[Bumpy]

What acoustic treatments on either the front or rear of the baffles can people recommend.

[mcgsxr]

I know that some have used cork to good effect.

I never tried it though, so I do not speak from experience.

[Bumpy]

Yes its a topic which is not discussed much. Aside from cork I have seen the use of felt, but is it just cosmetic?

[Tone Depth]

My understanding is that the crossover is designed for the specific driver models and baffles. It would follow that if you are contemplating acoustic treatment on the baffle, you may want to also contemplating reworking the crossover.

[matevana]

I have had good luck using baffles made of constrained layers. Instead of 3/4" plywood for example, use three layers of 1/4" ply separated by damping sheets (roofing felt, etc.) and bonded with green glue (viscoelastic compound).  Once the raw boards are glued, clamped, and cured, I then proceed to cut baffles from the newly created stock.

Some of the autosound companies offer exotic damping materials that convert vibration into heat. They can be very expensive and I have found only a small difference in performance between those materials and roofing felt from Home Depot. If you opt for the type with adhesive on one side (peel-n-stick) you can save some time, but don't omit the green glue altogether. 

As for the exposed surfaces of the baffles, I have always preferred them to be untreated in OB.

[Bumpy]

I have had good luck using baffles made of constrained layers. Instead of 3/4" plywood for example, use three layers of 1/4" ply separated by damping sheets (roofing felt, etc.) and bonded with green glue (viscoelastic compound).  Once the raw boards are glued, clamped, and cured, I then proceed to cut baffles from the newly created stock.

Some of the autosound companies offer exotic damping materials that convert vibration into heat. They can be very expensive and I have found only a small difference in performance between those materials and roofing felt from Home Depot. If you opt for the type with adhesive on one side (peel-n-stick) you can save some time, but don't omit the green glue altogether. 

As for the exposed surfaces of the baffles, I have always preferred them to be untreated in OB.

Thanks for that Matevana

I too would ordinarily leave my baffles untreated, but circumstances dictate I run them just 1m from the back wall. I can picture some of the sound waves bouncing off the wall then reflecting back again from the rear of the baffle  towards the wall ad infinitum. The room is also one of our living areas so wall treatments are a big no no. Sound treatment on the rear of the panel seems a viable alternative.

[matevana]

How about something like this, applied to the rear of the baffle (self adhesive) ? 

https://www.parts-express.com/sonic-barrier-1-2-acoustic-sound-damping-foam-with-psa-18-x-24--260-520

[FullRangeMan]

Yes its a topic which is not discussed much. Aside from cork I have seen the use of felt, but is it just cosmetic?

Not cosmetic, felt attenuates the hi freq.
Baffle treatment are restrict to external side, I have never see a internal baffle treated as it is said it sound better untreated_non stuffed. What you can do inside aside stuffing is paint black all the speaker inside for less resonances.

[Bumpy]

Not cosmetic, felt attenuates the hi freq.
Baffle treatment are restrict to external side, I have never see a internal baffle treated as it is said it sound better untreated_non stuffed. What you can do inside aside stuffing is paint black all the speaker inside for less resonances.

I would be looking to treat most this reflective area. Mine are the black panels

[Bumpy]

How about something like this, applied to the rear of the baffle (self adhesive) ? 

https://www.parts-express.com/sonic-barrier-1-2-acoustic-sound-damping-foam-with-psa-18-x-24--260-520

Yep that's an option. Anyone guess as to what it does to the sound quality.

[matevana]

It will probably sound a bit less lively (more dry), which is usually one of the more sought-after characteristics of OBs. It will likely affect the energy from reflections in the mid to high-ish frequencies more profoundly. There are so many variables that are room and system dependent.  The outcome can vary tremendously, but it's a relatively cheap fix to attempt.

[Chicken Man]

I suppose one could mount one's drivers on a thin sub-baffle above the main baffle with an acoustic absorbent layer in between. This would help isolate vibrations being transmitted to the main baffle.
Possibly rubber matting glued to the sub-baffle might be useful here with the corners of the sub-baffle being fixed to the main baffle with screws.

Any sound improvement would come from the isolation of bass frequencies vibrating the main panel. Physical time alignment is also a possibility with different sub-baffles for the woofer and the midrange, with the tweeter mounted on the main baffle.

I might give this a shot when I get the time.

C.M 

[Bumpy]

I suppose one could mount one's drivers on a thin sub-baffle above the main baffle with an acoustic absorbent layer in between. This would help isolate vibrations being transmitted to the main baffle.
Possibly rubber matting glued to the sub-baffle might be useful here with the corners of the sub-baffle being fixed to the main baffle with screws.

Any sound improvement would come from the isolation of bass frequencies vibrating the main panel. Physical time alignment is also a possibility with different sub-baffles for the woofer and the midrange, with the tweeter mounted on the main baffle.

I might give this a shot when I get the time.

C.M 

You have given me an idea. If I mount acoustic foam to say cardboard I can hang it over the rear of the panel without making any fixings. That way I can judge if I like the effect without damaging the baffle itself.

I'll stick some pictures up when I get round to doing it.

[matevana]

I had a chance to play around with my current OB speakers last night. I placed them exactly 3 ft. from the wall and used painters tape to attach 3/4" open cell foam to the rear of the baffle on the left speaker only. I then used my DAP's remote to pan side to side from the listening position.

There was a slight difference, although I'm not sure it was for the better. First off, most of the smearing that occurred by having the speakers a bit too close to the wall was not aided by the addition of foam. I assume the 3/4" foam offered little absorption of low frequencies. It did however remove some reflection above that; I'm just not sure this benefited the presentation overall. However, it became clear that the sound greatly improved by removing the foam all together and sliding both baffles away from the wall an additional foot.

Have you considered mobile bases?  Something that would allow you to more easily move the speakers into position when listening, and then moving them back.   

[JLM]

Don't judge treatments by appearances.  Open cell foam is acoustically useless.  Absorption of low frequencies via treatments is extremely difficult.  Look at the GIK 242 vs. 244 panels (uses Owens Corning 703 high density fiberglass which is perhaps the most effective material) to get an idea of what's required.  Note that diffusion of low frequencies is near impossible. 

Putting a secondary baffle on the rear would tend to turn the dipole into a dipole/enclosed hybrid speaker. 

Thin baffles become flexible, which generates secondary sound waves.  In fact any unsupported baffle (smaller/stiffer/heavier is better) acts like a springboard that generates secondary sound waves.

[Voncarlos]

Anyone remembering the unique '80's "Spica TC-50" speakers would have noticed the front baffle was covered with felt. Memory seams to think it was 1/4."
My Magnaplanar MGIIIs have a 2mm felt surrounding the ribbon.

[S Clark]

Felt has real and measurable effects on FR.  I've been present when Danny Richie was measuring speaker responses and applying felt to rear baffles and front.  I remember that on front it smoothed out diffraction ripples.  I don't remember the exact effect on back, but I think it lowered a resonance peak. 
Also JimDGoulding has sold a felt tweeter ring "DiffractionBeGone" or something like that.  Do a search and you can find discussion and some measurements.