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Mediasonic ProBox 4-Bay 3.5″ Hard Drive Enclosure

The Mediasonic ProBox HF2-SU3S2 is a simple and affordable 4-bay USB 3.0/eSATA enclosure with fan control and nifty power syncing features.

February 26, 2014 by Lawrence Lee

Mediasonic ProBox HF2-SU3S2
4 Bay Hard Drive Enclosure
Street Price

Mediasonic is a small Canadian outfit specializing in storage devices and accessories. They’re primarily known for their multi-bay enclosures that allow consumers to augment their PC with extra storage in external form. Today we’re going to take a look at one of their more popular products, the ProBox HF2-SU3S2, a 4-bay enclosure with both USB 3.0 and eSATA interfaces, active cooling with fan control, and syncing features that allow it to power on/off with the system it’s connected to.

The ProBox moniker is applied liberally to a variety of Mediasonic’s wares including the HFD1-SU3S2 4-bay dock, and the monstrous H82-SU3S2 8-bay enclosure. The ProBox HF2-SU3S2 is only a 4-bay device but being a simple enclosure, it lacks the physical girth of NAS systems and full-fledged servers, as well as the attention from the media. The ProBox is a humble device by comparison, lacking an operating system, network connectivity, or even RAID functions (check out the ProRaid series if RAID capability is required). It is just a USB/eSATA connected local storage extension.

The Mediasonic ProBox HF2-SU3S2.

The ProBox is quite compact, only 16.6 cm tall, equivalent to about seven stacked desktop hard drives. A small grill under the bezel allows air to pass through the drives to an 80 mm fan at the back. The fan can be run on automatic, tied to a thermal sensor inside, or set to one of three speeds, via a front panel control. Other controls allow you to switch the interface between USB 3.0 and eSATA, and change the sync mode that dictates whether it will shut down, go to sleep, or remain active if the PC it is connected to powers down. The sleep function also wakes up the drives if the system turns back on. It’s a simple device but it’s anything but dumb.

The box.

Package contents.

The ProBox HF2-SU3S2 ships in a dark cardboard box with a convenient plastic carrying handle. Included in the package is the enclosure well protected with foam padding, a brief instruction sheet, USB 3.0 and eSATA cables, the power adapter and cable, and four handles with screws.

Specifications: Mediasonic ProBox HF2-SU3S2
(from the
product web page
Hard Drive Support All brand of 3.5″ SATA I / II / III hard disk drive up to 4TB per drive, and up to 4 x 4TB
Interface USB 3.0 (up to 5.0 Gbps)
eSATA (up to 3.0 Gbps)
Smart Fan function Thermal-Sensor built-in
Auto & Manual mode
3 level of speed
Additional Features Power Sync: Power off in synchronization with PC
One button interface selection: Switch USB 3.0 or eSATA interface by pressing one button
Supporting OS Windows XP / VISTA / Windows 7 / Windows 8 (with MBR enabled, supports total capacity up to 2TB)
Windows Vista / 7 / 8 32/64 bit (with GPT enabled, supports total capacity more than 2TB)
Mac OS 10.3 or later
Power Adapter 100V to 240V
Package Contents HF2-SU3S2 Enclosure
eSATA Cable
USB 3.0 Cable
Power adapter (Universal)
Power cord (US Type)
User manual
Screw driver
Hard Drive Handle
Dimension 215(D) x 126(w) x 166(H) mm
Weight 1.8KG (excluding hard drive)
Safety Specification CE / FCC / ROHS
Product Origin Taiwan
Important Note: When connecting via eSATA interface, customer’s computer hardware needs to have Port Multiplier w/ FIS-based switching in order to access multiple HDDs simultaneously.


The ProBox HF2-SU3S2 weighs 1.8 kg or 4 lb and measures 21.5 x 12.6 x 16.6 cm or 8.5 x 15.9 x 6.5 inches (D x W x H), giving it a total volume of 4.5 liters. The enclosure is sturdily built with molded black plastic but the door has a thin aluminum faceplate to give it bit of shine and pizzazz.

