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Professional Series Ported Dual 15" Enclosure Skar Audio VXF-15 · Dual 15" Ported enclosure

Net volume
3.37 Cubic Feet
Tuning
30.5 Hz
Max mounting depth
9.780 Inches (Skar Audio Spec)
Cutout
13.860 Inches (Skar Audio Spec)
External dimensions
45.00 Inches W × 18.00 Inches H × 17.00 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
Skar Audio VXF-15Buy at Audio Intensity
  • Alignment: 3.37 cu ft net vented at 30.5 Hz. F3 39.2 Hz anechoic, 0.05 dB passband ripple
  • Driver: Skar Audio VXF-15 D2/D4, 1500 W RMS, 30.0 mm Xmax, 31.40 Hz Fs
  • Build: Front-firing standard box, 2.25" three-layer baffle with the woofer flush-mounted in the outer layer, Skar Audio logo acrylic, dado joinery, 66.0 sq in front slot port beside the woofer with one bend along the back wall, port and excursion gated at 3600 W
  • Cabinet: 45.00" W x 18.00" H x 17.00" D, 79 lb, threaded insert kit included

Spec of record

Technical specifications

SeriesProline X Professional
Driver-Specific FitmentSkar Audio VXF-15 D2/D4 (Dual 2 Ohm or Dual 4 Ohm)
Enclosure TypePorted | Front-Firing Standard Box
External Width45.00 Inches
External Height18.00 Inches
External Depth17.00 Inches
Internal Volume (Gross)5.68 Cubic Feet
Internal Volume (Net After Displacement)3.37 Cubic Feet
Port TypeVertical Slot Beside The Woofer | Front Exit | One 90 Degree Bend Along The Back Wall
Port Geometry4.00 x 16.50 Inches, 66.0 Square Inches, 43.36 Inches Of Path
Port Area66.0 Square Inches
Port Tuning (Fb)30.5 Hz
Port Mouth1/2 In Roundover On All Four Edges, 87.5 Square Inches At The Face
Port Air Velocity22.1 m/s In The Channel, 16.6 m/s At The Mouth, At 3600 W (17.0 m/s Chuff Threshold)
Design Power Basis3600 W RMS (1.2 x The Driver Rating) For Port Velocity And Excursion
Predicted F339.2 Hz (Anechoic)
Passband Ripple0.05 dB (Anechoic)
Subsonic Filter24 Hz High-Pass, 24 dB/Octave - REQUIRED On A Vented Enclosure
Driver Fs31.40 Hz
Driver Qts0.360
Driver Qes / Qms0.380 / 4.740
Driver Vas76.800 Liters / 2.712 Cubic Feet
Driver Sd779.3 Square Centimeters
Driver Mms303.30 g
Driver BL24.90
Driver Xmax30mm (One-Way)
Driver Displacement0.23 Cubic Feet (Published by Skar Audio)
Driver Sensitivity89.7 dB
Driver Power Handling1500 Watts RMS
Driver Overall Diameter15.360 Inches (Skar Audio Spec)
Mounting Depth Required9.780 Inches (Skar Audio Spec)
Cutout Diameter13.860 Inches (Skar Audio Spec)
Flush Mount Recess16.375 Inches In The Outer Layer
MaterialLangboard Elite 3/4" MDF
ConstructionShopSabre CNC / Windowed Brace Front To Back Beside 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 Skar Audio Logo Insert, Outer Layer, Standard
Mounting HardwareThreaded Insert Kit Included: 8-12 Inserts, Drill Bit, 2.5 In Allen-Head Screws, Allen Key, Gasket Tape
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 Power1050-1500 Watts RMS (Skar Audio Rated: 1500W RMS)
Carpet FinishPlush Black
Shipping Weight88 lb
ShippingUPS Ground Parcel, Included In The 48 States
Bundle OptionsEnclosure Only (Bring Your Own Skar Audio VXF-15)
Warranty2-Year Limited (Enclosure)
ManufacturedTullahoma, Tennessee, USA

Modelled response

Performance in this enclosure

Net airspace
3.37
cu ft
Tuning
30.5
Hz · Fb
Half power
39.2
Hz · F3, anechoic
Xmax at
29600
W RMS · 24 Hz subsonic
With NO filter
6226
W RMS · unfiltered
Port
16.6
m/s at the mouth · 3600 W

01Is this driver right for a ported box?

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

EBP = Fs ÷ Qes = 82.6
SEALED 0–50 TRANSITION 50–100 PORTED 100–150 0 50 100 150 EBP 82.6
Skar Audio VXF-15 D2 · EBP 82.6
Between 50 and 100 a driver takes either load, and the choice becomes one of priorities rather than of physics. The Skar Audio VXF-15 D2 reads 82.6. Ported buys output and low-end reach around tuning; sealed buys a shallower rolloff below it. This cabinet takes the first trade.

