AKG BX25 problem

[Aref]

Hey,
I found a same topic about BX20 problems and find it useful, but this might become a good thread for typical BX25 issues.
I made the remote and found that one channel (2) builds a gradual feedback on its short RT. It also happens when I disconnect the ground (pin1).

My main issue is the tone difference among two channels. One sounds bright and the other dark!
I'm in the process of making the remote and then calibration. Does the short/long reverberation level balance help this?
I also hear little bit of distortion. Any experience?

 

[gyraf]

The BX20 has a selection of trimmers that can cause this, when set wrong - probably also the case with the '25.

Try trimming/calibration procedure.?

Jakob E.

 

[Aref]

The feedback issue is my main concern. I'm in the process of calibration and need to figure out how much volt is 0 dbm=1 W.
My studio reference is -18dbfs=+4dbu=0dbvu=1.23v

 

[zamproject]

The feedback issue is my main concern. I'm in the process of calibration and need to figure out how much volt is 0 dbm=1 W.
My studio reference is -18dbfs=+4dbu=0dbvu=1.23v

Hi
1 W really ??? I think you miss a mili factor ...
0dBm <=> 1mW under 600ohm <=> 0.775V
Best
Zam

 

[Aref]

Hey,
Zam you're right. It doesn't get that loud! Glad you help me everywhere...
Last night, I tried my best to figure out what's wrong with these two BX25. The good point is that I could swap whatever I doubt if it works right or not...
I couldn't level match both channels at the first place, but after working on echocompensation it started to sing on closer tonality and levels (Strange that reverb level came before echocompensation in alignment procedure of the manual!)

This reverb is like a musical instrument which needs to get tuned...There is not much about the mechanical part of it in the manual!
The feedback was the result of two springs so close to each other and the distortion was related to the spring and magnets distance. They all are adjustable with handles that holds the spring and pins on the top and down lids...
Please add any experience you've had about BX25
Cheers

 

[zamproject]

Hi Aref

Please add any experience you've had about BX25

I have no experience with BX25, I have a BX20 which IIRC don't share any part (maybe just the coil ?) with BX25.

Best
Zam

 

[Aref]

Hi,
Little confused with the echocompensation!
Is it related to "echo" or it's the dry/wet signal mix?
Manual says;
Input purst signal...listen via headphones....adjust output signal via R241(coarse) and R243 (fine) to minimum echo impression.
In the attached paper they say;
...dry/reverb signal mixing are provided for each of the two electrically and acoustically separate channels. Decay time is adjusted silently through the use of motional feedback.
Any idea from people who have worked with BX series?
Thanks

 

[natrecstudio]

We just went thru restoring two BX15's so you really have my sympathy: they don't make it easy, and there is a lot of head scratching stuff in the manuals and in the designs themselves.