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

Net volume
2.93 Cubic Feet
Tuning
32.0 Hz
Max mounting depth
8.110 Inches (Dayton Audio Spec)
Cutout
13.937 Inches (Dayton Audio Spec)
External dimensions
36.00 Inches W × 18.00 Inches H × 14.00 Inches D
Front baffle
Three 3/4" MDF layers, 2.25" total | Woofer Flush-Mounted In The Outer Layer
Buy at Audio IntensityFactory-direct, ships from Tullahoma
Dayton Audio Ultimax II UMII15Buy at Audio Intensity
  • 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

Spec of record

Technical specifications

SeriesProline X Professional
Driver-Specific FitmentDayton Audio Ultimax II UMII15 D2 (Dual 2 Ohm)
Enclosure TypePorted | Front-Firing Standard Box
External Width36.00 Inches
External Height18.00 Inches
External Depth14.00 Inches
Internal Volume (Gross)3.52 Cubic Feet
Internal Volume (Net After Displacement)2.93 Cubic Feet
Port TypeVertical Slot Beside The Woofer | Front Exit | One 90 Degree Bend Along The Back Wall
Port Geometry1.75 x 16.50 Inches, 28.9 Square Inches, 18.35 Inches Of Path
Port Area28.9 Square Inches
Port Tuning (Fb)32.0 Hz
Port Mouth1/2 In Roundover On All Four Edges, 48.1 Square Inches At The Face
Port Air Velocity21.1 m/s In The Channel, 12.7 m/s At The Mouth, At 1080 W (17.0 m/s Chuff Threshold)
Design Power Basis1080 W RMS (1.2 x The Driver Rating) For Port Velocity And Excursion
Predicted F331.2 Hz (Anechoic)
Passband Ripple3.68 dB (Anechoic)
Subsonic Filter25 Hz High-Pass, 24 dB/Octave - REQUIRED On A Vented Enclosure
Driver Fs29.00 Hz
Driver Qts0.700
Driver Qes / Qms1.000 / 2.340
Driver Vas96.000 Liters / 3.390 Cubic Feet
Driver Sd791.0 Square Centimeters
Driver Mms279.00 g
Driver BL14.60
Driver Re4.2 Ohm
Driver Xmax24mm (One-Way)
Driver Displacement0.18 Cubic Feet (Published by Dayton Audio)
Driver Sensitivity88.5 dB
Driver Power Handling900 Watts RMS
Driver Overall Diameter15.315 Inches (Dayton Audio Spec)
Mounting Depth Required8.110 Inches (Dayton Audio Spec)
Cutout Diameter13.937 Inches (Dayton Audio Spec)
Flush Mount Recess16.250 Inches In The Outer Layer
MaterialLangboard Elite 3/4" MDF
ConstructionShopSabre CNC / Two Windowed Braces Front To Back Either Side Of The Woofer
JoineryDado Joinery (CNC-Cut), Flat Panels
Front Baffle ConstructionThree 3/4" MDF layers, 2.25" total | Woofer Flush-Mounted In The Outer Layer
Baffle Layers3
AcrylicGlossy Black Dayton Audio Logo Insert, Outer Layer, Standard
Mounting HardwareThreaded Inserts On The Published 14.606 In Bolt Circle | Stainless Machine Screws Included
Voice Coil ConfigurationDual 2 Ohm
Terminal CupProline X ABS/Carbon Fiber Composite | Back Panel, Terminal-Cup Side | 12g OFC Pre-Wired
DampingNone - Ships Dry. Polyfill Detunes A Ported Enclosure
Recommended Power630-900 Watts RMS (Dayton Audio Rated: 900W RMS)
Carpet FinishPlush Black
Shipping Weight71 lb
ShippingUPS Ground Parcel, Included In The 48 States
Bundle OptionsEnclosure Only (Bring Your Own Dayton Audio Ultimax II UMII15)
Warranty2-Year Limited (Enclosure)
ManufacturedTullahoma, Tennessee, USA

Modelled response

Performance in this enclosure

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
SEALED 0–50 TRANSITION 50–100 PORTED 100–150 0 50 100 150 EBP 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
20 30 50 70 100 150 200 +8 +4 0 −4 −8 −12 −16 −20 −24 FREQUENCY · Hz LEVEL · dB −3 dB Fb 32.0
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.

PXmax = 7001 W with a 25 Hz subsonic  ·  1171 W with none  →  the filter is worth 6.0×
20 30 50 70 100 150 200 0 8 16 24 FREQUENCY · Hz CONE TRAVEL · mm PAST LINEAR TRAVEL · Xmax 24.0 mm 7001 W reaches Xmax here
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.

From the shop floor

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.

Before you order

Questions

Why is this enclosure tuned to 32.0 Hz?

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. Tuning is chosen for in-car response rather than an anechoic curve: a vehicle adds roughly 12 dB per octave below about 45 Hz, and this tuning is where that sum comes out flattest across 25 to 60 Hz.

Why is this a Professional build and not a Performance Optimized box?

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. It carries a 2 year warranty, against 1 year on the Performance Optimized lines.

Threaded inserts or a kit?

Threaded inserts pressed into the baffle on the published 14.606 inch bolt circle, stainless machine screws included. The inserts are in the baffle when it arrives; the machine screws are in the terminal cup bag.

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.

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.

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.

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. Do not add polyfill; it ships dry on purpose.

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.

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