Piano World Home Page Forums Our Most Popular Forums Digital Pianos - Electronic Pianos - Synths & Keyboards Headphone jack out impedance. Kawai especially

Hi all,

I'm not only looking for my first DP, I'm looking for a pair of headphones to go with it.

I don't find any specs for out impedance of the built in headphone amps? (to match with the 1/8 rule of thumb for the headphone impedance)

Especially interested in Kawai models (CN34 and CA65) but others are of interest too. Am I looking poorly or is this a hard spec to find?

Best Regards and thanks,
Fredrik

Unfortunately it's a nearly impossible spec to find, even for a lot of hardware that you would expect to have specs on exactly that type of thing. I will be very impressed if you can ever find it for any digital piano headphone jack.

You can always ask the manufacturer though - I've done that once, and got a quick answer. (mind you this was for the AvantGrand, so I probably got a quicker response than normal ;^)

Greg.

There has been lots of discussion on here about headphones, and occasionally impedance matching. In general low to medium impedance seems best suited to most DP's, but higher needs a (external) headphone amp. I had a CN33 and used AKG 240 MK2 and Shure SRH440 with plenty of audio headroom.

gvfarns,
That's what I suspected, and your name has been in quite a few of the threads.

sullivang,
I may try that. Just out of curiosity, what was it for your AvantGrand?

I'm looking at the AKG K-550 as a hot candidate. They are 32 Ohms. 32 / 8 = 4 which I think is quite low? But I may be mistaken I don't have a good reference frame here.

The HD598 that often see recommended is 50 Ohm, AKG-K240 II that I see people here using are 55 Ohm.

The answer was "approximately 33 ohms for all three models". (I don't have an A.G though - I was only asking out of curiousity)

Just btw, it appears that the AKG K-550 has a very flat impedance vs frequency curve, so the 8:1 rule may only really apply to the damping factor, if you're concerned about that. The frequency response would at least be flat, with any normal output impedance.
I've tried my K-601 headphones with two amps - one with a 5 ohm impedance, and one with a whopping 220 ohms, and could not detect the slightest difference. The K-601 also has a very flat impedance vs frequency response, so if the damping factor was causing some kind of distortion, I couldn't hear that.

The other issue is volume level - tricky to be absolutely sure about that without trying, unless you can get an output level spec and then do the maths to work out the SPL.....

Greg.

Here's the impedance graph: http://graphs.headphone.com/graphCompare.php?graphType=0&graphID=3578

FredrikJ: If you don't understand anything I've said, then the main point I'm making is that in my (very limited) experience, if the headphones have a flat impedance vs frequency response, then the 8:1 rule doesn't seem to matter to me, and the main issue for me would then be whether the headphones would be loud enough with any particular headphone amp.

FWIW, I have also tried some headphones that do NOT have a flat impedance vs frequency curve, and I think I can hear a small difference in the bass response when I compare the 5 ohm amp to the headphone output of my laptop (circa 50 ohms) It's still not enough to bother me though. I haven't tried these headphones with my 220 ohm amp yet.

Greg.

Lots of good replies chaps.

FredrikJ, I confess that I'm not terribly knowledgeable when it comes to headphones, however, please feel free to contact Kawai Europe for further recommendations.

Kind regards,
James
x

FWIW --

The only place I've heard that "headphone impedance" makes _any_ difference is in discussions of battery-powered MP3 players. Those use small, low-voltage batteries, and have limited voltage swings at the headphone output.

And in that case, people resort to outboard 'headphone amps'.

But DP's have 12-volt power supplies. And better electronics than "portable MP3 players".

I'll bet that any "wall-powered" digital piano has a headphone amp that will drive _any_ reasonable headphone to "more than loud enough" levels. And the headphone amp will have reasonably flat frequency response, because that's easy to engineer into low-power circuitry.

In other words:

. . . Stop trying to "match impedances" --

. . . just get a good pair of headphones, and plug them in.

. Charles

Here's a link that can help clear up a few things about headphone impedance ...


