The art of cancellation

Using ‘QuietPoint’ noise-cancellation with a twist, Audio-Technica delivers a careful balance between the different demands of wired and wireless sound.

Noise-cancelling (NC) and Bluetooth together of course deliver the ultimate in convenience — hands-free without cables, noise-free by cunning cancellation of lower frequencies.

Yet it’s notoriously hard to achieve with distinction. As we’ve seen on many wireless NC designs, problems come when deciding how to ‘voice’ the headphones. Do you create the best possible cabled sound and then hope Bluetooth won’t muck it up too much? Or do you assume most people will use Bluetooth, voice it for that and let the cabled performance suffer? Or a compromise? Noise-cancelling adds a third effect on the sound, either cabled or wireless, so the designers are left seeking a solution between four separate set of sonics.

Audio-Technica certainly has a headstart in delivering cabled headphone sound, having done so reliably for decades. The NC700BT feels as solid as the company’s usual designs — all in a durable matte black plastic, with memory foam earpads, the headshells able both to twist flat around your neck (facing down) or to fold up on the other axis for very compact storage.

omfort was high throughout use, the headband especially so, spreading the point of contact so that this relatively light design felt almost weightless, exerting no significant pressure around the ears. You could easily kip on the plane wearing these.

All the controls and indicators are on the left headshell (see below), along with the connectors for USB charging and the cable, if you’re using it.

The only physical switch is to power them on, but the left earshell has touch points — tap in the middle to play/pause (and to answer calls), swipe up/down for next/last track, tap top or bottom for volume up/down. This all worked well, although the volume changes are accompanied by loud and redundant bleeps, and also, when used with an admittedly ageing iPhone 5s, only raised the volume to whatever was set on the phone, requiring the phone itself to be used to go higher, rather than the full range being controlled back to the phone by AVRCP, in the Bluetooth profile. (The manual does say “The volume control of some devices may not work well with the product.”)

There’s not much to tell on the audio tech; the drivers are an unspecified type of 40mm diaphragm, likely Mylar or similar being the diaphragm material.

Balanced for Bluetooth
We used these headphones in their various listening modes for the best part of a month. We reckon that, sensibly enough, the balance has been optimised for active Bluetooth use, which is how most users will undoubtedly operate them. In direct comparison we thought the passive cabled sound to be just a little boxy. Lou Reed’s vocal on Walk On The Wild Side was rather shut in, soft in comparison to the other three options, lacking airiness and cut-through, leaving things tilted a little too full in the upper bass. But that’s not to criticise the overall quality — though not entirely natural, it was a detailed and powerful sound, musically enjoyable, and the usual credit to the brand.

Keeping the cable attached we switched the headphones on, so engaging the active circuits and noise-cancelling. We note this changes the impedance of the headphones from 35 ohms to 150 ohms, though there’s no drop in level, the active circuits and a higher sensitivity in this mode presumably compensating. Again there’s plenty of level available, while the active mode brightens things up nicely, at the cost only of introducing a little sibilance to vocals — and of using battery power, of course. Here we enjoyed a strong and dynamic Walk On The Wild Side with a good hit to the kick drum, the bloom of the passive sound stripped away, though with the addition of some sibilants and hiss to Lou Reed’s vocal.

Switching to Bluetooth, with noise-cancelling automatically engaged, a little of this sibilance remains, but the overall quality of the headphone continues to deliver fine music, well supported and impressively devoid of the degradations Bluetooth can impose on the sound. The ANC700BT supports both AAC and aptX codecs, the first delivering better sound for Apple users than the base-level SBC codec, and aptX much improving sound for Android phones which support it. You can hope for some 25 hours of full playback from a full charge.

You can get an extra five hours or so by turning off the noise-cancelling. At first we thought this wasn’t possible in Bluetooth mode (and we regularly criticise headphones for this flaw), but in fact you can do this using those touch-sensitive points on the left headshell. Cover all three in a cupping action and noise-cancelling is toggled on or off. We weren’t at all surprised to hear the sibilance banished and a certain stability delivered by turning it off. Noise cancellation is inherently destructive to music signals, and it’s amazing it works as well as it does in most cases. It should always be an option, and kept for noisy environments. Here you get better sound without it — slightly thicker, yet our preferred balance with these headphones in the long term.

As to the noise cancelling itself, we found it effective, yet quirky. On a city street corner it did a fine job of hushing exterior noise, likewise on the train. Audio-Technica’s supplied information highlights “a newly-developed active noise cancellation system that operates in a wider frequency range in the low through midrange frequencies than typical ANC designs, and provides a greater degree of noise cancellation”, but the specs make it clear the NC acts only up to about 300Hz, with the passive ‘closed’ isolation serving to muffle the rest.

The quirk was that when listening to the NC alone, prior to playing music, we found that turning our head left or right caused the cancellation to break down in whichever ear was facing forward. This was so unusual as to require closer investigation as to its cause, and we’re fairly confident it’s a matter of fit. The seal around the ears becomes less than absolute with the head turned — confirmed by the failure not happening if we pushed firmly on the earpads in as we turned. (The manual even notes a possible issue and suggests “putting them on properly”, which is not very helpful.)

Could this sensitivity to less than a perfect seal be because of an innovation that is touted with these headphones? Audio-Technica’s QuietPoint noise-cancelling system uses a four-microphone multi-feedback system to reduce environmental noise. There are two microphones in each headshell, avoiding the one-sided feel of cancellation in some low-cost NC headphones.

The innovation is in placing one internal microphone not as usual on the inside, close to the ear, but instead behind the driver. This, it says, avoids the problem of microphones “mounted in a location where they can unintentionally pick up some of the generated noise-cancelling signal, which is then reprocessed in a feedback loop and can limit noise-reduction performance.”

We can’t see why moving the mike to the other side of the driver would prevent it hearing the noise-cancelling signal, though it is possible the phase characteristic could be improved in this way. But were the breaks in seal especially notable due to this move, with the feedback NC microphone no longer in a position where it would most easily compensate? Hard to say. The Australian distributor kindly forwarded some questions to A-T HQ, and they clarified that they haven’t moved the earcup mike, they’ve added a second mike behind the driver to cancel pick-up of the noise-cancelling signal... loops within loops. Headshapes vary, of course, and the seal-breaking effect was less notable once music is playing, though apparent when listening to spoken word or podcasts.

Less hidden under music was a significant sensitivity to the physical judder of a bus ride, which regularly sent a series of jolts through the NC and music. We regularly experience this on NC and Bluetooth headphones, and these fell in the medium level of severity. There was no such problem on the smoother rides of a train or plane.

Conclusion
While not quite our favourite at this price level, audio-technica certainly has here a good Bluetooth noise-cancelling contender, with the generally-effective NC and sonic merits across the different available voicings. 

audio-technica ATH-ANC700BT QuietPoint
Price: $349

Type: Active Bluetooth noise-cancelling closed dynamic
Driver: 40mm
Sensitivity: 98dB/mW cabled with NC on; 95dB/mW cabled with NC off
Impedance: 150 ohms cabled with NC on; 35 ohms cabled with NC off
Bluetooth codecs: SBC, AAC, aptX
Quoted playback time: 25 hours BT+NC, 30 hours BT, 1000+ hours standby, passive cabled playback also available
Charging time: 5 hours
Weight: 250g