Proline X
Performance Optimized Down Fire Sealed 18" Enclosure | Ampere Audio AA-2.75 18
SKU: PO 18-S DF AA275
- Alignment: 1.80 cu ft net, Qtc 0.67 to 0.69, F3 55.5 Hz on the dual 2 ohm and 57.1 Hz on the dual 4 ohm; height set by the motor, not the airspace
- Driver: Ampere Audio AA-2.75 18 (dual 2 ohm and dual 4 ohm), 1000 W RMS, 19 mm Xmax, 10.12 in mounting depth
- Standoffs: Included, 1.75 in, shipped uninstalled. Installed height near 13.38 in
- Cabinet: 30.00"W x 15.00"D x 11.62"H in down fire position, excludes standoffs, square corners
Financing available. Choose Shop Pay Installments at checkout.
Performance Optimized Down Fire Sealed 18" Enclosure | Ampere Audio AA-2.75 18
Proline X Performance Optimized Down Fire 18" Sealed
Cut and tuned for the Ampere Audio AA-2.75 18
Performance, Performance Optimized, and Micro
Proline X builds three tiers of Down Fire enclosure. The difference is not finish or materials, it is whether the cabinet was designed for a category or for a driver, and how much of the fitting work is already done for you.
| Performance | Performance Optimized | Micro Series | |
|---|---|---|---|
| Fitment | Universal. Accepts any subwoofer that clears the published cutout and mounting depth. | Woofer specific. Cut for one named subwoofer, with cutout, mounting depth, magnet clearance and displacement drawn in CAD from that driver. | Woofer specific. Cut for one named subwoofer. |
| Footprint | Sized to the driver diameter. | A shared 30 by 15 inch platform, with cabinet height as the variable. This build sits on that platform at 11.62 inches tall, the height its 10.12 inch motor needs. | Compact per driver footprint. |
| Front baffle | Single, 3/4 inch. | Double, 1.5 inch, outer layer machined as a flush recess. | Double, 1.5 inch. |
| Driver mounting | Solid flange. You drill your own mounting holes. | Threaded insert kit and stainless machine screws included; Ampere prints no bolt circle, so you mark and drill from the driver. | Threaded inserts, stainless machine screws included. |
| Joinery | V-groove and dado, CNC cut. | V-groove and dado, CNC cut, perimeter cross brace. | Stack fab, dowel reinforced. |
| Published alignment | Modeled Qtc profiles across a range of drivers. No single response curve. | A real predicted Qtc and F3 for that exact driver, calculated from its own Thiele-Small parameters. | Target alignment described in the listing. |
| Carpet | Gray standard, black optional. | Plush black. | Plush black. |
| Warranty | 1 year limited. | 1 year limited. | 2 years. |
Feet ship with every tier, uninstalled on purpose. Mount them where your floor wants them for a down fire install, or leave them off and run the cabinet front firing or up firing. The orientation is yours to choose.
This page is a Performance Optimized enclosure. The airspace, the cutout and the cabinet height all come from the driver's own numbers. A Performance box fits your subwoofer. A Performance Optimized box was built for it.
Built Around the Ampere Audio AA-2.75 18
Nothing about this cabinet is generic. The baffle is cut to 16.69 in, Ampere's published cutout, under the 18.66 in frame. The airspace lands on 1.80 cubic feet net, the volume the cabinet reaches at the height the 10.12 inch motor requires.
The AA-2.75 18 is Ampere's 18 inch in the AA-2.75 series: built on a cast aluminum frame with a 2.75 inch aluminum voice coil, a vented gap and a large aluminum Faraday ring, rated 1000 watts RMS with 19 mm of one-way excursion, 10.12 inches of mounting depth on an 18.66 inch frame. It sits 10.12 inches deep, which matters on a down fire, where the motor rises into the cabinet. Every Thiele-Small figure comes from Ampere's own published table for the AA-2.75 18, and the table holds together: the moving mass and resonance reproduce the published Vas on a cone area in class for an 18 inch driver. Two cells in Ampere's table are mislabeled: the cone area printed is the nominal circle in square inches, not the effective area, and the compliance is printed in mm/N where the value is micrometers per newton. The cone area used here, 1288 square centimeters, is derived from Ampere's own Vas and compliance.
