The Most Excellent Sennheiser Amperior and HD 25-1 II Page 2

Stored Energy
Stretch a rubberband between your forefinger and thumb; with your other hand pull the rubberband like it was a slingshot; then let go. Sproing! It vibrates like a guitar string for a bit, and eventually stops. When you pulled the rubberband back, you were storing energy in it; when you let it go, it released the energy with a bunch of vibration before going back to its stable state.

Sennheiser_Amperior_graph_300impIn a headphone, the diaphragm makes acoustic energy, which radiates off the front of the diaphragm for you to hear. But the rear of the diaphragm also radiates energy and, in a sealed headphone especially, this acoustic energy pushes and pulls on the rear of the housing, which stores a bit of the energy depending on how elastic/stiff it is.

Now imagine you have headphones on, and you play the sound of a single hand clap. (No, not one hand clapping, one single hand clap ... an impulse.) You'll hear the sound at your ear, but the sound will also go off the rear of the diaphragm, smack the back of the housing, and have some of its energy stored. In the very next moment, it will release that energy and you'll have a little extra sound in the headphones that you may hear from the vibrations of the housing ... just a little ... but it's there.

In the image to the right, at the top you'll see again the inside of the HD 25-1 II. The small walls radiating from the center are there to stiffen the rear wall of the housing so it doesn't absorb and re-radiate acoustic energy ... but plastic is pliant, so it does store a bit. Below it, you'll see the Amperior's aluminum capsule housing. It doesn't have these stiffening walls, but because it's aluminum it's dramatically stiffer than the plastic housing. It will not store nearly the same amount of energy as the plastic housing, and therefore releases less energy after the fact to muddy up the sound.

This phenomenon is readily apparent in the measurements of these two headphones. In the 300Hz square wave responses to the right, you can see that both waveforms are quite similar in general, showing that these two headphones are nearly identical. But it's also obvious that the HD 25-1 II response is noisier. I think this indicates the capsule housing releasing the stored energy from the intense transient of the leading edge of the square wave. There is obviously less of this noise in the Amperior square wave.

Similarly, you can see in the impulse response of these two headphones that the HD 25-1 II "rings" more, and creates a longer trail of noise after the impulse.

Sound Quality
Again, for my full take on the general nature of the sound quality of these cans you can read my review on the Sennheiser Adidas Original, which is exactly the same as the HD 25-1 II. All these headphones sound very good, indeed: clear, articulate, well-balanced, and punchy.

The big surprise for me, however, was the subjective difference between the plastic versions of this headphones and the aluminum Amperior. The effect of the small amount of extraneous noise in the less stiff housings of the plastic headphones was quite obvious. While the HD 25-1 II is a good sounding headphone, I would characterize its performance as "very good mid-fi," while my experience with the Amperior reached what I would consider "entry-level audiophile" performance. The Amperiors are the best sounding supra-aural sealed cans I've heard to date, handily besting the DT1350, V-Moda M-80, and, of course, the HD 25-1 II. I love these headphones.

Previously, I've felt the HD 25-1 II had a bit of an edge to them, in the case of the Amperior the highs are simply clear and articulate; there may be the slightest edge to the sound, but it's not bothersome in the least. Sure, they don't manage to pull off the airy, spacious highs of reference quality cans; and neither do they deliver the liquid coherence and transparency that a full-size, open headphone can. But for this type of headphone (small, sealed, portable) they are remarkable.

My One Gripe
Both these headphones did drive me crazy, though. The 1/8" stereo mini-plug at the end of the cable was TOO DAMN LARGE TO REACH THE JACK OF MY iPAD OR iPHONE THROUGH MY OTTERBOX DEFENDER CASE!!!! Jumpin' Geebus, Sennheiser, look around at the cables out there! Everybody is making slender plugs these days. What's up with that?

Sennheiser will be shipping the Amperiors with a three-button phone adaptor, but I don't know if it's going to have a small plug. The good news is that the cables are relatively easily replaceable, and if Sennheiser figures out that they've blown it on the connector and make a new cable, you'll be able to replace it.

