Unique Hardware HUMP NF02 speakers are miniature hi-fi speakers with USB and analogue line input connection. Tiny - each speaker fits in a hand's palm - yet powerful in sound and with a clarity that many larger speakers can't match. Those are literally "pocket hi-fi" speakers - they're small enough to be carried in a coat's pockets or a backpack. With an optional AA battery pack or AC/USB adapter they can work as a portable player companion, as voice speakers for presentations, language lessons, etc.
Review
HUMP NF02 are pocket speakers.
Based on the Humming port principle; sound waves from dual speaker drivers collide and compress, producing waves of lower frequency. This allows the speakers to generate shorter-length sound waves (corresponding to low frequencies).
The standard kit on sale includes the two speakers, a combined mini-amplifier/USB soundcard module, and the USB connection cable. Connection module can either be plugged in as a USB soundcard, or have an external device plugged into its minijack socket, in which case the USB soundcard output is muted.
The USB soundcard part is an implementation of a href="http://www.micronas.com/products/by_function/uac_3553b/product_information/index.html" target="_blank">Micronas UAC 3553B integrated controller, done by ESMT, as an AD62551A integrated controller (ESMT's addition was a class D amplifier). UAC 3553B is capable of 6-48000 Hz/24-bit sampling, -90 dB THD and 96-dB SNR. Recognised automatically by Windows & MacOS X as "USB Audio Device".
The kit sent for review also included an AC/DC adapter and a battery pack with a USB socket. The battery pack takes four AA batteries and is a special blessing as it also allows charging a digital audio player... Like the Cowon T2 in the photo below.
That is the most interesting bit; although there are some USB-based mini speakers like Roland's Edirol UA-1EX mini-speakers, they require a USB connection and don't have an analogue audio input. There are the Maxell FPS series of inexpensive flat-panel speakers, but the FPS-2 lack a USB connection option. NF02 can double as portable battery-powered speakers and USB soundcard/speakers, and they cost less than fancy competition from the likes of Logitech, Harman/Kardon, etc.
The mini-amplifier/soundcard module has three buttons - volume "-", "+", and "mute", a standard USB mini-socket, stereo minijack line input and two speaker output sockets.
Sound
Sound-wise, they're very detailed and clean. More detailed than the older Kenwood LS-M35S bookshelf speakers. The Kenwood speakers can certainly kick, but they're also boomier (with a reflex tube tuned quite low) and lack the higher-frequency detail.
NF02 frequency response graph looks somewhat similar to that of Sennheiser PX200:
Both have a -3dB cutoff at roughly 300 Hz. Except the NF02's graph looks cleaner - and they certainly play a much cleaner and more natural sound.
Frequency response graphs of headphones are often uneven because human hearing itself has an uneven sensitivity to different frequencies.
Here's a graph for Fletcher-Munson curves, representing equal loudness for human hearing.
Hearing is most sensitive to midrange at ~80 dB, becoming most sensitive to high frequencies at threshold of pain (~120 dB), and relatively straight at 100 dB (house-shaking loudness, which explains why parties and clubs tend to blast music at roughly 100-110 dB).
Headphones, being so close to ears, tend to be adapted to match human head-related transfer functions (HRTF), often faking pinnae high-frequency damping, or mimicking frequency response of a hall (diffuse-field, or DF, equalisation). Here's a sample HRTF, showing which frequencies a human ear model receives, but not which frequencies hearing is sensitive to.
The ideal speakers might have a completely straight frequency response (unlike headphones, where a straight frequency response can sometimes be painful), but regular consumer speakers usually measure very far from that. Typical "multimedia" single-driver speakers (also known as "cube speakers") can measure really nasty, and they usually have abysmal high-frequency response, veiling detail and sounding rather suppressed.
What's astonishing about the NF02 isn't the bass (which is there), but the high-frequency detail. The two graphs, PX200 and NF02, sitting together, are a good illustration. All the extra detail that usually appears in headphones is due to excellent high-frequency reproduction of headphones. Headphones are usually single-driver, so they don't have to deal with crossover circuits or speaker enclosures (any speaker box adds reflexions) and they sit next to the ears, therefore not having to spend as much power.