Net Volume, Not Gross
We build this cabinet at 1.80 cubic feet net, out of 2.01 gross after the brace and the driver. Ampere publishes the driver displacement, 0.20 cubic feet, and it is taken out of the net figure. The 10.12 inch mounting depth sets this cabinet's minimum height on the 30 by 15 platform, and the airspace comes with it.
True net, not marketing net. Internal volume is calculated from the machined cavity dimensions and the driver's displacement, not guessed from external dimensions minus wall thickness.
1.80 cubic feet net on Ampere's published figures: the dual 2 ohm reads Qtc 0.669 with resonance at 52.4 Hz and half power at 55.5 Hz, and the dual 4 ohm reads Qtc 0.695 with resonance at 56.1 Hz and half power at 57.1 Hz. One cabinet serves both coils, built to the volume that keeps both closest to maximally flat. That is a slightly over-damped alignment: a gentle, early rolloff and tight transients rather than a flat top.
| Driver | System Qtc | fc | F3 |
|---|---|---|---|
| AA-2.75 18 dual 2 ohm | Qtc 0.669 | 52.4 Hz | 55.5 Hz |
| AA-2.75 18 dual 4 ohm | Qtc 0.695 | 56.1 Hz | 57.1 Hz |
Down Fire Construction
Cut with V-groove and dado joinery on our ShopSabre routers from Langboard Elite 3/4 inch MDF. Every panel joint is a machined interlocking groove that mechanically locks before adhesive is applied, which keeps the cabinet airtight under sustained pressure cycling. Corners are square on Down Fire cabinets.
The cabinet measures 30.00 inches wide by 15.00 inches deep by 11.62 inches tall, measured in the down fire position and excluding standoffs. Plan the space around the installed height rather than the cabinet height: the standoffs hold 1.75 inches under the baffle, so the finished stack sits near 13.38 inches.
Double Baffle, Flush Recess
The front baffle is 1.5 inches, two bonded 3/4 inch sheets, with the outer layer machined as a flush recess so the driver bolts to the inner layer. That recovers 3/4 inch of internal clearance.
Side-Mounted Terminal Cup
Proline X ABS and carbon fiber composite cup with stainless hardware and copper ring terminals, pre-wired in 12 gauge OFC. Side mounted so it stays accessible with the baffle facing the floor.
Standoffs Included
Ampere publishes no front clearance figure for the AA-2.75 18, so this cabinet uses the Proline X standard 1.75 inch standoff, shipped with every enclosure and left uninstalled so you can place them to suit your floor. At that height the floor slot is 0.46 times the cone area, under the 1.0 we aim for. With 19 mm of excursion this cone moves a lot of air at its limit, so for hard use mount taller feet or run the cabinet front firing; at daily levels the slot is not the limit.
Motor Clearance and Orientation
The motor rises off the baffle into the cavity, so on a down fire cabinet the clearance that matters runs to the top panel. The 10.12 inch mounting depth puts the motor 8.62 inches into a 9.38 inch cavity, leaving 0.75 inches above the motor against a 0.75 inch minimum. Height was set by that clearance, not by the airspace: the volume alone would have allowed a lower box.
Ampere does not publish a position on down firing this driver, and this cabinet makes no claim on their behalf. The feet ship uninstalled, so if you would rather run it front firing or up firing, that is a decision you can make at install time without changing anything about the enclosure.
Power, Mounting and Warranty
Ampere rates the AA-2.75 18 at 1000 watts RMS. Ampere sells the AA-2.75 18 as dual 2 ohm and dual 4 ohm: the dual 2 ohm is two 2 ohm coils, 4 ohms in series or 1 ohm in parallel; the dual 4 ohm is two 4 ohm coils, 8 ohms in series or 2 ohms in parallel. A parallel load at or under 1 ohm needs an amplifier rated for it. Confirm the load against your amplifier's minimum stable impedance before powering the system.
Ampere prints no bolt circle for the AA-2.75 18, so the baffle ships undrilled with a threaded insert kit and stainless machine screws: set the driver in the recess, mark its holes, drill, press the inserts and bolt it down. The enclosure carries a 1 year limited warranty. Bring your own AA-2.75 18; the driver is purchased separately.
