Selenium ST200 Super Tweeter
The ST200 is a $20 budget super tweeter by Selenium. As in all Selenium products, it’s intended for the pro sound market. According to their specs, the ST200 is rated at 140W Musical Program when crossed at 5,000Hz (12dB/oct). The Frequency Response at -6dB is from 2kHz~20kHz. Dispersion pattern is 40° conical and comes with a phenolic diaphragm.
Fig 1 – Selenium ST200 Impedance
Fig 1 is the Impedance sweep of the Selenium ST200. Resonant frequency (Fs) is a rather high 3kHz. The impedance peak at Fs looks well damped which is an advantage. Lowest impedance is 7Ω at 5kHz.
Fig 2 – Selenium ST200 RAW Frequency Response.
Fig 3 – Expanded view of Selenium ST200 Frequency Response
Fig 3 shows a fairly flat frequency response from 3kHz~10kHz. Beyond that, it rolls off linearly to about 17kHz at -15dB.
Even though Selenium recommends crossing at 5kHz at 12dB/oct, I think it’ll be fine at 4kHz with 18dB/oct. If one wants to push it, it can go to 3kHz at 24dB/oct. Below 3kHz, the horn cuts off. This, of course, depends on how much power one expects the ST200 to take.
Fig 4 – REW Waterfall of Selenium ST200. Rise Time = 0.10 msec. Window = 1.3 msec ( 769Hz ). Time Range = 1.0 msec
The highly magnified (1ms) Waterfall plot in Fig 4 shows minimal artifacts from 5kHz onwards. It looks like a very “clean” tweeter.
Fig 5 – Toneburst Energy Storage of Selenium ST200
The Toneburst Energy Storage plot In Fig 5 shows stored energy (light blue slices) from 3kHz~6kHz. It’s not critical because they last for only 10 cycles at most.
Fig 6 – Spectrogram of Selenium ST200
The Spectrogram in Fig 6 gives us a better idea of the stored energy. It is at 3kHz where the stored energy is most. This frequency also happens to be the Fs of the ST200.
Selenium did a remarkable job with the ST200. The flat frequency response alone is worth more than $20.
Even though the ST200 is meant for the PA market, there’s no reason why it cannot be used for HiFi or Home Theater.
Note: All measurements were made with the mic at 1m, tweeter axis. Impulse Window=5ms. No smoothing applied.