Neumann KH120A noise issue ...ANYONE?

[btyreman]

Hello I have a noise issue with my neumann kh120A speaker, the left speaker started making a noise about 1-2 months ago, here are some audio examples which you can download:

for the recording I sweep a microphone in and out of the tweeter zone sweet spot

left (problem) speaker:

https://www.dropbox.com/s/294pq46bytr72m5/left_speaker_noise_mix.wav?dl=0

right speaker with no issue for reference:

https://www.dropbox.com/s/aq8w0iq8k32y2rc/right_speaker_noise_mix.wav?dl=0

can anyone here identify what's wrong and what could cause it? I have tried getting inside the speaker and am willing to repair it if necessary, I am planning on contacting neumann but would like to know at least what the issue is with them.

Any help will be really appreciated,

regards,

Ben.

 

[btyreman]

bump  nobody?

 

[moamps]

First check the switches on rear panel for oxidation an dirt. Switch the speaker of and move/exercise  all switches several times.
If noise is still there, move the speaker to another room and power it on and check it to be sure that the noise doesn't come from an outside EM source. The last, the cause can be SMPS inside the speaker, open the speaker, make a high quality picture and post it here for further analysis.

 

[btyreman]

First check the switches on rear panel for oxidation an dirt. Switch the speaker of and move/exercise  all switches several times.
If noise is still there, move the speaker to another room and power it on and check it to be sure that the noise doesn't come from an outside EM source. The last, the cause can be SMPS inside the speaker, open the speaker, make a high quality picture and post it here for further analysis.

hello I have already tried moving the switches and no joy, I currently do not know how to get inside the speaker, there are four screws in the back but it doesn't seem to come open when you try, I will upload high quality photos soon. What is SMPS?

 

[rock soderstrom]

What is SMPS?

https://en.wikipedia.org/wiki/Switched-mode_power_supply

 

[Khron]

There's very likely some sort of (rubber) foam gasket between the rear panel and the enclosure itself, and that can be a bit "sticky" and stubborn sometimes.

I currently do not know how to get inside the speaker, there are four screws in the back but it doesn't seem to come open when you try, I will upload high quality photos soon.

 

[pvision]

If you can't get inside it you're unlikely to be able to fix it. The KH120 is a one-board design, all surface mount, has lots of power supply components and a switched-mode power supply

I gave up and sent mine to Sennheiser for their fixed-fee £240 repair service

Nick Froome

 

[btyreman]

I've had a look inside and can't work out what is wrong with it, good news is I eventually worked out how to open it up, there was nothing obvious visually on the circuit like a blown capacitor and the components were all top quality, but there is clearly something wrong, I am a bit apprehensive about uploading photos because of being sued by neumann/sennheiser, is it allowed legally to do this?

for now I re-assembled it as they're my main monitors, the noise has been driving me crazy though, so for 90% of listening I am just using one speaker and summing to mono

any thoughts?

cheers,

Ben.

 

[btyreman]

If you can't get inside it you're unlikely to be able to fix it. The KH120 is a one-board design, all surface mount, has lots of power supply components and a switched-mode power supply

I gave up and sent mine to Sennheiser for their fixed-fee £240 repair service

Nick Froome

thanks I will likely end up doing this when I have the money set aside, I am not sure it's within my skill set or capability to repair this one.

 

[Tubetec]

Seems to be a common enough story with many active monitors , a few years down the road and something goes pop ,
I did have my eyes on a set of K&H 110P at one point the predecessor to the Neumann KH120 but in passive format , specs fall a good bit short of the newer Neumann though.

 

[pvision]

My KH120 is back - shipped to them just before Christmas, back two days ago. £240 inclusive repair fee

By comparison a pair of JBL LSR305Ps was £219 inclusive, delivered

On balance I do think that the Neumanns justify their price - particularly as they seem to have become quite a bit cheaper recently

Nick Froome

 

[andre tchmil]

I have a pair of 120's and the slightly smaller ones in my office( don't know the type ) . Great speakers I can say after having  Genelecs, Adam, NS10, JBL, Quested, Dynaudio, ........


Any idea what they replaced ?

 

[btyreman]

bad news guys, the second speaker has also started making a simlar noise, but for about 1-2 minutes after you turn it on, then it goes back to no noise, very strange, I can do a recording of it, the noise reminds me of 1970s atari games, it reminds me of 8 bit noise, that's the best way I can describe it, I'm guessing it's the drivers going? no idea...

with corona going on I'm thinking of giving it a go at trying to fix it and look inside, but I'd need some help/guidance.

 

[Khron]

The drivers themselves can't "make" noise on their own (unless they make "extra" noises during sound reproduction), so the source of the noise will likely be in the electronics.

 

[btyreman]

here's a recording I made of the noise, as you can hear it's quite horrible, but goes away after about 5-6 minutes, if anyone has a clue what this noise means do let me know,

https://www.dropbox.com/s/mbcpimfq8r0qsvv/kh120a_right_switchon_noise.wav?dl=0

cheers,

Ben.

 

[btyreman]

here are some photos of the circuit, I am not sure where I would begin with testing? I can at least get inside now,  there are some adjustable pots near the back, any idea what they do? the blue things

any suggestions?

regards,

Ben.

 

[btyreman]

I have a pair of 120's and the slightly smaller ones in my office( don't know the type ) . Great speakers I can say after having  Genelecs, Adam, NS10, JBL, Quested, Dynaudio, ........


Any idea what they replaced ?

I used to own KRK V6 series II speakers, the neumann's are in a different league, it's a shame about the noise issues though, I predict that other people will get the same problems as me in time, although they have lasted 6 years which is pretty good, they've had a lot of use including in a commercial studio so some 16 hour sessions.

 

[moamps]

here are some photos of the circuit, I am not sure where I would begin with testing? I can at least get inside now,  there are some adjustable pots near the back, any idea what they do? the blue things

Most probably blue trimmers are used for adjusting active crossover and gain. Don't touch them, or if you like to do, first write positions or make a good picture of their current positions.
The sound clip you posted indicates to me a problem with switching power supply, that's the lower part on the board with bunch of capacitors, small inductors etc.
Could you please post high res pictures of front and bottom of the board?
First you can try is to replace capacitors in power supply, but which exactly I don't know right now without better pictures.
Be careful when you power it, there is dangerous mains voltage present at some points of the board.

 

[btyreman]

If you can't get inside it you're unlikely to be able to fix it. The KH120 is a one-board design, all surface mount, has lots of power supply components and a switched-mode power supply

I gave up and sent mine to Sennheiser for their fixed-fee £240 repair service

Nick Froome

was that just for one speaker or both?

 

[pvision]

was that just for one speaker or both?

£240 per speaker

Nick Froome