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Proline X PO 15-S DF RSS390HO sealed down fire enclosure, front panel on 1.75 inch feet, 30 by 10.1 inches.
Proline X PO 15-S DF RSS390HO sealed down fire enclosure, end panel with recessed terminal cup, 15 by 10.1 inches.

Performance Optimized · Datasheet

Dayton Audio Reference RSS390HO Box: Sealed 15" Down Fire Enclosure Single 15" Sealed enclosure

Net volume
1.53 cu ft after the brace and the driver displacement
Max mounting depth
7.01 in required, 2.38 in clearance above the motor
External dimensions
30.00 in W × 10.13 in in the down fire position H × 15.00 in D
Front baffle
1.5 in double baffle, outer layer machined as a flush recess
Buy at Audio IntensityFactory-direct, ships from Tullahoma
Dayton Audio Reference RSS390HOBuy at Audio Intensity
  • Alignment: 1.53 cu ft net, Qtc 0.71, F3 47.5 Hz
  • Driver: Dayton Audio Reference RSS390HO (RSS390HO-4 (single 4 ohm)), 800 W RMS, 12 mm Xmax, 7.01 in mounting depth
  • Standoffs: Included, 1.75 in, shipped uninstalled. Installed height near 11.88 in
  • Cabinet: 30.00"W x 15.00"D x 10.13"H in down fire position, excludes standoffs, square corners

Spec of record

Technical specifications

SpecificationValue
SeriesProline X Performance Optimized Down Fire
Compatible DriverDayton Audio Reference RSS390HO (RSS390HO-4 (single 4 ohm)), quantity 1. Direct fit
ConfigurationSingle 15 inch, sealed down fire
Mounting PositionTrunk or cargo floor, baffle facing down on standoffs
Firing DirectionDownward. Feet ship uninstalled, so front or up firing is also possible
External Width30.00 in
External Depth15.00 in
External Height10.13 in in the down fire position, excludes standoffs
Installed Height11.88 in including the 1.75 in standoff
Internal Volume, Gross1.69 cu ft
Internal Volume, Net Acoustic1.53 cu ft after the brace and the driver displacement
Height Set ByAirspace; clearance alone would allow a lower cabinet
Driver Mounting Depth7.01 in required, 2.38 in clearance above the motor
Floor Slot0.60 times the cone area at the 1.75 in standoff
Alignment, RSS390HO-4 (single 4 ohm)Qtc 0.707, fc 47.5 Hz, F3 47.5 Hz anechoic
Woofer Opening14.00 in, cut for Dayton's frame
Frame Outer Diameter15.29 in
Bolt Circle14.49 in, Dayton spec; threaded inserts pre-installed
Driver Displacement0.153 cu ft, estimated; Dayton publishes none
RSS390HO-4 (single 4 ohm) Fs / Qts / Qes / Qms / Vas21.5 Hz / 0.32 / 0.35 / 3.69 / 168 L
Driver Sd830 cm2, Dayton spec
Xmax12 mm, one-way, as Dayton publish it
Driver Power Handling800 W RMS
Wiring OptionsDayton sells the RSS390HO as RSS390HO-4 (single 4 ohm): the RSS390HO-4 (single 4 ohm) is a single 4 ohm coil, a 4 ohm load. A parallel load at or under 1 ohm needs an amplifier rated for it.
Parameter SourceDayton Audio spec sheet
MaterialLangboard Elite MDF
ConstructionCNC cut, V-groove and dado joinery, square corners
Panel Thickness0.75 in
Front Baffle1.5 in double baffle, outer layer machined as a flush recess
Internal BracingWindowed brace, dadoed to the shell
Driver MountingThreaded inserts pre-installed at Dayton's bolt circle; stainless machine screws included
Terminal CupsOne Proline X ABS and carbon fiber composite, side mounted, pre wired 12 gauge OFC
StandoffsIncluded, 1.75 in, shipped uninstalled
DampingLight polyfill wall lining, does not alter acoustic volume
CarpetPlush black
Shipping Weight41 lb
Warranty1 Year Limited
Built InTullahoma, Tennessee

Modelled response

Performance in this enclosure

Net airspace
1.53
cu ft
System Qtc
0.71
sealed
Half power
47.5
Hz · F3
Xmax at
489
W RMS · no filter
With 25 Hz subsonic
649
W RMS · +33%
Amplifier
800
W RMS recommended
This enclosure holds 1.53 cu ft net . In it the Dayton Audio RSS390HO runs a system Qtc of 0.71 with half power at 47.5 Hz, and the cone reaches its 12.0 mm travel limit at 489 W, below the driver’s 800 W thermal rating, so travel is what stops you here, not heat. Run a subsonic filter at 25 Hz and that becomes 649 W — +159 W, or 33 percent more power for the same 12.0 mm of travel.

01Is it a sealed driver?

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

EBP = Fs ÷ Qes = 61.4
SEALED 0–50 TRANSITION 50–100 PORTED 100–150 0 50 100 150 RSS390HO-4 61.4
RSS390HO-4 · EBP 61.4
At 61.4 the RSS390HO sits in the transition band, not the sealed band. That is not a mismatch: a transition motor works in either alignment, and sealed buys a smaller box and a gentler roll-off at the cost of some low-end output. Stage 02 shows what this airspace actually does with it.

02What the box does to it

1.53 cu ft against a 168.0 L Vas.

