consistent Posted February 17, 2013 Share Posted February 17, 2013 Hi Guys Some advice please. I have swapped out the K55 for Altec 291-16k, what a beautiful driver but a little hot for the K77 and K33 in the AK4 network. So I added an L-pad attenuator (50w 8 ohm). Works well be the K77F which surprises me. The pad seems to work well but not sure if it should be 16ohm for the driver? Also if i have a fixed L-pad of say 3db and 6db should it be 16ohm and what should the wattage be? Thanks Quote Link to comment Share on other sites More sharing options...
consistent Posted February 18, 2013 Author Share Posted February 18, 2013 Bump...Help! BTW I have fixed the Altecs on Le Cleac'h horns...very different to traxtrix...I think I hear more on the stage as instruments and vocals have a clearer space...the sound is cleaner Quote Link to comment Share on other sites More sharing options...
Chris A Posted February 18, 2013 Share Posted February 18, 2013 Perhaps djk, DeanG, BEC, or speakerfritz can provide a better answer, but my $0.02, based on a little data, is below... ...what a beautiful driver but a little hot for the K77 and K33 in the AK4 network. So I added an L-pad attenuator (50w 8 ohm). Works well be the K77F which surprises me. The pad seems to work well but not sure if it should be 16ohm for the driver?Here is a listing of K-55 impedance values vs. frequency that Bob Crites measured (that I assume was measured while attached to a horn such as the K-400, etc.):http://forums.klipsch.com/forums/storage/3/667382/k-55mimp.pdf I think that the K-55 is really a 11-14 ohm impedance device, and your inserted lpad is showing 8 ohms to the crossover/balancing network. Perhaps simply adding a low-value, high wattage resistor in series with the Altec driver and removing the lpad, then listening and adjust the values based on a hand-held SPL meter to get close. Not sure of the shape of the Altec driver's impedance curve and corresponding SPL curve, however, so this is a bit of a shot-in-the-dark suggestion. Chris Quote Link to comment Share on other sites More sharing options...
Chris A Posted February 18, 2013 Share Posted February 18, 2013 Here is the reason why I made some of the comments, above: the impedance of the K-55/K-400 on a mid-1980's vintage Klipschorn shows a big impedance loop... Quote Link to comment Share on other sites More sharing options...
consistent Posted February 18, 2013 Author Share Posted February 18, 2013 Thanks Chris...that is a big loop of impedance. My thinking was that as the K55 is nominal 16 that the 291 (nominal 16) would be a good fit dropped by a few db as it is about 3db more efficient/w/m. I am not sure what damage (if any) I am doing to the network or driver load (the amp should be spared) but by dialing what my ears perceive to be the right balance (ohm meter test also) with the 8ohm L-pad it sounds pretty damn good with a good balance of tone in peaks. cheers Steve Quote Link to comment Share on other sites More sharing options...
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