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- Update Nov 16, 2007 - Many additions and deletions to recommendations.
- Update Oct 17, 2007 - Antec P182 added.
- Update Aug 17, 2006 - Many additions to recommendations,
plus new section on Acoustics around the media PC.
- Update Jan 3, 2006 - Antec P150 recommendation put on hold
until bundled NeoHE PSU issues are fully resolved.
- Update Nov 9, 2005 - Additions, deletions and changes all
around.
- Update May 7, 2005 - A few changes to the lists.
- Update Jan 23, 2005 - Text revised, new Antec, Coolermaster
and SilverStone cases added.
- Update Aug 3, 2004 - YY Mars and SilverStone SST-LC01 cases
added.
- Update May 31, 2004 - A huge number of changes and additions.
- First published March 12, 2003
Cases don't make noise by themselves. Some people argue that a PC begins with the case. Others say it's merely the outer skin in which a PC is enclosed. Our point of view is that there's no doubt that a case has a very significant role to play in silent computing.
What's in a case? Components, heat, and noise.
Much of the discussion here refers to a tower-style ATX case. There are many other case styles, including very small towers, tall towers, horizontal desktops, both large and small, silm desktops, and the "lunch box" size / shape popularized by Shuttle and Mini-ITX case builders. Fundamental points about cooling and airflow apply to all case types. Just keep in mind that the low-front-to-high-back airflow path considered ideal for ATX towers will not apply the same way for horizontally laid out cases.
THE ROLE OF A CASE
The conventional perspective says that a case performs these functions:
- Adheres to various form factors in order to hold and house the various components that make up a PC: PSU, motherboard, PCI cards, drives, fans, etc.
- Provides EMI and noise shielding.
- Allows for airflow through the case for cooling of the components within.
- Looks nice.
The silent PC perspective is different, mainly in emphasis. Form factor adherence is assumed (and mandatory) for all cases; EMI shielding and looks are secondary to the key properties of:
- Extremely unrestricted airflow vents,
- Indirect paths for noise escaping the case,
- Well-directed airflow paths within the case,
- Low resonance, sturdy construction and low sound transmission.
Here is a little beauty, but it is not just a case... it's a customized fanless mini-ITX PC.
1. Unrestricted Airflow Vents
There are several reasons why unrestricted aiflow vents are so important for silent computing:
- A main strategy is the use of quiet fans at reduced speed to eliminate fan noise. Because airflow volume and pressure is considerably lower than in a standard PC, any obstruction at the vents has a potentially large negative effect in temperatures.
- Case fans are normally mounted at the airflow vents. Anyone who has paid attention to the behavior of fans knows that a physical obstruction (impedance, in the fan jargon) close to the fan blades cause turbulence noise. The greater the obstruction, the greater the noise and the lower the airflow.
The ideal vent is one with no grill at all, but in the face of realities such as curious toddlers or pets, something like a minimal wire grill is about the best compromise. In the front of the case, it is normal for a plastic or metal bezel to be used for a cosmetically pleasing apparance. The front intake air vent can be seriously hampered by the design of the bezel. Very few case makers pay enough attention to the bezel vent design.
Antec P180 broke new ground in many ways, including independent thermal zones for improved cooling of all components.
2. Indirect Escape Paths for Noise
The above points might suggest that the best silent case is one with a completely open hole in the front for an intake fan. But that's not true, because this allows the noise of the fan to go directly out of the case, to the users' ears. The requirement of indirect noise escape paths means that the front bezel should act as a baffle that forces sound to travel around angles so that it loses intensity before exiting the case, while at the same time, allowing the air to flow unrestricted. A similar arrangement for back panel vents would also be useful, but no known case has this feature. The noise from the back panel, which usually points away from the user, is also less critical than the noise from the front.
3. Well-directed Airflow Path in the Case
This is best achieved by minimizing the number of extraneous holes in the case. Randomly placed holes on the sides of cheap cases, for example, tend to disrupt the ideal flow of air, which is generally seen as from front bottom to the back top.
4. High Resistance to Vibration, Sturdy Construction and Good Sound Insulation
The requirement of high resistance to vibration and good sound insulation calls for heavier, thicker panels joined solidly. Noise caused by panels vibrating in sympathy with fans and hard drives is much more insidious and prevalent than most people would believe. This phenomenon adds a haze of background hum, mostly in the lower frequencies but not limited to them. In general, this requirement tends to exclude aluminum cases, which are usually made of thinner, stiffer sheet metal that resonate and vibrate more readily than steel cases. (More about vibration and aluminum cases on the next page. )
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