70-Hour Battery Test: How Haylou FlowLoop S33 Headphones Challenge Expectations

Who’s after some ultra-durable noise-cancelling headphones for less than 50 bucks? Simple, reliable, decent-looking, but without any fuss or fancy tech. Just something that’ll last as long as possible and sound decent. That’s more or less how the Haylou FlowLoop S33 are marketed, but we don’t take their word for it and put them through their paces. Seriously, I’m prepared to spend 70 hours with a stopwatch to check whether they really do last that long. Read on to find out how it went.

4 reasons to buy the Haylou FlowLoop S33:

• very long battery life;
• adequate noise cancellation;
• pleasant and familiar sound with support for Hi-Res Audio and LDAC;
• a tried-and-tested, convenient foldable design.

3 reasons not to buy the Haylou FlowLoop S33:

• no analogue wired connection;
• not particularly audiophile-grade sound;
• only built-in microphones, with no option to connect an external one

What’s in the box?

An extremely simple package: the earphones and a USB cable. They don’t even include any information leaflets anymore (though who used to read them anyway?). One could criticise the lack of a carrying case, though to be fair, one is almost never included at this price point.

Contents of the Haylou FlowLoop S33 earphones. Image: gagadget.com

What do they look like?

Familiar, neutral, even a bit dull. These earphones won’t attract any unnecessary attention; everything here is utilitarian and practical. The model is available in black and white; the latter looks more interesting, but the former is more versatile.

All parts of the housing are made from matt plastic; it doesn’t show fingerprints and is pleasant to the touch, although it looks rather simple. The sides of the ear cups have a slightly different texture and a metallic colour, and feature the brand name.

The designers of the FlowLoop S33 didn’t try to reinvent the wheel and based the design on a popular and convenient transformable structure. The headband is adjustable by sliding the ear cups; the ear cups themselves rotate 90 degrees around a vertical axis for wearing around the neck and can fold inwards for compact transport. It’s familiar and straightforward.

All the controls are located on the right ear cup. These include the power button, the ANC button and the dual volume buttons, as well as a USB-C port. The buttons are made of a rubber-like material and are springy. They’re easy to reach and comfortable to press.

How do you connect and set them up?

The connection process is standard: whilst in pairing mode, select the headphones from the list of available Bluetooth devices on your smartphone or other audio source. The multipoint function is enabled by default: the headphones can be connected to two sources simultaneously. In this mode, the audio streams do not, of course, mix, but you can, for example, listen to music on your laptop and, without taking off the earphones or switching anything, answer a call on your phone. The headphones will automatically switch to the correct source provided both sources are connected, which is very convenient. There is also the option of a wired connection, but only a digital one – that is, via a USB-C cable – whilst there is no classic analogue mini-jack socket.

How do you control them?

There are two ways: using the buttons on the earbuds or via the Haylou Sound mobile app. You switch the earbuds on and off by holding down the power button; this button also controls ‘play/pause’ and answering calls. The volume is adjusted using the ‘plus’ and ‘minus’ buttons, whilst a double-tap on either of these buttons skips to the next or previous track. The buttons on the right earbud are conveniently positioned, and it’s easy to get used to them. The buttons feel solid to press, with a distinct click, and there are no accidental presses. The noise-cancelling modes can be cycled through using a dedicated ANC button (or via the app). 

How does noise cancellation work?

The Haylou FlowLoop S33 offers hybrid noise cancellation of up to 45 dB, with five microphones providing feedback. As we already know, a dedicated physical button allows you to switch between three modes: noise cancellation, transparency and off. In the third mode, the S33s function like ordinary earphones; in the second, rather than blocking out noise, they amplify ambient sounds so that you can hear them as if you weren’t wearing earphones at all. The noise-cancelling performance is typical for models in this class; the system is particularly good at filtering out low-frequency noise. The Haylou Sound app also offers a three-level adjustment for ANC intensity.

How do they sound?

The Haylou FlowLoop S33 uses 40-millimetre dynamic drivers, a fairly common solution in this class. They also feature Hi-Res Audio certification and LDAC support, which is no longer unusual in this price range. In practice, however, the sound is typical and average, which will suit most listeners in various scenarios. Even an expert in such matters would be hard-pressed to distinguish the type of rosin on a violin bow by ear. However, for everyday listening to music and making voice calls, these earphones are perfectly suited. Despite their closed-back design, there’s no bias towards the low frequencies; they’re quite distinct, yet at the same time soft, without any particular harshness. The dynamic range is pleasing for budget headphones; the soundstage isn’t particularly wide, but it is well-defined. The high frequencies may lack some nuance, but we’ll let that slide. If you wish, you can customise the sound to your liking using the simple equaliser in the Haylou Sound app, which offers several standard presets straight away (and you can even listen to nature sounds there). 

How comfortable are they?

The headphones are relatively lightweight (I weighed them at 245 g); wearing them for long periods doesn’t cause fatigue, but you do notice them, of course. Also, in hot weather, your ears will sweat a little – this is typical for closed-back headphones (though they’ll keep you warm in winter). The faux leather feels pleasant to the touch, and the memory foam padding also adds to the comfort, although there’s nothing particularly unique about that. The size adjustment is standard and straightforward; you can achieve a comfortable fit in a couple of seconds. I was pleased with the reliable connection to the audio source, which doesn’t drop out even behind concrete walls. Let’s put it this way: connection stability is clearly above average, and in these headphones it’s provided by Bluetooth 6.0.

What about battery life?

That’s the main selling point! We’re promised up to 100 hours of battery life without noise cancellation, or up to 70 hours with it. Of course, that’s under ideal conditions on the manufacturer’s test bench. Such impressive battery life is supposed to be provided by an 800 mAh battery and modern, energy-efficient internals. Well, shall we give it a go? For the test, I fully charged the earphones and set a timer whilst using them. I should point out straight away that this wasn’t a lab test, where the earphones are left idle with music playing quietly in the background, but real-world use with various types of content and phone calls. Of course, the downside of this method is the natural margin of error in the measurements, as your results will certainly be different. Well, the earphones lasted just over 55 hours for me under very demanding conditions: high volume, active noise cancellation, lots of on-off cycles, and frequent changes in distance from the sound source. I reckon that under ideal conditions, you could probably reach the claimed 70 hours, and without noise cancellation, you’d be close to the specified 100 hours. In practice, that’s a lot, and in most cases, you won’t need to worry about charging at all. Incidentally, charging takes up to three hours and, judging by the tester’s readings, it really does accept a full 800 mAh.

Haylou FlowLoop S33 and a bit of magic. Illustration: gagadget.com

The bottom line 

The Haylou FlowLoop S33 is a ‘mid-range’ mass-market model of wireless earphones; it offers the typical feature set for its class, adequate noise cancellation and a particular focus on battery life. With a neutral design, practical materials, a foldable build and convenient controls — just add a small carrying case and you’ve got a brilliant, affordable option for travelling. Perhaps influenced by the inevitable approach of autumn, I’d describe these headphones as ‘student-friendly’: hard-wearing, unpretentious and affordable. There are plenty of full-size headphones in the under-50-dollar range, but among the long-lasting models, the Ugreen Studio Pro is probably the closest competitor at the moment.

Three things you need to know about the Haylou FlowLoop S33:

• they are full-size closed-back headphones with Bluetooth headset functionality;
• they feature adaptive noise cancellation and the option of a wired connection via USB-C;
• they stand out thanks to their high-capacity battery and long battery life.