Thanks for your input all, appreciated.
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Why not just use naim speaker cables ?
Also the better amp should be on the tweeter not the woofer
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That’s the reco with an active set-up (Naim’s speakers are generally amp friendly) but with bi-amping it may be different (?), as it’s the bass units which can generate the higher current demands (more suck-out) when the volume is increased. I think it depends on how the speakers’ X-overs work when in bi-amp mode. B&W’s manuals don’t seem to cover what happens in bi-amp mode.
If the cited potential 3-ohm load for the B&W’s is accurate (they are cited at 8-ohm in single-amp mode), then the potential for issues with a 250-model (even a DR one) is obvious.
If you haven’t read this, it may give you some additional perspective on bi-amping:
Naim only don’t recommend biamping for quality reasons. They don’t believe it’s detrimental, just not beneficial. But it is useful for power handling reasons where one amp is insufficient. And if I recall correctly, B&W needing to be bi/tri-amped is a known use case.
Indeed - when my 804s are connected to my home cinema amp, I’ve set it to bi-amp them. I feel this is a better use of the spare amp than expanding my surrounds to 7.1, although the pushback I’d get from the domestic inspectorate if I tried to put an extra two speakers up on the walls is also a significant factor in this decision.
Mark
Another music session last night, this time Keb Mo whose tunes feel right played at lower volumes. No problems with the 250DR cutting out or it’s casing remained cool throughout as was always the norm until the other night playing The Cure’s Live at Hyde Park set at volumes no different to what I sometimes play live rock/metal recordings at. Loud admittedly, but not exceptionally so.
The Cure set is quite bassy so maybe there is something in the B&W’s not being a perfect match for the 250DR under exceptional circumstances.
In any event, I’ve decided to take advantage of a home loan of a McIntosh amp which at 300 watts per channel is at the other end of the spectrum and I believe has a warmer presentation than Naim. Time will tell if it matches better with the B&W’s and is more to my taste.
Stuff like Keb Mo is generally undemanding, as there’s only modest bass and it’s mainly mid-range music replay. The move to a Mac amp is sensible IMV (much softer sound than Naim but the additional power will compensate – see on). In summary here:
1- don’t trust the published specs on speakers (B&W cite amps of 50-500 wpc here) as these can be highly misleading and the bare data alone isn’t appropriate when matching amps. Stating a speaker is an 8-ohmer is clearly incorrect when reviews identify an impedance dip to 3-ohms – and this really matters.
2- if you have an underpowered amp, you can damage a speaker — Naim amps include protection circuits which prevent this. You’re probably aware that NAP300s/500s (135s of yesteryear) all have fans and also protection circuits.
3- you are far better of using higher-powered amps, as these control & grip the speaker far better, and will sound far better. Often it can be transformational, as the bass performance is what often contaminates replay, can aggravate room modes et al (a ‘tight’ bottom end is good!).
Sadly, Naim amps (bar Statement) are modestly powered when compared to some competition, which is a limitation imposed by their design briefs/technology adopted, hence why Naim also advocate use in active mode, with a very limited range of speakers.
To be honest, while a NAP250DR appears to fit the specs, it really, really doesn’t.
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Seems we agree on all fronts HL. This despite the HiFi+ reviewer proclaiming the 803D3s a good match with the 250DRs (he did go on to say higher power delivered benefits). I enjoy hifi mags but never use them for anything more than research for potential shortlisting and view them as advertising vehicles for the most part.
As for the McIntosh, it sits on my equipment rack unable to get itself out of standby despite the efforts of myself and the installer to rouse it. Not the best of starts for McIntosh 
Wakey, wakey Mr. Mac …
Sadly, many of us have had to learn about speaker & amp matching the hard way e.g. only when you hear a powerful amp with more modest speakers, do you understand what the true hierarchy should be. The car engine analogy plays here in that for comfort it’s best to have a high-powered engine which operates within its comfort (revs) zone rather than one which is having to rev hard much of the time. As a rough financial proxy, I’d say the amps should cost 2x the speakers (ideally more).
Reading the HiFi+ review, it seems the 250DR was hooked up passive (not bi-amped), which would have been OK with very undemanding music, even at reasonable volume, but this is not a true test. The ATC P1 the reviewer said was better is 150wpc in to 8 ohms and even that is modest for the B&Ws – as you say, treat reviews with caution!!