Is it worth nearly twice the price of the HD 25-1 II for the Amperior? Yes! Sure there's always a diminishing returns curve for all things audio, but hogging out (machining), finishing, and anodizing aluminum capsules ain't cheap. The improvement isn't just cosmetic either; the increase in capsule stiffness nets a very real improved listening experience. Both are very high performers in this type of headphone at their respective price points, however.

Beyond the great sound quality performance, the incredible durability, excellent isolation, and extremely secure fit on the head, make both these headphones outstanding performers. The lower impedance and higher voltage efficiency of the Amperior make it an excellent portable headphone EXCEPT THE PLUG IS TOO DAMNED BIG!!!

Both these headphones are going on the Wall of Fame. The Sennheiser HD 25-1 II is an extremely cost-efficient headphone for audio pros needing a small sealed headphone for DJ, ENG, location recording, and musicians' studio purposes. The Sennheiser Amperior is simply an outstanding portable headphone for audio enthusiasts and pros wanting a headphone that will also be accurate and articulate enough for mixing and mastering applications. Both highly, highly recommended.

Video and Resources after the measurements.


Click on graphs image to download .pdf for closer inspection.

Raw frequency response measurements show these headphones seal fairly well and reliably. Bass is somewhat rounded and emphasized to 200Hz, then fairly flat to 2kHz. I like this curve for these cans, it gives them a solid bass response even when they aren't quite sealing, and mids that are fully present throughout. The subsequent roll-off to 6kHz is typical and likely heard as fairly flat. The peak at 8kHz is also somewhat typical of headphones generally; I hear this peak in listening as slightly too bright in this area. Highs remain fairly strong after 8kHz, and are about the right level. This frequency response curve is a good result.

30Hz square wave shows a slight bowing as indicated by the bow in frequency response from 10Hz to 300Hz.

300Hz square wave shows slightly more overshoot than I'd like to see; the upward slope thereafter shows a strong upper mids response, which tends to deliver a punchy sound. Both 300Hz square wave and impulse response show this headphone to be fairly free of ringing due to the machined aluminum cups and extra damping.

THD+noise measurements indicate good power handling and tight bass response. The distortion peak at 5kHz is a bit disturbing and again may explain a slightly grainy sound at times.

Broadband isolation at -13dBspl is good, and with 24 Ohm impedance and 24mVrms to reach 90dBspl loudness, these will play fairly loud on portables. The high performance of these cans would benefit from a good portable headphone amplifier, if you so choose.

Current measurement .pdf and updated measurement notes for the HD 25-1 II on this page.

1989 Manual for original HD 25 and newer HD 25-1 II and HD-25 SP II.
Cool U.K. custom paint jobs on DJ headphones.
A review from the DJ perspective at Scratchworx.
Head-Fi threads for the HD 25-1 II here, here, here, here, here, and here.

Sennheiser USA
1 Enterprise Drive
Old Lyme, CT 06371
(860) 434-9190

killmurer's picture

From the pictures it seems like it you compared the amperior with velour pads to pleather clad hd 25s? Don't the pads themselves make a big enough difference?

Tyll Hertsens's picture
They'll almost certainly make some difference. I should try to measure it ... but it's late now, and I don't want to think about it. Maybe in the morning I'll reconsider.
kitasaitama's picture

Don't these headphones have something like a bag to take them like DT1350 does? It will be a pity If they don't....

donunus's picture

LOL this would be pretty funny if they sounded almost exactly the same when both are using the velours.

Limp's picture

You know, the 25-1 has a steel cable, while the Amperior got copper.
Sure that's not why you're hearing a difference? ;)

13mh13's picture

$50 more than 1350 ... so are they better, different, etc?

bravo4588's picture

Do you know when they will hit the European market?
And is the Amperior really better than the DT1350? WoW!!

