Overview:
The RS28F-4 is a 4Ω tweeter from the Dayton Audio Reference series.
It offers a very sturdy build quality with a metal faceplate and a grill covering the silk dome.
It has a tuned rear chamber, supported by a rugged diaphragm assembly. It has excellent power handling and a low-distortion motor system with a lot of copper in the right places. It has a low free-air resonance and it supports very low crossover points (1200-1500Hz), depending on the used filter design.
This very nice tweeter not only measures well, but also sounds great and matches mid-woofers which need low cross-over points perfectly.
Dayton Audio Spec sheet: RS28F-4
T/S Parameters:
An average of about 150hz higher free-air resonance than manufactorer spec sheet.
Impedance:
Free air impedance measurement:
Sample 1 = Green
Sample 2 = Blue
The two samples are not a perfect match. The samples differ by 80Hz on the resonance frequency and sample 2 has a more damped resonance frequency peak.
Frequency:
Frequency measurement conditions:
The tweeter is measured mounted in a 8 liter Dayton Audio enclosure (PartsExpress part #302-701) baffle with the following conditions:
Baffle size (WxH): 19,05×30,48cm (7,5″x12″)
Driver position: Mounted on center-line with driver unit center 8cm from the top of the baffle.
Mic position: 1m distance, on tweeter-axis.
Smoothing: No smoothing applied.
0deg tweeter-axis
Sample 1 = Blue
Sample 2 = Red
Virtually the same frequency response between the two samples. At 3.5kHz the baffle diffraction is noticed as a dip in the frequency response. This dip is reduced in the off-axis measurements. The tweeter has a slightly rising top-end frequency response in the on-axis measurements.
0deg = Blue
15deg = Red
22.5deg = Green
30deg = Blue
45deg = Red
60deg = Green
Distortion:
Measurement setup:
- Tweeter near-field measurement at 10cm
- Frequency Range Tweeter: 500-10000Hz
- Baffle size WxH: 19,05×30,48cm (7,5×12″)
The distortion measurements are done in near-field and the amplifier output level was adjusted for each driver so that the fundamental is 85dB at 1m and 90dB at 1m. This setting simulates normal to medium-high listening levels.
Sample 1:
85dB at 1m
Sample2:
85dB at 1m
Sample 1:
90dB at 1m
Sample 2:
90dB at 1m
The odd-order harmonics are low throughout the tweeters usable frequency range. The harmless 2nd order harmonics is a bit elevated compared to the odd-order harmonics, but is still very low. To sum up, this is a very low distortion tweeter and it can be used as low as 1.5kHz with an appropriate filter.