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8331 calibration and GLM3 software

smooshieface, modified 4 Years ago.

8331 calibration and GLM3 software

Youngling Posts: 3 Join Date: 3/19/19 Recent Posts

Hi Guys

I am a long time Genelec Classic Monitor Customer but first time user of SAM based monitors
I have just purchased a pair of 8331's.
In relation to room acoustics, I need some advice.
After calibration I seem to have a massive frequency hole in the right speaker between 60 and 90Hz with peak of -11dB at 81Hz
I thought initially this would be backwall cancellation but after trying the suggestions on the Genelec Site re Backwall cancellation i got little difference in the results. (speakers currently 6 cm from the wall.)

The Left speaker seems to be fine.

I bought some acoustic bass traps from sound acoustics australia and hae been placing them around the room but as I am someone with very little experience in room acoustics I really do not know what I am doing and everything I try does not make a difference. I have 4 panels dispersed around the room/

My room is a 360 Cm cube with a 550 cm ceiling. All walls are double brick with plaser on top.
Roof is insulated plasterboard.
Unfortunately I do not have the ability to significantly alter the walls or hang a cloud
Any tips or suggestions would be greatly appreciated.
Even if its to just compensate somewhat as I uderstand the limiting factors I am dealing with.

One last thing, after setting up the monitors, it seems I need my computer and GLM running to get any sound out of the speakers.As a pervis classic monitor user I just want t be able to use the monitors without having the software running, is this possible or am I doing something wrong?

many thanks


jantex, modified 4 Years ago.

RE: 8331 calibration and GLM3 software

Padawan Posts: 36 Join Date: 3/11/15 Recent Posts

Your issue is most probably related to the modal interference of your room. Since your room is unfortunately a cube with quite small dimensions apart from the celiling height it might be a very difficult room to get the low end right. Looking at the picture you posted, your speakers are not positioned symmetrically in relation to the left and right side wall and there is more distance from the right wall to the right speaker than in the case of left speaker in relation to the left side wall. So since you moved the speakers close to the front wall, you shifted SBIR much higher and it is definitely not the front wall contributing to the dip you are experiencing. You will probably get bigger variation and bigger chances of success with moving speakers 10cm left or right than with additional absorbtion, since these low frequencies need quite a significant amounts of absorbtion to be treated or some correctly tuned Helmholz resonators (tuned bass traps). So I think you should try moving the right speaker closer to the right side wall to see how the shift will progress.



smooshieface, modified 4 Years ago.

RE: 8331 calibration and GLM3 software

Youngling Posts: 3 Join Date: 3/19/19 Recent Posts


Hi Jantex

Thank you so much for your insights, it gives me something to work with. I will try relocating the speakers as suggested first then if not successful look at how I can make the positioning more symettrucal. Appreciate your input. Thank you





smooshieface, modified 4 Years ago.

SOLVED: 8331 calibration and GLM3 software

Youngling Posts: 3 Join Date: 3/19/19 Recent Posts

For those reading this thread I wanted to provide feedback based on Jantex's comments.

I tried relocating speakers but did not have much success, in fact the problem got worse.
I then focused on making the positioning of the desk more symmetrical with the room and BOOM, the bottom end Null dramatically improved on the right speaker, without causing any reall effects on the left speaker. Now I only have a small bell curve dip at 65 Hz -3dB.
Jantex you are a star, thank you so much. This community is fantastic



jochenschulz, modified 3 Years ago.

RE: 8331 calibration and GLM3 software

Youngling Posts: 5 Join Date: 2/24/20 Recent Posts

Good to hear you could solve the big acoustical problem with your speaker placement.

To answer your second question: I use the GLM software usually to adjust the volume, using the digital input without any other volume control. But still it should be possible to store the settings from GLMĀ to the speakers ("Store Group Settings", adjust the startup level). You need to switch one DIP on the back of each speaker to "stored ON". Otherwise the speaker will load the factory default when it's switched on.