Update – May 21, 2018
The Crow Bandpass Subwoofer can be used with the normal Unshielded Silver Flute W17RC38-08. The Red plot above is with the Unshielded W17. There’s not much difference with the shielded version (Blue plot).
Crow
The Crow is a bandpass subwoofer using a magnetically shielded Silver Flute W17RC38-08 6.5″ woofer. This 25 liters subwoofer is a slim tower standing 23.5″ tall. I deliberately designed it this way so that they can be used as speaker stands for compact 2-ways. If desired, they can also double up as pedestals for flower pots.
Fig 1 – Crow Bandpass Box Dimensions. Material: 3/4″ MDF or Plywood.
Download ZIP CROW PLANS
Crow Frequency Response
 Fig 2 – Crow RAW and with 250Hz Low Pass Frequency Response
Mic at mouth of port, Impulse Window=5ms, 1/24th octave smoothing.
The Black plot in Fig 2 is the RAW response of the Crow made with the mic at the mouth of the port. The bandwidth is approximately from 40Hz~125Hz (-3dB). Note the series of resonant peaks after 500Hz.
The Blue plot is with an external 24dB/oct Linkwitz/Riley active crossover with the Low Pass filter set at 250Hz. This additional filter is mandatory as it completely eliminates the destructive resonant peaks.
Setting Up the Crow
Fig 3 – Crow with SuperMicro in Tri-Amped System
For convenience, I setup the Crow in a Tri-Amped system. An electronic crossover is set to 250Hz Low Pass and the signal is fed to a power amplifier. That takes care of the bass.
The SuperMicros at the top are powered by a pair of Synergy Bi-Amp units. Their internal 18dB/oct crossovers are set for 3kHz. Tweeters are the Peerless BC25SC08-04. Woofers are the Tang Band Full Range W3-1364SA.
 Fig 4 – Crow and SuperMicro Frequency Response. SuperMicro crossed at 3kHz @ 18dB/oct.
Fig 4 shows the frequency responses of Crow Bandpass (Blue plot) and the SuperMicro (Black plot). They cross at about 130Hz. The high pass seen in the SuperMicro is the natural roll-off of the W3-1364SA in a sealed box.
Listening Impressions
I was stunned by what I heard. The system is crystal clear with great bass definition and dynamics thanks to the Crow. The additional 24dB/oct to cut off the resonances in the Crow’s low pass made a world of difference. Vocals are transparent and not muddied by the Crow.
As for the SuperMicro, the clarity continues to impress me. I did a Toneburst Energy Storage sweep of the SupeMiicro and true enough, there were very little artifacts.
The sound quality of the Crow with the SuperMicro easily exceeds speakers costing 1K. Simply amazing, considering the low cost.
 Fig 5 – SuperMicro Toneburst Energy Storage. Impulse Window = 5 ms. Mic at 36 ins, Tweeter axis.
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Fig 2 – Crow RAW and with 250Hz Low Pass Frequency Response
Fig 4 – Crow and SuperMicro Frequency Response. SuperMicro crossed at 3kHz @ 18dB/oct.
Fig 5 – SuperMicro Toneburst Energy Storage. Impulse Window = 5 ms. Mic at 36 ins, Tweeter axis.