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struts
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AKG Debuts K 702 Headphones For Recording and Broadcast Applications

Just when you thought it was safe to go back into the water AKG announces the K 702 for August release. As I understand it this is intended to be a pro model and will be sold in parallel with the AKG K 701 rather than replacing it.

As you can see the new model comes in a handsome dark blue and features a removable cable which should delight purveyors of aftermarket cables. It is not entirely clear to me from all the marketing blurb what other enhancements there are over the K 701, no doubt all will become clear in the fullness of time.

Clicky here for the hoopy scoopy!

dcstep
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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl

Will you be getting one of the first shipments so that you can report to "us"?

Dave

struts
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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl

You're kidding, right? I am still burning in my new K 701s with their Black Dragon cables! I am guessing they have somewhere over 100 hours on them by now, maybe 120-or-so, but although they sound very good indeed I still don't feel they have fully settled down yet...

I find I am reaching for the K 701s much more than the HD650s since I got the pair with the Moon Audio cables, which has never been the case before (regardless of which cables I use with the HD650s, I think I am up to four now). Maybe I'll find time to write up some thoughts over the summer.

dcstep
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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl

It's great to hear that you're enjoying the 701s. Did you think that the Black Dragon cable upgrade was big. I'm sure enjoying my Cardas on my 701s.

Dave

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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl

Interesting stuff!

Cool to learn also that you are sooo pleased with your new cables.

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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl

Struts,

Thanks for the info. I haven't been keeping up with things over at Head-Fi.org but I just checked and there is already a 12 page, 114 post long thread about these 'phones. And of course the thread includes plenty of speculation on the ability to recable these headphones - balanced, single entry, double entry and all things in between.

The high resolution image (click the link on the page that you linked to) is pretty cool and these 'phone sure do look sharp.

I guess Wes Philips will be getting one of the first pairs to hit the US shores. I can just see conclusion of the review: "These headphones are so good that I just had to buy the review pair" - Yeah won't we all "just have to buy the review pair" at 50%(?) off list price. As I always say: would the reviewer buy the item under review at full list price, like the rest of us poor audiophiles have to do? Now that would be a much more meaningful endorsement than buying the highly discounted review item.

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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl

Looks like cabling will be a snap, given the pro-level connector shown in the literature.

The guys at www.head-fi.org are really big on balanced connections. I guess it makes some sense because so many of them are using crummy DACs that spew tons of RFI/EMI into the area right around the cans, but I don't find it to be an issue in my rig. My Woo Audio WA6 only has single ended connection, but my CDP to pre-amp is balanced and well shielded via a heavy chassis, so I'm doubting that I would gain much from going balanced on the headphone rig.

Dave

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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl


Quote:
. . . headphones - balanced, single entry, double entry and all things in between.


Headphone porn.

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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl


Quote:

Quote:
. . . headphones - balanced, single entry, double entry and all things in between.


Headphone porn.

Exactly. I feel myself getting excited right now...

Dave

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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl


Quote:
The guys at www.head-fi.org are really big on balanced connections. I guess it makes some sense because so many of them are using crummy DACs that spew tons of RFI/EMI into the area right around the cans, but I don't find it to be an issue in my rig. My Woo Audio WA6 only has single ended connection, but my CDP to pre-amp is balanced and well shielded via a heavy chassis, so I'm doubting that I would gain much from going balanced on the headphone rig.


Dave,

You may be confusing balanced headphone drive with balanced interconnections. While related these are really two different things and the benefits of the former extend well beyond those of the latter. See here for a better description than I could manage.

I have heard the difference on both Sennies and AKGs and it is quite significant. In particular, I was immediately struck by the deeper bass the K 701s produce when driven in balanced mode.

So I am definitely planning to go balanced with my headphone rig. The only problem is that means I will need a new DAC as well as a new headphone amp (I am currently using a Grace m902 which contains both but is single ended-only). I am leaning towards the very tasty looking (and sounding) Rudistor amp, the DAC is a bit more of a problem. Hmmmm...

dcstep
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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl

I still don't get it. The loads are so small that one amplifier circuit should easily handle the load. It seems to me that the quality and power of the amp circuit is more important than this "fully balanced" operation with the same or lesser power.

Are you sure that the amps were of the same power and quality? What you describe is similar to what I hear between say a Woo 6 and a Dark Voice 336.

Dave

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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl


Quote:
It seems to me that the quality and power of the amp circuit is more important than this "fully balanced" operation with the same or lesser power.


Absolutely true.

Additionally, a true well-designed balanced circuit is a bit pricey to implement. Thus, single ended often sounds better.

That said, perhaps headphones benefit from balanced operation differently than speakers for example. I don't have any reason to believe this, but quite a few listeners that I respect report that balanced driven cans are better. I haven't heard a pair so I don't know.

struts
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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl


Quote:
Are you sure that the amps were of the same power and quality?

Yes, I have heard the same amp (same actual unit) driving the same cans (HD650s, same actual pair) through two lengths of the same type of cable, one balanced and one S-E. At the same listening session I compared balanced and S-E AKG K 701s, although the balanced and S-E cables were of different types so this was not an apples-to-apples comparison.