Cooling is provided by an 80 mm fan at the back. The eSATA and USB 3.0 connectors are also found at the rear, while the power jack is off on the side.

The enclosure sits on four small plastic rings which allows it some mobility though the weight of the chassis plus the drives inside is more than enough to keep it from being moved accidentally.

Powering the device is an external 60W adapter (12V/5A).

The external cover is attached loosely with a simple open hinge system. Once that’s removed, a metal grate secured with two spring-loaded barbs ensure the hard drives stay tucked in place.

Broad metal guides align the drives with their respective connectors on the controller board at the back. The PCB takes almost all the available space with only a couple of small holes for the fan to pull air through.

Plastic handles are used to slide the drives in. There isn’t much feedback to tell you if the drive has made contact with the SATA connector so just push it in as far as it will go.

LEDs at the front denote hard drive activity as well as the interface currently being used, the sync mode, and fan speed setting. To prevent accidental presses, turning the enclosure off and changing the sync/interface setting requires a long press of three seconds. It’s also possible to connect the ProBox to two different systems, one through eSATA, the other through USB 3.0. Only one PC will be able to access it at a time but you can switch back and forth, handy if you want to routinely back up two PCs, or transfer data between machines that aren’t otherwise networked through a wired connection.


USB 3.0-Connected System Configuration:

Test Hard Drives:

Measurement and Analysis Tools


Most of the noise from the ProBox is caused by its cooling system, an 80 mm rear exhaust fan, rather than the Seagate NAS HDD 4TB‘s we used for testing. The fan runs fast, probably to compensate for all the airflow blocked by the controller board inside. There are three manual settings (low, medium, and high) as well as an automatic option, though during our testing, the drives never got hot enough to cause it to spin past the low setting.

Baseline Noise Level (dBA@1m)
Fan Speed Setting (drive config)
SPL @1m
Disabled (filled)
20~21 dBA
Low (empty)
27 dBA
Low (filled)
28~29 dBA
Med (empty)
34 dBA
High (empty)
41~42 dBA
Measuring mic positioned 1m at diagonal angle left/front
of case.

The drives on their own inside the enclosure generated a SPL of 20~21 dBA@1m (the fan cannot be turned off — we manually disabled it by jamming it) with a limited level of vibration passed onto the rest of the enclosure. The drives are braced fairly well by the metal grate inside and the external door, though loose, thankfully didn’t rattle. The NAS HDD’s are relatively quiet models and there’s nothing in the enclosure’s design to make them sound worse.

At low speed, the fan had a soft, smooth sound except for some broad clicking noises audible close up. It’s not the best sounding fan in the world but it certainly helps being buried at the back of the enclosure behind hard drives. It’s moderately loud, producing 27 dBA@1m, so it would easily drown out a typical modern four hard drive configuration. The fan gets noticeably louder at medium and high, with the tone increasing with its speed, though the clicking becomes less noticeable.

Compared to the drives alone, the fan outputs considerably more noise in the 150~800 Hz range.

Power Consumption & Thermals

Enclosure Measurements (Idle)
Enclosure State
Idle (empty)
Idle (filled)
HD #1 Temp
HD #2 Temp
HD #3 Temp
HD #4 Temp
System Power (AC)
10~11 dBA
27 dBA
28~29 dBA
Fan speed: auto (low).
Ambient temperature: 20°C.

When turned without any drives, the ProBox pulled only 5W from the wall. The AC power draw increased by 5W for each drive we installed. This indicates the power adapter is fairly efficient as we previously pegged the power consumption of the Seagate NAS HDD 4TB at 4.8W idle. After sitting for half an hour (more than enough for HDD temperatures to stabilize), the drives were running at a cool 30~33°C. Even though the fan is mostly blocked off, it nevertheless managed to do its job.