α = Vas ÷ Vb = 3.88  ·  Fc = Fs√(α+1) = 47 Hz  ·  Qtc = 0.71
20 30 50 70 100 150 200 +6 +0 -6 -12 -18 -24 FREQUENCY · Hz LEVEL · dB −3 dB
RSS390HO-4 · Qtc 0.71, Fc 47 Hz, F3 47.5 Hz
The box lifts resonance from 21.5 Hz free-air to 47 Hz and half power lands at 47.5 Hz, anechoic, before any cabin gain. Parameters are Dayton Audio’s own spec sheet for each coil plotted. Driver displacement is not published and is estimated. Only the coils this listing carries are plotted; the other version falls outside a well-behaved sealed alignment in this cabinet.

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

PXmax = 489 W unfiltered  →  649 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 12.0 mm 489 W reaches Xmax here
RSS390HO-4 · 489 W, no filterRSS390HO-4 · 649 W with subsonic at 25 Hz, 24 dB/octXmax 12.0 mm one-way
Every trace touches the limit and no further, because each is drawn at the exact power that puts that coil on 12.0 mm. Unfiltered that is 489 W, reached first at 20 Hz. It sits under the 800 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 649 W before hitting the same 12.0 mm. That is 33 percent more amplifier for the price of one filter setting.
ParamValueUnitNote
Fs21.50Hzfree-air resonance
Qts0.320RSS390HO-4
Vas168.00Lequivalent compliance
Sd829.6cm²effective piston area
Xmax12mmone-way, as Dayton publish it
Pe800Wcontinuous RMS
SPL88.6dB1 W / 1 m, derived from T/S

Driver parameters as published by Dayton Audio spec sheet. Curves computed against this enclosure’s actual net airspace.

From the shop floor

Installer's take

1.53 cubic feet: Qtc 0.707 on the RSS390HO-4 (single 4 ohm), F3 47.5 Hz.

Measure the installed height, not the cabinet height: 10.13 tall on its own, 11.88 with the standoffs on the 30 by 15 footprint.

Floor slot is 0.60 times the cone area at the 1.75 standoff, under the 1.0 I like. For hard use, taller feet or front firing.

Dayton's spec sheet holds together on every check I run. Displacement is the one figure they do not give, so it is estimated.

Inserts are pressed at Dayton's bolt circle, so the driver bolts straight in. Sealed, so leave the polyfill as it is and run it at 800 watts or under per driver.

Before you order

Questions

Does this fit the Dayton Audio Reference RSS390HO, and will any other 15 inch fit?

The Reference RSS390HO, yes, in the RSS390HO-4 (single 4 ohm) version. The baffle is cut to 14.00 in for Dayton's 15.29 in frame. The 7.01 inch motor clears the cabinet with 2.38 inch to spare.

Any other 15, no. The airspace is engineered around the Reference RSS390HO's own Qts and Vas, and a different woofer that happened to drop into the hole would not see the alignment printed on this page.

Why 1.53 cubic feet, and what alignment does it target?

1.53 cubic feet net on Dayton's published figures: the RSS390HO-4 (single 4 ohm) reads Qtc 0.707 with resonance at 47.5 Hz and half power at 47.5 Hz. That is spread either side of maximally flat: the lower-Q coil a little drier, the higher-Q coil a little punchier.

Cabinet gain in a vehicle lifts the bottom end further, so in the car this reads deeper than the anechoic figures.

What amplifier power should I run, and how should I wire it?

Dayton rates the Reference RSS390HO at 800 watts RMS, so target 560 to 800 watts RMS at the final load.

Dayton sells the RSS390HO as RSS390HO-4 (single 4 ohm): the RSS390HO-4 (single 4 ohm) is a single 4 ohm coil, a 4 ohm load. A parallel load at or under 1 ohm needs an amplifier rated for it. Confirm your amplifier's minimum stable impedance first.

How tall is this once the standoffs are on?

The cabinet is 10.13 inches tall measured in the down fire position, and that figure excludes the standoffs. The standoffs hold 1.75 inches under the baffle, so plan your space around a finished stack of roughly 11.88 inches.

The footprint is the standard Performance Optimized down fire platform, 30.00 inches wide by 15.00 deep. Height is the only dimension solved to the driver.

Why is the front baffle double-layered?

The baffle is two bonded 3/4 inch sheets, 1.5 inches through. A single 3/4 inch panel flexes under the pressure a 15 inch woofer puts on it at 800 watts, which smears output and works the driver loose over time; the second layer stiffens the face and gives the mounting hardware twice the material to bite.

The outer layer is machined as a flush recess to Dayton's 15.29 inch frame, so the driver bolts to the inner layer.

What is the expected low-frequency extension?

Anechoic F3 is 47.5 Hz. Below Qtc 0.707 the rolloff is gentle and F3 sits above fc, which is what an over-damped sealed box does.

Those figures exclude cabin gain. In a car the cabin's transfer function adds real output below 50 Hz, so in-vehicle response runs deeper than the numbers above.

Do I need to add polyfill or damping?

No. Polyfill is already installed as a light wall lining to control internal reflections, and the quantity is chosen so it does not change the acoustic volume.

Do not add more. Packing a sealed box with fill makes it behave as though it were larger, which walks the alignment away from the 1.53 cubic feet this cabinet was built to.

Is the driver included, and are the threaded inserts installed?

No driver. This is an enclosure only. You receive the cabinet finished in plush black carpet, one side-mounted pre-wired terminal cup, the polyfill lining already in place, the standoffs, and stainless machine screws, with the threaded inserts already pressed.

The inserts are pressed at the shop on Dayton's published bolt circle for the Reference RSS390HO, so the driver bolts straight in. The Dayton Audio Reference RSS390HO is purchased separately, and the cabinet is cut direct fit to it, not a general purpose 15 inch box.

Same series, same size

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