Sennheiser Noise Canceling Headphones: PXC 550 Wireless; HD 4.5 BTNC; HD1 Wireless; and HD1 On-Ear Wireless

About this time last year I reviewed the then new Sennheiser PXC 550 BTNC over-ear, noise canceling headphones in hopes that someone would manage to unseat the Bose Quiet Comfort 35. Didn't happen. The Sennheiser had some great features, but in the end it was just too bright for me.

Recently I got a few more Sennheiser wireless noise cancelers and I found they too seemed overly bright. Now I consider Sennheiser the world's best headphone manufacturer. They've got a lot of experience under their belt, so when I hear a batch of Sennheisers, from differing product lines, that all seem too bright and have a quite similar measured response, I've got to question myself. Maybe they know something that I don't.

The thought that came to mind is that maybe wireless noise canceling headphones for consumers should be a little brighter than neutral in order to keep speech intelligibility high in loud environments. Maybe watching YouTubes and making phone calls are particularly aided by a different sort of response.

So, I sent in a question that was basically a short version of the following observations asking whether it was an intentional tuning that is thought to be superior for consumer mobile phone use.

Sennheiser PXC 550 ($399)
Here's the measurements from the PXC 550 I reviewed last year.


This headphone has no wired mode without the electronics on so there may be some electronic tuning going on here, but in the raw plot above (lower traces) notice the rise from 500Hz to the peak at 3.5kHz. I call this the presence region (above 800Hz anyway) and in my experience it should be a gentler rise until about 1.2kHz and then steepen to the peak, which in this case is about the right height at about 12dB above the baseline level. You can also see in the compensated plot (upper traces) that the plot bulges upward in this area. This is a clear sign to me that these cans will sound forward, and they did.

Also note the narrow dip at 4kHz and subsequent sharp peak at 5kHz. At first I thought this might just be a notch to tune out something undesired in this range but, as we'll see below, this feature is common to a number of these headphones.


The above plot is the PXC 550 wired with noise canceling active. You can see that there's some tuning done to flatten out and extend the bass response, but the strong presence region and 4kHz notch and 5kHz peak remain.


Response is similar with noise canceling in Bluetooth mode. Additionally we see a sharp peak sometimes appearing at 20-30Hz. This is a common artifact for noise cancelers as they fight to keep bass response in the presence of slight leaks in the ear pad.

Sennheiser HD 4.50 BTNC ($199)
Here's a more recent, and less expensive offering.


Wired with no electronics on we can see the basic passive response of the headphone. It's a little bass heavy, but tastefully so. The peak at 3kHz may be a little low in level, but the run-up to it is a nice upwardly curving plot. Oddly—and I say oddly because this is in passive mode and matches the PXC 550 plot—the notch at 4kHz and peak at 5kHz is present. This is something done by the passive acoustic response of the headphone and, because it's common to two of the other cans here, I can only assume is by design.


Now in wired mode with the noise canceling electronics on, we again see a linear run-up to from 300Hz to the peak at 2.2kHz. The peak is a little low in frequency, but is now a full 15dB or more above the level at 300Hz. These sounded like a fairly bright/forward headphone to me. The notch/peak at 4-5kHz remains, and is even a bit stronger than in passive mode. The bass has also been reshaped, though I think this may be a reasonable bass response for some listeners.


Here off the wire but with noise canceling off, you can see the response is more like the wired, passive mode—though the inconsistant bass response indicates I was having a hard time getting these cans to seal—which can be seen in various degrees with all measurements of this headphone.


Turning the noise canceling on in Bluetooth mode and we see the return of the strong presence region; strong peak at 2.2kHz; and 4-5kHz notch/peak.

Sennheiser HD1 M2 AEBT ($499)
Flagship of the Sennheiser wireless noise canceling line is the reincarnated Momentum over-ear headphone, the HD1 M2 AEBT. (Headphone one, Momentum 2, around-ear Bluetooth, I assume.)


In wired passive mode this headphone clearly resembles the wired, non-noise canceling modes of both above headphones.


But turn the noise canceling mode on while wired and we now get the linear run-up with a huge 20dB peak at 2.2kHz! The bass is now even more exaggerated. In listening the bass didn't bother me too much...probably because it did a little something to take my attention away from the significantly bright presence region. The 4-5kHz notch/peak remains.


Off the tether with noise canceling on was much the same.

Sennheiser HD1 On-Ear Wireless ($399)
The only on-ear of the group, the HD1 On-Ear Wireless was a little different.


Notice the 4-5kHz trough/peak has disappeared. Other than the bass boost intruding a bit on the low-mids this is a pretty good looking response, and I heard it as the best of the bunch.


But go wireless and we see the return of the linear rise to a 5dB higher peak at 3kHz, and a big bass boost.


Once noise canceling is active response is much the same above 400Hz, but we see some significant artifacts from the difficulty of sealing with an on-ear and the noise canceling circuit working to deliver bass.

My first question to Sennheiser went did the second...and third...and fourth...

I have no idea why Sennheiser likes that linear run-up to the 3kHz peak. Nor do I know where the 4-5kHz trough/peak is coming from. In the absence of a definitive answer from Sennheiser I'm left to speculate.

I tried these cans for YouTube watching and phone calls in loud environments, and I found them all too forward for comfortable listening, they were just too bright. If Sennheiser thinks this is a better tuning for mobile use I'll just have to disagree.

I would guess that the 4-5kHz trough/peak is coming from the internal noise canceling microphones mounted in front of the drivers. I have noticed this type of feature elsewhere and have come to think that when you put an obstruction right in front of the driver you get a feature like this.

