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high impedance headphones need a dedicated amp to sound good... please can we kill this myth? - Page 4

post #46 of 59
Thread Starter 
Quote:
Originally Posted by RazorJack View Post

I'd say low and high impedance headphones both need an amp to sound good, because headphone outputs on most devices are bad.

 

This isn't true. Look up measurements of iPods (the most popular device). The conclusion is always that they're surprisingly good. Look at the Sansa Clip+, it has fantastic measurements, and bests much more expensive headphone amps. Yet it sells for $40, and is tiny. Sure, the voltage swing may not be large enough to attain sufficient volume on very high impedance cans, but that is a different issue than it sounding bad. If your headphones cannot get loud enough, the headphone's specs do not pair with those of the amp. Those specs (power output of the amplifier, headphone impedance and sensitivity) are given by the manufacturer. But I rarely see anyone citing power ratings or mentioning sensitivity here. It has always been "high impedance headphones? BUY AN AMP NOW", as if something magical happens when an amplifier has it's own aluminum housing.

 

In my experience, many portable devices do have enough voltage swing for 300 ohm headphones with reasonable sensitivity. Many of these headphone companies realize that selling >600 ohm headphones with 50 db/mW is stupid because consumers use things like iPods primarily. Why do you think so few companies sell electrostatic headphones? They sound fantastic, but require substantial amplifiers. So I am not surprised that I can drive my HD600s well with every source I have. That is simply good engineering on Sennheiser's part.

 

A very low impedance headphone is much more likely to sound bad due to the source+amplifier than a high impedance headphone, but the opposite is constantly stated, which is why it is a myth. I've tried low impedance IEMs on my laptop... they sound absolutely terrible. They pickup all kinds of weird noises and sound super muddy... but you don't find people here saying that sensitive IEMs need a dedicated amplifier with low output impedance, do you?

post #47 of 59
Quote:
Originally Posted by Eisenhower View Post

Look at the Sansa Clip+, it has fantastic measurements, and bests much more expensive headphone amps.

 

You really need to run that past Voldemort. He has published the most comprehensive set of measurements on the Clip+ anywhere, but I doubt that even he will agree with your statement. Its about more than THD and IMD figures. 

post #48 of 59
Thread Starter 
Quote:
Originally Posted by estreeter View Post

 

You really need to run that past Voldemort. He has published the most comprehensive set of measurements on the Clip+ anywhere, but I doubt that even he will agree with your statement. Its about more than THD and IMD figures. 

 

Actually he would if you read his measurements.. I wasn't implying it'd be better than all more expensive amplifiers, but I can think of several revered designs it bests (AMB)

 

Here is what he said (note the part about not needing an amp):

 

"""""""""
THE MEASUREMENTS (brief version):


  • Frequency Response: Ruler flat from 10 hz to 20 Khz and very accurate
  • Distortion: Below 0.05% which most agree is inaudible
  • Maximum Output: About 15 mW--higher than average
  • Output Impedance: An extremely impressive 1 ohm (dedicated headphone amp territory)
  • DAC Performance: Impressive and better than many players costing several times more

NO HEADPHONE AMP REQUIRED: A headphone amp isn't likely to help much, and may do more harm considering how good the Clip+ already is by itself. It has plenty of clean output power to drive nearly any portable headphone likely to be used with a player like this. The unusually low output impedance means its performance is relatively unaffected by the headphones used. Unless you plan to use some oddball seriously inefficient headphones with an impedance higher than 64 ohms, or like uber-loud levels and long term hearing damage, you'll likely not get any significant benefit from using an amp and may end up less happy. An amp also defeats having such a small and light portable player.

"""""""""""""""


Edited by Eisenhower - 9/20/12 at 7:05am
post #49 of 59
Quote:
Originally Posted by Eisenhower View Post

A very low impedance headphone is much more likely to sound bad due to the source+amplifier than a high impedance headphone, but the opposite is constantly stated, which is why it is a myth. I've tried low impedance IEMs on my laptop... they sound absolutely terrible. They pickup all kinds of weird noises and sound super muddy... but you don't find people here saying that sensitive IEMs need a dedicated amplifier with low output impedance, do you?

