# Advice on treating early reflections



## Doctor X (Apr 3, 2007)

Hi there,

I recently bought acoustic treatment from GIK (4 tri-traps and 3 244 panels) and the differences the tri-traps made was night and day in the low-end. However putting two 244 panels behind my main speakers made them sound much, much better.

Everything I put on the system, whether it's music or movies sounds much clearer with better separation. Turning the volume up now makes things sound better, with less clutter. But I still feel it could sound better at higher volumes.

As good as the bass sounds now, there are some occasions at higher levels where bass instruments tend to give this 'booing' effect on music. The ringing and boom has been reduced significantly, especially higher up after treatment was put in, but it hasn't been mitigated at higher levels. I suppose the higher the volume, the more these artifacts will creep in, whether it be some kind of resonance or ringing.

Here are just a couple of pics to show the layout of the room. I've been chatting with Bryan via PM and I think these pics might give him a better idea of what is happening. I would like fellow members who have treated their rooms to tell me what made the biggest difference to them as far as placement of their panels is concerned. 

Did you find the sound improved significantly when putting panels on the side wall reflection points ? Behind the speakers ? On the back wall ? Ceiling ? Any observations would be appreciated.

Forgive me for the low quality pics, they were taken on a very old camera :










The front of the room, tri-traps stacked from floor to ceiling in the two front corners. I don't have the 244 panels positioned behind the front speakers. There is a cabinet in the way so it makes things look awfully untidy if I straddle the traps behind the speakers. But it works wonders when I do ! 










As you can see from this pic, I can't put any panels in between the speakers and where I'm sitting as the wall opens to a kitchen on the left side. However I have tried putting a 244 panel directly to the side of me, where you see the big mirror. I elevated the height of the panel by using a small stand. Made no difference to me.










You can see on the right side below the surround speaker, empty wall space. I tried putting a 244 there but it made little to no difference at all.










I've tried putting two 244 panels on two chairs as a temporary solution and, again, it made little to no difference. I don't know if they should be raised more but I pretty much put them up at slightly above ear level height as far back against the wall behind me as possible. The door behind the chairs is always open as you see it. 

Bryan, perhaps you can see where I'm going wrong or offer your advice as to what I can do to mitigate these reflections that otherwise cause this acoustic 'clutter'. After putting in the tri-traps and the two 244 panels behind the speakers, I've noticed that my room isn't nearly as harsh as it was before. But I don't want it to sound too dead and I'm scared of making it sound lifeless if I add more panels. What are my options ? 

Regards,


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## cinema mad (Jan 28, 2007)

Hi Vaughan,

Is there any chance you can move your subwoofer out and away from the corner, mabe along A side wall?..
This will definitely help with reducing boomy bass due to corner loading...

Cheers...


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## lcaillo (May 2, 2006)

Start by moving the speakers out from the cabinet and TV as far as possible. Most of your problem with reflections are likely there.


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## Doctor X (Apr 3, 2007)

cinema mad said:


> Is there any chance you can move your subwoofer out and away from the corner, mabe along A side wall?..


The sub is about 1/2 meter away from the corner boundary. I could try moving it out a little more out so that it's further away. As for the side-wall suggestion, I think I should start dreaming.  I'm getting enough grief as it is. Heh. 

Thanks !

Regards,


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## Doctor X (Apr 3, 2007)

lcaillolcaillo said:


> Start by moving the speakers out from the cabinet and TV as far as possible. Most of your problem with reflections are likely there.Start by moving the speakers out from the cabinet and TV as far as possible. Most of your problem with reflections are likely there.


Thanks for the suggestion but when I place the panels behind the speakers, they're already more than 1m away from the cabinet. I would have assumed that would be sufficient distance away from the wall.

I won't be able to move them further than that. Thanks for the suggestion !

Regards,


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## bpape (Sep 14, 2006)

In your particular situation, the panels behind the speakers are not only dealing with SBIR and surround reflections from the rears, they're also helping to control the resonances being built up in the cavities of the entertainment center/shelving. 

