41 replies to this topic

[Grainy]

Whilst doing a bit of reading about room treatments, I found a conversation on the Audiogon forums which included the following thoughts by Steve N. of Empirical Audio in dealing with big flat panel TV's between your speakers:

....you might consider adding some 1/4 round ASC tubetraps near the rear insides of the speakers. Face the round surface inwards. These then can be "tuned" by moving them forward and backward along the inner line of the speaker walls. You can also rotate them slightly outwards to improve width of soundstage. These tubetraps in this configuration are not being used for bass, then are reflective in order to scatter unwanted backwave.

....The reason for the 1/4 round tubetraps is to eliminate the effects of a HD screen or in your case, the cabinet. You will have improved imaging, depth and width. I personally have a combo HT and 2-chnl system. The only reason I can do this is the 1/4 round ASC traps and their specific positioning....the traps should be 1.5-2" behind the inner back edge of the speakers. Start with the backside of the trap being parallel to and along the inside edge of the speakers. Then rotate them outward a few degrees at a time until the centered vocalist becomes diffuse. Then rotate back. Then you will have the best mix of image focus, depth and width. Move them closer to the speakers or further away to get the best overall focus.

Anyway, call me simple, perhaps stupid, but I'm trying to get my head around the setup he's explaining, this is my interpretation in the Pic. Have I got it right?

Any thoughts, and any idea where I could get 1/4" bass tubes, or something else that would diffuse in a similar way so I can give it a go?

[Peter the Greek]

Unfortunately you cant get the ASC traps here - not at a decent price at any rate (you'd have to buy them direct from the states I believe).

My stance with front walls remains unchanged - cover in a minimum of 50mm of high density insulation (I'd do a few other things, but basically as much absorption as you can get).

I suspect the benefits in " image focus, depth and width" are from him moving the speakers intoa more beneficial locaion and possibly experiencing come benefits of absorption from the face of the traps.

I've not seen anything that says adding diffusion to a front wall is a good thing unless dipole speakers are being used (which I know nothing about so wont comment)

[aechmea]

Like Elill I don't think that tube traps are available here. prohibitively expensive to import. I am trying to make my own from pre-formed fibreglass tube, but still a work in progress.

They aren't 1/4inch tube traps but 1/4 round. More likely to be 12 inches or so in dimension.

I think that he means that the traps are situated the other way around as in my crudely updated picture. Your missus looks more comfortable now as well

[Some planar owners like diffusion behind (more common), others absorption (less common). I use absorption because I prefer a heavier/richer sound and am happy to absorb highs whilst 'fixing' the bass. My front wall is almost all covered with high density fglass like Elill.]

Attached Files

•  From Clipboard.jpg   24.69KB   23 downloads

[Braddles 63]

Here is a tip for the flat screen. If you are doing some critical listening and not watching tv, hang a rug over the tv.

[KenTripp]

Moving the speakers further into the room will help negate the effects of that flat hard surface between them.

As will wall mounting the panel.

I'm assuming WAF is in play here as TubeTraps look nice but there are lots of other ways to improve this situation.

[O.Sydney]

Moving the speakers further into the room will help negate the effects of that flat hard surface between them.

or moving the flat panel TV further back in relation to the speakers

[triode12]

Grainy is not a bad looking chick...

[Krispy Audio]

Grainy is the Higgs Bacon, defying gravity in the first pic

[GregWormald]

Whilst doing a bit of reading about room treatments, I found a conversation on the Audiogon forums which included the following thoughts by Steve N. of Empirical Audio in dealing with big flat panel TV's between your speakers:

....you might consider adding some 1/4 round ASC tubetraps near the rear insides of the speakers. Face the round surface inwards. These then can be "tuned" by moving them forward and backward along the inner line of the speaker walls. You can also rotate them slightly outwards to improve width of soundstage. These tubetraps in this configuration are not being used for bass, then are reflective in order to scatter unwanted backwave.

....The reason for the 1/4 round tubetraps is to eliminate the effects of a HD screen or in your case, the cabinet. You will have improved imaging, depth and width. I personally have a combo HT and 2-chnl system. The only reason I can do this is the 1/4 round ASC traps and their specific positioning....the traps should be 1.5-2" behind the inner back edge of the speakers. Start with the backside of the trap being parallel to and along the inside edge of the speakers. Then rotate them outward a few degrees at a time until the centered vocalist becomes diffuse. Then rotate back. Then you will have the best mix of image focus, depth and width. Move them closer to the speakers or further away to get the best overall focus.

Anyway, call me simple, perhaps stupid, but I'm trying to get my head around the setup he's explaining, this is my interpretation in the Pic. Have I got it right?

