Ok forget boxed ESLs

[Borat]

i have already expressed this idea years ago on madisound but i am now revisting it with respect to ESLs

have a gigantic slab of foam attached to the back of ESL panel.

this would in effect realize an enclosure-less transmission line. the backwave would be delayed and attenuated therefore reducing out of phase cancellation and boosting on-axis output.

directivity benefit of dipole operation would be preserved as the attenuation would be partial at all but highest frequencies. at highest frequencies the width of ESL panel will be enough to ensure directivity.

at low frequencies radiation pattern will switch from dipole to cardioid with a boost of on-axis energy.

at high frequencies front radiation will remain unchanged while rear will be eliminated.

in other words there will be a performance benefit at all frequencies.

placement will be greatly simplified.

what do you say ?

[DavidJanszen]

Seems like a good idea to me, certainly for large, wide range panels. Let us know how it works.

I think another interesting approach is to put a diffuser to the rear and send the highs and mids off sideways.

[bolserst]

Originally Posted by Borat

i have already expressed this idea years ago on madisound but i am now revisting it with respect to ESLs

have a gigantic slab of foam attached to the back of ESL panel.

this would in effect realize an enclosure-less transmission line. the backwave would be delayed and attenuated therefore reducing out of phase cancellation and boosting on-axis output.

directivity benefit of dipole operation would be preserved as the attenuation would be partial at all but highest frequencies. at highest frequencies the width of ESL panel will be enough to ensure directivity.

at low frequencies radiation pattern will switch from dipole to cardioid with a boost of on-axis energy.

at high frequencies front radiation will remain unchanged while rear will be eliminated.

in other words there will be a performance benefit at all frequencies.

placement will be greatly simplified.

what do you say ?

If you haven't already seen the following websites, you might check them out.
Pretty interesting results for cardioid woofer response using rear damping in a dipole woofer similar to what you described.

NaO U-frame

DIY-dipole-1

Whether or not a similar damping technique will work with an ESL...that is the question.

[norman bates]

I cannot speak for a foam enclosed woofer, but I had a 3" thick foam box around a w3-871s run open baffle. It sounded wonderfull and could be moved up against a wall.

I now have a 4 x 4" focused array open backed box (2' tall x 2' wide x 19" deep) with the back blocked by 3" thick foam slab.

I want open baffle clarity to the midrange, but do not want the wall bounce nor forced to place a speaker at least 5' from the front wall (10mS delay).

To me it is not an option, it is a requirement.


Check it out on the full range forum here under "4 driver focused array".


Norman