NAP 500 Class?

I seem to recall that the reason Naim chose to go with a bridged design for the NAP500 was because they wanted a lot more power but wanted to avoid using paralleled output devices to achieve it - bridging gave them just that. Naim speakers were a benign load, rarely dipping below 6 ohms, so current into very low impedances wasn’t seen as such an issue.

Going way way back here :slight_smile: … didn’t Linn originally use bridged 250’s to power their cutting lathe?

As lnnocent_bystander goes on to say, its a characteristic of the generic ‘bridged configuration’, and typically applies to all amplifiers which adopt this method to achieve higher power output, you end up with more transistors in series in the output stage which with all other things being equal leads to higher output impedance.

There are compromises in all design topologies. It was particularly popular in early 70’s and 80’s in car stereo systems where you only had a 12V supply to play with. No doubt that has changed with the advent of low cost DC to DC converters and class D amps but I expect they still bridge class D amps for "even More Power!’

Could not find out this info, trying to find it from the manufacturer, all they state in the tech specs is the nominal resistance…

Yes, not many manufacturers publish the minimum impedance. You may bd able to find from test results by a reviewer that conducts electrical as well as listening tests.

If I remember correctly, big B&W speakers were problematic for NAP500 due to their low minimum impedance. B&W were a very popular pairing at one point but moving up to the biggest model (don’t remember the model name) wasn’t so straightforward. If my memory isn’t completely askew, the NAP300 handled them better. Wasn’t there some sort of modification offered, either for the speaker or the amp at the time???

Yes, it was felt that a pair of NAP300s bi-amping the top B&Ws could drive them more effectively.

The modification was made quite early on. It was found that something within the B&W crossover could trigger the protection in the Naim amps, so a small modification was made. FWIW, I think the mod is applied to all early models (NAP200 upwards) at service time. I’m sure @NeilS can confirm or otherwise.

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Naim amps are Class AB.

This is true for the Statement as well, correct?

I believe so, yes.

If the Statement power amps were fully Class A then they would likely heat a gymnasium.

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Only if they were in a gymnasium!

If I remember rightly the negative speaker wire does not go to the traditional ground as the unit is bridged…this is also suppossed to improve load tollerance…and drive…I am sure someone will correct me…

Yes, we always update the protection circuits if required when units visit the factory:-




@Richard.Dane what is the lowest impedance a nap500dr is comfortable with?

Naim have in the past stated that their amps are unconditionally stable. Below 2 ohms though the protection kicks in. So, I’d imagine the answer to that is not so straightforward. Especially when it comes to a speaker with a nominal 4, 6 or 8 ohm impedance that may dip down to below 2 ohms at certain frequencies (mercifully not so common).

If it were me, I’d want to match the NAP500DR with a speaker that has a relatively easy impedance curve, and one that doesn’t dip too much below 4 ohms at any frequency.


I know the website is not super reliable, but as it says “capable of prolonged output into 2 ohms with no discernible impact on performance” I would expect it to be true, and any extended time below 2 being not good.


From all I’ve heard over the years with Naim amps, I think this is the trick in speaker-matching which many don’t appreciate and, as good as a NAP500DR is, one mustn’t forget the ‘500’ aspect is combined channels in to 4-ohms.

There are quite a few speakers out there which cite high efficiency (~90db - more with Focals) but when the bass units chime in more at higher SPLs, the impedance curve can drop away, which presents a material challenge to anything but a current-pumping mono-block.

IMV, it’s a shame Naim didn’t produce the equivalent of a 500 mono – although I suppose they have with Statement (and more of course). I recognise there would perhaps be a conflict with thinking around active here but that seems to have fallen out of favour in the wider market some while ago.


I guess it is because they avoid using multiple paralleled output transistors, for claimed sonic benefit. However, given that the Statement is a bridged amp rated at 746W into 8 ohms, a monoblock consisting of half an S1, or single S1 unbridged as a stereo amp, should be capable of 186W RMS into 8 ohms, a significant improvement on the other NAPs. (And despite being bridged the S1 can apparently cope with loads at least down to 1 ohm, so unbridged should be equally happy into half an ohm or less, with 5.5 kW potentially available on transients into 0.5 ohm.)

Perhaps the cost is seen as too much of a hurdle other than for the very rich, who’d simply go for the Statement - the answer to that may be to compromise a bit with other parts of design instead of the no-compromise Statement, making it more like 1/3rd of cost instead of half.

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I found out these specs: Impedance modulus min/max (20Hz–20kHz) 3.1ohm @ 44Hz
15.0ohm @ 1.5kHz… I take it no issues here for the NAP500DR to handle comfortably… And yes, the sound is absolutely amazing so no concerns here, just the OCD in me reacting here :wink:

I know just enough about impedance to be dangerous. On my speakers, Focal Maestro Utopias, the manual from Focal stated an impedance of 4 ohms nominal, 3 ohms minimum. But elsewhere it is reviewed at a dip of 1.7, a “dip” not continuous. I’ve never noticed any clipping nor does my 500dr even become warm to the touch. The sound is great been running it for 4 years so I guess no problem.

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