JVC HA-RX900 modifications, a picture tutorial. (56k, forget about it...)

[iaTa]

I was going to ask about those lenses and why you didn't remove them completely but I assumed there would be a good reason, especially being that I'm a bit of a newb at all this

[jaudio]

Originally Posted by TopPop

I guess the lens made sense to me, in that the idea (I figured) was to balance the frequency response by having many different sized holes (and thus, difference degrees of airflow, and wave propagation). But it also makes sense to simply have greater overall airflow, too. I'll have to try it one of these days, very soon.

I wonder why JVC has incorporated these? They give very little information on what they actually do.

It suppose to work like"bose direct reflect" from 80's, It was designed to widen the soundstage. If i remember correctly it had a single turnable piece of metal in front of the tweeter.

This is the only picture I could find
http://cgi.ebay.com/1980-Bose-301-Di...ayphotohosting

[micmacmo]

Long story long, I'm expecting a set of RX900s shortly that I plan on modding. I got curious about Dynamat and what it does. Primarily, it's intended to dampen or deaden unwanted resonant vibrations in the sheet-metal panels of cars, making for a better acoustic environment. It does the same in the plastic housings of headphones. There are a range of similar products, all of which are generically called sound deadeners. It's all explained at this site:
Sound Deadener Showdown

According to the site, these deadeners:
# Add mass to (the housing) to move resonance out of the audible range
# Reduce vibration through viscoelastic damping

So sound deadeners really are intended to be heavy. That's why they work (and weigh down your headphones). But manufacturers can offset the need for weight by using an adhesive that dampens the vibrations by being rubbery.

Now, back to Dynamat. Original Dynamat is largely asphalt (hence its weight). Dynamat Xtreme is primarily a butyl-based compound which is lighter than Original but is supposed to be better at dampening.

According to the Dynamat website: "Dynamat Xtreme damps four times better than Dynamat Original and weighs at least 50% less."

Trivia: Some folks have used asphalt-based roofing materials called Peal 'n' Seal and Jiffy Seal as cheap alternatives to high-cost sound deadeners in their cars. Oh, And the asphalt-based ones can stink like hot asphalt (go figure) if they get too hot.

[Alai]

Wow. Great research. Definitely grabbing Dynamat Extreme after my wallet recovers from my recent splurge on amps and dacs.

Originally Posted by micmacmo

Long story long, I'm expecting a set of RX900s shortly that I plan on modding. I got curious about Dynamat and what it does. Primarily, it's intended to dampen or deaden unwanted resonant vibrations in the sheet-metal panels of cars, making for a better acoustic environment. It does the same in the plastic housings of headphones. There are a range of similar products, all of which are generically called sound deadeners. It's all explained at this site:
Sound Deadener Showdown

According to the site, these deadeners:
# Add mass to (the housing) to move resonance out of the audible range
# Reduce vibration through viscoelastic damping

So sound deadeners really are intended to be heavy. That's why they work (and weigh down your headphones). But manufacturers can offset the need for weight by using an adhesive that dampens the vibrations by being rubbery.

Now, back to Dynamat. Original Dynamat is largely asphalt (hence its weight). Dynamat Xtreme is primarily a butyl-based compound which is lighter than Original but is supposed to be better at dampening.

According to the Dynamat website: "Dynamat Xtreme damps four times better than Dynamat Original and weighs at least 50% less."

Trivia: Some folks have used asphalt-based roofing materials called Peal 'n' Seal and Jiffy Seal as cheap alternatives to high-cost sound deadeners in their cars. Oh, And the asphalt-based ones can stink like hot asphalt (go figure) if they get too hot.

[Diesp]

Great job TopPop !
Looking at your pictures, you made me wonder if we could buy RX900 replacment pads & if they would fit on ATH-A900 cause they look better than stock ones.
I should have tried this before buying W5000 ones

[goober-george]

Is the acoustic lens supposed to come of easily? It almost seems like its glued to the felt. *update* Weird the when I unscrewed the other side it just came off, the left side I had to carefully pull off. I'm going to compare how it sounds with the acoustic lens off and on. So far it seems the highs are a bit more extended with just the felt off.

