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[Jack]

I have been using the new FiiO S5 for the past two months for background music at the office. The FiiO S5 is a fairly unique product in terms of features and form factor. It overlaps across some different product types and doesn’t fit neatly into any of them.  Therefore I had some difficulty categorizing the S5 - just what kind of a product is it?

The S5 is available in both a deep wine red or pearl white. Its form factor resembles a very fat iPhone 3G, or a half a jellybean, depending on the color. The wine red color finish is an automotive paint process, with a deep metallic luster, but the glossy finish shows more finger prints and smudges.  The white pearl color is also metallic in look, but with a matte texture, giving an overall luxurious "glowing" appearance.  Even those who make it a point to stay away from white color gadgets may make an exception for the pearl white S5.

The FiiO S5 contains a simple MP3 player that supports a wide range of formats including MP3, WMA, OGG, and lossless formats like FLAC and APE. With 2GB of non-expandable internal storage, it can hold a decent amount of music – about 500 songs at an average of 4MB each.  Getting songs onto the S5 is very simple as it mounts as a normal USB storage device when connected to a computer.  No special software is provided with the S5, so users can use normal file copy operations to put music on the S5.  A variety of shuffle and repeat playback settings are available through the control menu, but as with most simple MP3 players, there is no play list support.

It has a beautiful OLED screen with a 128x64 resolution; the display is exceptionally sharp and easy to read. In addition to displaying normal song information such as title and artist, the FiiO S5 also supports .LRC files for lyrics. A total of 19 different languages are supported by the FiiO S5 – though it seems that cross-language compatibility is not available, so Japanese song information will no display if the language is set to English.  In all, the MP3 player aspect of the S5 works well and offers enough features to be useful.

Another source for music on the FiiO S5 is the built-in FM radio, which covers two separate bands of 76-90MHz and 87-108MHz. The 76-90MHz band is currently used only by radio stations in Japan, but the FCC is investigating adding the 76-88MHz band to the US FM radio broadcast band, so if that happens, the FiiO S5 could prove to be quite useful.  The FiiO S5 supports manual and auto programming of station presets.  Though there is an internal antenna built in the FiiO S5, as verified by taking it apart, the reception was improved dramatically when a USB cable was attached to the S5, regardless of whether the USB cable is attached to anything on the other end.

For those remain unsatisfied with the built-in MP3 player or FM radio, an AUX-in jack is available on the back of the S5. Anything with a headphone jack or line output can be used to supply music to the S5, such as iPods, MP3 players, and computers.

Without a headphone jack, the only outlet for the S5’s musical talents is the built-in stereo speakers.  Luckily, FiiO knows how to make low power amplified speakers very well and the S5 reaffirms that position.  The S5 for this review came loaded with a demo Chinese song consisted primarily of female vocals and some string instruments. It was in the lossless APE format and was hauntingly beautiful to listen to on the S5.  The midrange and highs on the S5 is exceptionally smooth and detailed, without any hint of strain or harshness.  It was a truly indulging listening experience and a shock to hear such beautifully reproduced music from this tiny speaker.  As can be expected, bass was on the lean side though the little speaker does make a valient effort. Bass heavy types of music will miss quite a bit of the oomph and impact. For most music types this is not an issue, especially with the high quality mid and high frequency output of the S5.

Other notable features and functions of the FiiO S5 include a very flexible alarm, where you can set the alarm time and frequency, as well as choose the alarm sound source.  Available alarm sound sources include a limited number of embedded files, user stored music files, or the FM radio.  The S5 has a "sleep" and "delayed turn on" feature where it will automatically turn on or off after a set amount of time.  These features make the S5 a very practical gadget for travelers as a clock radio.

The S5 comes with a circular peg stand - it's a very simple but effective design.  When not in use, the stand dangles on the lanyard.  Flanking the stand peg hole is a USB charge/data connector and a standard 3.5mm stereo mini plug.  On the top are two wiper switches that control all aspects of the S5's operation. It's a very ergonomic design as the index fingers naturally fall on the wiper switches when holding the S5. The only gripe in terms of usability is that the S5's menu system and reaction to user input feels kind of sluggish.  Most of it appears to be due to built-in delays, such as holding a button for 2-3 seconds to access the secondary action where 1 second would have been plenty.  Other delays such as switching tracks and changing radio stations could be due to lag in the software.

After two weeks of use, I came away from the S5 feeling that it should prove to be a very useful and enjoyable music player for those that want a portable mini audio system that can provide high quality background music anywhere anytime. Travelers can use it as both a clock radio and as impressive notebook speakers for giving presentations.  I still don't know if the S5 can be fit into any one category, a "mini boom box" is about as close as I got to a description that I think others can relate with.  What is certain is that the S5 offers a healthy dose of audio goodness in a very small and portable package.

[Jack]

Coming away from the review of the FiiO S5 thoroughly impressed at the quality of output that the engineers were able to produce from such a small device, I decided to take a closer look at how it is made, and perhaps unlock some of the secrets it holds.

The S5 was relatively easy to take apart, with four small screws at the four corners holding the back shell cover in place.  Once removed, I was able to pry the rear cover off with a bit of effort.  The level of effort put in by the engineers in designing the S5's enclosure is impressive, as each driver is housed within its own separate chamber, with an elaborate systems of grooves to ensure adequate sealing.  Using separate chambers for each speaker not only makes the final performance much more predictable, it also minimizes channel cross talk for superior low frequency output and more realistic imaging.

