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high impedance headphones need a dedicated amp to sound good... please can we kill this myth? - Page 2

post #16 of 59
9/17/12 at 7:03pm

Headphones may be insensitive. They may have a high impedance, or an impedance that varies a lot with frequency (most vary to some extent).

 

Headphone outputs can have problems driving headphones (to an adequate volume or with a flat frequency response) because of:

 

1 Inability to source sufficient current.

 

2 Inability to achieve sufficient voltage swing.

 

3 Too high an output impedance.

 

4 Any 2 or 3 of the above in combination.

 

Very rarely some headphones perform better with a high output impedance (some are designed to operate with 600 ohms out, an old standard), but an amplifier with good voltage and current capability can be made to appear as a high driving impedance by using a series resistor, whereas nothing can lower output impedance, or improve current or voltage performance other than an amplifier (OK, a transformer can, but let's not go there).

 

A headphone amplifier is not necessary in some instances and will not be an improvement in some instances, but often it will. It's the difficulty of defining and understanding the circumstances in which it will be an improvement that makes it a good recommendation in general, if the amplifier itself is of good quality (has good current and voltage and low output impedance in combination with low noise and distortion).

 

Put simply, it's easier to recommend trying a good amplifier than to explain to a naiive consumer with phones and a DAP of unknown quality how to figure out if he needs one, and owning one has the advantage of opening up the range of headphones he can expect to use successfully should he decide to buy different ones in future, so it's often chosen as an easy recommendation without any intent to mythologise.

 

w

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post #17 of 59
9/17/12 at 7:41pm
Thread Starter 
Quote:
Originally Posted by wakibaki View Post

Headphones may be insensitive. They may have a high impedance, or an impedance that varies a lot with frequency (most vary to some extent).

 

Headphone outputs can have problems driving headphones (to an adequate volume or with a flat frequency response) because of:

 

1 Inability to source sufficient current.

 

2 Inability to achieve sufficient voltage swing.

 

3 Too high an output impedance.

 

4 Any 2 or 3 of the above in combination.

 

A headphone amplifier is not necessary in some instances and will not be an improvement in some instances, but often it will. It's the difficulty of defining and understanding the circumstances in which it will be an improvement that makes it a good recommendation in general, if the amplifier itself is of good quality (has good current and voltage and low output impedance in combination with low noise and distortion).

 

Put simply, it's easier to recommend trying a good amplifier than to explain to a naiive consumer with phones and a DAP of unknown quality how to figure out if he needs one, and owning one has the advantage of opening up the range of headphones he can expect to use successfully should he decide to buy different ones in future, so it's often chosen as an easy recommendation without any intent to mythologise.

 

w

 

A low impedance headphone is more likely to cause distortion and fluctuations in the frequency response than a high impedance headphone due to current drain.

 

If there isn't enough voltage to drive a high impedance headphone, it will simply not get loud enough.

 

However, dedicated headphone amplifiers are constantly touted as being necessary for high impedance headphones to sound good. Anyone who has been here for a while should be familiar with this observation. The question is rarely "my headphones don't get loud enough" (distinct from not sounding good) because in that case a dedicated headphone amp is obviously needed. In fact, a newcomer would need no outside information to figure out that a headphone amplifier is the solution. But no, a dedicated amp is suggested to someone with a high impedance pair of cans for almost any sonic ailment - not enough soundstage, poor bass response, poor midrange, poor treble, sterile sounding, too warm sounding, etc...

 

It might be the case that the built-in headphone amplifier simply sucks, and distorts all over and substantially colors the sound. But with reputable companies who can afford halfway decent engineers, I don't see how this would be likely. I'm not knocking anyone suggests getting a dedicated headphone amp, since it can help, but it isn't suggested as much as it's demanded.


Edited by Eisenhower - 9/17/12 at 7:55pm
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post #18 of 59
9/17/12 at 7:54pm
The volume output of the iPod isn't huge with any cans. But bypassing the headphone out will result in a small improvement in sound quality on early gens. That's another reason amping helps.
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post #19 of 59
9/17/12 at 8:27pm

If the sole purpose of an amplifier was to make music 'louderer', I might be able to see the point of this thread. Just as I wouldnt hook a 4-ohm speaker to a fleawatt speaker amp and expect good results, I'm not going to plug 600-ohm cans - or insensitive orthos - into an iPod and expect anything close to optimum results. Its about scale and impact, and its about the point at which clipping degrades your enjoyment of the music. I know the difference between my old K601's amped and unamped - I dont need to see frequency graphs on this one. No myth here.