Each of those cavities has it's own resonance that can mask detail, cause a bloated midbass throgh lower mids, etc.

Bryan


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## Doctor X (Apr 3, 2007)

Hi Bryan,

So, besides placing the panels behind the speakers, where else could I possibly put panels to reduce SBIR and resonances/ringing ?

Regards,


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## bpape (Sep 14, 2006)

SBIR is purely a function of behind and directly beside the speakers. You dont' really have an option for side wall reflections with an opening on 1 side and windows/curtains on the other.

The rear wall directly on each side of the open door will give a bit of bass control in the rear of the room and help a bit with general decay time. 

With the hard floor, some panels on the ceiling would be a benefit in general decay time control but not sure if that's an option. You just don't have a lot of other places to work with.

Bryan


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## Doctor X (Apr 3, 2007)

Thanks for your comments Bryan ! I think I'll try perhaps a pair of Monster traps for behind me on the wall and a custom 244 for the center speaker. I'm sure the Monster traps would make more of a difference than the 244's would, especially behind me with respect to decay times and dealing with possible resonances.

The big white cabinet is going to be sold soon as well so I can then put a custom 244 trap behind the center speaker. As far as the side wall reflection, that is the only thing which disappoints me because I'm told that it will give greater focus and even cleaner more detailed sound but I can't do anything about it.

Thing is, since the kitchen opening is almost right where the left front speaker is, would there have been any real benefit for an absorption panel there in the first place ? If one panel was put besides the right front speaker, covering the windows, do you think that would have made much difference ?

Regards,


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## bpape (Sep 14, 2006)

You can potentially do a panel on the right side. That will reach more into the dialog range than just the curtains. The other side with the kitchen, there's nothing to reflection off of - other than very late ones bouncing in the kitchen and then back out.


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## Doctor X (Apr 3, 2007)

Cool. Thanks again for your help. I'll email for a quote on the Monsters and custom 244.

Thanks. And sorry for being such a nuisance. 

Regards,


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## omholt (Jun 5, 2007)

I would do the following:

1. Get rid of that cabinet and replace it with a small TV rack. Yes, it's about time to get serious with the sound. :bigsmile: Then you can place two 244s in the first reflection points on the front wall. 

2. Place two bass traps (244s or Monster Traps) on the rear wall.

3. Buy three 242s. Two of them you can place on the first reflections on the ceiling. The third one you can either place between the two on the ceiling or on the one sidewall as Bryan mentioned.

Remember that 242 are a different product then 244s and Monsters. The 242s absorp all the way up.


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## Doctor X (Apr 3, 2007)

I was thinking of getting either 2 more Monster traps or another pair of 244's. My reasoning is that those traps reach down deeper than the 242's and I need as much bass trapping as I can afford, right ? Bass issues are hardest to control and if I can use the 244 or Monster then I think I should go for maximum absorption down low.

Because I'm thinking that by the time I've added those traps, the high-end would have _at least_ been tamed enough. If I add a bunch of 242's they might absorb too much in the high-end. At least, I'm assuming that might happen. Perhaps Bryan or anyone can explain why 242's would be beneficial over the 244's or Monster traps besides being less expensive. 

Regards,


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## omholt (Jun 5, 2007)

Well, you don't have any panels that absorb the high freq and 100% of the midrange today. You really need both. I agree though that you shouldn't use too many of panels that absorb all the way up. But again, you don't have any in first reflection points today and you need some. Tri-traps absorb all the way, but they are placed in the corners. 244s are a membrane panels that mostly reflect the high freq. I would use 242s on the ceiling, first reflection points. That may be enough, and then you can use 244s, Tri-traps and Monsters other places. Bass trapping in very important in a small room, but some absorption of highs is also needed and vital.


