9 square inches. It runs 8.50 inches to the back wall and turns once along it for 4.35 inches; the fold costs about 1.5 Hz and the port is cut for it. The channel runs at 21.1 metres per second at 1080 W, 55 percent of its turbulence limit, and the mouth edges carry a 1/2 inch roundover so the air leaves the face at 12.7 metres per second against the 17 metres per second threshold where a slot starts to chuff.

Q: What does the price cover, and how does it ship?

64 lb, 36.00" W x 18.00" H x 14.00" D external. Every Professional cabinet is priced the same way, by its size: this one is 5.25 cubic feet outside. Delivery to the 48 states is inside the price; it ships as a 64 lb parcel and checkout adds nothing. The Performance Optimized 15 inch ported wedge is $519.99. The $34 difference is the larger box and the port this driver needs to run at its rating. Do not add polyfill; it ships dry on purpose.

Q: Is the Ultimax II UMII15 included?

No. This is an enclosure only, cut for the Dayton Audio Ultimax II UMII15 specifically: the 13.937 inch cutout, the 8.110 inch mounting depth allowance and the 2.93 cubic foot alignment all come from Dayton Audio's published parameters. Dayton make the UMII15 in one version, dual 2 ohm (UMII15-22). Bring your own driver.

SKU: Pro 15-P UMII15

QUICK SPECS

Alignment: 2.93 cu ft net vented at 32.0 Hz. F3 31.2 Hz anechoic, 3.68 dB passband ripple
Driver: Dayton Audio Ultimax II UMII15 D2, 900 W RMS, 24.0 mm Xmax, 29.00 Hz Fs
Build: Front-firing standard box, 2.25" three-layer baffle with the woofer flush-mounted in the outer layer, Dayton Audio logo acrylic, dado joinery, 28.9 sq in front slot port beside the woofer with one bend along the back wall, port and excursion gated at 1080 W
Cabinet: 36.00" W x 18.00" H x 14.00" D, 64 lb, threaded inserts pressed into the baffle on the published 14.606 inch bolt circle

Shipping Included No freight charges at checkout on US orders. International orders are quoted live carrier rates at checkout.

Built in Tennessee CNC cut from 3/4" Langboard Elite MDF. V-groove and dado joinery.

Advanced Terminal Cup Built in-house. ABS/Carbon Fiber. Stainless steel hardware. Copper ring terminals.

$ 553.99

In Stock and Ready to Ship

Financing available. Choose Shop Pay Installments at checkout.

Complete Your System

Prodigy Audio 1200 Watt Mono Block Amplifier NBM1200.1 - Prodigy Amplifier for car audio systems

Prodigy Audio Prodigy Audio 1200 Watt Mono Block Amplifier | NBM1200.1 $ 272.99

Dayton Audio Ultimax II UMII15 Box: Ported 15" Professional Series Enclosure

$ 553.99

More enclosures cut for Dayton Audio subwoofers: Dayton Audio Subwoofer Boxes

Enclosure Type Ported

External Dimensions 36.00" W x 18.00" H x 14.00" D

Net Volume 2.93 cu ft

Tuning Frequency 32.0 Hz

Port Area 28.9 Square Inches

Shipping Weight 71 lbs

INSTALLER'S TAKE

I built this box for one UMII15 on the full Professional chassis: 2.93 cubic feet net at 32.0 Hz, three layers of baffle with the frame flush in the outer one, and a slot port that turns once along the back wall.

Dayton make the UMII15 in one version, dual 2 ohm (UMII15-22).

Dayton rate it 900 W RMS. Set the subsonic filter near 26 Hz and leave it there; it ships dry, no polyfill in a ported box.

Product Details

Proline X Professional 15" Ported

One Ultimax II UMII15 in a front-firing Professional box, vented at 32.0 Hz on a three-layer flush-mount baffle

2.93 cu ft net Tuned 32.0 Hz F3 31.2 Hz 2.25" three-layer baffle Cut for the Ultimax II UMII15 Built in Tennessee

2.93cu ft net

32.0Hz tuning

31.2Hz F3 anechoic

28.9sq in port area

Why this driver is vented at 32.0 Hz

The UMII15 is the 15 inch from Dayton's long-throw Ultimax II line: 29 Hz, a Qts of 0.7, 96 litres of Vas and 24 mm of excursion, rated 900 W RMS. This cabinet gives it 2.93 cubic feet net behind a 2.25 inch three-layer baffle, vented at 32.0 Hz through a 28.9 square inch slot beside the woofer, for an anechoic F3 of 31.2 Hz in a 36 by 18 by 14 inch front-firing box.

