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I've been working with codecs for many years and I know that the same headphones don't sound the same on different phones, and I'll explain how to do that in the rest of the text. Now I will explain to you as simply as possible how codecs work. If you play a song on your phone and it is transmitted to the headphones via Bluetooth, the language they communicate with is audio codec. Because of that, when talking about bluetooth codecs, it does not only mean headphones or phones by themselves, but the shared system both devices use to compress and read audio data. In this example, I used the recently reviewed Tozo HT3 headphones. How I tested To see how the codec changes sound, I used three smartphones. I had the iPhone 14 Pro, Google Pixel 7 Pro, and Samsung Galaxy A23 in this test. I used them for listening and watched the results. Daily use test The first test was for normal daily use. I wanted to see if the basic SBC codec lowers sound quality. I did listening tests. I used the iPhone with AAC first, then the Android with LDAC, and then I compared both to the SBC fallback. One track I used for this test was "Billie Jean" by Michael Jackson. Complex music test The second test was for harder use. I wanted to see how much the codec changes clarity when you listen to complex music. For this, I played songs with many instruments. I used "Beat It" by Michael Jackson for this test. I set each phone to its default codec to keep it fair. I turned Wi Fi off to stop interference. So does the codec change the sound? Yes, it does. In my listening tests, the basic SBC codec used the same battery as LDAC, but the sound quality was lower. I found that AAC and LDAC gave more detail and wider sound than SBC. For a full song, SBC uses less data but also gives less fidelity. Using a basic codec might save a little battery but you lose detail. It is a small thing for most people, but you can hear it if you listen carefully. The phones were different. The Google Pixel 7 Pro with LDAC and the iPhone 14 Pro with AAC had the biggest difference from SBC. You could hear more clarity. The Samsung Galaxy A23 used a bit less battery but also had less detail. This is probably because of the phone hardware and software. What is clear is that battery use when idle is the same, but sound quality is not. The small battery difference is just margin of error. It does not matter if you use AAC, LDAC, or SBC. But in my listening tests, the devices showed a steady difference in sound quality. Again, it is small for casual use but it matters for serious listening. This shows that phones put Bluetooth to sleep when not in use, but the codec is still working when you play audio. You do not need to turn Bluetooth off, but you should check which codec is active. How much sound quality does the codec use? SBC does not really change battery life when on, but what about when you use Bluetooth on your phone? My listening test shows the same quality difference on all three devices. Comparing AAC and SBC shows a small drop in data rate but a clear drop in quality. It is small on paper but it means more quality loss than I first thought. This is likely because the devices were in use for a long time, and Bluetooth codecs do not always use high quality streaming. For a full battery charge, listening with SBC is a bit more power efficient by a small percent on average. It is small but not zero. But this kind of constant high quality streaming is not likely in the real world with signal problems. Phones are different. The iPhone 14 Pro had a steady, smooth sound with AAC. The Google Pixel 7 Pro was best for quality, with the most detail over hours. This difference is likely from phone hardware and software. The Pixel Tensor chip and iPhone A series chip do different audio processing than the other phone Snapdragon chip. Each Android software also has its own ways to handle Bluetooth audio. No two devices sound exactly the same, but they go from good to basic. Does a better codec use more battery? Many people use Bluetooth audio now because phones do not have headphone jacks. That is why I did these tests with audio playback as the main use. The results show that playing audio with a high quality codec uses about the same power as a basic codec. On average, the devices used a tiny bit more power with LDAC. This is well within margin of error. The iPhone 14 Pro and Pixel 7 Pro had no real difference in battery over four hours of listening in good conditions. This is because Bluetooth audio encoding runs on special chips in the phone. These chips use very little extra power for better codecs. At the same time, the phone audio circuits work the same way. This balances the power used by the Bluetooth chip. A stronger signal gives better quality. What I learned My test is not perfect and does not cover every Bluetooth use case. But it shows how the Bluetooth codec changes sound quality in general. Battery use is a bit different between codecs, but we are talking minutes of difference. The sound quality difference is what you can hear if you pay attention. You do not need to turn Bluetooth off, but if you care about sound, check which codec you are using. If you want better sound, use a better codec. Make sure your phone and your headphones both support the same good codec. If they do not support the same good codec, they will use SBC. And SBC does not give good sound quality. The codec makes a big difference in sound quality. The phone makes a big difference in sound quality. The headphones make a big difference in sound quality. But if the codec is not good, the headphones cannot sound good. And if the phone does not support a good codec, the headphones cannot sound good. So when you choose headphones, check the codec support. When you choose a phone, check the codec support. If you want the best sound, make sure both support the same high quality codec. If you do not check this, you might not get the sound you want. This is why I tested the same headphones on different phones. I wanted to show that the headphones are not the only thing that matters. The phone matters too. The codec matters too. And now you know how to check these things. You know that you should check the codec. You know that you should check the phone. And you know that you should make sure they work well together. That is the most important thing I learned. The phone and the headphones must work well together. If they do not work well together, the sound will not be good. If they work well together, the sound will be good. It is that simple.