Telefunken TL 700 missing capacitor

[Nixxla]

I just did recap of one of these speakers. I'm not sure if it was necessary though because I don't hear any difference. It still had original capacitors and when I measured them after unsoldering they were still the same capacity as they were rated for. These speakers were rarely used since they were bought (maybe once in one-two years, and probably haven't been used at all in last 10-15 years).
What it bugs me is that in schematics for it's crossover there is one capacitor shown that is missing form actual PCB. How important is it? Should I insert it? Is it not a rare thing that schematics and actual PCB don't match? I marked that capacitor with red on schematics?

 

[Salt]

This is a capacitor of the midwoofer's low pass, if I see it correctly.
Maybe 6 dB was considered better than 12 dB (the capacitor) in time?

 

[kokono]

I don't have those, but very similar to Grundig hifi Box, which are a fun listen.
Capacitors usually don't drift much in capacitance, but usually in ESR. You need a good ESR metter for measuring that, and still we dont' know the original value.
Do not change electrolytic with film in a vintage speaker crossover, because most probably they'll sound bright.

 

[DVDdoug]

Are you sure the schematic goes with your particular speaker? Sometimes there is more than one version of a circuit board assembly.

Or if they find they should revise the design they may not re-design the board if they just need to delete a component. But in that case usually the schematic IS revised. The revision (a letter or number) might be marked on the schematic and the board and if they don't match, that explains it.

I work at an electronics company and we have a few different products that use the same PCB assembled differently. Usually there's a note on the schematic but sometimes it's just a different bill of materials and/or an assembly number/version marked on the actual board.

...Sometimes components are "tacked-on". In the long run the board is usually revised to properly accommodate the additional component(s) but some units may be sold with the temporary fix.

I just did recap of one of these speakers. I'm not sure if it was necessary though because I don't hear any difference. It still had original capacitors and when I measured them after unsoldering they were still the same capacity as they were rated for.

I'm not surprised although it's pretty-normal to imagine an improvement.

Electrolytic capacitors can age and deteriorate but I wouldn't "recap" unless I was having problem. The various film types are usually super-stable and last forever if you don't over-voltage them.

 

[Nixxla]

Are you sure the schematic goes with your particular speaker? Sometimes there is more than one version of a circuit board assembly.

Shematics are from service manual for whole TL series. Mine is TL 700 and I don't think there were several revisions of it, but maybe I'm wrong.

Anyway, here are the photos before and after "recap".

I didn't use film capacitors (If it's possible to find 100µF film one must be really huge and I don't think it would fit on the board), it was straight replacement with electrolytic ones. They sound good after recap, not worse for sure, but I'm still not sure if there was any improvement.

 

[kokono]

Can i ask you how do they sound?
Crossovers seem really business.