Getting 20% less than my lowest speed estimate

[#1]

RadioFox,
Thank you - I can now see why your expectations a bit over optimistic.
The Speed Guide results are not really correct, as they provide just one figure for ADSL without distinguishing between ADSL/ADSL2.  ADSL2+ uses additional frequency bins and therefore has the potential to be different.  ADSL(1) and ADSL2 calculate attention differently and therefore an attenuation of X will not deliver the identical synch speed for both ADSL(1) and ADSL2.  

Quote from: ejs

ADSL_G.dmt.bis indicates ADSL2 not ADSL2+. ADSL1 and ADSL2 will report similar attenuation figures, ADSL2+ will tend to give a higher downstream attenuation figure.

These calculators are an ESTIMATION of synch speed and not guarantees.  That said, lets look at the results...
Speed Guide: ADSL 6112 / ADSL2+ 7026
Kitz: @45dB ADSL 5888 / ADSL2+ 7200 - @46dB ADSL 5792 / ADSL2+ 6816
Your last reported synch speed (6587kbps) is better than either of these forecasts for ADSL/ADSL2, given that you are (if I understand ejs correctly - we cannot see the whole of the modulation field value) NOT running ADSL2+, you will not get the higher ADSL2+ speeds.
Having understood synch speed, you then need to consider that the PROFILE speed (the maximum speed at which data can be transferred) will be 88.2% of the synch speed.  This makes the following advice on speed guide WRONG!

Quote

Considering protocols overhead, best case scenario should be able to achieve ~90% of the maximum theoretical speeds in actual throughput speed testing.

For your SYNCH speed, you BT Profile will be 5.81Mbps, which PlusNet will round down to 5.8Mbps (see current speed on the user portal).  These both need to be checked.

The actual DATA transfer speed which you then see will be a fraction of the profile speed, as data speed tests report how long it takes to SUCCESSFULLY transfer a volume of data.  Remember that errors need to be corrected / retransmitted using the available physical transmission capacity.  For example if you are trying to transfer 100MB of data and the error rate is such that 50% of all transmissions are unreadable, then to transfer the whole 100MB 197MB of data will be transmitted all together. (Send 100MB, 50MB fails and need to be resent, send that 50MB, 25MB fails...).
It is though not just transmission errors which need to be considered - your internet is delivered over BT services which are provisioned on "contended" connections.  That means for any given resource / capacity you are sharing that with a number of other users - typically 50.
To summarise - your SYNCH speed is well aligned to expectations.  4.8Mbps DATA speed might be just a little shy of what it might be - that could be down to elevated error rates or due to exchange congestion.  A TBB BQM would be helpful.

[#2]

I would have taken the kitz WBC estimate for a line running as ADSL2 or ADSL2+, since ADSL2 is up to 12Mbps, which is more than the maximum ADSL1 is capable of. I think ADSL_G.dmt.bis is the whole of the modulation field, I expect it would say ADSL_2plus if it were ADSL2+.
Anyway, so RadioFox's ADSL line rate was slightly higher when connected to the test socket. In that case, I suppose there is room for improvement with the internal wiring. Disconnecting the extension wiring from terminals 3 and 4, leaving only 2 and 5 connected, might help. A filtered faceplate for the master socket may also make an improvement.

[#3]

Quote

What kind of actual download speeds do you get with that atten figure?

