Performance Optimized · Datasheet

Performance Optimized Wedge Ported 8" Enclosure | Rockford Fosgate P2D2-8 Single 8" Ported enclosure

Net volume
0.92 Cubic Feet
Tuning
35.5 Hz
Max mounting depth
4.760 Inches (Rockford Fosgate Spec)
Cutout
7.130 Inches (Rockford Fosgate Spec)
External dimensions
29.00 Inches W × 11.75 Inches H × 8.62 Inches / 12.90 Inches D
Front baffle
Vertical Baffle - Driver Fires Rearward Into The Trunk
Buy at Audio Intensity
  • Alignment: 0.92 cu ft net vented at 35.5 Hz. F3 30.3 Hz anechoic, 2.40 dB passband ripple
  • Driver: Rockford Fosgate P2D2-8 D2, 250 W RMS, 7.8 mm Xmax, 39.60 Hz Fs
  • Build: Rear-firing wedge, 20 degree rear rake, V-groove and dado joinery, triangular side-exit slot port with a 1/2" rounded mouth, double 1.5" baffle, side-mounted terminal cup
  • Cabinet: 29.00" W x 11.75" H x 12.90" D at base tapering to 8.62" D at top, 13.0 sq in port, ships dry

Technical specifications

SeriesProline X Performance Optimized Wedge
Driver-Specific FitmentRockford Fosgate P2D2-8 D2 (Dual 2 Ohm)
Enclosure TypePorted | Rear-Firing Trunk Wedge
Baffle ConfigurationVertical Baffle - Driver Fires Rearward Into The Trunk
Wedge Angle20 Degrees On The Rear (Seat-Side) Panel
External Width29.00 Inches
External Height11.75 Inches
Top Depth8.62 Inches
Base Depth12.90 Inches
Internal Volume (Gross)1.22 Cubic Feet
Internal Volume (Net After Displacement)0.92 Cubic Feet
Port TypeTriangular Slot | Bottom-Rear Corner | Straight, No Bend | Side Exit
Port GeometryIsosceles, 5.25 Inch Legs, 13.0 Square Inches, 23.92 Inches Long, Side Mouth
Port Tuning (Fb)35.5 Hz
Port MouthTriangle Through Side A, 1/2 In Roundover On All Three Edges, 22.5 Square Inches At The Face
Port ThroatOpen Far End, 3.33 In Gap To Side B, 3/8 In Roundover On The Panel End
Port Air Velocity20.3 m/s In The Channel, 11.6 m/s At The Flared Mouth (17.0 m/s Chuff Threshold)
Predicted F330.3 Hz (Anechoic)
Passband Ripple2.40 dB (Anechoic)
Subsonic Filter28 Hz High-Pass, 24 dB/Octave - REQUIRED On A Vented Enclosure
Driver Fs39.60 Hz
Driver Qts0.460
Driver Qes / Qms0.510 / 5.400
Driver Vas9.900 Liters / 0.350 Cubic Feet
Driver Sd221.0 Square Centimeters
Driver Re3.4 Ohm
Driver Xmax8mm (One-Way)
Driver Displacement0.04 Cubic Feet (Published by Rockford Fosgate)
Driver Sensitivity83.0 dB
Driver Power Handling250 Watts RMS
Driver Overall Diameter8.720 Inches (Rockford Fosgate Spec)
Mounting Depth Required4.760 Inches (Rockford Fosgate Spec)
Cutout Diameter7.130 Inches (Rockford Fosgate Spec)
MaterialLangboard Elite 3/4" MDF
ConstructionShopSabre CNC / Two Windowed C Braces At The Third Points, Seated On The Port Panel
JoineryV-Groove and Dado (CNC-Cut)
Front Baffle ConstructionDouble-Layer 1.5" MDF | Cosmetic Front Layer Routed For The Acrylic Insert
Mounting HardwareThreaded Inserts At Every Mounting Location | Stainless Steel Machine Screws Included
Voice Coil ConfigurationDual 2 Ohm
Terminal CupProline X ABS/Carbon Fiber Composite | Side Mounted, Opposite The Port | 12g OFC Pre-Wired
DampingNone - Ships Dry. Polyfill Detunes A Ported Enclosure
Recommended Power175-250 Watts RMS (Rockford Fosgate Rated: 250W RMS)
Carpet FinishPlush Black
Weight41 lb
Bundle OptionsEnclosure Only (Bring Your Own Rockford Fosgate P2D2-8)
Warranty1-Year Limited (Enclosure)
ManufacturedTullahoma, Tennessee, USA

