Pro 15-P FI NEO37 placeholder
Pro 15-P FI NEO37 placeholder

Proline X

Professional Series Ported 15" Enclosure | Fi Car Audio NEO 3.7 15

SKU: Pro 15-P FI NEO37

QUICK SPECS
  • Alignment: 3.04 cu ft net vented at 35.0 Hz. F3 30.9 Hz anechoic, 1.43 dB passband ripple
  • Driver: Fi Car Audio NEO 3.7 15 D1/D2, 2500 W RMS, 34.0 mm Xmax, 33.30 Hz Fs
  • Build: Front-firing standard box, 2.25" three-layer baffle with the woofer flush-mounted in the outer layer, Fi Car 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 2500 W
  • Cabinet: 36.00" W x 18.00" H x 18.00" D, 73 lb, threaded insert kit included
Shipping Icon
Shipping Included No freight charges at checkout on US orders. International orders are quoted live carrier rates at checkout.
USA Flag Rounded
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.
$ 651.99
In Stock and Ready to Ship
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Pro 15-P FI NEO37 placeholder

Professional Series Ported 15" Enclosure | Fi Car Audio NEO 3.7 15

Regular price $ 651.99
Sale price $ 651.99 Regular price
Unit price
Enclosure Type Ported
External Dimensions 36.00" W x 18.00" H x 18.00" D
Net Volume 3.04 cu ft
Tuning Frequency 35.0 Hz
Port Area 66.0 Square Inches
Shipping Weight 81 lbs
INSTALLER'S TAKE

I built this box for one NEO 3.7 15 on the full Professional chassis: three layers of baffle with the frame flush in the outer one, and a slot port that runs along the back wall to put 35.0 Hz in a 18.0 inch deep box.

One cabinet serves both coils. It was solved so the NEO 3.7 15 D2 and the NEO 3.7 15 D1 each pass every velocity, excursion and ripple gate in the same box.

Fi publishes no bolt circle, so the box ships with a threaded insert kit rather than pressed inserts.

2500 watts RMS by Fi's rating, and the port is sized for exactly that. The dual 2 ohm wires to 4 ohms in series or 1 ohm in parallel; the dual 1 ohm to 2 ohms series or 0.5 ohm parallel, which few amplifiers tolerate. Fi Car Audio publishes no mounting hole locations for the NEO 3.7 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 28 Hz.

Product Details
Enclosure Specifications
Performance Graphs
Woofer Details
Materials
Product Details

Proline X Professional 15" Ported

One NEO 3.7 15 in a front-firing box, vented at 35.0 Hz on a three-layer flush-mount baffle

3.04 cu ft net Tuned 35.0 Hz F3 30.9 Hz 2.25" three-layer baffle Cut for the NEO 3.7 15 Built in Tennessee
3.04cu ft net
35.0Hz tuning
30.9Hz F3 anechoic
66.0sq in port area

Why this driver is vented at 35.0 Hz

The NEO 3.7 15 is Fi's 15 inch at 33.3 Hz, a Qts of 0.38, 61.4 litres of Vas and 2500 W RMS. This cabinet gives it 3.04 cubic feet net behind a 2.25 inch three-layer baffle, vented at 35.0 Hz through a 66.0 square inch slot beside the woofer, for an anechoic F3 of 30.9 Hz in a 36 by 18 by 18.0 inch front-firing box.

Threaded insert kit ships with this box. Fi Car Audio does not publish the mounting hole locations for the NEO 3.7 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 one kit.

Fi publishes ported figures only for the NEO line, and with a Qts of 0.37 a sealed box would be overdamped. The slot is gated at 2500 W, Fi's own rating: the channel runs 22.2 m/s and the mouth 16.7, and the cone peaks at 11.8 of its 34 mm with the subsonic filter in place. Fi's own ported recommendation for its 15 inch NEO motors is 3 to 5 cubic feet.

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.

Fi Car Audio logo acrylic

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

Threaded insert kit ships with this box

Threaded insert kit included, inserts NOT pre-installed: the manufacturer publishes no mounting hole locations, so the kit ships with the box for installation when the woofer goes in: 8 to 12 inserts sized to the woofer, the correct drill bit, 2.5 inch allen-head screws, allen key and gasket tape.

Port gated at 2500 W

The 66.0 square inch slot beside the woofer is sized so the channel runs 22.2 metres per second and the mouth 16.7 metres per second at the driver's rated power, under the 17 metres per second where a slot starts to chuff. The channel runs 10.25 inches along its wall and turns once along the back wall for another 17.75 inches, which is why a 35.0 Hz tuning fits a 18.00 inch deep box.

Why this is a Professional build

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 NEO 3.7 15 does not fit that envelope at all: no tuning, width or depth inside it carries an 11.00 inch deep 15 inch driver at 2500 W. This box is the chassis with the width, depth and port to carry it.

What the price covers

Every Professional cabinet is priced the same way, by its size: this one is 6.75 cubic feet outside. Delivery to the 48 states is inside the price; it ships as a 73 lb parcel and checkout adds nothing.

The cabinet

36.00" W x 18.00" H x 18.00" 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 36 by 18 Professional envelope for a single 15, 18.0 inches deep. 15.625 inch frame, flush in the outer baffle layer, 14.125 inch cutout, 11.00 inches of mounting depth. It ships as a parcel.

Fi publishes its Thiele-Small table and a one-way Xmax of 34 mm on the NEO 3.7 15 product page, but does not say how the Xmax was measured, so we size port and power against it rather than past it. Fi's printed moving mass for the NEO 3.7 15 is the MT 15's figure carried across, so we left it out; Fs, Qts and Vas agree with the 12 and 18 in the same family and the alignment rests on those. The slot mouth runs 16.7 m/s at Fi's rating against a 17 m/s limit, so this is a box to run at its rating, not past it. Tuning includes a 1.5 Hz fold loss that is an estimate, not a bench measurement. Fi Car Audio does not publish the mounting hole locations for the NEO 3.7 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 one kit.

