Air carrier First Officer reported there are tall towers that are not depicted on the approach chart for SBN; and during initial approach the flight crew may have potentially crossed one of the towers with less than required clearance.

Narrative

Coming in to land on 27L; cleared for the visual around 10 - 15 miles away at 3000 feet. PM was watching the big group of towers located on the approach place which shares the highest one being 1940. PF set 2000 FAF altitude; visual conditions; and field in sight. The PM was monitoring the group of towers waiting to cross them; PF was going to turn base after them. However; there's an extra tower around outside of the group of towers to the right side of them but not depicted on the approach plate and potentially crossed it with less than 1000 feet. No terrain warnings; no Tower warnings; and in full VMC conditions had them in sight. As soon as the big group of towers passed I was about to begin my base turn when I saw the last one cross. There is a chance we were not over that tower above 1000 feet. PF extended the downwind leg way outside of them to make sure this didn't happen. However; there's another high one not depicted on the plate still very high up.Cause: The approach plate should have more of the towers depicted even if it's all 7/8 of them. The highest one being 1940 but the plate should show the next ones' altitude as well. It's a big area with lots of towers. When cleared for the visual; PF should have stayed at 3000 feet and then on final configured to begin a quicker descent. There was no indication we were close to it and the PF landed safely in the touchdown zone and parked at the gate with no issues. Suggestions: Although the approach plate has the 2 towers at 1940; it doesn't do a good job depicting the ones outside that group. It should have all of the towers on the chart or at least the tallest 5.