Discussion in 'Headphone Measurements' started by purr1n, Sep 1, 2016.
Has anybody ever measured the HD800 with the front protective grill removed?
I did in a different thread. The Anax mod in general has always recommended removing the dust cover.
I think he meant the driver cover. I tried that. FR gets worse (more rough). Measurements don't improve, but in terms of sound it does bring different stuff to the table. It's a little too raw or undamped for me, though.
Let me see if I can find my measurements. Not much brighter, though.
That's generally not recommended for practical reasons. We want to keep the last line of defense in there
I'm referring to the cover that's placed on top of the driver. The black plastic one.
I had a disassembled pair that was gathering dust in the closet. I put the parts together and tried with and without the cover. With the cover the treble sounds somewhat hard and gritty. Without the grill the treble was softer, yet somewhat odd, perhaps uneven. Surely, the cover introduces unwanted diffraction, but perhaps the cover also has a similar purpose to the "phase plug" in speaker drivers. Or its purpose is to diffuse the treble and upper midrange, as these frequencies are very directional and the driver is placed too close to the ear. I can only speculate, but I'm quite curious to see, in terms of measurements, what I'm actually hearing.
If you can dig out those measurements, it'd be great. Thank you!
I absolutely agree. I've already written off my pair, so I don't mind experimenting with it. You know though, unless you stuff your thumbs into the driver membranes or metallic particles get into the fold, that'd be impossible to brush off, you can't really do any damage to the driver.
So instead of taking a nap and taking 2h to post like Marvey, I just took 2 days . The main reason was that these measurements are from back in May (and April) and I didn't want to remove the driver cover again to measure. (I also have measurements from February, but couldn't find them. I tried this a few times.) So I opened the four REW files I had, saw 30 measurements (each) with weird cryptic names and then decided to put it off again. Today I took the time to decipher my measurements. Here are the results. Keep in mind that these are months old and might not be comparable to my newest measurements.
NOTE: With these measurements you will see some bass rolloff. This is because it's very hard to push the driver in all the way with the cover removed, without touching the driver. This should however not affect the midrange and treble part. The driver cover itself doesn't affect the bass.
This is what it looks like (and how to do it):
To try to keep things fair I removed the metal ring that holds the driver in place.
Frequency response on the coupler
White: HD800 with removed metal ring
Red: HD800 with removed driver protection cover
Again, the bass rolloff is from the driver not being seated perfectly. There's a slight 2kHz dip, which is probably from the outer (and inner) walls. On the coupler the treble energy gets reduced, with a big dip around 9kHz, most likely because the center hole effectively gets bigger (changing the baffle dimensions). You also get less energy >10kHz, which is probably because the ring above the voice coil acts as a waveguide to prevent destructive interference.
The protection cover does have a purpose.
CSD with the cover
CSD without the cover
It looks like the cover helps reduce two slight 12 and 15kHz resonances, but I wouldn't worry too much about this. Maybe the cover does introduce some diffraction resonances, but they're not in the audioband. Even with the cover I get very clean CSDs up to about 38kHz.
Finally, here are the old FR measurements on the head, with my mod config (2016-05)*:
You can see that I now got good bass extension, because this time around I actually listened to it. IIRC both measurements were with the SD resonator inserted upside-down. For the measurement with the removed cover I used double-sided tape to prevent it from falling out.
Generally looks a bit warmer with the cover removed. The sharp resonance just below 8kHz actually gets a bit better, too. I also had measurements without the mods, but I'm not sure how accurate they were. The CSDs do look slightly worse below 6kHz, though.
I didn't write down any notes, but I know I felt it wasn't worth it to keep the cover off. I think I actually preferred the sound with the cover on.
BTW: Here's a picture of the underside of the cover. All of the edges are rounded off. I think it looks neat.
Frequency response unmodded on the head:
White: removed metal ring
Red: removed driver cover (bad seal)
Some people have been wondering about my measurement methods and how they seem to make the HD800 look way too flat, thinking that my methods are flawed. Well, for comparison here's a FR without the mods. As you can see I couldn't get a good seal with the removed driver cover for this measurement, something that I fixed after I measured it. Might not be the best accuracy, as I feel they look not bright enough and without as much midbass hump as I hear, but generally this is what an unmodded HD800 measures like on my head. The pads do influence the measurements. I think these were pretty worn which usually have a better FR at the cost of soundstage and imaging. The 5 and 6.5kHz spikes sound worse than measured and the whole treble above 4kHz is 5db too bright.
Also, like Besnia mentioned, you get less 6-8kHz without the cover.
What you can also see is that unlike on a coupler where you get a huge 4kHz dip, you now get a small 2kHz dip and then it starts to rise again. I think there's some reasoning for the HD800 FR, at least until you get to the treble. As you can see with Tyll's measurements you tend to get a pronounced 2kHz cancellation effect when stereo speakers are playing mono material. I feel like the HD800 was voiced like two stereo speakers with a flat measuring response at the listening position playing mono material or something like that. I don't like the stock HD800 midrange.
The longer I look at the measurements, the more I realise how well the mods work.
BTW: My measurements should be comparable to Hands's. Of course there might be some minor differences around 2-4kHz and maybe a bigger difference at about 6kHz because of a different outer ear shape, but our methods are virtually identical. I've found that with headphones the in-ear measurements seem to show large differences around 6kHz. I don't think our brain compensates for this and I'm sure this explains some disagreements. Some people may always find the HD800 to sound bright, no matter what mods they use, while others (like me) will find the HD650 to sound rolled off, for example.
*For those wondering what the wiggly stuff between 1 and 4kHz is with these measurements, those are reflections from my room. The HD800 is pretty open at those frequencies and isn't very directional, This depends a lot on where you turn your head. I do think you can hear your room with open headphones, but it's not a big deal.
Great job! Thank you for taking the time and effort to do this. I am trying to correlate your measurements with what I'm hearing and I can, to a great extent. I cut out a ring of plastic with the same thickness as the side of the plastic cover, so that I could compare with (somewhat) proper seal. Obviously, I couldn't A/B very quickly, but spent more than a few hours yesterday, trying to figure out what's going on. I took some notes and here are my subject impressions. Overall, the headphone sounds warmer and more polite w/o the cover. It's quite tricky to read into FR measurements, but contrary to what the measurements indicate, I do believe that w/o the cover there's better transition from upper mids to low treble. To my ears, they just blend properly now, subjectively. And the typically piercy/metallic sounding 6-8khz region feels a lot less pronounced than the measurements suggest (I do have an improvised @sorrodje resonator inside the gap). The downside, however, is that w/o the cover the upper treble becomes subdued and uneven, and that's quite noticable. Without a doubt, at least in my mind, your measurements have proven that the cover underside spiky ring does effectively tackle treble interference. These two 10db spikes above 14khz, I could barely notice the first one running white noise. However, this is probably due to my own hearing (not what it used to be) and the fact my output transformers have a steep rolloff starting at 16khz (measured).
Eventually, I decided that I prefer the overall sound w/o the cover, probably because all my dacs and amps lean towards the bright side. I DO feel there's a touch of extra clarity and depth throughout the mids and treble when the cover is removed that the measurements don't reveal, even though the upper treble is subdued. However, I admit it's incredibly hard to spot small differences in sound clarity, when the tonality is different, so there's a pretty good chance I may be fooling myself.
Cudos for your work. Would be interesting if you could share a little bit more of your subjective impressions, since you have a different audio chain.
Oops, I tend to make a bad habit of not mentioning that you will see these sort of spikes in the measurements on the head. Those are just ear-resonances and aren't heard with music in my opinion. You won't get quite the same sharp spikes with speakers where the drivers aren't coupled in a very close space to the ears, but I also don't think that you should focus on completely getting rid of all of them, since that will most likely make it sound overdamped. The measurement method (omni mic at ear canal opening, ear canal completely blocked) also isn't perfectly representative of these resonances.
As for the subjective impressions, honestly it's been so long since I last tried it that I don't remember all that much about it. More clarity? I think you're probably right. I'm sure you could achieve that by only peeling off the protective screen, though. And to be honest I didn't notice it getting much warmer, contrary to what my in-ear measurements showed. I think I mainly felt that the treble was less even.
Did you leave the metal ring on, or did you compare both with a cardboard ring? I feel the metal ring is responsible for a lot of the metallic sound.
