https://www.diyaudio.com/community/...overs-without-measurement.189847/post-2834287
Can you provide the attendant circuit diagram of the filter network that was referred to above? I can't seem to get my idealizations to work the way I expected.
Thanks for the circuit. I've set it up in VituixCAD as shown below.
The resulting filtered frequency response curve is shown below using the red line. As expected, at higher frequencies the roll-off rate is less than second-order, due to the impedance of the series RC leg becoming dominated by the resistor.
In addition, for comparison purposes, the blue line corresponds to the above circuit with resistor R1 short-circuited. In this instance, the response seems to be much more like a theoretical 2nd-order Butterworth filter response function, with a 12dB/octave roll-off rate.
The resulting filtered frequency response curve is shown below using the red line. As expected, at higher frequencies the roll-off rate is less than second-order, due to the impedance of the series RC leg becoming dominated by the resistor.
In addition, for comparison purposes, the blue line corresponds to the above circuit with resistor R1 short-circuited. In this instance, the response seems to be much more like a theoretical 2nd-order Butterworth filter response function, with a 12dB/octave roll-off rate.
Nonetheless, it gives the correct response for that speaker. I’ll go into a little detail about the process in determining this.
This was a 15” woofer crossed to a waveguide, so the cross is snug against the natural upper rolloff. I was using Speaker Workshop as a simulator which explains the unique looks and smoothing parameters.
I used full polar measurements to determine that I could cross on top of the relatively benign 1st breakup mode. This allowed me to get the “kick” I needed to flip to a steep crossover slope. The real reason for crossing there of course, was to match directivity.
The resistor isn’t a standard Zobel value, it was there to tune the damping of the knee of the rolloff and in this case it gave me the control I needed to get that right.
The baffle step happens below the room’s Schroeder frequency since the baffle is 60cm wide with the woofer occupying much of that. The response is therefore largely flat down to 200Hz, below which it gives a near textbook average step. (Somewhere I’ve posted a quasi anechoic shot of the averaged baffle response which is revealing.)
The upshot of this is that I virtually ignored the baffle step in the cross, and picked it up in the multi-sub implementation.
This was a 15” woofer crossed to a waveguide, so the cross is snug against the natural upper rolloff. I was using Speaker Workshop as a simulator which explains the unique looks and smoothing parameters.
I used full polar measurements to determine that I could cross on top of the relatively benign 1st breakup mode. This allowed me to get the “kick” I needed to flip to a steep crossover slope. The real reason for crossing there of course, was to match directivity.
The resistor isn’t a standard Zobel value, it was there to tune the damping of the knee of the rolloff and in this case it gave me the control I needed to get that right.
The baffle step happens below the room’s Schroeder frequency since the baffle is 60cm wide with the woofer occupying much of that. The response is therefore largely flat down to 200Hz, below which it gives a near textbook average step. (Somewhere I’ve posted a quasi anechoic shot of the averaged baffle response which is revealing.)
The upshot of this is that I virtually ignored the baffle step in the cross, and picked it up in the multi-sub implementation.