The ProBox has two sync modes that can be used to either turn the enclosure off or put it into sleep about 15 seconds after the PC it’s connected to is shut down. The sleep function also wakes the drives up when the PC turns back on but we were only able to get this to work with eSATA, not USB 3.0. With USB, it shut down with the system just fine, but when put to sleep, it stayed asleep, requiring power cycling to get the drives back online.


To gauge the overall performance of the ProBox we used a synthetic benchmark, CrystalDiskMark, which tests both sequential and random performance with two different block sizes. We also performed some timed file copy tests (the same used in our hard drive test methodology), a small file test consisting of a variety of small HTML, JPEG, MP3, ZIP, and EXE files, and a large file test consisting of four AVI files, 2 x 700MB and 2 x 1400MB in size.

The copy tests were conducted between two of our Seagate NAS HDD 4TB’s placed in three different configurations:

  • both as internal drives, connected to our test PC using a SATA 6 Gbps interface
  • one internal and one external in the ProBox connected to the PC using USB 3.0
  • both external in the ProBox

CrystalDiskMark paints a flattering picture, indicating the ProBox USB 3.0 and internal SATA 6 Gbps interface to be very close in performance. For large block sequential transfers, the same drive actually benchmarked better inside the ProBox.

Our file copy tests tell a different story. With our reference point being the completely internal PC to PC result via SATA 6 Gbps, it’s clear that parity is only attained when the ProBox is reading. It was slower when being written to, particularly with small sets of data. The small file copy test result took 35% longer writing compared to reading. Transferring data between two drives within the ProBox itself was slower still, this time with a dramatic reduction in large file transfer performance.

When used as a repository for large files, it seems that a mechanical hard drive mounted in ProBox offers virtually the same level of performance as it would deliver connected internally. Small files take longer to copy over but once it’s on there, retrieval isn’t affected by any deficiencies with the USB 3.0 interface.


These recordings were made with a high resolution, lab quality, digital recording
system inside SPCR’s own 11 dBA ambient anechoic chamber, then converted to
LAME 128kbps encoded MP3s. We’ve listened long and hard to ensure there is no
audible degradation from the original WAV files to these MP3s. They represent
a quick snapshot of what we heard during the review.

Each recording starts with ambient noise, then 5~10 second segments of product
at various states. For the most realistic results,
set the volume so that the starting ambient level is just barely audible, then
don’t change the volume setting again while comparing all the sound files.


The Mediasonic ProBox HF2-SU3S2 is a simple product that gives users a sizable backup or storage expansion solution. It’s not network-capable and lacks redundancy options but at this price-point we certainly can’t complain. Despite its rather generic nature, it has a couple of surprising extra features you wouldn’t expect to see in such a rudimentary device. The ability to turn off with the PC it’s connected to and the sleep/wake function are incredibly convenient, though wake only works properly with eSATA. The fan control modes are a nice bonus but are ultimately unnecessary — the low setting alone provides more than enough cooling.

The fan doesn’t sound too bad in relation to four mechanical hard drives revved up inside, but it’s fairly loud, to the point that it can become distracting if left on for more than a short period of time. It’s something you would put on the floor under the desk rather on top next to your monitor. Not only does the fan spin faster than necessary, the cooling design is flawed in that the circuit board is positioned directly in front of the fan, blocking off much of the airflow. This seems to be the convention for these types of enclosures but a larger fan attached to the side or blowing up from the floor would be preferable. Its only other notable issue is poor write performance with small files but if you’re mostly going to be storing large files you can expect full speed.

We can’t deny the value proposition Mediasonic is offering. The ProBox HF2-SU3S2 is selling for approximately US$100, making it one of the more affordable 4-bay enclosures on the market. That alone would put in contention but with the extra features, and you have a compelling product.

Our thanks to Mediasonic
for the ProBox HF2-SU3S2 case sample.

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Mediasonic ProBox HF2-SU3S2
is Recommended by SPCR

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this article in the SPCR Forums.

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