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SB Acoustics SB21RDC-C000-4 Tweeter

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The SB21RDC-C000-4 by SB Acoustics is a 21mm ring radiator tweeter. The centre of the diaphragm is inverted and bonded to an internal dimple on the pole piece, this innovation negates the need for a front phase plug and gives excellent extension to above 20kHz.

Key Features:

  • Inverted centre phase plug free design
  • Non-resonant diaphragm design for minimum high frequency break-up
  • Dual balanced compression chamber for improved dynamics
  • Copper capped pole for reduced voice coil inductance and minimum phase shift
  • Saturation controlled motor system for low distortion
  • Non-reflective rear chamber with optimised damping for improved dynamics
  • Flow optimised vented pole piece for optimum coupling to rear chamber
  • CCAW voice coil for low moving mass
  • Long life silver lead wires
  • Low resonant frequency

Basic parameters:

Resonant frequency (fs) 760 Hz Nominal impedance (Zn) 4 Ω
Effective diaphragm diameter 21mm DC resistance (Re) 3.0 Ω
Ferrofluid ? Y/N Yes
Max power handling 60 W
Recommended crossover 2.6kHz/12dB Faceplate diameter 92mm
Sensitivity (2.83V/1m) 90dB Cutout hole diameter 64mm

Here's the full datasheet:

.pdf link

Customer Reviews

Based on 1 review
Peter Bauckham
Inexpensive replacement for old Scanspeak D2008

Firstly, thank you for the excellent service!

I wanted to replace a pair of old 92mm faceplate Scan-speak D2008/8203 tweeters I've been using with KEF B100B bass driver for many years. The replacement D2008/8511(now discontinued) would 'drop in', although isn't a perfect replacement efficiency or sound wise (the 8203 was heavily doped). The wonderful Hiquphon OW1/92 would be first choice but sadly out of my price range!

The SB21RDC-C000-4 required a little modification to the cabinet, simply to accommodate the connectors, and has four screw holes rather than three - but fits flush with the baffle.

I've had to re-work the crossover somewhat (this is a 4ohm tweeter), but the results are very promising using a third-order high-pass with an l-pad (1.5/2.7 ohm based on the 3 ohm DCR). Currently using a 5.6 and 16 microfarad capacitors and a 0.125mH inductor, which seems to blend rather well. I'm sure I'll tinker more, but there's really nothing to dislike as it is.

Thankyou for your review Peter!
Will & Caroline