Fried 250DR?

Just listening to music in my biamped system (Supernait 2 serving highs and 250DR serving lows of B&W 803D3’s) when the low end cut out.

I noticed the 250DR’s display had gone out and so turned it off but in doing so found the unit’s casing to be hot to the touch, almost to the point of it being too hot to touch for more than a second or two.

I suspect this will be a return to Naim job but thought I would ask whether anyone else here has experienced the same?

The amp is just under two years old and connects using Witch Hat Phantom cables. Music was playing at around the 9 o’clock mark.

Thanks in advance for any thoughts.

Don’t panic. Heat cut-out has probably activated due to the heat (>70C?) and likely over-driving (not uncommon). Have a read of the manual.

Give it about 15 mins and it should return OK.

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I’ve no experience with bi-amped systems, noting Naim don’t recommend doing this.

My headline observation (post reading some data on the B&Ws) is that they may not be a friendly load for the 250DR. B&Ws are notorious for being very demanding of the amps connected to them i.e. they need higher-power-rated amps, in order to effect proper control.

Thanks HL. 250DR has now indeed righted itself so emergency is now resolved.

I think you’re correct that the 803’s might prefer a higher wattage but the 80 watts of the SN3 and 250DR are both within B&W’s spec’d range.

The SN2 has a biwire output so Naim’s view on biamping seems to have shifted if there were previous reservatons. Thankfully the amps and speakers have played nicely up until now so will keep fingers crossed this wss a one off.


Specs are not the full story - far from it.

But - IMO - any speaker which can take out a Naim 250 should be shown the door.
My 250 has never overheated or cut out - since 1985.


Good news – and pleased to hear it appears a one-off.

It could be that what you were playing had a very low/awkward frequency in it, especially if it was a digital source. This can play havoc with demands on an amp. The easier load is from the tweeter and the current demands of the bass units etc, can swing dramatically and often well below the cited 8 ohms for the speakers.

When the larger B&Ws are reviewed by mags et al, they generally use upper-end power amps (often 250wpc in to 8 ohms) i.e. in Naim-land, that’s far more than a 500DR!

Yes, the 803’s can drop below 3 ohms I’ve read and the CD was The Cure’s rather bsssy live set. I’ll probably check the casework of the 250 for the next few listening sessions and see how things go from here on.

Is the 250 DR on a rack with plenty of air around it or in a cupboard? I had a 250 and it used to cut out when played at sustained volume.

I also had it in a hifi cupboard and moving it to a rack helped.

Now have 2 x 135s with fans and no problems.

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Hi. Its on an Atacama rack with a HiCap DR alongside but open to the air on all other sides. Some Isoacoustics feet give ventilation below and there’s decent height to the next shelf.

See how you get on with it. If you like playing music loud for sustained periods you may consider a different amplification set up.

I am not sure a biamp set up is best way of getting what you want.

A 282 HiCap 250DR should sound better.

My 804D2s are often similarly-described as ‘difficult to drive’ for similar reasons, but I can drive them very loud (~100dB) and my 200 doesn’t seem to break a sweat.

Assuming the amp is well-ventilated, I think the idea of just keeping a weather eye on it over the next few sessions will suffice.


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


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.


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 :frowning: