[davstev]

HI Folks,

Not too long ago, I bought a near-mint, still boxed pair of early 70s, Koss ESP-9 electrostatic headphones. Obviously old, but in good cosmetic shape & seems barely used.

After several weeks I found the time to hook them up. I wired the E-9 energizer to the back of my Kenwood 700M (170W per channel), power amp. (Pretty sure I hooked them up right!)

The result was disappointing to say the least. The signal is barely audible (even when cranked waaaay up) and very distorted at that, and all treble. Just wrong.

My audio tech, who is quite knowledgable, says that there's a chance it's the membrane coating, which may have deteriorated with time. Says too, if not the membrane, then the polarizer could be the issue.

He'll get to the root of the problem, but in advance of me handing them over to him, wondering if anyone has any issues with electrostatic phones and membrane coating issues and would like to comment.

Thanks
David

 

[chinsettawong]

Hi David,

Since your headphones are old, yes, the coating can be an issue. But, first, please try to leave your headphones plug in the energizer for a few minutes (5-10 minutes) before you start listening. The old coating can possibly take longer time to charge up the diaphragms.

Wachara C.

 

[ericj]

Near-mint still-boxed is the sort of thing that would make me wonder if they were defective when new, thus packed back into the box for return to the original retail point of purchase.

I have a bunch of vintage stats, including esp-9 and esp-6, and marantz and magnavox and, uh, I forget. american company, big can headphones that are probably SR-5 drivers. (Edit: Superex. That's the one. The magnavox and marantz and superex all seem to have a variation on the SR-5 driver)

Anyway. Some of them needed to be hooked up for several minutes to 'charge'. Some of them needed to be opened up so that push-on connectors could be wiggled to renew connectivity.

But the coating isn't typically a problem. Never heard of it failing, really.

 

[davstev]

Near-mint still-boxed is the sort of thing that would make me wonder if they were defective when new, thus packed back into the box for return to the original retail point of purchase.

I have a bunch of vintage stats, including esp-9 and esp-6, and marantz and magnavox and, uh, I forget. american company, big can headphones that are probably SR-5 drivers. (Edit: Superex. That's the one. The magnavox and marantz and superex all seem to have a variation on the SR-5 driver)

Anyway. Some of them needed to be hooked up for several minutes to 'charge'. Some of them needed to be opened up so that push-on connectors could be wiggled to renew connectivity.

But the coating isn't typically a problem. Never heard of it failing, really.

 

[davstev]

Thanks for this, eric. Yes, I know what you mean about the defective thing, quite possibly was defective after purchase. Although, there are some very minor signs of use.

In any case, I have hooked them up for a lonnnnggg time to see if they would charge, and, no dice.

The signal is coming through, but very very very slight. Like, you have to turn it up to 3 o'clock on the volume dial to hear something. and it's very slight at that, and terribly distorted.

Can you explain what you mean by the push-on connectors needing to be wiggled to renew connectivity? Are we talking about the breaker re-set buttons on the back? Because i've tried pushing them in and they just won't budge.

I can see that you are pretty experienced with electrostatic phones, and you claim that coatings don't fail, yet other people say they do, and have supposed remedies (ie. coating with graphite). What makes you think they don't fail?

 

[ericj]

I think the koss connections are soldered but i don't remember exactly. I do remember that the foam rubber in mine was decomposing and i needed to clean a bunch of crap inside the cups.

koss still sells the oil-filled pads fwiw.

I mean on the SR-5 and some others, it's something like a faston or "spade" connector between the cable and the driver, and they needed to be wiggled to scratch away some oxide between the parts. I never loved the ESP-9 very much so i haven't messed with mine in years and years.

I don't recall seeing actual discussion where the coatings were found to have failed. Maybe i'm wrong or remembering wrong.

It would be best if you could try your headphones with a different energizer or vice-versa but it can be tough to find someone nearby who has one.

 

[ericj]

It's also possible that there is a bad switch contact or something.

Are you absolutely certain that it is hooked up correctly? Hook up speakers and make sure you get normal sound out of them?

There's also a concern where the e/9 energizer ties the negative sides of the input together, which makes it incompatible with amplifiers which have a bridge tied type output, or otherwise have an active rather than passive negative hookup. This means you can't use most class-D amps with it, for example.

 

[davstev]

Well, I am pretty sure they are hooked up properly, I just followed the instructions and triple checked. I haven't hooked up speakers to the E-9 though. I assume that would make no difference to the headphones performance, but, it would be good for troubleshooting, so I will.

Also, for the e-9 compatibility issue, I am using a kenwood 700M amp. I ran the schematic by my tech, and he said that the amp is grounded in a way that is compatible with the E-9.

If I may ask, what didn't you like about the ESP-9's?

My tech, btw, will soon be looking the whole thing over.