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Grosbeak-DCR The majority of my work is based on getting a flat response. While it’s important for studio monitors, many of us find listening to such speakers too “dry” or “clinical”. In this Grosbeak-DCR, I tuned it for music. Obviously, the response is not as flat as my other speakers but it’s more than that. I want bass. And I want the bass to be loud, dynamic and possess a fast attack. Combine all three and you get what I call “punch”. This is the most important aspect. Lose that and you won’t get drawn into the music. It is therefore crucial to find the right woofer that can do these. The Peerless 835025 is one such driver. I first tested out this woofer in the Grosbeak. The crossover was fine but the bass was completely wrong. Later, I installed it in the same Dual Chamber Reflex (DCR) that I used in the Cardinal-TBFC-DCR. Played some music without any crossover and discovered that this woofer works better for music. That set the direction in the development of the Grosbeak-DCR.
Fig 1 is the RAW response of the 835025 in a DCR with a Baffle Width of 9″. Disregard the deep notch at 150Hz. That’s caused by a floor bounce in my setup. The response of the 835025 is very different from the 830874. This woofer starts to taper down at about 1.5kHz. At 7kHz, there’s a cone breakup peak.
After much adjustments by ear, I finally settled on the Blue plot in Fig 2. What is most striking with this response is how low my midrange is when compared to the bass. Furthermore, in choosing a low crossover frequency, the 7kHz peak is now attenuated by 25dB.
I made some adjustments to the 27TBFC crossover (Red plot) to accommodate the 835025. Fig 3 shows the two drivers are crossing at 1.8kHz.
The Black plot in Fig 4 is the passband of the Grosbeak-DCR. No cancellations are observed in the passband which is an indication of good summing.
The final frequency response of the Grosbeak-DCR is in Fig 5. In this response, the bass is louder than the midrange. Higher up in the lower treble (2kHz), there is a slight de-emphasis. At 12kHz, it is about 1dB more than the midrange. This response curve mimics my hearing. It is not suitable for audio mixing but in listening to program music, I find it’s more pleasant.
The Violet plot in Fig 6 is the Null when I flipped the tweeter’s wires around. The null is fairly deep, centered at 1.8kHz which indicates the phasing of the two drivers are quite close.
The Grosbeak-DCR Step response (Fig 7) doesn’t show any anomaly. The transient is actually very smooth and linear up to 90%. After that, the woofer slows down slightly, hitting the apex at 400 microsec. What is interesting is it has a very natural decay after the peak.
The Waterfall plot (Fig 8) shows minimal artifacts in the treble. There may be some excess energy decay down at about 1kHz but it’s hard to tell .
Yes, the Toneburst plot (Fig 9) recorded some excess energy at 1kHz to 2kHz. These are the ones that can smear the midrange. There are more excess energy higher up the spectrum but they die off early.
The Spectrogram (Fig 10) shows some energy bleeding out at 1.2kHz. This is not serious as it is dissipated by 7 msec. There is a hot spot at 2.8kHz which I cannot account for. It’s not from the drivers nor the crossover. Fortunately, it vanished by 6 msec. Sound of Grosbeak-DCRI am glad I decided to tune the Grosbeak-DCR for music. She would not have worked had I gone for a flat response. This is what the Peerless 835025 is good at and I let her fly. Believe it or not, she punches. But it’s not just in the bass that the Grosbeak-DCR impresses. Her midrange is quite well isolated, so vocals can still be clearly heard. The Seas tweeter performs flawlessly throughout. Ever notice how some speakers sound hard or harsh when you crank up the volume. You won’t get that with this Seas 27TBFC. She maintained her composure. The hallmark of a good speaker is it makes you want to dance. That is precisely what the Grosbeak-DCR does. This is one speaker I highly recommend. You won’t be disappointed. Unless otherwise stated, all measurements were made with the mic at 36 ins, tweeter axis. Impulse Window=5ms. No smoothing applied. |
December 28, 2020HIFI DRIVERS, Projects
Fig 1 – Peerless 835025 RAW response in 40 L DCR
Fig 2 – Peerless 835025 with Low Pass Filter (LPF)
Fig 3 – 835025 Low Pass with 27TBFC High Pass
Fig 4 – Grosbeak-DCR Passband
Fig 5 – Grosbeak-DCR Frequency Response
Fig 6 – Grosbeak-DCR Null
Fig 7 – Grosbeak-DCR Step Response
Fig 8 – Grosbeak-DCR Waterfall
Fig 9 – Grosbeak-DCR Toneburst Energy Storage
Fig 10 – Grosbeak-DCR Spectrogram