Sony's flagship WF-1000XM5 earphones are currently ranked at the top of our list of best wireless earphones, and there is no doubt that they are capable of outstanding performance. As I mentioned in my review, the $299 (£259 / A$499) price tag seems high in today's economic climate, but they really are the best-sounding wireless earphones I've heard.

Still, there is no doubt that Sony's latest earphones offer an outstanding level of performance when listened to on high-quality media players like the Fiio M15S portable music player or the Sony Xperia 1 IV. Unfortunately, if you're listening to the Sony WF-1000XM5 earphones wirelessly connected to your iPhone, you're listening to the wrong thing. Let me explain.

As I mentioned in my review of Sony's WF-1000XM5, I was fortunate enough to be one of the first audio experts in the world to experience Sony's next-generation flagship wireless earphones. Although the miniaturized earphone design made for a poor fit, requiring me to increase the ear-tip size for an optimal fit, and some initial difficulties with 360 Reality Audio personalization, the Sony WF-1000XM5 wireless noise-canceling earbuds have become my favorite earbuds since I got them. Even after further testing and countless hours of listening, I remain strongly impressed. However, they are not for everyone.

Like the company's other headphones, these headphones come with an excellent user experience through the surprisingly comprehensive and well-crafted Sony Headphones Connect app. However, getting the best sound out of them is a catch-22 due to the type of Bluetooth codec the playback device is using. While it may sound rather boring, the codec and audio data transfer rate is one of the biggest determinants when evaluating sound quality.

My review revealed that I experienced the Sony WF-1000XM5 wireless noise-canceling earphones via a Sony Xperia 1 IV smartphone with LDAC support provided by Sony. The new Sony Bluetooth version is 5.3, which offers improved efficiency and more stable connectivity; with LDAC mode enabled on the Xperia smartphone, the sound quality of Sony's latest flagship earphones blew me away. Here's why.

Expressed in kbps (kilobits per second) of data transferred, Sony's LDAC offers a wireless streaming bit rate of up to 990 kbps over Bluetooth, while Apple's AAC (the highest iPhone-supported audio codec) is up to 320 kbps over Bluetooth.

When audio quality is considered in terms of the amount of data transferred between devices per second, AAC represents a compromise. Nevertheless, AAC is more sophisticated than the SBC Bluetooth codec and makes Bluetooth sound spectacular in many wireless audio products, such as Apple's AirPods Pro 2 wireless earphones for iPhone and AirPods Max wireless headphones. The Sony Xperia X2 is a wireless audio product that is being used in many wireless audio products.

The Sony XM5's ability to extract more information than most earphones I've heard is truly outstanding. The extra level of detail that could easily be missed with lesser earbuds was far more pronounced. I don't think that the frequency range is boosted in any particular area, but rather the amount of audio data being transferred allows the listener to capture the core of the song being played in a musical way without strain.

The new dynamic drivers of course have a role to play as well, processing different parts of the frequency range depending on the combination of materials, making nuanced instruments and vocals sound natural, convincing, and realistic, making you feel like you are in the front row of whatever it is you are listening to It makes you feel like you're in the front row of whatever you're listening to.

Listening to the exact same content from the Tidal HiFi playlist on the Sony WF-1000XM5 connected to an iPhone 12 Pro was not quite the same as listening to its full audio performance via an LDAC-enabled device. If anything, the new WF-1000XM5 doesn't sound like much of an improvement over Sony's previous-generation WF-1000XM4 wireless earphones. Naughty Sony.

I'm not saying the XM5 sounds bad on my iPhone. It's just that the sound is not as detailed in terms of being able to follow the different instrument parts and layers that make up the music mix. In comparison, the Bluetooth audio from my iPhone sounds less sophisticated, and as a result, the overall experience seems less immersive and engaging.

When testing any audio product, I always use the highest quality audio that the device can handle. That way, I get a sense of the full capabilities of the product before testing its performance with lower quality options.

It's a little disappointing that Sony's latest flagship earphones don't sound as great when connected to an iPhone using AAC, but a future firmware update to the Headphones Connect app sound tuning may be improved.

Sony has clearly designed the WF-1000XM5 earphones to perform best with LDAC, and the sound is exceptional. By using new dynamic speaker drivers, Sony has succeeded in highlighting the differences in sound quality between codecs, making the loss of sound quality when using lower kbps transfer rates more apparent. For me, if there is any reason to upgrade to a playback device that supports LDAC over Bluetooth, it would be Sony's WF-1000XM5. With proper playback, it offers the most audiophile-like listening experience I've had with wireless earbuds.