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## Doctor X (Apr 3, 2007)

Thanks for the reply, omholt. Doesn't the 244 and Monster traps absorb sound at the high-end too, just not as much as the 242's ?

If I put 242's at the first reflection points vs 244 panels, wouldn't the 244's absorb a similar amount into the mid-range but also more bass control up in the higher bass (like from 100 Hz up to 500 hz ? ) I'm not against the idea of getting 242's, I'm just trying to understand how it would benefit my situation.

I mean, if one just had 244's in the first reflection points, in the corners, on the back wall, etc, would that not be enough ? Just asking. Thanks again for replies.

Regards,


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## bpape (Sep 14, 2006)

Correct. The 244 and Monster don't just brick wall at say 500 Hz. They roll off gradually. Even at 4k, they're still about 25% absorbent.

That said, 242's are generally preferred for side wall reflection duties.

Bryan


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## Doctor X (Apr 3, 2007)

Bryan, what would I expect by adding 242's to the room ? Like if I put them up at the ceiling reflection points ? What would change ?

Focus ? Reducing the level of confusion within the sound at higher levels ? I don't have any idea. I don't know what problems are caused at very high frequencies so I don't know what to look out for (besides echoes and there aren't echoes per se in my room, but I can tell that when clapping my hands, the sound doesn't die out immediately..)

I want my system to be used for music and home theater.

Regards,


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## Doctor X (Apr 3, 2007)

It is preferable for high-end absorption to be placed on the ceiling or would it rather be recommended to use a trap that has good bass absorption ?

Regards,


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## bpape (Sep 14, 2006)

242's on the ceiling will give some better focus and screen lock as well as providing good general decay time control. At reflection points, 242's would be preferable. 244's would be better if directly over the seating to deal with any height related bass response issues.

Bryan


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## Doctor X (Apr 3, 2007)

Wouldnt the back wall reflection point need the most absorption in the low end as possible ? Do your 242 panels have no membrane installed ? Just wondering, because if they absorb basically all high frequency reflections then I would imagine no membrane could be used othrewise higher frequencies might be reflected back into the room. 

So you're saying that 242's are better than 244's for reflection points like behind the speakers, side walls, back wall and ceiling ? 

Regards,


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## bpape (Sep 14, 2006)

Back wall, yes on needing extended bottom end control (244's). Side walls, no. The wall behind the speakers can be either depending on the amount and frequency where your SBIR starts.

Bryan


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## Doctor X (Apr 3, 2007)

How does one determine what frequency the SBIR starts at ? Sorry for asking all these questions. If I put up 244's that may be enough but it may not and I won't even know if it's not as I don't know what to look out for.

Regards,


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## Doctor X (Apr 3, 2007)

If I'm understanding you correctly, the 242's _really_ need to be used on the side-walls, but the 244's can be used behind the speakers and even more bass control would be welcomed using either 244 or Monster traps for the rear wall. The ceiling should also 242's and not 244's.

Regards,


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## Kal Rubinson (Aug 3, 2006)

Vaughan100 said:


> How does one determine what frequency the SBIR starts at ? Sorry for asking all these questions. If I put up 244's that may be enough but it may not and I won't even know if it's not as I don't know what to look out for.
> 
> Regards,


IIRC, it is worst where speaker-boundary distance is 1/4 wavelength resulting in cancellation.


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## Doctor X (Apr 3, 2007)

Thanks Kal. So if my dimensions from back to front wall is like 5.5 meters (I've got a rectangular room but am sitting the short way) then how would I calculate what frequencies would be affected ? Speed of sound divided by distance ?

I know that sitting the long way would be best as the walls are spaced much further apart but unfortunately I can't change my current position.


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## omholt (Jun 5, 2007)

Vaughan100:
Do you know what the first reflection is how to find them? 
It's the mirror image of the speakers on the walls, floor and ceiling. 242s placed in first reflection points on sidewalls would be beneficial, but are not possible in your room. You can however place 242s on the 1reflection points on the ceiling. Yes, 242s are a better option there then 244s because it's good to have some absorption of the reflection points that absorps 100% of the higher frequencies. It gives better image and pin-pointing, more overall direct sound from speakers. 

