I recently had a fault on my broadband, which is through copper wires that also are used for the phone. We were suffered many disconnects. Plusnet, my provider did some checks and got me to do some checks in my building* and we decided the fault lay with the cabling so they raised a call with BT Openreach. A nice man came with his test kit and discovered that my speed was 3Mb/s faster outside versus at my master socket. When I say outside I mean in the junction box on my outside wall where the subterranean cable emerges and connects to my master socket by means of a cable which is about 1m in length. He changed this cable and my master socket, got someone to adjust my SNR and my problem is fixed. There was no charge for this. My speed is about 15Mb/s and I'm paying £9.99 for an 'up to 17Mb/s' service. We don't need anything faster.
All components in the network influence the speed at your device, even your operating system. We've run tests with the same computer, running Linux Mint it's networking is faster than when running Windows7 !
*Essentially they had me use a different router and plug it into the test socket inside the master socket with nothing else connected. My problem persisted.