March 2, 2012

T20 Rythmik dual opposed tapped horns - measurements

T20 has now been measured:

Red and blue lines represent the output of each driver individually, black is combined. You can see that the horn is much less effective with just one driver and the difference is far more than expected. Running together they smooth each other out. The difference suggests that the passive driver when switched off, actually undermines the horn. The plot above shows the response unfiltered.

Blue: Lower crossover

Compared to simulations:

Simulation shown in red. You can see the peak is higher in reality and has more damping. The real version rolls off earlier on the bottom end. With room gain however, the response is flat to well below 20 Hz, even with high pass filters in place. In short, this sub is now a beast!


  1. Hi Paul, this tapped subwoofer looks awesome ( if only one could peek inside ). Would it work also if I added two 8 " drivers on each side - how did Rhythmik calculate the interaction of the facing drives. Did he experiment with the distance and the exact placement ? I can't imagine that hornresp allows such a design - did he mirror and double one TH ? dakoolmalelivz at

  2. This sub is my own design using two older model Rythmik kits without modification. If you search for "T20" or look back you will see build pics and what is inside. It's actually quite simple. There is potential for 8" drivers to work, and it could result in a smaller version. Tapped horns are not all that difficult to design, but some drivers work better than others.


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