Crossover & Measurements

A new crossover?

I used a combination of ARTA and Speaker Workshop to acquire the frequency response of each driver and design a suitable crossover. However I found that the original TDL RTL3 crossover gave the same predicted response as mine but with fewer parts and since I'm no crossover expert I decided to stick with that and simply replace all the components for better quality ones.

On further analysis and measurement it was apparent that the tweeter needed padding down which was not part of the original crossover. This explains in part why the TDL RTL3's had an emphasised tizzy top end. The quality of the tweeter is far from excellent, but adding an L-Pad does miracles for it. If you have a pair of TDL RTL3's lying around and want to improve them with the simplest mod, then I can't suggest a simpler method for good improvement than by simply adding these two resistors to the network!

Rp1 and Rp2 are the L-Pad resistors. These are the only addition to the original network.

Parts Replacement

The parts are from Madisound. The inductors are 19awg air-core, the capacitors are Solen Polypropylene, and some of the resistors are Eagle Metal Oxide Film. The L-Pad was an add on and I used some decent spare resistors from my spare parts box. The air core inductors are measured to achieve the exact value by unwinding from slightly larger ones.

Above right is the original TDL RTL3 crossover, and the new one with only an L-Pad added is on the left. The parts are mostly soldered together point-to-point directly to the rear of the connector plate.

Frequency Response Measurements

The above shows the unsmoothed farfield frequency response of the woofers and tweeter. The thin lines are the raw response of the drivers (measured without the crossover in place) and the thick lines illustrate the response with the crossover.

The above measurement is of a combined nearfield and farfield response smoothed to 1/16 octave, and also 30° and 60° off axis.