It looks like your centre channel speaker has wire links between the terminals of the treble and bass sections of the crossover so you’ll have a single run of speaker cable from the 145 to the speaker.
If you remove these links, you can power the speaker using both channels of the 250 and using two runs of speaker cable. Connect one channel to the treble section terminals, the other channel to the bass section terminals.
You’ll need a rewired input cable to feed both the Ch1 and Ch2 inputs of the 250 with the mono output from your processor.
Are they tacked to joists or laid free? If the latter, you should be able to attach a fishline to one end, pull the old cable and fishline through and then attach new cable to the fishline and pull it back the other way to lay a new cable.
The golden rule for cabling under floors and behind walls is always always always use trunking.
Use your existing NAPV145 if it has been serviced as you indicated, with your existing speaker.
You will get no extra benefit from using two channels into your existing centre speaker.
Consider trade in NAP250DR for a NAC252, which will benefit your NDX2.
Alternatively, depending where you want to end up, put a PS on the NDX2, if a NAC upgrade will follow.
Improve source first, then if funds are limited, sort the NAC before upgrading the two channel NAPs, in other words leave all else alone.
Bi-amp, bi-wiring is not a Naim thing at all!
Lots of threads on here, try a search.
I’ll ask my builder if he thinks he can run another cable. In the interests of domestic harmony I don’t think I can run one across the room over the floor.
One channel of a 2020 250DR must be better than an 18 year old 145? Might be overkill but I the centre speaker is the most used when watching movies and the HTM2 could use the extra grip the 250 would provide.
The 145 is effectively a 4 year old amp as it was serviced in 2020. It’s a very good (mono) amp.
Best to try it for yourself with the 250 though and see what you think - you can use the input cable you presently use with the 145 and use the ch1 (left) speaker output on the 250 to try this out.
If you go this route then getting another speaker cable in and using both channels of the 250 for the centre speaker would be the way i’d go. That’s quite a speaker you’ve got there for the centre.
Consensus seems to be that there is no benefit from using two channels into the centre, but part of me wants to keep the newer and more capable amp, if at all possible?
A second cable to the centre speaker is going to be a challenge. Trying the ch1 from the 250 might be do’able, so I’ll try this at the w/e.
For context, I’ve just done the 282/250 to 252/300 upgrade, but I’ve not yet connected the 252/300. Rest of the system is:
NDX2/TP XPS
NAC252/TP Supercap
NAP300 > B&W803D3
NAPV 145 > B&W HTM2D3
NAP100 > Neat Iota Alphas (side & rear)
NAP100 > MK inwalls (ceiling)
Marantz AV8805 for movies (using AV bypass for 2 channel)
If not the 250, would an old 135 or even a 300 work with the centre? I could then px the 145 and 250 for one of these?
Just a thought but while you are trying things out this weekend why not swap out one of the NAP100 for the 250 ? No idea if this would make a major or minor difference but it shouldn’t be much effort. As for replacing the 145 with a 135 - I have two of them for front R&L and hopefully sometime way into the future they will pass on to one of my sons
Interesting, I’d not thought of swopping a 100 for the 250. I’m sure the Neat Iota Alpha’s would sing with a 250.
Given the limited sound that comes from the rear channel however, a 250 is probably even more overkill than my original idea of putting it on the centre!
A 135 is not a bad idea, but not sure I’ve ever seen anyone selling a single 135.
The simple answer is, if it ain’t broke, fixing it isn’t necessary.
I think you run the risk of causing a two channel amp to become unstable, if you only use one channel.
Use your single channel amp for a single speaker if AV is the source, the NAP will not improve the source!
To reiterate, source first, room for improvement with your ps - scap dr on 252 + ensure all key units are up to date with servicing.
