[digitalreferee]

Hi all, so I have recently gotten hold of a pair of CD1700 Sony cans, after being very curious about them for years. Got a nice-looking pair off of Yahoo auctions, however while they do work and produce sound, they have some severe channel imbalance (right ear being louder than the left, and there being almost nothing below 200Hz in the left cup, or at least extremely quieter in that region). It's been suggested to me in another thread on Sony headphones that the problem could come from the cable being tired.

I've seen mods online before for this headphone but they are usually kind of ugly (drilling holes into the bottom of the cups, etc.), and after some research I have not been able to find any instructions online on how to mod this specific pair either.

I have three questions:

- is there a way to determine that the channel imbalance for sure comes from a bad cable, and not just a shot driver? (ideally before attempting any sort of mod)

- if it does come from the cable, is there a way to mod these particular headphones in a way that doesn't ruin the outside of them, i.e. by having a single 3.5" female jack in the place where the original cable is normally attached?

- does anyone have experience with these or similar Sony headphones who could provide some guidance and/or instructions on how to perform this (knowing I have never modded any headphones before)?

Thanks!

 

[GREQ]

- is there a way to determine that the channel imbalance for sure comes from a bad cable, and not just a shot driver? (ideally before attempting any sort of mod)

Yes.
Use a multimeter to determine that both drivers are reporting similar ohm readings.
Doing this twice, first through the cable and then directly on the speakers should rule out a cable problem if they results are a match.

- if it does come from the cable, is there a way to mod these particular headphones in a way that doesn't ruin the outside of them, i.e. by having a single 3.5" female jack in the place where the original cable is normally attached?

I've seen this mod done before on the CD1700, so it's certainly possible.
This is where I saw it.
- https://systematicsound.wordpress.com/2021/10/17/sony-mdr-cd1700-review/

BUT - before all of that, make sure that the drivers are actually CLEAN.
The old acoustic foam that was covering the drivers is definitely rotten and crumbly now - it's possible that a large piece or pieces of this foam have got between the metal acoustic lens and the driver diaphragm - this will prevent the diaphragm from moving and do 2 things - reduce bass drastically, and reduce the volume on that side.
- So I think this is the most likely issue before thinking about any kind of mods.

 

[digitalreferee]

Hey Greq, thanks for the detailed answer.

Both drivers are reporting similar readings on themselves (32.1Ω on the left driver, 31.8Ω on the right ; the headphones stated impedance is 32Ω), the ohm readings through the cable are slightly higher (34.3Ω left/tip, 33.9Ω right/sleeve) but consistent.

As far as the foam is concerned it seems like the previous owner did remove most of it already, there wasn't much left although still some of it was sticking on the plastic piece resting on the ear but definitely not enough to make a complete disc of foam. I removed some bits and pieces carefully but it didn't seem like there were any stuck inside the driver on the left ear, or if there are they're wedged in there pretty good.

I've seen this mod done before on the CD1700, so it's certainly possible.

This is the mod I've seen too after doing more research and it would be ideal. I did contact the guy behind the mod who is on these forums right here. However considering both readings are the same I'm not sure if there's anything else to test at this point?

 

[GREQ]

However considering both readings are the same I'm not sure if there's anything else to test at this point?

Damn... I hope the left driver isn't toast... they really are unique and excellent headphones.

I can't really think of any other tests other than to check if the driver diaphragm isn't dented, although this is extremely unlikely.
The last time I had less bass in one driver, it was a dented diaphragm...

I don't suppose you have any way of gently blowing air into the driver?
- I use one of those hand-operated-pumps for blowing dust from camera lenses.
I'm just thinking there might be some foam or debris trapped and hidden somewhere between the grill and the diaphragm, since it is quite difficult to get a good view inside of it.
But if you're sure it's clear, it might be a dying voice coil... or... in another unlikely case, an unseated voice coil.

If it was a vintage planar, I would suggest pumping VERY LOUD bass through it for a few seconds to see if that 'shakes' it back to normal, but that method has never worked with a dynamic for me :/

 

[digitalreferee]

I can't really think of any other tests other than to check if the driver diaphragm isn't dented, although this is extremely unlikely.
The last time I had less bass in one driver, it was a dented diaphragm...