FYI, I ran a pair of Dynaudio speakers with a 72/140 and then 52/250. The improvement was material but, even then, the 250 would shut down as the Dyn’s must have a nasty impedance dip when played with gusto (they are cited as ‘stable 4-ohms’), such that the 250 got toasty hot!
The trials and tribulations we must endure in this hobby, eh.
Thanks again for your thoughts.
Every amp has it’s limits. While it is true that Naim amps have a transient current delivery that is unmatched in each amps’ power class, people often totally misunderstand that and talk aboout things like “Naim Watts”. You even hear things like “75 Naim watts is like 150 from somewhere else.” Except, no, it isn’t. 75 Naim watts is 75 watts. They have far more grip and control than a similarly powered non Naim amp but they still must be paired with speakers in their weight class.
Luckily, Naim power supplies do have 3 pre outputs on them. Since going for significantly more power with Naim is hugely expensive, doubling/trippling up on the same amp, while certainly still expensive, is far more doable.
But you’ll always have to match speakers and amp, and room. The latter has a huge impact on driving ability not just sound quality. The volume of space being filled to what sound pressure at what listening position can make one scenario drive the desired volume with the dial at 9 O’clock while another needs 11 O’clock in a different room to achieve the same thing. Yet hardly anyone remembers the room as a factor in speaker driving requirements.
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The 250 dr should be the tweeter
The bowers should not be biamplified
Last but not least why not try with naim speaker cables
Blimey
As wonderful the NAPs are, a partner to difficult loads they are not. Exception being the Statement, evidently.
A great example of how much juice is needed to really saturate a speaker and make it sound as intended is having a look at Dynaudio passive / active speakers offering.
Evoke 50 are 4ohms / 87dB speakers. A 250DR will move them, sure. A 300DR even more so.
But then check out the Focus 50 which is the active version of the Evoke (same drivers). They use 670W worth of amplifiers to drive them. Do you still want to get the NAP 500 and try driving them?
Even my QB has 300W of amplification.
Naim amps are load tolerant, however the main issue here is that the NAP250 is a very rare beast in being a fully regulated power amp (same for the NAP300 and 500). This effectively means that the power amp’s performance is held tightly and not allowed to “slide” like other amps when the going starts to get tough. To that end, when things do get tough it has to work very hard, which creates heat, and so it’s far more likely that you’ll be hitting its thermal limits (and triggering thermal protection) than anything else. That’s one big advantage offered by splitting things into two chassis, as in the NAP300, and thus being able to fit in extra heat sinking and also fan cooling.
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As is part of the fun in this hobby, one question elicits multiple viewpoints.
Tried the 250DR on the HF. Both me and my dealer agree, works better on the LF.
From the B&W 803 handbook…“bi-wiring can improve the resolution of low frequency detail”. Ergo, biamping should take this a step further (and in my own hands-on experience does) but as HL notes, specs and manufacturer/reviewer statements aren’t everything.
Tried NACA5. Prefer Phantom as I find it more relaxed and to my liking and it is built to Naim specs by ex-Naim staff with favourable comments on this forum which I concur with.
Thanks for your thought though.
Agree…the room has a significant impact. My own (not too large) room is treated with GIK Acoustics panels and bass traps on all four walls and ceiling They control bass nicely and strike a good balance between not too lively/not too dull, plus the system images well.
I’d add the benefits of an electric recliner chair. Upright and I’m between the tweeter and mid, reclined I’m between the mid and top woofer. There’s certainly a difference. Footers under the front spikes could of course produce a similar result to the latter case by tilting the baffle upwards but is not something I’ve experimented with…yet.
I’d be more concerned about my hearing than getting a new amp if you’re overloading a 250.
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When I got the Magnepan LSR+ which are (small but still) fullrange 4ohm ribbon speakers with low sensitivity the word was I needed bigger amps. I was supplied with one big Bryston and one big Parasound on loan. None of them light class D playthings but real class AB. I then stubbornly tried my 135s which sounded faster and with better grip than the big americans. When we played Madonnas Material Girl lossless from Apple Music I had to check the speed settings on iTunes - sounding very fast. Not even the last act of Wagners Göttterdämmerung at volume made them clip, slip or start the fans.
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