I do generally think that less stuff infront of the driver is generally better, unless you're dealing with a facetweeter that needs toilet paper treatment, but there's a balance you have to strike. I always feel damping affects transient handling. The modded HD800 for me hits a sweet spot where it doesn't sound overdamped, but also doesn't sound too in your face. In comparison I feel the HD600 has a much more polite transient handling (something that I don't like), despite being similar levels of brightness. Maybe removing the silver mesh covering half of the driver could help in that case, but that'd probably mess up the tonality. I think I remember removing the cover with the HD800 to make it sound slightly too underdamped to me.
BTW: I'll update the above post with what the measurement looked like without the mods on the head. I believe this is without the ring, so the same as the coupler measurements. Those do show less of a 6-7kHz spike with the removed cover. The longer I look at the graphs, the more I realise how well the mods work.
We really need to organize a meet in Germany sometime soon
Interesting stuff, good to know. I was going to ask if these spikes were due to measurement issues, but decided it was probably my hearing
By getting warm, I didn't mean the FR was getting tilted overall toward the lower end of the spectrum. I feel that w/o the cover the upper midrange energy and moreso the treble was reduced, resulting in a more soft, polite sound, without becoming mushy at all. I did keep the metal ring as I wanted to make sure I was getitng a good seal. However, I didn't screw the bolts very tightly, so not sure if I was getting the exact same seal every time. Yes, the metal ring brings some metallic coloration and lifts the treble a bit, but my ring is covered in cork.
We're in perfect accord on this. Anything placed in front of the driver is bad in my view. Rigid materials introduce noise/distortion, soft materials, like cloth or foam, reduce the subjective speed and immediacy of the sound, or as you refer to it the transients. Most people don't agree, but the latter isn't dependant on FR. I've tried with a stronger magnet on the HD650 (stronger > FR tilted more towards the upper frequencies). With the bass, it's simple, but when the waves get shorter and more directional, things get quite complicated. A foam, for example, reduces the energy, shifts the phase, as different frequencies interact to a greater or lesser extent with the barrier, and sort of meshes different frequencies together. Don't ask me about the physics behind it. This is a topic that I had discussed with MJK years ago, and it's mind boggling to me. The effects are small, most people can't discern the difference, but they are noticable. And it seems you have come to the same conclusion.
Seems to me the HD800 uses a heavily machanically damped driver with high resonance. If you change the acoustic impedance on one side of the driver, you'll have to adjust on the other side accordingly. Otherwise, it will become either unpleasantly boomy at 100hz or way too damped. The driver membrane is glued directly to the frame. What allows for some limited pistonic movement are the notches on the membrane, but that introduces tangental movement as well, and in turn increased distortion, the harder you push it. HD650 driver is even worse, as the dome twitches and it's very soft. I tried covering it in a thin film of epoxy, but the weight of the film relative to the overall weight of the membrane is too much. I lost roughly around 12db of efficiency and even though the clarity in the upper mids and treble improved substantially, the lower mids and particularly mid base sound way too loose and overpowering, regardless of how much I damped the enclosure. In short, another failed experiment.
In my experience, removing the mesh on the driver does make a huge diffrence. And it does change the tonality, but I don't think you will personally like it I can't stand that mesh, because the midrange sounds like two drivers with different characteristics meshed together. If you remove the mesh though, you'll have to cover the baffle holes with a layer of paper or layers of tensioned cheesecloth, or something else. The goal is to get the lower mid-range and base in line with the upper frequencies w/o overdoing it. I eventually moved in the opposite direction. Covered the baffle in rubberized cork, made a 8 tiny vent holes and damped the back of the driver a little bit. I like the tonality, but it certainly isn't everyone's cup of tea. It does sound a lot like a closed headphone, but the clarity is substantially improved, compared to the vanilla HD650. Btw, nowadays a pair of replacement drivers cost 100 euros, including the cans, so it's not very expensive, if you just want to scratch your itch and experiment
Thanks for adding the measurement for the unmoded headphone. It's great how much progress has been made by this community alone, isn't it?
I'm not saying I agree with you, but here's FR of my full range drivers in backfiring horns... there's some resemblance to HD800, hmm Yet, they sound vastly different.
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