[analogsurviver]

   
Loudspeaker with K1000 drivers .... very interested 

 
I own a K501 (get it from an ex AKG stuff member) , I had a K1000 for a while (loan from an AKG stuff, bust get them back) and now I have the new K812 Pro
 
All this offers another line of music presentation in contrast to the K/Q7xx line.
 
Have you some contact to ex AKG stuff members, please send me a PN/PM

Loudspeaker consisting out of AKG K1000 drivers would be awesome - but an even more outlandish "loudspeaker", both in price AND performance, did exist for a brief moment in the early 80s of the previous century.
 
It consisted out of several hundred per channel of the then top of the line Bruel & Kjaer microphones in paralell - driven in reverse. I got this piece of information during the official B&K presentation of then brand new 4006 microphone, early 80s. That must have been world's best "loudspeaker" ever - BY FAR.
 
Unfortunately, I do not even dare to start to think what those babies would do to one's wallet...considering that a single pair of comparable Bruel & Kjaer (or DPA these days) microphones set you back for approx 5K ...

 

[hrklg01]

Hi,
The original idea behind that speakers with K1000 drivers was to compare the "openness" of the sound with elextrostatic state of the art speaker.
The disadvantage apart from the cost are too less bass response due to the too high resonance frequency of the drivers.
However if paired with a bass box with x-over at 40 Hz it sounds really great.
BR heinz

 

[Marabu]

Hello Heinz,
 
great insight on this headphone. So I reconnected my one after about 10 years again. Unfortunately there are low frequency distortions in the left. Anything you recommend to do? Thanks.
 
And a Hello from the netherlands to all forum members of course.

 

[hrklg01]

Are the distortions harmonic or non harmonic ones?
Can you measure that?
BR Heinz

 

[Marabu]

Can't measure, it sounds quite harsh. As my technical English is quite bad, l ll explain in german:
Die Verzerrungen hören sich schnarrend an, als ob die Membran Kontakt hat oder ein Fremdkörper im Weg ist, oder defekt ist. Allerdings ist im ausgebauten Zustand nichts davon zu sehen. Mit einer starken Lupe ist eine sehr kleine Anomalie auf der Membran zu sehen, wie eine Vernarbung, aber kein Riss. Ob dies ursächlich ist, weiss ich nicht. Meine Kenntnisse und Fähigkeiten sind auch begrenzt.
Am liebsten würde ich das Gerät zu Ihnen nach Wien senden.
Was kann einem K 1000 Besseres passieren, als vom Entwickler geprüft und ggfs repariert zu werden!
Danke auf jeden Fall für den Input.

 

[jpelg]

Herr Heinz - have you had an opportunity to hear AKG's latest flagship, the K812? If so, thoughts or comparisons to the classic K1000?

 

[hrklg01]

Hello,
'Don't think that your english is bad - it's the opposite!
At least much better than my one!
Howver, I try to answer in German also with the meaning ... "let's see!"  
Guten Tag,
Ihr Vertrauen mir das gute Stück zu schicken ehrt mich! Das Problem ist jedoch, daß ich hier zu Hause auch nur eine kleine Werkstatt mit sehr beschränkten Mitteln habe.
Da Sie aber melden, daß das Geräusch eher "schnarrend" - vielleicht kratzend ist!? dann klingt das wirklich nach einem Fremdkörper - vermutlich Schmutz im Luftspalt des Magnetsystems zwischen Eisenteil und Spule...
Ich denke nicht, wie Sie das Geräusch beschreiben, dass ein Membranfehler die Ursache ist...
Haben Sie so etwas wie einen Tongererator bei dem Sie eine Sinusschwingung in der Frequenz variieren können? Mit einem solchen Signal können Sie problemlos feststellen ob es eine halbwegs konstante Frequenz gibt, bei der das Signal verzerrt wird. Zum Beipsel bei der Basis- Resonanzfrequenz des Systems. Wenn dem so ist, ist es unwahrscheinlich, dass es sich um einen Membranfehler handelt.
Haben Sie schon mal versucht das AKG Service in Wien zu fragen? 
Falls Sie den K 1000 schon bzw. noch zerlegt haben, könnte ich jedoch auch den fraglichen Lautsprecherteil mir selbst ansehen. Nur zerlegen möchte ich das gute Stück nicht selbst!
Liebe Grüße Heinz Renner
PS: Sie können mich auch anrufen oder persönlich schreiben unter:
+436641218844
heinz_renner@yahoo.de

 

[hrklg01]

