An all time favourite made its way here: the HD6XX that is based on the legendary HD650, once Sennheiser’s flagship headphone before the HD800 came out.
When you read a review of the HD6XX/600/650, read it as a review not of the headphones but of the reviewer. There are already way too many reviews and measurements of these on the internet.The popularity of the 6XX series, plus excellent quality control and consistency in manufacturing at Sennheiser can serve as a litmus test: if you share the same sound preference with the reviewer.
So that is the main purpose of this review. With that out of the way let’s pull up the graph:
Tonality: Exemplary vocal reproduction and overall balance. The 6XX series have been the gold reference for a good reason. Mids are life-like and effortlessly smooth. Highs are slightly tuned down to offer a more relaxed listening, as can be seen from the scoop between 7-9khz and also 10khz onwards till 15khz. There’s still sufficient energy there to make instruments sound realistic though. Cymbal attacks may be less aggressive than recorded but not to the point where it is dull or dim. Extra air at the top above 15khz certainly also helps. Bass is arguably the only drawback: it is audibly rolled off so you don’t get the planar bass that extends all the way to 20hz. There’s also some added mid-bass between 100-300hz, resulting in what some may call ‘warmth’ or ‘Sennheiser veil’. Still, the overall presentation is life-like albeit in a slightly less aggressive way.
Technicality (see this as qualities that may not be directly reflected in FR): Decent performer. There’s no serious flaws: resolution is ok although a bit blunted by the mid-bass hump and relatively toned down mid-treble; dynamics are generally ok but smaller driver size comparing to flagships plus the bass roll-off won’t give you the most slam. Soundstage many have said to be a weak point and I can see why. It is not claustrophobic, as there is decent front imaging and sufficient depth between front and back instruments. The real weakness is left and right imaging which are very close up. I guess this is why some people say there is a ‘three-blob effect’. Even then the HD6XX offers an excellent price-to-performance package at the asking price, so there’s no complaint.
Here we don’t stop at the default configuration. Let’s try some simple mods and see how they change the sound. I don’t have other pads at hand but will hunt for some and update when they arrive. For now, let’s tinker with the chasis and damping scheme.
First, the back grill was removed:
There’s little difference. You lose a hair amount of bass possibly due to absence of back reflection but it’s very minor (less than 1db). Treble smoothes out a bit as shown by the dip at 4k and 7khz, both of about 1db.
Some may wonder if there would be differences in the time domain (let’s set aside the debate of headphone as mininum phase deivce for now). So I measured Cumulative Spectral Decay (CSD):
Again the differences are marginal. Decay may be ever so slightly faster without the back grill but the differences are within run-to-run measurement error (I have selected the runs with fastest decay for each cases). Overall the HD6XX does not display any issues in resonances or lingering.
P.S. also measured THD and impulse response, no meaningful differences.
Next, I tried removing the damping foam in front of the driver (between the ear and the driver). It is quite thick and some claim that removing it gives you more treble. Let’s measure to find out:
Indeed, there is more treble almost across the board. Differences in treble extension can go up to 7db at 12khz. So there should be clearly audible differences. I didn’t try listening to them without the foam cause that would risk damaging the driver as there is no longer anything between my ear/hair and the driver. Maybe I can find something thinner/more acoustically permeable and try that.
On the down side, there’s now quite a bit less bass. These are not bass heavy cans to begin with, so that is really a trade off you need to make if you want extra treble.
Measurement of several alternative pad options:
These are some of the generic HD6 series pads that you can find on the Taobao/Aliexpress. Honestly, they don’t really hold up well against the stock pads in terms of sound quality. The velour ones, while the material and made are both quite similar to the stock pads, unfortunately dull the treble. This is likely due to the use of high-density memory foam.
I have a few suggestions for pads:
1. ZMF HD600 pads (all 3)
2. standard velour pads from Taobao/aliexpress (budget)
Seeing the measurements of those and getting your feedback would be great 🙂
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Hi there. Yeah, I’ve thought about the ZMF HD600 pads. Zach’s already shared some measurements with the 5128, so I wasn’t sure if it was necessary to do my own. Might still check them out later at some point, though.
Regarding the Taobao/Aliexpress budget pads, I’ve tried a few, and honestly, they didn’t really hold up well against the stock pads in terms of sound. I have yet to find one that could match the stock pads.
I did some measurements on an older rig, but since they weren’t great, I haven’t bothered with the 43AG. Also, I don’t have the HD6XX anymore, but I might be able to test them on an HD580 Precision if that helps.
I have updated the pad measurements from the legacy rig at the end of this article.
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I have the exact Chinese pad from DIYAUDIOHEAVEN’s website. Everything from his picture looks identical to my unit. Even the sound impressions are extremely similar
To me, the chinese clones are slightly warmer and smooth sounding than stock. transients are slightly smoothed out while stock sounds slightly sharper. In short, stock pads are slightly sharper and clearer sounding.
Based on DIYAUDIOHEAVEN’s measurements, the chinese clones sound close to a worn HD6X0 pad.
Not sure if you have these pads but feel free to check them out!
Ctrl+F and search for:
“I also had some worn (almost 30 years old) original HD650 pads lying around and a cheap Chinese knock-off bought from Ali-Express.”
to get to the exact part I was referring to.
https://diyaudioheaven.wordpress.com/headphones/earpads/
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Thanks for pointing that out – I checked again this morning, and it turns out the Taobao velour pads I measured are indeed the ones you’re talking about, or at least they look the same. Your description matches my impression too.
The main difference is the creasing pattern of the protein leather at the back, something the stock pads don’t have. I’ll keep an eye out for other options on Taobao/Aliexpress. I hope to find one that’s identical to stock.
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Yes you are right. The creasing pattern of the protein leather at the back.
all in all, decent for the price but not the best. I will definitely be picking up the ZMF perforrated suede in the near future
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Is it possible for you to upload the measurements of the chinese pads on your Squig.link?
on either the hd600 or hd6xx is fine. Thank you so much
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Ah, those measurements were taken with the old system. I can redo them on the HD580 Precision if that’s useful to you. I might pick up another HD600 down the line, and I’m also considering the ZMF Suede pads.
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I removed the foam pads in front of the driver and installed thin piece of ladies stockings. The sound is a touch brighter and more neutral. I tried the same with 58X but while it brighten them a little, for some reason they also became fatiguing and somewhat unnatural (possibly the pesky 5kHz peak was too exaggerated).
As for pads, since 2021 the OEM pads are a bit different than the ones used since the introduction of HD580. There is definite chance in sound: brighter, less midbass hump, maybe a bit less smooth. The new pads are a touch stiffer and hopefully won’t compress with time as the old style ones.
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Hey mate, interesting – that’s something I might try myself. Yeah, I’ve always found the HD6XX/650, and even the 58X, to lean a bit on the darker, slightly veiled side, which is why I usually prefer the HD600 for most genres.
For the 58X specifically, I measured them with the damping removed and noticed that the 5–9kHz region becomes more prominent. The overall tonal balance shifts since the reduced midbass allows more treble energy to ‘cut through’, which might explain why they started sounding more fatiguing.
I did notice the changes in the newer OEM pads as well, but I haven’t had the chance to measure them properly on my rig yet since I don’t have another pair of 6XX on hand.
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