The numbers to respect

Set a 28 Hz subsonic filter, 24 dB per octave. Below tuning the vent stops loading the cone; with the filter in place the cone reaches 11.8 mm of its 34.0 mm at 2500 W.

Enclosure Specifications
SeriesProline X Professional
Driver-Specific FitmentFi Car Audio NEO 3.7 15 D1/D2 (Dual 1 Ohm or Dual 2 Ohm)
Enclosure TypePorted | Front-Firing Standard Box
External Width36.00 Inches
External Height18.00 Inches
External Depth18.00 Inches
Internal Volume (Gross)4.80 Cubic Feet
Internal Volume (Net After Displacement)3.04 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, 35.75 Inches Of Path
Port Area66.0 Square Inches
Port Tuning (Fb)35.0 Hz
Port Mouth1/2 In Roundover On All Four Edges, 87.5 Square Inches At The Face
Port Air Velocity22.2 m/s In The Channel, 16.7 m/s At The Mouth, At 2500 W (17.0 m/s Chuff Threshold)
Design Power Basis2500 W RMS (1.0 x The Driver Rating) For Port Velocity And Excursion
Predicted F330.9 Hz (Anechoic)
Passband Ripple1.43 dB (Anechoic)
Subsonic Filter28 Hz High-Pass, 24 dB/Octave - REQUIRED On A Vented Enclosure
Driver Fs33.30 Hz
Driver Qts0.380
Driver Qes / Qms0.400 / 7.970
Driver Vas61.370 Liters / 2.167 Cubic Feet
Driver Sd810.0 Square Centimeters
Driver BL25.10
Driver Re1.8 Ohm
Driver Xmax34mm (One-Way)
Driver Displacement0.21 Cubic Feet (Published by Fi Car Audio)
Driver Sensitivity89.3 dB
Driver Power Handling2500 Watts RMS
Driver Overall Diameter15.625 Inches (Fi Car Audio Spec)
Mounting Depth Required11.000 Inches (Fi Car Audio Spec)
Cutout Diameter14.125 Inches (Fi Car Audio Spec)
Flush Mount Recess16.625 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 Fi Car 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 Power1750-2500 Watts RMS (Fi Car Audio Rated: 2500W RMS)
Carpet FinishPlush Black
Shipping Weight81 lb
ShippingUPS Ground Parcel, Included In The 48 States
Bundle OptionsEnclosure Only (Bring Your Own Fi Car Audio NEO 3.7 15)
Warranty2-Year Limited (Enclosure)
ManufacturedTullahoma, Tennessee, USA
Performance Graphs
Net airspace
3.04
cu ft
Tuning
35.0
Hz · Fb
Half power
30.9
Hz · F3, anechoic
Xmax at
20663
W RMS · 28 Hz subsonic
With NO filter
3905
W RMS · unfiltered
Port
16.7
m/s at the mouth · 2500 W

01Is this driver right for a ported box?

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

EBP = Fs ÷ Qes = 83.2
SEALED 0–50 TRANSITION 50–100 PORTED 100–150 0 50 100 150 EBP 83.2
Fi Car Audio NEO 3.7 15 D2 · EBP 83.2
Between 50 and 100 a driver takes either load, and the choice becomes one of priorities rather than of physics. The Fi Car Audio NEO 3.7 15 D2 reads 83.2. 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

3.04 cu ft net against a 61.4 L Vas, vented at 35.0 Hz.

Fb = 35.0 Hz  ·  F3 = 30.9 Hz  ·  passband ripple 1.43 dB
20 30 50 70 100 150 200 +4 0 −4 −8 −12 −16 −20 −24 −28 −32 FREQUENCY · Hz LEVEL · dB −3 dB Fb 35.0
Fi Car Audio NEO 3.7 15 D2 · Fb 35.0 Hz, F3 30.9 Hz
Anechoic, before any cabin gain, with the 28 Hz subsonic filter already applied. The vent takes over below 35 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 Fi Car Audio NEO 3.7 15 D2 — we do not build a sealed enclosure for it and Fi 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 Fi's published 34.0 mm. The two traces are the same cabinet with the subsonic filter switched on and switched off.

PXmax = 20663 W with a 28 Hz subsonic  ·  3905 W with none  →  the filter is worth 5.3×
20 30 50 70 100 150 200 0 8 16 24 32 40 FREQUENCY · Hz CONE TRAVEL · mm PAST LINEAR TRAVEL · Xmax 34.0 mm 20663 W reaches Xmax here
20663 W · subsonic at 28 Hz, 24 dB/oct3905 W · no subsonic filterXmax 34.0 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 34.0 mm. With a 28 Hz subsonic that takes 20663 W, reached first at 27 Hz. Take the filter away and the same cabinet reaches 34.0 mm on 3905 W — the filter is worth 5.3× 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 3905 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 — Fi rate this one at 2500 W RMS, and that is the number that binds first here: heat stops you before travel does, so treat 2500 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

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.

Handcrafted in USA

Handcrafted in USA

Hand-assembled at our facility in Tullahoma, TN. Every enclosure is inspected before it ships.

Tuned to the Build

Tuned to the Build

Internal volume and port geometry are calculated to spec and CNC-cut to exact dimensions. The box performs the same way every time.

Frequently Asked Questions

Why is this enclosure tuned to 35.0 Hz?

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

Threaded inserts or a kit?

Do I need a subsonic filter?

Would a sealed box be better for me?

How does the front port work?

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

Is the NEO 3.7 15 included?

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