Originally posted by: SonicIce
Originally posted by: 88NovaTwincam
I think you have it backwords! Sleeve bearings are not as noisy over time compared to ball bearings..
are you sure? I thought ball-bearings had less friction.
IF you were comparing two fans virtually identical (in RPM, blade design, mounting or free-air, motor, magnet, balancing, etc, etc, etc) then the sleeve bearing fan is subjectively quieter when new, partially because the ball bearings make a higher pitched noise that doesn't blend in with surroundings as well and that the human ear is fairly sensitive to, directionally.
This is also considering a certain minimal RPM and above, as the lowest RPMs used by many for very quiet systems will make the difference between sleeve or ball bearing indiscriminable. The higher the RPM, the more noticable the bearing noise.
Once a sleeve bearing fan starts to wear, it inevitably wears the bearing in a somewhat elliptical shape and slaps around, progressively wearing out the bearings at an accelerated pace. Since sleeve bearings tend to have lower lifespan (except the most high end bearings in precision made and balanced fans), they will eventually be louder than their ball bearing counterpart- if you're lucky. If you're unlucky, they will instead just fail to spin up from a cold start and some part of the system bakes instead.
All else is seldom equal as mentioned above. Ball bearings themselves are more expensive than sleeve bearings and are typically used in higher quality fans, with better blade molding, better balance, smoother motor operation. These factors can easily offset the bearing type for noise purposes, unless you have a particularly high quality sleeve bearing fan such as Papst or Panaflo, or get lucky and your low quality fan is (randomly) well balanced and you relube or replace it.
So in summary, it's not just a matter of bearing type and most people who seek these low RPM Yate Loons are wanting low noise, a noise level which requires low enough RPM that either type of bearing would be similar enough in noise level and frequency- until the fan starts failing. You have to use a fan speed reduction method with most fans, and these Yate Loons too as they are not silent at default speed, 12V operation.
They do start out closer to that ideal and due to their low torque, are pretty easily put into an even lower RPM by pulling air though a case, but it's all a matter of how quiet you need the system and how you want to reduce that RPM- just about any fan will be quiet enough given a good RPM reduciton method, except for a few thicker models with very powerful magnets, high torque types tend to start making pulsating or clicking noises.
One example of such a fan that doesn't respond so well to greatly reduced voltage, or even current limiting, is a
Sunon 120 x 38mm, though otherwise it is a good quality fan, certainly a lot better than these Yate Loons if airflow and life are more important than low RPM, low noise operation.
Otherwise, you can randomly grab any medium to better quality 120x25mm fan and expect to be able to run it as quiet as a Yate Loon, with a current limiting control method, and expect longer life too.