02What the box does to it

3.37 cu ft net against a 153.6 L Vas, vented at 30.5 Hz.

Fb = 30.5 Hz  ·  F3 = 39.2 Hz  ·  passband ripple 0.05 dB
20 30 50 70 100 150 200 +4 0 −4 −8 −12 −16 −20 −24 −28 FREQUENCY · Hz LEVEL · dB −3 dB Fb 30.5
Skar Audio VXF-15 D2 · Fb 30.5 Hz, F3 39.2 Hz
Anechoic, before any cabin gain, with the 24 Hz subsonic filter already applied. The vent takes over below 30 Hz and the cone stops doing the work there, which is what holds travel down at the bottom of the passband.

03Perceived Ported vs Sealed

This cabinet, 3.37 cu ft net vented at 30.5 Hz, against Skar Audio's recommended sealed box, 2.75 cu ft per driver, 5.50 cu ft for the pair.

Ported Fb 30.5 Hz  ·  the 5.50 cu ft sealed box runs Qtc 0.51, Fc 44 Hz
20 30 50 70 100 150 200 +4 0 −4 −8 −12 −16 −20 −24 −28 FREQUENCY · Hz LEVEL · dB +2.8 dB at 37 Hz
Ported · this cabinet, 3.37 cu ft, Fb 30.5 HzSkar Audio's recommended sealed, 2.75 cu ft net x2, 5.50 cu ft, Qtc 0.51
Shaded blue is where the ported alignment is louder for the same power, orange where the sealed one is. The sealed curve is Skar Audio's recommended sealed box, 2.75 cu ft per driver, 5.50 cu ft for the pair, not this cabinet with the port blocked: two different boxes, because that is the choice a buyer actually has. Across 25 to 60 Hz the vent is worth 2.8 dB at its widest and 2.2 dB on average. This is the anechoic picture, which is not what you hear in a car.

04Real World Ported vs Sealed

The same two boxes with cabin gain applied, 45 Hz corner, 18 dB ceiling.

Flatness across 25–60 Hz: ported 2.5 dB spread, the 5.50 cu ft sealed box 3.6 dB
20 30 50 70 100 150 200 +4 0 −4 −8 −12 −16 −20 −24 −28 FREQUENCY · Hz LEVEL · dB +2.8 dB at 37 Hz
Ported, in-car · 2.5 dB spreadSkar Audio's recommended sealed, 2.75 cu ft net x2, 5.50 cu ft, in-car · 3.6 dB spread
Cabin gain lifts both boxes by the same amount, so the gap between them does not change: what changes is the shape each one ends up with. A car pressurises below roughly 45 Hz, which fills in the sealed box's shallower rolloff and over-drives it where the ported box is already flat. Across 25 to 60 Hz, the band kick and bass fundamentals occupy, this alignment holds 2.5 dB of spread against 3.6 dB for Skar Audio's recommended sealed box, 2.75 cu ft per driver, 5.50 cu ft for the pair. Flatter is the whole point of tuning this high. Note where the curves cross. Below about 23 Hz the sealed alignment becomes the louder of the two and stays louder all the way down, by up to 2.1 dB: a sealed box rolls off gently into the subsonic region where a vented one falls away steeply once it is below tuning and the vent stops contributing. If the content you are chasing lives below 23 Hz, a sealed alignment reaches further down than this one does. Cabin gain here is a house assumption, not a measurement of your vehicle.

05The watts that reach Xmax (in this enclosure)

Travel scales with the square root of power, so there is one wattage that puts both cones exactly on Skar's published 30.0 mm. The two traces are the same cabinet with the subsonic filter switched on and switched off. Every power figure in this section is for the pair, split evenly.

PXmax = 29600 W with a 24 Hz subsonic  ·  6226 W with none  →  the filter is worth 4.8×
20 30 50 70 100 150 200 0 8 16 24 32 FREQUENCY · Hz CONE TRAVEL · mm PAST LINEAR TRAVEL · Xmax 30.0 mm 29600 W reaches Xmax here
29600 W · subsonic at 24 Hz, 24 dB/oct6226 W · no subsonic filterXmax 30.0 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 30.0 mm. With a 24 Hz subsonic that takes 29600 W, reached first at 22 Hz. Take the filter away and the same cabinet reaches 30.0 mm on 6226 W — the filter is worth 4.8× 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 6226 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 — Skar rate this one at 3000 W RMS, and that is the number that binds first here: heat stops you before travel does, so treat 3000 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 one for a pair of VXF-15 in a single shared chamber, which is how a dual ported box should be built: one volume, one port, both drivers loading the same air.

