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NAD C355 problem

BrokenEnglishGuy

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Hey hello, i have a problem with my setup: nad c355 + kef r300
i sended a email to nad, and in the end nad says:
Hello,

Thank you for your patience.

Our NAD Specialist has gotten back to me with the following:

- All NAD stereo & HTR amps are designed for 4 ohm ~ 8 ohm loads. Less than 4ohm loads will cause the protection circuits to trigger and could eventually burn out the amplifiers. 2~3 ohm speakers will push the amps past their continuous power limit.​

Hope this helps!

Kind regards,
Support Crew Analyst

i sended back another email saying i never get a protection mode, maybe because im a low volume listener... the max volume that i use is 1/3 with this nad, the amp just feel very powerfull...
but they say
I have reached back out to our NAD Specialist about playing your speakers at moderate volumes, and he has said the following (paraphrased):
''Playing at lower volumes (7~8 o'clock) actually stresses the output transistors more than playing at full volume.


This combined with 3.2 ohm speakers is pushing the C355 beyond its red line. ''


As such, we would still advise you not to use these speakers with your C355BEE.


My unique question is, well i never get that protection mode.. and well i like how my R300+ C355BEE sounds.. :/ i saw the marantz pm6006UK for potential upgrade due this problem, that amplifier will have this problem too ?


thank you
 

restorer-john

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You haven't told us what the actual issue is.

Make sure you turn off the soft clipping switch on the rear panel, play the amplifier and speakers and tell us the problem.
 
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BrokenEnglishGuy

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the problem is nad doesn't recommend drive the r300 because it might cause damage to my c355 :(
'' unning your C355 with your R300 may cause the C355 to go into protect mode and, for extended time, may cause damage to the amplifier in the C355 if this occurs multiple times. So there is potential that continuing to your your R300 with the C355 may cause damage to the C355. ''

i don't have any issue.. but nad says it might damage my amp..., my kef is 3.2ohm
 
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CDMC

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I think you are looking for a problem where none exists. Per NAD's own brochure, the C355BEE is designed to drive both 4 and 8 ohm speakers. Most 4 ohm speakers drop below 4 ohms. NAD knows this and in fact rates the C355BEE as having an IHF Dynamic Power at 2 ohms of 270w.

Your speakers are not a hard load never going below 4.25 ohms: "Impedance reaches a minimum of 4.25 ohms at 158 Hz and a phase angle of –28.40 degrees at 4.7 kHz." https://www.soundandvision.com/content/kef-r300-speaker-system-ht-labs-measures
 
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BrokenEnglishGuy

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i really wish this problem that Nad is talking about doesn't apply in my case... because i don't wanna spend money in things like marantz pm8006 naim, and those 1000usd things... but at the same time i don't wanna damage my nad
 

NTK

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You would think the NAD product support staff actually know something about their products :rolleyes:

NADC355.JPG
 
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Wombat

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Given that there are four weasel words/qualifiers in the short quote attributed to NAD it seems that they were being non-committal whilst wishing to sound authoritative. Not uncommon 'customer service speak'.
 
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BrokenEnglishGuy

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You would think the NAD product support staff actually know something about their products :rolleyes:

View attachment 84157
i thinked the same they hve that powerdrive and those 2 ohms things ( but im not amplifier maker or anything like that so my opinion isn't too important ) also i use the speaker in nearfield so i don't need a lot of volume and i never go into the protect mode, i don't know what thing the amp do because i never saw my amplifier get into protect mode

but then they said '

Playing at lower volumes (7~8 o'clock) actually stresses the output transistors more than playing at full volume.





This combined with 3.2 ohm speakers is pushing the C355 beyond its red line. ' ''

Well apparently listening in low volumes it's worse.. i don't know.... i thinked because of i listen my speaker in moderate volume the amplifier have a good amount of reserve power.. i just move the volume a little in my nad and the speaker get loud instantly
 

NTK

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...
but then they said '
Playing at lower volumes (7~8 o'clock) actually stresses the output transistors more than playing at full volume.
This combined with 3.2 ohm speakers is pushing the C355 beyond its red line. ' ''
...
I am no amplifier designer but what NAD product support said doesn't make sense intuitively nor from my experience. You can either believe NAD product support is more honest than NAD marketing, or believe that the product support person replying you doesn't has his/her act together. You are free to confront them with their contradictions.
 

CDMC

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Given that the NAD rep doesn’t even know the minimum impedance of the speakers is 4.2 ohms and incorrectly states that driving speakers at a lower volume is harder on an amplifier than at high levels, it is clear the person has no ideawhat they are saying.

To the OP, an amplifier puts out a set voltage for an input. It’s ability to drive a low impedance load is limited by its current capability. Not enough current and voltage sags. This occurs as you get near clipping. Do it hard enough, the amp will shut down. At low volumes, you could drive a .5 ohm speaker, as the current requirement to support the voltage will be far lower than what is available.

You are worrying about nothing. You are driving a speaker that is not a hard load with an amp that is capable of driving far low impedances. Again, enjoy it and quit worrying, the NAD customer support person gave you inaccurate advice.
 
