[Anouk]

Hi, I read on the headroom site that the akg k702 is not very sensitive. But somewhere else I found that it has a sensitivity of 105db. Is that correct because that seems rather sensitive to me.
I had an ultrasone headphone which had a sensitivity of 95db.
Greetings, Anouk,

 

[crossmd]

It's not, really. It need a solid, stable desktop amp to push it hard enough to make it really worth spending your precious $250. Trust me on this one. Do a search and you'll see.

 

[Anouk]

Hello, i know from experience that this headphone needs a good amp, I just dont udnerstand it however, i have the jvc dx1000 here and that is also about 60 ohm and 105 db and not too hard to drive at all (my ibasso does a very admirable job when compared to my woo).
Greetings, Anouk,

 

[crossmd]

I mean, you can send some juice into them using whatever you want, theoretically. The issue lies in the fact that they're sort of finicky regarding the flavor of the amp that's giving it to them. It's about sound quality. Not necessarily the numbers. Trying to amp these via a portable amp, is going to leave you with a bad taste in your mouth..leaving you to post about how the fault lies with the phones because of the numbers on the side.

Like cigarettes or alcohol, there needs to be a Surgeon General's warning on the side of these that says: AMP ME. Its deceiving, I know..but a portable won't begin to get you where you need to be with these phones.

 

[Zombie_X]

In my experience you can get them to loud levels out of an Ipod/Zune/D2+, but tends to sound thin and weak. Also even though they are lower impedance their sensitivity is what makes then difficult to drive since they need a lot more juice. So even a decent old tube amp should do a far better job than a portable.

I know with my new X-CanV8P it can drive them very well and up to 100db and beyond. It also gives them a much fuller sound and a bit more bass while tightening up the entire sound. A really worth while purchase on my part. There is also much more transparency and separation of instruments.

My VHP-2 can also drive them nicely, but gives them a more analytical sound signature which is different than the warm, full sound of the X-CanV8P.

 

[audiowize]

A word about sensitivity...

The standard for loudspeakers is SPL produced at 1 meter off one watt and generally at 1000 hz.

For headphones, it makes no sense to measure the sensitivity at one meter, and this is obviously not the case since the numbers are so high. Unfortunately, I don't see anything in the manual about how they have done this measurement.


I personally have the 701's in my lineup. They basically need an amp capable of driving very efficient speakers (given a suitable transformer).

 

[Anouk]

Dont get me wrong I KNOW they need a good amp but I wonder why, the sensitivity isnt that low if i read the specs right 105 db and about 60 ohm seem as jvc, still the akg is a lot more hard to amp..... Why.....
Greetings, Anouk,

 

[audiowize]

I'm saying that if you don't specify a distance, the sensitivity really doesn't mean anything.

 

[holland]

you'll get different numbers with dB/mW vs db/V. db/V will give higher numbers but you really want to use dB/mW. Converting the 105dB/V for AKG K702 yields about 93db/mW.

 

[holland]

BTW, formula for converting is

db/mW = db/V + 10 * log(R * 0.001)

92.92 = 105 + 10 * log(62 * 0.001)

 

[estreeter]

Yep, AKG/Senn/Beyer all measure sensitivity using different metrics. Surprising amount of sanity in this thread thus far, given the subject line. Anything with the acronym 'AKG' followed by '70' seems to attract The Zombie Horde.

 

[Zombie_X]

Quote:

Originally Posted by Anouk /img/forum/go_quote.gif Dont get me wrong I KNOW they need a good amp but I wonder why, the sensitivity isnt that low if i read the specs right 105 db and about 60 ohm seem as jvc, still the akg is a lot more hard to amp..... Why..... Greetings, Anouk,

It's just the way they are. They are incredibly power hungry phones in my experience and such need for more power to get louder. The Ohm/Sensitivity specs give you an idea on how they will preform, but you have to take into account how they function. I personally never trust Ohm/Sensitivity since that sometimes means squat when it comes to powering the phones.

They are so power hungry they drain my LDMK1+ in mere hours (even though it has a rated battery life of 30hrs). They are also current hungry and pull more than what the device is supposed to give.

 

[holland]

Quote:

Originally Posted by Zombie_X /img/forum/go_quote.gif They are also current hungry and pull more than what the device is supposed to give.

LOL. I understand your intentions, but I think the impression you are leaving is incorrect. You can probably hit about 113dB on the LDMK1+ with the K701 before clipping. The limit is not the current, as the buffer can supply 250mA, which the K701 cannot consume. It is likely the voltage limit induced by the low voltage swing of the battery pack.

Your battery life may be more that your amp is oscillating. You can't really tell unless you open it up and know what you're doing in order to look for it.

From pure specs:

200mW @ 32 ohm rating yields about 2.5Vrms and about 80mArms. The 2.5Vrms is clearly the limit before clipping, and not the current as you seem to imply as 80mA is well within the grasp of the output buffer.

Recalculating for the K701 you get about 41mArms when utilizing the 2.5Vrms limit for a total power output of about 103mW. Figuring the 2.5Vrms is the limit, you get about 8dB more over the 105dB/V rating, so that leaves you at about 113dB for the LDMK1+.

In contrast, the JVC DX1000 can hit over 122dB on the same amp.

For a portable amp, 113dB is more than respectable. An 18V Pimeta (a DIY build with 2 9V batteries) would give the K701 the power it needs without much issue. Whether or not it sounds good is a different matter.

Many people make claims about current hungry this and that are not factual. Headphones don't really use much current, except for a few like the K1000.

Also a pure tube amp will have a harder time with a K701, if OTL. If transformer coupled you'll be fine. The reason is because tubes can't give off that amount of current without using a bank of cathode followers (i.e., a whole bunch of output tubes).

One can work the math, and depending on how loud you listen to, *what* you listen to, you can make do with a variety of amps. SS is easiest to drive the K701, that or a tube hybrid. If you're looking for pure tube, it's harder.

Anouk, your JVC DX1000 is rated at 102dB/mW. Compare that to the K701 at 93dB/mW and it's pretty clear.

 

[Zombie_X]

Sorry that I stated it wrongly. Yeah I meant to say they would clip. I have personally heard bass clipping and such.

 

[Acix]

Yes, the K-702 are very sensitive. They will clip easy and it's a great to have this control over your mix/mastering in the studio. You will get an nice alert in form of edgy sibilant before the main distortion will show up. This correspond well and match my other studio equipment.

The K702 is one of the few with this unique sensitives for studio abilities.

I prefer SS amp, and I do agree with Holland about the amps.