BOTH cables you linked here (originally for the HD25 phones) are NOT good for the HD540, not because of the connectors (which DO fit the HD540), but because they are NOT symmetrical Y cables (both Left and Right sides equal) but asymmetrical - one side is longer then the other. If you carefully look ay the photos you'll see that. That's because most HD25 phones, being DJ oriented, are designed this way. As far as I know there is only one HD25 model (HD25SP) that uses a symmetrical 'Y' cable and this is a "heavy duty" STEEL cable (not copper) that Sennheiser still keeps into production. The original HD540, 600 Ohm Ref.1 (and the HD250 Linear1 had steel cables).
I belong to a MINORITY here that actually PREFERS the sound of the steel cable to the copper one because it has a bit more "sparkle" others think the copper sounds more refined and detailed... If you read at the start of the thread the situation was just the opposite...
) so be warned about that.
THIS is the STEEL cable I'm talking about,
3 meters long - Sennheiser HD 25-
SP Replacement Cable: (fits perfectly all the 540-250-580-600-650 and other lines with this connector. I know from experience - I have a few of them)
https://www.audiosanctuary.co.uk/sennheiser-hd25sp-heavy-duty-cable-black-300cm.html
THIS is today's Sennheiser COPPER cable with the old shaped connector:
1.5 meters long - Official Sennheiser Spare Part No. 508822:
https://www.audiosanctuary.co.uk/sennheiser-hd-replacement-cable-black-3.5mm-jack-adaptor.html
THIS is really the best deal in town, official HD650 replacement cable,
3 meters in length, but you will have to "shave" the plastic a bit with a scalpel to get it in...
https://www.audiosanctuary.co.uk/sennheiser-hd650-hd660-replacement-lead-3m.html
THIS is also an official Sennheiser replacement headphone cable (cat.no.508688),
3 meters in length, to fits most of Senheisser models with this connector, you will have o "shave" the plastic a bit to get it in.
https://www.audiosanctuary.co.uk/se...d580-cable-3.5mm-jack-plug-3m-ofc-508688.html
THIS cable is
1.4m in length, made by Apogee. and comes with 2 Pin Connector to 3.5mm Jack termination. Also have to "shave" the same as above.
https://www.audiosanctuary.co.uk/sennheiser-hd650-hd600-hd650-apogee-replacement-lead-1.4m.html
I'm sure you can find all these cables at Thomanns and other suppliers
Sound wise, there are small differences IMO, but I don't want to enter the subject - to each one his ears...