Polk Audio EX8 (EX Series II)
8″ subwoofer · 4 Ω · 125 W RMS
The Polk Audio EX8 (EX Series II) is a shallow 8″ sub (3 3/8″ mounting depth): it fits behind a truck seat or in a slim box. With Qts 0.54 and EBP 78 it works both sealed and ported: sealed is tighter and smaller, ported is deeper and louder. Modest excursion (Xmax 0.18″) — for clean sound at moderate levels, not for SPL competitions.
| Source | web.archive.org · manufacturer data |
|---|---|
| Checked against source | October 2026 |
| Thiele/Small parameters | not in the spec sheet: Sd — typical value for the size used |
| Mounting dimensions | 2 of 4 — missing: frame outer diameter, magnet diameter; the designer will use an estimate |
Recommended box
For a sedan, one sub, 125 W. It’s the same math as the designer’s step-by-step mode, where you can fit the box to your space, vehicle and amp and get plans, a cut sheet and DXF.
Sealed
smaller, tighter| Bass character (Qtc) | Tight and punchy · 0.80 |
|---|---|
| Fc | 66 Hz |
| F3 (−3 dB, no cabin gain) | 62 Hz |
| Example box (outside) | 10 1/4″ × 10 1/4″ × 14 3/4″ |
Ported
deeper, louder| Tuning (Fb) | 41 Hz |
|---|---|
| Port | slot 1 15/16 × 14 5/16″, 80 5/16″ long |
| Port velocity at 125 W | 14 ft/s |
| F3 (−3 dB, no cabin gain) | 46 Hz |
| Example box (outside) | 31 1/2″ × 15 3/4″ × 9 3/4″ |
The volume and tuning are the recommendation, but the port doesn’t fit this example box. Size the box and port in the designer.
Open ported box in designerDeeper: 1.31 ft³ (37 L) tuned to 39 Hz, 31 1/2″ × 15 3/4″ × 8 11/16″ outside — a bigger box with flatter deep bass. Open in the calculator
Projects with this subwoofer
Boxes that users designed and published: plans, cut sheet and response graph.
Thiele/Small parameters
| Size | 8″ |
|---|---|
| Voice coils | 4 Ω |
| RMS power | 125 W |
| Fs | 44.6 Hz |
| Qts | 0.54 |
| Qes | 0.57 |
| Qms | 11.43 |
| Vas | 0.65 ft³ |
|---|---|
| Re | 3.73 Ω |
| Sd | ≈ 33.3 in² |
| Xmax | 0.18″ |
| EBP | 78 — sealed or ported calc. |
| Sensitivity, 1 W / 1 m | 86.6 dB calc. |
Mounting dimensions
| Cutout diameter | 7 1/16″ |
|---|---|
| Mounting depth | 3 3/8″ |
Where it fits in a vehicle
Spots from our vehicle guides where the cutout, mounting depth and recommended box fit. The spot sizes are approximate — measure your own vehicle.
- F-150 SuperCrew — under the rear seat sealed and ported box
- F-150 regular cab — behind the seat sealed and ported box
- Ram Crew Cab — under the rear seat sealed and ported box
- Ram regular cab — behind the seat sealed and ported box
- Tacoma Double Cab — under the rear seat sealed and ported box
- Tacoma Access Cab — behind the front seats sealed and ported box
- Bronco 4-door — behind the rear seat sealed and ported box
- Wrangler 4-door, hard top — behind the rear seat sealed and ported box
- Wrangler 4-door, soft top — behind the rear seat sealed and ported box
- Silverado / Sierra Crew Cab — under the rear seat sealed and ported box
- Silverado / Sierra regular cab — behind the seat sealed and ported box
- Spare tire well sealed and ported box
- Polaris RZR / Ranger — under the seat sealed and ported box
- Can-Am — under the seat sealed and ported box
- Avalanche — under the rear seat sealed and ported box
- FJ Cruiser — behind the rear seat sealed and ported box
- El Camino 1978–87 — behind the seat sealed and ported box
- C10 1973–87 regular cab — behind the seat sealed and ported box
- Cherokee XJ — cargo area, spare moved out sealed and ported box
- Excursion — behind the third row sealed and ported box
- Mustang 2015–2023 coupe — trunk sealed and ported box
- Challenger / Charger — trunk sealed and ported box
- Tesla Model 3 — well under the trunk floor sealed and ported box
- Club Car Precedent — under the rear seat sealed and ported box
“≈” means the value isn’t in the spec sheet and a typical value for the size is used; “calc.” means it’s calculated from the published parameters. Check the manufacturer’s spec sheet before you build.