Roy G Biv's picture

The jack on your Otterbox Defender Case is TOO DAMNED SMALL!!

2Twinster's picture

Hey Tyll, can you try the two pieces of damping from the Amperior in the HD25-1 II cups? That could be enough to reduce the backwave reflection.

13mh13's picture

Signs hung around Senn. HQ read: "Kreatshe Demand"

Orig. Sennheiser lab prototype: Aluminium body (like Amperior). Senn. mkting dept. says: Diese will nicht sellung -- zu fukkung teuer. Use plastische kapsule fur now. "Kreatshe Demand". Get mann fukking hooked on model's sound. Dann, few Jahren spater, introdusche NEUE+IMPROVED "Amperior" mit effektiv psychologische kampaign.
Sell lots. Kollect viele Marks. Gehen Sie auus fur Bier.
Next kampaign: HD700

Okay, so I'm a sucker: The IE-80s have metal capsules (over IE-8's plastic) and they are better.

ultrabike's picture

I was seriously considering an HD650, but the prices have gone up dramatically. This deal with the Amperior is not very attractive. It almost seems like Senn wants to pull out a Bose marketing strategy with these prices. I'm eyeing the Denon D2000 and the Beyerdynamics more seriously now... I still have a lot of respect for Senn, but this Amperior + HD650/600 and the HD800 price is IMHO very questionable. Meanwhile you have Skullcandy pushing really hard... Weird... and interesting :)

13mh13's picture

... competition is catching up. And the "Made in Germany" logo splashed on packages and products is ... gettin' old.
Also, 'Amperior' is a weird -- WTFIT!! -- name for a headphone and, style-wise, pretty ugly.

ultrabike's picture

Agreed. I get the Amp part of the name, but what is it? "Did you say I'm-Su-perior or I'm-In-perior?" ... "No man I said Am-perior" (silence) "You are whot?"

Regardless, this reasonably performing headphone could be named Ugly-Duckling, it is the price that is hard to swallow.

13mh13's picture

First, I don't get why Senn changed their naming strategy from -humble acronym-number (HD-650, IE-8) to a 'word-name'. If one just heard 'Amperior' or 'Whatever', one would never think it was a Senn product. IAC ...
Like the case with writing owner's manuals and product literature (and web site write-ups, PDFs, etc.), when it comes to nomenclature ... best either use and or heavily consult with lotsa NATIVE-TONGUE speakers before proceeding further. Esp. when it comes to naming something for such a large worldwide distribution. Otherwise, Arschlochs like me will drill them a new one via insulting-und-embarraßing-as-fukk-to-them forum postings ;)
I think "Amperior" -- whatever-der-fukk it means -- was probab. coined up by Germans THINKING in German.

Great line from Firefox (1982 film):
Dr. Baronovich: You must *think* in Russian. [When discussing with Clint Eastwood charac. about the MiG's thought-controlled weapons system]

endk17's picture

Rather a small and most likely insignificant difference but they actually have a "Made in Ireland" logo.

The Monkey's picture
Agree. Senn's pricing strategy is not to my liking, and I think Senn underestimates the long term damage it will do to its sales and brand. I would love to see an interview with Senn about this, but doubt they would be willing to talk about such things publicly.
donunus's picture

I agree 110% Senn will never really talk about the pricing here. I've seen it before with so many senn products... px100 to px100-II, hd555 to hd558, 595 to 598, 580 to 600 to 650 price hikes with only slight tweaks, cmon. Its a good thing I happen to like their hd6xx sound because if I didn't, they would never get any business from me.

Tyll Hertsens's picture
The root of the headphone pricing issues lies with Monster and dDre's Beat marketing bullshit driving the prices of headphones up with among wanna-be teensters. Sennheiser (and all headphone makers) are riding a gravy train of unbridled demand, at the moment.

I have to review product in the context of the current market, and I thin the Amperior is a top-notch can in it's class and, relative to the competitive products, it's pricing is rational.

