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On HD650s and speaker amps...


catscratch
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Well, I've had my first exposure to HD650s using push-pull amplification. I have to say, I'm stunned.

I *hate* these headphones single ended, for reasons which I will list here. Their bass is loose and overwhelming; there is a very slight grain to their sound, which is more of a characteristic of most dynamic headphones in general to my ears (but not all); the highs are muffled and obscure the detail; the impulse response is slower than a Geo Metro; the tone is far too warm and there seems to be bass even where there shouldn't be. And I have no idea why Sennheiser decided to voice the HD650 this way - rather I can guess (more bass when underdriven), but I have no idea how they could have been this thick.

But...

Push-pull seems to be a miracle cure for nearly all of the HD650's woes. The bass is no longer loose, the highs are no longer muffled, there is no grain to the sound that I can detect, and there is much, much more detail and instrument separation. But most importantly, the speed has gone up by orders of magnitude. It sounds seriously stunning this way - not much like a dynamic at all, not much like anything except for the music. It's still very very colored, but it's a very appealing HE90-like coloration that I can live with, and the texture, detail, imaging, transparency and overall realism are out of this world compared to what they are single-ended. Is this a dynamic??!?

Even stranger still is that I got all of this running the HD650 off... my push-pull Dared VP-20 speaker amp. The Senns were using a 4-pin XLR cable, into AKG's 4-pin female XLR to speaker leads adapter.

What the hell? Am I going to blow up my amp forcing it to drive a 300 ohm load? Am I going to melt the voice coils forcing them to swallow more current than they can handle? The amp outputs 18wpc into 4 ohms, so I'm guessing it really can't output much into 300 ohms, but can it handle the load without going 4th of july on me?

Even more disappointing is having this system, and then having it gone since I had to give up the cable. Oh well, you can guess what I'm now trying very very hard to get.

Consider me converted. I still hate these headphones single-ended and probably always will, unless I can hear something single-ended that can cure their ills, but in this system they're stunning. This is the best system I've had; better than the K340, SR-404, and H2 combined, though I'd wager this is probably new toy syndrome still, um, toying [...] with me. I'd love to hear them with a more neutral source and silver cables, which is where I'm headed next.

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Peculiar...

I've heard them on some very nice balanced amps (would it be comparable to push-pull from a speaker amp? There's no way the drivers are getting more than 400 mw?) and they improve. Not an earth shattering improvement so if you didn't like the HD650 to start off with I didnt think the improvements were enough to warrant a change of opinion...

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I've tried this with my HD600s and my HD650s some time ago when I heard that driving the Senns balanced makes quite a difference.

The amp was a balanced 2x60W C.E.C. Amp3300.

When I reported the results of my listening tests at a german forum mostly populated by hardcore sceptics (the "all digital sources and all decent amps sound the same" crowd).Everyone tried to convince me that I'm fooling myself since there is no technical reason for the major changes I was hearing.

It was amusing.I'm sort of a sceptic myself and the difference wasn't subtle, but theory told them I'm wrong and they are right and when I insisted on what I heard my reputation was seriously damaged.

In the end it was not practicable though.The loudspeaker amp did have too much gain for the headphones.I had to be very careful with the volume knob and the pot behaved quite crappy between 07:30 and 08:30.

Balanced operation made a significant difference, but at least my speaker amp didn't turn the Senns into a giant killer.Better, yes, but still not in the same league as my Stax SR-007s.

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I don't know anything about the theory behind it all, I'm a marine zoologist-in-training, but I see it like this. Please correct me if I'm wrong.

In a single-ended system, the motive force is applied in one direction only, with the voice coil moving back in the other direction under the tension of the membrane. But in a push-pull system, the membrane is pushed in both directions by the motive force and the tension of the membrane is far less relevant. If you have an underdamped membrane, which the HD650 does (though to a lesser extent than the HD600), you don't have much in the way of membrane tension, so the difference between the membrane snapping back under its own tension and it being forced back by the signal is major. Also, I believe that in a SE system, if let's say you have a signal from 0 to +4V, the average position of the membrane will be at +2V, whereas in a push-pull system the average position will be at 0. At 0, membrane tension doesn't apply, and the membrane should be faster to respond to a push-pull signal.

Am I making sense?

As far as the sonic difference goes, it's not subtle. It may as well be a different headphone entirely. Transparency, impulse response, resolution, and control are not things that I associate with the HD650 normally; in every other rig I've heard it has failed miserably at all of them. Here, though, it might as well be an electrostat. Not as fast, perhaps, and not as airy, but just as detailed, transparent, and a lot more impactful.