Playback of Music
NF02 are very, very close to headphones in detail. The only area where they lack is sub-bass and low bass, but for their size they can kick - snares and bass drums, even TR-909 analogue toms (which Cowon T2's earbuds fail to play correctly!) all sound like percussion, unlike any regular small speakers with similar tiny metal drivers.
Bjorn Lynne's "Beneath Another Sky", full of powerful, bassy pads and electronic percussion, played at listening volume out of Cowon T2 on the street, with the battery pack attached to speakers.
Our own Audiotest stress pieces like Tranq-F.flac (Fender Jazz Bass, Korg synthesised strings and a Moog Mini sweep pad) and a saturated Moog sine wave pad passage played without distortion at approximately 85% volume of the USB sound device. Instrument-thick Moon Arpeggio played without any distortion. NF02 do not distort harshly, either - they discard any bass notes they can't play.
Like many small speakers or headphones, the NF02 have an elevated treble; some people don't like that, proclaiming instantly a "lack of bass". Canalphones can be similar: low frequencies are there, and clear and powerful, but they can be overtaken by midrange, treble and very high frequencies. It can take time for hearing to adapt to the tonal balance, but just as with canalphones, the detail is welcome.
NF02's mildly elevated treble and a clean midrange combine to make the overall sound involving, airy, ambiental. Mick Harris' Hednod Sessions album was hypnotising and "dragging through the speakers" into the music itself.
Loudness
Out of the Apple Powerbook, the speakers are powerful enough to fill a room with sound. They can play much louder than the size suggests (and much louder than regular notebook speakers, too). Of course those are not bass-heavy shoutboxes, but acoustic records, classical music, even some drum'n'bass music plays with much better detail than any small "multimedia" speakers or notebook speakers can manage. As long as there is no monster sub-bass in the mix - and there seldom is in regular CDs - the NF02 will play music smoothly.
NF02 certainly won't rearrange furniture, but their loudness is enough to fill a room with sound. It won't be very bassy sound - mostly midrange and treble. To bookshelf speakers, they're what PX200 are to real headphones. With a much cleaner sound than the PX200, of course.
With a friendly EQ and a +10 dB EQ boost in ITunes, the NF02 can play louder without distortion than with the Powerbook's volume boosted to 100%. Powerbook's analogue filter overshoots when going past 90% of volume bar (or roughly -3 dB), and NF02's amp gets a clipped signal. Gain boost gives an additional power boost to speakers, even in USB mode.
Portability
Each NF02 speaker fits in a hand's palm. They can be pocketed in a jacket or coat, or carried in a small bag. The AA battery pack and AC/DC adapter are sold separately, as optional accessories. Those are necessary for HUMP NF02 to work as standalone speakers, without a USB connection, and make them a great portable player companion.
That's a muffin at the left.
Standing on an Edirol MA-10 speaker, with Denon AH-D1000 headphones.
Equalisation
The NF02 can handle everything quite well, but with the rare overly-bassy tracks they may need some help.
An EQ cutoff starting at 300 Hz, with 300-250 Hz at -1 dB, 200 Hz at -2, 160/140 at -4 and 60 Hz at -6 dB ought to prevent any distortion caused by overly heavy bass.
For voice playback, very high frequencies and bass can be depressed, as in the screenshot below:
NF02 played louder with the AC/DC adapter (rated at 5V/1000 mA, that is, 5 W) and, ironically, taking power from an Apple Powerbook's USB output, than with a PC motherboard's USB port.
For tasks like voice presentation, an AC/DC adapter or the battery pack could be used, together with a portable player and a voice EQ like the one above (telephone range is 300-3000 Hz; for voice presentation, frequencies below 250 Hz can be cut, midrange boosted to increase loudness, and high frequencies also depressed).
Conclusion
Unique Hardware HUMP NF02 speakers have the best sonic detail of many small portable speakers, outperforming regular bookshelf speakers when it comes to clarity.
NF02 are the most detailed speakers in its own class of miniature speakers. They do qualify as portable hi-fi speakers, pocket hi-fi speakers even.
NF02 are on sale at Unique Hardware's classily named HUMP Unique store. The price for NF02 hovers around US$60.
Highly recommended.
A videoclip of the speakers playing "Another Brick In The Wall".
And another clip, demonstrating bass & percussion reproduction.
Distortion's courtesy of the mobile phone microphone.
