I just recently finished modding my hd650 based on zoNt0's instruction and help (from a month ago).
First I removed the back foam on impulse. Then I did a little readings for a day and a half regarding how people feels about each modifications (rear foam removal, front foam hole, and mass dampening). The sound was airier with just rear foam removed. The midbass, if my memory was correct, felt punchier as well. One thing to note, removing the rear foam made the sound exuberant.
This may be good and bad, depending on how one feel about their hd650. Removal of back foam mod, I feel, made the hd650 loses it's envelopingly warm sound.
Then I made the coin-sized hole on the front foam I think 2 days after that, also on impulse. I immediately noticed the coin-sized mod made the hd650 has louder high frequencies. If back foam removal increases the midbass, I felt like coin-sized hole brings back the balance by adding some clarity so the balance in sound was there.
Problem is, I feel that it's peaky in some specific frequencies where my ears happened to apparently can't exactly tolerate the sound when I listen to them for some time.
Then I ordered a mass dampening material (I chose Second Skin based on Zonto's advice). While waiting for the mass dampener to arrive, I did a lot of mod readings in the meantime while also brain-adjusting to the sound of the hd650-mod.
I've had the rear removal+coin modded-hd650 for several weeks, while waiting for the dampener to arrive. To me, the r+c modded-hd650 is vibrant, airier, and the details from songs was retrieved noticeably louder than stock, background sounds are louder.
The sound however, is peaky in some specific frequencies somewhere around the upper midrange/lower treble region. Listening to the r+c modded-hd650 gave me listening fatigue. A bit of a context about me, I liked grado and I rarely feels fatigue listening to them. I think if I were to describe it, I feel like there is a wave of sounds that just hits my ears and gave me fatigue.
The dampener arrived on October 10th. I put the mass dampener on the hd650. I'm not a DIY-er / modder, so I didn't exactly get the idea behind putting things on a housing. I had my skepticism about this mod. In my mind, when the product arrived, it just looked like fancy blu-tacks to me. What's a fancy blu-tacks being tacked on the chambers got to do with a headphone, I thought. I put the dampener on because why not. It was $33 in my case so, might as well.
Went a bit on a tangent there but I would like to say that mass dampener did make a notable difference in the sound. In terms of how big the sound changes are, the back foam removal is the singular mod that changes the sound in the most noticeable way. However, the mass dampener mod I feel is the one mod that is the most notable for the hd650, both from sound and practical perspective.
The change in sound is not as big as rear foam removal, but mass dampener mod can be done in isolation without adding new problems that wasn't there before.
What mass dampener does to the hd650 sound is tightens up the bass. That's the most noticeable part. I wouldn't call it a big difference, but I think it's immediately apparent and noticeable.
So after I did the dampener mod, what I read regarding dampener and what made them able to modify sound clicked in my head. I read the explanations beforehand, but most of it went over my head because I'm a dumbass.
Let's see if I get the theory right. Feel free to correct me when I'm wrong.
So there is a driver. Driver vibrates. Housing holds driver. Housing also vibrates. Dampener is heavy. Dampener adds weights to housing. Housing stabilizes. Housing vibrates less. Bass tightens. Less distortion.
That's how I understand it in my mind.
Now a bit of a good news. The sound wave issue I felt with rear-foam removal decreases from adding the dampener. Unfortunately the decrease is not significant enough and is a subtle decrease.
The one modification I haven't done yet as of the above point was rear spider cage removal. I didn't want to do it as that mod was irreversible and unless I'm well-informed about them, I decided to put it on hold and consider not even doing it at all.
Now at this point in time, I listened to the r+c+d-hd650 probably for close to a week, and I somewhat noticed that I got less fatigue from the sound wave attack. All the while, I was reading all that I can read about spider cage removal and people's comments about them.
I don't think I ever came to a point where I was sure and then decided that removing spider cage was a good idea.
I just happened to do it because well, impulse. That was yesterday.