AKG faq

Charles: You're oversimplifying things. (and btw, my Casio PX-330 can NOT drive my AKG K601 full-sized headphones loud enough, although these headphones are admittedly particularly hard to drive. My old Kawai MP9000 can drive them loud enough though)

In addition to Dave's link, here are some more:

http://nwavguy.blogspot.com.au/2011/02/headphone-amp-impedance.html

http://www.soundandvisionmag.com/blog/2011/11/14/output-impedance-show-and-tell
http://www.stereophile.com/features/808head/index.html
http://www.benchmarkmedia.com/discu...c-advantages-low-impedance-headphone-amp

Greg.

Kawai Europe answered that "the impedance of the headphone should be between 50 and 100 Ohm."

That didn't exactly answered the question on the out impedance (CN34 and CA65 was mentioned when I asked), but gives a hint. (I was looking at AKG K505, that are 32 Ohm). I'll get back in this thread if I get more information from Kawai.

I don't know this at all, but after doing some reading - this is not only about driving the headphones, but also how they sound (the frequency response), if I understand things correctly. Most of it would probably go undetected by me, but it's still fun to dive into specs

Ugg -- I guess I was! Sorry, and thanks --

. Charles

This might not help at all as my knowledge of headphones is very limited but the CN34 has two settings for headphone volume. Normal (which is low volume for low impedance headphones) and high (for high impedance) to compensate for high ohm headphones. This is just headphone volume to speaker volume ratio i guess.

And, as always. No forum member and no technical spec can replace your ears ;-)

Thanks for posting this information, it's very helpful!!

EDIT: I don't know if a 32 or 52 ohms headphone would make any difference with regards to the tone, I mean, does it affects just the volume or the sound character, as well?

I know that people use 80 Ohm and 250 Ohm head phones on digitals (DT 770 PRO 80 Ohm and 250 Ohm). 30 Ohms is more a portable mp3 player thing IMHO.

From some forum:

"applying it to headphones, if the output impedance of the amp matches the headphones, the signal flow will be ideal. If they differ, if the headphones have less impedance the signal will flow too easily; that decoupling would cause the kind of "lack of consistency in the sound" as if it was more fragile, if the reverse, signal would flow heavily, losing power and timbre."

So I asume it's not just one given impedance, but the balance between headphones and amp. what gives the better sound.
Am I wrong?
And by the way, is it important enough so as to point it in some manual? Or are customers supposed to know it all...

(Translation from spanish is mine, please forgive any mistake; happy this is not a polish forum ).

The more correct statement would be: if the output impedance of the amp matches the headphones, you can achieve maximum power transfer from the amp to the headphones.

Two things:
1. Is that necessary or important?
2. What about damping factor? This figure improves with high-Z phones.

Considering those two points, it's clear that low-Z phones get more power from the amp, but high-Z phones get better damping factor.

In an ideal world you'd be able to choose the impedance of BOTH the phones and the amplifier.

You can choose phones impedance readily.

But you cannot choose your piano's impedance. If it's impedance is too low for your phones, all you can do is buy a headphone amplifier.

Ok.
At least we already know that, for this models (Cn34, Ca65 and, perhaps, ES7 which has the same sound than Cn34) Kawai technicians point for some 50-100 ohms impedance headphones.
Funny (at all! grgrgr) that I was using those with 32 ohms and finding the sound close to saturation from 1/3 of the power on.

According to this (from wikipedia):

Overdamped (ζ > 1): The system returns (exponentially decays) to equilibrium without oscillating. Larger values of the damping ratio ζ return to equilibrium more slowly.
Critically damped (ζ = 1): The system returns to equilibrium as quickly as possible without oscillating. This is often desired for the damping of systems such as doors.
Underdamped (0 < ζ < 1): The system oscillates (at reduced frequency compared to the undamped case) with the amplitude gradually decreasing to zero.
Undamped (ζ = 0): The system oscillates at its natural resonant frequency (ωo).

My questions would be: less ohms than ideal means overdamping, therefore distortion? Did I understand anything?
I mean, is clear that you need more amp power to run higher impedance, as the higher it is, the more power it substracts (plus the cord's impedance). But aside the power, what is the difference in terms of quality?