Vifa PL11MH-09-08 Premium Line 4″ Midrange
I have this Premium Line 4″ midrange since the late 1990s. At that time, Vifa was still made in Denmark. All this while, it was kept in storage. This is the first time I’m listening to it, a good 20 years later.
To replicate the sub-chamber for the PL11MH in a 3-way box, I made a small test box of 1.7 liters internal volume. If the PL11MH tests out fine, it will pave the way for a proper design. Box modeling predicts F3 to be about 150Hz with a Q of 0.68.
In this review, I’ll be listening to the PL11MH without any crossover. No tweeter, no woofer. Just the PL11MH direct from the amplifier.
Fig 1 – Vifa PL11MH-09-08 Sealed Box 1.7 liters. F3=157Hz. Q=0.68
Fig 2 – Vifa PL11MH-09-08 RAW Frequency Response. Measurements below 500Hz are in Nearfield.
Fig 2 is the RAW response of the PL11MH in the test box with a baffle width of 6.5″. It is impressively flat with a remarkable treble extension. Come to think of it, it looks exactly like Vifa’s FR plot (see top of page). Mic is at 1 meter, PL11MH axis. Impulse Window=5ms. No smoothing applied.
With a response like this, the PL11MH can even be used as a full-range driver. It goes as high as 10kHz, which looks like the cone breakup. The response is flat up to 6kHz, after which it starts to roll-off. The optimum crossover is about 3kHz but anywhere from 2.5kHz to 4kHz will work fine. My yet to be tested Fountek NEO CD3.5H will fit right in at 2.5kHz. And should I decide to cross higher up at 4kHz, my HiVi RT1C Planar tweeter is there waiting.
Fig 3. REW Waterfall. Rise Time = 0.10 msec. Window = 1.3 msec ( 769Hz ). Time Range = 1.0 msec
Fig 3 is a highly magnified Waterfall plot of the PL11MH. For clarity, I adjusted it for -20dB from the fundamental. We can clearly see the artifacts at 10kHz. This corresponds with the 10kHz peak in Fig 2, confirming that it is indeed the cone breakup. The 10kHz artifacts will not present any problems because they are well away from the optimum crossover frequencies. At such a rapid decay of less than 1ms, these artifacts will not degrade the treble should the PL11MH be used as a full range driver.
Fig 4 – Toneburst Energy Storage of Vifa PL11MH-09-08
In Fig 4, stored energy (the light blue slices), is recorded at 10kHz. As in the Waterfall plot, it starts at -20dB below the fundamental and last for a duration of 6 cycles.
Fig 5 – REW Spectrogram of Vifa PL11MH-09-08
In the Spectrogram (Fig 5), the cone breakup at 10kHz is not even seen because it’s less than 1ms. What is shown is from 3.5kHz down to 1kHz, there are some artifacts. I seriously doubt we can hear any smearing at 6ms. Readings below 1kHz include room reflections.
Fig 6 – Harmonic Distortion of Vifa PL11MH-09-08. Red plot=2nd harmonic. Violet plot=3rd harmonic.
Fig 6 is the Harmonic Distortion of the PL11MH. Generally, the 2nd and 3rd harmonics are about -55dB below the fundamental. No anomaly is seen throughout.
the sound of a vintage Vifa PL11MH-09-08
WOW! I was simply bowled over. The tonal quality is incredible. This PL11MH midrange has a certain mellowness and warmth that is missing from the other drivers that I have. Vocals and wood instruments in particular, sound wonderful.
If I’m not mistaken, some high-end speakers used this midrange in it’s time. It’s that good. It is a shame that this beauty is no longer in production. The now defunct Vifa had some really good drivers. This PL11MH-09-08 was one of them.