The slot is gated at 1080 W: the channel runs 21.1 m/s and the mouth 12.7, and the cone peaks at 9.4 of its 24 mm with the subsonic filter in place. Passband ripple is 3.7 dB.

What makes it Professional

Three-layer baffle, flush mount

Three layers of 3/4 inch Langboard Elite make a 2.25 inch front. The outer layer is routed to the flange, so the woofer sits flush with the face; the two layers behind it carry the mounting hardware and the load.

Dayton Audio logo acrylic

A glossy black acrylic insert with the Dayton Audio mark sits in the outer layer beside the woofer. It is standard on every Professional cabinet.

Mounting

Threaded inserts pressed into the baffle on the published 14.606 inch bolt circle, stainless machine screws included.

Port gated at 1080 W

The 28.9 square inch slot beside the woofer is sized so the channel runs 21.1 metres per second and the mouth 12.7 metres per second at 1.2 times the driver's rating, under the 17 metres per second where a slot starts to chuff. The channel runs 8.50 inches along its wall and turns once along the back wall for another 4.35 inches, which is why a 32.0 Hz tuning fits a 14.00 inch deep box.

Why this is a Professional build

The Ultimax II UMII15 also builds in the Performance Optimized ported wedge, the smaller and cheaper box. The Professional cabinet is the step up for it: a 2.25 inch three-layer baffle with the woofer flush in the outer layer, and a slot port gated at 1080 W.

What the price covers

Every Professional cabinet is priced the same way, by its size: this one is 5.25 cubic feet outside. Delivery to the 48 states is inside the price; it ships as a 64 lb parcel and checkout adds nothing. The Performance Optimized 15 inch ported wedge is $519.99. The $34 difference is the larger box and the port this driver needs to run at its rating.

The cabinet

36.00" W x 18.00" H x 14.00" D external. Two windowed braces run front to back either side of the woofer, clearing the cutout by two and a half inches. The box ships dry: polyfill detunes a ported alignment. Inside the Professional envelope for a single 15, 36 inches wide, 18 tall and 14 deep. 15.315 inch frame, flush in the outer baffle layer, 13.937 inch cutout, 8.11 inches of mounting depth. Dayton print the bolt circle, so the threaded inserts are pressed at the shop. It ships as a parcel.

Dayton publish a complete parameter table for the UMII15-22 that holds together on Qts, moving mass and motor strength. The Ultimax II product pages mislabel fitment (their cutout figure is the magnet), so the cutout, frame and depth come from Dayton's spec-sheet drawing. Displacement is not published; 0.176 cubic feet is our estimate. Tuning includes a 1.5 Hz fold loss that is an estimate, not a bench measurement.

The numbers to respect

Set a 25 Hz subsonic filter, 24 dB per octave. Below tuning the vent stops loading the cone; with the filter in place the cone reaches 9.4 mm of its 24.0 mm at 1080 W.

