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Performance Optimized · Datasheet

Performance Optimized Down Fire Wide Sealed Dual 12" Enclosure Morel Ultimo PowerSlim PS124D · Dual 12" Sealed enclosure

Net volume
0.807 cu ft after displacement
Max mounting depth
3.386 in
External dimensions
41 in W × 8.75 in in the down fire position H × 14 in D
Front baffle
1.5 in double baffle, outer layer machined as a flush recess
Buy at Audio IntensityFactory-direct, ships from Tullahoma
Morel Ultimo PowerSlim PS124DBuy at Audio Intensity
  • Alignment: 0.807 cu ft net per chamber. Qtc 1.067, Fc 42.7 Hz, F3 32.7 Hz
  • Down Fire Wide: 41"W x 14"D x 8.75"H in down fire position, excludes the 1.75" standoffs (installed height 10.5"). Stands lower than the standard 30 x 15 at 10.75"
  • Height set by: airspace; 4.61" of clearance above the motor
  • Chambers: Two fully separate sealed chambers, 3/4" MDF full divider, one shared side-mounted terminal cup
  • Driver: Pair of Morel PS124D (DVC 4 ohm), 700W RMS each / 1400W combined, 24 Hz Fs, 11mm Xmax each way
  • Build: Langboard Elite MDF, V-groove and dado, 1.5" double baffle with flush outer recess, full divider, 12g OFC side-mounted terminal cup

Spec of record

Technical specifications

SeriesProline X Performance Optimized Down Fire Wide
Compatible DriverMorel Ultimo PowerSlim PS124D (DVC 4 ohm), pair required. Direct fit
Enclosure TypeSealed, dual driver, down fire, floor coupled
Intended FitmentLong, low spaces where height or depth is the limit and 41 in of run is available
Firing DirectionDown firing. Feet ship uninstalled, so front or up firing is also possible
Chamber ConfigurationTwo fully separate chambers, full divider, single shared side-mounted terminal cup
External Width41 in
External Depth14 in
External Height8.75 in in the down fire position, excludes standoffs
Installed Height10.5 in including the 1.75 in standoffs
Dimension ReferenceAll external dimensions measured in down fire position
Standard 30 x 15 Version10.75 in tall, 0.80 cu ft net per chamber
Internal Volume, Gross1.81 cu ft total
Per-Chamber Net Volume0.807 cu ft after displacement
Total Net Volume1.615 cu ft
Height Set ByAirspace; 4.61 in clearance above the motor
Alignment (per chamber)Qtc 1.067, Fc 42.7 Hz, F3 32.7 Hz anechoic
Woofer Opening10.6 in each
Mounting Depth Required3.386 in
Frame Outer Diameter12.008 in
Driver Displacement0.08 cu ft, estimated; Morel publishes no displacement figure, so the 12 inch rule of thumb is used
Driver Fs24 Hz
Driver Qts0.6
Driver Vas49.4 Liters Each
Driver Xmax±11mm
Cone Area452.4 cm² Each / 904.8 cm² Total
Power Handling700 Watts RMS Each / 1400 Watts RMS Combined
Driver ConeFlat Honeycomb Hexatech Aluminium
Driver Voice Coil129.5mm / 5.1" | 4 Layers Carbon | Aluminium Former
Driver MotorDouble Magnet EVC
AwardsEISA Best In-Car Subwoofer 2023-2024 (Ultimo PowerSlim Series)
Driver Mounting8/32 Threaded Inserts | Stainless Steel Machine Screws Included | 2 Sets
Voice Coil ConfigurationDual 4-Ohm Per Driver - Final Impedance Set At The Drivers
Recommended Power Per Driver350-700 Watts RMS (Morel Rated Range)
MaterialLangboard Elite 3/4 in MDF
JoineryV-groove and dado, CNC cut on ShopSabre routers
Front Baffle1.5 in double baffle, outer layer machined as a flush recess
Internal BracingFull-height 3/4 in bonded divider plus perimeter cross-brace
Corner ProfileSquare (Down Fire series standard)
Terminal CupOne Proline X ABS and carbon fiber composite, side mounted, pre-wired 12 gauge OFC to both driver positions
Standoffs1.75 in, included, shipped uninstalled
DampingPolyfill installed as a light wall lining in each chamber
CarpetPlush black
Bundle OptionsEnclosure only (bring your own pair of Morel PS124D)
Warranty1 year limited (enclosure)
Built InTullahoma, Tennessee, USA

