B&C design
S21HL
Horn loaded 21" subwoofer
- Drivers
- 1 × 21DS115, 4 Ω
Designed with the 4 Ω version.
21-inch LF driver · 21DS series · 116 mm voice coil · 1,700 W
B&C 21DS115 8Ω
35–500 Hz
- Fs
- 34Hz
- Xmax
- 16.5mm
- SPL
- 97dB
- Pe
- 1700W
- BL
- 39.3T·m
- Vd
- 2673cm³
- Qts
- 0.27
- Vas
- 204L
Published graphs
B&C 21DS115 is a 21-inch 8 ohm LF driver rated at 1700 W RMS. The validated T/S data includes Fs 34 Hz, Qts 0.27, Vas 204 L, Xmax 16.5 mm, sensitivity 96.6 dB, plus 2673 cm³ Vd and 121 EBP. bits tracks UK, EU and US shop prices, price movement, datasheet links, simulator import data, and similar drivers, with a current best price of £475.59.
The published T/S values agree with each other
Thiele/Small
- Fs
- 34Hz
- Qts
- 0.27
- Qes
- 0.28
- Qms
- 10.2
- Vas
- 204L
- Re
- 5.1Ω
- Le
- 4.90mH
Motor and cone
- BL
- 39.3T·m
- Sd
- 1620cm²
- Mms
- 404g
- Xmax
- 16.5mm
- Vd †
- 2673cm³
- Voice coil
- 116mm
- Flux density
- 0.80T
Power and response
- Sensitivity †
- 96.6dB
- Manufacturer sensitivity
- 99dB
- Power
- 1700W
- Nominal power
- 1700W
- Impedance
- 8Ω
- Min. impedance
- 6.6Ω
- Range
- 35–500Hz
- EBP †
- 121 · Leans vented
Size and mounting
- Diameter
- 547mm
- Cutout
- 508mm
- Bolt circle
- 527mm
- Depth
- 255mm
- Weight
- 14.7kg
Sensitivity shows 96.6 dB, calculated from the T/S values. B&C publishes 99.0 dB, 2.4 dB apart.
† Calculated by bits from the published values
What this validation status means
Everything else B&C lists
LF
- BL
- 39.3T·m
- Fs
- 34Hz
- Le
- 4.90mH
- Re
- 5.1Ω
- Sd
- 1620cm²
- Mms
- 404g
- Qes
- 0.28
- Qms
- 10.2
- Qts
- 0.27
- SPL
- 96.6dB
- Vas
- 204L
- Xmax
- 16.5mm
- Power
- 1700W
- Impedance
- 8Ω
- Flux density
- 0.80T
- Sensitivity
- 99dB
- Low limit
- 35Hz
- Nominal power
- 1700W
- Calculated sensitivity †
- 96.6dB
- High limit
- 500Hz
- Manufacturer sensitivity
- 99dB
- Min. impedance
- 6.6Ω
- Voice coil
- 116mm
- Weight
- 14.7kg
- Diameter
- 547mm
- Depth
- 255mm
- Cutout
- 508mm
- Bolt circle
- 527mm
- Bl
- 39.3 Tm
- Fs
- 34 Hz
- Le
- 4.9 mH
- Re
- 5.1 Ω
- Sd
- 1620 cm² (251.1 in²)
- Ebp
- 121 Hz
- Mms
- 404 g
- Qes
- 0.28
- Qms
- 10.2
- Qts
- 0.27
- Vas
- 204 dm³ (7.2 ft³)
- Η0
- 2.7 %
- Cone
- RCK21DS1158
- Xmax
- 16.5 mm
- Xvar
- 13.5 mm
- Depth
- 255 mm (10.04 in)
- Spider
- Double Silicone
- Cone shape
- Radial
- Net weight
- 14.7 kg (32.41 lb)
- Pole design
- T-Pole
- Sensitivity
- 99 dB
- Flux density
- 0.8 T
- Shipping box
- 570x570x320 mm (22.44x22.44x12.60 in)
- Winding depth
- 40 mm (1.57 in)
- Shipping units
- 1 pcs
- Surround shape
- Triple Roll
- Former material
- Glass Fibre
- Frequency range