Enclosure Specifications

Series	Proline X Professional
Driver-Specific Fitment	Dayton Audio Ultimax II UMII15 D2 (Dual 2 Ohm)
Enclosure Type	Ported \| Front-Firing Standard Box
External Width	36.00 Inches
External Height	18.00 Inches
External Depth	14.00 Inches
Internal Volume (Gross)	3.52 Cubic Feet
Internal Volume (Net After Displacement)	2.93 Cubic Feet
Port Type	Vertical Slot Beside The Woofer \| Front Exit \| One 90 Degree Bend Along The Back Wall
Port Geometry	1.75 x 16.50 Inches, 28.9 Square Inches, 18.35 Inches Of Path
Port Area	28.9 Square Inches
Port Tuning (Fb)	32.0 Hz
Port Mouth	1/2 In Roundover On All Four Edges, 48.1 Square Inches At The Face
Port Air Velocity	21.1 m/s In The Channel, 12.7 m/s At The Mouth, At 1080 W (17.0 m/s Chuff Threshold)
Design Power Basis	1080 W RMS (1.2 x The Driver Rating) For Port Velocity And Excursion
Predicted F3	31.2 Hz (Anechoic)
Passband Ripple	3.68 dB (Anechoic)
Subsonic Filter	25 Hz High-Pass, 24 dB/Octave - REQUIRED On A Vented Enclosure
Driver Fs	29.00 Hz
Driver Qts	0.700
Driver Qes / Qms	1.000 / 2.340
Driver Vas	96.000 Liters / 3.390 Cubic Feet
Driver Sd	791.0 Square Centimeters
Driver Mms	279.00 g
Driver BL	14.60
Driver Re	4.2 Ohm
Driver Xmax	24mm (One-Way)
Driver Displacement	0.18 Cubic Feet (Published by Dayton Audio)
Driver Sensitivity	88.5 dB
Driver Power Handling	900 Watts RMS
Driver Overall Diameter	15.315 Inches (Dayton Audio Spec)
Mounting Depth Required	8.110 Inches (Dayton Audio Spec)
Cutout Diameter	13.937 Inches (Dayton Audio Spec)
Flush Mount Recess	16.250 Inches In The Outer Layer
Material	Langboard Elite 3/4" MDF
Construction	ShopSabre CNC / Two Windowed Braces Front To Back Either Side Of The Woofer
Joinery	Dado Joinery (CNC-Cut), Flat Panels
Front Baffle Construction	Three 3/4" MDF layers, 2.25" total \| Woofer Flush-Mounted In The Outer Layer
Baffle Layers	3
Acrylic	Glossy Black Dayton Audio Logo Insert, Outer Layer, Standard
Mounting Hardware	Threaded Inserts On The Published 14.606 In Bolt Circle \| Stainless Machine Screws Included
Voice Coil Configuration	Dual 2 Ohm
Terminal Cup	Proline X ABS/Carbon Fiber Composite \| Back Panel, Terminal-Cup Side \| 12g OFC Pre-Wired
Damping	None - Ships Dry. Polyfill Detunes A Ported Enclosure
Recommended Power	630-900 Watts RMS (Dayton Audio Rated: 900W RMS)
Carpet Finish	Plush Black
Shipping Weight	71 lb
Shipping	UPS Ground Parcel, Included In The 48 States
Bundle Options	Enclosure Only (Bring Your Own Dayton Audio Ultimax II UMII15)
Warranty	2-Year Limited (Enclosure)
Manufactured	Tullahoma, Tennessee, USA

Performance Graphs

Net airspace

2.93

cu ft

Tuning

32.0

Hz · Fb

Half power

31.2

Hz · F3, anechoic

Xmax at

7001

W RMS · 25 Hz subsonic

With NO filter

1171

W RMS · unfiltered

Port

12.7

m/s at the mouth · 1080 W

01Is this driver right for a ported box?

Efficiency bandwidth product places the motor before anything else is decided.

EBP = Fs ÷ Qes = 29.0

Dayton Audio UMII15-22 · EBP 29.0

Under 50 the raw number leans sealed. The Dayton Audio UMII15-22 reads 29.0, so this is a ported build against the grain of its own EBP: it works because the alignment is tuned for in-car response rather than for an anechoic curve, and because the cabinet holds port area and volume the driver can actually use.

02What the box does to it

2.93 cu ft net against a 96.0 L Vas, vented at 32.0 Hz.

Fb = 32.0 Hz · F3 = 31.2 Hz · passband ripple 3.68 dB

Dayton Audio UMII15-22 · Fb 32.0 Hz, F3 31.2 Hz

Anechoic, before any cabin gain, with the 25 Hz subsonic filter already applied. The vent takes over below 32 Hz and the cone stops doing the work there, which is what holds travel down at the bottom of the passband.

03Ported vs Sealed

No sealed comparison is shown for this driver.

A ported-versus-sealed chart is only worth reading against a sealed box someone would actually build: the one we make for the driver, or the one its maker recommends. Neither exists for the Dayton Audio UMII15-22 — we do not build a sealed enclosure for it and Dayton publish no sealed volume for it — so rather than compare this cabinet against itself stuffed and sealed, a box no one would build, the comparison is left out.

04The 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 Dayton's published 24.0 mm. The two traces are the same cabinet with the subsonic filter switched on and switched off.

P_Xmax = 7001 W with a 25 Hz subsonic · 1171 W with none → the filter is worth 6.0×

7001 W · subsonic at 25 Hz, 24 dB/oct1171 W · no subsonic filterXmax 24.0 mm one-way, published

Each trace touches the limit and no further, because each is drawn at the exact power that puts the cone on 24.0 mm. With a 25 Hz subsonic that takes 7001 W, reached first at 22 Hz. Take the filter away and the same cabinet reaches 24.0 mm on 1171 W — the filter is worth 6.0× the safe power. A vent unloads the cone below tuning, so there is nothing holding it once the box stops loading: on a sealed build a subsonic filter is an improvement, here it is required equipment. The unfiltered trace is still rising where this chart stops at 20 Hz, so treat 1171 W as a bound rather than a floor. Every wattage on this page is a MECHANICAL limit, not an electrical one. It is the power at which the cone runs out of linear travel in this cabinet, and nothing more. What the voice coil can dissipate as heat is a separate ceiling set by the driver, not by the box — Dayton rate this one at 900 W RMS, and that is the number that binds first here: heat stops you before travel does, so treat 900 W as the ceiling and the travel figures above as headroom. Final wired impedance, amplifier output and how long you hold the level are all electrical questions this graph does not answer.

