[youngho]

Clearsorber would be a very good product for what you're seeking, though I don't know about current availability in the US. I know that the Walters-Storyk Design Group has used it in studio projects, even in a pool house! https://wsdg.com/projects-items/morro-do-chapeu-residence/.

One product I just ran across that you might also consider are translucent acoustical curtains https://www.empa.ch/web/s604/curtains-that-quench-noise, available through Wolf Gordon: http://www.wolfgordon.com/print/content/14258/carmen-carm-902ad.pdf?q=gnum%3D%26category%3Ddrapery is a non-gloomy option. Obviously, this is a compromise, but perhaps worth the trade-off for light transmission...

[nickd]

The issue of budget is relevant here.
Not all windows are created equal. Hard wood frames, heavy laminated glass, double and triple Pane etc.
smaller panels and shaped trim for diffusion. The options are only limited by budget.

That said, heavy insulated velour curtains with vinyl blackout backs really warm up the room. You might like them and they are not crazy expensive.

Plantation Shutters can be a help too. Provided they are tight and don't rattle. The Faux wood versions are surprisingly well damped and they provide a bit of diffusion.

Some ideas anyway.

[EVOLVIST]

This thread is getting really great!

[ryno]

I have dipole speakers, and 3 windows across the front wall. I had medium weight drapes that were recently replaced by 3 GIK polyfusors.
http://www.gikacoustics.com/product/evolution-polyfusor-diffusor-absorber-bass-trap/
There was a great improvement in image stability and width. I need to attach material to the backs of the diffusors. From the outside it looks like my windows are boarded up.
Ryan

[jk@home]

...You could also use double- or triple-cell cellular shades as an alternative or even in addition to the curtains, though I don't know about absorption data...

I have windows on one sidewall, and do double cellular blinds there (innies and outies). But at the point of reflection, still use a floor absorber.
http://imagizer.imageshack.us/v2/640x480q90/540/K3fFQH.jpg

Did the OP say what kind of speakers he had, do they even output any energy from the back?

[EVOLVIST]

I have windows on one sidewall, and do double cellular blinds there (innies and outies). But at the point of reflection, still use a floor absorber.
http://imagizer.imageshack.us/v2/640x480q90/540/K3fFQH.jpg

Did the OP say what kind of speakers he had, do they even output any energy from the back?

Actually, my new speakers aren't in yet, but I'm getting Audio Physic Avanti 30th Anniversary speakers. There is energy, though they can be moved about 2ft from the front wall, so that's a bit better than most.

[JWL.GIK]

Some good ideas here. Windows are a challenge to treat for sure, because you can't really mount anything to them. Also, materials that are good at absorption tend to not be very flexible, so roll-up type solutions are a challenge.

Usually the best solution (in terms of performance) is to use panels on stands in front of the window. If that's not acceptable aesthetically, then use some nice thick, gathered curtains to get as many highs as you can, and make sure you have good bass trapping elsewhere in the room (perhaps in the ceiling and/or floor corners above & below the window?).

Also, keep in mind that in terms of high frequencies, the front wall behind the speakers is the least important of the 4 walls to treat.

[mirekti]

Thanks for all of the comments, y'all. Thanks for GIK being great at what they do.

Just for giggles (not for this thread), I drew out my 12x12x8 listening room. I should have made it more in line with the grid. Quick and dirty.

My situation is very similar to yours. I am using drapes, but there is also a 55" TV in front of the center window.
When I listen to the music I push the TV all the way back to the window and use two rather thick blankets, fold each of them and put one on top of the other to cover the TV.
Usually TV between the speakers is no, no, but in my case it actually helps.

The other thing is, my chair is rather close to the speakers, I listen in near filed.
You should push that sofa two blocks ahead and toe in the speakers (if the configuration and speakers permit). You will get less room, and more music.

[advanced101]

My speakers each have a set of rear firing tweeters.  I put a Polyfusor on all three window sills.

[advanced101]

.

[doggie]

How about vertical panels suspended from the ceiling from a track or rail so that they could be pulled to the side uncovering the windows when not listening?

It would also allow for fine adjusting/tuning.

[Ace Deprave]

How about vertical panels suspended from the ceiling from a track or rail so that they could be pulled to the side uncovering the windows when not listening?

It would also allow for fine adjusting/tuning.

That would be cool, maybe on a barn door type track on the wall.

[Hipper]

I'm not quite clear what you want, Evolvist.

Could you write a specification?

Do you for example want to keep the windows clear when listening? Or, do you want something in front of it when listening that can be easily moved and stored when not required - more easily moved and stored then a panel on feet, such as a curtain, blinds, or something on rails?

And then, what sound problems are you trying to deal with? A frequency range, say.

For me I see nothing wrong with moving panels on feet. They are not heavy, but perhaps they could be put on castors or rollers. Of course there needs to be a place to store them when not in use, but that applies to any product.