This forum is very helpful for me, problem is my bad english. So I read to much over
![Sad :(](./images/smilies/icon_sad.gif)
Since a few weeks I startet to build a new head out of car speakers. This time I'm experimenting with Feedback. I make paperglued cones with an aluminium push rod at the end. These pushrod is not connected to a torque tube. Around the rod is a feedback coil. Between the feedback coil and the driver is steel and aluminium to keep away the dynamic magnetic fields from the driver coil. I have tested it before without the extra magnet for the feedback. Now, I got a good feedback amplitude (with very little 50Hz noise) but another problem where I think you all know it -> phase issues
In this forum I see often a phase plot, but I don't know the software to make it. The only way I check out the phase correlation is to use a 2 channel oscilloscope or record it to a stereo wave, where the one channel is the original driver signal and the other channel is the feedback signal. I can also see the X/Y diagram.
One messure point is direct at the driver contacts. The other point is after the feedback amplifier. I build a simple amplifier with 2 non-inverted NE5532, without a capacitor. I tested this produces no phase shift up to 15kHz. But now with the mechanic everything goes bad. In my opinion the signal at the feedback is older then the signal at the driver coil
![Wink :wink:](./images/smilies/icon_wink.gif)
Several problems I think about:
-The mass velocity rises to its maximum after(!) the maximum current is flow (?)
-sound velocity of the materials -> paper glued cone (?)
-capacity and/or inductivity of the wires (??)
Summing the signals can destroy my new expensive construction. So I don't want to try it without making things clear as possible. Here are many threads about problems of feedback, but I don't know how to handle with my results.
First Problem I cannot display my phase shift in a diagram. Only testing frequence by frequence and hold a ruler at the oszi
![Very Happy :D](./images/smilies/icon_biggrin.gif)
In this file is the left channel the original and the right is the feedback signal. Sorry for the different levels. The amp is from Sony
![Embarassed :oops:](./images/smilies/icon_redface.gif)
orig-feed.wav
I hope someone can help me a little bit.
MfG Fatrecco