Sennheiser HD-424s Component Upgrades

[cscottrun4it]

I finally got my HD-424s. I think they must be relatively unused, as they've had quite a burn in period - going on about 40 hrs at this point, and they keep getting better. The bass is becoming much more responsive and showing signs of actually getting somewhere close to the 16Hz advertised. (I know - I can't hear 16Hz, but bass shouldn't be lacking with that spec.) Also, the near ear-splitting treble is being tamed. I can listen at volumes approaching fun without fear of never hearing above 10000 Hz again.

Nonetheless, the HD-424s are unforgiving of poor recordings, at least so far. They are great with HiRes audio, CDs, and well preserved/recorded vinyl. But them "stereo" Beatles albums? For get it. My snap, crackle, and pop Kinks albums from Goodwill? No goodwill shown there, either. Physical Graffiti? Well, the original pressing of that album sounds like badger scat on anything, but particularly on the HD-424s.

Oddly enough, for headphones that were for sold between 1972 and 1976, they like modern recordings far better than recordings from their day. (The drivers on my HD-424s are metal backed. I read those were made until 1976?) So, I've been asking myself, how good are the cables on the HD-424s? Would different cables open things up and make them a little more forgiving?

Before you answer, let me remind everyone of the HD-424s' specs.

2000 Ohms resistance
94db at 1mW​

Getting to 1mW at that resistence has been tricky. None of my sub $200 headphone amps will do it. The guys at Shiit said none of their amps would get there. So I've turned to one of my speaker amps. Plus, that resistence scares me, as I know nothing about cables and 2000 Ohms. And there's the ability to easily change the cords themselves.

So the questions are...

1. It looks like I should be able to pull out the connector ends on the driver side of the cable just like you would with the Sennheiser HD-600s. Anyone know if that's true? I'd hate to break these things. The cable seems pretty well affixed to the drivers.
2. NOS cables for the HD-424s are out there on the internet. Their connectors look very similar to the modern Sennheiser headphones. I can't quite tell if the plugs are two different sizes, however, like the modern cables. Anyone know?
3. Let's say all of that lines up, what do I need to know about cables and the resistence on the HD-424s? I've been considering this cable, at 10 ft, with the 1/4" Furutech FP-704 plug:

https://www.etsy.com/listing/576188778/sennheiser-hd25-1-hd525-hd535-hd540.​

Or... maybe changing out the cable to one that uses modern wiring and couplings is a fool's errand? Normally, for $80 headphones, I'd say yes, but $80 in 1976 is $500 in today's money. I would certainly play with the cables on $500 headphones.

 

[cgutz]

The early HD424 (I have one) had 2000ohm resistance. They can actually have the phono plug cut off and wired straight to speaker out terminals on a power amplifier (its actually in the manual). Some headphone amps maybe don't provide enough power to seriously drive them, but my cheapo Little Bear P1 does drive them just fine. They also work on any headphone jack on any amplifier I have owned.

Later model HD424 had only 600ohm resistance. I have read, but cannot verify, that the 2000ohm version has metal end caps, the 600 ohm version has plastic end caps on the "cans."

The cables can be replaced by the user, so yes, you can pull them out of the drivers. I however have never done it. Sorry, can't answer about replacement cables. I still use my originals.

IMHO These were far and away the best available headphones when I bought them in the 70's. Like a lot of accurate speakers and systems, great recordings sound greater, poor recordings sound poorer, and the resolution of the headphones enhances the defects.

These headphones sounded really good on a quality amplifier with accurate recordings (vinyl or tape) in the 1970's technology. Modern records such as low res mp3 or bluetooth do indeed sound flat on them. Cables won't do anything to make bad recordings sound better, in fact, increasing the detail and accuracy will only make poor recordings sound poorer.

The headphones tend to be bright as you have observed, but this was good in the 70's when many recordings (cassette and vinyl) tended to roll off the highs. They are capable of deep but not "thumpy" bass. Modern digital recordings typically have strong bass, so the bass does sound better, even if they are a bit bright.

Enjoy. I have gone through 4 foam sets over the years.

 

[cscottrun4it]

Thanks, cgutz. I am amazed how the highs have become more tame with time being played. I think I've never understood "burn in" before these. The HD-424's highs sound relatively "normal" at this point. On the bright side, yes, but quite listenable. Plus, I swear, when I first plugged these guys in, I couldn't hear a base drum. I can hear a bass drum now, but there's a bit to go yet. I'd also love to hear a bit more depth to the sound stage, if that possible. I guess that's what I meant by open up.

 

[cgutz]

If I recall, make sure you have the ear foams properly centered on the ear. They tend to be positionally sensitive regarding sound stage and bass.

Enjoy

 

[cscottrun4it]

@cgutz - You are so right... again.... These guys are very sensitive to ear placement. I want to put them too far forward. It's a killer if I do.

Having run the HD-424s now for about 65 hours, I can't believe how detailed they are becoming. I'll have to check back in at around 100 hours. I'm really curious where there will be, then.

 

[Thorsten R.]

Detaching Sennheiser headphone cables from the cans (and yes they basically had the same plug for decades at all of their cans) for the first time is always difficult. Especially at an old headphone I normally use round nose pliers and grip the corpus of the plug carefully. I pull it straight out and do not wiggle the plug. Then I use faderlube or something similar at the pins.

I don´t want to start a cable discussion but those old Sennheisers normally had steel cables, not copper cables. They were solid and reasonably good sounding. They cannot be soldered but only spot welded.