That said, most headphones are overpriced at the moment, and it's only pressures from makers like Philips who seem to be bucking the tide, and the consumers coming to their senses that will turn the price inflation down.

I really don't feel like Sennheiser is the bad guy here.

ultrabike's picture

I agree with the idea that Monster is driving the headphone pricing up, and I do not have any respect for Monster at all.

What drove me to write a bit about Senn here is the fact that I really like the sound signature of the HD600. I have the much lower end HD202 and while not exactly audiophile grade, they are fun to listen and I paid $22.20 for them. The HD202 are not fatiguing at all, and from what I've read here and there, the HD600 are also non-fatiguing and a significant step up from the HD202.

The Audeo IEM I have are wonderful, but they can be a little fatiguing, and I do get canal irritation after a while. Comply tips just don't work out for me in terms of SQ.

If I didn't care for Senn products, there would be little for me to complain about their prices. They could sell their cans for $10000 and I wouldn't mind. But I care because I really would like to get my hands on an HD600, and the prices are frustrating.

Not all decent HP manufacturers seem to be jacking up their prices too much: Koss, Grado, Audiotechnica, AKG, and Denon have decent offerings at relatively acceptable prices. So what? Then buy from them and stop ranting about Senn!... Well I did buy some Koss KSC75 for jogging ($16) and they are fantastic. But the reason why I rant is simple: I want the HD600 or like sound signature. And I'm kicking myself because I'm willing to pay < $300 for it, but not the current street price... So I'm naturally frustrated.

Will Senn change their pricing because of me or my ranting? probably not... So suggestions for something of the likes of a HD600 for < $300 might be welcomed :(

gorboman's picture

If your gripe is the plug, then my grip is the price. Sigh... Anyway, since it used a unibody style housing, is it heavy?

ultrabike's picture

Haven't really tried these at all... but for what its worth, aluminum is not heavy.

Negakinu's picture

And I am awesome.

Will now go and damp my HD25-1 in the exact same spot as the Amperior is and replace the cable for a copper one.

ultrabike's picture

You just gave me an I-mperior-ity complex. I'm getting my < $200 HD580 right now!... Oh wait, I can't!... Options man, options: $400 HD600... Whot!?

Tyll Hertsens's picture
You'd be better off, I think, a little epoxy into the wells of the HD 25-1 II to stiffen the plastic. Don't use too much though, as changing the internal volume. Then you could add a little extra foam if you like, but I think it's the stiffening that counts.
alvin's picture

So what's the reason for the steep pricing? Machined aluminum? Added piece of polarizing foam? Velour pads? Uh-huh. The Koss DJ100 is also machined-aluminum and has an overall better-built quality and it costs $79. I'll pass on this. My next DJ headphone will be an Aiaiai TMA-1

This is silly Sennheiser XD

Tyll Hertsens's picture
It's not just the materials used, the DJ100, though decent at its price, doesn't sound nearly as good as the HD25 series.
biseinen's picture

hi tyll,
audiophile on a budget here trying to get the best portable+ cans $400 can buy me to listen to my lossless library of all music genres on my iPhone 4S and do some occasional mixing. after extensive research, including your reviews, i’m particularly torn bet the Senn Amperior and the Grado SR 325is. i’ve always loved the Grado signature but will the iPhone drive them to any high standard? the Amperior on the other hand, have been optimized for portables. also, are they 'reference'/flat sounding enough for mixing? i’m also aware one is isolating, the other open. i prefer the isolation, but only as long as it doesn’t compromise sound quality. fidelity is my priority.

Tyll Hertsens's picture
I'd take the Amperior in a heart beat. It's well known that I'm not a Grado fan,though, so take it with a grain of salt.
biseinen's picture

Noted. I knew about "not a Grado fan" bit. Just never read the reasons why.
Thx much Tyll. I value your opinion and appreciate you taking the time.

Tyll Hertsens's picture
Grados are just too piercing and bright for me.