here is the PINOUT for the Speaker Connectors on Logic board 820-2828
=== Update (06/21/2020) ===
[image|2153156]
here is picture
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=== Update (06/21/2020) ===
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Dear friend,
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Thank you very much for your great news.
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About speaker, sorry that it can not support the original iMAC speakers . As it can not provide enough power. But it can support the 5W 8ohm speaker instead. Will this give you the answer?