Now I've been listening to the hd650 non-stop ever since I started typing this post and I didn't feel any fatigue from listening to the spider-removed hd650. Everything felt fine to me so far. I haven't noticed sonic wave attack out of the ordinary in this particular listening session. I know exactly when the sonic wave attack happened because to me, it felt like my inner ear got Sonic Boom'd by Guile. It was not subtle to me.
What spider cage removal does, is that it basically eliminates (or dramatically reduced) the sense of glare / treble issues / sonic attack from having no rear foam at that place.
So, conclusion time and some odd tidbits.
For beginners that are considering modding their hd650, these are the lessons I learned from my experience:
1) I would have done the mass dampener mod first.
- Regardless of skepticism, it's a reversible mod and so, there is little harm on doing it and doing it first were you set to try modifications.
2) Get proper / good enough tools to do the modifications.
- A cutting mat : is not expensive and would have saved me some time were I to have it the day I cut the front foam.
- Have a pen knife on-hand for the front foam : It's easier to use than cutter. Besides, you really don't want to make your coin-sized hole too big. Pen knife may have more accurate handles than cutters.
- Pick up the mass dampeners remnants from your floors immediately : Or else your floor might have some spots from the adhesives if you left it on the floor and you happened to step on them.
- Have a tweezers : If you don't have one, as using tweezers is the easiest way to remove the rear foam. Tweezers is better than screwdrivers or dental floss toothpicks.
*I used "side-cutter pliers for plastic" to remove the spider cage. Mine was too big, I would have used something else were I to do it again. Something smaller. The spider cage is not tough (leaning towards the fragile side) so after the fact, I feel like it can be broken / cut by a lot of things. Not necessarily have to be "big side-cutter pliers for plastic" that I used.
**Reason why I would've used something smaller is because you have to cut the spider-cage on the upside down position, and my pliers twice or thrice got attached to the magnet near the spider cage, and to be honest it kinda freaked me out a bit / moderately.
My hd650 sounds fine now so that's good. Worst case scenario I'll just get a new driver if it breaks (hoping it's nothing and fine though. Seems fine now so far).
3a) I would do the coin-sized mod after the dynamat, because it's semi-reversible by buying the foam / earpads part.
3b) Prepare to mess up your coin-sized mod size. So make smaller circles. instead.
- I read that people used quarter dollar coin for their coin-sized mod. I learned that quarter dollar is 2.42 cm. I used a 1 yen coin that is 2 cm diameter. I still ended up with hole that was a bit bigger than the driver hole (not using cutting pad and pen knife, but cutter and cardboard). So prepare to mess up your foam and... order the foam / earpads depending where you live.
4) Do not do the rear foam removal until you are somewhat well-informed with it's plus and minuses.
5) Do not do the rear foam removal.
6) Are you willing to irreversibly mess with your hd650? Then do the foam removal + spider cage at the same time.
- From my experience, I don't think foam removal in itself is a good mod. It messed up as much as it adds. The "addition" itself, is not so much a net positive as it is a trade-offs between A and B. As in, you get airier sound at the expense of the hd650 sound.
- The foam removal sound change is definitely noticeable.
- It also adds what I call a sonic boom problem that is cured by spider cage removal and that, is non-reversible. You can't buy just the housing either, they sell it as one part (as the driver part), I think.
7) Do I think hd650 mod worth it? The dynamat is I think. The rest I would say is subjective. I feel like the better one's amplifiers are, the more subjective the mods becomes.
I have a baseless thought that the weaker somebody's amps are / the less well-designed their amps are / the less synergy the amps has with the hd650, the more the dynamat mod worth it, as it tightens up the bass noticeably, for people in this hobby.
I can live with either of them, the hd650 stock or hd650 mod. Which is why I didn't do the spider cage removal until the very end, in hopes that I can reverse the foam removal should I want to, one day or some .days. However, it turned out that rear foam removal in itself is not a good mod for me, spider cage is a necessity (ymmv and all that).
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Well that was long. This is probably my longest post on head-fi, lol.
