Quick question: Can the wrong placement of panels ....

[MarcB]

Just a quicky

Can the incorrect placement of panels actually make your room sound worse than it would without them ? (I have GIK 244 and 242 panels)

I've been doing frequency sweeps and noticed a huge suckout between 60hz-120hz, it almost goes to no audio at all around 110hz.

I'll post more once I've measured the room (ordered a mic and stand today)

cheers

[jsipich]

Placement matters, yes.

[MarcB]

I understand that placement matters..

but if say for eg. I had a completely undtreated room and then added panels which weren't in the correct places , could it make the room worse at all ?

[Ethan Winer]

Originally Posted by MarcB

could it make the room worse at all ?

Probably not worse, but not as "better" as it should be.

--Ethan

________________
The Acoustic Treatment Experts

[MarcB]

cheers

The reason I asked is I've just re-arranged my room and left the panels due to me not really being bothered to shift them just yet.

thanks

[jhbrandt]

There are many factors at play here.. it could be a null due to comb filtering from early reflections.. OR it could be that you are sitting in a null due to the modal activity of the room. - need more information. please post a drawing with accurate dimensions and your setup placement - please include the height.

Cheers,
John

[Sebastian Vera]

Its seems that there is a hole octave between the deeps, so they are related. It starts very low so it should be an axial mode...

Where did u place the panels? And give us the room dimensions

[Jens Eklund]

Originally Posted by MarcB

Can the incorrect placement of panels actually make your room sound worse than it would without them ?

The amplitude in a specific spot in a room is the complex summation of all phasors (vectors) and it should therefore be possible for two separate ”problems” to cancel each other out, but if one is eliminated, the other will appear.

[jhbrandt]

Originally Posted by Jens Eklund

The amplitude in a specific spot in a room is the complex summation of all phasors (vectors) and it should therefore be possible for two separate ”problems” to cancel each other out, but if one is eliminated, the other will appear.

+1 Well said.

- John

[MarcB]

Originally Posted by Sebastian Vera

Its seems that there is a hole octave between the deeps, so they are related. It starts very low so it should be an axial mode...

Where did u place the panels? And give us the room dimensions

room is 15x13x8ft.

Speakers are firing across the short section (they are large 3 way midfield speakers and sound better away from the sides)

tweeter is 26" from rear wall and 46" from side wall. (other side is 42")

72" between tweeters , 80-85" between tweeters and my ears.

Gik 244 panels at rear corners (I have doorway behind speaker so can't place a panels in the front corners) and at 1st side walls reflection point

gik 242 panels placed directly behind speakers and side walls 2nd reflection point and also placed horizontal higher up near ceiling.

Directly behind, about 18" behind listening position is a large patio door sized window. Having the rear of speakers near the window makes the sound a bit sharp which is why I've tried it the other way.

It's a bank holiday weekend here so the measuring mic and stand still haven't arrived.

Maybe tomorrow or wednesday ?

cheers

edit after playing with some frequency volume tests, there's definitely a large 6-10db boost at 3-3.5khz. any ideas what the cause of that could be ?

[Glenn Kuras]

Once you do get some readings please email them to me so we can take a look. I think it would be easier to talk over the phone to go through a few different things to clear it up.

The amplitude in a specific spot in a room is the complex summation of all phasors (vectors) and it should therefore be possible for two separate ”problems” to cancel each other out, but if one is eliminated, the other will appear

That is what I am thinking also, but also want to walk through his room.

[MarcB]

Originally Posted by Glenn Kuras

Once you do get some readings please email them to me so we can take a look. I think it would be easier to talk over the phone to go through a few different things to clear it up.



That is what I am thinking also, but also want to walk through his room.

I've uploaded some pics (I've posted pics in this forum before so they might look familiar.. please ignore the mess of wires... not worth sorting them out until I've worked out the best placement for everything)

The synth/table is on castors and gets wheeled out of the way when I'm mixing.

ImageShack(TM) slideshow









cheers

[Glenn Kuras]

Would you mind emailing this stuff to me through our company website? Also include your name and contact info. It is kind of hard to keep on top of a thread and GS is not the GIK advise department. lol lol... Trust me it would be great for business but Jules might have a problem with it.

[MarcB]

yeah no probs

I'll do it in a few days once I have the room measured and something to go off.

[DanDan]

There are some global truths regarding room treatment which rarely if ever fall down.
e.g.
Corner placement of traps is very effective.
More Bass Traps is better.

I would regard treating the four vertical corners, floor to ceiling, as a starting point. I would often do this before considering measurement.

So...

And... yes to the question and Jens has explained a reason why. There is more. When say four corners and the RFZ around the mix position are treated there is every chance you will start to hear other problems which were previously masked. e.g. flutter echoes between even small areas.
Central heating radiators ring like bells you will find!