Any thoughts, and any idea where I could get 1/4" bass tubes, or something else that would diffuse in a similar way so I can give it a go?

From my reading the front of the speaker would be in line with the cabinet or screen with the traps between the speakers and the cabinet. I.e.--move the speakers back so they are 'outside' the traps.

I think the way the pic is now, with the speakers well forward, the confusion from the cabinet/screen bounce would most likely be much less.

As Braddles indicated, anything that softens the hard edges and surfaces of whatever is between the speakers, should work to some extent. The article is basically recommending that you reflect/diffuse some of the sound waves between the speakers in a regular way rather than with irregular hard surfaces.

Greg
(all of the above is gained from experience--I have no training in acoustics!)

[Grainy]

Thanks for the pointers folks, sounds like my first point of call is to bring the speakers out more, which I can and do when the need arises, and get some asthetically pleasing absorbsion on the front wall. I was hoping the tubetraps would be a nice convenient answer, pity they are'nt more readily available. Is there such a thing as sound absorbent wallpaper ?????

Yes you're right Aechmea, I meant to say 1/4 round, not inch. BTW, you now have my missus facing away from the TV, shes not gonna like that.

[berun12]

Why not put a portable absorption or diffusion horizontally right in front of tv panel for critical listening? You could store it behind tv cabinet for other times. 4 cm thick, dense polyester like Polymax will do the job perfectly. Problem of first reflection from from that tv solved.

On side walls put again either absorption or diffusion in the first reflection points.

Put basstraps in the corners, that's where they do the most work. No point wasting them in away from the wall.

Thanks, berk

[loki65]

This is how i resolved my issue. 1800mm x 1200mm x 12mm chipboard, framed with 40mm x 20mm pine and some accoustic foam. Just need to get some castor wheels, so i don't have to carry it.

[Grainy]

Cool idea loki. I'll start off with throwing some blankets around and give it a test. Its the constant tussle between sound improvements and WAF

BTW, anyone have experience with Acoustice Art panels like this?

www.acousticart.com.au

http://www.artoustic.com.au/

I don't mind paying a bit for something pretty

[O.Sydney]

you could make one yourself that looks pretty good in a modern decor.
Acoustic pyramid tiles in your choice of colour, acoustic compressed panel as a substrate. It can also be made double thickness.

like this

[KenTripp]

That's very neat. This is what my 55" Sony looks like in audio only mode...

[loki65]

Cool idea loki. I'll start off with throwing some blankets around and give it a test. Its the constant tussle between sound improvements and WAF

BTW, anyone have experience with Acoustice Art panels like this?

www.acousticart.com.au

http://www.artoustic.com.au/

I don't mind paying a bit for something pretty

Cheers mate, thats how i started. The box the TV came in with a couple of dooners over it, and pillows taped to the walls.

I also looked at the pre made panels, pretty pricey. For a hell of a lot less, i made that one got bass traps and a few smaller panels for the walls. I have not bothered about it yet. But if you got a staple gun and some material, i don't think it would be to hard or expensive to cover them. And i think you could get away with doing the room (within reason), for less than the price of some of the panels ive looked at (ie - 2400 x 1200 $1390).

[Peter the Greek]

Cool idea loki. I'll start off with throwing some blankets around and give it a test. Its the constant tussle between sound improvements and WAF

BTW, anyone have experience with Acoustice Art panels like this?

www.acousticart.com.au

http://www.artoustic.com.au/

I don't mind paying a bit for something pretty

I can make you custom printed absorber panels. PM me if interested.


I'm also working on a "abfuser" (absorbs and diffuses) panel but this is a little way off.

[Grainy]

OK so I'm a fool. I knew about the "cover the TV" mod but never tried it, even though I have 59 inches of smeary-ness between the speakers. Yes it make a noticable difference Now I need to make something up that looks better than a baby blue faux wool blanket.

I'm now using my tablet to control iRiver instead of the remote and TV when doing serious listening (Nada may like to know).

Thanks for the offer Ellil, the problem wall area would be better covered by a custom size, tall and thin. My wife is a graphic designer and would love to create the image to print on it. I'll PM you in the near future if thats OK.

Edited by Grainy, 17 July 2012 - 07:25 PM.

[Juicester]

you could make one yourself that looks pretty good in a modern decor.
Acoustic pyramid tiles in your choice of colour, acoustic compressed panel as a substrate. It can also be made double thickness.

like this

how is that connected to the TV? I like this solution and would love to copy it....

