In part 2 of the Wharfedale Diamond 10.2 review I will cover frequency measurements, impedance and distortion measurements, but first we start with the official technical specification from Wharfedale.
Technical specification:
Format: Stand-mount
Bass/mid driver: 165mm
Tweeter: 25mm
Amplifier power (rec.): 20-100W
Impedance (Nominal): 6Ώ
A/V shielded: Yes
Sensitivity (1W@1M): 86dB
Nominal Frequency Range: 40-24kHz
HF Limit (-10dB): 44kHz
Freq. Fb: 42Hz
Crossover Frequency: 1.8kHz
Dimensions (HxWxD) (mm): 364x223x301
Ok, let’s see how accurate the specification is.
Impedance measurements:
(click on picture to zoom)
Blue: Left loudspeaker
Green: Right loudspeaker
Good impedance similarity between left and right loudspeaker with a 4 Ohm impedance minimum @ 157Hz. The port tuning frequency is 44Hz, slightly higher than the official specification of 42Hz.
There is a small wrinkle in the impedance plot around 500-600Hz. This could be some sort of mid-woofer chassis or other type of resonance.
From 300-20000Hz the impedance stays above 5 Ohm without any sharp phase shifts. This should be an easy load for just about any type of amplifier.
Update! (20140608)
This is the updated impedance response with new replacement drivers for the right loudspeaker.
(click on picture to zoom)
Blue: Left loudspeaker
Green: Right loudspeaker
Purple: Right loudspeaker with replacement drivers
The impedance plot shows a bit better consistency between left and right loudspeaker with the new replacement drivers.
Frequency measurements:
If nothing else is noted in the comments, the following frequency measurements of the loudspeaker are made at a 2m distance at tweeter height.
All frequency response charts are presented in a 50db scale with 1/24 octave smoothing and the measurements are valid down to 400Hz.
(click on picture to zoom)
Left: Frequency response on-axis:
Right: Frequency response 15deg off-axis:
Blue: Left Loudspeaker
Red: Right Loudspeaker
The on and 15deg off-axis frequency measurement shows an overall linear frequency response with a slight dip between 3-5.5kHz.
We have a sharper dip centered at 13kHz which is most likely caused by the diffraction from the tweeter´s design ring and grill cover. We have another broader dip centered around 550Hz which correlates to the impedance wrinkles at the same frequencies.
From the review part 1 I described the right loudspeaker as having a slightly different sonic character as it sounded a tiny bit darker than the left speaker and here’s the reason for it.
The right loudspeaker has about 1.5dB less output between 4-20kHz. The high frequency response are almost identical, but with lower tweeter level.
The 15deg off-axis confirms the same high frequency behavior. In the next review part I will try to find the reason for this difference.
The rest of the frequency measurements shown in this review part will use the left loudspeakers frequency responses.
Update! (20140608)
This is the updated on-axis and 15deg off-axis frequency response with the new replacement drivers for the right loudspeaker.
(click on picture to zoom)
Left: Frequency response on-axis:
Right: Frequency response 15deg off-axis:
Blue: Left Loudspeaker
Red: Right Loudspeaker
Green: Right loudspeaker with replacement drivers
With the new replacement drivers in the right loudspeaker (green) we can see a much closer match to the frequency response of the left loudspeaker (blue). This small difference frequency response is negligible and the loudspeaker pair now sounds more balanced.
(click on picture to zoom)
Left: Frequency response on-axis:
Right: Frequency response 15deg off-axis:
Blue: Left Loudspeaker without front grill cover
Red: Left Loudspeaker with front grill cover
The above frequency responses show the effect of using the front grill cover. The front grill smothers out the 13kHz dip on the on-axis measurement, but overall it introduces more frequency anomalies than without.
I recommend listening to this loudspeaker without the front grill covers.
(click on picture to zoom)
Left:
0deg = Blue
15deg = Red
22.5deg = Green
Right:
30deg = Blue
45deg = Red
60deg = Green
Nice frequency linearity throughout the off-axis measurements without any off-axis frequency collapses in the upper mid-range or lower treble region.
(click on picture to zoom)
Upper Left: On-axis individual driver frequency response.
Upper Right: 15deg off-axis individual driver frequency response.
Lower Left: On-axis individual driver frequency response with reverse polarity.
Lower Right: 15deg off-axis individual driver frequency response with reverse polarity.
The on-axis measurement shows a broad overlap in the 2-3.5kHz region. The 15deg off-axis measurement on the other hand shows a deeper “null” when the tweeter is connected with reverse polarity.
The official technical specification states a 1.8kHz cross-over frequency, while the measurements indicates a cross-over frequency just below 3kHz.
The mid-woofer has almost a text book LR4 cross-over slope and the tweeter has a LR4 slope down to 3kHz, but below 3kHz it has a broad “knee” in the frequency response that doesn’t follow a LR4 cross-over slope.
From the measurements it seems like Wharfedale has optimized the design from the 15deg off-axis frequency response with a targeted cross-over point around or just below 3kHz. This sets the cross-over point about 1.1 kHz higher than advertised.
Distortion measurement:
Measurement setup:
- Tweeter-axis near-field measurement at 18cm
- Frequency Range: 200-10000Hz
- Baffle size WxH: 22,3×36,4cm
The distortion measurements are done in near-field and the amplifier output level was adjusted for each driver so that the fundamental is 90dB and 95dB at 1m. This setting simulates medium and high listening levels.
Note! The distortion measurements are done assuming that the loudspeaker has a sensitivity of 87dB @ 2.83V/1M. This means that the actual distortion measurements is somewhere between +0/-2dB from the reference level 90dB and 95dB @ 1m.
(click on picture to zoom)
Top left: Left loudspeaker, 90dB @ 1m
Top right: Right loudspeaker, 90dB @ 1m
Lower left: Left loudspeaker, 95dB @ 1m
Lower right: Right loudspeaker, 95dB @ 1m
The right loudspeaker has an overall slightly higher distortion profile than the left loudspeaker.
The impedance and frequency wrinkle around 550Hz appears here as an elevated second-order distortion.
We have some elevated third-order distortion between 550Hz and 2000Hz with an average third-order distortion of about 0.3-0.4% in this region.
The distortion profile of the Wharfedale Diamond 10.2 is quite good for a loudspeaker in this price range.
In the review part 3 I will dissect the loudspeaker and un-mount the drivers, cross-over, ports damping material and examine the cabinet construction in detail. I will measure each individual drivers T/S parameters, frequency response, impedance plots and distortion profiles.