Antec Sonata Case & PSU

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IN ACTUAL USE: NOISE

The Sonata case was placed on top of a heavy steel desk which can resonate if there is enough vibration in a PC system. This quality was used to check the level of vibration emanating from the Sonata. For the most part, a dampening pad was placed under the case to eliminate interactive noise effects -- they are too dependent on specifics.

Subjective comparative listening was done against the recently reviewed ARM Systems Stealth system as well as a self-built P4 system (quietest of all, with three 5V Panaflos and 2 elastic-suspended Seagate Barracuda IV single platter drives). Both use cases that are relatively modest in price but solid. The home-built machine is in a Landmark ATX-298U with grills cut away and some internal damping applied. The single-fan PSU has been modded with a Panaflo 80L fan swap.

Noise With Test Load

The first test was to simply power up the PSU on a test load, close the case covers and listen. The noise level was too low for any serious measurements with the old Heath SLM, and there was no opportunity to access the UBC anechoic chamber at this time.

1. PSU only: Up to ~100W power output, the Sonata + can be considered very quiet. There is no extraneous noise caused by air turbulence effects anywhere around the front bezel. The PSU fan is spinning too slowly for this to be a problem. A very small amount of noise escapes the small holes that form the name Antec across the sides, confirmed by blocking, then unblocking the holes. I would venture to say the difference is likely no more than 1-2 dBA. Most of the PSU fan noise is slightly turbulent midrange airflow, with a small amount of bearing noise -- audible only if you get really close in a quiet room. There is too little vibration transmitted into the steel desk to cause any audible resonances.

2. PSU + 120mm fan: With the 120mm fan plugged into the fan-only voltage feed from the PSU, up to ~100W, the noise level is increased by about 1-2 dBA from one meter away. It is a smooth broadband noise similar to pink noise, where output drops with increasing frequency. There is little or no high frequency content in the noise of the 120mm fan, even at 12V.

Noise with Simplest Low Heat System Setup

The next tests involved the installation of a low-heat system.

Intel P4-1.8A Rated at ~50W max
Thermalright AX478 HS Very good P4 HS
Panaflo FBA08A12L1A 80mm fan SPCR's standard low noise fan, plugged into fan-only PSU output
AOpen AX4GE Max motherboard Includes built-in VGA, LAN, and unique SilentBIOS & SilentTEK fan/thermal control features
256 MB DDR RAM Samsung 2100
Seagate Barracuda IV 40G Single-platter, 12.8W max
Hitachi 16X DVD ROM Detailed specs unknown
Included 120mm Antec fan On back panel

Given the component count, you might predict that there is hardly any difference in noise between this system and the dummy test load. You would be right.

The system draws 92-95W AC during long term 100% CPU utilization with 3 different software utilities. Given the ~65% efficiency of the True 380S at lower loads, this translates to 62W of delivered DC power. Yes, a few turn-on peaks of 120-130W were observed, but these were fleeting, mere bursts. A real VGA card, a couple of PCI cards, another strip or two of RAM and another hard drive -- all these could add another 40-50W to the toal power load, but it would still be no more than about 100-110W long term maximum draw. The point is that the PSU fan speed would remain close to the default of 5V and thus remain very quiet.

3. PSU + Panaflo plugged into fan-only PSU output + HDD snugly screwed with grommets: There is a small increase in broadband noise from the Panaflo fan and the Barracuda IV hard drive. At one meter, the Heath SLM may have registered a 2 dBA difference; it is difficult to judge. Judging by ear, I believe it is no more than 2 dBA. The PSU fan remains most audible.

Seek / write of the hard drive could be heard quietly but plainly above the residual system noise, despite the rubber grommets. The HDD screws were just barely tightened to minimize mechanical coupling. Again, the difference is below the resolution of the Heath (and most affordable SLMs), but the seek noise is slightly more audible than with the EAR grommets in the ARM Stealth system. This noise sounds like soft thrumming. Placing the PC directly on the desk causes some amplification of the noise by the desk. Unless you are seeking silence, it is not objectionable or serious. Up to 3-4 dBA difference can be measured against direct HDD mounting without grommets; the subjective difference is much bigger than the measured 3-4 dBA. I personally do not put up with the noise of direct mounting of any HDD to any case.

4. PSU + Panaflo plugged into fan-only PSU output + HDD placed on grommets: The screws were removed, and the drive placed on top of the grommets, making sure the sides did not touch the mounting frame. The noise difference of this little adjustment is very difficult to measure but so easy to hear: The soft thrumming drive seek noise simply disappears. OK, maybe it does not completely disappear, but it drops enough that even with the PC directly in front of the keyboard I am working on, the seek noise is not audible. I have to get well under one foot or less to hear the noise. The PSU fan becomes the loudest noise again.

5. PSU + Panaflo and 120mm fans plugged into fan-only PSU output + HDD placed on grommets: As in scenario #2, the noise level is increased by about 1-2 dBA from one meter away. The 120mm fan is a smooth, broad increase in sound, not really objectionable or very significant. Some low frequency noise accentuation may occur of the system is placed on a resonant structure.

Noise Performance Summary

The Sonata combinations is a bit noisier than the ARM System Stealth. My guesstimate of anechoic chamber readings for the Sonata system, based on the 22-23 dBA @ 1 meter for the ARM Stealth, is about 26-28 dBA @ 1 meter.

