Mid Bass PA Drivers
A mid bass PA driver covers the band between the subs and the mids, typically from a sub crossover around 80 to 120 Hz up to a few hundred hertz: kick, bass harmonics and the body of a vocal. The job asks for low moving mass and high sensitivity more than long excursion. Wavemark mid bass drivers are coming soon.
Coming soon. Get in touch to hear when mid bass drivers arrive.
Where it sits
In a four-way sound system the mid bass (or "bass", or kick) box runs from the sub crossover to the low-mid crossover. In a three-way PA the low-mid driver in the top box does the same job. See anatomy of a sound system and crossover basics.
Mid bass vs sub drivers on published data
Figures are B&C's published 8 Ω data, with a sub driver for contrast.
| 12PE32 (12") | 15NDL76 (15") | 18SW115 (18" sub) | |
|---|---|---|---|
| Sd | 522 cm² | 855 cm² | 1210 cm² |
| Mms | 37 g | 96 g | 275 g |
| Xmax | 2.8 mm | 7 mm | 14 mm |
| Sensitivity (1 W/1 m) | 101 dB | 99.5 dB | 97 dB |
| Voice coil | 65 mm | 76 mm | 116 mm |
| Fs | 51 Hz | 37 Hz | 32 Hz |
| Beaming onset (ka = 1) | ≈ 424 Hz | ≈ 331 Hz | ≈ 278 Hz |
The pattern is the trade-off in one table. Mid bass drivers carry far less moving mass and much shorter Xmax, so they are more sensitive and cannot move the air a sub can. Above about 100 Hz the excursion needed for a given SPL is a quarter of what it is at 50 Hz (12 dB per octave), so short Xmax is not a limit in their band.
12" or 15"
- Directivity. A cone starts to narrow its coverage around ka = 1, where a is the effective cone radius. On the figures above that is about 424 Hz for the 12" and 331 Hz for the 15". If you cross to mids at 300 to 400 Hz, a 12" holds its coverage further up.
- Displacement and extension. The 15" has 64% more Sd, so more output low in the band, and a lower Fs. It suits a lower sub crossover.
- Box. Mid bass drivers go into reflex boxes, horn-loaded kick bins and front-loaded horns. Model the T/S data in the design. See T/S parameters and horn loading explained.
- Sensitivity. Mid bass boxes run alongside efficient horns, so every dB counts: 3 dB is half the amp power for the same level. See sensitivity and decibels.
Don't share one band between 12s and 15s: different Mms and tuning shift phase through the overlap. Give each size its own band.
Sub drivers available now
All current drivers: 18" sub bass drivers.
Sources: B&C Speakers published data for the 12PE32, 15NDL76 and 18SW115 (8 Ω), checked 11 October 2026. Beaming onset calculated from Sd as f = c / (2πa), c = 343 m/s, rounded.
Questions
What frequency range does a mid bass driver cover?
Typically from the sub crossover, around 80 to 120 Hz, up to the low-mid crossover at a few hundred hertz. The exact band depends on the system's crossover points.
Is a 12 inch or 15 inch better for mid bass?
A 15 inch has more cone area and usually a lower Fs, so it suits a lower sub crossover. A 12 inch keeps its coverage higher (beaming starts around 424 Hz for a 522 cm² cone against about 331 Hz for 855 cm²), so it suits a higher crossover to the mids.
Why do mid bass drivers have so little Xmax?
They don't need it. Excursion for a given SPL falls 12 dB per octave as frequency rises, so above 100 Hz a short-throw, low-mass cone is more efficient. B&C's 12PE32, for example, has 2.8 mm Xmax, 37 g Mms and 101 dB sensitivity.