Corsair CX650M PSU Review

Efficiency, Temperature, And Noise

Efficiency

Our efficiency testing procedure is detailed here.

Using the results from the previous page, we plotted a chart showing the CX650M's efficiency at low loads, and loads from 10 to 110 percent of its maximum-rated capacity.

Compared to Gold-rated power supplies, the Bronze-class CX650M doesn't stand a chance when it comes to efficiency performance. But as you can see from the comparison graphs above, it is way ahead of the similarly-rated Antec VPF650. With a little tuning, the CX650M could meet the 80 PLUS Silver requirements as well.

Efficiency At Low Loads

In the following tests, we measure the efficiency of the CX650M at loads significantly lower than 10 percent of its maximum capacity (the lowest load the 80 PLUS standard measures). The loads we dialed were 20, 40, 60 and 80W. This is important for representing when a PC is idle, with power-saving features turned on.

Test #12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan Speed
Fan Noise
PF/AC Volts
11.205A0.491A0.484A0.195A19.6664.16%840 RPM
27.7 dB(A)
0.905
12.119V5.032V3.296V5.095V30.64115.1V
22.433A0.990A1.000A0.391A39.7476.01%840 RPM27.7 dB(A)0.953
12.115V5.030V3.295V5.091V52.28115.1V
33.669A1.487A1.515A5.085A59.8981.38%840 RPM27.7 dB(A)0.969
12.110V5.029V3.293V5.085V73.59115.1V
44.887A1.987A2.004A0.784A79.7283.82%840 RPM27.7 dB(A)0.977
12.105V5.026V3.291V5.079V95.11115.1V

Efficiency under light loads isn't impressive, that's for sure. However, it's satisfactory for an 80 PLUS Bronze unit. Our only complaint is the fan's speed, which could be much lower under such light loads. The fan isn't noisy, but it could be totally inaudible if Corsair dialed it down to 400 or 500 RPM.

5VSB Efficiency

The ATX specification states that 5VSB standby supply efficiency should be as high as possible, recommending 50 percent or higher with 100mA of load, 60 percent or higher with 250mA of load, and 70 percent or higher with 1A or more of load.

We take four measurements: one each at 100, 250 and 1000mA, and one with the full load the 5VSB rail can handle. 

Test #5VSBDC/AC (Watts)EfficiencyPF/AC Volts
10.101A0.5277.61%0.068
5.102V0.67115.1V
20.251A1.2880.50%0.149
5.099V1.59115.1V
31.002A5.1080.57%0.337
5.089V6.33115.1V
43.001A15.1978.83%0.442
5.062V19.27115.1V

The 5VSB rail is a nice surprise because of its high efficiency levels. It truly looks like CWT/Corsair equipped the CX650M with a very capable 5VSB circuit, which puts to shame the corresponding converters of much more expensive PSUs.

Power Consumption In Idle And Standby

In the table below, you'll find the power consumption and voltage values of all rails (except -12V) when the PSU is idle (powered on, but without any load on its rails), and the power consumption when the PSU is in standby mode (without any load, at 5VSB).

Mode12V5V3.3V5VSBWattsPF/AC Volts
Idle12.126V5.035V3.300V5.100V6.240.518
115.1V
Standby0.040.005
115.1V

Phantom power is really low, allowing for high efficiency at 5VSB under light loads.

Fan RPM, Delta Temperature, And Output Noise

Our mixed noise testing is described in detail here.

The first chart below illustrates the cooling fan's speed (in RPM), and the delta between input and output temperature. The results were obtained at 34 °C (93.2 °F) to 45 °C (113 °F) ambient temperature.   

The next chart shows the cooling fan's speed (again, in RPM) and output noise. We measured acoustics from one meter away, inside a small, custom-made anechoic chamber with internals completely covered in sound-proofing material (be quiet! Noise Absorber kit). Background noise inside the chamber was below 18 dB(A) during testing, and the results were obtained with the PSU operating at 34 °C (93.2 °F) to 45 °C (113 °F) ambient temperature. 

The following graph illustrates the fan's output noise over the PSU's operating range. The same conditions of the above graph apply to our measurements, though the ambient temperature was between at 28°C (82.4°F) to 30°C (86°F).  

Up to around 330W, the PSU operates quietly. It'd be even more so if the minimum fan speed was lower. Above 390W loads, the fan speed increases and so does the noise. In a worst-case scenario, output noise is in the 43-46 dB(A) region, which is pretty loud.

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44 comments
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  • Dark Lord of Tech
    Thanks for the review on this new CXM platform.
  • JQB45
    Looks to be better then the old CX line up.
  • Onus
    Good to see that Corsair didn't produce a[nother] Turkey with this one.
  • turkey3_scratch
    Onus why would Corsair produce me?