- 35 Hz - 500 Hz
- Magnet material
- Neodymium Inside Slug
- Shipping weight
- 17 kg (37.48 lb)
- Nominal diameter
- 530 mm (21 in)
- Overall diameter
- 547 mm (21.54 in)
- Winding material
- Aluminium
- Minimum impedance
- 6.6 Ω
- Nominal impedance
- 8 Ω
- Magnetic gap depth
- 14 mm (0.55 in)
- Recommended tuning
- 40 Hz
- Voice coil diameter
- 116 mm (4.5 in)
- Bolt circle diameter
- 527 mm (20.7 in)
- Recommended enclosure
- 170 dm³ (6 ft³)
- Woofer cone treatment
- TWP Waterproof Both Sides
- Baffle cutout diameter
- 508 mm (20 in)
- Nominal power handling
- 1700 W
- Continuous power handling
- 3400 W
- Flange and gasket thickness
- 13 mm (0.51 in)
- Air volume occupied by driver
- 15 dm³ (0.53 ft³)
02
Designs
Cabinets for the 21DS115: two designs and a suggested box from B&C, and plans builders have published.
All 21DS115 designsHow we find designsB&C’s designs
From the maker, with plans to download
B&C design
S21IB
Extended LF Reflex Isobaric Subwoofer
- Drivers
- 2 × 18DS115, 8 Ω1 × 21DS115, 8 Ω
B&C’s suggested box
From B&C’s 21DS115 page
- Net volume
- 170L
- Tuning
- 40Hz
B&C gives the volume and tuning; the port is sized for the driver when you open it.
Modelling the box in 00 Simulator…
03
Compare
Same-size drivers, compared with the 21DS115. Clear differences are green when better and red when worse.
This driver21DS115
Best price
£475.59
Fs
34 Hz
Qts
0.27
Vas
204 L
BL
39.3 T·m
Xmax
16.5 mm
Sensitivity
96.6 dB
Power
1700 W
SB AudienceNERO-21SW1100D
£343.60 · 28% less, betterFs32 Hz −6%
Qts0.34 +26%, worse
Vas312.6 L +53%, worse
BL30 T·m −24%, worse
Xmax12.2 mm −26%, worse
Sensitivity96.7 dB –
Eighteen Sound21LW2600
£425.60 · 11% less, betterFs27 Hz −21%, better
Qts0.33 +22%, worse
Vas333 L +63%, worse
BL32.5 T·m −17%, worse
Xmax14.6 mm −12%, worse
Sensitivity94.9 dB −1.7
CelestionTSQ2145
£445.00 · 6% less, betterFs30 Hz −12%, better
Qts0.34 +27%, worse
Vas253.8 L +24%, worse
BL33.8 T·m −14%, worse
Xmax15 mm −9%
Sensitivity94.8 dB −1.8
Dayton AudioHTS545HE-4
£448.82 · 6% less, betterFs26 Hz −23%, better
Qts0.28 +4%
Vas179 L −12%, better
BL38.2 T·m –
Xmax21 mm +27%, better
Sensitivity92.5 dB −4.1, worse
Eighteen Sound21NLW4100
£456.79 · 4% lessFs36 Hz +6%
Qts0.46 +70%, worse
Vas210 L –
BL29.4 T·m −25%, worse
Xmax15.2 mm −8%
Sensitivity95 dB −1.6
Beyma21LEX1600ND
£475.00 · Same priceFs30 Hz −12%, better
Qts0.29 +7%
Vas305 L +50%, worse
BL36.6 T·m −7%
Xmax14 mm −15%, worse
Sensitivity96.4 dB –
RCFLF21N451
£475.00 · Same priceFs30 Hz −12%, better
Qts0.26 −4%
Vas375 L +84%, worse
BL34.5 T·m −12%, worse
Xmax13 mm −21%, worse
Sensitivity97.8 dB +1.2