The primary limitation is the fan in the Antec True 380S PSU. In free air, with both fans at the Antec's 5V default voltage, it is louder than the Panaflo 80L, the fan in the PSU of the ARM Stealth and my own home-assembled PC. With the added accentuation of lower frequency noise in the PSU due to acoustic impedance effects, the Antec PSU is the loudest component. Keep in mind, however, that the Antec's ability to keep itself cool at high power load is definitely superior, as its fan is rated for almost 40 CFM airflow at 12V, compared to the Panaflo's 24 CFM.

The noise of the 120mm fan off the PSU fan-only output is unobtrusive. It does add noise, mostly a kind of lower frequency hum, but the quality is such that it hardly seems to, especially with the masking effect of the slightly noisier PSU fan. Given its proximity to the CPU, it would be a simple matter to rig up a duct from the 120mm to the heatsink, and eliminate the fan on a top-ranked HS. Unless you are overclocking and overvolting a very high power CPU, this is probably a perfectly viable cooling solution.

No part of the bezel opening could be identified as a source of noise; almost all the noise came from the back of the case where the fans are. The drive seek noise could not really be isolated to its source. It seems to emanate from the entire case. Softer, larger grommets -- perhaps in combination with soft plastic screws -- would help improve the effectiveness of the HDD noise reduction.

The holes that form the word Antec allow a small amount of noise to emerge. That noise is relatively modest but tends to be somewhat higher in pitch, perhaps because of the proximity to the PSU, which emits some very low level buzzing. Blocking the holes from the inside is a simple way of reducing the noise if so desired.

COOLING PERFORMANCE

Three points were monitored for temperature during CPU stress testing:

  1. CPU diode with Motherboard Monitor (MBM5)
  2. PSU fan exhaust (with thermal probe and DigiDoc2 from online retailer SVC as shown below)
  3. HDD with Dtemp software

DigiDoc monitoring PSU exhaust; HDD mounted low in drive bay to take advantage of convection.

The PSU exhaust monitor was simply to ascertain whether the 120mm fan lowers case temperature enough to make a difference in the PSU temperature. The unusual external 4-pin DC power output on the Antec PSU came in very handy here, as you can see in the photo above.

120mm fan
OFF
ON
CPU Stress
idle
max
idle
max
CPU temp
29C
59C
28C
56C
PSU exhaust
30C
39C
30C
33C
HDD
35C
38C
34C
34C

FAN voltages (for both Panaflo on HS and 120mm fan) remained at 5V throughout testing, as the PSU never got hot enough to push the fan any higher. Ambient room temperature was at 20C throughout.

The results are clear:

  • The P4-1.8A stays cool enough with the Thermalright AX478 / Panaflo at 5V, with or without the 120mm fan at 5V, although the big fan does drop the max temps a bit.
  • PSU exhaust air temp drops by a significant 6C with the 120mm fan on, so if your system runs hotter than this one and pushes the PSU fan voltage up, the big fan will help it run cooler and quieter.
  • The HDD temp stays perfectly safe with or without the 120mm fan. Anything below 40C is just coasting. The HDD location just behind the front bezel vents always ensures at least a small amount of airflow, enough in this system to keep it cool.

The holes on the sides that form the word Antec appear to have some cooling effect. Blocking them with duct tape raised all temps by a few degrees.

CONCLUSIONS

In the SPCR forums and elsewhere, I have often repeated the line that how quiet a case is not that important, it's how cool a case will let components run that's more interesting. The concept is simple: if the components can be run quietly enough and still be cooled effectively, then there is so little noise that the ability of a case to damp noise is irrelevant. Of course, this is probably only true if you don't run cutting-edge, burning-hot components.

The Antec Sonata incorporates no damping at all, so if it is being marketed as a quiet case, it is on the basis of its ability to run components coolly, and therefore, quietly. Like all cases, by simply enclosing the components, the Sonata provides a degree of noise reduction.

For those seeking simplicity in a quiet home-built PC, the Sonata is a good choice. Buy a Sonata case / power supply. Pick out the Barracuda IV or V drive(s) of your choice, CPU, motherboard, VGA, RAM, optical disks, etc -- and any top ranked HS from our recommended list with a Panaflo 80mm L fan. Assemble everything and run both the Panaflo and 120mm from the fan-only output of the PSU. Make sure the CPU HS fan protection switch in the BIOS is turned off. Power up. Voila: you now have a quiet computer.

  • the convoluted sound path through the front air intake vent,
  • the noise-reduced, single-fan PSU (Antec's quietest, as far as I know),
  • the PSUs reduced-voltage fan output,
  • the quiet high-airflow 120mm case fan,
  • HDD mounting grommets
  • and the unique (and cool) HDD mounting setup

... these are the many features that allow a quiet system to be built around the Sonata with little effort. Given the modest size of the Sonata, it may not be for power-crazed gamers. In the hands of an imaginative or experienced silent PC devotee, it could easily be made extremely quiet. The HDD mounting system alone is worth the purchase price if you are a hardware hacker like me. Oh, let's not forget -- that black piano finish looks pretty slick, and it is a handsome unit.

The Sonata is Antec's first foray into quiet computing. As such it is a very respectable effort. Recommended.

Much thanks to Antec for the review sample and their kind support.

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