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Audible noise on Genelec 8351

musicmarc, modified 6 Years ago.

Audible noise on Genelec 8351

Youngling Posts: 8 Join Date: 1/6/16 Recent Posts
Hello,

I am using Genelec 8351 monitors for about 3 weeks in a stereo setup mostly for music listening. Unfortunately they produce audible white noise even at a 2 m distance when no audio cables are plugged in. At lower distance there is also a buzz noise audible from the woofers.
Formerly used monitors' noise wasn't audible at distances greater 1 m.

Is it a common problem or might it be related to something else?

Greetings

Marc
ilkka-rissanen, modified 6 Years ago.

Re: Audible noise on Genelec 8351

Yoda Posts: 2564 Join Date: 3/23/09 Recent Posts
Hi Marc,

Can you tell me little bit more about your system? Are you using analogue or digital signal? Are you using the GLM software? If yes, are you adjusting the volume from there?

Background noise is slightly higher if using the analogue signal. Volume setting in the GLM will also affect the noise level.
musicmarc, modified 6 Years ago.

Re: Audible noise on Genelec 8351

Youngling Posts: 8 Join Date: 1/6/16 Recent Posts
Hello Ilkka,

anlog inputs are used and the volume is controlled by a preamp. GLM hasn't been used yet. The noise is already audible at 2 m without any audio connections. Attaching the audio cable an powering on the preamp makes almost no difference.
ilkka-rissanen, modified 6 Years ago.

Re: Audible noise on Genelec 8351

Yoda Posts: 2564 Join Date: 3/23/09 Recent Posts
Ok, but you have the GLM? I would advice you to run the calibration and then set the GLM volume level to -10...-15 dB to reduce the overall input sensitivity of the speaker. Without any adjustment, the sensitivity is really high which will then manifest itself as slightly higher background noise level, especially when using the analogue input.
musicmarc, modified 6 Years ago.

Re: Audible noise on Genelec 8351

Youngling Posts: 8 Join Date: 1/6/16 Recent Posts
I haven't been using GLM, but used "System Level rotary control" to lower the gain, which didn't really help much.
At the weekend I got a chance to measure the sound pressure with a sound level meter. It was setup at 10 cm distance to avoid any residual noise from the surrounding and no audio cables where plugged in to avoid noise from the preamp. The reading showed a level of 50 dba, which would translate to about 38 dba at a 2 m listening position, which seems high too not notice with highly dynamic music material.

Would setting up the speakers with the GLM, reduce the background noise of the speakers itself or is it similar to the System Level rotary control?
ilkka-rissanen, modified 6 Years ago.

Re: Audible noise on Genelec 8351

Yoda Posts: 2564 Join Date: 3/23/09 Recent Posts
What type of sound level meter were you using? Unless it's an expensive professional model, its own noise is probably much higher than the speaker generates.

I took comparison measurements today in our anechoic chamber and using a professional SPL meter. At 10 cm distance SPL was about 30 dBA which translates to 4 dBA at 2 meter distance.

There seems to be something wrong with the calculation you present because 50 dBA at 10 cm would translate to 24 dB at 2 meter distance. Sound level attenuates by 6 dB per doubling the distance.
musicmarc, modified 6 Years ago.

Re: Audible noise on Genelec 8351

Youngling Posts: 8 Join Date: 1/6/16 Recent Posts
The Sound Level meter is just a semi pro and by far not as exact like ones from NTi audio, but should be in a window of 2 db from 30 db upwards regarding reviews.

My calcalution is wrong, somehow I have taken a start distance of 0.5 m.

30 dbA seems ok, since my older monitors where rated <8dB SPL @ 1m from specs, and weren't audible at 2 m distance. Is there a possibility that the noise gets influenced by other things like WiFi, Bluetooth ...?
ilkka-rissanen, modified 6 Years ago.

Re: Audible noise on Genelec 8351

Yoda Posts: 2564 Join Date: 3/23/09 Recent Posts
A good way to check if the meter is capable of reading low levels and whether the background noise of the environment affects the result is to measure the residual noise by turning off the speaker. If you have a quiet space and a low noise meter, you should see SPL around 20 to 25 dBA. Can you check that this is what you get? Can you post the model of the SPL meter you are using?
musicmarc, modified 6 Years ago.

Re: Audible noise on Genelec 8351

Youngling Posts: 8 Join Date: 1/6/16 Recent Posts
The model is a Sper Scientific Type 1 SPL meter, it is only capable of reading from 30 db upwards. Room background noise doesn't show any oscillation as long I am at least 1 m away from it.
ilkka-rissanen, modified 6 Years ago.

Re: Audible noise on Genelec 8351

Yoda Posts: 2564 Join Date: 3/23/09 Recent Posts
And how much is the room background noise?
musicmarc, modified 6 Years ago.

Re: Audible noise on Genelec 8351

Youngling Posts: 8 Join Date: 1/6/16 Recent Posts
The room background noise isn't measurable at the listening point or near the speakers, since the SPL doesn't work below 30 db.
ilkka-rissanen, modified 6 Years ago.

Re: Audible noise on Genelec 8351

Yoda Posts: 2564 Join Date: 3/23/09 Recent Posts
Do you have any additional info? Maybe a short video while you are taking a measurement?
musicmarc, modified 6 Years ago.

Re: Audible noise on Genelec 8351

Youngling Posts: 8 Join Date: 1/6/16 Recent Posts
I will try to make a video of the setup. Is it also possible to use the GLM set for measurements? I might be able to borrow one.
ilkka-rissanen, modified 6 Years ago.

Re: Audible noise on Genelec 8351

Yoda Posts: 2564 Join Date: 3/23/09 Recent Posts
GLM can be used for calibration purposes only, it can't be used for low level background noise measurements.