G1 Studio Monitor
The G1 is a 2-way, 18 liter bass reflex designed for studio monitoring. She features an incredibly flat response that is crucial in sound mixing.
Fig 1 – G1 Frequency Response • Nearfield below 500Hz
Fig 1 is the on-axis response of the G1. Measurements below 500Hz are in nearfield. The response lies within a +/- 2.5dB window from 500Hz to 15kHz.
Fig 2 – G1 RAW Frequency Response • Baffle Width=9-1/2″
To see the actual G1 bass, I superimposed the in-room response below 500Hz (Fig 2). The Black plot below 500Hz includes room reflections. The bass extends down to a healthy 50Hz. More importantly, it is at the same level as the midrange. Ignore the notch at 150Hz. It’s a floor bounce in my setup. No notch is seen in the nearfield plot (Blue plot), confirming that it’s an anomaly.
Fig 3 – G1 Crossover Passband
Fig 3 shows the responses of the drivers. The Blue plot is from a Peerless 835025 mid-woofer and the Red plot is that of a Morel MDT29 tweeter. The Morel tweeter is surface mounted for a flatter response.
Fig 4 – G1 Null
The Violet plot in Fig 4 is when the tweeter is wired in the opposite phase. It resulted in a symmetrical and deep null centered at 1.85kHz, exactly where the two drivers are crossing. But how time-aligned are the drivers?
Fig 5 – REW Woofer and Tweeter Delay Plots
For that, I switched over to REW. This is a wonderful, free software that can measure time-alignment. The Red plot in Fig 5 is the Impulse of the MDT29 tweeter. The Green plot is that of the Peerless 835025 woofer. We can see that at the 100% mark, the woofer reaches the microphone first, closely followed by the tweeter.
Fig 6 – REW Delay Readouts
REW even provides you with a readout of the delays. In the top panel (tweeter), it recorded a delay of 0.31 ms referenced to an acoustic beep. In the lower panel (woofer), the delay is 0.29 ms. This correlates to the plots in Fig 5. The difference between the two delays is 0.002 ms (2 microsec). When converted to distance, this works out to 7mm (0.107 m – 0.100 m). So the woofer is ahead of the tweeter by 7mm.
2 microsec is an exceptionally small delay. If I’m a perfectionist and I insist on 100% time-alignment, all I have to do is recess the woofer in the cutout by 7mm. That will bring the tips in Fig 5 to overlap exactly at 100%. However in use, there’s virtually no difference because I certainly cannot tell two sounds arriving at 2 microsec apart. For all intents and purposes, the G1 Monitor is time-aligned.
Fig 7 – Step Response
The sharp tip at the bottom indicates good alignment between the woofer and the tweeter (Fig 7). In the transient, the G1 exhibits quite a fast attack. She hits the apex at 300 microsec cleanly with no overhang.
Fig 8 – Waterfall
Fig 9 – Toneburst Energy Storage
Fig 10 – Spectrogram
The Waterfall (Fig 8) and Toneburst (Fig 9) plots show some excess energy above 2kHz. They will not affect the performance of the G1 as they are dissipated by 2 msec (Fig 10). As for the bleed at 1kHz, it dissipated by 6 msec. I did not detect any smearing during playback.
Fig 11 – Excess Group Delay
The G1 has an Excess Group Delay of -1.77 msec at 45Hz (Fig 11). This is very low for a bass reflex.
Fig 12 – G1 Impedance
Most modern day power amplifiers should find the G1 an easy load (Fig 12). The lowest impedance is about 5.5Ω at 5kHz. With such an impedance, the G1 would normally be labelled as 8Ω nominal.
The electrical phase is not too demanding. Generally, it’s 20º max in the midrange and upper treble. The lowest is at 1.6kHz, where it dips to -45º.
Fig 13 – Maximally Flat Alignment • Fb=44Hz
Coming to the bass reflex alignment, the G1 is tuned for a maximally flat response (Fig 13). The box tuning (Fb) is at 44Hz but the actual tuning is 40Hz as seen in Fig 12. The discrepency is probably due to a higher Vas brought on by the internal stuffing. The port I used is a 1.5″ diameter PVC tube cut to a length of 3″. The -3dB (F3) is at 45Hz, impressively low for a 6.5″ woofer..
Fig 14 – Over-Damped Alignment • Fb=39Hz
If you prefer a tighter bass, the G1 can be tuned for an Over-Damped Alignment with a Fb of 39Hz (Fig 14). Port diameter is still 1.5″. The new length is 4″.
Fig 15 – Sealed Box Alignment • F3=74Hz
If you are not interested in the bass because you want to use it for nearfield monitoring of voices, use a sealed box (Fig 15) instead. This will be similar to the bass roll-off in the Yamaha NS10 which is also a sealed box.
An additional benefit of using a sealed box is a smaller footprint. The box is only 13 liters. That’s a massive 30% reduction than the 18 liters bass reflex.
Sound of G1
The G1 is neutral sounding. This is what a flat response speaker should sound like. There must not be any emphasis in the bass, midrange or treble otherwise it will distort the mix. Basically, what we want in a studio monitor is a zero reference point so that the sound engineer can hear what he’s doing. For comparison, this is what the famous or infamous Yamaha NS10 studio monitor looks like (Fig 16).
Fig 16 – Yamaha NS10 Frequency Response
Crossover is available on request. Free for DIY. Not for Commercial use.
February 18, 2021Projects