I’ve a pair of Nap 300drs running my SL2s, speaker cables are 8.5 ms. and the amps are 3 years old. The LF amp runs quite hot at times whereas the HF amp remains relatively cool and I wonder should they be swapped after a few years or is it best to let them keep doing what they’re used to. I’m just about to do my 6 monthly connection cleaning so it would be an ideal time to swap them over. The PSs seem to run about the same temperature.
2 Likes
That’s an interesting thought. I run 3 NAP 250DR into Isobariks. I can’t say I’ve noticed any difference in running temperature across the three. I don’t see how it could possibly hurt to rotate them though. I might do that next time I do a strip down and rebuild. It’s not something my back enjoys anymore.
1 Like
It would certainly be interesting to see whether the one running hot still runs hot when swapped to HF duty.
FWIW, I’ve never known any Naim amp run particularly hot driving SL2s, except possibly when there has been an issue somewhere.
2 Likes
Perhaps I should swap them and see ! I do listen quite loud and long at times, often 10 to 11 o’clock on the 552 and for 6 to 8 hours. My main concern is am I likely to need a recap sooner if one amp is working harder than the other ???
AFAIK, no - recapping is purely time based.
I have used CB, Olive and Reference Nap 250s in my active system at various times. Only one ever ran hot and it needed a recap.
Recap - 10-15 years is fine IMO. If you get any quiet buzzing or it goes a bit dull - Recap!
I’d leave them doing duty on what they are now - I find Amps tend to ‘run-in’ on what they are being exercised to do in duty and you may find swapping puts that back a bit - but no harm trying!
My amps never get warm no matter what level but that may be the large heatsinks and plenty of airflow around them in their Fraim stack. The PS box should not get warm as it is not really spending the current into the Speakers like the Head Unit box.
DB.
Slight drift, but the one thing which has always seemed counterintuitive to me now that I have the SNAXO 242 potentially allowing me to use 2 different amps in the future (say NAP 300/NAP 250 rather than NAP 250/NAP 250), is why the better amp should traditionally be placed on HF duties?
If the LF amp here is hotter as it is ‘working harder’ would that not suggest the more powerful amp would be better on LF duties?
It’s far from certain that the LF amp in the current case is hot because it is working harder!
Not being an expert on active, I would guess that normally the better amp is on HF duties because upper bass, mids, and treble carry the majority of the information we hear, and better accuracy is probably rewarded more in these ranges.
1 Like
I don’t exactly know why (Suedkiez may have it though), just that whenever this has been tested, it invariably always sounds best that way.
1 Like
Yes, the hotter amp may be hotter for some other reason, but the reason I suggest it’s counterintuitive is simply that I’d imagine the larger mass of a mid/bass driver requires a bit more oomph than the tweeter to move and thereafter control.
Interesting isn’t it. I just find it counterintuitive that’s all, hopefully one day I’ll be able to compare for myself. I wonder how many use Naim active systems in an ‘unbalanced’ manner when it comes to power amps.
@Xanthe - any thoughts?
I’d also add that when being cautious connecting the speaker cables in active configuration to the SBLs I generally only connect a cable to mid/bass drivers initially to determine it’s actually LF not HF as again my conventional understanding is that hooking up LF to a tweeter might damage it, though in reality why not the other way around? 
Also, I’d say that unless something is amiss, the sound coming from the tweeters in isolation is pretty devoid of upper bass/mids and almost like white noise, but adds so much extra if you listen to the mid/bass in isolation it’s uncanny.
1 Like
Has it always been this way?
That the bass one runs hotter is hardly surprising if that is only when playing, as it takes a lot more energy (power) to drive bass cones (assuming the music has bass!). Whether there might be change in the one that runs warm has changed with respect to the cooler one would depend on how stable the electronic components are with heat, but I would be surprised at permanent change at the moderate temperatures inside, though conceivably one amp may reach the point of requiring service a tad earlier than the other. But swapping to try surely is very easy, though telling for certain if there is a difference may not be easy!
Simple - bass energy is far higher, and tweeter voice coil much more delicate.
1 Like
in a 3-way system, if the amps are different in terms of clarity the better one is generally best on midrange, because that is where most critical detail in the music lies. In a two- way system that may mean the tweeter as it may go down more into the midrange. But if the amps are of identical clarity but different power, the most powerful should be at the bass end because that is where the power is needed. If you look at the speaker manufacturers who make active systems, e.g. ATC and PMC, you will see that is what they do. For every 100w required on bass in a 3-way system, the treble may typically require only require something like 5w, and midrange somewhere between.
1 Like
That’s the logical and likely correct answer - just thinking from a different perspective though could a mid/bass driver be damaged by inability to cope with high frequency excursions of the driver - hypothetical perhaps if at far lower ‘power’, though don’t many of these units have fluid cooling?
I think you may have nailed it in terms of it perhaps being more applicable to 3 way systems where the mid driver will be optimal hypothetically. My own personal view with the SBLs is that the better NAP would be optimal on the mid/bass driver rather than the tweeter simply as the tweeters seems to offer very little high midrange (unless my SBLs are borked!).
I would imagine (from a layman’s point of view) that although a tweeter is much smaller than a woofer, its mass changes direction thousands of times per second, much more rapidly than the larger unit, and this might place greater demands on the amp.
It’s interesting, perhaps, that Dynaudio seem to use the same spec amp for each driver on their active speakers, whereas ATC use much more powerful amps on the LF drivers.
1 Like