Thruster THW835 with Peerless GBS85N (Pt1)

Blending in a Midrange
Active 2-way

I was very tempted to use the Solitaire to marry with the Thruster THW835 but it was too much of a cost mismatch. The Peerless 830870 is one of my favorite midrange drivers but it’s cost is almost double that of the THW835. I prefer a driver that is about $20 and I found a dome midrange that I’ve worked on before, a Peerless GBS-85N25PR03-04 that I used in the Swallow-TPC.

Fig 1 – Peerless GBS-85N25PR03-04 Response with 300Hz HP (24dB/oct)

Fig 1 is the response of the GBS85N with a 300Hz 24dB/oct High Pass from my electronic crossover. The roll-off is very effective at 300Hz. It kept the bass out of the midrange. Bear in mind that this GBS85N is rated for 15W only. Keeping the bass away will prevent the midrange from distorting early.

From the plot, we can see the GBS85N starts to climb at 4kHz. This is the beginning of the cone breakup. The first peak is at 5kHz, followed by a smaller peak at 8.5kHz and a final one at 17kHz.

Fig 2 – Peerless GBS-85N25PR03-04 Wavelet • Baffle Width=8″

Fig 2 is the Wavelet of the Peerless GBS-85N. The cone breakup at 5kHz is clearly visible. Fortunately, it doesn’t last long, about 1.5msec.

Fig 3 – Peerless GBS-85N25PR03-04 Waterfall

The Waterfall plot in Fig 3 is a 3-D view of the response. The peaks at 5kHz and 17kHz are seen. There’s even one at 20kHz. I wouldn’t be too concerned because they dissipate by 1 msec.

Fig 4 – Peerless GBS-85N25PR03-04 ToneBurst Energy Storage

The Toneburst plot in Fig 4 is another  3-D view of the response but this time, the z-axis is in cycles. The light blue slices are the unwanted stored energy. There’s bunch at 5kHz, which is where the peak is. They are not harmful because they last about 5 cycles only.

Fig 5 – Peerless GBS-85N25PR03-04 Distortion

Fig 5 is the Harmonic Distortion of the Peerless GBS85N. The 2nd Harmonic is at 0.345% while the 3rd is at 0.490%. The total harmonics from H2~H9 is rather high at 4.75%. However, during auditioning, I couldn’t pick up any issues in the midrange.

Fig 6 – Thruster THW835 with Peerless GBS-85N25PR03-04 crossed at 300Hz

Fig 6 are the plots of the Thruster and the Peerless GBS85N crossed at 300Hz at 24dB/oct. With this steep slope, the Thruster is kept well away from the midrange. This is important as it enhances the clarity of the midrange.

Fig 7 – Thruster THW835 with Peerless GBS-85N25PR03-04 Frequency Response

The final response of the Thruster with the Peerless GBS85N dome midrange is in Fig 7. I adjusted the bass to be at the same level as the midrange to avoid muddying the vocals. The dip at 150Hz is nothing to worry about. It’s an anomaly that’s caused by a floor bounce in my measuring setup.

Sound of Thruster with Peerless GBS85N

For this audition, I’m listening to the Thruster with the GBS85N only (Fig 7). What I want to determine is the quality of the midrange.

I started off with male singers. This will flag me any issues in the lower midrange. “Memories Are Made Of This” by Dean Martin came out perfectly. There’s no nasalness in his voice.

Willie Nelson’s “Always On My Mind” is heartrending. It sounded like he is addressing your soul.

While testing the Dayton PA200 a few years ago, Glenn Frey sounded “hard” at certain passages in the Eagles “Doolin-Dalton”. That’s caused by a bump at 700Hz in the response. With this GBS85N, it’s smooth throughout.

In Summary

The Peerless GBS-85N is a good match for the Thruster THW835. Vocals came out clearly and wasn’t “shouty”. It would not be an issue integrating in a tweeter after this.

The GBS85N can be used on it’s own without a tweeter but I don’t recommend it for demanding listeners. The treble sounds slightly “metallic”. I picked this up in “Lyin’ Eyes” (Eagles).

As for the bass, the Thruster performed exceedingly well even crossing at 300Hz. Bass is clear and doesn’t muddy the vocals.

A word of caution. The Thruster sensitivity is higher than the GBS85N. It’s not an issue for active systems but the GBS85N is not a good match for a passive crossover. For that, a higher sensitivity midrange is needed.

NEXT> Blending in the Tweeter

Unless otherwise stated, all measurements were made in Full Space (4 pi) with the mic at 36 ins, tweeter axis. Impulse Window=5ms. No smoothing applied.