help with a 600-1,5khz dip please

[yass]

Hello slutz

Here is my question, if someone has an idea...

We have a little commercial studio in which we worked to improve teh acoustics the past two months.

We built basstraps, schroeder difusors, diffusors etc...

We have had a HUGE improvement, and the frequency curve and RT now show everything is fine except for the 600-1,5khz range, in which we have from 3 to 8 dbs dips.

Does anybody have an idea where this could come from?(speakers,diffusions,ceiling,placement...)

We did the measurements with HR824's, 1031's,1032's and Dynaudio AIR 12's.

The room is 5X5X2 meters.

The ceiling is covered with rockwool and mini schroeders.
We have 2 schroeders at the back wall (23 cavities), and 6 basstraps(corners and center of the front and back wall, and diffusor on the sidewalls.

Thank you very much for any ideas

YASS

[DanDan]

Yass, is your room really only 2M high? That would put the mini diffusors very close to ears and speakers.

Did you test with one or two speakers?

DD

[yass]

yes the ceiling is 2,05 meters but is covered with 5cm thick rockwool.

Do you think the problem might come from the low ceiling?

we did the measures with 1 and 2 speakers and the problem is less pronounced with one speaker.

ideas?

Thank you anyway.

Yass

[yass]

yes the ceiling is 2,05 meters but is covered with 5cm thick rockwool.

Do you think the problem might come from the low ceiling?

we did the measures with 1 and 2 speakers and the problem is less pronounced with one speaker.

ideas?

Thank you anyway.

Yass

[DanDan]

It might. 5 cm with no airgap behind is not really thick enough to have good action in the mid range. Also those diffusors in a tiny room....
Do you have a RFZ i.e. absorbent panels to the left and right of you between you and the speakers?
How did you measure? What software. Can you send me a file?
If you wish to do that use the email address at one of the websites below.
Or you could post the measurements here. Let's see a zoomed ETC of the first 10-20mS.
DD

[tINY]

Don't forget about reflections off the desk or mixer.

Near-Fields Handbook | Sweetwater.com




-tINY

[yass]

Thanks for your answers i'll post it tomorrow.

Thanks

Yass

[yass]

here are the curves of the 2 speakers together with and without EQ, and the reverb times.


Thank you for your time

YASS

[DanDan]

Yass, the looks very very good to me. You may have comb filtering, quite likely from the mixing desk or mouse keyboard table as tINY said. If you could display a zoomed bit of the ETC from the big peak to say 10mS we should be able to see a destructive very early reflection. Are those measurements with one speaker or two? Full range frequency response and ETC need to be done with just one speaker to avoid comb filtering caused by the different distances to each tweeter, and two sources messing up the ETC.

DD

[yass]

ok thanx for your reply.

These curves were measured with both speakers.

I post teh zoomed ETC on monday.

Thank you for your advices and time.

YAS

[yass]

hello

These are the waterfalls from 600hz to 2khz the 10 and 20 first milliseconds.

ideas about comb filtering?what to do about that?

THANX

Yas

[DanDan]

Hi Yass,
drive one speaker only. The comb filtering is caused by the two speakers.

DD

[yass]

Ok Dan

I'll do it today and post it tonight.

YAS

[yass]

Hello Dan

Here is a measurement with one speaker onlyand its waterfall and reverb times.

thanx

[yass]

this is a measurement with a HR824

[Seamus TM]

For the waterfalls, try a 500ms duration and -60dB decay.

On a related note, I find the default waterfall settings a bit useless.

[Weasel9992]

Originally Posted by tINY

Don't forget about reflections off the desk or mixer.

Near-Fields Handbook | Sweetwater.com

I agree. Have you tried covering the mixer or desk? If that's the problem you should be able to narrow it down right away.