Choosing the Best 18" Sub Driver
The best 18 inch sub driver is the one whose parameters fit the cabinet you are building and the amp you are running. Pick the cab first, model the driver's Thiele/Small data in it, then compare displacement, coil size and continuous rating. Price per rated watt comes last, and only between drivers that already fit.
Cab first, driver second
A driver and its enclosure are one system: the same 18" can model well in a reflex box and badly in a horn. Qts and the efficiency bandwidth product (EBP = Fs / Qes) are the first filter.
| Cab type | What it asks of the driver |
|---|---|
| Scoop bin | Strong motor and a suspension that survives heavy back-pressure; high continuous power, because scoops are run hard |
| Folded or rear-loaded horn | Usually low Qts and high Bl. Within the horn's passband the air load restrains the cone, so excursion matters less than motor strength |
| Reflex (ported) box | Moderate Qts and generous Xmax: below tuning the cone is unloaded and excursion rises fast |
Rules of thumb only. Run the actual figures through WinISD or Hornresp for the box you plan to build. See scoop vs reflex vs horn and choosing an 18" scoop driver.
What to compare
- Displacement (Vd = Sd × Xmax). Sets the excursion-limited output below and around tuning. Every doubling of Vd is +6 dB. See Xmax and excursion.
- Voice coil diameter. A larger coil has more surface to shed heat, which limits power compression over a long set. See voice coils and heat.
- Continuous rating. Compare AES or RMS figures, not peak or "program". Note which standard each maker uses. See power ratings explained.
- Sensitivity and power together. On paper, maximum SPL at 1 m is sensitivity + 10·log₁₀(watts). At 93.5 dB and 1800 W that is about 126 dB before power compression and box gain or loss.
- Impedance. Two 8 Ω drivers in parallel give 4 Ω, the usual load for one amp channel. See 4 ohm vs 8 ohm.
- Fit. Cut-out, bolt circle and mounting depth must match the baffle. See will it fit?
The numbers side by side
| Wavemark WM1850/8 | Wavemark WM18X451 | B&C 18SW115 | |
|---|---|---|---|
| Continuous power | 1800 W AES (3600 W peak) | 1800 W RMS (3600 W max) | 1700 W nominal (3400 W continuous) |
| Voice coil | 125 mm | 115 mm (4.5"), copper | 116 mm |
| Sd | 1244 cm² | On request | 1210 cm² |
| Xmax | 12 mm | 14 mm | |
| Vd | 1493 cm³ | 1694 cm³ | |
| Fs / Qts / Vas | 42.9 Hz / 0.644 / 120.9 L | On request | 32 Hz / 0.30 / 187 L |
| Sensitivity | 93.5 dB | On request | 97 dB |
| Motor | Ferrite, vented | Ferrite, double spider | Neodymium |
| Impedance | 8 Ω | 8 Ω (4 Ω option) | 8 Ω |
| Price | £275 | £345 | |
| Price per rated watt | 15.3p | 19.2p |
The B&C is a lower-Qts, neodymium design with 2 mm more Xmax and about 1.1 dB more displacement; the WM1850/8 has the larger coil and Sd and a higher continuous rating. Rating standards differ (AES, RMS, B&C "nominal"), so treat power and price per watt as a guide. For a priced comparison see 15 vs 18 inch subs.
Where each Wavemark driver fits
WM1850/8: Qts 0.644 and EBP 62.9 sit in reflex territory, with 12 mm Xmax and 1493 cm³ of displacement for ported boxes and mixed systems. Cut-out 392 mm, depth 202 mm.
WM18X451: built for scoops and folded horns, with a 4.5" copper coil, ferrite motor and double spider, 1800 W RMS. 8 Ω, or 4 Ω if you want fewer cabs per channel. T/S data on request for modelling.
Both can be heard in our listening room by appointment.
Budget the protection too
A high-pass filter and limiters set from the driver's rating decide how long any 18" lasts. Allow for an amp with headroom and a crossover or DSP with limiting. See amp matching and budget DSP.
Sources: B&C Speakers published data for the 18SW115 (8 Ω), checked 11 October 2026; Wavemark WM1850/8 spec sheet and WM18X451 product data. SPL and displacement figures calculated, rounded.
Questions
What is the best 18 inch driver for a scoop bin?
One with a strong motor, a suspension built for back-pressure and a high continuous rating, modelled in the scoop design you plan to build. The Wavemark WM18X451 is made for scoops and folded horns: 1800 W RMS, 4.5 inch copper coil, double spider, £345.
Which 18 inch driver suits a reflex box?
Look for moderate Qts and plenty of Xmax, because below port tuning the cone is unloaded. The Wavemark WM1850/8 has Qts 0.644, 12 mm Xmax and 1493 cm³ of displacement, rated 1800 W AES, at £275.
How do I compare power ratings between 18 inch drivers?
Compare continuous figures (AES or RMS), not peak or program, and note the standard each maker uses. Then check coil diameter, since a larger coil sheds heat better and compresses less over a long set.
Should I buy a 4 ohm or 8 ohm 18 inch sub driver?
8 ohm lets you run two drivers in parallel on one channel as a 4 ohm load. 4 ohm suits running one driver per channel at higher power, if the amp is rated for it.