Hi, yes I had the chance to listen to the K812. A very good friend of mine has it.
For me - it's really a good headphone, however a "headphone".
What I mean with that is, that at least to me, the sound impression is not that "open and free" more inside the head - as the K1K offers. The reason for that is that the acoustic "impedance" is larger due to the relative closed cushions.
Or in other words, the acoustic mass is higher compared to the K1K.
The opportunity is of course that the bass level is much higher and its easier to wear on the head.
Another disadvantage is, that many people start to sweat between the ears and the phone.
However, I like it a lot too! Especially when I have to move while listening. Normally I use the old K240DF also when I'm in this mode...
Best regards, Heinz

 

[qazxsw80]

The K812 have kind of bad measurements, the level of disortion is pretty high, especialy under  100 kHz and between 1kHz and 3 kHz and the freaquency response is very rough above 2 kHz. Is it because of strong magnets or maybe something with the costruction of the cup? Is it possibly to fix it by making some kind of new revision, let say changing material or the form of the ringes of the driver?

 

[hrklg01]

Hello,
Good measurements!
However, it's for me not clear on which type of artificial ear it's measured. Can you clarify?
I do not know much about this type of headphone, because it was developed long time after I left AKG.
High frequency distortions can be caused mostly by membrane problems.
But the question is first: Can you hear it? Are the distortions you measure really audible?
If yes, The best way to check root causes is to reduce the input level and check if the SNR will stay the same or not. If it stays almost the same, than the root cause is most likely the membrane itself.
If it's so, a very liitle amount of thin film damping glue can help a lot - like a kind of very thin lacquer on the membrane. 
The disadvantage of this methode is, that such laquer is capable to get sticked a lot of dust on it's surface during use....
This is why I do not generally recommend this method to improve a headphone. It's only great help if the user takes care and protect the headphone against dust.
BR heinz

 

[Don Quichotte]

Hello Mr. Heinz!
 
Regarding the K1000 I have a couple of questions. I have tried to clarify them before, but I don't remember having received a definite answer:
 
1. What is the maximum acceptable level of DC offset at the amplifier's outputs?
2. I remember reading that the (/ some?) class T amplifiers have elevated HF response if the impedance they "see" at the output is high. There was some concern about a certain (high) amount ultrasonic noise such amplifiers would inject into the K1000 due to their 120 ohms impedance. In this regard, I'd like to know if:
a) such noise could be detrimental to the K1000 drivers, and
b) the K1000's drivers would naturally filter that noise or they would actually reproduce it, inaudible but perhaps potentially harmful for the user's hearing on the long term?
 
Thank you very much, we all appreciate your participation to this thread!

 

[hrklg01]

Hello,
I try to answer your specific questions as good as possible. But please understand, that I can only recall out of my brain what I designed during year 1988...
 
add. 1.) The K1000 is relative uncritical to DC offset sue to it's extreme large possible linear membrane excursion. This is based on the specific membrane design with the cutted edges.
But the possible DC offset is depending on the polarity. It means, if the polarity is in the direction that the membrane shift to the outside of the magnetic air gap, than it's fine. If it pulls the membrane towards the inner side, than the offset limits the maximum power.
 
add. 2.) I do not much know about the specific amplifier behaviers. But one thing is very clear: The design of the K1000 voice coils shows an acoustic shortcut at very high frequencies based on a aluminium coil carrier which is not electrically open. This design was choosen to get more damping at higher frequencies. This means that the membrane limit the high frequencies with - 6dB/oct. above 25kHz (if I remember right)
Therefore there can not do any harm for human ears based on ultrasonic.
 
BR heinz

 

[Don Quichotte]

Thank you, Mr. Heinz!

 

[hrklg01]

Hello to All who have problems with K1000 distortion's and/or Rub&Buzz:
 
'had the chance to get from one great guy of this forum the K1000 drivers to repair.
The problem was - as it seems often in this forum - Rub&Buzz or also named distortions....
 
As already described several possible reasons of this problem, I detected another one which is:
A poor membrane fixation process at AKG
(Sorry AKG - but this is really poor workmanship!)
 
To fix the problem the best way to do is following:
Get the glue type "Ponal Wasserfest" (it's a specific waterproof white glue where workers normally fix wood),
dispense little amounts of this glue to the normally fixed edge of the membrane between membrane and the frame. Do not worry! You can use relative large force there and shift with it the membrane some millimeters, the membrane is robust!
The glue will slide under the membrane/frame and after one day (sorry - you have to wait!) everything is fixed elastically well.
On the picture below, you see the glue as it's slided below already - white colored!

 
I'm writing this because - this failure can happen very often by the latest used glueing method. SORRY for this - but it was a process installed at AKG some time after my left from there....  
 
This is the reason because I did not mention it earlier in this forum, because I just did not know that the glueing process was altered.
 
BR your's Heinz Renner

 

[Marabu]

A very big thanks and thumbs up to this wonderful forum member.
My K1000 is playing now flawless as the faults mentioned in this thread were perfectly repaired.