Data sources
Other Polk Audio 8″ models
- Polk Audio db804 8″ · 4 Ω
- Polk Audio db804DVC 8″ · dual 4 Ω
- Polk Audio db840 8″ · 4 Ω
- Polk Audio db840DVC 8″ · dual 4 Ω
- Polk Audio dX8-4 8″ · 4 Ω
- Polk Audio dX8-8 8″ · 8 Ω
- Polk Audio DXi804 DVC 8″ · dual 4 Ω
- Polk Audio DXi804 SVC 8″ · 4 Ω
- Polk Audio MM840 8″ · 4 Ω
- Polk Audio MM840DVC 8″ · dual 4 Ω
- Polk Audio MM2084 8″ · 4 Ω
- Polk Audio MM2084 DVC 8″ · dual 4 Ω
Similar 8″ subwoofers from other brands
Close in Fs, Qts and Vas — a box of similar volume will suit them.
- Dayton Audio PCS8-4 0.42 ft³ sealed · 0.57 ft³ ported
- Gladen RS 08 (SVC 4 ohm) 0.42 ft³ sealed · 0.53 ft³ ported
- Ground Zero GZTW 20TX (2x2 Ohm) 0.60 ft³ sealed · 0.60 ft³ ported
- Ground Zero GZIW 200X-II (4 Ohm) 0.42 ft³ sealed · 0.49 ft³ ported
- Rockville W8K5S4 0.39 ft³ sealed · 0.92 ft³ ported
- Morel Ultimo Titanium 804 (SVC 4 ohm) 0.46 ft³ sealed · 0.64 ft³ ported
FAQ
What box does the Polk Audio EX8 (EX Series II) need?
Recommended net volume: 0.57 ft³ sealed, 0.53 ft³ ported tuned to 41 Hz — for one sub in a sedan at 125 W. Fit the box to your space and amp in the free calculator, with plans and a cut sheet.
What are the Polk Audio EX8 (EX Series II) Thiele/Small specs?
Fs 44.6 Hz, Qts 0.54, Vas 0.65 ft³, Xmax 0.18″.
What is the Polk Audio EX8 (EX Series II) mounting depth?
Mounting depth is 3 3/8″, cutout diameter 7 1/16″. The inside depth of the box must exceed the mounting depth by at least 1″.
How much power does the Polk Audio EX8 (EX Series II) handle and how do I wire it?
RMS power rating: 125 W. Wiring for several subs and amp power — in the wiring calculator.
Is the Polk Audio EX8 (EX Series II) better sealed or ported?
EBP 78: both work — sealed 0.57 ft³ is tighter and smaller, ported 0.53 ft³ tuned to 41 Hz is deeper and louder.
What port does the Polk Audio EX8 (EX Series II) need?
For the 0.53 ft³ ported box tuned to 41 Hz: slot 1 15/16 × 14 5/16″, 80 5/16″ long, area 28.2 in²; or a round port Ø6″, ≈ 80 5/16″ long. Port air speed at 125 W: 14 ft/s.
What box do two Polk Audio EX8 (EX Series II) subs need?
Two subs need twice the volume: 1.13 ft³ sealed, or 1.06 ft³ ported at the same 41 Hz tuning with twice the port area. One shared chamber or one per sub — whatever fits your vehicle.