[Cristello]

when I looked at Tyll's Frequency Response graph for the pioneer, his measurements seemed to REALLY coincide with your impressions. But! I noticed something else that I don't quite understand: "Frequency response measurements show good seal achieved easily, and bass rolling off below 100Hz." Tyll has said many times that achieving a good seal is a key factor in good low-end response, at least for closed cans. Since the HDj-2000 DOES have a consistent sealing ability, why the sudden, linear drop off below 80Hz or so? Additionally, his next statement says: "30Hz square wave sagging indicates a somewhat loose bass response, which was heard during listening." This got my mind racing. IF the seal is good, but the headphone has trouble reproducing bass without rising distortion (as the HDJ-2000 is shown to do in Tyll's THD+noise plot), either the driver has a limited range that doesn't include it OR the driver has something else going on entirely... When you commented, "When playing heavy bass sounds, I could feel vibrations emanating from the cup and into the first arm segment," and, "...sealing around the outer rim of the baffle plate with some putty... Yowza, that did the trick. Bass extension is noticeably improved," I thought back to what Tyll said about it having loose bass. Is it possible that the WHOLE driver unit (not just the diaphragm) is not secured well enough by just the three screws and needs a more solid mounting to the outer frame in order to more evenly distribute and relieve the vibrations? I thinking firmer than soft putty, for sure. Anyways, thanks for the great guide and for putting up with my long thoughts! Any response would be appreciated.

 

[Armaegis]

I think most headphone need a sturdier/heavier baffle than what they currently have. The tradeoff then is comfort/weight. Most are also desperately in need of some damping material to remove resonance and ringing, which will make certain frequencies seem louder (bass will seem rumbly, treble will zing)
 
As for the bass rolloff, reverse the thinking a bit and think of it as a midbass hump. The low bass levels are really just returning to normal, but seem like a rolloff since they're starting from higher up. 
 
Going back, when I say bass extension is improved I think I would be more correct in saying that I've reduced the midbass hump so the entire bass region is flatter and doesn't resonate as much. There's less bass oomph overall, but it's cleaner sounding. 

 

[Cristello]

I see... so my theory that the baffle plate is moving in a negative fashion directly proportional to the strength of the vibrations produced by the driver (in this case the lower the frequency, the stronger the reciprocating force) is not entirely correct? I am still wondering what the effect of replacing the baffle plate with a rigid wooden or metal one might be. I agree that keeping these cans light is preferable, but not having felt the weight of the baffle plate alone, I am not sure that any other material would be significantly heavier. Also, would increasing the density and mass of the baffle plate have the same effect as mass damping behind the driver? I am inclined to believe that it should have the same effect.

 

[Armaegis]

You are correct. It's the whole "equal and opposite reactions" thing in physics. 
 
Replacing the baffle with something more rigid should in theory improve the sound from the driver. On the flip side, a baffle might also act as a radiator. Ideally you want something rigid, heavy, and which absorbs internal vibration.
 
Yes increasing density and mass of the baffle should effectively be the same as mass damping around the driver. 

 

[Cristello]

Just to confirm, is the baffle plate secured to the rest of the housing by ONLY the three screws, or is there some other form of mounting? (i.e. - does it have some way it snaps in place or interlocks?)

 

[Armaegis]

Nope, only the three screws. The baffle doesn't even really sit all the way into the cup either; it kind of floats. 

 

[Cristello]

thanks for all the quick replies. I don't suppose you would consider redrawing the frequency response (post-mod), especially since you have had a lot more time with them? your drawings only showed a boost in the very lowest end of the spectrum and a evening of the highs, but your comments are somewhat conflicting (i.e. mid-bass humps and more "smoothing" than a boost, per-se). It is possible that I only need a bit of clarifying from you instead.

 

[Armaegis]

The stock frequency response has a midbass hump and a somewhat wobbly treble typical of closed headphones. After mod, the hump is less pronounced which makes the subbass feel more even, and the treble peaks and valleys are less pronounced.

 

[Cristello]

thanks for the concise summary. I feel much more confident about these headphones. You may want to rename this thread though, as I came in here expecting MORE bass, not just a balancing of sound. I am not sure if others will get confused as I did...

 

[Armaegis]

Good point. When I first started the mods it did indeed seem like a bass increase. But then I kept tweaking and I found myself preferring the flatter and cleaner sound. I'll make some edits tomorrow when I'm less tired.

 

[PROTRance]

Man, I bought Today a MSRNC and I want to do the same mod with this headphone, what do you think?

 

[Armaegis]

@PROTRance
I have no idea what MSRNC is...??

 

[PROTRance]

@PROTRance
I have no idea what MSRNC is...??

I meant audio technica MSR7 NC , They sound are similar,

Msr7 Sub Bass is not powerful so I want to do the same mod with this headphone, what do you think?

 

[Armaegis]

I've never modded the MSR7, so I can't say for certain. I would also be wary about trying to mod a NC model since there is active circuitry which already modifies the sound, and I have no idea how altering things would affect the NC qualities.