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Topic: HD650 Headphones request (Read 8721 times) previous topic - next topic
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HD650 Headphones request

Apologies in advance for a selfish topic.


I'm looking for legitimate (double blind, matched volume) tests of Sennheiser HD650 headphones done with and without dedicated AMPs or DACs vs say, the standard output on an iPod or a media dedicated Laptop. I got into an argument awhile ago with some people who insist that I'm somehow wasting my headphones with inferior equipment. I have used a separate AMP before, but other than unnecessary increased volume I didn't notice anything better about it.

When I do a search on this forum invariably the answer seems to be 'if the volume is enough, then you don't need an AMP.' However, if you do a search on the HD650 you also find a tonne of threads with people making unsupported (but also unpunished) statements that the HD650 somehow need an AMP. The people I got into an argument with pointed to these threads as if they were fact. I know it shouldn't bother me, but it's been like a monkey on my back since, and a kind of negative placebo when listening to music.

I can say the volume is enough for me, but really I think the volume would be enough for anyone if I were giving advice. I've listened to lower impedance headphones and earphones... It seems like the only reason earphones with low impedance can sound stupidly loud, is because the driver is actually in your ear. When I've tried headphones with 16 ohms of impedance, it wasn't as obviously louder as it probably should be if impedance makes the huge difference people claim it does. I hope saying that doesn't violate your rules... I'm just saying the difference between 16 ohms and 300 isn't immediately apparent (as people claim it is) volume wise.


Basically what I'm trying to find is legitimate reason to believe my iPod is somehow not getting the most out of my headphones. I know the burden of proof isn't on me, but it would be something nice to quote the next time someone tells me I'm an idiot for letting my iPod be the weakest link. Information that says it doesn't matter is obviously great too.

HD650 Headphones request

Reply #1 –
Impedance alone doesn't make it louder/less loud, sensitivity also plays a part, so sometimes there's not the difference you should expect when using such different impedances.

HD650 Headphones request

Reply #2 –
Why not quote engineering mathematics?  Ask somebody to demonstrate, using established engineering principles, that you need some special (read: expensive) equipment to drive the HD650.  Nobody will be able to do much more than say "It's so obvious when I used my amp, DAC, cables, balanced, etc.  I don't need science to tell me what I'm hearing..."

I've done volume matched tests between amps and DACs with a range of headphones.  The only time I've been able to establish the NEED for a seperate amp was with the 600 ohm AKG 240DF, a headphone with very low sensitivity.  Even with a basic 9V battery powered amp it started distorting during large dynamic swings in certain genre's of music.  For other genres (e.g. modern pop music which are very loud in the recording) one could get by with just a computer sound card.

Quote
Basically what I'm trying to find is legitimate reason to believe my iPod is somehow not getting the most out of my headphones


I doubt you'll find any legitimate reason unless you consider "I know I can hear a night and day difference when I use X equipment" a legitimate reason.

HD650 Headphones request

Reply #3 –
Ah, thanks a tonne

Did you happen to record your method and observations for your experiments? If you did, and you're willing, I'd like very much to read them.

By legitimate reason I mean one that respects scientific method and still reports that a user can tell the difference without the answers being right in front of him or her. I don't think it's likely I'll find anything either, but it'd be nice to have a reason not to believe something, as absurd as that really is.

HD650 Headphones request

Reply #4 –
I'll write something up.  I've mentioned some of my experiments in past threads on HA.  I'll be traveling for a few days so it'll me a few days to post a basic procedure of what I did.  I know I've outlined the basic procedure in another thread but I can't find it right now.



HD650 Headphones request

Reply #5 –
Keen to hear it. Although it sounds a little unfair being written after the fact, I'd like to reproduce it on my own at least. So far all I can think of as a means to ABX and amplifier is to get a friend to roll dice and plug the cord without me knowing where it goes. I can't figure out how to match the sounds, or what special equipment and know how I'd need to do so.

HD650 Headphones request

Reply #6 –
Impedance matching is important for SOME headphones.  In my experience, the HD600's, a cousin of the HD650's, sound rather thin when played through a 5th generation iPod.  My triplefi10's sound completely different (frequency response) based on what they're plugged into.  I get a night and day difference when run straight from the iPod, laptop headphones output, Mbox, and Mackie mixer.  Oddly enough, they sound best when they're plugged into the laptop, which has poor sound quality in general.

- Rob

HD650 Headphones request

Reply #7 –
Quote from: LocrianGroove on
Impedance matching is important for SOME headphones.  In my experience, the HD600's, a cousin of the HD650's, sound rather thin when played through a 5th generation iPod.


