SPCR Ratings

kojak71 · Post by **kojak71** » Fri Apr 08, 2005 1:41 pm

I'm not sure if I'm perhaps misinterprating the SPCR ratings of reviewed PSUs, but I find it odd how the Seasonic S12 is rated an 8+ and the Nexus 4090 is rated as an 8. I'll explain.

Here in the United Kingdom, availability of Seasonic PSU's is extremely rare, so I've been considering other alternatives. The Nexus 4090 is readibly available, so naturally I've put in on my short list for further consideration. However upon reading the reviews, the Nexus is anything up to 8db louder than the Seasonic in the 150W-400W range! That's an incredible difference especially if you listen to the mp3 recordings SPCR have made, and yet it's only rated 0.5 points lower on the SPCR scale. What's going on guys? Or am I missing something?

Tibors · Post by **Tibors** » Fri Apr 08, 2005 2:31 pm

Yep, the 150W+ range is that part of the PSU that never gets used in a silent PC. So why weight it in the rating?

You didn't just skip over the first pages of Power Supply Fundamentals & Recommendations, did you? On page 4 is explained how much power the typical machine uses.

Green Shoes · Post by **Green Shoes** » Fri Apr 08, 2005 3:06 pm

I agree that most PCs on this forum won't use that much power, but he brings up an interesting point. Is there any mechanism in place to cope with evolving standards? Hopefully things will improve so that our idea of an eight-point PSU five years from now will be much stricter than our idea of an eight-point PSU now. Are those ratings up for re-evaluation in the future?

StarfishChris · Post by **StarfishChris** » Fri Apr 08, 2005 5:32 pm

As standards evolve the old PSUs will drop out as they become discontinued. I can't see power draws increasing much more, either.

The rating for noise should be more-or-less absolute. After all, a fanless PSU with no buzz should get 10, and the 'minimum' ambient dBA is hardly going to change. Quality would be more relative, but most PSUs score 8 at the moment and it doesn't appear to have changed much in a few years. (I think they've reserved 10s for the ones that manage 100% efficiency and absorb other PC noise by decoupling the space-time continuum.)

kojak71 · Post by **kojak71** » Fri Apr 08, 2005 6:07 pm

Tibors wrote:Yep, the 150W+ range is that part of the PSU that never gets used in a silent PC. So why weight it in the rating?

You didn't just skip over the first pages of Power Supply Fundamentals & Recommendations, did you? On page 4 is explained how much power the typical machine uses.

No. I use my rig for AV editing and gaming, so it's a pretty powerful system. I don't expect to be able to get towards silence nirvana, but there's no reason why my system can't be quieter than it already is. So taking their definition of a "high-end" system, you can add the following as per their notes (just as soon as I upgrade my CPU as well):

# The C: High P4 system could draw as much as 50~70W more (AC) with a P4-3.8 (the most power hungry desktop CPU). This would put max AC system power draw up to ~300W; the DC power delivery of the PSU at that point would be ~225W. Increasing memory by another 512mb might add 10W. Swapping the ATI 9800 Pro for the hottest current VGA card may also add another 20W.
# These numbers are quite accurate and based on empirical testing, but for argument's sake, you could say they're as much as 10% too low. The max power draw of any system we've discussed here would still be not much more than 300W DC.

So doing something as intensive as video editing or gaming, is going to move the PSU out of the 150W output range. Personally I was going to purchase a QTechnology 350W PSU (QT-03350G Gold) as those nice people at AcoustiProducts rate them highly. However it's been years since SPCR have done a QTechnology review, and although the reported acoustic noise level is impressive, I would want it to be independently verified.

Tibors · Post by **Tibors** » Sat Apr 09, 2005 9:22 am

I didn't say you couldn't build a system that uses more than 150W. But if you insist on using a 3.8GHz Prescott and the hottest video card you can find, then you are clearly building a system that is outside the spec range for the average target audience of the recommended PSU article. This is SilentPCReview, not SlightlyLessNoisySpaceHeaterPCReview. So that will reflect in the way things get rated here.

BTW If I somehow had the need for such a hot setup, then I would seriously be looking into the "put the PC at the other side of the wall" type of solutions.

tay · Post by **tay** » Sat Apr 09, 2005 9:42 am

Green Shoes wrote:Is there any mechanism in place to cope with evolving standards? Hopefully things will improve so that our idea of an eight-point PSU five years from now will be much stricter than our idea of an eight-point PSU now. Are those ratings up for re-evaluation in the future?

I agree with this, but it seems that the noise signature of PSU's is improving rather slowly. In any case you can always (thankfully) just check the SPCR review if youre looking to buy.

WRT people silencing 3.8 Ghz + 6800 cards, while agreeing with Tibors that such systems are going to be tough/expensive to silence at load, I think the Seasonics improved ability to do power these less loudly than a Nexus should be reflected more strongly in the rating numbers.

In any case noone should be buying a Nexus 3090 unless you get a much better deal than an S12. *FLAME ON*

Post by **MikeC** » Sat Apr 09, 2005 10:52 am

kojak71 has a good point. I had meant to totally revise the ranking system when I did this last revision but got so exhausted by everything that went before the lists that I decided to leave them alone for now. However, I agree that it needs to be refined.

Currently, the noise ranking is explained thus:

old noise ranking wrote:The amount of noise the component makes. Ranked from 1-10, 10 being completely noiseless, 9 being effectively inaudible, and 1 being over 50 dBA, or as loud as a PSU can be. We suspect there will never be any product on our list with a noise rank below 4: it would simply be too noisy to be of interest to us. A number rank followed by "?" indicates we have not fully verified the assessment. Any audible coil buzzing is noted in the comments.

