In the world of audio enthusiasts, there are many options and choices to be made. Some can almost be seen as polarizing, such as tube sound versus solid state or analog versus digital. Of course, any reasonable person will see these as options to explore rather than a cause to become dogmatically entrenched in… but sometimes people take this hobby a bit to seriously.
Among the most polarizing options is the use of equalization. Detractors contend that in order to enjoy the music as it was intended, the signal needs to remain pure and unmolested. Fans of equalization counter that a good EQ simply fixes flaws in the reproduction chain, meaning the EQ is actually helping produce a more pure accurate sound. Obviously both sides want the same thing but disagree on how to get there.
The reason so many people dislike equalization is likely due to its poor history of implementation. The traditional “treble” and “bass” adjustment knobs, utilized for decades, are very limited in scope as to what they can do, and the classic “loudness” button is more concerned with bass boost at lower volumes. Over the years EQ has become much better, but there are still many devices (Sansa Fuze and Clip for example) that don’t have a passable EQ option. Unless you have used a DAP with a good EQ like a Cowon or Samsung, you might have no idea how a good EQ can actually help you enjoy music.
Enter the digiZoid ZO. They market the thing as a “personal subwoofer”, which is an interesting way of saying it is a portable hardware based EQ box with an emphasis on the low end. It also acts as somewhat of an amp although it does is not really advertised as such and does not have its own volume control. The theory is that you run your source flat (with no EQ or bass boost applied) and then send the signal into the ZO which takes care of it from there, thus adding a (hopefully good) EQ option to practically any device. The ZO sells for $119 and comes with a 60 day money back guarantee.
The item itself is about the size and shape of an iPod Nano, although it is a bit shorter (roughly ¾ of an inch) and a tiny bit thicker (1/10 of an inch). It is made of plastic, is very lightweight, and has a gloss black plastic finish that looks quite nice but attracts fingerprints easily (think black Sansa Fuze). Much like a portable amp, it has a pair of 1/8th inch jacks; one for the input, one for headphones. The only control is a combo rocker wheel/button on the side which is responsible for powering the ZO off/on as well as adjusting the level of EQ that is applied. When powered off, the unit operates in “bypass mode” which means it allows the original signal to flow through to the output with no processing applied. The rocker wheel portion does not adjust volume as you might assume (again, this is not really a typical amp) but rather lets you choose between 32 different EQ curve settings. A small LED lighted window gradually changes from green to red with each step of adjustment, red indicating maximum processing. The whole thing is elegantly simple to use; as I type this I realize it would likely be quicker to learn it all by playing around with the device than it is to read this paragraph.
The packaging is quite nice, and it looks like a retail product. Bundled accessories include a 4 inch mini to mini cable, a 40 inch mini to mini cable, a mini-USB cable for charging, and a user guide.
Visiting the digiZoid website (www.digizoid.com) there are lots of marketing claims thrown around. They say their product is “the world's first speakerless subwoofer & electronic audio enhancement device for portable media.” Some of this marketing speak can seem a bit overwhelming, but the bottom line is that they are claiming a unique way of reshaping sound to make it sound better than would normally be possible. Here is a helpful quote from the website:
“digiZoid® SmartVector™ sound contouring technology utilizes a new method of sound enhancement, which is expected to become the foundation for future audio system design. It doesn't employ standard audio enhancement techniques such as: cross feed, low-frequency bandwidth extension, common equalization schemes, or digital signal processing algorithms.
Instead, we approached the problem from a different angle, and engineered from the perspective of the human auditory system. Our solution is therefore based on principles of hearing sensitivity, psychoacoustics, and in particular, psophometric filtering. SmartVector technology deviates from many of the established audio industry standards; and as a result, breaks some well-known stereotypes (i.e., you can't get big bass out of small speakers, because you actually can with SmartVector).”
I was going to look up the term psophometric filter, as I had never heard of it, but the website handily shows a definition:
“A filter whose response is based on that of the human auditory system”
My initial reaction when encountering all this information was that this product might sound convincingly good for the masses, but it probably not designed with headphone enthusiasts in mind. After spending some time with it, my opinion has changed for the most part.
I used the ZO with a Sansa Fuze, Sansa Clip+, an old Insignia Sport player, and a QLS QA-350 solid state transport. I tried various headphones from low to high end, in ear to full size. I listened to all types of music. I also watched a few movies on my PC via Netflix streaming video.