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post #20 of 59
9/18/12 at 3:58am
Quote:
Originally Posted by Loquah View Post

So does this mean that they need more power because of being less sensitive than other cans (e.g. SRH840s) and therefore don't have the headroom to create the same dynamics as a more sensitive headphone?

Not necessarily more power, just more voltage.

 

 

Quote:
Originally Posted by Eisenhower View Post

However, dedicated headphone amplifiers are constantly touted as being necessary for high impedance headphones to sound good.

Dunno why, these guys probably equate sound quality with volume.

 

 

Quote:
Originally Posted by estreeter View Post

If the sole purpose of an amplifier was to make music 'louderer', I might be able to see the point of this thread. Just as I wouldnt hook a 4-ohm speaker to a fleawatt speaker amp and expect good results, I'm not going to plug 600-ohm cans - or insensitive orthos - into an iPod and expect anything close to optimum results. Its about scale and impact, and its about the point at which clipping degrades your enjoyment of the music. I know the difference between my old K601's amped and unamped - I dont need to see frequency graphs on this one. No myth here.

How'd you call an amp with flat and wide frequency response, sufficient gain, low distortion and low noise? I'm not alone to call that "wire with gain".

Whether 600 ohm cans are loud enough with an iPod depends on the sensitivity of the headphones, the genre/dynamic range of the music you're listening to, EU-limited output voltage .. Similarly a small amp might be enough for a 4-ohm speaker in the nearfield. To quote Dick Olsher: “The first watt is the most important watt.” Just like the first milliwatt is the most important one with headphones.


Edited by xnor - 9/18/12 at 3:59am
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post #21 of 59
9/18/12 at 10:31am
Quote:
Originally Posted by Eisenhower View Post

It might be the case that the built-in headphone amplifier simply sucks, and distorts all over and substantially colors the sound. But with reputable companies who can afford halfway decent engineers, I don't see how this would be likely. 

 

I think this actually is the case.

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post #22 of 59
9/18/12 at 1:02pm
Quote:
Originally Posted by Eisenhower View Post

 

It might be the case that the built-in headphone amplifier simply sucks, and distorts all over and substantially colors the sound. But with reputable companies who can afford halfway decent engineers, I don't see how this would be likely.

 

You need to work on your cynicism a bit.

 

50 years ago 'hi-fi' was all science-based. Now 99% of 'audio' is mythology. Apart from the stuff bought by ordinary consumers who have the good sense to know hype when they see it. I don't mean Beats by Dr. Dre.

 

I don't like it any more than you do, but there's no sense in getting your knickers in a twist. Let it all wash over you.

 

w

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post #23 of 59
9/18/12 at 1:51pm
Quote:
Originally Posted by xnor View Post

How'd you call an amp with flat and wide frequency response, sufficient gain, low distortion and low noise? I'm not alone to call that "wire with gain".

Whether 600 ohm cans are loud enough with an iPod depends on the sensitivity of the headphones, the genre/dynamic range of the music you're listening to, EU-limited output voltage .. Similarly a small amp might be enough for a 4-ohm speaker in the nearfield. To quote Dick Olsher: “The first watt is the most important watt.” Just like the first milliwatt is the most important one with headphones.

 

Just beg/borrow/steal a pair of K601/K701/600-ohm Beyers from someone and plug them into the headphone out on an iPod. You will hear music, sure, but will you hear what the headphones are capable of sonically ? My opinion is that it wont even be close. 

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post #24 of 59
9/18/12 at 2:24pm
Quote:
Originally Posted by estreeter View Post

Just beg/borrow/steal a pair of K601/K701/600-ohm Beyers from someone and plug them into the headphone out on an iPod. You will hear music, sure, but will you hear what the headphones are capable of sonically ? My opinion is that it wont even be close. 

 

Sounds fine to me, aside from being too quiet on music that is recorded well (the kind that might be more revealing of issues)... but then again, I didn't do any volume matched, blinded comparisons.  You also might not hear what they are capable of without the proper listening volume.

 

K701 is kind of not that "high impedance" though.

