Peerless GBS85N with Audiopur PLA114-6

Peerless GBS85N25PR03-04 with AudioPur PLA114-6
Active Bi-Amped

The objective of this exercise is to see how well the Peerless GBS85 integrates with the AudioPur PLA114. My reason for choosing these two rests solely on the GBS85. Due to its shallow mount design, the acoustic center is nearer to the frame than conventional drivers. With this unique feature, I am hoping to time-align the AudioPur without much trouble. It’s also an opportunity to listen to the AudioPur Ribbon as I’ve not heard it before.

After much measurements, I found that the drivers’ acoustic centers are still not close enough. In a moment of inspiration, I lifted the front of the box by 1″ and “Voila” everything fell into place. The two drivers’ acoustic centers aligned. All the measurements below are with the box lifted by 1″, with the microphone axis between the GBS85 and the AudioPur.

Fig 1 – Blue plot=Peerless GBS85 • Red plot= AudioPur PLA114

The Blue plot in Fig 1 is the Peerless GBS85 with my 24dB/oct (LR) crossover at 90Hz and 3.4kHz. The Red plot is the AudioPur PLA114 at 3.4kHz high pass.

Fig 2 – Black plot=Summed Response

Fig 2 shows the summed response of the GBS85 with the AudioPur PLA114. Note that there are no cancellations in the crossover passband. This indicates good summing properties of the two drivers.

Fig 3 – Null Response

The Violet plot in Fig 3 is with the AudioPur PLA114 in reversed phase. The depth and symmetry of the null indicates the two drivers’ phases at 3.4kHz are aligned.

Fig 4 – Summed Response

For clarity, I removed the plots of the GBS85 and the AudioPur PLA114. The Black plot (Fig 4) is the summed response of the two drivers. Disregard the measurements below 500Hz as they include room reflections. 

Fig 5 – Waterfall

Fig 6 – Toneburst Energy Storage

The Waterfall (Fig 5) and the Toneburst (Fig 6) plots show some artifacts in the treble. They are quite inaudible as they are about -30dB at 1.5 msec. 

Fig 7 – Spectrogram

The Spectrogram in Fig 7 shows the treble to be clean. It is at 1kHz~1.5kHz that we see some hotness at 4.5 msec. They are mostly dissipated by 10msec.

Fig 8 – Step Response

The Step response in Fig 8 shows how close the GBS85 and the AudioPur are. Even though they are aligned in phase, the step shows the AudioPur reaches the microphone first. This is followed by the GBS85 in less than 100usec. This is a very good step for a 24dB/oct crossover.

Fig 9 – Summed Response with Albatross Bandpass Sub

To complete the speaker, I integrated in the Albatross Bandpass Subwoofer. The Black plot in Fig 9 shows the bass extending to 40Hz. Disregard the notch at about 130Hz. It’s an anomaly caused by a floor bounce.

Auditioning the System

Having listened to the speaker for a few days, I’m quite pleased with the sound of the GBS85 and the AudioPur. I like the GBS in that it doesn’t shout at you. Though it is flat, it doesn’t sound sterile. In fact, there’s some vocal presence even though the crossover is at a highish 3.4kHz.

The AudioPur is another surprise. I expected it to sound like my HiVi RT1C but it is anything but that. It veers more towards my AMT tweeter. It has a bit of brightness that reminds me of some titanium compression drivers. As for the crossover point, I tried it at 2.6kHz earlier but it didn’t sound quite right. It appears that 3.4kHz is the optimal frequency for a 24dB/oct slope.

For the bass, I tested a few 8″, namely the Peerless 830869, the Silver Flute W20RC38-08 and the Dayton DA215-8, all in bass reflex loading. The main issue I have is with the sensitivity. The GBS85 needs to be padded down by -6dB to match the bass. This means that I will need to parallel two woofers to get the bass SPL to match the GBS85.

The Albatross, on the other hand, is only -3dB. The penalty for using the Albatross is I have to cross the GBS85 at 90Hz because that’s the highest the Albatross can go. Frankly, I am not comfortable crossing the GBS85 at such a low frequency. My preference is at 250Hz. That’s where using bass reflexes have the upper hand.

In an active system, sensitivity is seldom a problem because the gain is adjustable for individual drivers. However, that is not the case when it’s passive. All things considered, it looks like I’ll have to use two 8″ woofers in parallel for a passive design. I will start off with two Peerless 830869. It’s a gross overkill using the 830869 but since I already have two units in hand, why not. I’ve always wanted to hear how two 830869 sound like.

Unless otherwise stated, all measurements were made with the mic at 36 ins, tweeter axis. Impulse Window=5ms. No smoothing applied.