NM-4 (Natural Music)
Fountek FW-100B with Dayton DA215-8
The NM-4 is a departure from the previous designs in that she doesn’t use a full range or a coaxial. Instead, she has a midwoofer to take care of the mids and highs. This driver is one of my favorites, the Fountek FW-100B.
 Fig 1 – Fountek FW-100B Frequency Response in 1.7L Sealed Box.
Fig 1 is the RAW Frequency Response of the FW-100B in a 1.7 liters sealed box. Based on her response alone, she is as good as the other fullrange drivers like the Mark Audio CHP-70. She extends to 7.5kHz after which she rolls off.
 Fig 2 – MN-4 Frequency Response (Fountek FW-100B with DA215-8)
Fig 2 is the frequency response of the FW-100B with the Dayton DA215-8. What I really love with this Fountek is the smoothness in the midrange. Saxophones like Kenny G don’t shout at you. There’s a gradual roll-off in the treble but it doesn’t affect the presence.
 Fig 3 – NM-4 Harmonic Distortion
The Harmonic Distortion (Fig 3) in the upper midrange to the treble is outstanding. 2nd harmonics at -55.1dBr and the 3rd at -59.2dBr. I do not expect the treble to give me issues.
 Fig 4 – NM-4 Toneburst Energy Storage
For a 4″ metal cone midwoofer, the Toneburst plot (Fig 4) is impressive. There’s hardly any stored energy (light blue slices) in the treble. This indicates a very “clean” treble.
 Fig 5 – NM-4 Waterfall
The Waterfall plot in Fig 5 shows minimal artifacts in the highs. The peak at 7kHz is clearly seen. However, it is not audible as it’s dissipated by 2ms.
 Fig 6 – NM-4 Spectrogram
The Spectrogram (Fig 6) confirms the 7kHz peak is inconsequential. Doesn’t even last 1ms. In fact, from 2kHz onwards, the FW100B is exceptionally clean.
From 800Hz to 2kHz, there are some streaking. Their intensity is much less than the other drivers before. During auditioning, I didn’t pick up these streaks so not an issue.
 Fig 7 – NM-4 Step Response
The Step Response (Fig 7) is the FW-100B with the Dayton DA215-8. The FW-100B step is almost perfect so using this Fountek is in line with the philosophy of the NM series.
 Fig 8 – NM-4 Excess Group Delay
The Excess Group Delay (Fig 8) does not show any anomaly in the bass region. From this, I do not expect the bass to lag the midrange.
Summary
The Fountek FW-100B may not be listed as a fullrange driver but she performs better than one. At only $15 in 2021, she is fantastic value for money. Unfortunately, she is no longer available. Ever since the Covid pandemic, Fountek, like so many others, have scaled back their line. Hopefully in future, more drivers will be offered.
If you happen to have a pair of these FW-100B lying around, the NM-4 is the perfect build. More than that, she is a minimalist design. Only one inductor and capacitor.
Unless otherwise stated, all measurements were made in Full Space (4pi). Mic at 36 ins, tweeter axis. Impulse Window=5ms. No smoothing applied. |
