I have been struggling with my DSL service since I moved into this new home. For some reason, my modem was training to 4M instead of the 8M in my previous home. My first reaction was acceptance that this was due to the distance factor from the exchange (which IS a significant factor). However, after months of resentment that life should be better, I decided to do something about it.
I had suspected that my internal home wiring was a factor. I knew that I should get a boost by changing things around, however, did not expect the level of impact. 15 minutes of investment boosted my speed from 4 MB to 8 MB.
So here is what I did and some explanation of what was causing the problem.
In the picture above, scenario A is your typical home internal wiring. The pair comes into the home through a special wall plate (NTE) and is then distributed around the home. This is a spiderweb typically. Worse, there may be other devices using the phone lines .. intercoms, alarm systems, pay-per-view box etc. The ADSL modem is typically on the end of one of these legs so, the signal to the modem has the interference and loss caused by the spiderweb of internal home wiring in addition to the normal loss and interference.
Scenario B uses a special device called an NTE5 central adsl splitter that plugs into the wall-plate where the copper pair from the exchange enters your home (you will have to do a mini external home survey to find where the pair disappears into the wall into your home).
You can see from the diagram that the signal to the modem does not have any of the issues with the internal home wiring. This also eliminates the need to put splitters on each and every outlet that has a phone.This is a 15 min job. Really trivial. Only limitation is that your ADSL modem now has to be located and plugged into this wall plate only. Here is a good link / site that explains further.
The issue of having the ADSL modem locked into one place possibly far away from a computer is really a non-issue now-a-days. Two options / reasons : most ADSL modems now have WIFI built in (G or N standards will be more than enough). Alternately, there are powerline ethernet devices that work very well. What these devices do is basically make your internal home power (220V) cables into a transmission network for ethernet. Fairly pricey still, however, extremely flexible and they work !! I use the NetGear Powerline Ethernet HD adapters and have no complaints.