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Our home has never had a good place to locate a woofer in the TV area. The rear screen 55 inch projection TV in the family room was built into a custom cabinet. Whatever new TV was contemplated would have to fit the furniture, not the other way around. When the old TV was replaced by a flat screen TV, a large space was left behind. The inspiration was to use the old TV cabinet and design a speaker to fit the constraints of the space and new TV placement.

A University CW-15 speaker had been salvaged from a building remodel years before. I had used the same speaker in building the University Classic theatre speaker with good success. I am indebted to David J McBean for his HORNRESP software and the Room EQ Wizard as a measurement tool.

The horn design is constrained by the mouth opening under the TV, the needed throat size of the speaker, and the volume of the TV box. A constant 15.75 inch height was maintained thru the expansion of the horn. Tongue and groove oak flooring was used to form the upper curve with reinforced composite board forming the bottom curve. An O-Audio 300 watt amplifier fit conveniently into the face of the cabinet. This provides vastly more power than is needed to drive the horn. It needs only a quarter of the power of the floor standing speakers. Total project cost was about $300.

The useable frequency response is from 40Hz to 350Hz with a THD distortion below 1% at 110Hz (SPL = 100) rising to 1.03% at 37Hz with a pressure of 86db. While not a spectacular sub-woofer, it does add a pleasant new lower end response. The speaker has met with load acclaim – as in – “turn it down , you’re shaking the whole house”.

Photos:
FTH-A: The old TV in the cabinet.
FTH-B: The removed TV before disassembly. The front of the TV became the flat back of the speaker.
FTH-C: Internal construction of the horn.
FTH-D: Assembled unit for testing.
FTH-E: Speaker and new TV in place. The speaker can be pushed back about six inches to give access to the TV connectors and then is rolled forward to snug up to the front panel. The TV hangs independently.
FTH-F: Front screen in place with grille cloth replacing wooden panels.
 

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Elite Shackster , HTS Moderator Emeritus
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Very nice work. :T

I'm going to move this into DIY subwoofers -- you'll probably get more questions about the horn design there.
 

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Cool idea.

Did you say took some measurements of its performance? I'd be curious to see the hornresp predictions too.

Very clever.
 

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You did a great job!
 

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Discussion Starter #12
Thank you for your interest. I have searched thru the design notes and include the predicted response and the measured speaker response. The microphone was placed in 3 positions across the face of the mouth at 6 and 10 ft. away. The results were averaged. The 2 curves are for microphone heights of 7 and 22 inches above ground. From the design software, just a few more inches of throat length would have slid the low frequency cutoff point noticeably downward but sometimes you just live with what you have.
 

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