Beyma21QLEX1600FE
£493.97 · 4% moreFs30 Hz −12%, better
Qts0.28 +4%
Vas309 L +51%, worse
BL36.4 T·m −7%
Xmax13 mm −21%, worse
Sensitivity96.5 dB –
B&C21SW152
£537.55 · 13% more, worseFs32 Hz −6%
Qts0.36 +33%, worse
Vas200 L –
BL39 T·m –
Xmax15 mm −9%
Sensitivity94.4 dB −2.2, worse
Eighteen Sound21LW1400
£543.74 · 14% more, worseFs28 Hz −18%, better
Qts0.24 −11%, better
Vas385 L +89%, worse
BL33.5 T·m −15%, worse
Xmax9.5 mm −42%, worse
Sensitivity97.5 dB +0.9
Eighteen Sound21NLW9001
£549.89 · 16% more, worseFs32 Hz −6%
Qts0.31 +15%, worse
Vas244 L +20%, worse
BL37 T·m −6%
Xmax14 mm −15%, worse
Sensitivity95.7 dB −0.9
No photo
Precision DevicesPD.2155-1N
£555.00 · 17% more, worseFs33 Hz –
Qts0.36 +33%, worse
Vas241 L +18%, worse
BL30 T·m −24%, worse
Xmax14 mm −15%, worse
Sensitivity95.7 dB −0.9
Eighteen Sound21NTLW5000
£595.00 · 25% more, worseFs31 Hz −9%
Qts0.36 +33%, worse
Vas270 L +32%, worse
BL32 T·m −19%, worse
Xmax17.5 mm +6%
Sensitivity95.3 dB −1.3
Eighteen Sound21NLW4000
£608.33 · 28% more, worseFs29 Hz −15%, better
Qts0.37 +37%, worse
Vas305 L +50%, worse
BL30 T·m −24%, worse
Xmax15 mm −9%
Sensitivity94.9 dB −1.7
Eighteen Sound21NLW9601
£623.80 · 31% more, worseFs37 Hz +9%
Qts0.29 +7%
Vas175 L −14%, better
BL43 T·m +9%
Xmax14 mm −15%, worse
Sensitivity96.6 dB –
No photo
Precision DevicesPD.2160-1N
£799.00 · 68% more, worseFs35 Hz –
Qts0.30 +11%, worse
Vas177 L −13%, better
BL43 T·m +9%
Xmax16 mm −3%
Sensitivity95.9 dB −0.7
B&C21IPAL
£863.28 · 82% more, worseFs37 Hz +9%
Qts0.21 −22%, better
Vas155 L −24%, better
BL19.1 T·m −51%, worse
Xmax22 mm +33%, better
Sensitivity97.6 dB +1
FaitalPRO21XL3000
£899.00 · 89% more, worseFs30 Hz −12%, better
Qts0.25 −7%
Vas284.6 L +40%, worse
BL43 T·m +9%
Xmax17.7 mm +7%
Sensitivity96.9 dB –
EminenceNSW6021-124
£916.36 · 93% more, worseFs31 Hz −10%
Qts0.32 +19%, worse
Vas224.6 L +10%, worse
BL30.5 T·m −22%, worse
Xmax21 mm +27%, better
Sensitivity95 dB −1.6
Dayton AudioPSS545HE-4
No current priceFs29 Hz −15%, better
Qts0.27 –
Vas212.2 L +4%
BL35.5 T·m −10%
Xmax21 mm +27%, better
Sensitivity94.6 dB −2, worse
B&C21SW150
No current priceFs29 Hz −15%, better
Qts0.26 −4%
Vas254 L +25%, worse
BL32.6 T·m −17%, worse
Xmax15 mm −9%
Sensitivity95.6 dB −1
Eighteen Sound21NLW9601C
No current priceFs38 Hz +12%, worse
Qts0.29 +7%
Vas140 L −31%, better
BL33.2 T·m −16%, worse
Xmax14 mm −15%, worse
Sensitivity96 dB −0.6
Sica21 S 4 PL
No current priceFs35 Hz –
Qts0.30 +11%, worse
Vas255 L +25%, worse
BL36.1 T·m −8%
Xmax5.2 mm −68%, worse
Sensitivity97.4 dB +0.8
Eighteen Sound21ID
No current priceFs38 Hz +12%, worse