[O.Sydney]

it's free a standing unit, when not in front of tv it's on the floor at first reflection point on side wall (not that the first reflection point concerns me too much)

[b.d]

I reckon diffusion between the speakers or anywhere is ideal and always better than a tv or a flat wall, but I dont think a TV is worse than a flat wall, probably better in that is breaks up the uniformity of whole wall as a reflective surface. I cant imagine glass is any worse than smooth concrete as a few micrometers of paint texture is going to do not very much at all. If the TV was further forward it would shorten the soundstage, but having it pretty close to wall is nothing worth worrying about.

I also reckon that a blanket over the TV is often worse than no blanket as it only absorbs the very highest frequencies and can tend to over deaden the sound. Either absorb the majority of sound with thick foam absorber over the TV, or nothing at all.

[flemo]

If the TV was further forward it would shorten the soundstage, but having it pretty close to wall is nothing worth worrying about.

I also reckon that a blanket over the TV is often worse than no blanket as it only absorbs the very highest frequencies and can tend to over deaden the sound. Either absorb the majority of sound with thick foam absorber over the TV, or nothing at all.

I'd have to disagree with that Bevan. The glass panel between my speakers causes very noticeable smearing. When I use a thick doona to cover the TV and it cleans up the imaging quite significantly. I thought it was a load of crap until Mario and Tuyen came over and complained about the smearing and insisted I try covering it. When I covered the panel I was gobsmacked at the significant improvement.

This has since made me determined to reclaim the games room from the kids in the near future so it can be a dedicated music room with no TV or HT!!

Cheers, Pete.

[b.d]

Hi Pete. Have you compared your uncovered tv up against the wall vs just the bare wall out of interest?

I'm not surprised a a thick doona can improve things without doing much harm, I was more thinking of those free airline type blankets. Though even these will only improve imaging, just likely at the expense tonal balance.

Cheers
B

[flemo]

Hi Pete. Have you compared your uncovered tv up against the wall vs just the bare wall out of interest?

Hi Bevan, no mate I haven't compared the bare wall vs the TV.

Pete.

[kajak12]

Hi Pete. Have you compared your uncovered tv up against the wall vs just the bare wall out of interest?

I'm not surprised a a thick doona can improve things without doing much harm, I was more thinking of those free airline type blankets. Though even these will only improve imaging, just likely at the expense tonal balance.

Cheers
B

Tonal balance is just fine with a blanket on a tv on a tuned system imho

[Grainy]

So I got off my butt and bought some convoluted foam, glued some cardboard on the back for support, and wha-la - temporary acoustic treatments.

[O.Sydney]

Hey that's quite a visual feature, has it made much difference to the sound ?

Why temporary, you got more plans ?

[Grainy]

I say temporary 'cos I can move the in and out as required. The sound is somewhat better focused in the midle areas, but I think it has also recessed the soundstage a bit, stops dead at the edge of the speakers when in place. As you say, it's all an experiment.

[O.Sydney]

that it is !! although lately no experiments and just enjoying the music.

I nice aluminium frame mitre cut corners to dress it up further and it could become a permanent feature.
After my experiment with such product in that position I found it worked really well in the room opposite the speakers to stop a bit of the bounce back into the room.

Experimenting is a slippery slope and before ya know it you can't stop the beats

[DRC]

This thread has given me some inspiration. The listening area is, well, an open plan dining/lounge area so the WAF is pretty low in terms of getting room treatments. The room also really needs them. Bugger.

As The Chef keeps different hours to me, I thought it could work if the room treatments were easily portable and could be stored in the spare room when not in use.

Project 1 - Flat Panel Treatment
Disused picture frame in the shed (no glass). Cut 4 cm thick acoustic foam to frame size, then hot melt glue to the frame. Visit Spotlight and get hold of a few meters of light weight fabric in the clearance bin. Cut fabric to size and staple gun to the frame. WAF is quite high.

 baffle.jpg   89.79KB   29 downloads

Next project will be 1800 x 600 portable panels with 3 inch acoustic foam for primary reflection points.

[Grainy]

Nice job DRC, now I'm going to have to pretty up my bits of foam

[O.Sydney]

This thread has given me some inspiration. The listening area is, well, an open plan dining/lounge area so the WAF is pretty low in terms of getting room treatments. The room also really needs them. Bugger.

As The Chef keeps different hours to me, I thought it could work if the room treatments were easily portable and could be stored in the spare room when not in use.

Project 1 - Flat Panel Treatment
Disused picture frame in the shed (no glass). Cut 4 cm thick acoustic foam to frame size, then hot melt glue to the frame. Visit Spotlight and get hold of a few meters of light weight fabric in the clearance bin. Cut fabric to size and staple gun to the frame. WAF is quite high.

 baffle.jpg   89.79KB   29 downloads

Next project will be 1800 x 600 portable panels with 3 inch acoustic foam for primary reflection points.

