Tempest Nexus - Compact Subwoofer with tunable frequency suitable for car/small room

Tempest Nexus — 5.5" High-Excursion Dual-PR Subwoofer

The Tempest Nexus is a compact, fully 3D-printed subwoofer designed around the Dayton Audio Epique E150HE-44 high-excursion 5.5" driver and two matching Epique E150HE-PR passive radiators.

The enclosure is approximately 9 L net internal volume and uses two passive radiators mounted on opposing side panels, with the E150HE mounted vertically on the top panel. The opposing PR arrangement helps balance mechanical reaction forces while providing substantially more radiating area than a conventional small port.

The result is a surprisingly compact subwoofer capable of reaching well into the sub-30 Hz region when appropriately tuned, while taking advantage of the E150HE's 14.7 mm Xmax and the large excursion capability of the passive radiators.

Corner holders are included as well so the subwoofer can be secured in the boot against moving with elastic bungee cords. Included in the 3mf file. 

Design

• Driver: Dayton Audio Epique E150HE-44

• Passive radiators: 2 × Dayton Audio Epique E150HE-PR

• Enclosure: ~9 L net

• Alignment: Dual passive radiator

• Driver position: Top

• PR position: Opposing side panels

• Nominal driver impedance: 2 Ω using parallel voice-coil wiring

• Amplifier: Stetsom IR 400.1 BASS

• Maximum amplifier output: 400 W RMS @ 2 Ω

• Printed material: Elegoo PETG-CF

• Nozzle: 0.4 mm

• Walls: 6

• Infill: 40% Gyroid

Driver

The two voice coils are wired in parallel, producing a nominal 2 Ω load for the Stetsom amplifier.

Passive Radiators

Two E150HE-PR passive radiators are used, one on each side of the enclosure.

The PRs are mass-loadable, allowing the enclosure tuning to be adjusted after assembly. The final tuning depends on the exact net enclosure volume and the amount of mass installed on each PR.

For this enclosure and this material/wall and infill %,  the tuning frequency of the box was 34Hz with no washers installed.

The PR mass can be changed depending on whether deeper extension or greater output in the 25–40 Hz region is desired.

Enclosure Construction

The enclosure is printed in Elegoo PETG-CF.

The design intentionally uses substantial wall thickness and a high perimeter count rather than relying exclusively on infill for rigidity.

Recommended print configuration:

• 0.4 mm nozzle, 0.6 can be used as well but for a dimensionally accurate outcome, I advise .4

• 6 walls/perimeters

• 40% Gyroid infill

• PETG-CF

• Use your calibrated PETG-CF profile for temperature, flow and pressure advance

• Print the enclosure with good bed adhesion and adequate enclosure ventilation/temperature control as appropriate for PETG-CF

The enclosure is deliberately overbuilt for a 5.5" driver. The goal is to keep cabinet flex and vibration negligible compared with the acoustic output of the driver and PRs.

Hardware / Heat Inserts

All major driver and PR mounting points use M4 hardware.

Two different heat-insert depths are used:

• 4 mm deep inserts: speaker/PR grille mounting

• 6 mm deep inserts: driver and PR mounting holes

The driver/PR mounting inserts are installed from inside the enclosure, rather than from the outside.

Installing the internal inserts

For the driver and PR mounting holes:

1. Place the M4 heat insert on the inside of the enclosure.

2. Insert an M4 screw from the outside and thread it into the insert a couple of turns.

3. Heat the insert with a soldering iron.

4. Slowly push the insert into the printed hole until it reaches the designed depth.

5. Remove the screw after it cools down.

6. Allow the PETG-CF to cool completely.

7. Verify that the M4 threads remain clean and usable.

Using a screw during installation helps keep the insert aligned and prevents molten plastic from filling the threads.

Sealing

The enclosure needs to be airtigh. JB Weld is used where a permanent structural bond/seal is desired.

Wiring

Driver voice coils

The E150HE-44 has two 4 Ω voice coils.

They are wired in parallel:

Amplifier +
     │
     ├──── VC1 +
     │
     └──── VC2 +
Amplifier -
     │
     ├──── VC1 -
     │
     └──── VC2 -

This produces a 2 Ω nominal load.

The physical wiring uses one positive and one negative terminal as the amplifier connection, with the corresponding terminals daisy-chained to the second voice coil.

Internal speaker wiring

Use approximately 14–16 AWG wire inside the enclosure from the feed-through terminals to the driver.

Keep the voice-coil parallel jumpers the same gauge.

Secure excess wire against the enclosure wall with silicone/hot glue so that it cannot move into the PR's excursion path.

Power and ground

• 8 AWG OFC power cable

• 8 AWG OFC ground cable

• Ground connected directly to a chassis negative terminal

• 30 A ANL fuse

• Fuse located approximately 10 cm from the positive battery terminal/junction point - up to 30cm is okay, do not exceed 30cm from your positive pole. 

Use OFC copper cable, not CCA.

The short battery-to-amplifier run makes voltage drop very small, while 8 AWG provides substantial current capacity and fits the amplifier terminals appropriately.

