Speaker Projects

No that is not a fireplace. It is a subwoofer built into a mantel from a defective electric fireplace. I bought the mantel for $5 and then braced it up and sealed it with caulking. I glued a baffle plate in the opening and closed off the back to make a sealed cabinet of about 5 cubic feet but taking up very little floor space. The single 12" driver is a closeout item from Parts Express which cost less than $20. I am using a salvaged plate amp to power it. The entire thing cost me well under $50 and I have good solid output down to the limit of hearing and a little beyond. This will have to do until I can build my infinite baffle system into the wall.

The little knick knack table speakers are my main speakers. The are open baffle (i.e. no box) with a set of older Radio Shack 5 1/4" full range drivers which appear to be Foster OEMs as the primary drivers. They cover everything from about 180Hz up to beyond what I can hear. When playing test tones I could hear it up to about 12.5kHz however when I turned it on playing a 20kHz tone my dog Abbey went wild so I guess it gets up there pretty well.

The table speakers also include a 10" helper woofer made by Goldwood. This was another inexpensive driver from Parts Express. It's main attraction was a combination of a reasonably low fs (around 40Hz) and quite high Qts (more than 1). You might expect flabby bass with such a high Q but on an open baffle this is not the case. Since the lowest notes will be handled by the subwoofer this woofer is plenty.

If going without a sub I would have made the tables wider and gotten a better driver like the 15" augie from Hawthorn Audio.

The table speakers are biamped. The main amp drives the full range drivers with no crossover at all relying on the driver's natural roll off. Currently I just take the headphone output of my main amp and run it to the aux input of another stereo receiver which has the bass turned all the way up and the treble all the way down. This runs the woofers. It really works better than you would expect because of the natural rolloff of the full range driver on the OB at about 180Hz. The next step in the process is to build a proper crossover and tube amplifiers to drive it all. This should clean up the sound even more as there is really a bit too much overlap of the woofers with the full ranges and the subwoofer plate amp has about 70Hz as the minimum crossover frequency. Even as currently set up the sound is better than any other sytem I have ever had. Don't usderestimate the quality of wide range drivers in open baffles. It really brings the instruments into the room with you. You have to hear it to believe it.

The table speakers are now stained in early american. Later I will add black rubber balls as feet so that the wires can come in from underneath. The latest picture does not show the final finish which is brushed Teak Oil. For comparison the last speaker is my initial proof of concept for open baffle. They sounded so good that I embarked on the journey of building something that wouldn't annoy the wife.

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