Modelled response

Performance in this enclosure

Net airspace
0.807
cu ft per chamber
System Qtc
1.07
sealed
Half power
32.7
Hz · F3
Xmax at
259
W RMS · no filter
With 25 Hz subsonic
282
W RMS · +9%
Amplifier
700
W RMS recommended
This enclosure holds 0.807 cu ft net per chamber. In it the Morel Ultimo PowerSlim PS124D runs a system Qtc of 1.07 with half power at 32.7 Hz, and the cone reaches its 11.0 mm travel limit at 259 W, below the driver’s 700 W thermal rating, so travel is what stops you here, not heat. Run a subsonic filter at 25 Hz and that becomes 282 W — +23 W, or 9 percent more power for the same 11.0 mm of travel.

01Is it a sealed driver?

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

EBP = Fs ÷ Qes = 34.3
SEALED 0–50 TRANSITION 50–100 PORTED 100–150 0 50 100 150 D4 34.3
D4 · EBP 34.3
EBP under 50 means a motor that wants a sealed load. The Ultimo PowerSlim PS124D sits at 34.3, inside that band, which is why this is a sealed build rather than a ported one.

02What the box does to it

0.807 cu ft against a 49.4 L Vas.

α = Vas ÷ Vb = 2.16  ·  Fc = Fs√(α+1) = 43 Hz  ·  Qtc = 1.07
20 30 50 70 100 150 200 +6 +0 -6 -12 -18 -24 FREQUENCY · Hz LEVEL · dB −3 dB
D4 · Qtc 1.07, Fc 43 Hz, F3 32.7 Hz
The box lifts resonance from 24.0 Hz free-air to 43 Hz and half power lands at 32.7 Hz, anechoic, before any cabin gain.

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 11.0 mm — and a bigger one once a subsonic filter stops it wasting travel below the passband.

PXmax = 259 W unfiltered  →  282 W with a 25 Hz subsonic
20 30 50 70 100 150 200 0 4 8 12 FREQUENCY · Hz CONE TRAVEL · mm PAST LINEAR TRAVEL · Xmax 11.0 mm 259 W reaches Xmax here
D4 · 259 W, no filterD4 · 282 W with subsonic at 25 Hz, 24 dB/octXmax 11.0 mm one-way
Every trace touches the limit and no further, because each is drawn at the exact power that puts that coil on 11.0 mm. Unfiltered that is 259 W, reached first at 32 Hz. It sits under the 700 W the driver can take thermally, so the enclosure sets the ceiling, not the voice coil. The dashed traces are the same driver behind a subsonic filter at 25 Hz, 24 dB/oct: stopping the cone wasting travel below the passband lets it take 282 W before hitting the same 11.0 mm. That is 9 percent more amplifier for the price of one filter setting.
ParamValueUnitNote
Fs24.00Hzfree-air resonance
Qts0.600D4
Vas49.40Lequivalent compliance
Sd452.4cm²effective piston area
Xmax11mmone-way linear travel
Pe700Wcontinuous RMS
SPL81.7dB1 W / 1 m, derived from T/S

Driver parameters as published by Morel Ultimo PowerSlim owner's manual, rev 24-12-23. Curves computed against this enclosure’s actual net airspace.

From the shop floor

Installer's take

Two PS124D in a box 8.75 inches tall instead of 10.75. Same 22.7 liters per driver Morel recommends, spread along 41 inches so the pair fits where the standard dual would not.

Height was solved to the airspace: 8.75 tall holds 0.807 net per chamber, against 0.80 in the standard box, and the motor clears the lid with 4.61 inches to spare. Same air, lower box.

Per chamber the alignment is Qtc 1.067 with F3 at 32.7 Hz. The 24 Hz free-air resonance and 49.4 liter Vas are conventional driver numbers in a shallow frame, and that is where the reach comes from.