 

 

Even if not blinded, maybe it could be useful to rig up a switchbox where one option is a source and the other option runs the source through a good amp set to unity gain (hopefully with good channel tracking or optimally no volume control).

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post #25 of 59
9/18/12 at 2:31pm
Since we are discussing power; does anyone thing HE-500 really need 1w amp like its stated on their website? I use them with Auditor which was made for high impedance cans and I think it sounds very nice.
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post #26 of 59
9/18/12 at 2:47pm
Quote:
Originally Posted by .Sup View Post

Since we are discussing power; does anyone thing HE-500 really need 1w amp like its stated on their website? I use them with Auditor which was made for high impedance cans and I think it sounds very nice.

 

Where does it say that?  (maybe I'm not checking the right part of the website)

 

As always, what's that mean?  It depends on the listening volume.  If you suppose that Tyll's setup is reasonably accurate, HE-500 need about 2.04 mW for 90 dB SPL, according to InnerFidelity.  That's in the ballpark of HiFiMAN's figures too.  1W would make for about 117 dB SPL, supposing they can actually handle that much power without running out of excursion—quite arguably, pretty excessive.

 

Maybe the hope is just that amplifiers that are claimed to be capable of 1W into... some load (sometimes load is not specified for output power ratings, or customers don't understand the difference here), can actually do some certain amount that is sufficient for most listeners with those headphones.  Sometimes it's better to just overestimate so you can pass the buck, or to oversimplify explanations.

 

I mean, if you're not running them to 1W and have no desire to run them that loud, you don't need something capable of 1W.  And that's that.

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post #27 of 59
9/18/12 at 2:49pm

Beaten by mikeaj, good reply.

 

1W will make HE500s put out 119 dB, which will make you deaf very quickly.

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post #28 of 59
9/18/12 at 3:07pm
Quote:
Originally Posted by mikeaj View Post

Where does it say that?  (maybe I'm not checking the right part of the website)

As always, what's that mean?  It depends on the listening volume.  If you suppose that Tyll's setup is reasonably accurate, HE-500 need about 2.04 mW for 90 dB SPL, according to InnerFidelity.  That's in the ballpark of HiFiMAN's figures too.  1W would make for about 117 dB SPL, supposing they can actually handle that much power without running out of excursion—quite arguably, pretty excessive.

Maybe the hope is just that amplifiers that are claimed to be capable of 1W into... some load (sometimes load is not specified for output power ratings, or customers don't understand the difference here), can actually do some certain amount that is sufficient for most listeners with those headphones.  Sometimes it's better to just overestimate so you can pass the buck, or to oversimplify explanations.

I mean, if you're not running them to 1W and have no desire to run them that loud, you don't need something capable of 1W.  And that's that.
Thanks for an interesting but logical response. I never go over 8-9 o 'clock on my amp. The website says its "89dB sensitivity " and my pair has 46 ohm. Anyway this could be calculated into required watts?
Edited by .Sup - 9/18/12 at 3:08pm
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post #29 of 59
9/18/12 at 3:20pm
Quote:
Originally Posted by .Sup View Post

Thanks for an interesting but logical response. I never go over 8-9 o 'clock on my amp. The website says its "89dB sensitivity " and my pair has 46 ohm. Anyway this could be calculated into required watts?

 

That sensitivity figure is probably shorthand for 89 dB SPL / 1 mW—give the thing 1 mW electrical power, and you get 89 dB sound pressure level.  Give it ten times more power, and you get ten more dB.  That would be 99 dB SPL / 10 mW, 109 dB SPL / 100 mW, 79 dB SPL / 0.1 mW, etc.  This figure may not be perfectly accurate, and it probably depends slightly on your particular sample.  Tyll's figure is a little off from that, for example.

 

So for X dB SPL, it requires 10^[(X-89) / 10] milliwatts of power.  For 75 dB SPL, that would be 10^[(75-89) / 10] = 10^[-1.4] = 0.0398 mW.

 

1000 mW = 1 W of course.  Hopefully my brain is still functional at this time of day, and I didn't screw anything easy up (edit: did typo 75 into 74).  You never know.


Edited by mikeaj - 9/18/12 at 3:56pm
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post #30 of 59
9/18/12 at 3:27pm
Very grateful for that info, I now know more. Thank you!
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