The HD600s have a 300 ohm impedance, while your iPod has an impedance of less then 1 ohm.  What exactly are you expecting to impedance match to your ipod?

HD650 Headphones request

Reply #8 –
You should post this also on head-fi, Chef.

The occupants of this forum are in general quite quick to poo-poo anything remotely 'audiophile', so it's really no surprise that almost everyone is telling you you don't need an expensive special equipment. Asking somewhere like head-fi may provide the opposing argument you won't necessarily see here. I think its good to hear all sides of an debate.

That said, my advice is to just buy a amp (and dac?) in your price range, do your own experiments and make your own decisions. A lot of places seem to have 30-day returns now even over the internet, so for 15 bucks in shipping you can save yourself the uncertainty of relying on others to tell you what you can and cannot hear.

- Qest

HD650 Headphones request

Reply #9 –
Quote from: Mike Giacomelli on
Quote from: LocrianGroove on
Impedance matching is important for SOME headphones.  In my experience, the HD600's, a cousin of the HD650's, sound rather thin when played through a 5th generation iPod.


The HD600s have a 300 ohm impedance, while your iPod has an impedance of less then 1 ohm.  What exactly are you expecting to impedance match to your ipod?



Not sure what the issue is with the HD600's and my iPod.  Any idea about what I said about the triplefi10's?

HD650 Headphones request

Reply #10 –
Quote from: Chef on
Keen to hear it. Although it sounds a little unfair being written after the fact, I'd like to reproduce it on my own at least. So far all I can think of as a means to ABX and amplifier is to get a friend to roll dice and plug the cord without me knowing where it goes.


That's one possible way.

If you have a decent ADC you also can record the output from the amplifiers (loaded with headphones, through a passive splitter) and then ABX the recorded files on your own.

Quote
I can't figure out how to match the sounds, or what special equipment and know how I'd need to do so.


You will need a passive splitter (Y-adapter) and a voltmeter able to measure alterating voltage (any cheap digital multimeter should do fine). You will also need a test tone generator (1 kHz sine wave). The test tone can be generated from computer with e.g. foobar2000 or with some audio editing software.

Connect the phones to the amplifier through splitter. Adjust the volume with the amplifier volume control to comfortable level for the recordings you plan to use for ABX test. Then feed the test tone to the amplifier input. Measure the voltage on the second output of Y-adapter (without disconnecting the phones). This may be somewhat challenging - you will probably need a piece of cable with minijack on one end and stripped wires on the other (the minijack-to-RCA cable also may work). Be sure that your multimeter is set to measure AC voltage, not DC voltage. It is sufficient to measure one channel (say left). Write down the obtained value (it probably will be below or somewhere near 1 V). When testing other amplifiers, you will need to adjust their output to this value, using the same procedure (headphones attached through splitter, the test tone is fed into the amplifier, the voltage is measured at the second output of the splitter). The adjustment accuracy should be about plus-minus 5% of the initially measured value or better.

When the volumes are matched as described above, you are ready to perform an ABX test with the recordings of your choice.

HD650 Headphones request

Reply #11 –
Quote from: LocrianGroove on
Not sure what the issue is with the HD600's and my iPod.  Any idea about what I said about the triplefi10's?


Perhaps you cannot drive them to the equivalent volume that do you with a mixer?  You should volume match when trying to explore these audible differences.

As for the issue with the triple fi's, I've believe I've responded to why this may be happening in a thread you created asking specifically about this.

HD650 Headphones request

Reply #12 –
Quote from: Qest on
You should post this also on head-fi, Chef.

The occupants of this forum are in general quite quick to poo-poo anything remotely 'audiophile', so it's really no surprise that almost everyone is telling you you don't need an expensive special equipment. Asking somewhere like head-fi may provide the opposing argument you won't necessarily see here. I think its good to hear all sides of an debate.

That said, my advice is to just buy a amp (and dac?) in your price range, do your own experiments and make your own decisions. A lot of places seem to have 30-day returns now even over the internet, so for 15 bucks in shipping you can save yourself the uncertainty of relying on others to tell you what you can and cannot hear.

- Qest

The point of looking for studies is so that I can avoid spending money unnecessarily... If I just buy a DAC or AMP randomly I'll end up getting a negative result and thinking 'oh... maybe I just didn't spend enough money.' I've used an old stereophonic receiver before which was free, and at the time I was using it I was reading a lot of head-fi and believed adamantly that it was improving the quality of the sound... But later as I started experimenting listening with and without, while also being very skeptical about its powers from further research, I realised it wasn't very obvious at all, if there was a difference. The thing was huge and inconvenient anyway, so I put it back into storage. It even gave feedback if I set the volume too high, and I hear odd sparking sounds occasionally that I don't hear with my iPod, which I assume had something to do with the jack slot. So if I go from free to spending 200 dollars on some amp, I do myself huge discredit I think... I have the money to spend, but not so much money that I want to risk paying for junk, or forcing myself into buyers remorse where I no longer care about real world results because even a placebo is better than 200 dollar right down the drain.

