SB Acoustics SB17NRXC35-8

Overview:

The SB Acoustics SB17NRXC35-8 is an 8Ω  6″ mid-woofer from SB Acoustics.

The mid-woofer has a 35.5mm voice-coil with a healthy 11mm (p-p) linear coil travel. It has a very low voice-coil inductance and is fitted with a copper sleeve on the pole piece to ensure a low distortion performance.

Key features:

  • Vented cast aluminum chassis for optimum strength and low compression
  • Proprietary cone material with natural fibers made in-house
  • Soft low damping rubber surround for improved transient response
  • Non-conducting fiber glass voice coil former for minimum damping
  • Extended copper sleeve on pole piece for low inductance and low distortion
  • CCAW voice coil for reduced moving mass
  • Long life silver lead wires
  • Vented pole piece for reduced compression

 

SB Acoustics Spec sheet: 6in SB17NRXC35-8

T/S Parameters:

 

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T/S Parameters measured using DATSv2. Higher Qts and lower sensitivity than the official specification.

Impedance:

 

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Blue: Mid-woofer sample #1

Green: Mid-woofer sample #2

A small resonance issue around 1.4kHz

Frequency:

 

Frequency measurement conditions:

The mid-woofer is measured mounted on a baffle in an 14 liter closed enclosure with the following conditions:

Baffle size (WxH): 24×35cm with 18mm round-over on the baffle edges (r=18).
Driver position: Mounted on center-line with driver unit center 22cm from the top of the baffle.
Mic position: 1m distance, on mid-woofer-axis.
Smoothing: 1/24 octave smoothing applied.

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Left: Frequency response on-axis (Blue=sample#1 Red=sample#2).
Right: Frequency response 15deg off-axis (Blue=sample#1, Red=sample#2).

0deg = Blue
15deg = Red
22.5deg = Green

30deg = Blue
45deg = Red
60deg = Green

Smooth frequency response up to 3kHz. The highest suitable cross-over frequency is around 2-2.5kHz.

Distortion:

 

Measurement setup:

  • Mid-woofer near-field measurement at 18cm
  • Frequency Range Mid-woofer: 200-10000Hz
  • 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

The SB17NRXC35-8  mid-woofer is overall a low distortion driver. However, the resonance issue shown in the impedance plot around 1.4kHz is shown here as a spike of odd order distortion.  Because of the overall very low distortion profile, the narrow banded odd-order distortion spike at 1.4kHz look worse than it is. The rise in the second-order distortion at the same frequency might contribute to some coloration or unique sound character.