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The Koss ESP950 thread (ESP owners, please contribute! :) - Page 6

post #76 of 346
10/19/07 at 3:01pm
Quote:
Originally Posted by AudioCats View Post
Can somebody provide some info on how the ESP9, when driven by an E9 box, compares with a Stax electrect such as SR-40/80 driven by a transformer box like SRD-4? sound quality wise.
Birgir? Edstrelow? ericj? Anybody?

Thanks!
.

I had both of these at one point and felt both were fine phones. The big plus with the ESP 9 , which I still have, is that it provides a great deal of attentuation of external sounds. It has good bass and dynamics which depends somewhat on the supporting amplifier.

The electrets, which I did not keep, were decent but with no noise attenuation and not such solid bass. They are very light compared to the ESP9.

I personally think that these electrets, and many Stax phones have a somewhat honky mid/upper midrange which I really notice when I compare them to the Koss ESP9.

One other plus with the electret is that it should be able to be run off a Stax amp as well as the transformer. So far the ESP 9 eludes my ability to get it to sound good on an amp.
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post #77 of 346
10/20/07 at 12:15am
Thread Starter 
Interesting, some like the ESP9 less, some like it more. I need to find a pair of each and take a side

How bad is the ESP6 when compared with the ESP9? I do realize the transformers are different though...

Edstrelow: just ran across one of your old post on headwize about the ESP9/stax amp situation: I think the ESP9's bias is at least 360V (if not 450 or higher), that might be why the 230V bias stax amp can't drive it well?
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post #78 of 346
10/20/07 at 12:58am
Thread Starter 
One question about the ESP9's bias: is it really higher than the ESP6/7's?

It has been confirmed that the 7 has a bias of 360v (4x 90v zeners), and it appears that the 6 has about the same circuit as the 7, just the circuit is in the ear cups, so the 6's bias is likely the same, 360v.

Now when I check the E9's schematic, it also shows 4 zeners, can anyone please check what voltage these zeners are? My thought is they might be the same as the big zeners in the E7 box (for logistic reason), then the voltage might be 360v too? What does the documentation indicate? Or can anyone with a E9 box please measure the actual bias voltage?
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post #79 of 346
10/20/07 at 6:10am
Quote:
Originally Posted by AudioCats View Post
How bad is the ESP6 when compared with the ESP9? I do realize the transformers are different though...
They sound pretty similar though I did the comparison on a 400v bias unit I built and leached the drive voltage from my T1 amp. As the original damping was beyond being dead on both units I made my own so both phones have the same damping structure and no PCB's installed in the cups.

Quote:
Originally Posted by AudioCats View Post
Edstrelow: just ran across one of your old post on headwize about the ESP9/stax amp situation: I think the ESP9's bias is at least 360V (if not 450 or higher), that might be why the 230V bias stax amp can't drive it well?
The Koss drive circuit is very different form the Stax counterpart as they drove them semi single ended to diminish the effect of the closed housing.

Quote:
Originally Posted by AudioCats View Post
One question about the ESP9's bias: is it really higher than the ESP6/7's?

It has been confirmed that the 7 has a bias of 360v (4x 90v zeners), and it appears that the 6 has about the same circuit as the 7, just the circuit is in the ear cups, so the 6's bias is likely the same, 360v.

Now when I check the E9's schematic, it also shows 4 zeners, can anyone please check what voltage these zeners are? My thought is they might be the same as the big zeners in the E7 box (for logistic reason), then the voltage might be 360v too? What does the documentation indicate? Or can anyone with a E9 box please measure the actual bias voltage?
I've given up on the /E.9 and can't be bothered with it. It's a huge rats nest of wires and connectors that come off easily.
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post #80 of 346
10/20/07 at 7:54am
Thread Starter 

ESP9 bias voltage = 720V

found some info here, which indicates the ESP9 diods are 180V (!) each, twice the voltage of the ESP7 diodes, making the bias voltage at 4x180=720v!! Holy cr#$%, that is a lot of bias voltage.

No wonder a LB Stax amp couldn't drive them....... Maybe a pro biased amp will do alot better?
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post #81 of 346
10/20/07 at 8:21am
Thread Starter 

ESP info list updated

updated ESP info list (post #31), including some of the E90 and 950's specs.

By the way, according to the Koss manual, the E90 power supply is 9V DC/1A...........
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post #82 of 346
10/20/07 at 8:49am
Quote:
Originally Posted by AudioCats View Post
found some info here, which indicates the ESP9 diods are 180V (!) each, twice the voltage of the ESP7 diodes, making the bias voltage at 4x180=720v!! Holy cr#$%, that is a lot of bias voltage.