My uninformed guess is that Bose noise canceling patents force Sennheiser to do things in less than optimal ways and the above response profiles arrise as a result. I wish Sennheiser would have filled me in.

Ah well.

Measurement Spreadsheets
PXC 550 wired, wired NC on, wireless with noise canceling.
HD 4.50 BTNC wired passive, wired NC on, wireless, wireless NC on.
HD1 M2 AEBT wired passive, wired NC on, wireless NC on.
Momentum M2 OEBT wired passive, wired NC on, wireless NC on.

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

Maybe's picture

I like how the Momentum AEBT has less Isolation with the noise cancelling on. Same goes for the 4.5BTNC. I'd say that something here went wrong. It may not be their forte, but I have a hard time believing that their noice cancellers are this bad.

Vinhcomputer's picture

If they knew something you didn't about how a good nc headphone should sound like, that means these headphones should have had, as you heard it, good sound quality for at least non-critical use cases (Youtube and the like); but these headphone didn't sound good even for these use cases. That means they don't know how to create good nc headphones.

Journeyman's picture

Too much bullshit going on, I prefer good isolation over ANC any day.

Johan B's picture

At work I am using the Philips SHB8850NC. A certain european review site gave it 5 stars. I bought it because the in-ear phones gave me pressures in my head in combination with the Airconditioning. So I bought these for 100 Euro. The build quality is ... appalling. But the sound .. I love them. They are better than my AKG K240MKII and stand up (Not better) to my other headphones (Philips Fidelio X1, Hifiman HE400s, Sony MDR-EX650) in ears. In fact in terms of value and functionality for money this crushes any head phone less than $300US. Try it!

RPGWiZaRD's picture

Are the HD4.40 still a decent buy? I don't want NC but I'm in need of a passive BT headphone though.

Tyll Hertsens's picture
jacobhs7's picture

It's also possible that Sennheiser is simply guessing that users will listen at lower volume levels with the noise cancelling enabled, and the more V-shaped sound profile with that setting reflects that expectation. But I'm guessing not.

potterpastor's picture

That’s too bad about these noise cancellers, I suppose that every company has their idea of what they are going for and not everyone will agree.

Hope you get a chance to have some ear time with the newly released Sennheiser HD 660S.

zobel's picture

No excuse though, for releasing these losers. I wonder who has the last say there, on voicing/sound quality standards, at Sennheiser.
Surely they can still hear alright.

MarkF786's picture

I recently bought an Acura MDX and was surprised how awful the "ELS Studio Premium Audio System" sounds; my old 2006 Acura TL's system sounded much better. Doing some research, many people speculate the Active Noise Control is to blame, and that in trying to cancel out the road and engine noise, it stops all over the lower frequencies of music. The resulting sound is unpleasantly bright and harsh.

Who knows though, maybe they're using a similar ANC algorithm as Sennheiser.

Bob Katz's picture

Noise cancellation involves a complex relationship between the microphones and the headphones. The microphones sense the ambient noise and that is subtracted from the signal. However, a very small amount of leakage back into the microphones from the headphones does occur. This signal is misinterpreted as noise. It is largely high frequency and so instead of cancelling (subtraction) it adds! Even if the leakage is 10 to 20 dB down at can cause coloration. If the noise cancellation gain is turned up too far it can even become positive feedback. Conversely, the closer the microphone to the headphone the more frequencies it can accurately cancel. It's a game of cat and mouse and compromises as so positive feedback is likely the culprit in the inexpensive models. Manufacturers also increase the noise cancelling more than they should as a sales gambit. There's nothing more instantly convincing on the sales floor than that switch. Yet, the untutored consumer notices the cancellation much more than the tonal aberrations.

Exactly the same phenomenon occurs in hearing aids when they squeal. The proximity of the microphone to the earpiece and the high gain of the Mike pre-amp is a recipe for disaster. Isolation is expensive and is the first compromise in a noise-cancellng design. The DSP (if there is any) is designed to help distinguish signal from noise but good, uncolored dsp is also an art.

zobel's picture

I thought that these noise cancelling cans worked by adding reversed phase outside sound signal to the signal driving the cans in proportionate SPL to, and in the same frequencies that are passed through the cups and into the ears passively? Do they ever incorporate microphones in the ear cups to create a negative feedback loop to remove the difference signal between the internal microphone and the signal driving the cans? Is there sometimes a combination of these two methods in use?

Tyll Hertsens's picture

Most noise cancelers these days have mics both inside and outside the earpiece. Generally, the outside mic is for the feed forward control, and the inside mic feed back control. It's quite complicated. Here's a reference for how it works:

zobel's picture

I enjoyed the read.

buyukbang's picture

Hello Tyll,

Thx for your all efforts to make clear thing on the Headphone world for potential customers and Headphone addicts. I really like to read your reviews and watch your videos.

As an P7 Wireless owner I'm holding my brath to see how you compare new PX that replaces P7 Wireless. Can we expect a review soon?

Lawk's picture

I had the Momentum 2 AEBT now called HD1 and I also had the 4.50 BTNC.

I found both to have a a honky midrange. Bass was tight but had no texture and the highs were also too soft for me.

In the end I preferred the JBL Elite 700 for their bite and livelyness. The Bose QC35 are pretty good too, but they are kinda rough mid-treble.

In the end I found the B&W P7 to be the best BT option for me. No NC but they have a lively sound with good treble resolution and dynamic punchy bass :) and the human voices sounded the most authentic on it from those vocals I know well.

Old Pa's picture

Sennheiser now distributes IOS and android versions of CapTune which is a music player app with eq adjustments for headphones such as the PXC-550. Did you utilize such an interactive app during your testing? Might this have corrected the brightness problem you noted? Thanks.