Heil with a JBL Woofer part 2 Back wave attenuation for best in room balance.

[Robh3606]

Has anyone tried any attenuation of the back wave?? I was just listening to a live recording and was impressed with how well the venue ambiance came through. That said on non live recordings I also get a sense of space but it seems the focus is less clear compared to either the F 206's or my horn systems.

I have been playing the the idea of trying to turn down the back wave just using some fiberglass batting to see if I can dial them in better. The goal is to increase focus but not loose the sense of space. I don't want to do an enclosure because of the potential of reflections back through the diaphragm just like putting a woofer in a box.

Anyone else try this?? I am going to give it a shot too see what happens.

Rob

[Robh3606]

This is worth playing with. At least in my room. I did a quick check to see what would happen using some 4" batting paper left on. It had a significant effect in room. Normally I couldn't hear a change in balance doing a sit down stand up test. I can now this did a great job of attenuation and effected the balance in the sweet spot. Better clarity more focus with little apparent loss of ambiance.

It is clearly absorbing a great deal of the upper octaves but seems to be frequency shading the back wave and attenuating it as expected.

With some experimentation I could reduce or increase the energy level but either increasing or reducing the thickness of the fiberglass behind the driver. Want to try and get some measurements to see exactly whats being shaded out and how much attenuation there is.

Rob

[Mr. Widget]

Hi Rob, I rotated your photo...

Interesting idea. For some reason all of the better ESS systems and many of the AMT systems by others have left the AMT driver as a dipole. I wonder if a better solution would be to place some Sonex or heavy curtains directly behind the speakers on the near by wall.

You may want to try both to see which you prefer.

On a parallel topic, I was considering getting a second pair of ESS drivers and running them stacked since it would be so easy to do with a length of threaded rod. I think this would help with the vertical dispersion.


Widget

[dkalsi]

On a parallel topic, I was considering getting a second pair of ESS drivers and running them stacked since it would be so easy to do with a length of threaded rod. I think this would help with the vertical dispersion.


Widget

Widget - see this crazy thread at Klipsch Forums - https://community.klipsch.com/index....-for-heritage/

[jmpsmash]

Widget - see this crazy thread at Klipsch Forums - https://community.klipsch.com/index....-for-heritage/

Very cool. I did try to look at what can be done. A while ago someone managed to do a quad stack. 4 on each side but didn't provide any measurements.

This one looks good except it still only go down to 500Hz with a fairly large "horn". Not high enough, not low enough. I hope he provide some distortion measurements too as that's one of the goal of going for an array.

[jmpsmash]

Back to the main topic.

When I first read it, I thought you meant putting stuff at the front wall. I have tried nothing (just normal drywall), 2" absorption panel, and some wooden pattern paneling that scatters the sound (it is not strictly a diffuser as it is not diffusing sound uniformly like a QRD, etc).

Dry wall: there are the most amount of ambience sound, creating a more live sound stage. I like that sound. However, instruments and voices are less focused mixing around all the backwave and front wave. My AMT is ~4ft from the wall. I have achieved better imaging with 6 ft from the wall but I have found that there are tons of low frequency issue with the speakers that far out.

Absorption panel: Best imaging, but the magic of the dipole is very much diminished. A/B comparison the sound is dry and liveness.

Scattering panel: Kinda in between, not the best of both worlds, neither the worse. but like 50% of each.

Now I am tempted with a proper diffusion panel like a QRD. Those are crazy expensive. I need a long weekend to DIY one.