Comb Filtering is evil

[Scoobz]

Direct from Satan's butt!

If you think speaker placement isn't important read this......

Ok, I've struggled with my setup for what feels like an eternity and made various posts on here (in which many of you were kind enough to try and assist me with) trying to sort out the treatment in my room.

My speakers started off on the bridge, sounded bad so got some stands, not much better, I made small desk stands so I had more flexibilty in monitor placement but no where seemed to gain an improvement. The top end was always 'off' and I had major problems with 100hz and 400hz.

My dimensions are not great 4.5mx5mx2m, due to the height I made a different cloud (didn't make much difference) I was close to giving up, even tracks made in top studios sounded awful in my room.

Then someone suggested I try to get my speakers higher up (this from a layperson btw) So I put my desk stands ontop of my proper stands and moved the speakers up and out about a foot and a half (and angled them down of course).

OH MY GOD! No comb filtering, I knew it straight away as soon as I played the first track. TFFT

Now I've found the solution I realize what my problems were. When on the desk the speakers were so close to the surface of the desk the angle meant I was getting really bad comb filtering and I was probably getting some serious sonic rebound off the desk causing odd vertical nulls. When on the stands the drivers were within say 15cm of vertical centre and the angle was still shallow.

Now they're up and out they sit maybe a third down from the ceiling (0.7m), close enough to the front wall to get a little sbir reinforcement, the angle of incidence is much more acute and is treated by a square of foam on the desk.

Anyway, I thought I take you on a little journey down my speaker setup history, my findings and my interpretation of the possible causes. I'd like to hear any thoughts you may have or any additional theories.

Nice to have a bit of good news for a change aint it?

[ProTools4]

I can dig it

[Scoobz]

thanks man, at least someone does!

I woulda liked a bit of feedback from those in the know. Do my theories make sense?

[Weasel9992]

Originally Posted by Scoobz

thanks man, at least someone does!

I woulda liked a bit of feedback from those in the know. Do my theories make sense?

Sure. What you're describing is an utterly common problem.

Frank

[pooley_99]

Hey there Scoobz,

I am near completion of my room build. Before my desk arrived I stuck a little table in with my laptop and baby monitors to see what was happening. It all sounded great... at first.. then I got my bigger mointors and turned it up.. oh dear!! I noticed (very subtly at first) when I moved backwards on my chair this weird flange effect like comb filtering, and would go all teh way up in frequency till I got to the back of the room, then when moved forward it would come back down again and stop (in flangy effect) where you would be sitting, but then you would notice this false frequency just sitting over your nice mix...and you really hear it then! I havent tackled the problem yet because the desk wasnt in then (52 module DDA) which will obviously change the characteristics of the room as its so big. So now the NS10s are in place on the meter bridge and I am boiut to see if the change in height/position/room layout has sorted it out??? One other factor is two big windows either side of the desk!!! Might have to block the buggers up, after all my hard work of getting them in in the first place and angling them blah blah... I was very stubborn about keeping natural daylight in tho.. nothing worse than working in a dungeon.. Anyway I'll let you know how it goes..

[Scoobz]

Well it's good you can hear the comb filtering, be interested to hear your findings. Up and out worked for me and of course angling down, good luck and keep us posted!

Frank, I've spent a long time learning about acoustics trying to solve my studio issues, piling more insulation in the room, trying membranes etc. I now realize was chasing the wrong problem. I think the 'high speakers pointing down' idea should make it into the set of 'rules' You know, the 38%, symmetrical, equilateral triangle set of rules. Woulda saved me alot of time

[DanDan]

Hi Scoobz, interesting post. Comb filtering seems to be most troublesome at high frequencies. A mirror will usually identify a destructive secondary path from tweet to ear.
However HF doesn't start at some exact frequency. So your trick probably helps eliminate some bounce effects lower down into the spectrum.
Also, the change of position of the woofers stimulates the vertical modes differently, perhaps better in your case. Fuzzmeasure or other would show this.
Lastly a caveat. I would not go too far with this. The ear is somewhat directional in terms of height. With eyes closed we can pretty much identify where sound is coming from height wise. This appears to be mostly due to change in frequency response with height due to the shape of the ears.

DD

[Scoobz]

thanks for the post dan, interesting reading. I think the angle (that the speakers point down) is around 15 degrees so it's not too seviere. I've also seen mains in 'proper' studios soffit mounted and angled down. Interesting point about the shape of the ears.

Cheers

[mikethedrummer]

pics or gtfo =p
id love to try a similar placement

[Scoobz]

lmao

http://i27.tinypic.com/23sw6m9.jpg

how's that for alot of treatment?! I've even got superchunks behind those corner traps!! The bass is nice and tight though

by the way there's a prize for guessing all the synths pictured (not really but there's a few I wouldn't be sure about from that pic) Oh and can you spot the dodgy joins in the picture? :D

[12ax7]

I'm setting up my studio again (after a year of having my gear in storage).

Anybody had any experience with dead-hanging nearfields from the ceiling at an optimum location?

[mikethedrummer]

that room is sweet. im surprised you even had noticeable phase issues

[Scoobz]

thanks mike, it was a combination of factors. Having the speakers at ear height meant they were quite close to the centre vertically, moving them up killed several birds with one stone so to speak