SB Acoustics SB23NRXS45-8

Overview:


The SB Acoustics SB23NRXS45-8 is an 8Ω 8″ woofer from SB Acoustics. The woofer has a 45.5mm voice-coil with a 13mm (p-p) linear coil travel. It’s fitted with a shorting ring in motor system for reduced distortion.

Key features:

  • Soft low damping rubber surround for improved transient response
  • Shorting ring in motor system for reduced distortion
  • Vented pole piece for reduced compression
  • Vented cast aluminum chassis for optimum strength and low compression
  • Shallow design
  • Non-conducting fiber glass voice coil former for minimum damping
  • CCAW voice coil for reduced moving mass
  • Long life silver lead wires

 

SB Acoustics Spec sheet: 8in SB23NRXS45-8 Rev-1

T/S Parameters:

 

 

 

Impedance:

 

(click on picture to zoom)

Blue: Mid-woofer sample #1

Green: Mid-woofer sample #2

A small resonance issue around 1kHz

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): 26×40cm with 18mm round-over on the baffle edges (r=18).
Driver position: Mounted on center-line with driver unit center 24cm from the top of the baffle.
Mic position: 1m distance, on woofer-axis. Nearfield at 1cm and 10cm from dust-cap.
Smoothing: 1/24 octave smoothing applied.

 

(click on picture to zoom)

Left: Frequency response on-axis near-field 1cm from dust-cap (Blue=sample#1 Red=sample#2).
Right: Frequency response on-axis near-field 10cm from dust-cap (Blue=sample#1, Red=sample#2).

 

(click on picture to zoom)

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

The SB23NRXS45-8woofer has a very smooth frequency response up to about 2.2kHz.

Distortion:

 

Measurement setup:

  • Mid-woofer near-field measurement at 20cm
  • Frequency range woofer: 100-10000Hz
  • Baffle size WxH: 26×40cm

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.

(click on picture to zoom)

90dB @ 1m

Left = Sample #1

Right = Sample #2

(click on picture to zoom)

95dB @ 1m

Left = Sample #1

Right = Sample #2

The SB23NRXS45-8  woofer is overall a low distortion driver. The resonance issue shown in the impedance plot around 1kHz is shown here as a slightly elevated odd order distortion.  The woofer’s odd-order distortion is low below 0.6kHz and it has a slightly increasing odd-order distortion above 0.6kHz.