I thought the fans were designed to operate only at higher outputs i.e. closer to their rated 75W, or are my speakers more power hungry than I thought? Is there a mod or tweak I can do to quieten the fans down a little? Your experiences and wisdom are appreciated.

James

The Sonuses are a relatively easy load; I had the
Amator IIs and they really rocked with the 135s at the end of them, with no "fan experiences".

Good listening; the music's still groovin'.

Philip

naimniac for life

I was just about to add that perhaps it's summer (max around 25 degrees celsius indoors) now in the Southern Hemisphere and the increased ambient temperatures might cause the thermoswitch to kick in earlier. And then I read your response from tropical Singapore (min around 25)!! Do you run your system in a fridge or at least an airconditioned room?

If only one of the monobloks was fanning itself, I would suspect a fault, but they are so synchronised with their on/offs that I somehow doubt it. Do your cases feel warm when the fans are blowing? Mine remain rather cool, if not stone cold. The 250 that was replaced was significantly warmer in operation.

James

[This message was edited by philip pang on WEDNESDAY 13 December 2000 at 04:14.]

My dealer has run his active 6 pack DBL set-up to 3 o'clock before (I daresay to the end of the volume knob) and under prolonged usage at that sort of volume (he could be partially deaf though...), that was when his fans came on.

Good listening; the music's still groovin'.

Regards

Philip

naimniac for life

I have had a pair of 135's for about 2 years now and i have NEVER heard the fans come on. If they have come on, they are so quiet i just dont hear them. My listening room is quite small (17'x 12') and i have the equipment along the long wall so i sit rather close to the amps (about 5-6 feet away) and never once heard as much as a whisper.

The only sound i do hear from the top amp (i have the two amps on the top two shelves of a 5 tier Mana stand) is a very slight hum, and the room has to be dead silent to hear this,and you have to walk up to the amp and put your ear right on top of the case to know it is coming from the transformer.

I have used two different speakers with average sensitivity. I have always used a 15' pair of naca5 speaker cables. I wonder what speaker wire you are using and what length? I understand Naim leaves certain output devices out of the amps and the speaker wire provides the proper resistence and completes the circuit,maybe this is causing your problem,or they just may need to be adjusted?

I hope you figure it out

Scot Hurwitz

p.s. the borg?

Simon

Whether they come on at a certain volume level is going to be completely dependent on environmental conditions - what the ambient temperature is, what the speaker load is and probably most importantly, what sort of music you are playing (Metallica at 9 o'clock on the dial will sink more power - and hence heat the heatsink quicker - than lone voice at 9 o'clock on the dial...).

Andy

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The first day I had them in, the fans were whirring so loudly I thought my CD player had sh*t its transport.

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Sounds like what happens when you get 135s :-)

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I don't have to play very loudly (9 o'clock on CD2/82) to activate the fans.

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Normally mine start at about 9:30 on the dial. They are whirring full-on by the time I get to 10:30 on the dial.

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The noise is not obtrusive during loud passages but in-between tracks it's very obvious.

...

Admittedly, the fans seem to have variable speeds and at lower volumes, they whirr away only slightly audibly.

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Sounds correct to me...

And

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The Sonuses are a relatively easy load; I had the Amator IIs and they really rocked with the 135s at the end of them, with no "fan experiences".

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Philip, the Amator IIs are one of the more easy SF's to drive. The Amator I was quite a bastard on amps so SF put a lot of effort in making them more amp friendly (and succeeded). I don't know which model James has. The older Electa's (which I have) are not the friendliest either but don't cause any problems for my 'little' 180.

BTW, you wrote 'had' the Amator IIs. You don't have them anymore?

Richard

My 135s are connected to SF Concertos via a 3.5m pair of NACA5 and Naim bananas, so that is within recommended specs. Philip says he had felt his cases turn warm and never heard his fans running. My experience is the converse. My cases have never felt warm - with or without the fans running.

As we all know heat is bad for electronics, I guess I shouldn't complain if they are cooled very effectively. But I just wonder if premature fan cooling might be affecting their performance if the electronics are not "warming" to their tasks. Perhaps Naim can comment?

James

are your 135s old or new?

Older 135s were set so the fans came on more easily. This can be adjusted by Naim.

I've only had the fans on my bass amps going once recently - after several tracks from James Taylor's Hourglass. (A bass heavy disc played at 12 O'Clock volume - fans going full bung). In general I don't find the cases get very warm anyway.

However, when it gets VERY hot in summer (UK) the fans will sometimes come on even when not using the system! (Can't remember if this has happened since amps were serviced and adjusted).

cheers, Martin

P.S. have you actually measured that 25c temperature?

With my ES22s (87db/watt, 6 ohm) the fans get spinnin quite readily with a couple of tracks of trip-hop or hendrix, and the amps get quite warm. My guess is that as the source/preamp gets better (cds2,supercap) there's a lot more drive and energy involved - but that's where the fun comes...

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are your 135s old or new?

Older 135s were set so the fans came on more easily. This can be adjusted by Naim.

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My 135s are current models and are about 3 years old. I haven't used any devices to measure the ambient temperature precisely, but if I ain't sweating then it can't be that warm. In any case, the 135 cases don't feel any warmer running at full steam than the other components.

I am curious, however, about the adjustability of the thermoswitch. I understand the 135s have considerably more heat sinking than a 250 and hence should be able to dissipate more kilojoules without the need for fan assistance.

Mr Murphy, do I need adjustment?

