Al Klappenberger Posted May 27, 2009 Share Posted May 27, 2009 Thanks to one of my local customers I have the lone of a Klipsch Forte. I hope to develop an improved crossover network to replace the stock network. I have been asked many times to design networks for people with nothing more to go on than a list of drivers from all sorts of manufacturers. I almost always have to say no. I hope to use this thread to illustrate what is involved in developing a network so people will understand why I usually decline their request as well as the primary objective to develop a new Forte network. This project is going to take a while and I will need to reserect this thread later after I order parts and build a prototype, if I decide to do that. I have already done a computer design but I don't expect to post it until later. The Forte model sold for around $1100 to $1200 when new. They seem to go on eBay for about half that figure tops. My experience developing a network for the original Cornwall shows that I must design the new network such that the total cost is not more than the cost of the speaker! This means I have got to cut a few corners. It also means that it might not be a worth-while product for me to offer. It that case I'll just give the design to the DIY community. The first thing I need to do to develop a network is to evaluate the speaker in its original configuration, then to evaluate the three individual drivers for complex impedance and sensitivity (efficiency). Here are the plots of efficiency, frequency response and impedance of the stock speaker. The frequency response is very impressive. It goes from below 30 Hz to 20Khz with a nominal sensitivity of 95 db SPL at 1 meter for 2.83V input. That would be 1W into 8 Ohms except that it is NOT 8 Ohms! The impedance is all over the place because of the usual cut-every-corner you can "balancing network" Klipsch put in all the heritage speakers! The impedance comes to a peak of 106 Ohms at 2150 Hz. At 950 Hz it looks to the amp like a 7.19 Ohm resistor in series with a 3 mHy inductor. At 5150 Hz it resembles 5.09 Ohms in series with a 1.68 uFd capacitor. Then at 14.5 Khz it's more like 9.28 Ohms in series with 2.59 uFd. This is all the result of the network. The individual drivers provide much more reasonable loads. Al K. Quote Link to comment Share on other sites More sharing options...
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