The improvements in balanced mode were not subtle, as best I could tell entirely for the better, and quite similar in nature for both pairs of cans. The bass seemed deeper and weightier, and both transparency (detail) and dynamics seemed improved. For some reason the improvements to the K 701s seemed greater in magnitude than those to the HD650s, at least it made a much stronger impression. Whether this was because the difference was actually bigger (the S-E cable was the standard stock cable so maybe the baseline was lower?) or whether it just seemed so because the sound was more to my taste I will never know.

In fact the sound with the AKG K 701s driven balanced with Moon Audio Black Dragon by a Rudistor RPX-100 was the best I have ever heard through cans by some margin. I got that feeling you get when you instantly know what your next upgrade is going to be. I'm afraid you will have to take my word for this for now but I would strongly urge you to get along to a canjam and listen for yourselves.


Quote:
That said, perhaps headphones benefit from balanced operation differently than speakers for example.

There is at least one big difference. Stereo speakers do not generally share a common return path whereas S-E cans generally do. This inexorably leads to crosstalk and distortion. Of course whether this explains the perceived improvements in SQ is an entirely different question, however there is a difference.

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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl

A "common path" is separate wires, so it seems like the quality of the dielectric is critical as is the geometry. Hence, wiring like Cardas can be superior to stock wire.

I'm not arguing, just trying to understand the advantage over a good amp and good cable. The trouble with sampling at meets is that it's hardly ever apples to apples. I appreciate the possibility, but it seems unlikely to be more effective than a really good amp and really good cabling. After all, you don't have the problem of driver interaction like with between the woofers and tweeters in a speaker system because, generally, with cans one driver tends to cover the whole range.

Dave

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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl

Dave,

I believe the "common return" is one wire in most stock cables, although I haven't dissected them to check! However I assume some (maybe most) aftermarket cables have separate return wires joined at the plug, since most of them are offered as balanced or SE with only the termination differing. This approach is valid since unlike the case of balanced interconnects it is not critical that the wire offers a specific characteristic impedance within a close tolerance band.

I will leave the religion to the preachers, but adherents of balanced drive maintain that it offers sonic benefits disproportionate (in a positive way!) to the increase in cost. This is of course virtually impossible to prove empirically one way or another. I would very much like to compare the Rudistor RPX-100 that so impressed me with a good SE headphone amp of comparable price, for instance one of Ray Samuels' models or a Single Power, but all the likely contendahs lack representation over here so they are extremely rare.

Comparing half the Rudistor (which is effectively what you are doing when you run it SE) with the full monty balanced output has certainly convinced me, however I will probably never convince you and I'm not trying. I subscribe to some audio religions and not to others, however I usually find that 'epiphanies' are caused by memorable listening experiences rather than bulletin board discussions I can only recommend you listen for yourself if you get the chance.

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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl

Struts, thanks for trying to explain this "religion" to me. I've just been trying to figure out how to do a reasonable A-B comparison with apples-to-apples. I'm not against it, just trying to understand the excitement. (Those guys at head-fi.org DO get excited easily).

Dave

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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl

I have pondered it on-and-off and I have not come up with a test that would really be apples-to-apples. The test that eliminates most variables is to compare the balanced and SE modes of an amp offering both, as I did, however in this case you are only using half the amp in SE mode.

I agree, head-fi.org has more than its fair share of 'Audio Taliban', although I still enjoy poking around there. It is unbeatable for tips on new headphone product releases and tweaks and you just can't beat the passion. There are more new threads in a day there than the headphone board here gets in a year!

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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl


Quote:
Dave,

I believe the "common return" is one wire in most stock cables, although I haven't dissected them to check! However I assume some (maybe most) aftermarket cables have separate return wires joined at the plug, since most of them are offered as balanced or SE with only the termination differing. This approach is valid since unlike the case of balanced interconnects it is not critical that the wire offers a specific characteristic impedance within a close tolerance band.
...

I finally remembered to check my recabled 701s and there are clearly two wires per side.

Things are sounding so good, there's no way I going to have the Woo modified for "balanced mode", whatever that is. Things are totally quiet, refined, transparent, deep and lush.

Dave

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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl


Quote:
I finally remembered to check my recabled 701s and there are clearly two wires per side.


Making them bi-wired headphones.

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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl


Quote:

Quote:
I finally remembered to check my recabled 701s and there are clearly two wires per side.


Making them bi-wired headphones.

Or "balanced", whatever that means with headphones. I always assumed there'd be a + and a - for each side, just like speakers.

People over at head-fi.org get really bent out of shape about this, and I have no idea what they're talking about, even after that thoughtful link in this thread.

Dave

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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl


Quote:
I have no idea what they're talking about, even after that thoughtful link in this thread.

Dave,

It's really simple but I'm struggling to come up with a good analogy. Try this. Imagine a rope going over a pulley. One person can pull on the rope on one side of the pulley ('live') and the rope the other side just follows along ('return'). In the equivalent of balanced mode two people pull on the rope in unison (i.e. in different directions relative to the pulley) on either side of the pulley. The 'return' leg is now being actively driven by a signal 180 deg out of phase with the first one.

