Description
The SB21SDC-C000-4 is a 21 mm fabric dome tweeter from SB Acoustics, positioned as a balanced performer between compact size and excellent sound quality. It’s a great choice for high-quality 2-way designs, especially when you want a smooth, detailed top end without the harshness.
Features
- Large surround dome for increased acoustic output
- Dual balanced compression chamber for improved dynamics
- Copper cap for reduced voice coil inductance and minimum phase shift
- Saturation controlled motor system for low distortion
- Non-reflective rear chamber with optimized damping for improved dynamics
- Flow optimized vented pole piece for optimum coupling to rear chamber
- CCAW voice coil for low moving mass
- Long life silver lead wires
- Low resonance frequency
Specs
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- Nominal Impedance 4 Ω
- DC resistance, Re 3.4 Ω
- Voice coil inductance, Le 0.07 mH
- Effective piston area, Sd 3.8 cm2
- Voice coil diameter 19.1 mm
- Voice coil height 1.8 mm
- Air gap height 3 mm
- Linear coil travel (p-p) 1.2 mm
- Moving mass incl. air, Mms 0.22 g
- Free air resonance, Fs 980 Hz
- Sensitivity (2.83 V / 1 m) 88.5 dB
- Mechanical Q-factor, Qms 6.45
- Electrical Q-factor, Qes 1.50
- Total Q-factor, Qts 1.22
- Force factor, Bl 1.75 Tm
- Rated power handling* 30 W
- Magnetic flux density 1.24 T
- Magnet weight 0.13 kg
- Net weight 0.32 kg
* IEC 268-5, high-pass Butterworth, 2600 Hz, 12 dB/oct.
✅ What Makes It Stand Out
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Exceptionally low Fs (~900 Hz) – allows for lower crossover points, even under 2 kHz.
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Integrated waveguide – improves efficiency and off-axis response.
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Smooth tonal balance – no shoutiness or harsh peaks.
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High sensitivity (91 dB) – can pair well with higher-efficiency woofers.
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Affordable with premium sound – high value in the DIY and OEM space.
🔧 Best Use Cases
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2-way speakers with 5.25″–7″ woofers.
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Tower or bookshelf designs where wide dispersion and smoothness matter.
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Upgrades for midrange speaker builds looking to improve clarity.
🛠️ Crossover Tips
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Recommended crossover: 1.8–2.5 kHz (even lower possible with proper slopes)
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Pair it with:
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SB17NRX2C35-4 (6.5″ woofer)
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SB16PFC25-4 (5.5″ paper woofer)
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Or similar drivers with a natural roll-off around 2–2.5 kHz
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⚖️ Comparison: SB21SDC vs SB26STCN
| Feature | SB21SDC-C000-4 | SB26STCN-C000-4 |
|---|---|---|
| Dome Size | 21 mm | 26 mm |
| Fs | Lower (~900 Hz) | Higher (~1.6 kHz) |
| Sensitivity | Higher (~91 dB) | Slightly lower (~90–91 dB) |
| Faceplate | With waveguide | Standard faceplate |
| Price | Budget-friendly | Budget-friendly |
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