I wish I had an O2 on hand to compare it to. But, once I've got silver cables in this rig, and a more neutral source, I'll drag it to the NYC meet and see where it stands. With the old cable and my current source it's far too warm and isn't quite ready to be shown to the general public yet (that, and I don't have my balanced cable anymore :( WTB faster build time for Headphile). Though now that I'm more used to a warmer tone, the O2 is very high on the "to get" list, I just need to sell off the K1k and H2 first. I'm betting the Dareds will drive it quite well through an SRD-7 Pro. They're really one hell of an amp for the price.

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Any future headphone purchases I'd consider would have to be driven in some way by a speaker amp. I thought that, as far as dynamic headphones were concerned, tis might limit options to the K1k and the K340, but if the HD650 likes it too then great. I liked the HD650 far more than the K340 during my previous ownerships with them. And the HD650 is one of the headphones I've let go of that I do sometimes miss, along with the BabyStax, HP-50A and the Ergo 2.

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I don't know anything about the theory behind it all, I'm a marine zoologist-in-training, but I see it like this. Please correct me if I'm wrong.

In a single-ended system, the motive force is applied in one direction only, with the voice coil moving back in the other direction under the tension of the membrane. But in a push-pull system, the membrane is pushed in both directions by the motive force and the tension of the membrane is far less relevant. If you have an underdamped membrane, which the HD650 does (though to a lesser extent than the HD600), you don't have much in the way of membrane tension, so the difference between the membrane snapping back under its own tension and it being forced back by the signal is major. Also, I believe that in a SE system, if let's say you have a signal from 0 to +4V, the average position of the membrane will be at +2V, whereas in a push-pull system the average position will be at 0. At 0, membrane tension doesn't apply, and the membrane should be faster to respond to a push-pull signal.

Am I making sense?

:doghuh:

Sorry, just had to use that...

In a single ended system, the output swings both positive and negative. For example, a sine wave will of 1Vpp will swing from 0.5V to -0.5V.

In a balanced system, I believe the membrane is driven by both the + and - outputs at 180deg. phase difference? (could be wrong...). So one side is pushing the membrane and the other side is pulling it at the same time.

I'll probably get crucified for this, but the only time I listened to HD650s was at a meet, both balanced and single ended... I didn't really care for them. Large symphonic was just too syrupy. Damn comfortable though.

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Nah, don't worry about laughing at my ignorance. That's why I'm going through this - to be less ignorant in the long run, and to try and understand the physics behind what I'm hearing, even though I have no physics education whatsoever.

So, in a SE system, the signal varies from + to - voltage but the force is applied in only one direction, whereas in a balanced or push-pull system the force is applied in both directions simultaneously, and the net force difference is what moves the membrane?

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I don't have the cable at the moment, but I will have one on Wednesday and I will try them again. It will be interesting to hear how it all stacks up now that I know what to expect and don't have new toy syndrome playing with my brain.

Going from memory...

I did use the HD600 initially and it didn't even occur to me to use the HD650 given how much I preferred the HD600 single-ended. Off the speaker amp, the grain was gone, the bass tightened up a lot, and the sound was even more forward and aggressive. It really was a very punchy, impactful headphone with a lot of heft to its sound, and on some of my jazz/fusion recordings it kept impressing me with how very present and right there the instruments were. It still didn't wow me with its detail, the soundstage was smallish, and imaging wasn't very good. All in all, it was a fairly different animal from the HD650, more natural and more impactful but nowhere near as detailed and technically refined.

I will listen more when I have the cable and report what I find.

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Joe Grado designed a simple attenuation cable for running headphones from speaker amps. I'll post a copy if I can find it. Basically, in each channel, you put a 20 ohm resistor in the "hot" lead. A 2 ohm resistor goes from the "hot" lead (before the 20 ohm resistor) to ground, if I'm remembering it right. You use fairly high wattage resistors for this.

This is done with dual banana plugs. Putting a plug into the speaker amp outputs the wrong way might be less than ideal ... :P

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I think that the biggest part of the magic that I'm hearing is that it's a push-pull amp, so I'm getting most of the benefits of balanced drive without basically paying $$$ for a nice balanced headphone amp. I don't think that being a speaker amp per se has anything to do with it.

Still, if we do have a way to run headphones reliably from speaker amps, just think of the system matching possibilities!

