Theoretical question on L-pad design

[Cunundrum]

I'm interested in the theory on using resistors in the traditional l-pad format vs. a single inline resistor of higher value (where applicable) resulting in the same level of driver attenuation. L-pad's seem to be largely benign with other crossover components and have little impact on sonic purity.

Would a single inline resistor of higher value interact differently with other xover components than a traditional L-pad circuit?

Should the resistor(s) be placed before or after the xover?

Can an audio grade resistor (i.e, mills) be used in tandem with a standard audio taper potentiometer to produce a "hi-fi" variable gain control? (The ready made volume pots seem to be less than ideal)

[fjhuerta]

Well... l-pads do have less of an impact on frequency response.

A single inline resistor definitely interacts differently with the x-over. I don't remember the theory exactly, but depending on where you place it (before or after the x-over circuit) frequency response is affected. It's all in the Loudspeaker design cookbook, IIRC.

The short version is - an L-Pad will not affect FR as much, an inline resistor before the circuit is OK, an inline resistor after the circuit can affect FR significatively, and some designs actually use inline resistors before and after the circuit.

The problem with a variable L-pad as the one you describe is that the Mills resistor would have to be in series with the circuit, while the pot would have to be a shunt. And you'd have serious problems when R=0 on the pot... the alternative would be the pot in series with the circuit, but then you'd negate all the benefts of the Mills.


If you need more info, I can search for it in the book...

[Cunundrum]

Thanks for the insight Javier. That was very helpful!