Amplifier → subwoofer

• 12 AWG speaker cable

• Short run between amplifier and subwoofer

12 AWG provides very low cable resistance relative to the 2 Ω load.

Signal / remote

• Approximately 16 AWG for signal/remote wiring

• Use 12v/cigarrette fuse for this if high level detection is not working

• High-level signal wiring should be kept away from high-current power wiring where practical

• Use appropriate strain relief and insulation wherever wiring passes through the enclosure

All crimped connections should use appropriate terminals and adhesive-lined heat-shrink where possible.

Important: High-Level Input

The Stetsom IR 400.1 BASS is being driven from a factory/OEM amplifier's speaker-level output.

Because the OEM amplifier can produce a very high speaker-level voltage, appropriate attenuation may be required before the Stetsom high-level input.

The OEM system in my car used for this project provides approximately 125 W per 8 Ω channel, corresponding to roughly 31.6 V RMS at full output. I had to use resistors to reduce the High-Level input going into the AMP so the signal is not too pre-amplified. You may also use a LOC. 

Do not assume that a factory speaker-level output is equivalent to a normal RCA line-level signal.

Tuning

The enclosure is designed around a passive-radiator alignment rather than a conventional port.

Approximate tuning for the current enclosure is in the following range:

PR mass per PR	Approx. tuning
0 g	~33–34 Hz
+30 g	~31 Hz
+60 g	~29 Hz
+90 g	~26 Hz

These values are estimates and the final measured tuning will depend on the actual net volume, PR tolerances, mounting geometry and installed hardware.

For a good balance of extension and output, +30 g per PR is a recommended starting point.

For maximum low-frequency extension, +90 g per PR can be used, preferably with appropriate DSP/high-pass protection.

DSP / Protection

The E150HE has substantial excursion capability, but the driver is still the limiting component at very low frequencies.

A high-pass filter is recommended when operating the subwoofer at high power, particularly below the PR tuning frequency.

For a ~29 Hz alignment, a high-pass around 24–25 Hz is a sensible starting point.

Actual EQ and filtering should ideally be set using measurements of the completed enclosure.

Why Two PRs?

The two E150HE-PRs provide approximately twice the radiating area of the driver.

The arrangement also places the PRs on opposite sides of the enclosure, helping to balance their mechanical reaction forces.

Compared with a conventional small port, the passive radiators avoid the very high port air velocities and long port lengths that can become problematic when trying to extract high output from a compact, high-excursion 5.5" driver.

---

BOM

Speaker Components

Qty	Component
1	Dayton Audio Epique E150HE-44 5.5" DVC subwoofer
2	Dayton Audio Epique E150HE-PR passive radiators
1	3D-printed main enclosure
1	3D-printed top/lid/driver assembly
2	3D-printed PR grilles/retainers
1	3D-printed driver grille/guard

Fasteners

Qty	Component
24	M4 heat-set inserts, 4 mm depth for grille mounting/corners
12	M4 heat-set inserts, 6 mm depth for driver/PR mounting
4	M4x6/8/10 screws for driver mounting
8	M4x6/8/10 screws for PR mounting
8	M4x10 screws for grille mounting
16	M4x16 screws for corner bungee holders

Adhesives / Sealing

Qty	Component
1	JB Weld
As required	Hot glue / adhesive for securing internal wiring
As required	Acoustic sealing gasket material

Wiring

Qty	Component
~2 m	8 AWG OFC power cable
~2 m	8 AWG OFC ground cable
~2 m	12 AWG speaker cable
As required	14–16 AWG internal speaker wire
As required	18 AWG signal/remote wire
As required	Adhesive-lined heat shrink
As required	Appropriate crimp terminals/ring terminals
As required	Rubber grommets / printed strain reliefs

Amplifier / Power

Qty	Component
1	Stetsom IR 400.1 BASS, 2 Ω mono amplifier
1	30 A ANL fuse
1	ANL fuse holder
As required	Battery/junction-box connections
As required	M4/M5/etc. power terminals appropriate for the amplifier

Optional / Tuning

Qty	Component
1	DSP / suitable high-pass filtering solution
1	Measurement microphone for final tuning

---

Final Result

The Tempest Nexus is designed around a simple principle:

small enclosure + enormous driver excursion + large dual PR area + rigid printed structure.

Rather than trying to make a conventional port work in a very small enclosure, the dual passive-radiator configuration provides the necessary acoustic displacement while keeping the cabinet compact.

The entire enclosure can be manufactured on a consumer 3D printer while retaining substantial mechanical stiffness through thick printed walls, six perimeters and carbon-fiber-reinforced PETG.

Driver: Dayton Audio Epique E150HE-44
PRs: 2 × E150HE-PR
Amplifier: Stetsom IR 400.1 BASS
Nominal load: 2 Ω
Enclosure: ~9 L net
Construction: Elegoo PETG-CF
Recommended starting PR mass: +60 g per PR
Estimated starting Fb: ~29 Hz

Estimated print time for everything is around 3 days with the aforementioned settings. Happy to answer any questions you may have.