Replace Senn HD 25 with hd 448??

Incidentally I've owned the HD238 and upgraded to the HD448 so maybe I can be of some help here:
The 238s, although very much "fun" to listen to, leak like crazy (no isolation whatsoever) and are much less refined and "gritty" sounding than the HD448. They are more balanced, I'd say, but have the general dark and not so detailed Sennheiser sound.
The 448s can be easily driven from a portable (I use a Walkman phone from Sony Ericsson and they sound great). They're light and not that big actually, so you don't end up looking too strange on the street. The isolation is ok, but not enough to hide the fact that you're on a subway, for example. That being said, the sound is superbly detailed in the mids, smooth and very lively, good for guitar-driven music, IMO. The fun factor is slightly less there, due to the fact that they're not bassy (on portables anyway) and more detailed. I consider them to be "grown-up" versions of the HD238, good for when you want to actually listen and get the music.

There is a thread on the HD428, HD438 and HD448. I considered the HD448 but when I read about a 'plasticky bass' I went for the HD428 which is really good to my ears. It's more on the neutral side regarding sound.

If you are used to a HD25 remember the HD4*8-series isn't build to last compared to the HD25. I find my HD428 too plasticky and the cable is just, really thin.

Paul T,
I'll have to revise my opinion on the HD448: they do have bass, and it's pretty clean and tight, when properly driven. I'm saying this because I got a Xonar DS last week and noticed they sound much more balanced now, with less emphasis on the mids and more bass. The overall clarity is still there though. They are in no way bassy, like most headphones I've heard (cheap models, ofc, no hi-fi for me).
That being said, I have only driven them from my Audigy SE - lacking bass there - and the Walkman phone I mentioned, no ipods for me. They'd do ok, I guess, if need be you can always bump up the bass a bit from the EQ.
As for the soundstage, I'm not really sure what to say, as I don't actually listen to much live or symphonic music (except a bit of classic rock where it matters). It's there and there is definitely a sense of separation and distance between the instruments, but not really enough to say "that guy's there and that one's 3 feet behind him to the left". I'm sorry I can't describe things better.

What kind of music do you listen to, anyway? Might sway your opinion on the HD448 on way or another. Also, be warned that they have a relaxing effect due to the sweet and smooth sound. I've fallen asleep may times listening to the Cure or Pink Floyd.

The HD448s are great when amped. I use a T3 and Sony x1051. Without an amp, my sony x1051 is unable to drive it. But they have very powerful mids and highs, and with my T3 amp they improve drastically on the low end. Also with an amp they isolate very well. Not sure how they sound on an ipod, but these cans are great with my T3 amp and sony x.

Get these if your are looking for a balanced, lifelike sound. These are my favorite headphones as of now. But they definitely need an amp. If you are on a budget, I would go for the fiio e3 or e5 to pair with it, or a T3 or T4 if you have around $100 dollars to spend. It is a great improvement with the HD448s, and they truly shine with an amp.

I always thought the senn 25's were pretty highly regarded headphones. Going to the 448 or 428 may be considered a backwards move.

You'll definitely like the 448s and they way they "do" guitars. Congrats then!
Don't be put off by how they sound at first, if you plan on listening from the start, without "artificial" burn-in. The bass will be boomy and the highs and mids nothing special. Let them burn in first, you won't miss anything if you play them 20-30 hours without listening to them.

I'd say they'll be fully burned in after a week or so. I've done mine with 20-20000Hz sweeps and bass loops (30 seconds of 40-60-90 Hz bass), plus assorted tracks, not necessarily bass heavy. Turn up the volume a bit past what you'd consider listening volume to get those membranes flexing and as I've said before, don't be disappointed after the first listen, they don't actually sound that way.

Like Paul_T posted above, the HD25 Concorde is more or less the same headphone as the HD25-SP. The HD25-SP - though not a bad headphone, I've owned one - is for most purposes greatly overshadowed by the regular HD25, also called the HD25-1 or (these days) HD25-1 II. The HD25-1 (or -1 II) is the one that's really highly regarded. The HD25-SP (and by extension the Concorde) has a very similar name and very similar-looking earpieces, but sonically I wouldn't even call it a relative of the HD25 (-1, -1 II).

Unfortunately I haven't heard the HD448 and can't give an informed comparison there. Except to say that in the era of the HD25-SP good-sounding closed headphones under $100 were a lot more rare than they seem to be now.

All the headphones you mention are a downgrade rather than an upgrade.

The Concord HD 25 headphones are 300 Ohms, which make them harder to drive from a battery portable.

An upgrade would be the HD 25 SP (look the same as the Concord ones, but with a much lower impedance and easier to drive) or, better still, the HD 25-1.

You could also consider the HD 280 Pro or HD 380 Pro.

But all the ones you mention would not be as good a the HD 25 Concord in quality in my opinion.

Sorry - this is totally wrong!

The very first HD 25 headphones were the HD 25-1 - and there is no change at all in the headphones from the very first until the present day (other than the internal change to gold connectors internally about 15 years ago).

Very shortly after this came the HD 25-13 - same headphones but 600 Ohms and a 3m cable for studio use.

British Airways approached Sennheiser UK for headphones for Concord. They liked the HD 25, but it was too expensive. Sennheiser UK realised that the HD 25 capsules would easily fit onto the headband of the old HD 414 headphones and as this was just a single piece of moulded plastic it would be much cheaper to manufacture than the multi-part split headband of the HD 25.

So a special 300 Ohm version was done with the cheaper headband for Concord.

Sennheiser Germany realised this was a good idea and then produced a cheaper version with lower impedance for general sale - this was the HD 25-SP. But you cannot have two identical headphones at very different prices, so the SP version was "down-rated" and had internally different capsules to the HD 25-1 and HD 25-13.

The Mk.II versions are identical to the Mk.I except for packaging, accessories and slight cable changes. EG: the original HD 25-1 had a 1.2m cable, rt.angle connector and a push-on adaptor to 1/4". The HD 25-1 II has a 1.5m cable, rt.angle connector and a screw-on adaptor to 1/4". The HD 25-1 II also now has the velour earpads included as well as the leatherweet ones and a drawstring carry-bag is also included.

Added to the range was the HD 25 II with a 2m cable and straight plug and the HD 25-C II with a coiled cable.

The HD 25 did not get "better and better" the best was the first and the "worse" ones are the SP versions which came later.

The current HD 25 headphones are:-

• HD 25-1 II - 70 Ohms, split headband, 1.5m steel cable with rt.angle 3.5mm mini-jack and screw-on adaptor to 1/4" standard jack. Delivered with both leatherette and velour earpads and drawstring bag.
• HD 25 II - 70 Ohms, split headband, 2m steel cable with straight 3.5mm mini-jack and screw-on adaptor to 1/4" standard jack.
• HD 25-C II - 70 Ohms, split headband, 3m coiled copper cable with straight 3.5mm mini-jack and screw-on adaptor to 1/4" standard jack.
• HD 25-13 II - 600 Ohms, split headband, 3m steel cable with straight 3.5mm mini-jack and screw-on adaptor to 1/4" standard jack.
• HD 25-SP II - 70 Ohms, single headband, 3m steel cable with straight 3.5mm mini-jack and screw-on adaptor to 1/4" standard jack. The SP cable is a Y-cable going from below (the split-headband HD 25s are single sided and the cable connects from the top).

I hope this clarifies and corrects things.