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-   -   100 hz dip (https://www.hometheatershack.com/forums/home-audio-acoustics/152977-100-hz-dip.html)

matthijs87 07-15-16 07:33 AM

100 hz dip
 

5 Attachment(s)
Hi guys, i'll introduce myself as most of you dont know me.

My name is Matthijs, 28yo and i'm from the netherlands. (so my writing might nog be perfect :))


Im currently setting up my new room which is meant for professional mixing purposes.

The lengt of my room is 5.65 (Meters)
The width is 3.48 (meters)
The highest point is 2,75 (its not a flat ceiling)

So with this information i made up some calculations where to put my speakers
and where would be my listening position. I had read the listening position should be around 30 till 38 % from your
front wall. So i did.

I placed everything (besides the lengt of course) exact in the middle and have setup the triangle as precice as possible.

My listening position is now at : 2.05 from the front wall which is 36 %

Im giving all this information becouse my graph gave me a big dip around the 100 hz and im being told i should experiment with
moving my listening position and or my speakers position. The only thing im concernt about is how to go about it becouse
every inch would make a big change in the symetry and even possibilities of placement.

So my question is, what would be the best and most effective way to find out where the dip is comming from whitout constantly changing my whole setup just to test if something changed, i mean there should be some guidelines right which makes things easyer ? Isnt there a way to find the source with the information given in the graphs ?

Here are some photo's of my measurements and the room im working in.

As you can see the dip is around 15 db, tho this is probably 5 db to much becouse my spl reading gives 5 db lower when doing the subwoover test.

I tried diffrenct mic placements with symetric angle towards my speaker, and i tried putting a absorb panel in front of my tv just to see if it does something with
reflections or buildups, and i checked to see if it makes a diffrence when i put my refference monitors away. Not big diffrences on all.

bpape 07-15-16 08:17 AM

Re: 100 hz dip
 

First, When you are making changes, all you move is the mic. If you move the speakers and the mic, you have 2 variables and no idea what changes are related to what. You always only want to only change one thing at a time. Also, you appear to have a very high level of smoothing applied which makes it pretty much impossible to determine really where things are. Turn the smoothing off when trying to identify where things are coming from.

matthijs87 07-15-16 08:48 AM

Re: 100 hz dip
 

1 Attachment(s)
Okay, thank you, that makes sense indeed.

I removed the smoothing, and of all tests moving the mic was the one which gave the best results.
i moved it 20 cm towards the speaker which gives me less spikes and is overall a bit better but it doenst look like the source of the problem.

Do you have any sugestions on how to find the source more accurate ?

tonyvdb 07-15-16 08:56 AM

Re: 100 hz dip
 

Just to understand a little more about your speaker setup are you using a small subwoofer?

matthijs87 07-15-16 09:12 AM

Re: 100 hz dip
 

No, im using Genelec 8050s , they produce more then enough sub so i dont need a subwoover :)

tonyvdb 07-15-16 09:17 AM

Re: 100 hz dip
 

Bryan would be the best person to talk to but until he responds Im thinking because you have many reflective surfaces in the room that could be causing cancellation. Have you tried putting down a thick throw rug on part of the floor?

bpape 07-15-16 09:32 AM

Re: 100 hz dip
 

How far are the speakers from the wall you are facing and what position is the mic in for this measurement?

matthijs87 07-15-16 09:58 AM

Re: 100 hz dip
 

Tonyvdb, thank you for your input, i tried the floor on diffrent locations but it didnt make any big changes, some frequenties went a tiny bit better but it also created extra spikes.

@ bpape : from front tweeter to wall is 1 meter (diagonal)
76 cm when measured from the back of the speaker. (diagonal)

Sidewall till tweater is 87 cm by the way.

My mic is pointing up.

lesmor 07-16-16 02:48 AM

Re: 100 hz dip
 

Quote:

matthijs87 wrote: (Post 1475425)
Tonyvdb, thank you for your input, i tried the floor on diffrent locations but it didnt make any big changes, some frequenties went a tiny bit better but it also created extra spikes.

@ bpape : from front tweeter to wall is 1 meter (diagonal)
76 cm when measured from the back of the speaker. (diagonal)

Sidewall till tweater is 87 cm by the way.

My mic is pointing up.

I hazard a guess that going by 87cm that it could be a sidewall 1/4 wavelength cancellation?
Caveat being I am no expert and just trying to learn

matthijs87 07-17-16 04:20 PM

Re: 100 hz dip
 

How is that a 1/4 wavelength cancellation ? woudnt 1/4th be 25 cm ? or maybe im missing the point , but from what i have read is that the sidewall length shoudnt be an equivalent of the length from the wall behind the speaker. so if im right, that would mean cancelations would be most probably at 25, 50 75 in my case or maybe i didnt understand this part well enough, im curious as well :)


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