On the rear wall, you're probably better off using 244s or Monsters.
I hope that clarifies it.


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## Doctor X (Apr 3, 2007)

Yes, thanks for clarifying omholt. I appreciate it. Just as a matter of interest, I've got some Ready acoustic suede bags and if I put 4" fiberglass in them, would that not absorb all the way up since there is no membrane installed ? 

Just thinking that I've got some of the bags, I just need some fiberglass then not only would it absorb all the high's but it will also dig deep. Am I correct in thinking this ?

Regards,


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## bpape (Sep 14, 2006)

Look at your response plots. Then take another measurement with them pulled out say 6-8". What changes is boundary related.

Bryan


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## Doctor X (Apr 3, 2007)

Bryan, why don't the 242's have absorption data on the website ? It says that it has equal absorption from 250-4000 Hz. But it doesn't show absorption numbers above that.

Also, would a 4 inch thick panel of fiberglass (with no membrane) be as effective in the high-end as a 1 inch thick panel ? Thanks.

Regards,


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## bpape (Sep 14, 2006)

Not sure why. Thought it was there. Above 4kHz, you can't get official lab results - just like you can't get them below 125hz.

The 242 does have a membrane going on but it's not totally blocking. The 242 is 2" of absorption with 1.5" air gap. It'll do the same all the way up pretty much. Below 250, it gradually rolls off.


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## Doctor X (Apr 3, 2007)

Okay. I was just wondering because I've got the bags so all I need is some fiberglass. The bags can fill up to 4" of fiberglass so as long as it absorbs all the way up, which is what I'm told is the optimal thing for the reflection points, then that sounds like a plan. As a bonus I'll get some additional low-end absorption.

Unless there is a distinct advantage going for the 242's that I'm not aware of ? I just want to make sure my room is balanced. 

Regards,


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## bpape (Sep 14, 2006)

4" of fiberglass in that application will be fine.

Bryan


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## Doctor X (Apr 3, 2007)

Bryan, I just want to say thank you very much for the time taken to answer my queries. I really appreciate your guidance in these matters. To everyone that helped, thank you very much ! I've learned some important things that will help me in future. One thing I know is that I really want those Monster traps. Because although the Ready Acoustic bags are, well, 'ready made' and all, I highly doubt they will have the fit and finish of a GIK product. If I decide to buy more panels it will be from GIK as their service has been excellent and the products first-rate.

I've been very happy so far.

Again, thank you.

Regards,


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## Kal Rubinson (Aug 3, 2006)

Vaughan100 said:


> Thanks Kal. So if my dimensions from back to front wall is like 5.5 meters (I've got a rectangular room but am sitting the short way) then how would I calculate what frequencies would be affected ? Speed of sound divided by distance ?
> 
> I know that sitting the long way would be best as the walls are spaced much further apart but unfortunately I can't change my current position.


What are your *speaker*-to-boundary distances?


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## Doctor X (Apr 3, 2007)

Hi Kal,

My main speakers are positioned half a meter away from the front wall. I am sitting almost 3 meters away from the speakers. The rear wall is about 1.5 m away from my seat.

Regards,


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## Kal Rubinson (Aug 3, 2006)

Vaughan100 said:


> Hi Kal,
> 
> My main speakers are positioned half a meter away from the front wall. I am sitting almost 3 meters away from the speakers. The rear wall is about 1.5 m away from my seat.
> 
> Regards,


1/2 meter is 1/4 wavelength for about 175Hz. Figure on interactions from their down.

But what are the distances from the same speaker to the other boundaries (side wall, ceiling, floor)?


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## Doctor X (Apr 3, 2007)

Well there is no side wall where the left speaker is positioned. It basically opens to a kitchen area. The right main speaker is situated about 1.5 m away from windows directly to the sides. No wall, just a large section of windows. 

