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Pioneer HDJ-2000 bass boost/extension mod

post #1 of 55
Thread Starter 

While I really like the HDJ-2000, comparing it with other DJ style cans you can notice a bass rolloff that starts off a little sooner than the others. When playing heavy bass sounds, I could feel vibrations emanating from the cup and into the first arm segment. Going by the age old audio mantra of "vibrations are bad", I decided to try some damping.


Without damping, the rolloff is noticeable around 70Hz or so, then sloping down and dropping out around 40Hz. Adding a little bit of damping inside alleviates this remarkably well, pulling the rolloff point down slightly to maybe 60Hz but maintaining a much flatter slope down to about 30Hz after which it drops very quickly. Overall, the bass feels *much* more powerful; maybe even verging on too much for my tastes (but I'm only a moderate basshead). I was also pleasantly surprised to discover that the headphones did not become any less sensitive (contrary to my other damping experiments). If anything, they actually feel louder because the bass presence is improved. 




Materials needed: 

phillips screwdriver

poster putty, or plumber's putty will do ($1 from dollar store, or $3 from hardware store)

some felt and scissors 

foam or gauze optional (from your mom or gf's craft/sewing closet)

micropore/medical tape optional (I got some from a Walmart pharmacy near the bandages; you can get gauze here too)


This took me about 30 minutes in total, and negligible materials cost. (like $1 worth of materials, if that)




1. Remove pads - just pull gently on one side and it'll slide off



Hard to see in the pic, but there are three screws there. Take them out and very gently open up the cup; be mindful not to yank the wires since they're rather short here.



2. Next, stuff some putty into the two crevices around the hinge. I figured this was the problem area generating resonance/vibration. In the ortho thread you see guys that also slather putty all across the surface to mass damp, but I want to keep these headphones light. I also stuck some micropore tape over the hinge assembly area, though I doubt it actually makes a difference (fuzzy reasoning is that I don't want a hard reflective surface directly behind the driver); Don't put any thick foam there as it will impede into the driver.

2.1. There's a row of small bass ports (4 of them) between the crevices on the top side of the cup (normally the hinge will obscure them from view). You can experiment with covering them. I covered all 4 with a piece of micropore tape (see step 5 below)




3. Next I cut out a round piece of thin felt (use the earpad as a quick guide and trim later if you don't want to measure). Poked holes into it with the scissors (and widened them with the screwdriver) to match the mounting holes, and also cut a slit to allow for the wire. Note that this is the right earcup. The left earcup has a few more wires and a small board for the mono switch; the only difference for you is you have to cut another slit into the felt to accommodate the board. 

edit: 3.1 actually I changed this and replaced the felt with fuzzy light breathable velour, and put the felt in front of the driver under the pad. This levels out the bass hump and makes it more consistent.





4. Put it all back together and you're done. Optionally, I rolled up a piece of gauze and stuck it under the earpads like so (not the prettiest I'll admit):

edit: 4.1 take the felt from 3 and place it under the pad. Easiest way is to slip it under the lip of the pad, then from there secure the pad to the baffle as normal


This does increase bass and reduces isolation a tiny bit, and improves treble clarity (by giving space for the front vents to breathe under the pad), but also blurs the line a bit between bass into midbass. I do it primarily for comfort because I have an unusually wide noggin and the headband actually presses on my temples (I have this problem with all headphones with a headband that curves with the head), so the thicker earpad gives me the clearance I need.


5. Here's a pic with a piece of micropore tape over the vents. I later put this on the inside because it's rather ugly on the outside (though usually hidden behind the arm. It sharpens up the upper mids (around the female vocal range), improves isolation just a tiny tiny smidge, and also reduces wind whistling noises if you wear these outside. 



6. I took a piece of blutak (about half a strip) and rolled it into a thin line approx 15cm long, then laid it into the crevice surrounding the driver. This is essentially mass loading the front plate on a very small scale. Covered it with some tape because I didn't want the blutak sticking to the earpads. Hard to say with certainty if there was improvement here, but I think the lower bass extension and distortion improved ever so slightly, and the bass kicks feels stronger when amped. It could entirely be placebo though.







step 7




I found some roofing repair material in the garage. I don't know the exact name of the stuff, but it's probably some variant of "peel 'n seal". Anyhow, this kind of stuff has been used as a cheap alternative for vibration damping in cars (the thicker variety of course). I think it's an asphalt based adhesive with a plastic/rubber backing. Just peel the paper off and stick it on. The thin stuff I've got seems just right for headphones. Therefore...






Cutting this stuff was actually rather difficult. The material itself isn't hard to get through, but it sticks to your scissors and makes a mess of things. You have to be careful it doesn't bunch up behind the scissors and pull itself back into the blade as you're cutting.


So anyhow, I cut a ring out and applied it around the edge of the baffle front. 


Sound impressions? Bass is cleaner, but yikes I think it got louder too. 


If you've got dynamat or other vibration dampener, I'd suggest using that instead. 






step 8:

Added some plumber's putty around the outer edge of the baffle to seal it with the cup (sorry, I forgot to take pics). This improved bass extension and actually just cleaned up bass definition overall


step 9:

Some pieces of dynamat/fatmat on the rear of the driver (do not cover the holes). Slight improvement to bass detail, treble detail moreso.