Qts0.23 −15%, better
Vas143 L −30%, better
BL25.2 T·m −36%, worse
Xmax14 mm −15%, worse
Sensitivity97.2 dB +0.6
Eighteen Sound21NLW5300
No current priceFs31 Hz −9%
Qts0.32 +19%, worse
Vas325 L +59%, worse
BL31 T·m −21%, worse
Xmax15.3 mm −7%
Sensitivity96.6 dB –
No current price
Fs35 Hz –
Qts0.34 +26%, worse
Vas266 L +30%, worse
BL31.3 T·m −20%, worse
Xmax14 mm −15%, worse
Sensitivity97.1 dB +0.5
No photo
Precision DevicesPD.2155-1F
No current priceFs35 Hz –
Qts0.34 +26%, worse
Vas266 L +30%, worse
BL31.3 T·m −20%, worse
Xmax14 mm −15%, worse
Sensitivity97.1 dB +0.5
CelestionNTR21-5010JD
No current priceFs32 Hz −5%
Qts0.32 +19%, worse
Vas276.7 L +36%, worse
BL33.9 T·m −14%, worse
Xmax9 mm −45%, worse
Sensitivity96.4 dB –
No current price
Fs33 Hz –
Qts0.36 +33%, worse
Vas241 L +18%, worse
BL30 T·m −24%, worse
Xmax14 mm −15%, worse
Sensitivity95.7 dB −0.9
Eighteen Sound21LW2500
No current priceFs29 Hz −15%, better
Qts0.37 +37%, worse
Vas305 L +50%, worse
BL30 T·m −24%, worse
Xmax14 mm −15%, worse
Sensitivity94.9 dB −1.7
Tune the match
Choose the published values that matter to your design. Size stays matched to this driver.
Qts
Qes
VasL
Xmaxmm
BLTm
- Thomann5.0 out of 54 ratings · Checked 25 Oct 2026Read reviews on Thomann
Each shop collects its own ratings. Bits shows them as published and doesn't verify them.
| Shop | Price | Against the lowest | Stock | Link |
|---|---|---|---|---|
Thomann | £489.00, the lowest price | In stock | Visit shop at Thomann | |
Blue Aran | £497.00 | 1.6% above the lowest price | 6 in stock | Visit shop at Blue Aran |
Blue Aran 4-6 weeks | £497.00 | 1.6% above the lowest price | Usually available in 4-6 weeks | Visit shop at Blue Aran |
JP Leisure Not currently listed · Last seen 7 Aug 2026 | £503.84 | 3.0% above the lowest price | In stock | Visit shop at JP Leisure |
JP Leisure Not currently listed · Last seen 7 Aug 2026 | £503.84 | 3.0% above the lowest price | In stock | Visit shop at JP Leisure |
JP Leisure | £503.84 | 3.0% above the lowest price | In stock | Visit shop at JP Leisure |
JP Leisure | £503.84 | 3.0% above the lowest price | In stock | Visit shop at JP Leisure |
Audio Video Parts Import VAT and duty may apply | £436.11 | Special order | Visit shop at Audio Video Parts | |
Parts Express Import VAT and duty may apply | £638.91 | 31% above the lowest price | 4 in stock | Visit shop at Parts Express |
Best price over time
Tracked since 1 Apr
Recent changes
- 20 OctThomann£495.00 → £489.00Down 1.2% from £495.00
- 4 OctThomann£499.00 → £495.00Down 0.8% from £499.00
- 23 JunJP Leisure£502.90 → £503.84Up 0.2% from £502.90