The ceiling is exactly 3 m high.

Regards,


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## bpape (Sep 14, 2006)

And that's part of the problem. Left and right wall are completely different.

Bryan


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## Doctor X (Apr 3, 2007)

So symmetry is very important ?

Regards,


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## bpape (Sep 14, 2006)

Absolutely. Differences in boundary makeup and distance can change bass response, reflection timing, imaging, etc.

Bryan


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## Doctor X (Apr 3, 2007)

Just wondering, I can get fiberglass locally, but I'm not sure if it's the equivalent of 703 or 705.

http://www.isover.co.za/content.asp?subID=13

You can get them in different densities. I want to use 6" fiberglass to make 2 traps and use the Ready bags for behind the couch. The way I see it, I'll treat the entire spectrum as well as digging deep for bass absorption. Just not sure if the fiberglass shown is the right type.

Regards,


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## bpape (Sep 14, 2006)

The Glasswool will be very similar. For reflections, make sure you get unfaced. The 40-50kg will be similar to 703 IIRC.

Bryan


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## Doctor X (Apr 3, 2007)

Would you say there isn't much benefit going for 705 ? There is like a R30 difference between the less dense stuff (48kg) and the 96kg, which I assume would be the equivalent of 705 ?

For bass trapping on a wall, not in corners, would 703 be perfectly sufficient do you think or am I better off getting the more dense fiberglass ? Thanks.

Regards,


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## bpape (Sep 14, 2006)

No benefit on wall reflections. Also, once you get to 4" or thicker, there's very little difference. Let's just say you can get 6" of 703 for less money than 4" of 705 and the 6" will perform WAY better down low.

Bryan


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## Doctor X (Apr 3, 2007)

Thanks for the advice !

Regards,


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## Doctor X (Apr 3, 2007)

Just for kicks, I put up 2 244's panels in the lower right corner, stacking the panels staddling the corner. I didn't notice any big differences but then I'm not able to play anything loud to see if there is a difference.

I'm sure it must be doing something.

Regards,


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## Doctor X (Apr 3, 2007)

So I'm wondering now what I would need to do in order to get much more of an improvement in terms of ringing. Because stacking 244's didn't seem to make much of a difference. It probably did reduce the ringing, but it didn't reduce it in a way that 4 tri-traps did, obviously. So what do I do to get another '' moment from here ?  

I had a spare 244 and being the lazy fellow I am, just got my camera and took the shot. Heh.

Regards,


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## Doctor X (Apr 3, 2007)

Currently, I have *no* panels behind me and I have *no* panels behind the speakers since I've taken 3 244's and used 2 of them for stacking in the lower right corner. I somehow have a feeling that two Monster traps stacked in my current situation would have yielded much better results than the 244's. But I need to have a reality check, those panels aren't staying where they are. It's late now, so I just decided to move them there as an experiment.

Regards,


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## omholt (Jun 5, 2007)

Try to place the 244s on the rear wall behind your couch and report back.


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## Doctor X (Apr 3, 2007)

Good morning )),

I tried that. The first time I tried it and noticed very little to no difference the panels were on the floor, at an angle against the wall. I've realized that panel positioning is very important to (especially the height of the panel). I tried raising the panels up on two small chairs and now it definitely has made a difference. It sounded more focused and the ringing also was reduced a tad, which was a nice bonus.

What is the next major improvement that I'll get besides adding some high frequency absorption (which I'm told will make things even more clear sounding ? ) Using 6" panels straddling the lower right corner stacked ? Treating the ceiling reflections ? The wall-ceiling corners ?

Admittedly, my options are very limited but I would like to know where to go, hypothetically speaking. I know I'll make the two 6" traps, which I'll either use for behind me (where I temporarily put the GIK 244's, or I can put the two 6" traps behind the main speakers (if additional high frequency absorption is needed at the front wall reflection points).

Regards,


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