Hi Fi Amp Speaker l/r out to single Speaker, possible?

Hi everybody, a long time already I wanted to ask if it is possible to have a stereo Hi-Fi amplifier, connecting left and right canal out to a single speaker, what would happen to the signal connected to the other two speakers? Would it shorten the amplifiers end stage and render the stereo signal mono?
I need some guidelines on how to set this up, I have a single bass speaker that I would like to connect to the second speaker terminals as a bass Boost.
Any ideas anybody?

If you have a dual coil speaker, you can hook up one channel to each coil.

If you have a regular single coil speaker, connecting both channels to the same coil will cause the channels to fight each other, which may damage the amplifier. You need a separate amplifier to drive the bass speaker. Or, if your amplifier has spare secondary outputs (which is what I assume you mean that you have), you can connect the bass to either the left or right channel (but not both together). For most types of music, the bass frequencies are mostly monophonic so it doesn’t matter which channel you pick.

How about using Diodes to prevent feedback to the end stages?

No, both channels are AC, and you’d rectify the signals of both channels and it would sound crappy.

You could add 8 ohm resistors (assuming 8 ohm speakers) in line with the non-common line of both left and right channels. You’d be reducing the power to the speaker, but protecting the amplifier.

Would not Diodes(not rectifiers) let the signal pass trough one way but not the other and so prevent the feedback and why should that affect the sound properties.
Your suggestion with the resistors would requirer what kind of resistor and what wattage?
Thanks so far

Diodes are rectifiers. Diodes would affect the sound because the sound signal goes both positive and negative. It’s an AC signal, not DC. So one of the wires is the common, at ground (0) potential. The other carries the signal, and the voltage alternates between positive and negative. The current also alternates sign, flowing one way then the other. If the current is a low frequency sinusoid, and you run it through a diode, you chop off the negative half of the sinusoid, and what is left now has lots of frequencies, so the sound has become distorted. It would sound awful.

As for wattage, it would depend on how much wattage the amplifier has. If the resistor and speaker had the same impedance, the resistor would need to handle 1/4 the wattage amplifier can put out. Speaker impedances aren’t exactly their nominal value, but can be lower at some frequencies, so handling 1/2 the wattage would be a good idea, to give you some margin.

This is really the best answer. Trying to hook up a bass speaker to your existing amp’s output will cause problems at the very least, and may even fry your amp.