No wonder a LB Stax amp couldn't drive them....... Maybe a pro biased amp will do alot better?
I've read a few times that it is closer to 400v. The low bias energizers can drive them just fine but you can't just plug them into a Stax socket unmodded. Part of the circuit is inside the phones you you won't hear any thing unless that is bypassed and connected directly to the 3 connection points.
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post #83 of 346
10/20/07 at 9:04am
Thread Starter 
hummmm, which one will it be, 400? 470? 720?

Birgir, can you set your E9 to AC mode and measure one of the zener's voltage? Please please, really curious now..... (and while you are at it, how about doing the same on the E10 )

Thanks


.
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post #84 of 346
10/20/07 at 9:36am
Quote:
Originally Posted by AudioCats View Post
hummmm, which one will it be, 400? 470? 720?

Birgir, can you set your E9 to AC mode and measure one of the zener's voltage? Please please, really curious now..... (and while you are at it, how about doing the same on the E10 )

Thanks


.
I'll do it if I have some time to kill and I can find the /E.9.
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post #85 of 346
10/20/07 at 9:53pm
Quote:
Originally Posted by AudioCats View Post
How bad is the ESP6 when compared with the ESP9? I do realize the transformers are different though...

Edstrelow: just ran across one of your old post on headwize about the ESP9/stax amp situation: I think the ESP9's bias is at least 360V (if not 450 or higher), that might be why the 230V bias stax amp can't drive it well?

I have both now working fairly well. I think the ESP9 is the way to go but the 6 is interesting. Possibly I have a sentimental regard for them because they were my first phones. But I really have to hook them up simultaneously to an amp with 2 sets of speaker connectors.


I have run the ESP 9 phones direct from Stax amps, having got rid of the crcuitry in the cups. I got hardly any sound from a low bias amp. I am hearing music from the high bias amp, but it just doesn't sound very full or dynamic.

I am curious what Spritzer means about "semi single-ended." Possibly that is the clue to what they need.
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post #86 of 346
10/20/07 at 10:02pm
Thread Starter 
Looks like somebody should re-cable a ESP9 and plug them into a Blue Hawaii. Maybe the amp can then over power the evil "semi-single-ended" thingy and make the 9's sing...
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post #87 of 346
10/21/07 at 7:12am
Quote:
Originally Posted by edstrelow View Post
I am curious what Spritzer means about "semi single-ended." Possibly that is the clue to what they need.
They put a diminished signal on the back stator to lessen the effect of a closed housing on the back wave. Driving ESL's single ended is a very, very bad idea resulting in some 7% or more THD because there is no way for the film to regain its former position. A push pull nature eliminates this problem so you can get away with using lower voltage on one stator without producing much distortion. This is the reason why the ESP6 through 10 sound so different on Stax amps as they are putting out a symmetrical signal.

Quote:
Originally Posted by AudioCats View Post
Looks like somebody should re-cable a ESP9 and plug them into a Blue Hawaii. Maybe the amp can then over power the evil "semi-single-ended" thingy and make the 9's sing...
You'll burn up the Blue Hawaii (or any Stax amp) if they would be forced to push huge amounts of voltage. Though there are 5 pins on the plug they are not L+.L-,R+,R- and bias. Instead there is GND, R+, L+, bias, bias. It's easy to use them on any Stax amp if you simply bypass everything that is inside the cups and go directly to the stators and diaphragm. I did use my 400v bias module though.
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post #88 of 346
10/21/07 at 11:18pm
Thread Starter 
How does the ESP9's bass compare with the ESP6's? (I only know what the 7 sounds like, and nobody has a 7....but the 6 should be close enough)
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post #89 of 346
10/21/07 at 11:29pm
Quote:
Originally Posted by AudioCats View Post
How does the ESP9's bass compare with the ESP6's? (I only know what the 7 sounds like, and nobody has a 7....but the 6 should be close enough)
I'll tell ya when my ESP6 shows up

And sorry i haven't cracked open my working E.9 to measure voltages. Maybe after work tomorrow.
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post #90 of 346
10/22/07 at 3:15am
Thread Starter 
Quote:
I'll tell ya when my ESP6 shows up
so you bought that pair of $13 ESP6? Good thing I didn't bid more, wasn't sure if I really wanted it



Any possibility of a comparision impression on ESP9/E9 vs. SR-001 system from some of you that own both? I will guess the baby stax will win, but by how much ? I think alot of people will be interested in such review since these two are about the only common and affordable non-leaking electrostatics available. ( There are also 6,7 and 4070, but the 6 is too heavy, the 7 is too rare, and the 4070 is way too expensive for most of us) Thanks
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