Kinergetics SW800C subwoofer crossover DSP simulator.

I occasionally see people post questions about the old Kinergetic subwoofers and in particular, questions about the SW800C crossover that came with the speakers. Given the age of the equipment, there aren’t too many of the crossovers still in circulation. So, I decided to see if I could develop a DSP emulator of the crossover. I am posting this here so that others have access to this info if they ever need it. I did this analysis with data from REW and implemented the results with a miniDSP 2x4HD.

I initially close-mic’ed a speaker to minimize room effects (mic-setup.jpg) and ran an REW sweep (SW800C.jpg). The black curve is the trace with the SW800C in the signal path – the reference curve. The red curve is the signal without the SW800C (i.e., preamp – power amp – speaker). It should be noted that I turned down the gain with the DSP (not the preamp) to avoid any unwelcome surprises. As a result, he two signals are not gain-matched at this point.

Given the shape of the raw transfer function, I applied a ramp filter to the signal [SW800C(a) & (b)], which brought the signal down at high frequencies. I then boosted the overall gain on the DSP to roughly align it with the reference curve. In fact, I didn’t add any gain (0 db on the DSP) because the two curves were pretty close to gain-matched at 20 hz.

I then applied a 12 db/oct low pass BW filter with a cut-off frequency of 120 hz to match the settings in the SW800C. (The blue curve in SW800C.jpg is a 12 db/oct filter with a cut-off at 150 hz.)

I completed the development by applying a steep high pass filter (LR48 db/oct) at 20 hz to eliminate any subsonic signals. Sonics.jpg shows the roll-off below 20 hz that is provided by the SW800C.

The final results at the listening position are shown in SW800C-Transfer-Function.jpg. Again, the black curve is the target from the SW800C and the red curve is the DSP emulation. In this case I was also running the main speakers, so you don’t see the roll-off at 120 hz. In the fullness of time I would need to use additional EQ to flatten out the low frequency response, but that wasn’t the focus of this project.

Finally, I should mention that I got a lot of help from several engineers, so the full development thread is captured here, which started off in a completely different direction.

In addition, all of the referenced pictures can also be found at this link.

https://www.electro-tech-online.com/threads/kinergetic-subwoofer-circuit-analysis.165898/

I hope this is helpful to folks down the road. Overall, I am pretty happy with the results and am happier still to know that I have a backup if the box ever fails.