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Performance Optimized · Datasheet

Performance Optimized Down Fire Wide Sealed 12" Enclosure Rockford Fosgate T1 Slim · Single 12" Sealed enclosure

Net volume
1.255 cu ft after displacement and the brace
Max mounting depth
3.03 in
External dimensions
41 in W × 6.9375 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
Rockford Fosgate T1 SlimBuy at Audio Intensity
  • Alignment: 1.255 cu ft net. Qtc 1.466, Fc 51.2 Hz, F3 35.9 Hz
  • Down Fire Wide: 41"W x 14"D x 6.9375"H in down fire position, excludes the 1.75" standoffs (installed height 8.6875"). Stands lower than the standard 30 x 15 at 8.25"
  • Height set by: airspace; 3.16" of clearance above the motor
  • Driver: Rockford Fosgate T1S1-12 (1 ohm SVC) or T1S2-12 (2 ohm SVC), 600W RMS, 15mm Xmax, 3.03" mounting depth, 3" voice coil
  • Build: Langboard Elite MDF, V-groove and dado, 1.5" double baffle with flush outer recess, windowed U-brace, 12g OFC side-mounted terminal cup

Spec of record

Technical specifications

SeriesProline X Performance Optimized Down Fire Wide
Compatible DriverRockford Fosgate T1S1-12 (1 ohm SVC) or T1S2-12 (2 ohm SVC), quantity 1. Direct fit
Enclosure TypeSealed, 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 ConfigurationSingle chamber, windowed U-brace, one side-mounted terminal cup
External Width41 in
External Depth14 in
External Height6.9375 in in the down fire position, excludes standoffs
Installed Height8.6875 in including the 1.75 in standoffs
Dimension ReferenceAll external dimensions measured in down fire position
Standard 30 x 15 Version8.25 in tall, 1.24 cu ft net
Internal Volume, Gross1.305 cu ft
Internal Volume, Net1.255 cu ft after displacement and the brace
Height Set ByAirspace; 3.16 in clearance above the motor
AlignmentQtc 1.466, Fc 51.2 Hz, F3 35.9 Hz anechoic
Woofer Opening11.22 in
Mounting Depth Required3.03 in
Driver Displacement0.042 cu ft
Driver Free-Air Qts1.06 (T1S1-12 parameter set; Rockford states the T1S2-12 shares it). Qtc cannot fall below Qts
Voice Coil ConfigurationSingle Voice Coil, Impedance Set By Driver Model
Driver Mounting8/32 Threaded Inserts | Stainless Steel Machine Screws Included
Recommended Power450-600 Watts RMS (Rockford Rated: 600W RMS Continuous)
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 BracingWindowed U-brace, dadoed to the shell
Corner ProfileSquare (Down Fire series standard)
Terminal CupOne Proline X ABS and carbon fiber composite, side mounted, pre-wired 12 gauge OFC
Standoffs1.75 in, included, shipped uninstalled
DampingPolyfill installed as a light wall lining
CarpetPlush black
Bundle OptionsEnclosure only (bring your own T1S1-12 or T1S2-12)
Warranty1 year limited (enclosure)
Built InTullahoma, Tennessee, USA

Modelled response

Performance in this enclosure

Net airspace
1.255
cu ft per chamber
System Qtc
1.47
sealed
Half power
35.9
Hz · F3
Xmax at
636
W RMS · no filter
With 25 Hz subsonic
642
W RMS · +1%
Amplifier
600
W RMS recommended
This enclosure holds 1.255 cu ft net per chamber. In it the Rockford Fosgate T1 Slim 12 (T1S1-12 / T1S2-12) runs a system Qtc of 1.47 with half power at 35.9 Hz, and the cone reaches its 15.0 mm travel limit at 636 W, above the driver’s 600 W thermal rating, so heat stops you before travel does. A 25 Hz subsonic filter adds little here: 642 W against 636 W, 1 percent. The box already resonates at 51 Hz, so its own rolloff has removed most of what the filter would have stopped.

01Is it a sealed driver?

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

EBP = Fs ÷ Qes = 31.6
SEALED 0–50 TRANSITION 50–100 PORTED 100–150 0 50 100 150 T1S1-12 / T1S2-12 31.6
T1S1-12 / T1S2-12 · EBP 31.6
EBP under 50 means a motor that wants a sealed load. The T1 Slim 12 sits at 31.6, inside that band, which is why this is a sealed build rather than a ported one.

02What the box does to it

1.255 cu ft against a 32.4 L Vas.

