So, from left to right: HD800, HD650 (silver damping), HD600 (black damping), HD545. Not pictured is my girlfriends HD650 with black mesh. All pads on the headphones are new OEM pads. I also have listening tests with a set of pads I highly recommend purchasing if you need them, and these are the Accessory House memory foam velours. They are a fantastic alternative to the OEM pads and the best I have heard yet from a 3rd party. The HD545 is a vintage Sennheiser and the predecessor to the HD580. It is the grandfather of the current HD6X0 design and its sound also proves testament to this. I’ll compare them all relative to each other first, then I’ll provide my listening notes for each category. The 650 silver vs black are quite similar, but the 650 silver actually sounds very similar to the 600 black, whereas the 650 black has slightly more bass and more recessed low and mid treble. I shall use the black 650 in this comparison to make it fairer. Bass Impact: HD650 > HD800 > HD600 = HD545 I wouldn’t call any of these bass head headphones. The HD650 digs the deepest and has a very good amount of slam, probably helped by the greater mid-bass hump. They’re all pretty close to be honest, but give the HD800 some EQ and it can hit harder than all of them. Overall Bass Quantity/Perception: HD650 > HD600 > HD545 > HD800 The sub-bass quantity within these headphones is pretty similar, but the HD800 and HD650 have slightly more than the HD600 and HD545. In overall bass quantity however, including the mid-bass, the slightly emphasised and wooly bass of the HD650 puts it ahead of the 600, which has slightly more than the rest. Bass Texture: HD800 > HD600 > HD650 = HD545 The cleanliness of the HD800 bass is noticeably better than the rest. The bass here, while not as textured as something like my LCD-3 and HE1000, is very good indeed and very planar-like in its speed. The HD600, given its slightly reduced mid bass and wooliness over the HD650, trumps it here. Surprisingly, the HD545, which also has less bass than the 650, didn’t really do better than it in this regard. Midrange Neutrality: HD650 > HD600 = HD545 > HD800 I think the HD650, closely followed by the 600 and 545, has some of the best midrange accuracy you will find in any headphone, period. Better than the LCD-4, better than the Utopia, better than the HE1000. The 650 pulls ahead of the 600 and 545 in that it is slightly less hard and emphasised in the upper midrange (at around the 3K peak). The HD800 has a somewhat artificial sounding midrange, which is actually slightly recessed. Female vocals lose their intimacy and body, but gain a lot of ‘air’ in the process here. I personally find this a slight set-back for the 800 that EQ can’t fix sufficiently. Midrange Seperation: HD800 > HD650 > HD600 = HD545 The HD800 has a significantly airer and more open midrange with fantastic separation relative to the rest. This is no doubt a result of the better soundstage and transient response, as well as the cleaner bass and lower distortion. The rest are quite similar, but I find the HD650’s smoother upper midrange to reduce acoustic masking and help give body and space to individual instruments. Midrange-Treble Transition: HD650 > HD600 > HD800 = HD545 The HD650 has an almost flawless transition into the treble. There is fantastic coherency here, marred only by a slight grain in the mid-treble that also exists on the 600 as well, albeit to a greater quantity. The HD800, whilst having great cleanliness across the board, has the infamous resonance at 6K that casts a slight ‘haze’ on tracks that trigger it, which includes almost any song with cymbals. Interestingly, I found the 545 to also have a slight emphasis in this region. I have a feeling this is a result of the plastic housing which is not as open as the metal mesh on the other headphones. Removing the back of the 545, whilst adding more treble and reducing bass, somewhat reduced this slight peak I was hearing. Treble Quantity: HD800 >> HD545 > HD600 > HD650 The HD800 has remarkably more treble across the board here. The HD545 actually has more treble than the HD600, and this is where this headphone differs from the 600 the most, as it has been really, really similar thus far. The HD650 still has excellent extension, good sparkle and nice ‘air’ above 10K, but it is definitely darker than the rest in the low and mid treble. Treble Cleanliness: HD800 > HD650 > HD600 > HD545 The HD800 is so wonderfully clean and puts a lot of other bright headphones to shame. The K812 for instance, has almost the same amount of treble from memory, and it was a hazy mess. This is similar to my previous Beyer T5p, which tried to be bright, but ended up just sounding harsh and messy. The HD650 is slightly cleaner and smoother than the 600 (this is a result of the lower treble on the 650 and some added refinement in the tuning). Again, a slight brightness and lack of refinement in the HD545 sets it apart from the 600 here. Transient Response: HD800 >> HD650 >= HD600 = HD545 The HD800 is king here, and probably against every other headphone I have heard. Transients are marvellously clean and quick. The 650 feels slightly snappier than the other two (despite a woollier bass), but it’s too close to tell and transients across the spectrum on these headphones are quite good. Soundstage Width: HD800 >> HD545 >= HD650 = HD600 No comparison in width, the HD800 has a big lead over the others. The 545, maybe as a result of the added treble and air, feels slightly wider, but again, it’s close. Soundstage Depth: HD800 > HD650 = HD600 > HD545 Again, the soundstage capabilities of the 800 shine here. The 650 and 600 do have quite a ‘tall’ stage however, and this is something I really like about these headphones as it gives acoustic instruments good depth and realism. The 545 feels slightly flatter than the rest. Again, I feel this may be a result of the plastic housing, which is more closed off. Overall Timbre and Naturalness: HD650 > HD600 > HD545 > HD800 As I said before, I really love the 650’s naturalness and timbre in the midrange and, paired with the smooth treble, it has possibly what is the most accurate tonal balances of any headphone I have heard. I want to call in the Focal Clear here, which even Tyll has said has a near perfect tonal balance. I liked the Clear, but a slight shout and tizz in the mid treble still make the 650 come on top here in this regard. The 600 and 545 are close, but the 545 loses out because of its reduced treble performance. The HD800, which can be made better with EQ, still has an unnaturalness I can’t get over. My Personal Enjoyment (Without EQ): HD650 > HD600 = HD545 >> HD800 My Personal Enjoyment (With EQ to match the Harman target as closely as possible): HD650 = HD800 > HD600 = HD545 Adding EQ to the HD800 can make it come close to a super-charged 650/600 in the bass and treble. The only issue is the midrange body and euphoria, which EQ hasn’t really fixed. Adding moderate warmth makes the 800 very honky so it is very sensitive to how you EQ the mids. I therefore love the HD800 for classical and acoustic, and equally love the 650 for electronic, jazz fusion, pop etc.