KrIVIUM2323
Well-known member
Hello,
I recently got a pair of PASSIVE System 800. They are nice speakers but i find they have some weird things happening in he 1,5khz area. I'm used to the ACTIVE version of them as i used them many times and this one doesn't have this behavior. There is some difference between them like woofer/ tweeter fc which goes from 1,8khz from passive to 1,6khz to active. The active line level filtering open possibilities which are unobtainable from passive too.
After some search over the web, i've found i'm not the only one to have this feeling and decided i could make my passive go active.
I found schematic and studied it. Overall this is not a very complicated circuit and it could be implemented relatively easily.
I think i figured out ( more or less) what is used on this circuit for processing ( omitting the signal 'conditionning' and pre filtering treatment) from ic2c which act as a buffer signal is split in two ways:
_ first one is tweeter way, starting with c18/r32 hp at 2khz it goes to a notch consisting of ic2a/d then it goes to a second hp at around 5khz thanks to c20/r20.
Then it goes to a tda7293 chipamp configured to have an overall gain of +25db.
_second path is the woofer way, starting with ic3d which act as an allpass 'leading phase' with an fc of 4420hz, then it goes to a second allpass cell this time 'lagging phase' at same fc 4420 thanks to ic2b.
This goes to a notch ( or a band pass?) acting at 800hz (ic3a/b) the output goes to ic3c which is configured to act as a second order lp at 1,1khz.
Then it goes through c32/r32 hp at 11hz to protect the tda7293 ( and woofer) driving the woofer. The tda is configured to have an overall gain of+29db.
My troubles comes from the two allpass in series in the woofer: from my understanding they may well cancel each other action. And i don't see Tannoy implementing this economical non sense...
So here it goes: could you make a sanity check over the signal path and could someone explain me or give a clue to understand what are the allpass actually doing and how?* And if you could help me define the delay time they should introduce it could be GREAT!
Thanks for your help in advance ( leading phase allpass cell in action!
Best regards.
* I understand why they are used ( to help compensate for delay of tweeter relative to woofer emmissing point -as the tweeter is located behind the woofer) but not really this implementation.
Component designation is from attached schematic for ease of comprehension.
I recently got a pair of PASSIVE System 800. They are nice speakers but i find they have some weird things happening in he 1,5khz area. I'm used to the ACTIVE version of them as i used them many times and this one doesn't have this behavior. There is some difference between them like woofer/ tweeter fc which goes from 1,8khz from passive to 1,6khz to active. The active line level filtering open possibilities which are unobtainable from passive too.
After some search over the web, i've found i'm not the only one to have this feeling and decided i could make my passive go active.
I found schematic and studied it. Overall this is not a very complicated circuit and it could be implemented relatively easily.
I think i figured out ( more or less) what is used on this circuit for processing ( omitting the signal 'conditionning' and pre filtering treatment) from ic2c which act as a buffer signal is split in two ways:
_ first one is tweeter way, starting with c18/r32 hp at 2khz it goes to a notch consisting of ic2a/d then it goes to a second hp at around 5khz thanks to c20/r20.
Then it goes to a tda7293 chipamp configured to have an overall gain of +25db.
_second path is the woofer way, starting with ic3d which act as an allpass 'leading phase' with an fc of 4420hz, then it goes to a second allpass cell this time 'lagging phase' at same fc 4420 thanks to ic2b.
This goes to a notch ( or a band pass?) acting at 800hz (ic3a/b) the output goes to ic3c which is configured to act as a second order lp at 1,1khz.
Then it goes through c32/r32 hp at 11hz to protect the tda7293 ( and woofer) driving the woofer. The tda is configured to have an overall gain of+29db.
My troubles comes from the two allpass in series in the woofer: from my understanding they may well cancel each other action. And i don't see Tannoy implementing this economical non sense...
So here it goes: could you make a sanity check over the signal path and could someone explain me or give a clue to understand what are the allpass actually doing and how?* And if you could help me define the delay time they should introduce it could be GREAT!
Thanks for your help in advance ( leading phase allpass cell in action!
Best regards.
* I understand why they are used ( to help compensate for delay of tweeter relative to woofer emmissing point -as the tweeter is located behind the woofer) but not really this implementation.
Component designation is from attached schematic for ease of comprehension.
