I know the recommended speaker cable length is a min. of 3.5m (preferable NACA5) but I’ve been using 2m lengths of Chord Odyssey2 from my NAP200 power amp for many years. Never noticed any issues but could the short length be inadvertently damaging the amp (or speakers)? The FAQs suggests that high capacitance and/or very low inductance cables may damage the amp.
It’s possible to damage an amp with very high capacitance, such a cable will invariably include low inductance, but low inductance would not be the cause of damage as such.
The damage is caused by the amplifier output stages becoming unstable due to capacitive reactance. This can be minor parasitic ringing up to full oscillation and although the problem occurs well above the audio band it will destabilise the amplifier throughout its whole operating range. The effects can be audible distortion caused by low level ringing up to the output devises overheating and in some cases destroyed.
I use 5m per side of Chord Odyssey & because they don’t publish the specs, I measured mine & found it to be 62pF/m & 0.6uH/m. Very middle of the road & not liable to cause any damage.
Chord cables are widely used with Naim amps and have pretty good compatibility, although not quite as good as Naim’s own cable. If your system is performing well it will not be damaged by short cables, although the amp may run a bit hotter, especially at higher volumes and/or with more demanding speakers. You may also find an uplift in sound quality. Ask your dealer if you can borrow a 5m pair of properly terminated NACA5 cables and see if anything changes.
The worst combination is long very high capacitance / low inductance cables, OR short low inductance cable when used with highly reactance speaker loads that show a capacitative dominant balance at higher frequencies.
As Mike-B says, in extremis, these can damage many types of amplifiers.
The early amps like the 135 could be damaged, I had a pair which I bought s/h which I thought sounded a bit off and when serviced by Naim they contacted me and asked about my spkr cable habits as both the 135 were ringing badly. From what I understood Naim ran the 135:s without a little protection circuit (to improve sound) and instead relied on the speaker cables to provide this protection.
I wonder then why Naim Audio sells SL speaker cable in 3m lengths? Owing to room geometry I use this length on my NAP500DR. So far I’ve not detected any ill effects. Maybe I should switch to longer lengths of KS-1…
3m is the minimum recommended length of Super Lumina speaker cable.
As Jan alludes to in his post above, Naim power amps don’t have added inductance networks for stability, instead they rely on the speaker cable to provide the necessary inductance - this was found to give much better performance. It does mean though that you need to stick to Naim’s recommendations re. speaker cabling, giving a combination of low capacitance and moderately high inductance;
Worth a try, but remember that 3.5m is the minimum recommendation, optimum being 5 to 10m, and that this is specific to NACA5. Cables with different specifications, in particular capacitance and inductance, will have different, usually longer recommended lengths.
As others have explained very well already the electrical properties of the cable, determined by the conductor material and cable construction, in particular inductance and capacitance, will give you a baseline from which to determine their compatibility and suitability relative to the amplifier they are connected to.
Naim have developed speaker and interconnect cables designed to work optimally to the capabilities and design constraints of their amplifiers and provide the guidance to ensure the amplifier isn’t put under an excess strain during operation.
The characteristics of the speaker cable circuit are defined by their length hence their minimum and optimal maximum guidelines, you have a range of tollerance within those recommended lengths which should be adequate for the majority of system setups.
Most Naim owners have or do use Naim speaker cables as this gives a known quantity relative to system performance and synergy, using other brands is absolutely fine as long as the properties of the cable fall within the guidelines Naim specify relative to their own cables.
Deviating from that could under certain circumstances place the amplifier under excessive strain and in extreme cases eventually cause the amplifier to fail if used extensively with cables outside of the recommended characteristics.
In my case I ended up settling on 4m pair of NAC A5 as that was the best balance between length and cable construction relative to the rest of the system.
If space allows a 5m pair is where many owners decide to end up to give further potential for optimisation. I have a set of 5m and 6m NAC A5 but found the 4m pair was my prefered balance between system synergy and cosmetic requirements as well as the needs of the listening room itself.
There are a number of speaker cable brands/type that others have found suitable and preferable from a system synergy perspective, typically those with similar construction and design and at equivalent lengths, Chord, WitchHat and Kudos being examples.
Hi @Clive, don’t get focused on cable length, it’s the required inductance load that matters, this means a different length dependant on each different cables specs.
Naim amps want a minimum 3.5uH inductance load, NACA5 is 1uH per metre, hence why the 3.5m cable length.
KS-1 will have a different inductance, I suspect it’s around 0.6uH/m meaning 5.8m is needed to get the 3.5uH load.
Technically speaking there are a number of ways to represent this, one of the better ones being a magnitude within a five dimensional space (and even that is an approximation, albeit an approximation that is valid under all realistically viable conditions). The two dimensions in this model with which we are primarily concerned here are:
inductance to capacitance ratio per unit length of the speaker cables
the length of the speaker cables
The net upshot of this is:
1 If the capacitance of the cable isn’t excessively high
2 If the inductance of the cable is 3.5uH or more
then the amp will drive any practical load of 2Ω* nominal impedance or more without damage (including difficult loads with a capacitative balance, such as electrostatic speakers).
What Mike is saying is that, if any practical speaker cable of any practical length is used such that the inductance is 3.5uH or more, the capacitance will be low enough that the conditions above will apply. **
If the above conditions are not met, then unless the capacitance of the speaker cable is too high, this won’t necessarily cause instability; it just means that then the stability of the amp becomes conditional on the nature of the load presented by the speakers.
However, a speaker cable with too high a capacitance to inductance ratio can itself cause instability irrespective of the speaker in use.
* 2Ω applies to ‘Classic’ series power amps, for Uniti series amps and possibly for integrated amps, this may be 4Ω.
** There are also other ways of expressing this: for instance it could be expressed in the complimentary terms using capacitance as the key measurement from which the other terms are implied. However, a) this inequality statement would be more complex than the one for inductance and b) we know the design inductance criteria, we don’t know the design capacitance limitations.
The maximum capacitance depends on the cable inductance - it isn’t a single figure.
The minimum inductance depends on the total capacitance - it isn’t a single figure.
Provided the capacitance of the speaker cable isn’t too high 3.5uH will ensure stability into any practical load of suitable nominal impedance.
Below this, it may be load dependent for some Naim power amps.
Naim have a minimum length requirement based on the specifications of the cable. I am asking for a cable with a shorter length that provides the same specifications. Naim do not reccomend a 4’ pair of naca, but there might be a cable they reccomend that emulates close to the same capacitance etc in a shorter length.