When I look at the 1209 and 1201 Altec networks they are identical except the 1201 has a resistor value of 7.5 ohms and the same resistor in the 1209 is 8 ohms. The 1209 has a zobel circuit in the LF section. Other information that I can garner is that the hipass in the 1209 is a 12db slope while the 1201 is a a 18db slope. since that is in the hipass section and other values are ldentical I suspect that the inductor for that part of the circuit contributes that that. To make a long story short, are these small differences noticeable given that the zobel is there (I assume) for noise only?????