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About 10 years ago, I built some loudspeakers for college course credit. I figure if I had to build something for college credit, I might as well build something I'd use, instead of something like a voltmeter. The speakers were based off of Professor W. Marshall Leach's speaker plans. Prof. Leach is an electrical engineering professor at Georgia Institute of Technology, my alma mater.
Just last month I noticed that one of my mid-range drivers had holes in it and it made the speaker sound like ca-ca. From the looks of it, the foam material of the cone has deteriorated. So it was time to replace the mid-range driver. I tried driving by the shop where I originally bought all the drivers and crossover components, but I was met with an Asian gynecology clinic in the same location as that the electronics store was located 10 years ago. Doh! So I did a web search and finally struck paydirt when I searched on "Peerless mid-range driver", where I discovered that the shop I bought my components from had just moved a few miles away from the clinic. The shop's name is Audio Lab of Georgia. You can still get all the drivers and crossover components you need for GT speakers from them (with the exception of the wood for the enclosure and some miscellaneous items that you need from Radio Shack and a hardware store (Ace or Home Depot is your best bet). While I was at their website I noticed that they had links to Prof. Leach's speaker plans, and a link to his home page where you can find plans for the the Leach SuperAmp, 2-way bookshelf speakers, and 3-way satellite speaker system. There some more plans on Prof. Leach's webpage, please check them out if you are so inclined.
The new crossover network now looks like this:
As you can see some tweaking has been done to the tweeter section, and to the mid-range. I've always felt the original crossover network emphasized too much on the high/mid-range, and the new crossover network definitely takes the sting off. The added resistors in the mid-range crossover acts as a current divider and lowers the current that feeds the mid-range driver (while still maintaining an 8 ohm load for the receiver/amp. Note: I used a 100 microFarad capacitor in the woofer network (instead of the 50 microFarad capacitor) to roll off the half power crossover point at 300Hz instead of 400Hz.
The Before stage: Here is a shot of the original crossover over network inside the speaker cabinet:
The During stage: Here's a picture of the mess once I ripped out the components that needed to be replaced and all the tools I used for the upgrade:
The After stage: Here's a couple of pictures of the newly installed network components. I had to make due with whatever space I could find given the constraints of the wire leads of the new and existing components and having to implement the new crossover network design as depicted:
The crossover upgrades cost me around $20, and the 2 mid-range drivers cost me around $80, so I guess it was worth it to me to pay $100 in upgrade parts instead of buying new speakers that would have costed me $400/pair and upwards. How many others can say when they upgrade their speakers, they really upgrade their speakers? :)
If you like DIY projects, and have $350 to blow on speakers, these might be a good project for you (if you're handy with a soldering iron, and other wood cutting appliances). Many people use MDF (Medium Density Fiberboard - 3/4" is my recommendation) for building flexy racks to house their home theater components. I would like to see someone use MDF to build a pair of speakers with. If MDF is good enough for NHT to build their speakers with, I don't why it can't be used here with these speaker plans. Using MDF might chop off $25-$50 off the final cost of the pair of speakers. See Prof. Leach's web page for the details on loudspeaker construction (from obtaining the wood, the cutting diagrams, to the crossover component parts suppliers). I can recommend the folks at AudioLab of Georgia very strongly as a supplier of the drivers and the crossover components.
I wish I could give out some "tech" specs on these speakers, but I can only offer that they should easily handle 100W/ch (maybe more since most of the power goes to the woofer, and the mid-range itself is rated at 100W). I will venture that their SPL could be rated around 88-89 dB. If I had some test equipment, I'd try to come up with the rating specs. I recommending using these speakers in tandem with a powered subwoofer to lessen the woofer's load. One day I'll consider staining them some nice wood color, but I'm just not good at choosing a color and then later having painter's remorse on the color choice, so they stay nice and light for now. Please contact me if you have any questions (can't say I'll be able to answer all of them!) and if you do build the speakers, I'd like to see pictures of their construction, and the progress in building them.
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