Impressive, don't forget to post some pics of the next project

[Luc]

Any updates from respondents to his thread on how their treatments are going? I'm about to wall mount a monitor or 42' TV on a swivel mount possibly or even recess it in to the wall so I'm half way interested in treatments

[Grainy]

Not much to update.... never got around to pretty'ing it up, I'm sitting here now listening to music with it setup pretty much the same way as in post #26, althought the lights are much dimmer......

[:) al]

~ I've not seen anything that says adding diffusion to a front wall is a good thing unless dipole speakers are being used (which I know nothing about so wont comment)

Focal suggest for their speakers a live front wall ie behind their speakers, and I myself do think works extremely well

I have also experienced good benefit in covering front of a panel with egg crate style treatment but not something I myself have bothered replicating.

Is there any measured benefit anyone has been able to establish with regard treatment over a front panel ?

[Paul Spencer]

Of all the places in a room that you could treat, why choose the one that requires you to remove the treatment often?

 

In most situations, you can treat a room well enough with careful arrangement and acoustic treatment in places where things don't have to be shifted all the time. Also it pays to remember that whilst a TV might look more specular to visual light, from a sound wave point of view it's no different to a flat wall.

[Luc]

So Paul,  are you saying don't bother or no need to worry about that wall mounted flatscreen TV people like me are putting in(or up )?

 

I'm in the beginning stages of doing a refurb of my listening room, you can see where I'm up to here  Cave refurb my wall mounted TV (which will be mainly used as pc monitor) will be surround by shelving that's full of books and I wasn't worried about it all until I reread this thread. I still have a little bit of room to move as far as initiating some treatment[s] for this particular wall as the bespoke shelving and across room bench/entertainment unit are still to be built although the timber has been ordered.

[Grainy]

Is there any measured benefit anyone has been able to establish with regard treatment over a front panel ?

 

When I had standmounts in front of the flat panel there was a distinct difference covering the TV, with more clarity in the centre of the soundstage. I admit it was "perceived" but not "measured", how would you measure this?

 

However the floorstanders I have now don't really suffer the same issue. I'm assuming its to do with the rear port being higher up with the standmounts.

[Paul Spencer]

Treating any significant area is readily measurable in an ETC plot and also audible. However, putting a plasma on the wall does not make it imperative to treat that spot. If you didn't need to treat it before, you don't need to do it now.

 

The real issue here is front wall treatment. The factors here are more complex than people normally consider, taking into account psychoacoustics, speaker radiation issues and also the goals that you have in mind - I don't propose a one size fits all approach to room treatment.

 

Don't let your eyes fool you - it might look shiny, but from the point of view of sound waves, it's only different to a flat wall if angled. Why is this so? Science tells us that it's a simple matter of the way a wave behaves. Wavelength has a relationship to undulations in a surface. Since light has a very small wavelength, the small undulations on a painted plaster wall creates a visible difference to a very smooth flat glass surface. But you have to consider that sound waves are much longer in wavelength. A 1k tone is actually a foot long in wavelength. Even at 12k it's still around 30mm. Glass and plasterboard are both perfectly flat to the sound wave. With that in mind, sound waves behave no differently with glass compared to plasterboard - at least not to any degree that matters here.

 

FYI - what is the frequency range of visible light? 430 - 790 THz ... or to put it in relative terms to audio, 430,000,000 - 790,000,000k! In other words, the longest wavelength of visible light is 20 million times smaller in wavelength than 20k.

 

It's entirely possible that you might hear differences in sound stage depth, the size of the sweet spot and the degree of image focus. This depends also on the radiation of your speakers. Dipoles will reveal differences here more than most speakers due to the strong front wall reflection.

 

In a lot of situations I'd suggest it's not worth the bother to have removable treatment over a TV. If you are certain it's giving you an improvement, and it's the only thing you are doing as treatment, I'd then say don't stop there - keep going! If you think that is an improvement, much more is possible.

 

So ......................................... does all this boil down to "don't bother?" Most of the time - yes.

Edited by Paul Spencer, 06 June 2013 - 01:03 PM.

[Luc]

One less worry then, thanks.

[David.M]

Yes - a wall mounted TV is not in desperate need of being covered and IMHO, not worth the inconvenience.

I had pretty much the same advice from acoustician David Spargo when he was here measuring my room.  I do continue to cover it though as I find the light reflections on the panel distracting, I've not bothered to spend time trying to hear a difference between in covered or not covered.

[:) al]

yep why I havent particularly bothered