The inductance of a 30" twisted pair cable will be about 20 nH. Forget about the inductance of the connecting wires for such short lengths. Most likely, the whole catch is in the output filter of the amplifier. As soon as the speaker impedance decreases in relation to the low-pass filter setting in the amplifier, the effect will immediately appear the inductance of the output low-pass filter amplifier in the form of additional inductance, and this inductance can be from 20 μH to 40 μH, it depends on the manufacturer of the amplifier.The amplifier makes you a roll-off in the frequency response, since the output low-pass filter of the amplifier is not covered by feedback.There is probably about 30" of twisted pair wire between the amp and the tweeter... Surely twisted pair wire would not add this much inductance? or maybe yes?
If the parts are accessible it is a simple way to try and count one problem out before considering more obscure reasons. There may be an unexpected interaction in the passive parts, a simple electronic frequency response will tell you if the problem is there or somewhere else.I agree that is a concern in any analog circuit. In this particular case, I can not simulate this response with any reasonable variation in the tweeter crossover values.
Oh wow I'm in love!Yes, it controls the 5" midwoofer breakup. In this particular case, I can change the notch filter values by +/- 10% without affecting the response too much.
I measured the woofer response with the crossover, and it agrees closely with the sim. When I measured the tweeter response with the crossover, I see the difference... a rolloff starting at about 7k and growing to be about 3 dB at 16k.
Good thought...The wiring length definitely changed. For the testing of the drivers, I was using short leads from the amp to the drivers. The actual finished system uses longer wiring. As you can see, I used twisted pair wiring for a neater installation. There is probably about 30" of twisted pair wire between the amp and the tweeter... Surely twisted pair wire would not add this much inductance? or maybe yes?
View attachment 1261099
yes that is correct.
I agree that is a concern in any analog circuit. In this particular case, I can not simulate this response with any reasonable variation in the tweeter crossover values.
Interesting... I need to think on that. I need to think about how the inductors were arranged in the cabinet.
Thank you for all the comments...... j.
Can you show the impedance plots as well for both cases, sim and real?
If the parts are accessible it is a simple way to try and count one problem out before considering more obscure reasons. There may be an unexpected interaction in the passive parts, a simple electronic frequency response will tell you if the problem is there or somewhere else.
In class D amplifiers, a low-pass filter (LPF) is placed at their output for demodulating the Pulse Width Modulation (PWM) signal. If this LPF is not covered by feedback, there will always be an influence of the LPF properties between the amplifier and the load. It is this LPF that possesses such physical properties; it is capable of altering the amplitude of the output signal when the load resistance changes. In post number 627, this property is precisely depicted in the lower picture; please study the images attentively. In class D amplifiers where the LPF is covered by feedback, such an effect is not observed because the feedback monitors the LPF output signal and makes necessary corrections to prevent such changes in the LPF output signal at the load.For us non-sparkies, can someone explain the conditions in which this could arise?
In class D amplifiers, a low-pass filter (LPF) is placed at their output for demodulating the Pulse Width Modulation (PWM) signal. If this LPF is not covered by feedback, there will always be an influence of the LPF properties between the amplifier and the load. It is this LPF that possesses such physical properties; it is capable of altering the amplitude of the output signal when the load resistance changes. In post number 627, this property is precisely depicted in the lower picture; please study the images attentively. In class D amplifiers where the LPF is covered by feedback, such an effect is not observed because the feedback monitors the LPF output signal and makes necessary corrections to prevent such changes in the LPF output signal at the load.