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# Headphone & Amp Impedance Questions? Find the answers here! - Page 14

Many thanks for this post, very informative

Quote:
Originally Posted by proton007

Use this formula to calculate the power needed:

```Power = Antilog ( (Desired SPL - SPL per mW)/ 10).Note that a 3dB increase in SPL will cause a 2x increase in Power.For reference, 85 dB is considered to be the limit where long term exposure can cause hearing damage.Use 85dB to calculate the average power needed.
```

Dude, antilog? log base what? if log base 10 then the antilog(z) = the number x such that logx=z. So if this is base 10 then if log_10(x)=z, 10^z = x, or if base e then exp(z)=x; writing it like this is much less confusing then antilog(z), especially when otherwise the base is complete guesswork.

Using this formula in the way you describe leads me to believe that if your headphone sensitivity is greater than 85db/MW then you don't need an amp. Is this what you are trying to say? It doesn't matter what base the log because anything to the power of a negative number is less than 1, so as long as your amp can put out 1MW of power at your highest ohmage of your headphones then you're all fine and dandy.

e.g. if db/MW were 85 = desired SPL then antilog(0)=1, any base whatsoever; thus if an amp can supply 1MW at the peak impedane for my headphones (300ohms), then yahoo to the \$2 shop for an amp I go.

This would seem to go against all other advice I've ever heard.

What do you think? Have I calculated something wrong?

The figures are all decibels, so base 10 would seem like the most reasonable guess, right? (It's base 10)

For what it's worth, a lot of people listen with peak levels much above 85 dB SPL. Peaks being tens of dB higher than average levels isn't common on highly compressed loudness wars'd releases, but it is on other masters. Your amp should cover the peak levels, not just the average.

But yeah, unless you're listening pretty loudly the average levels are often achieved at well below 1 mW of power. After all, most headphones are in the 90s or 100s dB sPL / 1 mW range.

Edited by mikeaj - 2/7/14 at 12:54pm

Hi.

If I have a fiio e07k

220mw at 32 ohms

a headphone with 100 ohms impedance

100 db @100mw

i want 70 decibels ... What percentage should the amp be with a gain o 6db?

Learned a lot from this post, thank you.

I was reading over some of this thread at work and have a quick question. Have you guys ever run into the situation where the source seems to powerful for the headphones that you are using? Let me explain, I have a HisoundAudio Studio 3rd Aniversary and I usually use it with my Senn Amperiors, ATH M50, AKG K280. But when I hook it up to say my UE triple Fi 10's, I only can handle say, gaving it on volume 1, it is clear but too loud for me.

Its due to a higher sensitivity of the iem
Quote:
Originally Posted by KamijoIsMyHero

Its due to a higher sensitivity of the iem

That is what I thought after reading through this, just wanted to make sure I was not crazy or had overly sensitive ears.

Quote:
Originally Posted by red71rum

That is what I thought after reading through this, just wanted to make sure I was not crazy or had overly sensitive ears.

thats why a lot of portable devices don't need amps imo, i think amps nowadays are really just equalizer, (expensive equalizers)

abeit cleaner than the presets on the iphone etc.. but still most headphones (in the consumer market) are able to run fine off say an iphone/ s3 or whatever device usually.

nowww i use the fiio e6 with my re400 because it gives it just enough oomph on the bass and a bit emphasis on the lower treble without making it overblown. (none of the presets on my itouch can do that without screwing the rest of the sound up)

Lots of good info here. One question, will my Fidelio X1s sound better with an Astro Mixamp than my 470 Ohm headphone jack receiver? From what I understand, the receiver headphone impedance is too high for the X1s. Mixamp would be a better fit and has great Dolby Digital surround features for 360 / PS3.

You'd think getting a receiver to plug all your stuff into was an end-all-confusion solution... Now nothing will plug into my receiver, sigh.

very informative. thank you very much.

I just joined because I was interested specifically in this subject. I am not an audiophile, but I do like to have quality hardware to use for games. I had a really hard time following the OP because it is filled with science and that only confused me... I would appreciate someone could help me out and answer my questions in layman's terms/simple English, but I do understand some technical terms, which you will hopefully realize if you continue reading my post/reply.

I used to use Creative X-Fi Titanium with Astro A50s headset (SPDIF), which was a total net value of \$300. Now I use ASUS Xonar DGX (10ohms) running UNi drivers and Sennheiser HD-280 Pro (64ohms) headphones (analogue connection), which is a total net value of only \$150. However, my current setup is miles better in sound quality than my previous setup! I do not have the best sense of hearing, but I could tell that my current setup sounded much better and it was NOT a placebo effect. I can now hear sounds I never heard before and Sennheiser HD-280 Pro headphones are monitoring headphones, so they have no artificial bass or similar frequency boosters.

