Single Coil vs. Humbucker volume question

[LowMoJo]

I'm aware of the reason for the difference in pickup volumes on the HS models, but I was wondering if it's less apparent on certain basses. It's quite noticeable on my Stingray, but I seem to recall it being less so on a Sterling I played at a shop. Just thinking ahead to my next bass.

 

[Duarte]

Could pickup / string height be a factor?

 

[LowMoJo]

it's possible. any idea if the series wired basses have louder single coils? since they likely have more mids and all.