Performance in this enclosure

Net airspace
0.92
cu ft
Tuning
35.5
Hz · Fb
Half power
30.3
Hz · F3, anechoic
Xmax at
309
W RMS · 28 Hz subsonic
With NO filter
83
W RMS · unfiltered
Port
11.6
m/s at the mouth

01Is this driver right for a ported box?

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

EBP = Fs ÷ Qes = 77.6
SEALED 0–50 TRANSITION 50–100 PORTED 100–150 0 50 100 150 EBP 77.6
Rockford Fosgate P2D2-8 · EBP 77.6
Between 50 and 100 a driver takes either load, and the choice becomes one of priorities rather than of physics. The Rockford Fosgate P2D2-8 reads 77.6. 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

0.92 cu ft net against a 9.9 L Vas, vented at 35.5 Hz.

Fb = 35.5 Hz  ·  F3 = 30.3 Hz  ·  passband ripple 2.40 dB
20 30 50 70 100 150 200 +6 +0 −6 −12 −18 −24 FREQUENCY · Hz LEVEL · dB −3 dB Fb 35.5
Rockford Fosgate P2D2-8 · Fb 35.5 Hz, F3 30.3 Hz
Anechoic, before any cabin gain, with the 28 Hz subsonic filter already applied. The vent takes over below 36 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, 0.92 cu ft net vented at 35.5 Hz, against Rockford Fosgate's recommended sealed box, 0.23 cu ft.

Ported Fb 35.5 Hz  ·  the 0.23 cu ft sealed box runs Qtc 0.73, Fc 63 Hz
20 30 50 70 100 150 200 +6 +0 −6 −12 −18 −24 FREQUENCY · Hz LEVEL · dB +11.8 dB at 35 Hz
Ported · this cabinet, 0.92 cu ft, Fb 35.5 HzRockford Fosgate's recommended sealed, 0.23 cu ft net, Qtc 0.73
Shaded blue is where the ported alignment is louder for the same power, orange where the sealed one is. The sealed curve is Rockford Fosgate's recommended sealed box, 0.23 cu ft, 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 11.8 dB at its widest and 7.9 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 7.0 dB spread, the 0.23 cu ft sealed box 3.4 dB
20 30 50 70 100 150 200 +6 +0 −6 −12 −18 −24 FREQUENCY · Hz LEVEL · dB +11.8 dB at 35 Hz
Ported, in-car · 7.0 dB spreadRockford Fosgate's recommended sealed, 0.23 cu ft net, in-car · 3.4 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 7.0 dB of spread against 3.4 dB for Rockford Fosgate's recommended sealed box, 0.23 cu ft. The sealed curve is flatter on paper; the ported one trades that for output. The two alignments converge at the bottom of the band rather than crossing cleanly, so there is no meaningful subsonic advantage either way here. 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 the cone exactly on Rockford Fosgate's published 7.8 mm. The two traces are the same cabinet with the subsonic filter switched on and switched off.

PXmax = 309 W with a 28 Hz subsonic  ·  83 W with none  →  the filter is worth 3.7×
20 30 50 70 100 150 200 0 4 8 FREQUENCY · Hz CONE TRAVEL · mm PAST LINEAR TRAVEL · Xmax 7.8 mm 309 W reaches Xmax here
309 W · subsonic at 28 Hz, 24 dB/oct83 W · no subsonic filterXmax 7.8 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 7.8 mm. With a 28 Hz subsonic that takes 309 W, reached first at 28 Hz. Take the filter away and the same cabinet reaches 7.8 mm on 83 W — the filter is worth 3.7× 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 83 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 — Rockford Fosgate rate this one at 250 W RMS, and that is the number that binds first here: heat stops you before travel does, so treat 250 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.