Edited by Armaegis - 5/21/12 at 9:41am
post #2 of 55

I knew it would only be a matter of time before you opened up those Pioneer's. Tell me did the mod cause the mids to feel recessed or sacrifice detail?

post #3 of 55
Thread Starter 

As far as i can tell the mids are unaffected. I did one cup at a time and listened back and forth with music and test tones. The only really noticeable difference I could pick out was the bass became stronger. It might even be my imagination, but it felt like the entire spectrum got louder. I was actually kinda hoping for the opposite, as I like the sensitivity of headphones to be a little lower so I get a more useable range on my volume pot.


I generally consider the highs to be where people hear "detail" and in that regards that Pioneers are no different, and admittedly might be considered a weak point. In my experience, headphones only ever get two out of three of the ranges (bass, mids, highs) "right", and note here that achieving technical competency and sounding right are different things to me.


One of my favourite test points is Metallica's Enter Sandman about halfway through there's a whispered "off to Never-never-land" at the end of a phrase. The cymbals and hushed vocals come across super clear on your DT1350, but then they lack that hard driving thump of a bass line that brought us up to that point. The HDJ-2000 drives hard and gets your heart pumping with the beat, and you get the quiet part for the vocal refrain, but you almost miss the whisper.

Edited by Armaegis - 9/9/11 at 8:50am
post #4 of 55
Thread Starter 

Well I'll be darned, micropore over the bass vents makes a difference... in the midrange. It brings out that "neverneverland" whisper just a touch better, and female vocals up a tiny bit.

post #5 of 55
Thread Starter 

Haha, an unintended benefit to putting tape over the bass vents is that the whistling sound from wind while walking outside has been decreased (probably because, well, now there aren't holes for wind to whistle across).

post #6 of 55

You're really having fun with this mod aren't you lol.

post #7 of 55
Thread Starter 

I haven't done much to it other than adding the micropore tape over the vents. If I were to tune a bit more I would actually want to reduce the bass a bit; maybe a thinner felt or smaller disc. There are also front vents on the driver that are sorta ultrasone in flavour that could potentially be experimented with. Hmm...


You should give these a try sometime. They might give your XB700 a run for its money!

Edited by Armaegis - 9/14/11 at 9:48am
post #8 of 55
Thread Starter 

Added pic 5 with tape over the vents.

post #9 of 55

Doesn't tape over the vents ruin the soundstage though? It has for all headphones with vents I've tried. The vents usually improve both bass response and soundstage.

post #10 of 55
Thread Starter 

I sat there for a while peeling tape on and off, 2 vs 4 vents covered, one side with and other without, etc, and the only difference I could note was the slightly better isolation (more noticeable against outside wind noise) and marginally better midhighs that were so slight it could have been placebo. I tried some of my binaural tracks and really couldn't tell any difference in soundstage.


Mind you, micropore tape is highly breathable. It has a strong effect right behind an ortho driver, but for a regular driver I think by the time the pressure backwave wave moves through the felt in the cup it doesn't have any significant effect in terms of venting.

post #11 of 55
Thread Starter 

Added a tiny bit more blutak today. I forgot to take a picture, but if you look at the third picture above, on the baffle surrounding the driver, two thirds of the surrounding ring are open with a paper filter. I filled the remaining third with blutak. The only hiccup here was the left cup where the board for the monoswitch actually resides in that area, so when seating the baffle back into the cup I had to very carefully press it back in since the blutak was essentially molding around the board. Don't think I'll be opening these back up anytime soon.


I didn't compare back to back, but I think it improved the bass clarity a tiny bit.

post #12 of 55
Thread Starter 

Note to self for future modding projects: put micropore tape over the blutak... felt that gets mashed into the putty is messy stuff and makes life difficult

post #13 of 55

Nice work chap. I have had quite a few pairs of the HDJ-2000 apart and often thought it strange they did not have any damping material inside especially at the price they are. I will have to have a fiddle around myself when I have some spare time.

post #14 of 55
Thread Starter 

Just to prove that I couldn't leave well enough alone... I thought to myself, "well gee if I don't want to open it up anymore, what can I do to the outside?"...


So I added another thin ring of blutak for mass loading. Any change? A tiny bit improvement in the lows around 40Hz which I think was more a slight reduction in distortion rather than improvement in sound. Bass kick is stronger when amped as well. Pics will be added to the first post in just a minute.


I wish I had some proper damping material like dynamat or something to properly mass load. 


Ideally, I would mass load the front baffle with a vibration damper like dynamat or some other butyl + constraining layer absorber. Then line the rear of the baffle with an acoustic foam if necessary, though the floating disk of felt may be enough as I don't think there's a huge amount of backwave there that needs to be tamed.

Edited by Armaegis - 10/7/11 at 1:33pm
post #15 of 55

I wish I had some proper damping material like dynamat or something to properly mass load. 

I have ordered too much so will send some out when I send the other goodies next week ;)

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