Before this more extensive evaluation, I had heard the Sonorous IV briefly once before at a local shop and found myself drawn to the experience - being quickly attracted to the ‘full and rich’ sound with sparkling highs. Upon a more lengthy evaluation, however, it’s clear that the final (pun intended) story on this headphone is a bit more complicated. I was able to test it thoroughly on my own system for an appropriate period of time and have come to somewhat mixed conclusions.
The Sonorous IV is unique in that it’s a dual driver headphone, with what appears to be a 50mm dynamic driver handling the lower frequencies and a balanced armature driver joining in above 2.5khz, although it’s not clear if these two drivers handle those ranges exclusively. You don’t generally see this kind of system so I was intrigued by the idea. Moreover, Final Audio is a company that has flown under the radar a bit in North America and deserves more attention, especially given their excellent line of IEMs and the fantastic D8000 flagship that made waves in 2018.
Primary source: iFi iDSD Micro Black Label. I tried the Sonorous IV on the single ended output of the Cayin IHA-6, but the output impedance was way too high. For prospective buyers, note that because of the inclusion of the balanced armature driver, you’ll need to run this from a low output impedance source to be able to retain the default frequency response (impedance and phase measurements show some nonstandard results in the lower treble).
Design & Comfort
Right away this is a very comfortable headphone, even if it is a bit bulky and awkward looking. It has a free tilting cup system that I love, which allows it to perfectly adjust to your head and ear position. I rate this slightly more comfortable than the Focal Elegia and more comfortable than the Mrspeakers Aeon Flow series, but not as comfortable as the Audioquest Nightowl. It weighs around 400 grams so it’s not light, but the wide (albeit simplistic) headband allows for even weight distribution. The pads on the other hand are a bit too shallow for my ears, and I find that if you have somewhat prominent earlobes like I do, they will get squished by the pads. For most people I imagine this wouldn’t be an issue, but if you have big ears like me, this may raise a flag. Also, the balanced armature driver appears to be implemented on the front edge of the cup, meaning it protrudes past the dynamic driver and into the cup by the pad slightly. I didn’t find this to be an issue, but I could see it causing problems for certain ear shapes.
This is a reasonably fast headphone, and notably faster than the Nightowl, however it’s not on the level of something like the Aeon Flow Closed or the Elegia. Its resolution is also appropriate for the price, providing excellent detail retrieval that’s superior to something like the Meze 99 Classic and Neo, roughly on par with the Fostex TR-X00 or similar Fostex headphones, and slightly behind the Aeon Flow Closed. The Sonorous IV’s strengths are in its soundstage for a closed back and its timbre. I mentioned earlier that it has a very ‘full’ sound, and while that can be difficult to measure or discuss properly, it needs to be reiterated. It’s possible that the success in this area is due to the dual driver design, allowing the dynamic driver to focus more of its efforts on the lower frequencies, leaving the more ‘airy’ and open elements of the frequency response to the balanced armature. This is likely Final Audio’s answer to the question of “how do we make a closed back sound more open”. On the flip side, however, the tonality of this headphone makes it difficult to properly evaluate these performant qualities without EQ.
Tonality & Frequency Response
Bass - While I emphatically classify this headphone in the ‘fun’ sound category, not unlike some of the heavy hitters such as the Philips Fidelio X2 or the Fostex TR-X00, the Sonorous IV has an atypical ‘N’ shape, rather than the usual ‘V’ shape. By this I mean that the bass to mid transition is more of a slight downward slope, and not as immediately recessed above 200hz. There is a bit of a sharp bump in the upper bass, but not enough to cause it to bleed into the midrange. In fact the bass to midrange transition when listening to music is quite pleasing, with enough slam down low and enough distinction to be able to isolate and follow instrumental lines that sound tonally rich and well-defined. On lesser headphones, this area can sound bloated and flabby by comparison (Meze 99 Neo).
Midrange - As with the bass, there’s little to complain about here. It’s perhaps not as forward as I’d like, but I think it’s totally appropriate in relation to the bass. I would like to say that vocals come through well, but unfortunately they don’t - but that’s not at all the fault of the mids. The ‘N’ slope continues into the treble, which is where the major tonality problems show up.
Treble - Measurements of the Sonorous IV show a seriously bizarre cut-out right at around 2.8khz, and this is likely where the balanced armature driver kicks in - or perhaps this is the transition spot. But interestingly this isn’t the problem when actually listening to music. In fact I don’t know if that cut is even audible, it certainly doesn’t get in the way. What does get in the way is the massive cut that shows up between 5-8khz, and then the peak immediately thereafter. This peak is where the ‘N’ shape spikes upward, and unfortunately that also happens to be right where the sibilance range kicks in. This can lead people to think the headphone is overly bright sounding, and it totally messes with vocals and any of the nice midrange that’s present. With an EQ boosting 5-8khz by a few db, things improve, however the main issue with the treble is that 8-10khz has a kind of artificial grain or sharpness to it that causes sibilance to be particularly grating. While this sounds bad, and in a way it is, I personally don’t mind a bit of grain or edge to my headphones. For example the Audeze LCD2C and HiFiMAN HE-500 both have a more aggressive edge, and this can lead to a headphone sounding more energetic and exciting. The problem with the Sonorous IV is that there’s too much of it, and it’s as if they cranked up the sharpness to give the illusion of detail when in reality it’s just grain. Think of the sharpness slider on your TV or monitor, and imagine turning that up to the max. You’re not getting extra resolution or detail, your eyes are simply drawn more strongly to the image - and at 8-10khz, that’s not really what you want. This is a far cry from the treble smoothness of something from Sennheiser or even HiFiMAN’s latest offerings.
EQ - This headphone was tricky to EQ to where I like it. I had to use an existing compensation preset and then edit from there. Even once it is tuned to a target curve, the 8-10khz grain or ‘fake detail’ is still a bit much. So my recommendation is to get close to a curve you like, and then reduce the sibilance by a few db, but I have to admit I’m more sensitive to that than most. If you prefer a bright headphone this might not be an issue, but personally I think this headphone should have been tuned more closely to something like an LCD2C, and then it might have even been stiff competition for Audeze, given its performant qualities are quite good. Once I was able to tune it how I liked, it sounded remarkably similar, and it even retains some excellent musical timbre that other higher end headphones lack.
This is a weird headphone, no doubt about it. It does some really good things - especially in the bass, mids, and with that ‘full’ sound I mentioned. If you’re looking for a closed back Fidelio X2, or the treble in that headphone doesn’t bother you, this might be a good candidate. I’d even go so far as to say the performance of the bass/mids on the Sonorous IV are superior to those of the Fidelio X2 (to my preferences). However it does require EQ - enough that if you’re someone who doesn’t EQ anything, I’d have a hard time recommending this over one of those Fostex headphones or the E-MU Teak, that is if you’re looking for a closed back ‘fun’ sound. With that said, those don’t quite hit the same soundstage or ‘fullness’ of the Sonorous IV. I get that this is a difficult quality to properly describe, so this has to be a “try before you buy” headphone to get a sense of what its most interesting qualities entail.
Check out my video review for more thoughts on the Sonorous IV