I'm not really willing to pseudo rent amplifiers and dacs either while trying to rely on a return policy that is probably voided by such practice

HD650 Headphones request

Reply #13 –
Quote from: Qest on
Asking somewhere like head-fi may provide the opposing argument you won't necessarily see here. I think its good to hear all sides of an debate.

Yeah, it's like going to the town drunk for advice on staying sober.  Good idea! 

HD650 Headphones request

Reply #14 –
Quote from: odigg on
Quote from: LocrianGroove on
Not sure what the issue is with the HD600's and my iPod.  Any idea about what I said about the triplefi10's?

As for the issue with the triple fi's, I've believe I've responded to why this may be happening in a thread you created asking specifically about this.


I looked at the thread I created, and I completely forgot I had asked that question.  My memory must be flaky.  Anyway, thanks for responding to my question.

HD650 Headphones request

Reply #15 –
Quote from: greynol on
Quote from: Qest on
Asking somewhere like head-fi may provide the opposing argument you won't necessarily see here. I think its good to hear all sides of an debate.
Yeah, it's like going to the town drunk for advice on staying sober.  Good idea! 

Case and point.

Quote from: Chef on
I've used an old stereophonic receiver before which was free, and at the time I was using it I was reading a lot of head-fi and believed adamantly that it was improving the quality of the sound... But later as I started experimenting listening with and without, while also being very skeptical about its powers from further research, I realised it wasn't very obvious at all, if there was a difference. The thing was huge and inconvenient anyway, so I put it back into storage. It even gave feedback if I set the volume too high, and I hear odd sparking sounds occasionally that I don't hear with my iPod, which I assume had something to do with the jack slot.

You may not want to draw general conclusions based on what sounds like a pretty poor receiver.

Quote from: Chef on
I'm not really willing to pseudo rent amplifiers and dacs either while trying to rely on a return policy that is probably voided by such practice

I've never had trouble returning components before, though either way I have to concede that it's a lot of work just to test something.

Alternatively you could consider going to some local high-end audio stores and bringing along some CDs and your headphones. Though it seems to me most stores don't have any of the stuff I would actually want to buy, 'audiophile' preamps seem to have decent headphone amps and overpriced dacs are common enough. If you try the best components you can find, then you at least know whether this stuff can realistically make a difference. If you find it doesn't then you're done and if you find it does then you you can decide whether to jump on board or not.

It's also a fun way to spend an afternoon .

- Qest

HD650 Headphones request

Reply #16 –
Here we go!

alexeysp gave a fairly good description of what you need to do.  I'm probably just repeating him, but this is what I did.

Hardware used.

1. At least one stereo Y-splitter.  I recommend two to save time.
2. Four 3.5 mm male to male stereo cables.
3. Various 3.5 to 1/4 (and vise versa) inch stereo plug converters.
4. Switching box (described below).
5. Multi-meter.

I also made a small switching box.  This consists on two 3.5 mm female stereo jacks (inputs), a toggle switch to switch between inputs, and a 1/4 female stereo jack (output).  Using this device I can switch between inputs with a simple flip of the toggle switch.

Here is how I compared amps.  First, I would plug the stereo Y-splitter into my source (DAC, sound card, etc).  Then I would connect both amps to this Y splitter so that the same signal is going to both amplifiers.  Then I would plug my headphones (I've tested a lot of them) into into one amp, play a song, and pick my preferred listening volume.

Now it is time to volume match.

I would now unplug my headphones from the amp and plug a Y-splitter (different from the one you are using at the source) into the amp.  My headphone would go into one end of the Y-splitter.  A male to male stereo cable would go into the other end of the y-splitter.  It's very important to volume match when the amp is loaded (headphones are plugged in) with headphones.

I then played a 1khz tone (I have a 1khz tone .wav file) and attached my multimeter to the male to male stereo cable attached to the amp via the y-splitter.  I measured the voltage and wrote it down.

I then moved the Y-splitter (headphone and male to male cable attached) from the first amp to the second amp.  I repeated the procedure with the 1khz signal and adjusted the volume on the second amp so I had a near identical voltage reading on both amplifiers when the 1khz was is playing.

