Kingfisher (the poor man’s B&W Matrix 801)

SUPERMICRO-DX3P

Kingfisher

The Kingfisher is inspired by the B&W 801. The journey started out in September, 2016 as the SuperMicro, a mini sealed 2-way using a full range Tang Band W3-1364SA with the Peerless BC25SC08 tweeter. The problem I have with the W3-1364SA is the cost because my aim is to use the cheapest driver available. With the BC25SC08, it’s not so much the money but the crossover. It sounded stressed when I crossed it at 2.5kHz.

It wasn’t until the SuperMicro-DX2 that I found the right drivers. The Fountek FE85 and the Peerless DX20BF00-04 are exactly what I’m after – cheap yet very good performance. After that came the SuperMicro-DX3 when I integrated a woofer in. The Kingfisher is the passive version of the SuperMicro-DX3.

SuperMicro-DX2
(passive crossover)FOUNTEK FE85 BANDPASS PEERLESS DX20BF HIGH PASS

Fig 1 – FE85 (250Hz-2.5kHz Bandpass). DX20BF00-04 (2.5kHz High Pass)

Fig 1 shows the frequency response of the Fountek FE85 and the Peerless DX20BF00-04 with their respective passive networks. The Blue plot is the FE85 with a Bandpass Filter. High Pass is 250Hz and Low Pass is 2.5kHz, both at 12dB/oct. The Red plot is of the DX20BF00-04 tweeter with a High Pass filter at 2.5kHz. For the tweeter, I prefer to use 18dB/oct. Acoustically, the two drivers are crossing at about 2.8kHz. That’s due to the slight bump of the FE85 at 2kHz. 

SuperMicro-DX3
(passive crossover)

SILVER FLUTE W20RC LOW PASS FOUNTEK FE85 BANDPASS PEERLESS DX20BF HIGH PASSFig 2 – Brown plot = Silver Flute W20RC38-08 with 250Hz Low Pass filter

The Brown plot in Fig 2 is of the Silver Flute W20RC38-08 low passed at 250Hz, again at 12dB/oct. Disregard the deep notch at 150Hz. That is an anomaly in my room, nothing to do with the crossover or the woofer. Due to my room limitations, measurements below 500Hz include room reflections.

Kingfisher Frequency Response
SUMMED RESPONSE W20RC38 FE85 DX20BF

Fig 3 – 3way Passive Summed Response

Fig 3 is the summed response of the Silver Flute W20RC38-08, the Fountek FE85 and the Peerless DX20BF00-04. Measurements from 500Hz~20kHz are within an impulse window of 5 msec. In other words, there are no room reflections. It’s quite encouraging that it’s within a fairly tight window of + / – 2.5dB.

Kingfisher Nearfield Spliced

KINGFISHER NEARFIELD SPLICED FRFig 4 – Response smoothed at 1/12 oct.

B&W MATRIX 801 FREQUENCY RESPONSEFig 5 – B&W Matrix 801 Frequency Response. (Courtesy of Stereophile)

Fig 4 is the frequency response of the Kingfisher with the Silver Flute W20RC38-08 nearfield measurement spliced in. I smoothed the response at 1/12th for easier comparison with Stereophile’s B&W Matrix 801 (Fig 5). It’s encouraging to see the Kingfisher frequency response flatness similar to that of the B&W Matrix 801.

Cumulative Spectral Decay

WATERFALL KINGFISHERFig 6 – Kingfisher Waterfall Plot. (Courtesy of REW)

Fig 6 is the Waterfall plot. The time range is 1 msec, so it’s a highly magnified view. We can see there’s virtually no audible artifacts from 4kHz upwards.

Toneburst Energy Storage
TONEBURST ENERGY STORAGE KINGFISHER

Fig 7 – Toneburst Energy Storage of Kingfisher

The light blue slices in Fig 7 are the stored energy of the Kingfisher. They correlate to the 1kHz~3kHz hump in Fig 3. My guess is they’re probably baffle diffraction. Above 3kHz, the tiny stored energy dissipates rapidly. From 4kHz~20kHz, there’s no sign of stored energy. This verifies the Waterfall plot in Fig 6. 