Since I am not big on audio, I am very content with what I have clarity-wise and sound-quality-wise. My problems rests in the fact that while I love Sennheiser HD-280 Pro headphones, I do not like Dolby Headphone positional audio that much due to high levels of reverberation and echo, even when used with an improved 7.1 Shifter profile that comes with UNi drivers. I heard SBX Pro solution in action/live and found it to be absolutely awesome and superior to Dolby Headphone. The trouble is that only Sound Blaster Z supports SBX Pro and Sound Blaster Z is rated at 22 ohms. My headphones are rated at 64ohms! That means there is a HUGE mismatch! Does that mean there is a big chance that I will frequently experience distorted sound? I am not into high volume and killing my ear-drums. I like medium-level sound that is pleasant and loud enough for me to hear footsteps behind me. Right now my ASUS Xonar DGX is rated at 10ohms, while headphones are at 64ohms. That is ALSO a mismatch, isn't it? Its not as drastic as it would be with Sound Blaster Z... I am not hearing any distortions and all frequencies sound very clear to me. But how could it also be a mismatch if ASUS Xonar DGX offers specific headphone options for headphones with sub-32ohms, 32-64ohms, and above 64 ohms? It obviously supports headphones with ohms less than 8x the soundcard ohms (10ohms)... Otherwise it would have options for headphone with 80ohms and above!!! So, I am at a loss as to whether I should get Sound Blaster Z or not. I know it would improve my positional audio experience, but it would worsen my overall quality sound, wouldn't it?

Can this issue be resolved with a cheap amp? Cheap, but good enough to be better than trying to match 22ohm Sound Blaster Z and 64ohm Sennheiser HD-280 Pro headphones. I am a bit confused about digital vs analogue signal in relation to impedance. Impedance does NOT affect digital signal, correct? Someone told me that I should get an amp and connect it to my Xonar DGX via SPDIF and then connect my headphones to the amp via analogue... Or maybe it would be cheaper to just upgrade my headphones to some above (8x22) 176 ohms?

All in all, I want to get to that SBX Pro sound without sacrificing the non-positional audio quality aspect for as little \$ as possible, be it with an amp or with new headphones... Of course, if the negative effect of mismatched 22ohm soundcard and 64ohm headphones is not that severe, then I may as well just get the Sound Blaster Z soundcard and be on way enjoying SBX Pro technology. Of course if you know how to reduce Dolby Headphone reverberation by some 50%, then it would be the best solution!!!

Sincerely,

The New Guy

Yeah, I'm not much a fan of Dolby Headphone either.

With respect to headphone impedance "mismatches" the effect on the sound is generally marginal on most sets. To be honest, it's more on the HD 280 than most headphones because the impedance vs. frequency plot looks like this:

source: InnerFidelity   http://www.innerfidelity.com/images/SennheiserHD280Pro.pdf

The effect with the 22 ohms on the Sound Blaster Z (I'm assuming you got this info from a good source and did not verify on my own) should be below a 2 dB swing in frequency response, giving effectively a slight bump in that 90 Hz range. Also, you'll get a little bit more nonlinear distortion. It'll affect the sound slightly but nothing I'd be actually concerned with.

The headphone options on the Asus sound cards seems to just limit the volume on some settings. It doesn't change anything really with regards to the hardware configuration or amplification. The labels for headphone impedance are some kind of gross oversimplification that veers into the "misleading" category.

This can be resolved by using a cheap amp, yes. If you already have a dedicated sound card I would use the analog output of the sound card and not the digital S/PDIF. If you use S/PDIF, you need something with S/PDIF input, which would be a device that also has a DAC inside. You only need an amplifier if you want something with lower output impedance to resolve this issue (or "issue").

Edited by mikeaj - 5/20/14 at 1:28pm
Thank you! The whole Dolby Headphone, CMSS-3D, SBX Pro deal is crazy. They are nothing, but feature licenses, capable of being applied to any soundcard, including onboard Realtek codecs... For example, top-end MSI Z97 Gaming motherboards use Realtek ALC1150 onboard audio, but licensed to produce SBX Pro Surround Sound, which is really the best surround sound solution out there. I bet my Xonar DGX can do it too, but it will never be licensed to do so...
Quote:
Originally Posted by mikeaj

source: InnerFidelity   http://www.innerfidelity.com/images/SennheiserHD280Pro.pdf

Holy crap, I just realized the title of the graph says it was measured with a 600 Ohm output impedance. Does this not artificially muck with the phase information?

Shouldn't this measurement be conducted with a source with as low as possible output impedance (it should be easy to find an amp with negligible output impedance compared to any headphone) and the current and current phase be measured as a function of frequency? I don't understand what a 600 ohm load is doing in there. Maybe somebody can help me out?

Cheers

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