Pro 15-P GZHW38 placeholder
Pro 15-P GZHW38 placeholder

Proline X

Professional Series Ported 15" Enclosure | Ground Zero GZHW 38

SKU: Pro 15-P GZHW38

QUICK SPECS
  • Alignment: 3.09 cu ft net vented at 34.0 Hz. F3 28.0 Hz anechoic, 2.71 dB passband ripple
  • Driver: Ground Zero GZHW 38 D1 or D2, 2000 W RMS, 22.5 mm Xmax, 43.40 Hz Fs
  • Build: Front-firing standard box, 2.25" three-layer baffle with the woofer flush-mounted in the outer layer, Ground Zero 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 2400 W
  • Cabinet: 36.00" W x 18.00" H x 18.00" D, 74 lb, threaded insert kit included
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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.
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Advanced Terminal Cup Built in-house. ABS/Carbon Fiber. Stainless steel hardware. Copper ring terminals.
$ 651.99
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Pro 15-P GZHW38 placeholder

Professional Series Ported 15" Enclosure | Ground Zero GZHW 38

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 3.09 cu ft
Tuning Frequency 34.0 Hz
Port Area 66.0 Square Inches
Weight 74 lbs
INSTALLER'S TAKE

I built this box on Ground Zero's own published Fs, Qts, and Vas for the GZHW 38: 43.40 Hz, 0.7700, and 22.19 litres, backed by a 0.8400 Qes and a 10.0200 Qms. It lands at 2.565 cubic feet net, vented at 34.0 Hz, and the model gives back F3 at 28.2 Hz with 2.24 dB of ripple, the flattest curve of the four Ground Zero boxes I built this round. Ground Zero publishes no vented number of their own for this driver, so there is nothing to check the curve against.

Ground Zero publishes no cone area for this driver. The 855.3 square centimetre Sd behind this alignment, the tuning, the port sizing, and the velocity math, is estimated rather than measured or stated by Ground Zero. Ground Zero also publishes no driver displacement; the 0.223 cubic foot figure I used is estimated too, and it only touches the gross volume number, not the tuning or the port.

Ground Zero calls its excursion spec Max. Excursion and never says what it is measured to. For the GZHW 38 the manual gives a peak-to-peak figure, and I halved it to the 22.5 mm one-way number this box is built around. That halving is the reason this model gets a cabinet at all; most of the rest of the Ground Zero line states no basis for its excursion figure and stays off the bench.

Ground Zero publishes no mounting hole locations for this driver, so I am not pressing the threaded inserts before it ships. The insert kit rides loose in the box; set them at install once the driver is in hand.

The GZHW 38 ships D1 or D2. Wire the D1's two coils in series for 2 ohms or parallel for 0.5 ohm; wire the D2's two coils in series for 4 ohms or parallel for 1 ohm. A sub-1-ohm parallel load needs an amplifier built for it.

Ground Zero publishes no mounting hole locations for the GZHW 38, 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.

The Performance Optimized wedge is the smaller and cheaper box, and I try it first for every driver. I could not make its port keep up with the GZHW 38: the calmest port that fits that envelope goes noisy at about 1024 watts, under what this coil is rated to take, so I did not sell you that box.

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

A ported fifteen-inch Professional box built to the GZHW 38's own Fs, Qts, and Vas, with cone area and displacement estimated because Ground Zero never publishes either

3.09 cu ft net Tuned 34.0 Hz F3 28.0 Hz 2.25" three-layer baffle Cut for the GZHW 38 Built in Tennessee
3.09cu ft net
34.0Hz tuning
28.0Hz F3 anechoic
66.0sq in port area

Why this driver is vented at 34.0 Hz

The GZHW 38 15 inch is a 43.40 Hz motor with a 0.7700 Qts and 22.19 litres of Vas, and this cabinet gives it 2.565 cubic feet net, vented at 34.0 Hz through a 49.5 square inch port. The 36.0 by 18.0 by 15.0 inch enclosure gets F3 down to 28.2 Hz with 2.24 dB of passband ripple, the flattest response of the four Ground Zero Professional builds. Ground Zero publishes no vented recommendation of its own for this driver, so the alignment stands on the published Fs, Qts, and Vas alone.

Threaded insert kit ships with this box. Ground Zero does not publish the mounting hole locations for the GZHW 38, so we cannot install the threaded inserts before it ships. The threaded insert kit comes in the box instead: 8 to 12 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; one kit serves one woofer.