Nestled between the two sound chambers is the main board as well as a vertical riser card.  The main board holds all of the main function circuitry while the riser card provides 3.5mm mini plug input and USB interface.  As with other FiiOs products, the circuit board looks to be of good quality and built with top notch components. The rechargeable lithium battery is securely held in place by a thick foam pad.  On the sell of the S5 is the FM antenna, with a thin wire leading to an attachment point on the main board.

The speaker drivers appear to be about 2mm in diameter each, built with paper cone and half-rolled surround, along with a stamped steel basket and neodymium magnet. The center “dust cap” is mounted directly on top of the voice coil former, instead of coupled to the cone, thus extending the range much further. Instead of mounting both drivers on the same plane as most small portable speakers, the speakers in the S5 are angled outward slightly to create a dispersion angle, resulting in a wider sound stage for a more dramatic stereo effect.

All this may sound nice in words and pictures but to carry the technical analysis one notch further, I made some in-room measurements of the S5.  For this measurement, the S5 was placed on an office desk situated in the middle of a 15 x 15 office.  The office is carpeted and is furnished with office equipment - all in all a good representation of the kind of environment that the S5 is expected to be used in.  The S5 is placed on the table without anything beneath or around it, propped up by the stand that it comes with.  The measurement is taken with a instrumentation condenser microphone that's been calibrated to provide flat measurement response from 10Hz to 20kHz. The microphone feeds into a microphone pre-amp with an USB interface to a PC running measurement software.

The microphone was placed at seated ear level and pointed at the S5 from 6 feet away. Measurement was done using a 100-22kHz sine wave sweep generated by the PC and played back through the S5's 3.5mm input, with the S5 powered by its own internal battery.  In addition to the frequency response sweep, I also made harmonic distortion measurements at fundamental frequencies of 400Hz and 1kHz.

In the graph above, the blue trace is the frequency response.  When reading frequency response charts, it's usually about the smoothness rather than absolute flatness. If a audio device is engineered to accentuate a certain frequency band as the desired voicing characteristic, then we should look for a smooth transition to and from the accentuated band. The human ear does not like sudden peaks and valleys in the frequency response, but finds gradual changes in emphasis quite pleasing.  This is why there are "bass" "treble" type tone controls, and why the most desirable equalizers are the parametric type with only a few bands.  This said, the smoothness of the S5's frequency response is rather impressive. The bump in the 300-800Hz region is likely due to the ground plane enforcement effect of the desk; there's a slight rise in response going into the upper midrange centered on 4.5kHz and finally a very gradual roll off to the treble area. The smoothness of this response curve confirms the exceptional quality of the S5's mids and highs.

With respect to the bass response, we can reliably say that the roll off starts somewhere between 300 and 400Hz, but due to the ground plane reinforcement, the -6dB point is somewhere closer to 250Hz. The roll off follows a 24dB per octave slope, and given the sealed chamber design of the S5, indicates that there is likely a 12dB/octave high pass filter in the S5.  Without this filter, the S5 is likely to sound much muddier without an appreciable increase in bass output, and the overall output level would be lower at the onset of amplifier distortion.  Given that the room had a noise floor of about 30dB, the limit of the S5's audible bass output was right about 100Hz. It is worth mentioning that the S5's response curve maintained this smooth characteristic and high frequency extension within about a 60 degree angle. That is, the off-axis response of the S5 was exceptionally good. I suspect this is due to the drivers firing at an angle relative to each other rather than on the same plane.  It isn't until the angle becomes larger than 45 degrees to either side before the high end response starts to roll off appreciably.

A smooth frequency response is worth little without good accuracy, detail, and transparency. To find out the reason behind the S5's good performance in this regard, I ran a couple of total harmonic distortion plots at 400Hz (green) and 1kHz (purple). Harmonic distortion is especially detrimental to sound quality and clarity at lower frequencies because of its harmonic nature.  Higher frequencies may only have 1 or 2 harmonics within the human hearing range, and thus isn't as critical. Both measurements were taken with the S5 playing at approximately 86dB, plenty loud to fill the office with a good amount of sound. The following are the distortion figures:

Input RMS 85.8dB Distortion at 399.9Hz, -20.5dB FS Based on 8 harmonics THD 0.727% 2nd harmonic 0.320% 3rd harmonic 0.649% 4th harmonic 0.055% 5th harmonic 0.028% 6th harmonic 0.014%

Input RMS 85.9dB Distortion at 999.9Hz, -20.3dB FS Based on 8 harmonics THD 0.377% 2nd harmonic 0.289% 3rd harmonic 0.068% 4th harmonic 0.017% 5th harmonic 0.203% 6th harmonic 0.011%

These results are exceptionally good, showing well below 1% total harmonic distortion at both frequencies.  These results again confirm the high quality audio output produced by the FiiO S5.  What's even more impressive is that this distortion measurement is cumulative of the entire playback and measurement setup, of which the S5 is just one component, so the actual distortion it is producing is even less than what's measured here. And lets not forget these measurements are not taken in a anechoic chamber under ideal laboratory conditions, but in a real life setting of a typical office with inexpensive test equipment.

I came away from this test completely impressed by what the FiiO engineers have accomplished.  The fact that the S5 is a well engineered product not only evident in the exceptional sound quality it produces, but is confirmed by measurements that shows the underlying technical capabilities of this great little audio device.