α = Vas ÷ Vb = 0.91  ·  Fc = Fs√(α+1) = 51 Hz  ·  Qtc = 1.47
20 30 50 70 100 150 200 +6 +0 -6 -12 -18 -24 FREQUENCY · Hz LEVEL · dB −3 dB
T1S1-12 / T1S2-12 · Qtc 1.47, Fc 51 Hz, F3 35.9 Hz
The box lifts resonance from 37.0 Hz free-air to 51 Hz and half power lands at 35.9 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 15.0 mm, and in this alignment a subsonic filter barely moves it.

PXmax = 636 W unfiltered  →  642 W with a 25 Hz subsonic
20 30 50 70 100 150 200 0 4 8 12 16 FREQUENCY · Hz CONE TRAVEL · mm PAST LINEAR TRAVEL · Xmax 15.0 mm 636 W reaches Xmax here
T1S1-12 / T1S2-12 · 636 W, no filterT1S1-12 / T1S2-12 · 642 W with subsonic at 25 Hz, 24 dB/octXmax 15.0 mm one-way
Every trace touches the limit and no further, because each is drawn at the exact power that puts that coil on 15.0 mm. Unfiltered that is 636 W, reached first at 45 Hz. It sits above the 600 W the driver can take thermally, so the voice coil gives up before the suspension does. The dashed traces are the same driver behind a subsonic filter at 25 Hz, 24 dB/oct, and they sit almost on top of the solid ones: 642 W against 636 W. At 51 Hz the filter sits well below resonance, where the sealed alignment has already rolled the cone off at 12 dB/oct, so there is little wasted travel left for it to recover. Set it anyway to keep road rumble out of the cone, but do not size the amplifier around it.
ParamValueUnitNote
Fs37.00Hzfree-air resonance
Qts1.060T1S1-12 / T1S2-12
Vas32.40Lequivalent compliance
Sd560.0cm²effective piston area
Xmax15mmone-way linear travel
Pe600Wcontinuous RMS
SPL83.3dB1 W / 1 m, derived from T/S

Driver parameters as published by loudspeakerdatabase.com, T1S1-12 / T1S2-12. Curves computed against this enclosure’s actual net airspace.

From the shop floor

Installer's take

The T1 Slim 12 is the one to reach for when someone wants 12 inch cone area and has about 3 inches of mounting depth. A full 3 inch four-layer coil and 15mm of one-way Xmax behind an anodized aluminum cone.

Height was solved to the airspace: 6.9375 tall holds 1.255 net, against 1.24 in the standard box, and the motor clears the lid with 3.16 inches to spare. Same air, lower box.

Understand the damping before you buy a box. Qts is 1.06, already above 0.707, so no sealed box of any size makes this driver flat. At 1.255 net it lands at Qtc 1.466 with Fc 51.2 Hz and F3 35.9 Hz: underdamped, with a peak near the corner. That is Rockford's intent.

Wiring is simple because both models are single voice coil. Target 450 to 600 watts RMS.

Measure installed height, not cabinet height: 6.9375 on its own, 8.6875 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 6.9375 inches tall instead of 8.25.

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 T1 Slim 12 enclosure?

Same driver, different shape. The standard cabinet is 30 by 15 by 8.25 inches and holds 1.24 cubic feet net. This cabinet is 41 by 14 by 6.9375 inches and holds 1.255 cubic feet net.

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.

Why is the Qtc above 1.0? Is this enclosure too small?

No. The high Qtc comes from the driver, not the box. The T1 Slim 12 has a free-air Qts of 1.06, and system Qtc can never fall below the driver's Qts regardless of enclosure size, so no sealed volume reaches a textbook 0.707 alignment with it.

At 1.255 cubic feet net this cabinet lands at Qtc 1.466 with Fc 51.2 Hz and F3 35.9 Hz. A larger box would not make it flat, and a smaller one makes it worse.

How do I wire this enclosure?

Straightforward, because both T1 Slim models are single voice coil. The enclosure has one side-mounted Proline X terminal cup pre-wired in 12 gauge OFC, and the impedance your amplifier sees is the model you install: 1 ohm for the T1S1-12, 2 ohms for the T1S2-12.

Rockford rates both at 600 watts RMS. Target 450 to 600 watts RMS and confirm your amplifier is stable at that load.

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

Side mounted. Every Proline X Performance Optimized enclosure uses a side mounted terminal cup, whether standard, wedge or down fire, which keeps the connection accessible with the baffle 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.

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 the cabinet 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 11.22 inch cutout.

A windowed U-brace stiffens the long panels, and polyfill is installed as a light wall lining. Do not add more fill; packing a sealed box makes it act larger and moves the alignment off the 1.255 cubic feet it was built to. Assembled and inspected in Tullahoma, Tennessee.

Is the Rockford Fosgate T1 Slim subwoofer included with this enclosure?

No. This listing is for the enclosure only. Bring your own Rockford Fosgate T1S1-12 or T1S2-12. The cutout and mounting depth are direct fit for either model.

Same series, same size

Other Performance Optimized models