SB Acoustics SB17NRXC35-4



The SB Acoustics SB17NRXC35-4 is a 4Ω  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


Note! This driver has been discontinued, but can be found second hand and at some shops!

SB Acoustics Spec sheet: SB17NRXC35-4 Rev-1-DISCONTINUED

T/S Parameters:


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Left: T/S parameters measured using “added” mass method in horizontal position.

Right: T/S parameters measured using “known” mass method in vertical position.



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Left: Free-air impedance driver sample #1 vs. sample #2.
Right: Close-up of free-air impedance driver sample #1 vs. sample #2.

Some wrinkles in the impedance plot are visible at about 1.0-1.5kHz.


Frequency measurement conditions:

The mid-woofer is measured mounted on a baffle in an 17.6 liter closed enclosure with the following conditions:

Baffle size (WxH): 20×40cm. No baffle edge round-over.
Driver position: Mounted on center-line with driver unit center 17cm from the bottom of the baffle.
Mic position: 1m distance, on mid-woofer-axis. Measurement valid down to 275Hz.
Smoothing: No 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).

Some difference between the two tested driver samples around 1.2-1.7kHz.

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2.5kHz is about the highest suitable cross-over frequency for this mid-woofer.



Measurement setup:

  • Mid-woofer near-field measurement at 18cm
  • Frequency Range Mid-woofer: 200-10000Hz
  • Baffle size WxH: 20×40cm

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 to high listening levels.

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Left: = 90dB @ 1m

Right: = 95dB @ 1m

Overall this is a very low distorting mid-woofer. We have some harmless elevated second-order harmonics around 1.3KHz, around the cone edge resonance.