    Anyway I think the price/performance page shows all. This thing rocks!

    Also Jonnyguru claims it is a rifle bearing fan that has the same model # as the sleeve variant.
  • benedict78
    Does the CX650 perform the same as the CX650M? I'm not interested in modularity anyway.
  • turkey3_scratch
    The CX650 is not out yet.
  • Aris_Mp
    I have several CM and CX-M units, which I plan to fully evaluate. So far I figured that there are differences (something natural of course) in their performance.
  • Dark Lord of Tech
    Could you put the newer CXM 750W OR 850W on deck soon , as they are widely use for DUAL CARD configurations.
  • turkey3_scratch
    The 750W and 850W CXM units are basically unchanged except for a bridge rectifier upgrade. Everything else is the same. Only the CX450-650M got the major revisions.
  • Dark Lord of Tech
    Yeah I know that , but want to see one reviewed , to compare top older generations.
  • Ryan_78
    Seems cool to be a CX now. Nice
  • bettsar
    After getting such high marks from the review, why no award?
  • Aris_Mp
    The CX750M is on the test bench right now. I don't have a CX850M sample.
  • Aris_Mp
    About the award. It should have a recommendation award but as it seems we forgot to add it. On it right now :)
  • Math Geek
    good to see them making a strong performer in a moderate price range. if they drop some massive rebates over the holidays like they do most years, this will be a super buy. i'm keeping my eye out to stock up on some. looks like a very solid buy.
  • atljsf
    the modularity is nice if you have a mini itx case, i have a cx500 and some of the unused cables are a bit inconvenient so that cx650m should be nice for those with not that small mini itx cases that can fit normal size psus
  • HERETIC-1
    Corsair spend $3 more and get all Jap capacitors and you'll have a good PSU.
    Oh you have-It's called the Vengeance series.(RECOMMENDED)
  • turkey3_scratch
    HERETIC you are severely misled. Do you realize there are Chinese capacitors of higher quality than Japanese? Do you realize how much ripple a capacitors handles and the environment the capacitors is in also affects it's lifespan a lot?

    Look at the thermal shots. The PSU is significantly cooler than was expected. That is fantastic for capacitor life. If you want to persist at judging power supplies based on capacitors country (and BTW a lot of Jap caps are outsourced to China) then you will be misled.
  • HERETIC-1
    So turkey are you saying Corsair's marketing "105C JAPANESE CAPACITORS"
    on their vengeance series is not necessary?
    I am more than happy to pay a little more when I see-
    "All electrolytic caps come from Nippon Chemi-Con"
  • turkey3_scratch
    The Vengeance series is a higher end unit than the CXM at a different price category for different countries. Not really fair to compare them.

    What more.could you possibly want at the price this thing sells for? This is the best value period and you have to find the need to talk about Japanese caps without even knowing the spec sheets of these caps used.
  • 10tacle
    "Finally, the number of provided cables and connectors is sufficient for this unit's capacity. And although it isn't fully modular, the native cables are absolutely necessary anyway."

    I've never understood the logic behind a "fully" modular PSU where all cables are completely disconnected and need to be plugged in. How exactly are you not going to use a PSU in a PC without the 20+4 pin ATX and 8 pin 12v CPU power connectors going to the motherboard?

    If anything, I'd want those connected directly during manufacturing to ensure nothing is lost (output or resistance) through a transfer connector port to the two most crucial power connectors.
  • atljsf
    202972 said:
    "Finally, the number of provided cables and connectors is sufficient for this unit's capacity. And although it isn't fully modular, the native cables are absolutely necessary anyway." I've never understood the logic behind a "fully" modular PSU where all cables are completely disconnected and need to be plugged in. How exactly are you not going to use a PSU in a PC without the 20+4 pin ATX and 8 pin 12v CPU power connectors going to the motherboard? If anything, I'd want those connected directly during manufacturing to ensure nothing is lost (output or resistance) through a transfer connector port to the two most crucial power connectors.


    the idea is that if you want a longer, half meter or a shorter, 15 centimeters long cable, you can change the one that came with the psu and put the one you need

    this is what most pc builders need this days, especially with mini itx cases where space is extremely limited
  • JQB45
    2011305 said:
    the idea is that if you want a longer, half meter or a shorter, 15 centimeters long cable, you can change the one that came with the psu and put the one you need this is what most pc builders need this days, especially with mini itx cases where space is extremely limited


    So If I buy power supply "A" for my mITX build and its fully modular but the cables are to long, where do I go to get shorter cables?
  • turkey3_scratch
    Cables cost like $100.