Also, sonically speaking, the VP-20 is one hell of a little amp for the money. It really does sound good.

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That's what I was thinking, but for me that seems unfortunate. Most people praise the HD650's balanced, but I don't really notice much change in them between balanced and single-ended...maybe a 5% difference, certainly nothing like what you've described.

It's actually something that's been bothering me a bit, lately. I've thought of posting a new thread to ask opinions on balanced vs. single-ended as in my experience it's not nearly the change most people make it out to be.

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i wonder how it would sound to do that with HP-2s and attach them to a really nice power amp.

Well, I would imagine if you really wanted to hear how your amp actually sounds like, that would be the way to go...the HP-2's are neutral and transparent enough to actually hear what your gear sounds like without the room imposing its sound signature on your rig. So I would imagine pretty damn f'ing good.

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I was waiting till I could borrow a 650 to try out before commenting. Maybe it's because I only have a Technics receiver/integrated amp that I picked up from the pawn shop for $20, but my observations don't really jive with those of catscratch. I also rebuilt my 8W p-p tube amp, but it didn't fare much better than my receiver. The best match is my K340 amp, running 6BX7 output tubes, which I find to be too bright and lacking in bass with any of my own headphones, but even then it still didn't match my K340, let alone my RS-1.

I didn't think there was a monumental improvement when driving the 650 with a p-p amp, the Technics was about on par with my DIY Gilmore Lite while the 8W tube amp was a bit better, and my K340 amp was another step up. On the other hand, the 650 out of the headphone jack of the Technics is quite possibly the best match for my turntable out of all the headphones I have. It sounds damn good with vinyl, but with digital it sounds pretty meh. My new working theory is that Senns are voiced for analog playback systems.

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  • 1 month later...

OK I've given this an extended try...

I had brought out from storage an old Bryston B60R SS integrated amp (60wpc/8ohms) to use with my K1000. Then I got a dedicated tube amp for the K1000, and intended to mothball the Bryston again. But since I have my Senns (580/650) on balanced cables to 4-pin XLR, and a K1000 4-pin to speaker wire adaptor, I thought I'd try this. First a bothersome low-level hum, but switching to optical feed on the dac instead of USB helped to addess. The result, especially with HD650 is more than noticeable -- everything seems more fleshed out, instruments/notes are separated, overall a punchy/full/detailed sound. A good example is I can easily follow a meaty bass line over the rest of a dense song. in fact, the cleaned up and tightened lower freq. is what I like best. The 580's respond as well, but too forward and in my face (back to kind of Grado land).

This has segued from experiment to semi-permanent arrangement -- miniDAC/B60R speaker taps/XLR speaker adaptor/HD650 Zu 4-pin XLR. Right now, about 70% of my listening is on this setup (K1000/Almarro is kind of like the sports car that you take out for a spin on weekends). Of course I paid good money for the Bryston in its day, but this feels like a free upgrade.

(I've got an upgraded XLR speaker adaptor on order and I'll use that separately with the K1000/Almarro).

Reading this thread, seems like mixed results, any others who have tried this?

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for those who has used the speaker amp to drive their headphone, can u please post picture of your connection. i like to try it out myself with my speaker amp. i assume if u are going to use the xlr connection, u will have R+,R- from speaker amp connected to +terminal and ground terminal on the right side of the headphone? do u have to put any resistor in between to ensure safety of operation?

that Joe Grado design really puzzled me, it's going into a 1/4" stereo connection, would that mean it will end up still single ended?

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Hi MV, I'm just using stock k1000 speaker adaptor pigtail (I'm not qualified to tell you how the pin outs should go on the 4-pin XLR).

I encourage others to try this. Doesn't seem universally applicable, but works for me in a HUGE way with my B60R. Enough so, I went down to a CA dealer yesterday and picked up a 840c. I'm getting 'word-class' sound -- by that I mean up to snuff with PS1, L3K/DHA3K that I had previously, and equally enjoyable compared to my K1000/Almarro (actually better tight and tuneful bass). Real happy with how this sort of fell in place, almost "there": (1) need to get a longer XLR to RCA interconnect to run 840c simultaneous to Almarro, while running RCA out to B60R; (2) waiting on an upgraded speaker adaptor to run k1000, so I can continue to use stock adaptor with Senns and B60R.

Forget e'stats (for now); relegate the other stuff for office/bedroom or sell-off. Here's a shot of current status -- see Almarro crying in the corner because B60 R wasn't mothballed...

840c.jpg

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