As I am on ADSL1 on a 20CN (ADSL_G.dmt) I am bound by bras profiles http://www.kitz.co.uk/adsl/IPprofile.htm#IP_and_bRAS_profiles; so for a synch 6816 I only can max out at 6 Mbps.
EDIT correct synch figure

[#4]

I fitted an Openreach Mk3 filtered faceplate on Friday. It appears to have improved the upload speed slightly, but has done nothing for the download speed.
I appreciate all the technical explainations of the readings I have supplied, but at the end of the day I'm still dissapointed that I'm getting 1Mbps less than with Sky, & 1.5Mbps less than BE with "actual" download speeds.
I also understand that Plusnet can only give estimates before you are actually connected, but my 7Mbps estimate also says "This may vary between 6Mb and 8Mb". I assumed that this tolerance should take into account the fact that the original figure is only an estimate. My current BTW speed test shows 4.65Mbps.
Of course, my 2 previous providers were LLU, so I assume that for some reason BTW equipment works differently & that I will just have to live with it. 
If I was previously getting, say 8 - 10 Mbps, & lost a meg or 2 download speed, I wouldn't be as bothered, but as I said before, with my relatively slow download speed anyway, every meg is valuable when downloading large files.

[#5]

RadioFox,
I missed your post on the extension wiring...

Quote from: RadioFox

I do have 4 wires connected to the lower faceplate to an extension socket upstairs. The wires are orange, brown, green, blue (from top to bottom).

There ought only to be 2 wires (terminals 2 & 5) connected and the colours of the wires indicate that the extension is not using the better standard twisted pairs cabling.
I am starting to wonder if the depressed DATA speeds are due to a local problem, known a REIN and discussed on the BBC R4 You and Yours programme today - http://www.bbc.co.uk/programmes/b055fzm0
Are you up to running some detailed monitoring?  If yes, please down load RouterStats (full product) from here - http://www.vwlowen.co.uk/internet/files.htm

[#6]

Now that I've fitted an interstitial filtered faceplate, is the ring wire still an issue? There's no problem removing the wires from 3 & 4. I will still do that of course. I'm just wondering if it makes a difference when a filtered faceplate is fitted.
Thanks for the REIN  link. I've just listened to it. Very interesting.
I have the new 2704N router. Does that work with RouterStats? There's a thread in the hardware section which says that it doesn't.

[#7]

I thought the ring wire being connected, and even the older standard of cable used for the extension wiring, shouldn't make much difference, now that it's filtered at the master socket. If you disconnect the ring wire from 3, since you no longer need to use a plug-in microfilter at the extension socket, you might want to check that the phone plugged in there still rings without it.

[#8]

Yep. I've now removed the wires from connectors 3 & 4. I've checked both phones in the house & they still ring.
I soft-reset the router & have attached some readings. I meant to take some readings before I did it but forgot.
I'm a bit confused as to what the difference is between "Attainable Rate" and "Rate" in the router stats. Sometimes "Attainable Rate" is the higher of the readings, & sometimes it's "Rate"?
It looks like both have increased by almost 1Mbps since the last figures I posted, even though speed tests have hardly changed.

[#9]

That is a big improvement but you will need to wait for this to update to get the new speeds https://portal.plus.net/my.html?action=data_transfer_speed

[#10]

OK. I'm not going to touch anything while it's like this LOL.
Any idea how long it will take to update?
With my previous providers it used to be instant.

[#11]

unless it gets picked up here  or you phone in - probably overnight

[#12]

Hi RadioFox,
Really good to see that the changes you have made are now delivering a synch speed which is right on the nail for your line's reported attenuation.  Can you redo the BTw speed test and do the further diagnostics.  It should report a profile around 5.66Mbps.  Unless that is shown there, thePlusNet profile will not update as expected to 5.6Mbps.
That should give you a little more data speed.

[#13]

Yep. The BTW diag is now showing an IP profile of 5.66.
btw...I did try to get the 2704N to run with RouterStats, but it wouldn't work.
I do have a Thomson TG585v7 (supplied by BE), & a Netgear DG834GT with DGteam firmware (which is what I was using until I switched from Sky & joined Plusnet). I could configure the DG834GT to work with Plusnet & run RouterStats, but I think I will let things settle down a bit before changing routers.

[#14]

Current line speed now showing as 5.6Mb on Plusnet site.  
It was 4.8Mb yesterday.

[#15]

Nice result, good to see that this is now sorted!