Inductors on 2.3TL

Bubinga99

A while back I measured all the crossover components on my 2 pairs of 2.3TL's. One inductor in particular (the one labeled as 0.3mH on the schematic) measured about .18mH, or about 40% lower than the schematic value. This changes the response of all 3 tweeters.

Since I measured this .18mH value on all 4 speakers, and the 2 pairs are pretty far apart in serial number, that would seem to say it wasn't just a bad batch of inductors at one time.

Does anyone know if this change from .3mH to .18mH was an official change that just didn't get included in the schematic?

ben62670

Do you have a standard inductor to check values? Could the meter be off?

Bubinga99

Hi Ben, well the meter is calibrated and not beyond its calibration date range, and the other inductors all measured within +/-10% (except one that was 12% low).

Here's all my measured values as a percent difference from the schematic values:

DarqueKnight

The .3mH inductor is in parallel with the .4mH inductor and the inductance of the tweeter coils. When you put your meter across the terminals of the .3mH inductor while it is still in the crossover, the meter sees the combined parallel inductance of the .3mH coil, the .4mH coil and the small inductances of the three tweeter coils.

The parallel combination of .3mH and .4mH = 0.17mH (then you would add the small inductance values of the tweeter coils to this).

If you disconnect one of the leads of the .3mH inductor, you should measure close to the nominal value.

Bubinga99

I measured it correctly. The value is .18mH on all 4 that I measured.

F1nut

Bubinga99 wrote: »

I measured it correctly. The value is .18mH on all 4 that I measured.

You removed them before measuring?

Bubinga99

On the first pair, I was rebuilding the crossovers at the time, so after I removed all the R's and C's from the board I measured all the R's, L's, and C's, and ESR.

But you don't need to remove everything. Have a look at the 2.3TL schematic again.
When the crossover is completely out of the speaker and none of the connectors are attached to anything, nothing is in parallel with anything. All those terminals to the tweeters and to the main connector are open circuits in that case. Every component (for this particular crossover topology anyway) can be measured while still in the circuit board. Everything is "dangling" and there is no closed loop anywhere.

This isn't true for every model of SDA (the 1C for example) but it is for the 2.3TL

bsoko2

I'm replacing my tweets with the RDO-198's on my 2.3TL's. Anything I should look for when I do this?

Bill