[Listening test] Sennheiser Accentum earbuds and BTD-700 adapter

Product name: Sennheiser Accentum and BTD 700
Manufacturer: Sennheiser - Germany
Price: ±$150 (earbuds) - $50 (BTD700)
Reviewer: M.L. Gneier - TNT USA
Reviewed: October, 2025

When I first got started reviewing, and that was a long time ago, it wasn't easy getting review samples. So, I started out reviewing things like cables and connectors. Over time, it got easier to get review samples to the point when review samples were delivered by freight and I would come home only to find water heater-sized boxes blocking my driveway.

Of late, I have the sense of a circle closing. That's because this review is of what must be the smallest and lightest product I have ever reviewed, except, possibly, the Aurex Silver spades I reviewed back in the late 1980s. No, the Sennheiser BTD 700 is even lighter if not smaller.

Sennheiser is pretty vague about the tech of the BTD 700 and the supplied documentation for the product goes beyond minimal. The deeper I got into the product the more I realized it's real intention is for use in multi-receiver applications.

AI sums it up like this: “Auracast is a new Bluetooth standard (LE Audio) that allows users to broadcast audio from a personal device to an unlimited number of compatible nearby receivers, such as headphones, earbuds, and hearing aids. This technology enhances public audio experiences by streaming TV audio, public announcements, or even a friend's personal playlist directly to your own devices, improving accessibility and providing new ways to share audio privately.”

But, what interested me was the quiet promise of better Bluetooth sound. The BTD 700 achieved this, but it took some time. Turns out the Sennheiser's flagship Bluetooth headphones, the MOMENTUM 4, that I reviewed right here at TNT, are not compatible with Auracast. Odd. After chasing my tail for a good while, and enlisting Sennheiser's help in chasing said tail, I discovered that fact with a sigh of resignation.

Sennheiser was unfazed and promptly sent me a pair of their new ACCENTUM Bluetooth 5.3 / aptX /Auracast earbuds. How are they? Well, they're fine but the sound quality is not really on par with their price point. They have very shallow tips. The ANC is average. On the plus side they don't penetrate the ear canal as far as some other. On the minus side they don't feel especially secure in ear. The charging case is Ok (not too bulky) and allows for charging via USB-C and wirelessly. On the subject of charging, however, I must add that the ACCENTUM's sat around for about three days and would not charge either by wire or wirelessly. Then suddenly they started to charge normally. Then, from time to time and after a few minutes listening, the left earbud will go silent. What the?

Is it a coincidence that the only two Sennheiser products to ever give me functional woes are the two most recent? Who knows but after a short time the sonically-superb MOMENTUM 4 began to behave oddly. Their automatic power-on, power-off function, which worked perfectly out of the box, began to get glitchy. Sometimes the headphones will stay powered on, draining the battery. Other times, the MOMENTUM 4 need to be manually powered on and occasionally even re-synced, which is a pain. They still sound great, but...

But what about Auracast and the BTD 700? The truth is that once it's up and running the sound is quite impressive. The ACCENTUM sound more dynamic and there's better definition and dynamic performance using Auracast and the BTD 700. I never recommend bus powered USB devices, especially so-called USB headphone amps, because they are universally worthless. But, the BTD 700 is not an amplifier, thank goodness, and it does advance the ball when it comes to Bluetooth fidelity, if you're using a pair of Sennheiser headphones that support Auracast.

I'm left disappointed with Sennheiser, a company I have relied on for decades, surely longer than any other audio company. Whether the problem flows from R&D stress or simply the speed of developing tech advancements I get a sense of settling for less than the best in each of these three products. If you had asked me over the years which headphone company designed and built the most reliable products one name would have come to mind and that was Sennheiser. Hopefully there will come a day when I can honestly say that again.

(*) Reviewer's note on prices. Going forward, unless requested by the source of the review sample, I will refrain from including a price in my reviews. TNT is an international publication and our readers are fully capable of researching prices in their respective currency. If a price is noted in one of my reviews, be advised that it has been provided by TNT's editorial staff.

DISCLAIMER. TNT-Audio is neither a shop, nor a HiFi company or a repair laboratory for HiFi components. We don't sell anything. It is a 100% independent magazine that neither accepts advertising from companies nor requires readers to register or pay for subscriptions. If you wish, you can support our independent reviews via a PayPal donation. After publication of reviews, the authors do not retain samples other than on long-term loan for further evaluation or comparison with later-received gear. Hence, all contents are written free of any “editorial” or “advertising” influence, and all reviews in this publication, positive or negative, reflect the independent opinions of their respective authors. TNT-Audio will publish all manufacturer responses, subject to the reviewer's right to reply in turn.

The Sennheiser Accentum Earbuds and the BTD 700 Bluetooth USB adapter

Is Sennheiser pushing the boundaries of Bluetooth Fidelity?