A 0.7700 Qts on 22.19 litres of Vas, backed by a 0.8400 Qes and a 10.0200 Qms, is a compliant motor that wants a large box and a low vent, and 34.0 Hz brings F3 to 28.2 Hz on 2.24 dB of ripple. At the driver's rated 1500 W the port runs 16.3 metres per second through the mouth at 1800 W, the reference point the velocity check is measured against. The 855.3 square centimetre Sd behind this solve is not a Ground Zero figure: Ground Zero publishes no cone area for the GZHW 38, so the number is estimated.

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.

Ground Zero logo acrylic

A glossy black acrylic insert with the Ground Zero 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 2400 W

The 66.0 square inch slot beside the woofer is sized so the channel runs 22.3 metres per second and the mouth 16.8 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 10.25 inches along its wall and turns once along the back wall for another 19.44 inches, which is why a 34.0 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 GZHW 38 did not clear the port gate there. The calmest wedge port that fits that envelope is 32.0 square inches at 26.0 by 11.25 by 17.98 inches, and its mouth runs 23.8 metres per second at 2000 W against the 17 metres per second line where a port starts to chuff. That port would stay clean to about 1024 W. The slot on this box reaches 66.0 square inches and holds the mouth at 16.8 metres per second at 2400 W.

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 74 lb parcel and checkout adds nothing. The Performance Optimized 15 inch ported wedge is $499.99. The $152 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 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. This is our single-fifteen Professional envelope built around the GZHW 38's own frame and motor depth, a 15.350 inch frame over a 14.170 inch cutout and 9.090 inches of mounting depth. Ground Zero lists this driver twice, as the GZHW 38 and the GZHW 38XSPL, and they are one unit; this enclosure is built for it under either name. It ships as a parcel.

Ground Zero publishes no cone area for the GZHW 38: the 855.3 square centimetre Sd behind this alignment, its tuning, port sizing, and velocity math, is estimated, not measured or stated by Ground Zero. Ground Zero also publishes no driver displacement; the 0.223 cubic foot figure used here is estimated too, and it affects only the gross volume figure, not the tuning or port math. Ground Zero publishes no mounting hole locations for the GZHW 38, so the threaded insert kit ships loose in the box rather than pressed into the baffle before the cabinet ships. Ground Zero labels its excursion figure Max. Excursion without stating a basis; the manual gives a peak-to-peak number for this model, halved here to the 22.5 mm one-way figure used in the math, which is why this model builds while other Ground Zero models with no stated basis do not. Ground Zero publishes the same Fs, Qts, Qes, Qms, Vas, Sd, and Xmax for the GZHW 38 and the GZHW 38XSPL, so this cabinet and its sibling XSPL build share identical airspace and tuning. Ground Zero does not publish the mounting hole locations for the GZHW 38, so we cannot install the threaded inserts before it ships. The threaded insert kit comes in the box instead: 8 to 12 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; one kit serves one woofer.

The numbers to respect

Set a 27 Hz subsonic filter, 24 dB per octave. Below tuning the vent stops loading the cone; with the filter in place the cone reaches 11.3 mm of its 22.5 mm at 2400 W.

Enclosure Specifications
SeriesProline X Professional
Driver-Specific FitmentGround Zero GZHW 38 D1 or D2 (D1)
Enclosure TypePorted | Front-Firing Standard Box
External Width36.00 Inches
External Height18.00 Inches
External Depth18.00 Inches
Internal Volume (Gross)4.94 Cubic Feet
Internal Volume (Net After Displacement)3.09 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, 37.44 Inches Of Path
Port Area66.0 Square Inches
Port Tuning (Fb)34.0 Hz
Port Mouth1/2 In Roundover On All Four Edges, 87.5 Square Inches At The Face
Port Air Velocity22.3 m/s In The Channel, 16.8 m/s At The Mouth, At 2400 W (17.0 m/s Chuff Threshold)
Design Power Basis2400 W RMS (1.2 x The Driver Rating) For Port Velocity And Excursion
Predicted F328.0 Hz (Anechoic)
Passband Ripple2.71 dB (Anechoic)
Subsonic Filter27 Hz High-Pass, 24 dB/Octave - REQUIRED On A Vented Enclosure
Driver Fs43.40 Hz
Driver Qts0.770
Driver Qes / Qms0.840 / 10.020
Driver Vas22.190 Liters / 0.784 Cubic Feet
Driver Sd855.3 Square Centimeters
Driver BL19.28
Driver Re1.9 Ohm
Driver Xmax22mm (One-Way)
Driver Displacement0.22 Cubic Feet (Published by Ground Zero)
Driver Sensitivity86.0 dB
Driver Power Handling2000 Watts RMS
Driver Overall Diameter15.350 Inches (Ground Zero Spec)
Mounting Depth Required9.090 Inches (Ground Zero Spec)
Cutout Diameter14.170 Inches (Ground Zero 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 Ground Zero 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 ConfigurationD1
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 Power1400-2000 Watts RMS (Ground Zero Rated: 2000W RMS)
Carpet FinishPlush Black
Weight74 lb
ShippingUPS Ground Parcel, Included In The 48 States
Bundle OptionsEnclosure Only (Bring Your Own Ground Zero GZHW 38)
Warranty2-Year Limited (Enclosure)
ManufacturedTullahoma, Tennessee, USA
Performance Graphs
Net airspace
3.09
cu ft
Tuning
34.0
Hz · Fb
Half power
28.0
Hz · F3, anechoic
Xmax at
9529
W RMS · 27 Hz subsonic
With NO filter
4183
W RMS · unfiltered
Port
16.8
m/s at the mouth · 2400 W