How did I do?

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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl


Quote:

How did I do?

Ugh, my head hurts.

I'll try again tonight, harder.

Dave

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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl

I find Headroom's description quite clear: Balanced Headphones

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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl

I was worrying with the "fully balanced" mode explained in the link at the bottom of your citing.

Still, if the amp is well designed with a properly designed ground, I don't see where balanced will do any good, if all it does is have two routes to ground rather than one then that seems inconsequential. It's not like the difference between a balanced IC vs. single-ended, it's merely changing the point where the two grounds become common.

Since this is usually done in connection with recabling and recabling makes a big improvement, I doubt that most users ever hear the difference due to the grounding scheme only. You'd have to make up two pairs of headphones exactly alike but for the ground and alter an same amp to accept both.

As for "fully" balanced, that just really complicates things and seems a lot like "fully" balancing a cartridge, which already has a great ground with the groundig wire to chassis. Maybe it does work, but the amp is so altered to facilitate it that you get into apples vs. oranges, it seems.

Dave

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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl


Quote:
I was worrying with the "fully balanced" mode explained in the link at the bottom of your citing.


I understand - but go on to the next page.

The "balanced" they describe is different than what I think of as balanced. Instead, they are creating a push/pull effect on each headphone driver.

I wish they didn't use the term balanced to describe this.

struts
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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl


Quote:
Still, if the amp is well designed with a properly designed ground, I don't see where balanced will do any good, if all it does is have two routes to ground rather than one then that seems inconsequential. It's not like the difference between a balanced IC vs. single-ended, it's merely changing the point where the two grounds become common.

This is indeed getting quite confusing but I'm not quite sure why!

In a fully balanced configuration neither live nor return is tied to ground, indeed the very definition of 'balanced' is that both signals have the same impedance with respect to ground. In practice the ground 'floats' half way between the live and return signals. This is true whether you are talking about a balanced cable (neither pin 2 or 3 is shorted to pin 1 which is chassis ground) or balanced drive in which both the live and return signals are amplified completely independently. So what is being described as 'fully balanced' is indeed fully balanced, both live and return are being independently and actively driven by output stages referencing the same ground.


Quote:
As for "fully" balanced, that just really complicates things and seems a lot like "fully" balancing a cartridge, which already has a great ground with the groundig wire to chassis

Same thing here. When a cartridge is used as a balanced source none of the four pins is tied to ground. The ground is used purely to provide shielding, not as a voltage sink.


Quote:
The "balanced" they describe is different than what I think of as balanced. Instead, they are creating a push/pull effect on each headphone driver.

What do you think of as balanced? They are indeed creating a "push/pull" effect. That is exactly what balanced drive is.


Quote:
I wish they didn't use the term balanced to describe this.

Why not? In what way do you find it inappropriate?

dcstep
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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl

Struts, in the "balanced" headphone (not "fully balanced") are they not merely changing the point where the ground is common (moving it from the Y to the plug)? Looking at the diagrams linked to by Elk, that's the only difference I see. I see little point in that.

I do see the potential of "fully balanced". At the Rocky Mountain meet in a few weeks, hopefully I can compare a fully balanced AKG rig to mine. Unfortunately, the comparison will probably be using a not so great amp with an really crappy internal DAC, but you never know.

Dave

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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl


Quote:
Struts, in the "balanced" headphone (not "fully balanced") are they not merely changing the point where the ground is common (moving it from the Y to the plug)? Looking at the diagrams linked to by Elk, that's the only difference I see. I see little point in that.

Dave,

As far as I can tell that diagram just shows a headphone with balanced cabling being driven by an unbalanced amplifier. Generally, unbalanced amplifiers don't sport XLR outputs so the real-world relevance of that diagram is a bit of a mystery to me!

What you are describing, if I understand you correctly, is a scenario where a balanced stereo cable (four conductors plus shield) is terminated with a stereo TRS plug (two conductors plus shield). In that case you would be correct, there would be no real difference between that and a two-conductors-plus-shield cable with a Y-joint in the headphone.

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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl

Here is the ultimate diagram showing fully balanced operation starting with a balanced DAC.

I think the confusion exists because they use + and - as the inputs to each headphone driver. This infers that the ground - is the same as the inverted signal - . The way they diagram the input into the amp is confusing as well.

It would be more clear if they indicated that each driver receives the inverted and non-inverted version of the same signal.

struts
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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl

Elk,

I agree, the circuit diagrams in the Headroom article are slightly 'stylized' and therefore tend to become more confusing the closer one studies them!

However, to return to the original point, some headphones sound better when driven in this way. Although I think I understand the theory I don't pretend to be able to definitively link cause with effect, however I have heard the difference and I am definitely a 'believer'! Everyone else is of course entitled to their skepticism.

Elk
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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl

I remain intrigued by the concept.

I haven't heard headphones driven balanced but would enjoy the opportunity to do an A/B.

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Re: AKG Debuts K 702 Headphones For Recording and Broadcast Appl

K702 is already available for sale at eBay for US$365.

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