Installer's take

Rockford's Punch P2 eight is a 39.6 Hz motor with a 0.46 Qts, and vented at 35.5 Hz in 0.92 cubic feet it reaches 30.3 Hz anechoic on 2.40 dB of ripple, a long way down for an eight. The cost is in the car: 7.22 dB of spread across 25 to 60 Hz, because a 40 Hz motor has rolled off well before cabin gain arrives and the port is carrying the bottom octave alone. Rockford's own sealed recommendation is 0.23 cubic feet, a quarter of this box; they are pitching a very different sound.

Excursion is the number I watch on this one. 7.8 mm of one-way travel and the cone uses 7.0 of it at 250 watts with the subsonic filter set, 90 percent of what it has. Set the filter, set the gain with a meter, and do not treat 250 watts as a starting point. The channel runs 20.3 metres per second against a 20.9 limit.

Questions

Why is this enclosure tuned to 35.5 Hz?

35.5 Hz puts the anechoic F3 at 30.3 Hz on 2.40 dB of ripple, a long reach for an eight, and the reach is what costs it in the car: 7.22 dB of spread across 25 to 60 Hz, because a 39.6 Hz motor has rolled off well before cabin gain arrives. Rockford's own sealed recommendation for this driver is 0.23 cubic feet; this is a different animal. The port takes 23.92 of the 24.88 inches available and runs at 20.3 metres per second in the channel against a 20.9 limit, 11.6 at the rounded mouth. Tuning is chosen for in-car response rather than an anechoic curve: a vehicle adds roughly 12 dB per octave below about 45 Hz. In this cabinet that lands at 7.0 dB of in-car spread across 25 to 60 Hz.

Why the 20 degree wedge, and why rear-firing?

The raked face is the seat side. A factory rear seat back leans about 20 degrees off vertical, so the cabinet sits flat against it and uses floor a square box wastes. The baffle stays vertical and fires rearward into the trunk, which acts as the acoustic extension into the cabin. This one is 12.90 inches deep at the base and 8.62 at the top, 29.00 wide and 12 tall.

Do I need a subsonic filter?

Yes, at 28 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 Rockford Fosgate P2D2-8 at 90 percent of its usable travel at full rated power; without it there is no meaningful number to quote.

How much power can I run, and at what impedance?

Rockford Fosgate rate the P2D2-8 at 250 W RMS and that is the thermal ceiling. The Performance Graphs tab shows the mechanical limit, the power at which the cone reaches the end of its travel in this cabinet: here the cone sits at 90 percent of usable travel at the rating, so heat is what stops you, not travel. A D2 coil is 4 ohms in series or 1 ohm in parallel; run series unless the amplifier is rated for 1 ohm. A D4 is 8 series or 2 parallel.

Would a sealed box be better for me?

The two alignments converge at the bottom of the band on this driver rather than crossing cleanly, so there is no meaningful subsonic advantage either way. Above 25 Hz the vent is the louder of the two. The Performance Graphs tab plots this cabinet against Rockford Fosgate's recommended sealed box, 0.23 cu ft.

How does the side port work?

It is a triangular slot in the bottom-rear corner: the floor and the raked back wall are two sides, one bevelled panel is the third. It runs across the cabinet, opens into the box through a 3.33 inch gap at the far end and exits through the side panel as the same triangle. Straight, no bend: 23.92 inches of path and 13.0 square inches of channel running at 20.3 metres per second, 53 percent of its turbulence limit. The three mouth edges are rounded over at 1/2 inch, so the opening at the face is 22.5 square inches and the air leaves it at 11.6 metres per second against the 17.0 threshold where a slot port starts to chuff; the panel's throat end is rounded at 3/8 inch for the same reason. The terminal cup is on the other side.

Does this enclosure ship with polyfill?

No, and do not add any. Every sealed Proline X enclosure ships with polyfill; a ported one must not, because damping changes the effective volume the port is tuned against. The port here is cut to 23.92 inches for 35.5 Hz. Stuff it and you move the tuning without shortening the port.

Is the P2D2-8 included?

No. This is an enclosure only, cut for the Rockford Fosgate P2D2-8 specifically: the 7.130 inch cutout, the 4.760 inch mounting depth allowance and the 0.92 cubic foot alignment all come from Rockford Fosgate's published parameters. It fits both coil versions; the alignment published here is the D2. Bring your own driver.

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