 

That's probably because if it sounds bad out of a headphone output of a device, a separate amplifier using that polluted signal isn't going to make a difference, I actually think it will make things worse (from my experience). What you need in such a case is an external DAC as well, putting out a clean line level signal. Have you tried high impedance headphones with that same laptop? I'm sure you'll hear the exact same noises.

 

The headphone outputs of my Philips discman, Samsung smart TV, Soundblaster soundcard and Nokia Lumia 800 phone all sound like crap with both my (high impedance) beyerdynamic T1, and (very low impedance) el cheapo Chinese-imported-probably-fake Sony MDR-EX82 earbuds. There's background noise coming from all of them!

I would assume those are all reputable companies who should be able to afford halfway decent engineers, but apparently they can't... Or they just don't care because most users aren't audiophiles. Nice that Apple is an exception to that rule.

post #50 of 59
Quote:
Originally Posted by RazorJack View Post

That's probably because if it sounds bad out of a headphone output of a device, a separate amplifier using that polluted signal isn't going to make a difference, I actually think it will make things worse (from my experience). What you need in such a case is an external DAC as well, putting out a clean line level signal. Have you tried high impedance headphones with that same laptop? I'm sure you'll hear the exact same noises.

 

High impedance headphones will normally be less noisy, especially if the device uses digital volume control (not uncommon for onboard audio), so the noise voltage is the same but a less sensitive and/or higher impedance headphone produces lower noise SPL from it. I tried using relatively inefficient 250 Ω headphones from Realtek onboard audio, and there were no major problems with the sound quality after I fixed the grounding on the front panel.

post #51 of 59
Quote:
Originally Posted by RazorJack View Post

That's probably because if it sounds bad out of a headphone output of a device, a separate amplifier using that polluted signal isn't going to make a difference, I actually think it will make things worse (from my experience).

 

This is another very common myth. Using an external amplifier can in reality easily improve the sound quality, because:

- it may drive headphone loads better (more power, less distortion, lower output impedance, no undersized coupling capacitors on the output, etc.)

- its line input is much easier to drive than a headphone, eliminating the above mentioned problems at the output of the "low quality" device

- the source may be used at a fixed volume setting, where it has the best (or least bad, depending on your point of view) signal to noise ratio; this is most useful in the case of devices with digital volume control and sensitive headphones/IEMs


Edited by stv014 - 9/20/12 at 11:11am
post #52 of 59
Quote:
Originally Posted by stv014 View Post

 

High impedance headphones will normally be less noisy, especially if the device uses digital volume control (not uncommon for onboard audio), so the noise voltage is the same but a less sensitive and/or higher impedance headphone produces lower noise SPL from it. I tried using relatively inefficient 250 Ω headphones from Realtek onboard audio, and there were no major problems with the sound quality after I fixed the grounding on the front panel.

All onboard audio chips I had so far had hardware volume control which can be controlled conveniently through the system volume control. It looks like digital volume control but it isn't.

post #53 of 59

@stv014:

I was talking about the clearly audible background noise I'm hearing from my crappy sources and the weird noises being picked up from a laptop's headphone output, described by Eisenhower (which sound all too familiar to me as well). If an external amplifier fed from such a nasty source magically gets rid of that, it really is badly designed (in an interesting way).

 

The much bigger dynamic range of my T1 indeed made me perceive the noise floor seem lower than with earbuds, but still clearly present to my ears. I'm not sure how/if dynamic range is related to impedance though.

post #54 of 59

The reason for that is the (much) lower sensitivity (dB SPL @ 1 Vrms) of the Beyers.


Edited by xnor - 9/20/12 at 12:10pm
post #55 of 59
Quote:

Originally Posted by RazorJack View Post

 

I was talking about the clearly audible background noise I'm hearing from my crappy sources and the weird noises being picked up from a laptop's headphone output, described by Eisenhower (which sound all too familiar to me as well). If an external amplifier fed from such a nasty source magically gets rid of that, it really is badly designed (in an interesting way).

