They aren't repeaters, they are called remotes. They are essentially just mini DSLAM's that the modems sync to. Whether you sync to a remote or CO doesn't matter as long as both support the same technology (VDSL2 for example).
There are a number of characteristics that affect DSL speed:
1. The length of the loop (how long the piece of copper is between you and the remote or you and the CO)
2. Noise on the line. This is independent of loop length. You can be on a short loop that is very noisy or a long loop that isn't. This affects the stability of the connection and how much of the RCO (line's capacity for bandwidth) you are able to use.
3. The speed supported by your modem (ADSL, ADSL2+, VDSL, VDSL2...etc)
4. The speed supported by the DSLAM at the remote or CO that you are syncing to.
Some of the big problems up here in Canuck-ville with Bell is that they are very slow to upgrade the remotes. So let's say the CO supports VDSL2 (fibe) that doesn't mean that all the remotes in that city do. So even if you are 10ft from the remote, if the remote is an old ADSL 1st gen model, you still get a max of 7Mbit down, which is ridiculous.
I'm on a 1.5Km loop (even though I'm relatively close to the CO physically) but sync to a VDSL2 blade/DSLAM and subsequently am able to get 24Mbit down, 4Mbit up. My line is not noisy and is stable at 99% RCO.