SB Acoustics SB17NBAC35-8



The SB17NAC35-8 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:

  • Vented cast aluminum chassis for optimum strength and low compression
  • Geometrically reinforced aluminum cone for optimum piston operation and reduced break-up.
  • Soft 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


Considering its features, build quality and measured performance this mid-woofer has a very high price/performance ratio.

SB Acoustics Spec sheet: 6in SB17NBAC35-8

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.

The drivers where burnt-in for 3 hours at 7 Volts using a 30Hz tone and then cooled off before measuring.



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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.

The cone break-up is visible as a small wrinkle at ~7.5kHz.



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.
Smoothing: No smoothing applied. Measurement valid down to 275Hz.

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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).

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Very smooth frequency response up to 3.5kHz. The cone break-up at ~7.5kHz might need some attention, depending on the choosen cross-over topology. 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. The ~7.5kHz cone break-up show up as a very small elevated 3-order distortion around ~2.5kHz.