Myna-DXT (Seas U18RNX/P with 27TBCD/GB-DXT)


The Myna-DXT brings together two excellent drivers by Seas, the U18RNX midwoofer and the 27TBCD/GB-DXT tweeter. I tested out the U18 in the Myna which was sporting a Morel MDT29. The DXT tweeter, on the other hand, was mated with a Scanspeak PL18WO-06-08 midwoofer in the Goldfinch-DXT. These two projects gave me an intimate feel of what the U18 and the DXT are capable of.

In the Myna-DXT, I will be using them at their best. In the U18, I intend to focus on the bass and the lower midrange. The DXT tweeter will take over after that. I’m expecting a lot out of the DXT because the crossover frequency is 1.5kHz. That will allow the U18 and the DXT to shine.

Now that I’ve explained my design objective, I will proceed with the U18RNX first. 

Fig 1 – Seas U18RNX/P RAW response • Baffle Width=8.75″

Fig 1 is the RAW response of the U18 in a 15 liters bass reflex. Measurements below 500Hz includes my room reflection. Disregard the deep suck-out at 150Hz. That’s an anomaly caused by a floor bounce.

We can see the response rising from 400Hz. That’s caused by the baffle step. The wonderful part with this driver is she maintains a flat response to 4kHz. After that, she rolls off gracefully. No violent peaks and all that.

Fig 2 – Seas U18RNX/P with Low Pass network.

The Blue plot in Fig 2 is the U18 with a 2nd Order Low Pass Filter (LPF). This is a very delicate response because I want the midrange (600Hz) to be slightly higher than the bass (100Hz to 60Hz). Too high and I lose the bass. Too low and the bass will overwhelm the midrange. The resultant response was actually tuned by ear, then I took the measurement.

Fig 3 – Seas U18RNX with 27TBCD/GB-DXT

The Red plot in Fig 3 is the DXT tweeter crossing over to the U18 at exactly 1.5kHz. It would have been nice if the top octaves didn’t roll-off at 8kHz but I can’t prevent that. Fortunately, there’s not much information up there and it’s not as though it falls like a cliff. 

Fig 4 – Myna-DXT Crossover Passband

The Black plot in Fig 4 is the summation of the U18 and the DXT. It looks promising because no cancellations are in the passband.

Fig 5 – Myna-DXT Frequency Response

The final frequency response of the Myna-DXT is in Fig 5. It is flat within +/- 2.5dB from 500Hz to 9kHz. There is a small dip at about 3kHz which is caused by baffle edge diffraction. Rounding the edges or chamfering them may get rid of it.

Fig 6 – Myna-DXT Null

I got a beautiful null (Violet plot in Fig 6) at exactly 1.5kHz when I flipped the DXT wires. It indicates excellent phase alignment of the U18 and the DXT.

Fig 7 – Myna-DXT Step Response

The U18 shows a very clean transient Fig 7). There are no breaks anywhere. The transient is largely linear until at 80% where it slows down slightly, hitting the apex at 400 microsec.

Fig 8 – Myna-DXT Waterfall

The Waterfall plot (Fig 8) shows minimal artifacts in the treble. 

Fig 9 – Myna-DXT Toneburst Energy Storage

Wow, this is one of the cleanest Toneburst plot (Fig 9) I’ve ever seen in a 6-1/2″ 2-way.

Fig 10 – Myna-DXT Spectrogram

The Spectrogram (Fig 10) shows only one hotness at 1.1kHz. It is very slight, -50dB at 3 msec. There are two minor spots at 2kHz and 2.3kHz but they are fully dissipated by 5 msec. By and large, these are pretty impressive measurements.

Fig 11 – Myna-DXT Distortion

The Total Harmonic Distortion (Blue plot in Fig 11) is -50dB below the fundamental. The 2nd (Red plot) and 3rd (Violet plot) harmonics are about -55dB

Sound of Myna-DXT

The Myna-DXT sounds fabulous. The bass is awesome. Dynamic, Clear and Textured. They are all there. The bass shares the same characteristics as the Scanspeak 15WU that I used in the Enlightenment.

The vocals are exceptionally clear. There’s no muddiness from the bass that cast a veil over the midrange. Voices are well isolated. Male voices don’t sound nasal. Females voices no shrieking.

Lastly, the treble. This is where the DXT blows away the competition. I’ve never heard anything like this before. There’s depth and layering. An incredible tweeter.

If you want top quality, the Myna-DXT is the one. The drivers cost more than your run of the mill ones but considering their performance, they are well worth it. We are looking at High-End here. In that respect, their prices are actually very reasonable.

Crossover is available on request. Free for DIY. Not for Commercial use.
Unless otherwise stated, all measurements were made with the mic at 36 ins, tweeter axis. Impulse Window=5ms. No smoothing applied.