Soliloquy-IIb (the Final Cut)

10 Liters Bass Reflex

The Soliloquy-IIb is based on a Tang Band W5-1685 midwoofer. For those who are not in the know, the W5-1685 has an underhung voice coil. What this means is that the voice coil is completely immersed in the magnetic field. The majority of woofers are of the overhang type.

I struggled with the W5-1685 the day I bought them. That was in 2016. The main cause of my disappointment is my Thiele & Small Parameters are not even close to Tang Band’s. Not for the better, I may add. I tried 27 liters followed by 13 liters. This version is the smallest, a compact 10 liters bass reflex. What I was trying to do is to find the best bass quality for an out-of-spec midwoofer.

Fig 1 – Tang Band W5-1685 Box Modeling

Fig 1 is what the Soliloquy-IIb bass reflex alignment looks like. It’s an under-damped alignment with a Q of 0.87. I will lose the tightness in the bass but what I’ll gain is the loudness. I generally avoid high-Q but there are times where I had to resort to it. This is one such case.

Fig 2 – Tang Band W5-1685 RAW Frequency Response • Baffle Width=8″

When I listened to the W5-1685 without any crossover (Fig 1), I was stunned by her excellent midrange. Smooth. No peaks, no honk, no glare. Add to that the boosted bass from the under-damped tuning, the Soliloquy-IIb can be impressive.

Fig 3 – Tang Band W5-1685 RAW and Low Pass Responses

The Blue plot in Fig 3 is the W5-1685 with the midrange finely tuned for the midrange that I want. I expect my tweeter to cross at about 1.8kHz.

Fig 4 – Soliloquy-IIb Passband

The Red plot in Fig 4 is the Seas 27TBFC tweeter crossing at my targeted 1.8kHz. To get this response, the tweeter is flush mounted. More than that, the midwoofer is recessed by exactly the same amount as the tweeter.

Fig 5 – Soliloquy-IIb Frequency Response

The final frequency response of the Soliloquy-IIb is in Fig 5. The midrange is only very slightly more than the bass. Hopefully, the upper bass will not bleed into midrange.

Fig 6 – Soliloquy-IIb NULL

The Violet plot in Fig 6 is the null when I reversed the tweeter wires. It is a sharp, deep notch. The Soliloquy-IIb is time-aligned. Not that I set out to do this, Sometimes, things just fall into place naturally. No need for step. No need for tilting baffle.

Fig 7 – Soliloquy-IIb Frequency Response with Nearfield below 500Hz

The Blue plot in Fig 7 is the nearfield response of the W5-1685. It is a good approximation of what the Soliloquy-IIb sounds like in an anechoic chamber.

Fig 8 – Port Resonance

The Brown plot in Fig 8 is the output of the Soliloquy-IIb port. I am relieved to see there is no peak at 1kHz, not like what I encountered in the Orion-RT13. 

Fig 9 – Soliloquy-IIb Step Response

The Soliloquy-IIb step response is well-mannered. The transient is linear and moderately fast, hitting the apex at 300 microsec. 

Fig 10 – Soliloquy-IIb Waterfall

Fig 11 – Soliloquy-IIb Toneburst Energy Storage

The Waterfall and Toneburst plots recorded some excess energy at 4kHz. They are no cause for concern. It is the ones at 1.5kHz that demands a closer look.

Fig 12 – Soliloquy-IIb Spectrogram

The Spectrogram shows some streaking at 1kHz. It starts to lose it’s energy by 7 msec. During playback, I did not detect any smearing.

Fig 13 – Soliloquy-IIb Impedance

The Soliloquy-IIb is a friendly load for most power amplifiers. The lowest impedance is 5Ω at 150Hz. In the midrange and treble, she hits a high of 9Ω at 600Hz and drops off to 6Ω at 20kHz. Her electrical phase is surprisingly linear. There’s almost no deviation from 200Hz to 20kHz.

At the lower octaves, her box tuning is spot on at 50Hz. This is the Fb that I chose in the box simulation (Fig 1). 

Sound of Soliloquy-IIb

The Soliloquy-IIb is a compact dynamite. Her bass is plentiful, not something one would expect out of a speaker of this size. It is not the tightest bass but is perfectly acceptable for most users, with the exception of hard-core audiophiles.

But there’s more to her than bass. Her strength is in her midrange. Vocals and instruments are sharply focused and not buried somewhere in the mix. 

I played a wide genre of music to test the Soliloquy-IIb. The controversial hit by Phil Collins Another Day in Paradise came out quite nicely. The bass is loud enough. His voice can be clearly heard. Cuts through the mix. Sibilance is well controlled. No harshness in the treble. There’s depth in the sound-stage.

To determine the quality of the bass, I played (Da Le) Yaleo by Santana (Supernatural). With some woofers, the bass sounds like mud. The Soliloquy-IIb, on the other hand, displayed sufficient clarity even with a Q of 0.87.

For vocal harmony, I turned to (I’m Setting) Fancy Free by Oak Ridge Boys. The timing and layering of the vocals can be distinctly heard. Boyz II Men End of the Road is equally heart-rending. Most important or all, the bass is kept well away. Doesn’t interfere with the voices.

Whatever that was not right in the previous Soliloquy-II has been sorted out in this version. The drivers are the same, as is the box and tuning. The main difference lies in the crossover. Now, the vocals project out and that slight edginess in the treble is no longer there.

The sound of the Soliloquy-IIb is very appealing. Loud bass, clear midrange and smooth highs. Her tonal balance is perfect. If you’re not into high-end stuff, this is the speaker you should seriously consider. It can’t get better than this.

Crossover is available on request. Free for DIY. Not for Commercial use.
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.