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Scanspeak PL18WO-06-08 The Goldfinch is based on the Scanspeak PL18WO-06-08 that is no longer in production. I happened to chance upon them at Parts Express and immediately bought a pair. Apparently this woofer was used in the Aerial Model 5 or 5B. It would be interesting to see how superior they are over my vintage Vifa Premium Line PL18WO-09-08.
The Black plot in Fig 1 is the RAW response of the Scanspeak PL18 in a 15 liters ported box with a baffle width of 9″. The response look remarkably similar to the Vifa PL18. It has a beautiful flat response that extends up to 4kHz before rolling off. This woofer is crying out for a 1st order network.
The Blue plot in Fig 2 is the Scanspeak PL18WO with a 1st order network The Red plot is the Peerless H26TG45-06. I opted for this tweeter because it is one of the few tweeters I have that is quite happy with a 1st order filter.
The Black plot in Fig 3 shows the summing of the two drivers. For a 1st order network, both drivers are summing pretty well. No cancellations are observed in the passband.
The plot in Fig 4 is the final frequency response of the Goldfinch. It is incredibly flat from 1kHz upwards. Measurements below 500Hz are in nearfield. No smoothing applied from 500Hz to 20kHz.
The Violet plot in Fig 5 is the null response of the Goldfinch. The notch is not as deep as I would like it to be but considering that this is a 1st order network, it is quite acceptable.
To check on the bass, I included the in-room response below 500Hz. This measurement is no longer quasi-anechoic. It includes reflections of my room. What I want to see is the bass response in real live situations. Disregard the huge notch at 150Hz. That’s caused by a floor bounce in my setup. The area I’m interested in is from 100Hz downwards. My baffle step compensation is just about right because the bass spl is almost level with the midrange.
The Red plot in Fig 7 is the frequency response of the Aerial 5B by Stereophile. Note the +5dB increase at 500Hz. It appears that no baffle step compensation was used in the Aerial 5B. This results in a prominent midrange. To compensate for this, the Aerial 5B box alignment is under-damped. Note the +6dB peak at about 130Hz. This is a closed box Q (Qtc) of about 1. In using such a high Q, the tonal balance is restored somewhat. In fact, gives the impression that the Aerial 5B has good bass for a small box. The penalty for such an approach is the degraded transient from an under-damped alignment. The bass may sound louder but it won’t sound tight and well defined.
The Goldfinch Step response (Fig 8) shows the Scanspeak PL18WO is exceptionally fast for its size. The transient is almost vertical until the 65% mark where it slowed down slightly. There seem to be a bit of a confusion at the apex which I can’t account for.
Fig 8 is the Step response of the Aerial 5B. Notice their woofer’s transient is markedly slower when compared to the Goldfinch (Fig 8). I believe this is due to using higher order filters in their crossover, possibly 2nd order networks.
The Goldfinch Waterfall and Toneburst plots don’t show any anomalies. What is a slight concern is the excess energy at about 1kHz.
The Spectrogram in Fig 12 shows a very light smearing at 1kHz. Though it’s recorded, it is inaudible because it dissipated by 5 msec. After 1kHz, the response is very clean.
The Goldfinch Impedance (Fig 13) is generally quite friendly. It dips to 4Ω at 10kHz but I did not encounter any issues with my amplifier during auditioning. From the saddle below 100Hz, we can see the Goldfinch is a bass reflex tuned to 35Hz. Sound of the GoldfinchThere are very few 2-ways I’m truly satisfied with and I’ve done a lot of 2-ways. One is the Enlightenment. The other is this Goldfinch. What sets them apart from the rest is the high quality of the Scanspeak woofers. The bass in the Goldfinch is so distinct that you would think it’s a 3-way. But it’s more than just the separation of the bass from the midrange. It is the character of the bass that is outstanding too. It’s incredibly dynamic, fast and full of body. Not muddy and lethargic like in most average drivers. This is what high-end drivers sound like. Undoubtedly, many will wonder the differences between the Goldfinch and the Aerial 5B. Like I mentioned earlier, I’ve never heard the Aerials before but judging from the measurements from Stereophile, I can make some fairly accurate assumptions. Putting aside the crossover and the tweeter, the most obviously difference you’ll hear is in the bass. The Aerial 5B is a closed box with a high Q, under-damped alignment. The Goldfinch, on the other hand, is a bass reflex with an over-damped alignment. Bass is therefore tighter and deeper. Lastly, for the best bass performance, I strongly recommend using 24″ speaker stands. Taller than this and you risk compromising the bass. Unless otherwise stated, all measurements were made with the mic at 36 ins, tweeter axis. Impulse Window=5ms. No smoothing applied. |
September 12, 2020HIFI DRIVERS, Projects
Fig 1 – Scanspeak PL18WO-06-08 RAW Response. Baffle Width=9″
Fig 3 – Crossover Passband
Fig 4 – Goldfinch Frequency Response. 500Hz and below in Nearfield.
Fig 5 – Null Response
Fig 6 – Bass Response
Fig 7 – Aerial 5B Frequency Response
Fig 8 – Step Response
Fig 9 – Aerial 5B Step Response
Fig 10 – Waterfall
Fig 11 – Toneburst Energy Storage
Fig 12 – Spectrogram
Fig 13 – Goldfinch Impedance