It gets the full Professional treatment, a 2.25 inch three-layer baffle with both woofers flush mounted in the outer layer, and the port on the left of the face.

Wiring is where a dual bites you. These are two 2 ohm coils each, so you can land on 0.5 ohm with all four coils in parallel, 2 ohms as two series pairs in parallel, or 8 ohms with everything in series. Check what your amplifier is rated for before you wire it, not after.

Skar Audio publishes no mounting hole locations for the VXF-15, so the inserts are not in the baffle when the box arrives. The insert kit is in the box: set the inserts where the woofer's own holes fall, with the drill bit and the 2.5 inch allen-head screws in the kit, and lay the gasket tape before the woofer goes down.

It ships dry. Do not add polyfill to a ported box. Set your subsonic filter at 24 Hz.

Before you order

Questions

Why is this enclosure tuned to 30.5 Hz?

Both drivers share one chamber and one port rather than sitting in separate boxes, so the pair works against the whole volume and the port is sized for the pair rather than doubled. The port carries 66.0 square inches of area at 30.5 Hz, and the design power for the velocity and excursion checks is 3600 W for the pair. Passband ripple holds at 0.05 dB across the tuning, with F3 at 39.2 Hz. 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?

Every driver is run through the Performance Optimized wedge and down-fire before this chassis; the Professional box is where a driver lands when that smaller envelope, 30 inches wide and 18 inches deep with a triangular side port, cannot give it what it needs at its rated power. The VXF-15 did not clear the port gate there. The calmest wedge port that fits that envelope is 26.4 square inches at 24.0 by 11.12 by 17.86 inches, and its mouth runs 21.3 metres per second at 1500 W against the 17 metres per second line where a port starts to chuff. That port would stay clean to about 957 W. The slot on this box reaches 66.0 square inches and holds the mouth at 16.6 metres per second at 3600 W. An under-ported box does not fail quietly. Air speed at the mouth rises with power; past the chuff line the flow turns turbulent and the port is audible on every note. The turbulence also chokes the port, so the box behaves as if it were tuned higher than it is, loses output near tuning, and lets the cone travel further below tuning than the design allows. This chassis is a full-size front-firing box on a 2.25 inch baffle built from three 3/4 inch layers with the woofer flush-mounted in the outer layer, a Skar Audio logo acrylic, and a port and excursion budget checked at 3600 W. It carries a 2 year warranty, against 1 year on the Performance Optimized lines.

Threaded inserts or a kit?

Skar Audio does not publish the mounting hole locations for the VXF-15, so we cannot install the threaded inserts before it ships. The threaded insert kit comes in the box instead: inserts sized to the woofer, the correct drill bit, 2.5 inch allen-head screws, an allen key and woofer gasket tape. You set the inserts when you mount the woofer, and this box ships with two kits, one per woofer.

Do I need a subsonic filter?

Yes, at 24 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 Skar Audio VXF-15 at 35 percent of its usable travel at 3600 W.

Would a sealed box be better for me?

Below about 23 Hz, yes. The maker's recommended sealed box is louder down there by up to 2.1 dB, because a sealed box rolls off gently into the subsonic region where a vented one falls away steeply once it is under tuning. Above that this alignment is the louder of the two for the same power. The Performance Graphs tab plots this cabinet, 3.37 cubic feet vented at 30.5 Hz, against Skar Audio's recommended sealed box, 2.75 cu ft per driver, 5.50 cu ft for the pair, so you can see exactly where they cross.

How does the front port work?

It is a vertical slot beside the woofer, the full height of the cavity, 4.00 inches wide and 66.0 square inches. It runs 9.25 inches to the back wall and turns once along it for 26.36 inches; the fold costs about 1.5 Hz and the port is cut for it. The channel runs at 22.1 metres per second at 3600 W, 44 percent of its turbulence limit, and the mouth edges carry a 1/2 inch roundover so the air leaves the face at 16.6 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?

79 lb, 45.00" W x 18.00" H x 17.00" D external. Every Professional cabinet is priced the same way, by its size: this one is 7.97 cubic feet outside. Delivery to the 48 states is inside the price; it ships as a 79 lb parcel and checkout adds nothing. Do not add polyfill; it ships dry on purpose.

Is the VXF-15 included?

No. This is an enclosure only, cut for the Skar Audio VXF-15 specifically: the 13.860 inch cutout, the 9.780 inch mounting depth allowance and the 3.37 cubic foot alignment all come from Skar Audio's published parameters. It fits both coil versions (D2 and D4), and the cabinet was checked against both. Bring your own driver.

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