Overall I am impressed with the quality of sound that the ZO produces. When used at the lowest setting (green) which I call level 1, the unit supposedly doesn’t apply any sound contouring measures, but simply acts as an amp. Even so, there ends up being an inherent bass boost that is definitely noticeable, as long as you are using some capable headphones. If a headphone is able to benefit from amplification, you will certainly notice it when using the ZO in this manner, as you would when using any amp of reasonable quality. If the headphones do not require amplification, then it will just sound the same but louder. Even as just a standalone amp, the ZO is pretty decent; better in my opinion than the usual suspects like Fiio, and on par with some of the better cmoy designs out there.
The real fun begins when you start moving further up the scale of contour profiles. As you can see on the chart here http://www.digizoid.com/tech each step up gives you further enhanced bass as well as a bit of high frequency boost. I don’t quite consider myself a full fledged bass-head, but I might be border line. Even so, the higher contour levels are a bit too much for me. At those levels, to my ears the bass starts becoming too unrealistic and unbalanced. To be fair, it sounds much better than other extreme bass boost EQ features that I have heard, and some people might enjoy it.
There are 32 levels of adjustment total. I found that my preferred zone was somewhere in the yellow to orange zone, meaning roughly steps 3-20 or so depending on what headphone I was using, the music, and my mood. I also found that the quality of the result varied quite a bit. I found that I generally preferred to keep high end headphones to their stock sound, which meant using the very lowest setting. Headphones like the Westone ES3X, Monster Turbine Pro Copper, and Sennheiser HD600, all have an excellent sound which benefits from the “level 1 amping” but does not really lend itself well to the sound contouring. Perhaps it is just that I am very familiar with them and any change to the sound signature is unwelcome, or the fact that they already have excellent bass reproduction with a fairly balanced sound signature. Whatever the case, they did not sound terrible with a higher contouring level, but ultimately I prefer to go without.
On the other hand, many headphones (mostly in the low and lower mid range with regards to pricing) benefit quite a bit from the extra boost of the ZO. A large but incomplete list includes: Soundmagic PL-30 and PL50, Ultimate Ears SuperFi 3, Koss Portapro and KSC-75, Audio Technica AQ88, Phonak PFE, Head Direct RE-2, JVC FX300, Etymotic ER6i, ADDIEMs, Equation Audio RP21, and AKG K271 original edition. Many of these were borrowed so I’m not an expert, but I used the bypass feature a lot to try and get a feel for their basic sound prior to boosting it with the ZO. Looking at the list, it seems that a common theme is IEMs that are somewhat neutral or bass light. The ZO is very good at taking those types and giving them a bit more kick. But also note that some heavy hitters like the Equation RP21 and the Koss siblings showed a good improvement as well.
I struggle a bit to explain how things sound with the ZO activated. Generally speaking, there is an increase in bass, not just volume but the presence and texture. Bass drums for example can often sound not just like they are being given more volume in the mix, but almost as if the drummer is playing it harder, resulting in more impact and energy. As long as you stay in the previously mentioned zone of yellow to orange, the bass not intrude or overwhelm the rest of the spectrum. Push it too high into the red zone and things generally start to get messy, with bass blurring into the mids and making the whole thing unbalanced. Even if that didn’t happen, for my tastes the yellow zone is plenty of bass; other opinions may vary.
Aside from the bass impact, there is also a subtle boost in the upper midrange and high frequencies. This is less immediately obvious than the bass improvement, but arguably more important. What it ends up doing, depending on your headphones, is giving you a somewhat different take on your music. There is an old review cliché that goes something like “I heard details I have never heard before!” In this case, I think my attention was drawn to things that I had not paid much notice to in the past. The first time this struck me was listening to Metallica’s “Black Album”. I found myself constantly noticing Hetfield’s rhythm guitar instead of focusing on the lyrics or the lead guitar as usual. I switched it up and tried the classic BT album “ESCM”. Again I found myself tuning in to all the little background details, which the album is packed full with, rather than focusing on the music as a whole.