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BrokenEnglishGuy

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Given that the NAD rep doesn’t even know the minimum impedance of the speakers is 4.2 ohms and incorrectly states that driving speakers at a lower volume is harder on an amplifier than at high levels, it is clear the person has no ideawhat they are saying.

To the OP, an amplifier puts out a set voltage for an input. It’s ability to drive a low impedance load is limited by its current capability. Not enough current and voltage sags. This occurs as you get near clipping. Do it hard enough, the amp will shut down. At low volumes, you could drive a .5 ohm speaker, as the current requirement to support the voltage will be far lower than what is available.

You are worrying about nothing. You are driving a speaker that is not a hard load with an amp that is capable of driving far low impedances. Again, enjoy it and quit worrying, the NAD customer support person gave you inaccurate advice.


Kef affirms the min load is 3.6 by his specs
''
ModelR300DesignThree-way bass reflexDrive unitsUni-Q driver array:
HF: 25mm (1in.) vented aluminium dome
MF: 125mm (5in.) aluminium
Bass units: LF: 165mm (6.5in.) aluminiumFrequency range (-6dB)42Hz – 45kHzFrequency response (±3dB)50Hz – 28kHzCrossover frequency500Hz, 2.8kHzAmplifier requirements25 – 120 WSensitivity (2.83V/1m)88dBHarmonic distortion
2nd & 3rd harmonics (90dB, 1m)<0.4% 130Hz-20kHzMaximum output110dBNominal impedance8Ω (min. 3.2Ω)Weight12kg (26.4lbs.)Dimension (H x W x D)
(with grille and terminal)385 x 210 x 345 mm
(15.2 x 8.3 x 13.6 in.)
''
 

CDMC

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I am going off the actual measurements as I posted above.
 
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BrokenEnglishGuy

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Well, nice to hear the nad advice was wrong.. no problem with that
I will keep using my setup, i really want to enjoy my toys :) not keep buying
 
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BrokenEnglishGuy

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Reading the manual i discover this
''
POWER AMPLIFER SECTION
Continuous output power into 8 Ω 2 80W (19dBW)
Clipping power (maximum continuous power per channel 4 Ω and 8 Ω) 92W
IHF Dynamic headroom - 8 Ω +2.4dB 4 Ω +4.4dB

IHF dynamic power (maximum short term power per channel) - 8 Ω 140W (21.5dBW)
4 Ω 220W (23.4dBW) 2 Ω 270W (24.3dBW) Damping factor (ref. 8 Ω, 1kHz) >160
Input impedance (R & C) 20kΩ+ 1nF Input sensitivity (rated output into 8 Ω) 940mV Voltage gain 29dB Frequency response 20Hz - 20kHz ±0.1dB Signal/noise ratio, A-weighted 105dB (ref. 1W ) 124dB (ref. rated power) THD + Noise 3 <0.02% SMPTE IM 4 <0.01% IHF IM 5 <0.01%
''
Cath my atenttion the '' max continuos power per channel 92w '' it's nothing wrong with that, right?
Apparently the amp can push more power but sometimes not continuous, but i think this is how it works in every amp..
 

CDMC

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Reading the manual i discover this
''
POWER AMPLIFER SECTION
Continuous output power into 8 Ω 2 80W (19dBW)
Clipping power (maximum continuous power per channel 4 Ω and 8 Ω) 92W
IHF Dynamic headroom - 8 Ω +2.4dB 4 Ω +4.4dB

IHF dynamic power (maximum short term power per channel) - 8 Ω 140W (21.5dBW)
4 Ω 220W (23.4dBW) 2 Ω 270W (24.3dBW) Damping factor (ref. 8 Ω, 1kHz) >160
Input impedance (R & C) 20kΩ+ 1nF Input sensitivity (rated output into 8 Ω) 940mV Voltage gain 29dB Frequency response 20Hz - 20kHz ±0.1dB Signal/noise ratio, A-weighted 105dB (ref. 1W ) 124dB (ref. rated power) THD + Noise 3 <0.02% SMPTE IM 4 <0.01% IHF IM 5 <0.01%
''
Cath my atenttion the '' max continuos power per channel 92w '' it's nothing wrong with that, right?
Apparently the amp can push more power but sometimes not continuous, but i think this is how it works in every amp..

NADs has typically designed their amplifiers to have significant headroom over their rated power. It is rare that an amplifier will need to put out more than 10 watts continuous, even at very high volume, generally it is 1 watt or less. It is the peaks that require a lot of power. If you are playing your speakers at 84 db average (pretty loud) it takes 3 watts at a listening distance of 12 feet (4 meters). Throw in a moderate 10 db peak, and your amp needs to put out 30 watts to reproduce it. Make that a 15 db peak (higher than most pop music, but very common with classical music) and that power requirement is now 100 watts. A big 20 db peak, 300 watts.

Given you stated that you listen at low volume, it is highly likely you never use more than 10-20 watts on peaks.
 
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BrokenEnglishGuy

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THANK YOU :):):):):D
Happy to see my amplifier is good and can drive my kef r300 properly without get damaged
 
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