Hawk-XT3 (the Final Cut)


The Hawk-XT3 is the final version using the HiVi L6-4R with the Peerless XT25TG30-04 ring radiator tweeter. In the XT3, I tuned the Hawk to include the bass. Because of that, the Hawk-XT3 needs plenty of breathing space. She is not recommended for small rooms. The ideal placement is a minimum of 3 feet away from the back and side walls.

Fig 1 – HiVi L6-4R RAW Response

Let’s have another look at the HiVi L6-4R woofer again. This plot (Fig 1) is the woofer mounted in a bass reflex box with a baffle with of 8-1/2″. Measurements below 500Hz include reflections in my room. Disregard the deep notch at 150Hz. That’s caused by a floor bounce in my setup.

In this plot, we can see the effects of baffle step, manifesting in the rising response at 400Hz. The midrange and lower treble is about 87dB where the bass is at 82dB. That’s a good 5dB difference.

Fig 2 – L6-4R with Low Pass Filter (LPF) • XT25TG30-04 with High Pass Filter (HPF)

The Blue plot in Fig 2 is the L6-4R with a new network taking bass into consideration. This response is actually determined by ear and the plot made after that.

Fig 3 – Hawk-XT3 Passband

The Black plot (Fig 3) is the summation of the the two drivers. There are no cancellations in the passband which is encouraging.  

Fig 4 –  Hawk-XT3 Frequency Response

Fig 4 is the final frequency response of the Hawk-XT3. It appears that the bass is too strong but during auditioning, it sounds perfect. We cannot blindly follow the measurements. 

Fig 5 – Hawk-XT3 Null

The Null in the Hawk-XT3 is quite deep. This indicates the phasing of the L6-4R and the XT25 are very close. For all intents and purposes, we can consider them to be time-aligned.

Fig 6 – Hawk-XT3 Step Response

The Hawk-XT3 is not as fast as some of the other 6-1/2″ woofer that I have. This doesn’t mean it sounds “slow”. The L6-4R exhibits slight hesitation during take-off but is completely clean after that, hitting the apex at 400 microsec (Fig 6).

Fig 7 – Hawk-XT3 Waterfall

The Waterfall plot reveals minimal artifacts in the treble. There is some excess energy at 3kHz but it won’t affect the sound.

Fig 8 – Hawk-XT3 Toneburst Energy Storage

The Toneburst plot (Fig 8) shows almost no excess energy at 1kHz to 1.5kHz. The light blue slices are all above 2kHz, so they are not harmfull.

Fig 9 – Hawk-XT3 Spectrogram

The Spectrogram shows the Hawk-XT3 free of smearing. There is a bit of streaking at 1.1kHz but is soon dissipated by 6 msec. There is a small delayed hot spot at about 2.8kHz. That comes from the cone breakup of the L6-4R but it is completely gone by 6 msec.

Sound of Hawk-XT3

Of all the Hawks, this is the one you want to build. With the bass brought up, the Hawk sounds more musical. But it’s not simply the bass loudness. I shaped the bass for clarity and dynamics. With that, the tempo of the bass matches the midrange.

Owners of the L6-4R will know that the woofer’s outstanding feature is the midrange. In the XT3, I made sure the midrange is not compromised in the pursuit of bass. Vocals remain crystal clear.

To those who are interested in building the Hawk-XT3, be warned that the crossover has a high component count. This is not a minimalist design.

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.