[micmacmo]

Thanks for the great instructions, TopPop. In my case, I applied a butyl-based sound deadener (B-Quite Ultimate) just to the back of the cups and the back of the drivers. I very lightly stuffed the cups with generic fiberfill (I could easily see the back of the cups through the fiberfill).

As for the acoustic lens, I just removed the easily peeled-off felt. At least at first. Because when I replaced the perforated plastic, I found that it buzzed without the felt beneath it, so I removed it too. (I didn't punch holes through the felt that remained on the housing.)

Frankly, I think that the so-called acoustic lens is actually the felt, not the plastic. Removing the plastic had very little effect on the sound (aside from getting rid of the buzz) but removing the felt really changed the sound.

Sound quality
Overall, making the modifications was time (and a few pennies) well spent. I was surprised by the difference they made. The bass is largely tamed, particularly the hump around 250Hz (as mentioned by TopPop). It now has real presence without bloat. I listened to Rob Wasserman's Duets disc and his bass playing with a bow had real depth and growl.

After a few hours of listening, I thought the highs and mids remained a tad foggy after the modification. Plus, the treble seemed to roll off without much extension. But then I did an A/B comparison between the mod'ed RX900 and my q-jays using a couple songs that included cymbals, triangles and chimes. I'd expected that the q-jays would render the high frequencies with more energy than the RX900. Not so. The sizzle and ringing qualities of these instruments were more audible with the RX900 and the sound didn't decay as quickly.

So, I think what was affecting or coloring my initial impressions is 1) the fact that the mids are still a tad muddy 2) the bass remains louder and dominates the treble and 3) my limited experience with phones that have a lot of bass kick. My collection is primarily limited to iems (ER6i and q-jays) and speakers (aging but beloved Celestion 3s) that are better known for their treble response.

The modification doesn't undermine the soundstage to my ears. In fact, maybe the opposite. The kick drum, for instance, no longer sounds like it's right in front of me while the cymbal is at the back of the stage. Now they sound like they're part of the same drum kit.

Before the modification, I thought "these are quite good but I wish that..." Now I listen to them and focus on the pluses, not the negatives, and just generally enjoy the music.

Head position
I've found that the position of the phones can have a huge effect on the sound. Moving the phones forward on my head (so my lobes touch the back of the pads) gives the best soundstage and most prominent bass. Moving them back has the opposite effect. Somewhere in-between works best for me.

[TopPop]

^Fantastic addition! Thanks so much!

I really concur with everything that you said here. However, I feel that there is a slight difference to be had when the acoustic lens is removed. The overall sound is a bit more forward and aggressive (not in a bad way!) with the plastic off, I think. More like my Alessandros in this way. However, it seems that the soundstage is a bit restricted. Eventually, I ended up putting them back on, because I already have some "aggressive" phones, and I like the laid back nature, and slightly wider soundstage, with the lenses on.

And you're spot on with the head position thing. Same thing I've found for the same positions you mentioned.

[micmacmo]

TopPop, you're probably right about the impact of the perforated plastic. But I was more amazed by how much things opened up with the felt removed (and why JVC put it there in the first place!). Relatively speaking, removing the felt elicited the bigger "wow" from me.

Also, I think the addition of the sound deadener altered both the bass and the treble, which surprised me. It could be just psychoacoustics at play. Or auditory placebo. Or willful self-deception. In any case, it was a very pleasant change.

Thanks for taking the initiative and sharing your findings.

[nickchen]

I've been linked here from elsewhere, damned interesting modification, I must admit. If I wasn't already too deep in my "silverback" phase, the modded RX900 was certainly someting indispensable on my "must try" list. Well done, team tinker!

[DoomzDayz]

any more impressions of this mod on rx700? these seem like quite the budget phones

[Aita]

First off I'd like to thank Toppop for his ideas and pictures and for contributing personally to this endeavour to help out a poor headphone crazed college student.

before I go into detail I would like to ask that anyone attempting this mod please give the JVC's at LEAST 10 hours of burn-in time as the difference in sound to me was more pronounced then I would have thought (and this is coming from someone who didnt believe in burn-in before).

