I recently picked up some old (70s/80s?) Leslie speakers. (Leslie 450M and 40S) THey are basically two huge speaker cabs with an amp built into one of the cabs. The other cab then connects to the one with the amp via a 6pin Leslie cable. My question is: Can I connect a CD Player into a quarter inch jack? The cab with the amp in it has an "input" jack on the back of it, it is a 1/4 inch jack like the type normally found on a guitar amp or whatever... But I am told that these speakers were definitely part of a hifi system and not used for a musical instrment... I believe they used to have a reel to reel tape player connected to them. ANy ideas or help would be greatly appreciated! Thanks!
Assuming the 1/4" jack is meant to accept a line level input, you should be able to connect a line level output from a CD player via a simple adaptor. You haven't stated whether the 1/4" plug is meant to take a mono or stereo signal. Until you know what sort of signal the speakers are expecting as an input, you shouldn't simply assume that going from a RCA to a phone jack will get you the sound you desire or won't possibly do some damage to one of the components. You should never combine outputs from two (stereo) channels to make a mono signal without using an appropriate device such as a transformer.
You also haven't stated how you expect to control the volume of the system. You haven't mentioned any type of control provided for this function. You really shouldn't use a headphone output from a CD player and rely on the volume control provided for the headphones. The voltage and impedance of headphone jacks are typically not correct for a line level output.
You need to work out the details of at least these two obstacles before you start plugging things together and expecting it to all work out and hang together.