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Bob Richards 5th December 2012 12:13 AM

Stereo Hologram Soundbar
I've designed and am building a Stereo Holographic Soundbar, and would be interested in hearing from others who have done something similar.

My box is 39 long, 16 deep, and 8 inches high. I've got 5 three inch drivers across the front, also 3 dome tweeters. I've also got a 6.5 inch woofer side firing near the rear on each end of the cabinet. The 42 inch (diagonal) TV will sit on top of it.

I'm using all active circuitry to do the L-XR function (removes most of the L+R from the feed to the non-L+R drivers), and the Polk style of inter-aural cancellation (hologram effect), and active EQ so the woofs are acoustically flat to 30HZ (running stereo and no L-XR processing), plus a 4 section Baxandahl tone circuit for final tonality adjustment. X-over at 150HZ is 4 pole active. X-over at 7kHZ is one pole passive. The processor chassis will drive 7 poweramp channels (60W+), which will drive the box. Any thoughts?

Elias 4th May 2013 10:26 AM

Any progress ? :D

How did the matrix worked out, did you find optimal x ?

Bob Richards 4th May 2013 05:55 PM

I decided to go passive on the L-XR and hologram function, so the box as a whole would only need 4 channels of power amp (instead of 7). The 4 pole Linkwitz/Riley crossover at 150HZ is all that's active now. It works better than I expected with X approx. equal to 0.5. Compared to the Carver electronic version, which I also have, you still need to be within about 2 inches of centered left to right, but the hologram effect is substantial over a very wide range on the Z axis. You can be up close (2 ft.), back on the couch (6 feet) or over by the fireplace (8 ft.) and the effect is still very strong.

If I had it to do again, I'd use 5 inch drivers rather than the 3 inch drivers I chose, since the 3 inchers have a hard time filling the room down to 150HZ without significant EQ. I chose 3 inch because the drivers are great, and I wanted to keep the cabinet as small as possible. I'll be putting some active EQ in the crossover for the upperband (a 6dB rise at 150HZ, flattening out above about 800HZ). The lower band (woofer) will have about 12 dB of active EQ at 35HZ relative to 150HZ. The crossover isn't done yet, but I've been listening to the upperband drivers all week. I'm also putting my 4 section Baxandall tone control circuit in the box with the active crossover, so the tonality can be well optimized regardless of level or room acoustics. I'll upload pictures eventually when it's fully done.

Bob Richards 10th June 2013 10:10 PM

I've finally finished The Stereo Holographic Soundbar project. I've created a page for it on my website. Click on this link, then click on Audio, then scroll down and click on Soundbar.
Bob's Website

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