Woofer Details

Materials

Material

Built From a Spec Sheet, Not a Sales Sheet

Every Proline X Professional Series enclosure is CNC-cut from Langboard Elite MDF, 3/4" (18mm) panels produced to published mill specifications. Most enclosure manufacturers source generic MDF without published data. We can tell you the internal bond rating, the modulus of elasticity, the modulus of rupture, and the face and edge screw holding strength for every panel in this enclosure, because we chose the material based on those numbers, not on price or availability.

Langboard Elite is produced in the United States. The specifications below are pulled directly from Langboard's published mill data and are verifiable. This is the same panel stock used in our full Proline X lineup.

Specifications

Langboard Elite MDF: Published Mill Data

Property	Value	Why It Matters
Panel Stock	Langboard Elite MDF	Named, verifiable panel source, not generic "high-density MDF"
Thickness	3/4" (18mm)	Industry standard for subwoofer enclosures; panels below this flex under pressure
Density	48.5 lbs/ft³	Higher density = less porosity, better screw retention, reduced resonance
Internal Bond	200 psi	Measures resistance to delamination under sustained internal pressure. The most enclosure-relevant spec on this sheet
Modulus of Rupture (MOR)	4,200 psi	Bending strength before the panel breaks, relevant for larger unsupported baffle spans
Modulus of Elasticity (MOE)	410,000 psi	Stiffness under load; higher MOE means less panel flex under bass pressure, less resonance
Face Screw Holding	325 lbs	How firmly the panel surface holds a screw; critical for baffle joint integrity over time
Edge Screw Holding	250 lbs	Panel edge retention, relevant for every joint that isn't face-to-face

Internal Bond

200 psi: The Number That Actually Matters for Enclosures

The internal bond rating measures how well the MDF panel resists delamination under sustained pressure applied perpendicular to the face. In a subwoofer enclosure, every bass transient generates a pressure pulse that pushes outward on every panel simultaneously. A panel that begins to delaminate internally loses stiffness gradually. The symptoms are slow: a box that starts to sound softer, less defined, less punchy over months of use. 200 psi internal bond is the spec that determines how long this enclosure holds its acoustic integrity under daily use at real power levels.

Stiffness

410,000 psi MOE: Less Flex, Less Resonance

The modulus of elasticity measures panel stiffness, its resistance to bending under load. A stiffer panel flexes less under the pressure generated by a high-excursion driver at volume. Panel flex is a source of acoustic coloration: the panel itself begins to radiate sound at its own resonant frequency, adding distortion to the output. 410,000 psi stiffness combined with V-groove and dado joinery means the panels stay rigid and the bracing controls resonance at the structure level, not the panel level. The bass you hear comes from the driver, not the box.

Screw Holding

325 lb Face / 250 lb Edge: Joints That Stay Locked

Screw holding strength determines how firmly the panel grips a fastener at the face and at the edge. This matters most at the baffle joint, where the front panel meets the side panels and where the driver is mounted. A panel with low screw holding strength allows fasteners to loosen over time under vibration, leading to air gaps at the joint and loss of acoustic seal. 325 lb face screw holding strength means the baffle hardware stays put. Combined with dado joinery and adhesive, the front panel on a Proline X Professional Series enclosure is not going anywhere.

Sourcing

Named Panel Stock: Not "Premium MDF"

The phrase "premium MDF" or "high-density MDF" appears on marketing copy for enclosures across every price point, from $40 to $400. It is not a specification. It is a description with no defined standard. Langboard Elite is a named, sourced, mill-documented product with published data. We name it in our copy because naming it holds us accountable to the spec. You can look up Langboard Elite independently, verify the numbers on this page, and confirm you are getting what we say you are getting. That is the point.

Why Proline X?

Most enclosures are built to a price point. Proline X is built to a spec. Every box starts with published-data MDF, gets CNC-cut to exact internal volume, and is assembled by hand in our Tennessee facility. The difference shows up in the measurements, and in how the box holds up two years into daily use.

CNC-Cut to Spec

Panels are machine-cut on ShopSabre CNC routers and joined with V-groove and dado joinery. Consistent geometry, no hand-cut variance, no gaps at the joints.