At this point you can now connect the two amps and headphones to the switching box.  Play some music and compare the sound as you switch between amps via the toggle swtich.

Comparing two DACs or sources is harder since you may also need two amps.  There is also the issue of time synchronization since you need to send the music to two sources.  I usually just used two music players (Foobar and VLC), made sure to disable all effects, and played the same song in both players.  Foobar was set to output to one source and VLC to the other.

When using a computer to playback, I could lineup the two media players quite well, meaning I could switch between sources (using the switching box) in a way that seemed nearly transparent in a time sense.  This is harder if you use two portable players or devices along those lines.

Hopefully by this point you have the general idea of how to volume match two sources (you can use two amps or one amp and set the volume in the software media players).  If not, let me know. 

As for doing it blinded, I quickly discovered there was no need to.  I could rarely tell the differences between sources, amps, etc when doing volume matched tests in this manner.  When I did, the differences emerged due to differences that are well understood in engineering.  These differences also appeared in RMAA measurements.

When I did feel the need to do it blind (when I heard differences) I would carefully repeat the volume match then just close my eyes, unplug the cables going into the splitter box, toss them around, plug them back in, and open my eyes.  I would then start playing the music without the headphones on my ears so I wouldn't know which player was connected to what.

This is a flawed "blind" test but I never saw the need to improve it because I never found results that contradicted the usual findings in blind tests.

I'll write up my general findings a little later.  Please let me know if you have any questions.

HD650 Headphones request

Reply #17 –
Thanks ! I'm going to save your post into a txt file for future reference. It's very generous of you to post such a detailed description and I appreciate it a lot!

I will check back when you've written your general findings as well. I respect the law of large numbers very much, so the more studies as I can read pointing to similar conclusions, the more confident I will be it putting the issue to rest. I'll save them too, in case I can find someone like me and save them some time searching

HD650 Headphones request

Reply #18 –
I've tested a lot of different headphone related gear and headphones.  For the most part I've stopped doing volume matched tests because I typically came up with similar results each time.  Now I mostly just compare headphones 

I also had quite a lot of collaboration with another Head-Fi'er in the EU who has done volume matched tests with expensive ($1K+) gear that is easier to get in the EU than it is in the USA.  His findings mirror mine.  I've also had short conversations with with other Head-Fi members who have done volume matched tests and come to similar conclusions.

If you want some links, here are some.

A site with a lot of different blind volume matches tests on speaker eqiupment - http://www.matrixhifi.com/ENG_index.htm
A post from a thread where a Head-Fi member did some volume matched tests for the first time.  If you look at the threads that person (upstateguy) has started you'll find a number of comments about volume matched blind testing.

Finally, my conclusions from my experiments.

1.  I don't even think about audible differences in DACs anymore.  If I buy a DAC it'll be some pro-audio DAC (e.g. EMU 0404, Echo Audiofire 4) that can also record audio.  If I do buy a DAC simply for stereo listening, I'll just buy something inexpensive like the Behringer 202 ($30 street price).  If I'm using a CD Player, PMP (e.g. IPOD), etc I don't much think about using any DAC beyond what is built into the device.

2. Amplifiers require a little more thought, but not much.  I've found that the one should look at the output impedance of a headphone amp when buying a headphone amp.  A headphone amp with a near 0 output impedance can drive most anything with a flat frequency response. 

Headphones amps with a higher than zero output impedance (e.g. 50 ohms) will change the output frequency response with low impedance headphones.  This difference may or may not be audible.  For example, the Presonus HP4 (50 ohms output impedance?) adds a measurable and audible bass boost to the 25 ohm Denon D7000.  It adds a measurable but mostly inaudible bass boost to the ~60ohm AKG K702.  Beyond 70 ohms it's not really an issue for full sized headphones.

Some AV receivers have very high output impedances.  This can change the FR of even high impedance headphones, but it may not be audible.

3. Thanks to shigzeo, I've now learned that IEMs with multiple drivers have impedance that can vary greatly over the FR range.  This will result in audible and measurable differences between amplifiers with a higher than 0 output impedance.

The solution is simple - get an amplifier with a near 0 output impedance.  This can be a little complex as I suspect some headphone amp manufacturers are not accurately reporting output impedance.  Shigzeo actually discovered that the IPOD can drive these multi-BA IEMs better (with a flatter FR) than many headphone amps!

4. The only time an dedicated amp is NEEDED is when your device cannot drive your headphones to your desired volume levels or if you cannot get to your desired volume levels without distortion.  An amplifier will not add any "sound quality" to your portable music player, but it can seem so since it's easier to listen to louder volumes (thus feel the sound quality has improved) with an amp.