Separate chambers as always. One side-mounted cup feeds both positions in parallel. Dual 4 ohm coils per driver: set impedance at the drivers, wire both identically, and target 350 to 700 watts RMS per driver.

Measure installed height, not cabinet height: 8.75 on its own, 10.5 with the 1.75 inch feet on. The standard 30 by 15 is still the pick if you do not have 41 inches of run.

Before you order

Questions

Why is this cabinet 41 inches wide instead of 30?

Because it trades length for depth and height. The standard Performance Optimized Down Fire platform is 30 wide by 15 deep; this one is 14 deep, 1 inch shallower, and 41 long. Spreading the airspace along 11 more inches lets the cabinet stand 8.75 inches tall instead of 10.75.

Fourteen inches of depth is the practical minimum, since a 12 inch frame needs about 13 inches of baffle. If your space is long and low rather than deep or tall, this is the shape that fits.

How does this compare to the standard 30 x 15 dual PS124D enclosure?

Same driver, different shape. The standard cabinet is 30 by 15 by 10.75 inches and holds 0.80 cubic feet net per chamber. This cabinet is 41 by 14 by 8.75 inches and holds 0.807 cubic feet net per chamber.

The airspace is effectively the same, so the driver behaves the same way in either. Choose the standard box when length is limited; choose this one when height or depth is the limit and you have 41 inches of run.

What alignment does each driver see in this cabinet?

Each chamber holds 0.807 cubic feet net, Morel's own 22.7 liter recommendation, and each PS124D lands at Qtc 1.067 with Fc at 42.7 Hz and a predicted F3 of 32.7 Hz, computed from Morel's published Fs 24 Hz, Qts 0.6 and Vas 49.4 liters.

Qts is 0.6, so Qtc cannot fall below that in any sealed box. The modest lift near the corner is the driver's intended character.

How is this enclosure wired, and how do I set my final impedance?

One side-mounted Proline X terminal cup with a single pair of posts, pre-wired in 12 gauge OFC to both driver positions in parallel. You do not wire the two chambers separately at the amplifier.

Each PS124D has dual 4 ohm voice coils, so the way you wire each driver's coils sets the load the amplifier sees. Wire both drivers identically. With 1400 watts RMS combined, confirm the load against your amplifier's minimum stable impedance before powering the system.

Where is the terminal cup located on a down fire enclosure?

Side mounted, and there is one cup serving both chambers rather than one per chamber. Every Proline X Performance Optimized enclosure uses a side mounted terminal cup, whether standard, wedge or down fire, which keeps the connection accessible with both baffles facing the floor. The cup is our Proline X ABS and carbon fiber composite unit, recessed, with stainless hardware, copper ring terminals and pre-wired 12 gauge OFC to both driver positions in parallel.

Why are the corners square instead of radiused?

Down Fire cabinets are built with square corners as a series standard. The 3 inch top down corner radius used on other Proline X alignments does not apply here. A down fire box is a low, long platform that sits flat against a floor or cargo deck, and square corners maximize usable internal volume for a given footprint while keeping the cabinet stable on its mounting surface.

How is this enclosure built?

V-groove and dado joinery, CNC cut on ShopSabre routers from Langboard Elite MDF. Every panel joint is a machined interlocking groove that locks the panels before adhesive is applied, which keeps both chambers airtight under sustained pressure cycling. The front baffle is a 1.5 inch double layer, the outer layer machined as a flush recess around the 10.6 inch cutouts.

A full-height bonded 3/4 inch divider separates the chambers and ties the walls together across the 41 inch span, with perimeter cross-bracing and a light polyfill wall lining in each chamber. Do not add more fill; packing a sealed box makes it act larger and moves the alignment. Assembled and inspected in Tullahoma, Tennessee.

Are the Morel PS124D subwoofers included with this enclosure?

No. This listing is for the enclosure only. Bring your own pair of Morel Ultimo PowerSlim PS124D subwoofers. The cutouts and mounting depth are direct fit at both driver positions.

Same series, same size

Other Performance Optimized models