01Is this driver right for a ported box?

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

EBP = Fs ÷ Qes = 51.7
SEALED 0–50 TRANSITION 50–100 PORTED 100–150 0 50 100 150 EBP 51.7
Ground Zero GZHW 38 / GZHW 38XSPL D1 · EBP 51.7
Between 50 and 100 a driver takes either load, and the choice becomes one of priorities rather than of physics. The Ground Zero GZHW 38 / GZHW 38XSPL D1 reads 51.7. 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

3.09 cu ft net against a 22.2 L Vas, vented at 34.0 Hz.

Fb = 34.0 Hz  ·  F3 = 28.0 Hz  ·  passband ripple 2.71 dB
20 30 50 70 100 150 200 +16 +12 +8 +4 0 −4 −8 −12 −16 −20 −24 −28 FREQUENCY · Hz LEVEL · dB −3 dB Fb 34.0
Ground Zero GZHW 38 / GZHW 38XSPL D1 · Fb 34.0 Hz, F3 28.0 Hz
Anechoic, before any cabin gain, with the 27 Hz subsonic filter already applied. The vent takes over below 34 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 Ground Zero GZHW 38 / GZHW 38XSPL D1 — we do not build a sealed enclosure for it and Ground Zero 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 Ground Zero's published 22.5 mm. The two traces are the same cabinet with the subsonic filter switched on and switched off.

PXmax = 9529 W with a 27 Hz subsonic  ·  4183 W with none  →  the filter is worth 2.3×
20 30 50 70 100 150 200 0 8 16 24 FREQUENCY · Hz CONE TRAVEL · mm PAST LINEAR TRAVEL · Xmax 22.5 mm 9529 W reaches Xmax here
9529 W · subsonic at 27 Hz, 24 dB/oct4183 W · no subsonic filterXmax 22.5 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 22.5 mm. With a 27 Hz subsonic that takes 9529 W, reached first at 27 Hz. Take the filter away and the same cabinet reaches 22.5 mm on 4183 W — the filter is worth 2.3× 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 4183 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 — Ground Zero rate this one at 2000 W RMS, and that is the number that binds first here: heat stops you before travel does, so treat 2000 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
Hydrogen sits above Radioactive in the range, built for competition and for everyday music both, and the cast aluminium basket is there to raise the SPL the driver can reach. Ground Zero lists this driver under two names, the GZHW 38 and the GZHW 38XSPL, and the only published difference between them is the dust cap. Note also that their web pages print 1500 W RMS while both manuals and the current catalogue print 2000; this enclosure is designed against the 2000. This enclosure is cut for 9.09 in, 231 mm of mounting depth and a 14.17 in, 360 mm cutout, taken from Ground Zero's published figures rather than measured off a sample. Where a rating below carries no reference condition, that is because the maker does not state one, and it is left as they print it.
DriverGround Zero GZHW 38 / GZHW 38XSPL
Coil OptionsTwo 1 Ohm Coils on the D1, Two 2 Ohm on the D2
Voice Coil Diameter75 mm, 3 in, High Temperature Copper
ConeFiber Reinforced Paper
Dust CapCarbon on the GZHW 38, IMPP With A 3D Structure Logo on the GZHW 38XSPL
SurroundHigh Roll U Surround
SpiderTwo Layer Polycot
Lead WiresPush Terminals
BasketSolid Aluminum Cast
MotorTriple Stack
Power, RMS2000 W
Power Handling, SPL3500 W
Sensitivity86 dB (D1), 87 dB (D2), Efficiency, reference condition not stated by Ground Zero
Mounting Depth9.09 in, 231 mm
Cutout Diameter14.17 in, 360 mm
Frame Outside Diameter15.35 in, 390 mm
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 34.0 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 GZHW 38 included?

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