The Grosbeak-TBFC is a bass reflex version of the 40 liters Dual Chamber Grosbeak-DCR. I had to re-work the crossover because simply transplanting the DCR crossover did not work. From the outset, this speaker is for bass.
Fig 1 – Black plot=835025 RAW • Blue plot=with Low Pass Filter (LPF)
The Black plot in Fig 1 is the RAW response of the Peerless 835025 in this 27 liters box with a baffle width of 9-1/2″. Disregard the notch at 150Hz. It’s caused by a floor bounce in my setup.
I’m not slicing in a nearfield measurement because I need to see the bass relative to the midrange. The Blue plot is the final response of the 835025 with a low pass network. Note the midrange is a couple of dBs less than the bass.
Fig 2 – Black plot=27TBFC RAW response • Red plot=with High Pass network
The Black plot in Fig 2 is the RAW response of the Seas 27TBFC. The Red plot is with my High Pass network.
Fig 3 – 835025 Low Pass • Seas 27TBFC High Pass
Fig 3 shows the plots of the 835025 and the 27TBFC with their respective networks. The two drivers are crossing at 1.7kHz.
Fig 4 – Grosbeak-TBFC Passband
The Black plot in Fig 4 is the summation of the crossover. No cancellations are seen in the passband which is an indication of optimal crossover phasing. It’s encouraging to see the peak at 7kHz from the 835025 is not causing issues in the treble.
Fig 5 – Grosbeak-TBFC Frequency Response
Fig 5 is the final frequency response of the Grosbeak-TBFC. After summation, the midrange remains slightly lower than the bass. When compared to the Grosbeak-DCR, this Grosbeak-TBFC response is actually flatter.
Fig 6 – Grosbeak-TBFC Null
Fig 6 is the null when I flipped the tweeter wires around. It centers at 1.7khz, exactly where the two drivers are crossing in Fig 3. The null depicts excellent symmetry, inferring that the crossover slopes of the woofer and the tweeter are similar. Furthermore, it shows a healthy depth, indicating the speaker is almost time-aligned.
Fig 7 – Grosbeak-TBFC Step Response
No anomaly is seen in the Step response in Fig 7. The Grosbeak-TBFC exhibits a clean transient followed by a natural decay.
Fig 8 – Grosbeak-TBFC Waterfall
Fig 9 – Grosbeak-TBFC Toneburst Energy Storage
The Waterfall (Fig 8) and Toneburst plot (Fig 9) show the Grosbeak-TBFC has some excess energy at 6kHz. I doubt this will cause harshness in the treble.
Fig 10 – Grosbeak-TBFC Spectrogram
The Spectrogram in Fig 10 verifies the excess energy at 6kHz is insignificant. Whatever hotness there is fully dissipated by 1 msec. There are some delayed hot spots at 2.1kHz but they are dissipated by 5 msec.
Sound of Grosbeak-TBFC
Though the Raven-TBFC is good, this Grosbeak-TBFC is even better. It all has to do with the bass. The Peerless 835025 excels in this department. The articulation in the bass is superior to the Dayton RS180s-8.
It’s a joy listening to Donna Summer. In She Works Hard for the Money, the beat is tight and punchy. Likewise for No More Tears (Enough is Enough). It’s not difficult to see why she’s known as the Queen of Disco. She had an amazing voice. It’s tragic that she passed away at only 63 in 2012.
Bass is an exceptionally difficult segment of the music spectrum to produce properly. What I strive for is articulation, clarity, attack and texture. The Scanspeak 15WU and the Seas U18RNX are two woofers I tested that can do all these. But they cost more, particularly the Scanspeak 15WU. At $58, the Peerless 835025 is obviously not in the same class but in that price bracket, she’s a winner.
Crossover is available on request. Free for DIY. Not for Commercial use.
January 21, 2021Projects