James

SF's are a little bit on the inefficient side, but I don't think they should be that hard to drive that your fans come on regularly unless you're a head-banger. Considering the speaker choice that seems unlikely.

I think you might check with Naim to see if there is a way to re-set the thermal switches. If your cases are cool and the fans are cutting on it sounds to me like they might be set wrong.

In my set-up I had the amp set on top one another and inside a cubby hole. Not the best set up for cooling.

Arthur Bye

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I am curious, however, about the adjustability of the thermoswitch. I understand the 135s have considerably more heat sinking than a 250 and hence should be able to dissipate more kilojoules without the need for fan assistance.

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I think you can get them adjusted, HOWEVER, the fans are not there only to allow you to dissipate more heat, they also keep the trannies operating at the correct thermal point.

The reason Naim amps shut down at high temperatures is that the transistors can go into thermal runaway (IIRC - this was 15 years ago I did this at Uni...). That is, as they heat up, their gain increases slightly, thus causing them to heat more, causing the gain to increase slightly etc... The fans keep the transistors gain in the region the circuit is really designed for.

Keeping them at the "correct" temperature keeps the circuit in balance. My guess is that you're more likely to get 135s to blow their output resistors than go into thermal shutdown. (i.e. the heatsinking is so big, I'd expect something else to go first).

When all is said and done though, the effect should be minimal and you may want to get your fans adjusted (so to speak...).

Andy

The adjustment really requires a test-tone setup and a digital thermometer; a specified specific load and frequency minimizes overheating of the wirewound resistors in the output network as you're setting it up.

Though the fans kick in at 44-45 Celsius, they typically turn off at a lower temperature, therefore it is possible to set the fans to turn on at too low a frequency (and thus constantly on).

Dave Dever, NANA

P.S. Do not disengage the fans (some old **** rumor about sound quality--it's a separate transformer secondary) or set the fan threshold above the specified setting, as it will shorten the lifespan of your output transistors, and increase distortion (easily viewable on an oscilloscope when sent for capacitor service).

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Though the fans kick in at 44-45 Celsius, they typically turn off at a lower temperature, therefore it is possible to set the fans to turn on at too low a frequency (and thus constantly on).

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I do tend to crank up the volume when I first play music in the evening and as the night wears on, I reduce the volume to more acceptable levels. Perhaps the buildup of heat and the lower cut-off temperature does cause the fan to run longer than I would expect. I'm less concerned about cool running than hot running, but wonder if operating the power trannies at room temperature (if my fans are indeed over-zealous) actually results in sub-optimal sonic performance. Or should I just be content that my trannies will never cook themselves and last forever?

James

Yeah, had them for a couple of months, but couldn't quite tame the mid-bass from their auxilliary bass radiator in my smallish room (approx 9ft x 11ft), due definitely to the cramped space afforded them, rather than the drive ability of the 135s. So they were sold, and I've since gotten back to my speakers from the past, the trusty SBLs. Much happier match, apparently. But having said that, given enough room to breathe, the Amator IIs would sing at the end of 135s. The 135s drive them very well. I had regular sorties with the Sonuses, with the volume set at about 2 o'clock playing Sheffield drums and just about anything I cared to throw at them. It was just really loud, but the music hung together with no hint of break up. You could feel the 135s really gripping the woofers and letting them have it. Should have pilfered a 500 somewhere to see how much more grip could be had...

>> Philip says he had felt his cases turn warm and never heard his fans running. James

I do have to say it is possible that my fans could have run on occasion without my knowing; if they have they've really been quiet... or I could be growing deaf from all the listening... But as of recent memory, they have not come on, no. The cases do run luke warm to warm at most, but never hot, even at relatively high volume (1 o'clock) for up to about 15 minutes each time.

Good listening; the music's still groovin'.

Philip

naimniac for life

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but couldn't quite tame the mid-bass from their auxilliary bass radiator in my smallish room (approx 9ft x 11ft), due definitely to the cramped space afforded them

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What a pity Philip but I know exactly what you mean. Especially the Amators (I&II) need a lot of space. Pretty amazing for such a small speaker. You only had them a few month's. Are you sure they where run in completely? This takes VERY long, as much as 6 months of intensive use. As in your experience, the mid-bass in particular needs a lot of time to integrate. Ah well, don't mind me. I've been a SF addict for more than 10 years. My Electa's are front ported and not as critical in this respect. I'm still on the lookout for a pair Amator I's in mint condition. I still prefer these (although slightly) over the II's with their magnificent and horribly expensive matched Dynaudio Esotar tweeters.

James,
While you still have your Concerto's (I recall you said something about your dealer trying to change that?), junk that NACA5 cable first! It really, really, REALLY doesn't work with SF's. My dealer gave me 2 x 3.5 mtr for free (I can imagine ) as a spare 'emergency' cable. As I've read and heard so much silly stories about the mandatory-ness of this cable with Naim amps I've done some serious listening with it. It's a fairly cheap cable so what would be nicer after all?? I like the 'all Naim approach' too. I won't comment on other speakers because I don't know but with SF it's a plain disaster. Screechy, harsh, strangled, extremely unbalanced and as flat as a pancake. A nice 10-out-of-10 score on the misery scale... Even an old'n dodgy Monster M.75 I still had lying around is a revelation. That's when it becomes scary...

You must give your Concerto's the chance to sing their beautiful voice before they go and pull that rope off their throats...

'Crazy what does he know' Richard.

P.S. Anybody interested in two pieces of NACA5 to power a light-bulb or something?