Which cycle day would be the best day to BD to conceive if the man has a low sperm count?

2 days before O

1 day before O

Or right on ovulation day

If somebody knows, can you tell me the scientific reason why?  (Can't find an answer researching internet)

Thanks

Day before O because it gives the sperm enough time to capacitate

*this info is not for swaying but for infertility with men who have low sperm count