One thing to keep in mind is that many headphone listeners (I know this from Headphone meets and meeting other headphone lovers) listen at volumes that I find painfully loud.  I suspect many people are listening at volumes that are detrimental to the health of their ears.  These people need an amp to drive headphones to their preferred volume levels without distortion.

IMHO the easier (and cheaper than buying a headphone amp) solution is to buy a SPL meter and learn to listen at sane volumes.

Beyond that, I've concluded that well measuring and well designed headphone amplifiers sound the same in volume matched tests.  Designing a good headphone amplifier is not anywhere close to rocket science, so it should be quite easy to find a inexpensive headphone amplifier than will work with most headphones.

That's about it.

HD650 Headphones request

Reply #19 –
Quote
IMHO the easier (and cheaper than buying a headphone amp) solution is to buy a SPL meter and learn to listen at sane volumes.

This I'm quite interested in. I've been particularly careful with my hearing and music habits. I found a lot of articles on the internet that give stats specifically for an iPod and its stock earphones, but I haven't dug up the more widely applicable knowledge about it (so far my big change of habit has been keeping my music low enough that I can still hear the bus, thereby assuming that whatever damage the noise of the bus is doing to my ears isn't worse than my music).

First search on google says Radioshack sells them for about 60USD .. is that a fair price? Or is there a better place to get them? Any quick comments about how to use one (or a link to a guide about their results) would be greatly appreciated.. I assume it's as simple as putting the device as close to the headphones as my ear would be?

PS: Thanks again for posting your findings.

HD650 Headphones request

Reply #20 –
Quote from: odigg on
I've found that the one should look at the output impedance of a headphone amp when buying a headphone amp.  A headphone amp with a near 0 output impedance can drive most anything with a flat frequency response. 

...The solution is simple - get an amplifier with a near 0 output impedance.  This can be a little complex as I suspect some headphone amp manufacturers are not accurately reporting output impedance.
Right.  There are two ways of reporting impedance, and you don't always know what they are reporting.  The "source impedance" is the effective impedance "looking back into" the amp, and this is what's important for flat frequency response.  If you see something low like 2 ohms (for a headphone amp), that's the source impedance.

The other thing they might give you is the minimum recommended load impedance.  If you see a spec like 32 ohms, it might be the load impedance or the source impedance, and it's hard to tell.  (It might be rated for driving 32-ohm headphones, but it might have an internal impedance of 1 ohm...)

I would expect a dedicated headphone amp to have a low source impedance.  A headphone output on a receiver might simply be a resistor in series (or a series-parallel network) with the speaker outputs.  In that case, it will have a higher source impedance.  But, a headhpone amp might also have a series output-resistor as protection to prevent excessive current (and damage) in case of a shorted output.


Quote from: Chef on
First search on google says Radioshack sells them for about 60USD .. is that a fair price? Or is there a better place to get them?
That's reasonable for an SPL meter.  Parts Express[/u] has SPL meters from $30 USD to $350.

I don't know how you use these with headphones!  I think headphone & earphone manufacturers have a "simulated head" and/or "simulated ear" adapter...  Maybe you can find instructions on how to make one????

HD650 Headphones request

Reply #21 –
I have a an older analog display radio shack SPL meter.  It broke recently but when it was working it did what it was designed to do.  My advice to anybody buying one now is to get a digital display

It's quite easy to measure the SPL of your preferred volume on a full sized headphones.  You should (need?) have a setup to that basically allows a good seal between the SPL meter and headphone earcup just like the earcup seals to your head.  The easiest way to do this is to get a piece of cardboard, trim it to size so it can seal against the earcup of the headphone, then cut a hole in the middle of the carboard so the microphone of the SPL meter fits snugly in this hole.  Basically you have to make a carboard donut.

I have no idea how would one do this with IEMs.

Keep in mind this method is not perfect and that these inexpensive meters probably have some error.  You'll also have some variance based on the location of the meter, the seal, the distance from the driver, etc...  Just to be on the safe side, I'd interpret 80db measured as 83db actual.  Don't ask me why I say 3db, it's just a number I pulled out of the air.

Quote
Right. There are two ways of reporting impedance, and you don't always know what they are reporting. The "source impedance" is the effective impedance "looking back into" the amp, and this is what's important for flat frequency response. If you see something low like 2 ohms (for a headphone amp), that's the source impedance.


It wouldn't surprise me if some manufacturers were reporting source impedance insufficiently.  But you are correct in that most dedicated headphones amps typically have a very low output impedance.