In this blog I test the Bliesma T25b-6 dome tweeter on the Azurahorn AH-1100.
Bliesma products can be found here as well as the published specification here.
Key Features for tweeter:
- 25mm beryllium dome
- Copper sleeve
- 2mm linear excursion
Key features for horn:
- 15cm (6.00" diameter) x 65mm deep
- Fibreglass
- 25.4mm (1.00") diameter throat
- Standard mounting for 1" compression driver
Both products mentioned above were shipped to me by my customers. I removed the metal grill from the tweeter and directly mounted it to the horn. The tweeter has a flat front face along with an inverted surround. This lends the tweeter to easy waveguide/horn mounting. For my testing I simply taped the tweeter to the horn. A more permanent solution may be to 3D print an alignment ring that also serves to clamp the driver to the horn.
Measurements
Below is the impedance sweep when mounted on the horn.
Below is the raw frequency response (red) along with the response using a 3.3uF capacitor (blue).
Below is the off-axis response at 0,15,30, and 45 degrees off-axis.
Time Domain
Below is the burst decay on-axis using a 3.55ms gate.
Below is the burst decay for the 15 degrees off-axis measurement.
The on-axis CSD plot is shown below.
Below is the CSD plot for the 15 degrees off-axis measurement is shown below.
Distortion
I began by measuring harmonic distortion at 85dB at 1m.
Increasing the test SPL to 95dB is shown below.
I then looked at intermodulation distortion starting with an 85dB SPL 1m test signal. I used a 2kHz LR4 high pass filter (HPF). IMD is around -72dB across the frequency spectrum.
Increasing the test SPL to 95dB we see IMD at -65dB.
