SB Acoustics SB17CRC35-8

Overview:

 

The SB17CRC35- is an 8Ω  6″ mid-woofer from SB Acoustics.

The mid-woofer has a 35.5mm voice-coil with a 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:

  • Rohacell/Carbon fibre sandwich cone for optimized stiffness/damping ratio.
  • Vented cast aluminum chassis for optimum strength and low compression.
  • Low damping rubber surround for improved transient response.
  • Non-conducting fibre 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 SB17CRC35-8 rev-2

T/S Parameters:

 

t-s-parameters-wt2t-s-parameters-wt3

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Left: T/S parameters measured with Smith & Larson Audio WT2 woofer tester. Measured “cold”.

Right: T/S parameters measured with Dayton Audio WT3 woofer tester. Measured after 10min of 5volt “massage” @ 28Hz.

Higher Qts and resonance frequency as well as a slightly lower sensitivity than the official specification.

Impedance:

 

imp-sb17crc-8-1l-vs-2rimp-sb17crc-8-1l-vs-2r-zoom

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Left: Mid-woofer sample #1 vs #2.

Right: Mid-woofer sample #1 vs #2 close-up.

A visible resonance issue at 1.6-1.7kHz and 6.5kHz.

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.

freq-sb17crc35-8-0deg-1l-vs-4rfreq-sb17crc35-8-15deg-1l-vs-4r

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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).

freq-sb17crc35-8-0-15-22deg-1l-vs-4r

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

freq-sb17crc35-8-30-45-60deg-1l-vs-4r

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

Smooth frequency response up to 4kHz. Minor cone break-ups at 4.9kHz and 6.5kHz. The resonance issue seen in the impedance plot at 1.6-1.7kHz is seen here as a frequency dip in the off-axis frequency measurements.

2kHz is about the highest suitable cross-over frequency for this mid-woofer.

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.

sb17crc35-8-1-18cm-90dbsb17crc35-8-2-18cm-90db

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90dB @ 1m

Left = Sample #1

Right = Sample #2

sb17crc35-8-1-18cm-95dbsb17crc35-8-2-18cm-95db

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95dB @ 1m

Left = Sample #1

Right = Sample #2

The SB17CRC35-8  mid-woofer has a generally low distortion profile. However, the resonance issue shown in the impedance and frequency plots at 1.6-1.7kHz is found here as an elevated odd and even order distortion.  Because of the overall very low distortion profile, the odd-order distortion spike at 1.6-1.7kHz 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.