Ok on with the MODS!

Felt removal
This mod helps to get rid of the veil on the mid-highs and highs in my opinion and does a decent job of it. While you cant expect earth shattering changes, the vocals on all of the songs I listened to perked up and were able to keep up with the mids and highs, which to be honest is a really big deal. Beforehand whenever i went to EQ the highs/mids the veil or muffle would still be there and would make listening to Jill scott, Anthony HAmilton, or Eric Clapton all but impossible. With the felt gone, the veil was lifted and i could hear the subtle nuances to Scott's voice and that is key to many of her recordings. All in all i would say that anyone who buys these shoulds should immediately remove the felt if they feel the veil to be too much for them after the burn-in or maybe before if it really annoys you. Also i should note that the highs onthe JVC are not the most extended I've ever heard but for the price and the target audience it should be more than sufficient and a little EQ will satisfy most.

Dynamat
While i consider myself to be a pretty avid basshead, that doesn't mean I dont liek a little control to my bass which the RX900s had only moderately at first. Sure with EQ they could rattle right off your head but for some they want control to go along with the power and this, to me, is where the dynamat comes in. By placing the dynamat on the driver and the back of the housing, the bass on the headphones seemed to tighten up just enough to make the mods noticeable in the music. This is even more pronounced with bass heavy music like rap and especially with reggae. I mention reggae specifically as the reason i know alot of people dont like to listen to is on heaphones is either 1. There isnt enough bass to acurately reproduce the rhythm. OR 2. even when there is enough bass it is usually so bloated and muddied that you miss the precision bass needed to reproduce the rhythm correctly. The dynamat largely cures that problem as even my father admitted that he could finally listen to it on these headphones(that my friends is higher praise then you'll ever know! lol). Unless you want to keep as much unweildy bass as possible( and you might) I'd recommend the dynamat mod as well.

I have yet to try the stuffing mod as i jsut dont have enough time to get off campus to a marshalls to get the necessary padding to do so. i will post my impressions on that mod as well when i get the time(though I'm not sure if i even WANT to tame the bass with the stuffing but I'm too curious now not to try it lol). In all these mods will really help strech the value of these headphones and make them even more of a bargain.

Oh and one last interesting note: After the dynamat mod when i went to EQ the highs I found that the shrillness that normally is associated with the altered highs was now gone. I dont know if it was because of the covered back or the dynamat on the driver, but i could definitely tell that they werent as shrill or annoying as they were before. It was apparent after 4 or 5 songs when i reflexively winced at one part in a paticular song only to realize the shrill was gone. This little improvement to me is worht more than any of the other ones as i have a fondness for EQs and that could have been a deal breaker later on down the line.
Thank you for bearing with me,
Aita

[TopPop]

^Wow, thank you so much for your impressions! They are pretty spot on with what I've heard, to be honest, especially with your description of the felt removal.

For the record, I think you will find when you put a thin layer of stuffing in the cups that the bass won't be so much tamed as it will be further tightened. The extension will still be there, but it should be even a bit more less muddied, and with a bit more punch than without it.

Enjoy, and do post your impressions of the stuffing, as well!

[j2kei]

Originally Posted by DoomzDayz

any more impressions of this mod on rx700? these seem like quite the budget phones

i'll try to post some short impression. i plan on dynamating the back of the driver and do some stuffing first. if i'm still not satisfied with the bass, i'll dynamat the cup.

[micmacmo]

Aita, I fully agree with your impressions. Thanks for being so thoughtful and thorough.

After I modified my 900s (sound deadener, lens removal and stuffing), I got onto a little Sly and Robbie kick, I was just so delighted with the depth and control of the bass. I'll have to see how these cans perform with some other reggae, now that you mention it.

I'm looking for a new set of phones not so much to replace the 900s as to complement them. I'm considering the RX700s (I believe that being cheap doesn't mean I have to suffer too much...or at least so I hope.)