This system limit the rankings, essentially from 6~9, which is a very tight numerical range. Why bother with 1-10 if only this range is used? So, here's what I will do in the next revision:

new noise ranking wrote:Ranked from 1-10, 10 being perfection. A number rank followed by "?" indicates we have not fully verified the assessment.

Noise: The amount and quality of noise the component makes. Ranked from 1-10, 10 being completely noiseless, 9 being effectively inaudible, 5 being ~25 dBA/1m with a benign acoustic signature, and 1 being ~30 dBA/1m. A number rank followed by "?" indicates we have not fully verified the assessment. Any audible coil buzzing is noted in the comments.

Keep in mind that we strongly weigh the acoustic performance at <200W when ranking the units for noise. This is because systems typically do not draw more than 200W, even at maximum power. Those seeking quiet systems should do everything possible to minimize power draw because low heat makes low noise much easier to achieve. For higher power PSUs, the noise performance >200W is considered as well, but the <200W is still weighted more heavily, because the vast majority of systems run at much less than full load >90% of the time. (Typically, the load is about at idle 90% of the time.)

This helps explain why a fanless PSU gets a rating of 9 when the quietest fan cooled units can get a rating as high as 8. In actual use, the difference is very marginal, as the system using a fanless PSU still needs an exhaust fan which may actually have to spin slightly higher than the one in a similar system with a fan-cooled PSU. It is only when the quietest fanned PSUs are pushed beyond the 150~250W ramp-up point of their fan controller that the fanless PSU gains a significant acoustic advantage. However, the fanless PSU system will be more stressed thermally unless it has airflow from case fans -- in which case, the acoustic advantage may diminish again.

It won't happen right away.

And kojak71, I'd suggest a high efficiency ATX12V 2.0 >400W PSU on the recommended list for your system. The S12s & Enermax Noisetakers are obvious choices, with the S12 getting the nod. Also, you could try the Silverstone or Antec fnless ones -- with the caveats already noted all over the place here.

Green Shoes · Post by **Green Shoes** » Sat Apr 09, 2005 3:31 pm

kudos on the new noise ranking, Mike! I look forward to seeing those implemented (understandably it'll take a bit of time).

At last, a website that doesn't give everything a 4 out of 5

Jordan · Post by **Jordan** » Sat Apr 09, 2005 7:58 pm

kojak71, I would seriously consider a Zalman Resarator for a system that powerful. It would get most of the heat directly out of the case leaving the PSU to deal with only its waste heat and no extra heat from the CPU and graphics card.

Mike C, that last paragargh gets a bit confusong, well at least for me

kojak71 · Post by **kojak71** » Sun Apr 10, 2005 3:38 pm

Thanks to those patient enough to help me out, especially for the clarification MikeC. It goes to show that rankings should be used in conjunction with the reviews. I spend a lot of time pouring over the individual reviews, and pay particular attention to noise levels/signatures at different power outputs. Even if one is building a system that requires more power than 150W, the reviews do prove that there are still some quiet alternatives. Quite clearly the S12 is a class leader in this regard, as an 8db advantage over the Nexus shouldn't be sniffed at.

Thank goodness my other rig which is a low powered system and used only for internet and office applications, is virtually silent, all with the help of SPCR of course

kojak71 · Post by **kojak71** » Sun Apr 10, 2005 3:46 pm

Jordan wrote:kojak71, I would seriously consider a Zalman Resarator for a system that powerful. It would get most of the heat directly out of the case leaving the PSU to deal with only its waste heat and no extra heat from the CPU and graphics card.

I was just thinking of that the other day, and I might seriously consider it. Thanks for the reminder Jordan.

BTW, has any manufacturer entertained the idea of building a PSU that could be watercooled?

Post by **MikeC** » Wed Apr 13, 2005 2:28 am

As promised, the PSU numeric ranking system has been revised, and each and every PSU on the list has been assigned new values in the context of the new system.
http://www.silentpcreview.com/article28-page6.html

Green Shoes · Post by **Green Shoes** » Wed Apr 13, 2005 5:41 am

Nice job, Mike, looks like a lot of work went into that!

The amount and quality of noise the PSU makes with a typical load in a noise-optimized PC. Ranked from 1-10, 10 being completely noiseless, 9 being effectively inaudible, 5 being very quiet (~25 dBA/1m with a benign acoustic signature), and 1 being borderline quiet (~30 dBA/1m). In this scale 1 is still a usable PSU for a noise-reduced PC and quieter than the average PSU. A number rank followed by "?" indicates we have not fully verified the assessment. Any audible coil buzzing is noted in the comments.

I think this ranking system is much more accurate for this site's purposes. One very small nit: is it possible to make this paragraph slightly more obvious to people browsing through? I realize that they should read it anyway, but it's amongst 4-5 paragraphs of text and I think most people's eyes glaze over when confronted by that much reading. Can you put in in a colored box or something?

kojak71 · Post by **kojak71** » Wed Apr 13, 2005 6:12 am

Brilliant!

Took your advice MikeC and bought an Antec Phantom 350, fingers crossed that I've got a good'un!

anthonysimilion · Post by **anthonysimilion** » Wed Apr 13, 2005 6:53 am

Wow - after seeing the revised numbers, I'm removing Zalman PSUs off my list now!