DD

[John White]

Originally Posted by Jens Eklund

The amplitude in a specific spot in a room is the complex summation of all phasors (vectors) and it should therefore
be possible for two separate ”problems” to cancel each other out, but if one is eliminated, the other will appear.

Keeping this in mind, I have found that treating near my speakers
seemed to result in what I thought were new speaker boundary issues.

I wondered if typical 3# RF would have either provided reflectivity issues
or it was that one problem was eliminated and another appeared.

[DanDan]

Many people treat behind speakers as if it were a go-to.
It isn't. RealTraps - Front Wall Absorption

If FW SBIR is your target I can't see those thin panels doing much at LF. If your target frequency is higher due to close proximity to the wall, then there is little energy making it's way back there.

If you don't see a useful change in Frequency Response with those panels behind the speakers, deploy them somewhere useful.

That would be Corners.

DD

[Glenn Kuras]

Originally Posted by DanDan

Many people treat behind speakers as if it were a go-to.
It isn't. RealTraps - Front Wall Absorption

If FW SBIR is your target I can't see those thin panels doing much at LF. If your target frequency is higher due to close proximity to the wall, then there is little energy making it's way back there.

If you don't see a useful change in Frequency Response with those panels behind the speakers, deploy them somewhere useful.

That would be Corners.

DD

Very well said. See more here is SBIR.
Learn what is SBIR (Speaker Boundary Interface Response).

[John White]

Originally Posted by DanDan

If FW SBIR is your target I can't see those thin panels doing much at LF. If your target frequency is higher due to close proximity to the wall, then there is little energy making it's way back there.

I agree as a result of some testing I've done. I'm still wondering, however, if you or anyone else has experienced any negative results toward an existing frequency response as a result of using a substantial porous absorber near their speakers.

For instance, when distributing absorption in my already well treated room, I found certain spots near the speakers to have either a slight benefit, no benefit, or contributing to drastic peaks and nulls (nulls mostly).

I realize that absorption (by definition) theoretically shouldn't create interference. However, the tests did indicate that perhaps some reflectivity from the absorber did attribute towards the creation of new boundary issues.

[Ethan Winer]

Originally Posted by John White

I'm still wondering, however, if you or anyone else has experienced any negative results toward an existing frequency response as a result of using a substantial porous absorber near their speakers.

Yes, I've seen that, but it's very rare. I believe this can happen if a reflection that had been canceling a partial peak or null now becomes trapped, so the response becomes worse. But that just means more traps were needed elsewhere.

--Ethan

[Glenn Kuras]

Originally Posted by Ethan Winer

Yes, I've seen that, but it's very rare. I believe this can happen if a reflection that had been canceling a partial peak or null now becomes trapped, so the response becomes worse. But that just means more traps were needed elsewhere.

--Ethan

Yep that is the first thing I look for.
The fun of acoustics.

[MarcB]

the room...





Not 100% sure if I've done it right, but that's the purdy graphs that it comes up with.

[DAH]

I'd say not bad for an untreated room if these measurements are for the mix spot.

[SörenHjalmarsson]

Originally Posted by John White

For instance, when distributing absorption in my already well treated room, I found certain spots near the speakers to have either a slight benefit, no benefit, or contributing to drastic peaks and nulls (nulls mostly).

I realize that absorption (by definition) theoretically shouldn't create interference. However, the tests did indicate that perhaps some reflectivity from the absorber did attribute towards the creation of new boundary issues.

John,

Theoretically there is actually a bit more to the subject of boundary behavior of waves through different media, aswell as the acoustical impedance of different materials, than the absorption coefficient alone. A given material will not offer absorbtive components exclusevily, nor can it be defined as 'absorbtion by definition' - as pure absorbtion just wont be the case.

Due to the impedance of the material, there will always be a mix of resistance and reactance occuring -- i.e. in all cases a sound wave will undergo both partial transmission (absorbtion) AND reflection. -- and part of the energy, due to certain component properties of the material/new media, will exhibit reactance viz. a resulting acoustic interference.

So, as strange as it might seem... an absorbtive panel, while absorbing certain energy, will also introduce near field reflections - this might very well be what you experienced/measured at certain spots near the speakers.


Cheers,
Sören

[John White]

Originally Posted by SörenHjalmarsson

So, as strange as it might seem... an absorbtive panel, while absorbing certain energy, will also introduce near field reflections - this might very well be what you experienced/measured at certain spots near the speakers.

Thanks for sharing your experience. I'm fairly certain this is what my tests revealed, but wanted some feedback. At one point I also read that "Bass Traps" shouldn't be adjacent (close) to speakers, though I hadn't really understood why. Perhaps there are other factors as well.

[DanDan]

Well stated Soren.
DD

[takman]

Originally Posted by Jens Eklund

The amplitude in a specific spot in a room is the complex summation of all phasors (vectors) and it should therefore be possible for two separate ”problems” to cancel each other out, but if one is
eliminated, the other will appear.

this is why i read every day in this forum...

thanks