This shift in focus of details, combined with the enhanced snap of the bass drum (and often the snare drum too), made for a very appealing sound. I especially liked it with various genres of electronic music. I also felt it really enhanced the sound of classic rock; many of my favorite albums from the 60s and 70s were recorded in such a way that makes the drums sound rather anemic, and the natural sounding boost from the ZO really brings them to life. That could just be the drummer in me talking.
In the end, I was able to find examples from every genre of music that sounded great with the ZO. At times I preferred to leave the ZO on level 1 for a flat response, but more often than not I found I appreciated at least a low level of contour enhancement. Again it is very dependant on the headphones being used and on your mood. I wish I could better articulate how it sounds, but it is something you really have to hear to understand. I can say this: For some of my headphones, the ZO helps them give the best bass performance they have ever given. For example, my Audio Technica AQ88 clip-ons. Ordinarily they have absolutely ZERO bass. Using a normal EQ, I have never been able to coax any sort of realistic sounding low end response from them. With the ZO turned up to medium setting, the bass actually pounds a bit. It is impressively convincing; they sound like completely different drivers, and the impact seems real. I guess this is a result of that psophometric filtering that they mentioned. However it works, I like it.
I watched some movies with the ZO, and was even more impressed with this little unit. My theater room features dual 15” Triad subwoofers, so I’m used to a fairly high amount of sub output when watching films. The ZO was able to give me a much closer simulation of that when used with most headphones as compared to just using the headphone jack on the computer. The audio on streaming Netflix videos seems roughly equivalent to medium bitrate mp3 compression, and overall it is not as smooth and dynamic as a Blu-ray with a lossless audio track, but with the ZO I was more than satisfied with what I was hearing.
There are only a few things I could find to complain about, and they are relatively minor. My biggest complaint relates to the input/output jacks on the bottom: they need to be marked. The manual shows them as having little arrow labels indicating signal flow, but my ZO does not have any such markings. On multiple occasions, I plugged my source and my headphones into the opposite jacks. With this configuration, you still get sound when the unit is powered off (remember the bypass function) but when you power on the sound is gone. This made me think my battery was too low to produce sound, which was not the case. A simple label, etching, or other method of identification would be very helpful to avoid this problem. Aside from that, the thing is a fingerprint magnet, just like every other shiny black device. The complaints end there. Build quality is good, battery life is roughly 10-12 hours, and the size is perfect in my opinion. Some may balk at the lack of a dedicated volume control, but once again, this is not a traditional amp. This didn’t really bother me; with all of the sources I tried, I got fairly clean sound just by using the headphone out. My worst sounding player, the Insignia Sport, still gave pretty good sound in this manner, so I don’t think it is a big issue. There is a tiny bit of hiss with certain IEMs but I never found it to be too bothersome. I have not had a chance to try the ZO with speakers but based on headphone performance I imagine a small pair of powered monitor speakers might get a nice boost. A common trait of cheap headphones and PC speakers systems is a sloppy, over boosted lower frequency section. The manufacturers, perhaps rightly so, conclude the general population will confuse the increased bass quantity with increased bass quality, which unfortunately many people do. I don’t believe the ZO will be a good match with those types of headphones or speakers. Thankfully there are many good options available at reasonable prices that don’t suffer this problem, and the ZO should play well with them.
When I first checked out the digiZoid website, it seemed suspiciously full of marketing talk, and the ZO struck me as one of those products designed for the uneducated masses who don’t know the first thing about good headphone audio reproduction. I’m happy to report that is not the case. The ZO hits more often than it misses. It is a well thought out product, and really stands apart from other amps. If all you want is an amp, there are plenty of choices out there in this price range. But none of them offer the unique sound enhancing technology that the ZO offers. It proved to be very versatile by working very well with many different headphones, and brought a unique spin to the music that was fun to listen to. If that sounds good to you, I suggest you give the ZO a try. As I mentioned, they offer a 60 day money back guarantee, so you are free to experiment with it and see if the sound fits your taste. It would end up costing you about $5 or so to ship the unit back to digiZoid if you decide the sound is not for you. When companies offer generous refund policies like that, it inspires confidence that they really believe in their product and think most people will too. At this point I have to say I agree with them. The ZO is far from a typical audiophile product, but it earned its place in my collection of gear by sounding unique and fun, and I recommend it for bass lovers everywhere.
*Note that this is my own cable, not the one bundled with the ZO.
Edited by project86 - 7/28/10 at 7:04am