Very Basic Questions For a Beginner (Headphones)

[newguy358]

I've been lurking on a couple of audio & headphone forums for the past month and this seemed like a good place to avoid "subjective" answers for some more technical questions I have. I'm interested in buying a headphone for usage at home, especially during this COVID-19 situation. However, from my online research, it seems like if I want a headphone, I also need an Amp and DAC (My source will be my computer). I have some questions regarding that.

1. What is impedance matching? I read about a 1-8 ratio rule, is that a strict rule?
2. Different headphones have different power requirements, and it seems like the amount of power an amp can put out changes with impedance? So how do I know if an amp will work with a given headphone?
3. I'm having a hard time understanding the 320 kbps vs 16-bit vs 24 bit descriptions. And then there's the 16/44 or 16/48? For example, I understand that 320 Kbps > 256 Kbps, but how does that compare to the other formats that people mention?
4. What does an IEM/Headphone being out-of-phase mean? How does that sound?

Sorry for the long questions, I'm sure you get asked questions all the time. Any help is appreciated!

 

[maverickronin]

What is impedance matching? I read about a 1-8 ratio rule, is that a strict rule?

Basically the lower the output impedance of the amplifier the better as it reduces the impact of the amplifier on the headphone's frequency response. The 1:8 is more or less a rule of thumb for the limit of audibility.

Different headphones have different power requirements, and it seems like the amount of power an amp can put out changes with impedance? So how do I know if an amp will work with a given headphone?

Here's a handy power calculator.

I'm having a hard time understanding the 320 kbps vs 16-bit vs 24 bit descriptions. And then there's the 16/44 or 16/48? For example, I understand that 320 Kbps > 256 Kbps, but how does that compare to the other formats that people mention?

Bitrate (i.e. 320kbs, 256kbs, etc) as an indication of quality is only relevant to lossy codecs such as MP3 and AAC. These reduce size by throwing away the information you're least likely to hear. A high bitrate means it throws away less information and better codecs can make better decisions about what to throw away allowing better quality with the same bitrate.

Bit depth determines dynamic range, the range between the loudest and softest sounds. There are 6 decibels (dB) of dynamic range per bit. 16 bit is more or less the difference between a quiet room and a loud concert. 24 bit is the difference between the threshold of human hearing and immediate pain.

Sampling rate (44.1kHz, 48kHz, 96 kHz, etc) is twice the highest frequency of actual sound. Since young humans can't hear much over 20kHz and the limit only declines with age 16/44 is all you really need for most purposes.

What does an IEM/Headphone being out-of-phase mean? How does that sound?

I assume this means that one channel is out of phase from the other since that is where it's most obvious. It's kind of hard to describe, but it often just sounds "weird" doing strange things with the soundstage and imaging.

 

[somebodyelse]

Note that the quality at a given bit rate depends on the quality of the lossy codec too - 128kbps AAC or Opus will sound better than 128kbps MP3 for example.

'Standard' and 'hi res' versions of a recording often sound different simply because they're different mixes. If you take the 'hi res' track and use a decent sample rate converter to reduce it to 16/44 you probably won't hear any difference between them.

 

[Jimbob54]

Others have given comprehensive answers, I'll try the very layman one.
1. You'll get music playing. But if you're investing plenty $ on either phones or amp, worth bearing in mind the specs
2. Don't worry about it much. Unless going expensive or exotic. You'll get music out. But as with 1, buying a nicely powered but low output impedance amp might be your best bet.
3. Really don't worry.
4. Not a clue!

 

[newguy358]

Thanks everyone! You all really helped me clear things up, appreciate all the help.

 

[Fluffy]

The previous comments are excellent explanations, so I'll try to just bust some myths. You don't always need a DAC and an amp for headphones. There are plenty of headphones that works fine plugging into a phone or a laptop. It depends on the headphone and the device you're plugging it into. The best advice is first to find a headphone that sound good to you and is comfortable, and then check if you need to add any hardware to make it work well.

 

[nhatlam96]

More expensive doesnt always mean better sound

 

[Amperage]

Hello all. I've recently been wondering about this topic - specifically how much power do I really need for now and perhaps future IEM/headphone use. I'm currently running my head gear out of a FIIO KA15 dongle DAC, and so far, it's great. According to specs, it can do from 510mw per channel at 16 ohms down to to 78mw per channel at 300 ohms, balanced out.

While I don't have any very-high impedance headphones or IEM's at the moment, I'm now caught wondering if my HE400SE's specifically and with balanced cables could benefit from more power from a dedicated desktop amp like the JDS Labs Atom 2, which I'd feed from another DAC, and maybe future-proof my setup.

Is this even worth it for those headphones, or is the KA15 enough? Opinions appreciated!