MarkAudio-SOTA Cesti T Tower Speaker Measurements and Analysis
For our measurements, the Cesti T speakers were elevated at a height of approximately 4 feet with the mic height level with the 2” driver and 2 meters away in a large, open area. This gives us a window of 7 ms before ground reflections hit the mic, and that allows us usable data down to 150 Hz before resolution is completely lost.
MarkAudio-SOTA Cesti T loudspeaker response (2 meters outdoors)
The above graph show the direct axis frequency response of the Cesti T tower speakers and also the Listening Window curve, which is an averaging of the direct axis response with the vertical responses 10 degrees above and below and horizontal responses at 10, 20, and 30 degrees outward. These responses are unsmoothed. From low frequencies to high, we see that the Cesti T speakers have somewhat elevated bass with respect to the mids. This elevation gently tapers off into the midrange frequencies where we see a nicely flat response up to 8 kHz, and we also see what might be a slight comb-filtering effect from the drivers interfering with each other, but it is very mild and was not something I could hear. At 8 kHz we run into a sharp spike and another much wider spike stretching from 13 kHz to 18 kHz. These spikes are without a doubt the causes of the bright nature of the speaker on axis. They are caused by cone break-up, and this is when the cones begin to bend above certain frequencies. It looks like the 8 kHz spike is caused by the 4” cone breaking up, and the 13 to 18 kHz spikes are caused by the 2” cone or perhaps a combination of both cones. The Listening Window curve, which is an average of the direct response and axises close to the direct response, show that the treble spikiness abates only slightly when these responses of the front of the speaker are gelled together.
MarkAudio-SOTA Cesti T speakers horizontal frequency response +/-90 degrees from axis: 3D view
MarkAudio-SOTA Cesti T speakers horizontal frequency response +/-90 degrees from axis: 2D view
The above graphs show the horizontal response of the Cesti T speakers, measured at 10-degree increments out to 90 degrees. Here we see a very nice, wide, and uniform dispersion up to 7 kHz. A severe dip crops up above 7 kHz at 40 degrees and farther angles. The high-frequency response spikes become very pronounced as the off-axis response sags in these outer angles. The break-up modes can be seen to cause raggedness in the treble frequencies at nearly all angles.
MarkAudio-SOTA Cesti T Polar Map
The above polar map depicts the horizontal dispersion of the Cesti T speakers, but in a different way then the ‘waterfall’ graphs above it. In this graph we can see some waist-banding around the mids near the crossover region, although nothing severe. The breakup modes can be seen to spread a lot of acoustic energy at off-axis angles. This would account for the sibilance heard at toed-out frequencies, even when the direct-axis brightness was reduced from the change in angle.
One interesting thing that can be seen when we rotate the polar map 90 degrees is the effect of the asymmetrical waveguide on both sides of its axis. I have drawn a line through the direct axis to emphasize these effects. We can see the left side of the graph projects acoustic energy more widely than the right side, and this is because the waveguide is broader on the right side of this model and expands out more from the driver. The waveguide contains the acoustic radiation in a tighter pattern on the left side. The effects become apparent above 7 kHz, and the asymmetry of the waveguide doesn’t look to be influencing the speaker’s behavior very significantly below that point.
The axis I would recommend to the listener is 20 degrees on the side of the ‘closed’ end of the waveguide, for this reason:
At 20 degrees angled to the closed end of the waveguide, the response is really quite good, and I would advise users to have that angle facing the listening position, which, in many cases, would have this speaker facing straight ahead in parallel vectors. The problem remains that acoustic reflections from room surfaces can still bring in some of that elevated treble response. I will repeat that on recordings that do not lean heavily on these high frequencies still sounded very good- perhaps a little forward but detailed without being edgy. The addition of a reasonably good tweeter and a much steeper low-pass filter would go a long way towards correcting these problems, but it would seem to be against MarkAudio-SOTA’s design philosophy at this time, which is a pity.
MarkAudio-SOTA Cesti T Impedance and Phase Response
We can see that the Cesti T speakers are tuned to about 50 Hz from the saddle between the peaks in the bass frequencies. The Cesti T speakers do not pose a stiff electrical demand on amplifiers. Impedance never dips under 5 ohms at any point. Impedance does consistently hover around 5 ohms for the treble frequencies, but even here the phase angle is never severe, so this should be an easy load for any amplifier. Sensitivity was measured as 86.4 dB for 2.83v at 1 meter, which isn’t very far from MarkAudio-SOTA’s spec of 88.5 dB for 1 watt at 1 meter, given the impedance curve. This is not an unexpected sensitivity spec for a speaker of this design. This speaker does not need a heavy-duty amplifier to get loud, not that it can handle a lot of current anyway. Again, we should mention here that users should pay attention to the power-handling specification provided by MarkAudio-SOTA.
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Read: MarkAudio-SOTA Cesti T Tower Loudspeaker Review