Hello

I'm just wondering hows the noise level of the Seasonic S12II 520 Bronze. When you compare it to the old S12+ or the Corsair 450VX.

I got a Seasonic M12 II Bronze M520 a couple of months ago and I'm very happy with it. As far as I can tell from the reviews, it's identical otherwise to the non-modular version.
The VX 450 is in my circumstances at least, certainly a lot louder than the S12; I know that from personal experience because I put one in the computer I built earlier in the year for my daughter. However, it's not a like for like comparison; hers is drawing more power because there is a 5750 graphics card in there as opposed to mine which is using integrated graphics - cpu's are the same in both. The psu in my case (FT 01) draws cold air from outside the case where as her case is the more traditional type with top mounted psu taking air from within the case. I reckon I'm using 200W max so the Seasonic is not actually working hard.
Basically, I never hear the psu fan - the only real noise, (not a lot) comes from the 3 suspended hard drives; the case fans in both cases are running pretty slowly and are virtually inaudible unless they ramp up.

Not a scientific comparison I know but I much prefer the Seasonic - It feels better quality too.

One of the best group regulated psus made out there. Definitely a budget psu, but top of the line budget. I'd say a recommend for almost all builds except I don't know the actual noise levels.

I think the "II" Bronze series are the same (or nearly) as Antec Neo Eco, both have the same Adda fan as usual but it idles at ~600rpm.

Im not sure how that would stack up vs the Enermax Modu/Pro 82+ which have a specialised fan that idles around 400-500 rpm if I remember.

Good value PSUs but Im also wanting something quieter than my Antec Neo 550w (rev:5), which is a pretty quiet PSU.

Enermax Modu/Pro 82+ is also almost double the price making the Corsair CMPSU-650TX better choice. I wouldn't compare a Seasonic unit to a Antec that's now made by Delta or FSP. There is just no contest in the quality and noise level, Seasonic hands down.

Have a read of the review I posted in the Antec Neo Eco thread, they are the same PSU even down to the fan profile

Also the Corsair TX650w is the loudest of all mentioned, theres quite a few quieter since then without being overpriced.

Your perception of the two supplies is more about the cases they are in then the supplies themselves. Both the fans and the circuit boards are almost identical. Johnny Guru even states that the vx450w may be a S12II power supply with better capacitors. My NZXT Whisper has a separate air path for the PSU (and hard drives).

The VX450w powers an overclocked Intel Quad-core, an AMD Radeon HD 5770, eight 5400 RPM hard drives (quiet due to rubber and foam), two optical drives, and a SSD. At normal loads (100-200 watts) the fan does not speed up past the 600 rpm it starts at, so the VX450 is not at all noticeable.

(While gaming the PSU does spin up its fan, as power draw rises to about 300 watts.)

The Johnny Guru review of the vx450w dates from July 2007 and does, as you point out, refer to a Seasonic S12 II. However he also reviewed the Seasonic S12 II Bronze 520W in April 2010... not the same psu I suspect, as he would be unlikely to review a 3 year old component. The bronze version is perhaps an updated and improved version of the older "non-bronze" version. it also scores slightly higher marks than the vx450w.