Cut for the Driver, Not the Catalog
Built one at a time in Tullahoma, Tennessee, with standoffs and a 1 year limited warranty. Questions on fitment or amplifier matching, call 931-563-5151.
| Specification | Value |
|---|---|
| Series | Proline X Performance Optimized Down Fire |
| Compatible Driver | Ampere Audio AA-2.75 18 (dual 2 ohm and dual 4 ohm), quantity 1. Direct fit |
| Configuration | Single 18 inch, sealed down fire |
| Mounting Position | Trunk or cargo floor, baffle facing down on standoffs |
| Firing Direction | Downward. Feet ship uninstalled, so front or up firing is also possible |
| External Width | 30.00 in |
| External Depth | 15.00 in |
| External Height | 11.62 in in the down fire position, excludes standoffs |
| Installed Height | 13.38 in including the 1.75 in standoff |
| Internal Volume, Gross | 2.01 cu ft |
| Internal Volume, Net Acoustic | 1.80 cu ft after the brace and the driver displacement |
| Height Set By | Driver clearance: the 10.12 in motor, not the airspace |
| Driver Mounting Depth | 10.12 in required, 0.75 in clearance above the motor |
| Floor Slot | 0.46 times the cone area at the 1.75 in standoff |
| Alignment, dual 2 ohm | Qtc 0.669, fc 52.4 Hz, F3 55.5 Hz anechoic |
| Alignment, dual 4 ohm | Qtc 0.695, fc 56.1 Hz, F3 57.1 Hz anechoic |
| Woofer Opening | 16.69 in, Ampere's published cutout |
| Frame Outer Diameter | 18.66 in |
| Bolt Circle | Not printed by Ampere; threaded insert kit included |
| Driver Displacement | 0.20 cu ft, Ampere spec |
| dual 2 ohm Fs / Qts / Qes / Qms / Vas | 29.1 Hz / 0.372 / 0.424 / 3.052 / 114.23 L |
| dual 4 ohm Fs / Qts / Qes / Qms / Vas | 31.9 Hz / 0.395 / 0.458 / 2.853 / 106.96 L |
| Driver Sd | 1288 cm2, derived from Ampere's Vas and compliance |
| Xmax | 19 mm one way, Ampere spec |
| Driver Power Handling | 1000 W RMS |
| Wiring Options | Ampere sells the AA-2.75 18 as dual 2 ohm and dual 4 ohm: the dual 2 ohm is two 2 ohm coils, 4 ohms in series or 1 ohm in parallel; the dual 4 ohm is two 4 ohm coils, 8 ohms in series or 2 ohms in parallel. A parallel load at or under 1 ohm needs an amplifier rated for it. |
| Parameter Source | Ampere Audio published T/S and dimension tables, AA-2.75 series page |
| Material | Langboard Elite MDF |
| Construction | CNC cut, V-groove and dado joinery, square corners |
| Panel Thickness | 0.75 in |
| Front Baffle | 1.5 in double baffle, outer layer machined as a flush recess |
| Internal Bracing | Windowed brace, dadoed to the shell |
| Driver Mounting | Threaded insert kit included, NOT pre-installed: Ampere prints no bolt circle |
| Terminal Cups | One Proline X ABS and carbon fiber composite, side mounted, pre wired 12 gauge OFC |
| Standoffs | Included, 1.75 in, shipped uninstalled |
| Damping | Light polyfill wall lining, does not alter acoustic volume |
| Carpet | Plush black |
| Shipping Weight | 41 lb |
| Warranty | 1 Year Limited |
| Built In | Tullahoma, Tennessee |
01Is it a sealed driver?
Efficiency bandwidth product places the motor before anything else is decided.
02What the box does to it
1.80 cu ft against a 114.2 L Vas.
03The 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 19.0 mm — and a bigger one once a subsonic filter stops it wasting travel below the passband.
| Param | Value | Unit | Note |
|---|---|---|---|
| Fs | 29.10 / 31.90 | Hz | free-air resonance |
| Qts | 0.372 / 0.395 | D2 / D4 | |
| Vas | 114.23 / 106.96 | L | equivalent compliance |
| Sd | 1288.3 / 1288.2 | cm² | effective piston area |
| Xmax | 19 | mm | one-way, as Ampere publish it |
| Pe | 1000 | W | continuous RMS |
| SPL | 90.1 | dB | 1 W / 1 m, derived from T/S |
Driver parameters as published by Ampere Audio published T/S table. Curves computed against this enclosure’s actual net airspace.
Built From a Spec Sheet, Not a Sales Sheet
Every Proline X Performance 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.
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 |
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.
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.
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 Performance Series enclosure is not going anywhere.
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.
Handcrafted in USA
Hand-assembled at our facility in Tullahoma, TN. Every enclosure is inspected before it ships.
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.
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