Okay well, I took some pictures because honestly all of this is way above my paygrade, so it's entirely possible that there's something glaringly obvious that's staring me in the face and I'm not seeing it…

A couple other points:

I have a pair of CD900STs which I bought recently, and I dumbly stepped on the cable while wearing it around the house, and now they have less bass response (and slightly less volume) in the left earcup as well (I swear it's not my hearing that's going lol, I don't have this problem with my other headphones), so I checked the impedance through the cable as well as on the drivers on that one too, and the readings were also very similar, even though I know it's the cable that's at fault. Could this problem on the CD1700 also be because of the cable and not showing up on the impedance readings?

Might also be my multimeter, admittedly it's a very cheap thing I got at jeff bezos' emporium just to check continuity so that could also be flaky.

I tried to play some very loud and bassy music through the headphones briefly (not extreme loudness but enough that I couldn't put the headphones on for more than a couple seconds) and I did hear the left driver "rattle" along with the bass, like something hitting the plastic enclosure, so there might very well be some of the foam blocking it but I find it incredible (if it's that) that it would be so present, because honestly the disparity in volume between the two drivers is enormous (I don't have anything to measure dB but it's one of those nakedly obvious imbalances) and I don't really see anything that different between the two just looking at them.

 

[GREQ]

So, the cable causing less bass in ANY headphone is basically impossible, so we can rule that out.

Looking at the driver photos, it looks to be in physically good condition, with no dents.

Since all the impedance readings are similar and consistent, I think we can also rule out the quality of the multimeter - even cheap ones are generally fine and accurate enough for this kind of thing.

I think the bass rattling is almost certainly attributed to the loose tuning-paper on the front of the driver.
I wasn't sure which variant of the CD1700 driver you had, but I can happily inform you, it's one of the better ones ^^
The fact that your version has the paper damping (the variant I own does not have this) also means that it's even less likely for small pieces of foam to get between the diaphragm and acoustic lens. So that's more good news.

So, the white part outlined in red, is all LOOSE... I don't know if the glue is just old, or if it was never fully glued down on these models - heavy bass will just cause this to rattle... so under normal listening conditions it's absolutely nothing to worry about.

Since your CD900ST is ALSO starting to experience the same lack of bass.... I naturally come to one possible conclusion - please test both headphones on a different device.
Maybe there is a problem with the socket connection on your device, or the device itself has a problem.
Or you're not plugging it in correctly (deep enough??)???

 

[digitalreferee]

I think the bass rattling is almost certainly attributed to the loose tuning-paper on the front of the driver.

Well I would like to believe that but I don't feel the paper rattling against my ear, since I tried putting on the headphones with the pad missing, just to see if it was that. It seems like the loose paper is just there and I watched it while hearing the "rattling" and it's not moving at all. It really sounds like the rattling is coming from inside the driver "cage" itself, like the bass is trying to come out but it's only managing this. I'll try to record a clip using my Zoom H4 recorder tomorrow.

I naturally come to one possible conclusion - please test both headphones on a different device.
Maybe there is a problem with the socket connection on your device, or the device itself has a problem.

As far as the device goes, sorry to disappoint again, but I have tested these on basically every source I have, that includes my Sony DAP, my older FiiO DAP, multiple different Discmen, my three hi-fi amps, directly from my component CD player, and even laptop computers… This isn't a problem that is exhibited on any of my other headphones, and it shows up specifically with these two and on any device I plug them in…
And I am also positive that the slightly lowered volume and bass response in the left earcup on my CD900ST showed up after I mistakenly stepped on the cable and it tugged on the headphones themselves (it was only for a brief second but sadly apparently enough to damage… something: cable, connector?)

 

[GREQ]

That's the worst news :/ I was really hoping the buzzing was the paper.

If it really is the cables (which would surprise me) it's a relatively painless process for someone experienced to fix.
If not...
The next step would either be invasive and possibly destructive investigation by removing the driver from the baffle, or the need to source a replacement driver.
For invasive investigation, the glue around the driver would need to be carefully broken down so the driver can be removed without destroying the baffle, so a proper driver observation can be carried out.

But since you already said "all of this is way above my paygrade" I'm guessing that either of these options are not possible without sending it to someone who knows what they're doing, and replacement drivers are basically impossible to come by.