FiR Audio M4

DITA Oslo cable.

Usually I will include a few interesting cable pairings in my reviews, but with the MMCX of the M4 I am unfortunately not able to do that. All the cables I have available have 2-pin connectors and I don’t have those nifty little adapters in order to use them with MMCX IEMs. However, Project Perfection did send along one cable for me to try out: the DITA OSLO cable. Alex has reviewed it here on Twister6 separately, but this time Project Perfection specifically wanted us to have a look at the synergy with the FiR M4.

The OSLO cable is a very high purity copper cable that has been specially treated and as such the name stands for Oil-Soaked Long-crystal Oxygen-free (OSLO). The build quality of the cable is great. It is a fairly thin and very supple cable that comes (in this case) with high quality MMCX connectors, the signature round DITA Y-split and of course the Awesome Plug, which I am a very big fan of. Since the DITA Dream XLS came with its own OSLO-XLS cable, I have been using this cable a lot and found it very comfortable. The main difference here with this OSLO cable and the M4 is that the connectors sit on top of the M4’s protruded sockets and that makes it a little high compared to the M4’s stock cable where the connectors slide over and sit nice and flush. Not a big deal, but if the OSLO’s MMCX connector would sit the same way, I think it would improve comfort even further. Of course, that would be an issue for other IEMs where the MMCX sockets are recessed, so perhaps it is unavoidable.


The OSLO cable also comes with a little bottle of the oil solution that is used to treat the cables, which can be used on the connection of both the Awesome plug (i.e. the four connectors you see when changing the plug) and the MMCX (or 2-pin) connectors. An aftermarket cable supplied with a bottle of oil, you say? Cue the snake oil comments! Given the hostility of some to anything to do with aftermarket cables, I think that is quite a gutsy move. Even I was skeptical about it, but I gave it a fair try anyway.

And to be fair, if you call it a “contact enhancer” it all becomes a bit less controversial. I used it on two IEMs that have seen a lot of use, just to see if I could notice a difference. It was not possible to A/B because once it’s on, it’s on and I wasn’t going to clean the connectors and reapply it several times. I am dedicated to doing thorough reviews, but I do have my limits. I first tried it with my DITA Fealty and felt that perhaps there was indeed a slight improvement in clarity, or perhaps just a cleaner and a little more stable sound. The difference was not huge and to be honest, I doubt I will ever use it purely for sound improvement. However, there was one point where I did find it incredibly useful and that was when I applied it to the Final E4000. Those have seen a lot of abuse as part of my boot camp review, where I went running in the pouring rain, the freezing cold, the blistering heat and had sweat pouring over the MMCX connectors during indoor bike trainings (talk about a thorough review…). By now the connectors have started suffering from frequent cut outs and I was about to accept their sad demise. Applying the contact enhancer however completely solved the issue and it gave the E4000 a new lease of life. So in that sense it was unambiguous that it indeed helped improve the quality of the connection.


The pairing of the M4 with the OSLO cable is a really good one where I feel the synergy between the two is bringing a few notable changes. The overall brightness of the M4 is toned down a little to the point where I can use the PAW6000 as a source again without having any problems with the treble (still using the Sony tips though, but purely because I get the most comfortable fit with those). The stage seems to open up even more than it already was and creates one of the biggest stages I have heard so far that stretches very wide with great depths, although height still seems to be similar. The bass of the M4 gets even more texture and a bit more body without loosing the tight control or impact. The little bit of extra warmth this generates helps to make the mids a little fuller and I feel this gives the mids a bit more naturalness. That is of course because it is more in line with my own personal preferences, as I tend to prefer a slightly warmer signature. Because of this the mid range also gets a little bit of the liquidity I mentioned in my review of the DITA Dream XLS, where in a very similar way to the Dream XLS, the M4 and OSLO pairing gives this sense of the notes flowing from one instrument to another. This is something that I felt very clearly with choral music, where for instances in Bach’s Cantata #140 the voices flowed almost like water (hence the term “liquidity”) without negatively affecting separation. Treble I feel is quite significantly affected -perhaps due to my sensitivity- and becomes sweater. I personally think this gave cymbals a more natural sound, less bright than with the stock cable, but still very well extended and incredibly detailed while having a great sparkle. That worked brilliantly for my treble sensitivity. [insert: big grin happy face]

I think the synergy between the OSLO cable and the M4 is very good and that combined with the comfort of the cable and convenience of the Awesome Plug, it makes for a very good upgrade from the stock cable. It is a little warmer and so it will depend on personal preferences if that is the direction you would wish to go.

Page 4 – Comparisons, and Conclusions.

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