SpectrogramSPECTROGRAM KINGFISHER

Fig 8 – Spectrogram of Kingfisher

The Spectrogram in Fig 8 is another view of the Stored Energy. The burst of energy from 1kHz to 3kHz is clearly visible. They don’t look serious. The main burst at the left is already down -40dB by 6 msec. At 10 msec, it’s almost zero.

Harmonic Distortion

NARMONIC DISTORTION KINGFISHERFig 9 – Red plot = 2nd harmonics. Violet plot = 3rd harmonics.

The Harmonic Distortion plot in Fig 9 is of the Kingfisher. My interest in this measurement is the distortion below 250Hz. Though there is a slight rise in the 3rd harmonics at about 150Hz, it falls off as the frequency lowers. This shows the high pass in the FE85 is doing it’s job in preventing the FE85 from over-excursion. Higher up, there is a slight rise in 2nd harmonics at 1kHz. Since these are even harmonics, they will not interfere with your listening pleasure. Furthermore, they are -40dB below the fundamental. I doubt my ears are that good.

Step Response

STEP RESPONSE KINGFISHERFig 10 – Step Response of Kingfisher. (Courtesy of REW)

Fig 10 is the Step Response of the Kingfisher. Frankly, I’m impressed. I didn’t expect this. The transient response of the FE85 is almost vertical, meaning “fast”. The small negative dip at the start indicates the DX20BF00-04 and the FE85 are quite close to being time aligned. The W20RC38-08 Silver Flute woofer is not too shabby. It peaks at 1.5 msec before decaying off.

For comparison, Stereophile’s Step Response of the B&W Matrix 801 is in Fig 11 below.

B&W MATRIX 801 STEP RESPONSEFig 11 – B&W Matrix 801 Step Response. (Courtesy of Stereophile).

Excess Group Delay
excess group delay KINGFISHER

Fig 12 – Kingfisher Excess Group Delay. No smoothing. (Courtesy of REW)

The Excess Group Delay in Fig 12 shows there’s no delay in the bass region (below 100Hz). A sharp peak is recorded at about 160Hz. This corresponds to the deep notch seen in Fig 3. As for the smaller peak at 350Hz, I can only speculate it’s from the crossover of the Silver Flute W20RC38-08 and the Fountek FE85.

Auditioning the Kingfisher

I have been listening to the Kingfisher for a few days and I must say I’m very pleased with the sound quality. I find it exceptionally soothing. I did not experience any listening fatigue even in prolong sessions.

The tonal balance of the Kingfisher is very appealing to most listeners. Being a 3-way, there is ample bass from the 8″ Silver Flute W20RC38-08. More importantly, it doesn’t bleed into the mids. The Fountek FE85 performs spectacularly from 250Hz ~ 2.5kHz. The midrange is clear and free from any annoying peaks in the response. Difficult vocals like Dionne Warwick, Nana Mouskouri and Jewel are a joy with the Kingfisher. In Stronger Woman (Perfectly Clear Album), the close miking recorded Jewel’s breathing and it came across without any excessive sibilance. As for the Peerless DX20BF00-04 tweeter, it’s invisible. When I do hear it, the cymbals don’t sound like screeching glass.

Can the Kingfisher play bass tracks? Most certainly. The Kingfisher has no problem pumping bass in Fourplay, Jamie Valle and even Bela Fleck. I do not recommend the Kingfisher in small rooms. The room gain will cause havoc.

Fig 13 below is the Kingfisher RT60 plot in my lab of 20’x16′. Almost all the frequencies are below 300 msec. This indicates the reflections are not causing any echoes. Below 70Hz, the decay is about 500 msec. I can expect a bit of “bloom” in the low bass due to the longer decay. Overall, not too bad for an untreated room.

KINGFISHER RT60Fig 13 – Kingfisher RT60. (Courtesy of REW)

Kingfisher System

Presently, the miniature SuperMicro box is meant to sit on top of the Silver Flute W20RC38-08 bass reflex box similar to the B&W Matrix 801. If required, the SuperMicro can be used as satellites with the 8″ Silver Flute box placed somewhere else but one needs to be imaginative because there’s no space inside the SuperMicro box for the crossover.

Crossover Values & Box Dimensions

If you’re interested to build this project, kindly send me a mail for the crossover and box dimensions. Free for DIY only. Not for commercial use.

Note: Unless otherwise stated, all measurements were made with the mic at 36 ins, tweeter axis. Impulse Window=5ms. No smoothing applied.