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Abacus C-Box 4
4.75 4.75 out of 5, based on 1 Review

Tiny active speakers that promise to deliver a full range sound. Did Abacus bend the laws of physics?

16th August 2019

Abacus C-Box 4 by Solidtrax

  • Sound Quality 5 out of 5
  • Ease of use 5 out of 5
  • Features 4 out of 5
  • Bang for buck 5 out of 5
  • Overall: 4.75
Abacus C-Box 4

For the past couple of weeks, we've been working on a set of active speakers that are, without a doubt, smaller than any other active speaker we've ever worked with. But the funny thing is, we don't feel they sound like compact speakers at all. Meet the Abacus C-Box 4!

The Company and the C-Box
Founded in 1983, Abacus is a Germany based company specialized in designing and manufacturing audio related equipment, like active speakers, subwoofers, (pre)amplifiers and digital streaming devices, which are all handmade in Germany. The most affordable line of active speakers they build are the C-Box, which they offer in two versions, the C-Box 3 and C-Box 4. Saying that the C-Box 4 is bigger than the C-Box 3 is totally true, but it feels not right. Instead, we would like to say that the C-Box 3 is even smaller than the C-Box 4. Yes, these sealed active speakers are seriously tiny! We know that tiny speakers are not rare, but once you start reading the specifications, you know things get pretty special all of a sudden.

The C-Box 4, which measures only 160mm x 160mm x 269mm (D x W x H), is supposed to have a frequency response of 32Hz to 20kHz at -6dB. These are numbers that you normally find in much larger speakers or studio monitors with a much larger woofer. The woofer in the C-Box, responsible for the lows and the mids, measures 5,75" (140mm) and the tweeter measures 1" (25,4mm). You will find no bass reflex or passive radiator, this tiny speaker is completely sealed. Inside every speaker you will find two Abacus amplifiers, one is responsible for the tweeter, the other is responsible for the woofer. Combined, they deliver roughly 25 watt RMS. Even though they are compact, they don't feel like toys at all, with a weight of 4,25 kg per speaker. On the back of the speakers you will find a RCA line input, which is the only audio connector available. There are two knobs, one controls the overall level of the speaker and the other is for the Bass EQ.

Testing Setup Room 1
Since we are a duo with both our own studio space, we decided to test the C-Box 4 in both our rooms. In room 1, we've placed these cute little speakers on stands behind the desk and we made sure that they had the right height so that they aligned nicely with our ears. We've experimented a lot with their placement, but finally we ended up having theme at 1.2 meters away from the seating position and also roughly 1.2 meters between them, putting them in a nice triangle. This puts the speakers at roughly 1 meter away from the back wall. This room features just some minor acoustic treatment with two bass traps and two wideband absorbers. We've connected these speakers directly to an Universal Audio Apollo Twin. We didn't know if these speakers needed any "burn-in" time, but just to be sure we've let them play some music on moderate levels while we where away for a few hours, before we started auditioning them.

Time to play (Room 1)
As always when we audition monitor speakers, we start with listening to some songs we're very familiar with from artists like Deadmau5, Dom Kane, Oliver Schories, Stephan Bodzin, John Mayer, Adele, Khalid and Benni Chawes. While listening to a variety of songs, we experimented with the Bass EQ knob on the back of the speakers. With the bass on the maximum level, depending on the room acoustics and how you have set them up, you can get such an incredible deep bass from these tiny speakers, that you start to wonder how that is possible. Of course, having the bass set at the maximum position will have effect on the maximum SPL the speakers can produce. For this particular room and to our combined taste, we liked it the best with the bass on roughly 75% of maximum capacity. We felt this was a nice balance between a deep bass (for the size) and sufficient SPL to be able to play the speakers loud enough.

During our auditioning of the C-Box 4, we both agreed early on that these are very revealing, but in a nice way. We would like to describe the sound as being on the fresh and forward side of neutral. Mids and highs are very detailed and sound overall convincingly realistic, but never get harsh or cause listening fatigue. We really praise how it reproduces vocals, especially male vocals. In our experience, small studio monitors often fail to accurately and naturally reproduce male vocals, but with the C-Box 4, we believed this was no struggle at all. John Mayer, Benni Chawes and Damien Rice for example sounded as real as it gets, with just the right amount of warmth. We also think the stereo image and phantom center is phenomenal, the speakers basically disappear and you forget you are listening to tiny speakers and you simply enjoy what you hear, with sounds coming from places that are beyond the speakers themselves.

But what about the lows? Do these speakers actually go down to 32Hz as stated on the website? Absolutely, they do! We've tested them with a sine wave and we could hear them all the way down to 29Hz, which is seriously insane for their size. But in practice, especially when it comes to modern pop music and EDM, they don't have the SPL capability to deliver a chest pumping kick drum, at least not in this particular room at their current position. Once we moved them closer to the back wall, room gain started to help the speakers in the lows, which made them capable of actually delivering that chest pumping lows which you normally associate with much larger speakers. However, the downside to this is that the stereo image suffered a bit and the mid range lost some of that magical clarity we've come to love. So how will this speaker behave in our other room? Time to find out!

Testing Setup Room 2
This room has a lot more acoustic treatment, from bass traps in all corners, to wideband absorbers and diffusers on the left, right, rear and ceiling. Again, we placed both the C-Box 4 speakers on stands behind the desk at ear level. After some experimenting with their setup, we ended up having them at roughly 1 meter from the seating position and little over 1 meter between them. Not exactly a perfect triangle, but we both felt this sounded best. We've connected them to a RME UFX II interface.

Let's continue (Room 2)
The first things we both noticed is that they performed pretty much the same as in our other room, even though the rooms are very different. There was some difference in the high-mid and highs, as it sounded just a tiny bit brighter than before, but once we decided to correct this with some subtle EQ cuts in the RME interface, it quickly sounded like we remembered it sounding before. We both figured it would have been nice to have a mid and treble control on the back of the speaker, but it's certainly not a deal breaker in our opinion that they are absent.

We think it's very commendable that these speakers, for the most part, seem to perform pretty much identical in two very different rooms. With other speakers, especially the ones that rely on a bass reflex or a passive radiator, the difference in performance was often much bigger.

Last Words
We wanted to test the C-Box 4 because we where curious if a speaker this compact could really deliver a full range sound. To our surprise, they indeed seem to be pretty much full range. It's like the people at Abacus where able to bend the laws of physics when they designed it. But despite being able to dig really deep, they can't do that with lots of SPL, so don't expect chest pumping kick drums, at least not without the help of some serious room gain. But enough about the lows. What maybe impressed us the most is their fantastic mid and high clarity and their fabulous stereo image. It is such a breeze to setup reverb levels and decay times and you can hear the tiniest EQ and compressor changes you make. For €890 (€790 for the rest of August) you get a set of tiny little miracle speakers that are really fun to mix on. We recommend them highly!

Visit the C-Box 4 product page

Thanks to Abacus for lending us a pair of the C-Box 4 for this review.

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