measured my room, cancelation in freq. responce

[pronto]

hi there,

I have a cancelation at around 78 HZ.
If i move some inches away from front to back it still exists only the frequency is changing.


please take a look at the graph below...


room dimensions:

Length: 15´5" / 4.7 meters
Width: 11´9.7" / 3.5 meters
Height: 8´2.4" / 2.5 meters

[cborg]

Is it moving up in frequency as you move back?
What's your measurement positions for the different measurements?

[pronto]

hi

yes i am moving back starting from 1,4 - 1,6 meters


my small speakers a placed against the front wall near the corners, and will keep them there.

there are no Axial Modes that causes nulls in this area.

i believe its coming from the backwall.

what is the best place for a trap if you want kill a boundry problem? corner?

[ciro]

Some nulls are non modal - as the one you shows - it changes with mic (engineer) position.
Anyway, you already have a good position (brown (or yellow)) which gives you a good response , *exception* for the nasty peak around 150 hz.

Based on dimensions and my little experience,this peak is probably a height related modal issue.Treat your ceiling reflection point (with a cloud) + change monitors height a bit and see if helps.

Ciro

[pronto]

Originally Posted by ciro

Some nulls are non modal - as the one you shows - it changes with mic (engineer) position.
Anyway, you have a good position-response (brown (or yellow)) which gives you a good response *exception* for the nasty peak around 150 hz.

yes agree , but its too close to the frontwall

[cborg]

Originally Posted by pronto

i believe its coming from the backwall.

Well you're probably right even though other reflections may add to the energy. It is consistent (pretty much) with the distance to the wall and the increase in the dip when you move.

what is the best place for a trap if you want kill a boundry problem? corner?

Well, carefully selected areas at the back wall would be a start.

But be sure to weigh in any other problem you'd like to treat to your solution though.

[pronto]

i will measure after placing a trap,

but currently i dont have the amount of absorbtion material here to test.

with 2 thin fiberglass panels there is nothing to do below 100 Hz

[pronto]

okay i post post some waterfall plots and some floor plans.

[pronto]

okay some plans and a graphs from a simulation programm

and waterfall with one speaker


i want to move back a little with the listener position, but then comes this hole.

[pronto]

i tried all variations of positions the last weeks. i have a tiny desk no furniture...

the only position where the speakers(small or big floorstander) have a good punch is very very close to the frontwall an spread wide out near the corners.

[DanDan]

pronto,
the frequency changes with listener distance. This strongly suggests that your dip is caused by destructive reflection from the side wall, ceiling, floor, or some combination.
It would take some pretty serious bass traps to get at it.
So I suggest that you are right to try moving the speakers to minimise the problem. Since you have already optimised distance from the front and side walls, now play with the height. Sometimes it can be useful to turn the speakers upside down or sideways to get the woofer out of the vertical null.
DD

[pronto]

yes some fine tuning .... i think i will buy some fiberglass packets and try out.