Piano World Home Page Forums Our Most Popular Forums Digital Pianos - Electronic Pianos - Synths & Keyboards Sennheiser HD 650/600

Brent, are you sure it's actual audio quality and not just a louder signal bringing out more details? The Ipod output has a really low volume as far as I remember.

It is not a myth.
Yes, sensitivity is important, too.
But the impedances of the driving amp and of the phones do matter.

Well not in the sense of running out of "turn up the volume" range but I suppose in the sense that an iPod might not get to my preferred listening level without the distortion making it sound louder than it really is. There's always that problem with an overtaxed output stage where you can go strictly "louder" with a stronger bit of gear because distorted, zero-headroom audio starts hurting your ears at relatively low volumes. At any rate, it's hard to level match between different bits of consumer electronics gear.

The end effect is it sounds worlds more detailed and cleaner with the headamp so it's necessary in that setup. But on the computer side my E-MU's headphone jack is quite acceptable.

Here's an article about the impedance issue: Sound & Vision: Output Impedance: A Show and Tell

I like this article because they actually measure the frequency response of the headphones with a microphone - they didn't just measure the electrical signal across the headphones.

Greg.

Interesting. If those actual frequency responses are what you would hear at your ear (doubtful) I'd prefer those associated with the higher impedance laptop output (blue) as opposed to those driven by the V-Can (red), particularly figure 4. But his conclusions are the opposite, with this at the end "Or to put it more simply: Headphone amps aren’t useless creations intended merely to capitalize on commercial trends. They’re the real deal." This, after saying he can't say which you might prefer, and several examples of the V-Can making things arguably worse. The author strikes me as something of an industry toady.

@Dewster,
They used a proper setup for measuring the frequency response - including a simulator of a human ear. They used a fully fledged headphone tester. He may indeed be an industry toady, but the raw measurements appear to be of a high standard.

Greg.

@Dewster,
That figure 4 you referred to is for the Audéo PFE 232 in-ear monitor.

I contacted the manufacturer, and they said that the ideal impedance is zero ohms, with a recommended upper impedance of 15 ohms. (this is hardly surprising, because they are designed for portable devices, which have a low output impedance) This means the V-can, with the 5.1 ohm output impedance, is far more likely to produce a frequency response that is closer to the designer's goal, than is the case for the 75 ohm laptop. Also, it's very difficult to just look at those raw frequency response curves and make an assessment - apparently a correction has to be applied - refer to Stereophile: Between the Ears: the art and science of measuring headphones (this article also mentions the impedance interaction problem). Neither article mentions doing the obvious - simply contacting the manufacturer and asking them for the recommended output impedance. Phonak didn't take long to come back with an answer, and neither did AKG when I contacted them. (they also said as close to zero ohms as possible) I have also contacted Sennheiser re: the HD598 - I'm having trouble getting through to the right department, but they are responsive. (they're giving me general advice which I'm not comfortable with yet - I want a more definitive answer)

In that first article, regarding doing the "safe" thing and looking for headphones with a flat impedance curve - that might be safe, but it's not an approach I would take. I have read that headphones with a flat impedance curve may have a compromised design in order to produce this flatness, and those that are not flat are not as compromised. (no link at the moment - sorry)

Greg.

You may need an amp for HD6xx or above of Sennheiser series, but HD 595 / 598 is fine without headphone amp.

Nice article, thanks! I remember stereo equipment reviews in the ancient Popular Electronics, where the tester (Julian Hirsch?) discussed the difficulties and gray areas when testing headphones, which is why I stated that it was doubtful those frequency response graphs are what one would hear at their ear (corrected or not).

Interesting that the author of the article you linked to preferred the sound of the Audio-Technica ATH-AD700 over the other three. I really like the sound of our ATH-AD700s, quite open and neutral sounding, though the physical design does not include an in/out gimbal, so they probably won't fit some heads as comfortably as others. I believe they've put a stop to my need/desire to find anything better in the way of headphones (wish I could say the same re. DPs).


It is sometimes a goal when designing & building speakers to make the impedance flatter, certainly the curve is often presented as an indication of how "easy" they are to drive, etc. This tends to add components though, and beefy coils and caps are not inexpensive items.

Toady was perhaps too strong a word. I still think his concluding quote is rather over-the-top and something of a non sequitur when considered with the information presented previously.

Sometimes one needs more drive voltage to keep the output stage from clipping with high impedance / low sensitivity phones, or more rarely one may desire a lower damping factor into the driven impedance so as to alter the frequency response in some way.

But the other 95% of the time headphone amps are pretty much just "useless creations intended merely to capitalize on commercial trends". The magical marketing claims are the tell.