SB Acoustics SB23NBACS45-8 8" Woofer Review

In this blog post I review the SB Acoustics SB23NBACS45-8 8" aluminum woofer. This woofer features an extensive list of features: 

  • Soft low damping rubber surround for improved transient response
  • Geometrically reinforced aluminum cone for improved break-up control
  • 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 fibre glass voice coil former for minimum damping
  • CCAW voice coil for reduced moving mass
  • Long life silver lead wires

Measurements 

I conducted my measurements outdoors to eliminate the affects of the room acoustics in my test results.  The test cabinet was constructed from 0.75" (19mm) MDF.  The internal volume was 80 liters tuned to 25Hz. Below is a picture of my test setup for near field measurement.  No did not use any software gating for this review.

Frequency Response 

Below is the frequency response at 1 meter mic distance. 

I then conducted a frequency response measurement using the near field technique.  The driver exhibits a sharp resonance at 1.7kHz resulting in a high 'Q' null.  Otherwise the driver shows a very flat response from 35Hz to 1kHz.

I set up the cabinet in the middle of my studio and conducted a frequency response measurement at 1m mic distance.  The room boundaries helped bring the bass response up quite a bit.  The results are shown below with 1/1 octave smoothing to show the general trend in the response. 

Step Response

Below is the step response. 

I then decided to zoom in on the step response results for clarity. 

Burst Decay 

The burst decay results are shown below. The driver produces a very resonance free result until the main diaphragm breakup at 1.7kHz

 

Distortion

I began by looking at harmonic distortion at 70dB SPL at 1m. The driver produces very low levels of 3rd order at 100Hz of only 0.032% (-60.76dB).   Distortion rises at 1kHz to 0.20% (-53.7dB).  

Increasing the SPL from 70dB to 80dB sees distortion improve (See below). 100Hz is now only 0.014% (-76.8dB) and 1kHz is 0.18% (-54.53db).

Increasing the SPL form 80dB to 90dB sees distortion rise.  100Hz is 0.65%(-43.6dB) and 1kHz is 0.54%(-45.23dB).

Intermodulation Distortion 

Using a F1 of 100Hz and F2 of 600Hz at 80dB SPL generates many side band products that are around -52dB down (0.25%).   

Increasing the SPL to 90dB (see below) the distortion rises to -43dB (0.71%).  

 

Conclusion 

The SB Acoustics 8" SB23NBACS45-8 produces acceptable performance within is operating bandwidth and SPL.  The driver produced low distortion under 83dB SPL which means it is suitable for small listening rooms at moderate listening levels.  This driver should be crossed over at 1kHz or lower.  

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