Overview:
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The SB Acoustics SB29RDC is a 4Ω coated textile ringe dome tweeter using a 29mm voice coil together with a copper cap pole piece
Key features:
- Non-resonant diaphragm design for minimum high frequency break-up
- 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
SB Acoustics Spec sheet: SB29RDC
T/S Parameters:
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10% resonance frequency difference between the two driver samples.
Impedance:
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Sample 1 = Green
Sample 2 = Blue
Besides the resonance frequency difference, the two drivers measures identically.
Frequency:
Frequency measurement conditions:
The tweeter is measured mounted on a baffle with the following conditions:
Baffle size (WxH): 24×35cm with 18mm round-over.
Driver position: Mounted on center-line with driver unit center 8cm from the top of the baffle.
Mic position: 1m distance, on tweeter-axis.
Smoothing: 1/24 octave smoothing applied.
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Left: Frequency response on-axis (Blue=sample1, Red=sample2).
Right: Frequency response 15deg off-axis (Blue=sample1, Red=sample2).
The two driver samples have almost identical frequency responses. The on-axis measurement shows a rising frequency response above 9kHz.
0deg = Blue
15deg = Red
22.5deg = Green
30deg = Blue
45deg = Red
60deg = Green
Distortion:
Measurement setup:
- Tweeter near-field measurement at 10cm
- Frequency Range Tweeter: 500-10000Hz
- Baffle size WxH: 24×35cm
The distortion measurements are done in near-field and the amplifier output level was adjusted for each driver so that the fundamental is 90dB and 95dB at 1m. This setting simulates medium-high and high listening levels.
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90dB @ 1m
Left = Sample 1
Right = Sample 2
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95dB @ 1m
Left = Sample 1
Right = Sample 2
Very low odd-order distortion profile down to 2kHz. Rapidly rising distortion below 3kHz as well as a spike at 5.5kHz of the relatively harmless second-order distortion profile.