 

The much bigger dynamic range of my T1 indeed made me perceive the noise floor seem lower than with earbuds, but still clearly present to my ears. I'm not sure how/if dynamic range is related to impedance though.

 

If the noise/interference is added downstream of the volume control (regardless of whether is analog or digital), then its level does not depend on the volume setting. A less sensitive headphone will turn the same noise voltage into less audible noise. Since you have to turn up the volume more to achieve the same loudness, the dynamic range will increase, as the signal voltage is higher while the noise voltage does not increase proportionally. You have confirmed this with your comparison of the T1 and the ear buds. When the device is used as a line level source, the volume can be increased to the highest level that does not result in clipping.

post #56 of 59
Thread Starter 
Quote:
Originally Posted by RazorJack View Post

 

That's probably because if it sounds bad out of a headphone output of a device, a separate amplifier using that polluted signal isn't going to make a difference, I actually think it will make things worse (from my experience). What you need in such a case is an external DAC as well, putting out a clean line level signal. Have you tried high impedance headphones with that same laptop? I'm sure you'll hear the exact same noises.

 

The headphone outputs of my Philips discman, Samsung smart TV, Soundblaster soundcard and Nokia Lumia 800 phone all sound like crap with both my (high impedance) beyerdynamic T1, and (very low impedance) el cheapo Chinese-imported-probably-fake Sony MDR-EX82 earbuds. There's background noise coming from all of them!

I would assume those are all reputable companies who should be able to afford halfway decent engineers, but apparently they can't... Or they just don't care because most users aren't audiophiles. Nice that Apple is an exception to that rule.


Actually there is very little noise with my hd600's out of my macbook pro, and I never need to have the volume above the halfway mark because there is sufficient voltage from the built-in headphone amplifier.

I'd note that the hd600's have a lower sensitivity of 97 db/mW compared to 102 db/mW for your T1's. That might be part of it.

I'll concede that an amp won't always improve the noise with low impedance headphones - I tried a cmoy with those IEMs and it made no improvements noise-wise. But, it might improve the frequency response since the cmoy has a lower output impedance.

post #57 of 59

I just tried my HD650s running from my iPod Classic 160Gb and although the 650s still sound good, the sound doesn't have anywhere near the space that it does coming out of my Audio-gd NFB-5.2 which is essentially an entry level unit (combined DAC/amp).

 

So, to confirm, are we saying here that it's not necessarily the iPod not being powerful enough and that my experience here is more a case of the NFB-5.2 just being able to output better quality sound (i.e. not a reflection of power, just the quality of the individual components) and that the 650s are a good headphone that is able to make the most of higher quality sound.

 

In other words, what I'm hearing is that my KSC-75s won't sound massively better out of an amp because they are already producing close to their peak SQ out of the iPod, but higher quality items like my SE535s, HFI-680s and HD650s (all different impedance from 32-600 ohm) sound better out of the NFB-5.2 simply because it puts out better sound and the better quality phones are able to make the most of this.

 

Is that the gist of it?

post #58 of 59
Quote:
Originally Posted by Loquah View Post

I just tried my HD650s running from my iPod Classic 160Gb and although the 650s still sound good, the sound doesn't have anywhere near the space that it does coming out of my Audio-gd NFB-5.2 which is essentially an entry level unit (combined DAC/amp).

 

As already explained in this thread, for the comparison to be valid, you need to:

- match the levels accurately (within 0.1 dB); this is very important, even a small volume difference can produce the effects usually attributed to "better amping" (punchier bass, more dynamic sound, larger sound stage, etc.)

- test blind, eliminating all spurious clues that would allow for guessing which device you are listening to

- make sure that the iPod does not clip a 0 dBFS signal at the volume you perform the listening test at

post #59 of 59
I was pretty careful with my test of the classic amped and unamped with HD590s. The difference I found was dynamic punch. It wasn't a huge difference but it was noticeable. The volume on the iPod was very near full volume. I think the iPod's headphone out was just a bit underpowered.
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