The Fountek FR88EX is a 3″ full range driver that’s similar to her cheaper sister, the FR85. Both have aluminum cones but the FR88EX has a cast frame and her magnet is neodymium. It’ll be interesting to see how she fares. For a quick test, I mounted her in a 6 liters sealed box. My aim is to find out how she sounds like, particularly in the treble. That was where the FR85 was slightly brittle.
Fig 1 – Fountek FR88EX Frequency Response • Baffle Width=8-1/2″
Fig 1 is the RAW response of the FR88EX. It is incredibly flat all the way to 20kHz. There’s a dip at 12kHz and 18kHz which won’t have much of an effect. What is shocking is when I played music. The FR88EX tonal balance is perfect. More than that, there’s no brittleness in the treble. Bass is obviously lacking but that’s not an issue. I powered up the Palila bandpass sub and that’s it, I have a complete bandwidth. I am listening to the FR988EX with the Palila as I’m writing and it’s thoroughly enjoyable. No crossovers are used. It can’t get simpler than this.
Fig 2 – Fountek FR88EX Step Response
The step response (Fig 2) of the FR88EX is something to die for. She takes off like a rocket, hitting the apex at 25 microsec. Her decay is fast too.
Fig 3 – Fountek FR88EX Waterfall
The Waterfall (Fig 3) shows artifacts in the lower and higher treble.
Fig 4 – Fountek FR88EX Toneburst Energy Storage
The artifacts are more prominent in the Toneburst plot (Fig 4). In this plot, they are the light blue slices. They don’t look very encouraging but they are not harmful. Perhaps even necessary. My guess is they are the cone ringing. How else is a woofer going to have treble without a tweeter. Induce some cone ringing to simulate the highs.
Fig 5 – Fountek FR88EX Spectrogram
The Spectrogram (Fig 5) shows how well Fountek did with the FR88EX. From 2kHz upwards, it’s clean. They designed it such that the cone ringing is just right to extend the bandwidth. There’s no streaking anywhere.
Below 2kHz, there’s a delayed hot spot at 1.5kHz. It is dissipated by 8 msec. I didn’t hear anything during playback so it’s as good as not being there.
Fig 6 – Fountek FR88EX Harmonic Distortion
The FR88EX fares better than the FW100B in distortion. The 2nd (Red plot) and 3rd (Violet plot) harmonics are -50dB below the fundamental.
Fig 7 – Fountek FR88EX Sealed Box modeling
The FR88EX box modeling is in Fig 7. It is a sealed box with an F3 of 112.5Hz. I feel it’s rather big for a 3″ woofer. I will likely build a smaller 3 liter box later. My only worry is whether the Qtc will be too high. If I were to use Fountek’s specs, the Qtc is 0.56 for 3 liters sealed box. Either way, it’s worth a try.
The FR88EX opens up tremendous possibilities in speaker design. I can have her as mini monitors supported by subwoofers, similar to the Bose Acoustimass or the Bowers & Wilkens. That has a wide appeal, particularly to the missus.
Alternatively, the FR88EX can be integrated with a woofer. Imagine, a 10″ with the FR88EX. It will definitely give the Seas A26 kit a run for the money. How about a slim tower using 2 units of 6-1/2″ woofers for bass and a FR88EX for mid and highs. I can go on but I’m sure you get the picture.
Unless otherwise stated, all measurements were made in Full Space (4 pi) with the mic at 36 ins, tweeter axis. Impulse Window=5ms. No smoothing applied.
March 24, 2021Drivers Evaluation