Suitcase Luggage Mixer

Thread Starter


Joined Feb 16, 2010
For my senior capstone project, I have to design a stereo into some old vintage luggage.

We've got the speakers all placed and laid out and are finalizing the electronics. One of the last parts is a mixer since the output of the system is stereo and we have 5 speakers (1 woofer, 2 mids, 2 highs).

Most of the opamp mixers I've found are inverting. Would having the low signal inverted be bad? Both lows would be summed and inverted so I'm not sure if phase cancellation is going to be an issue or not.

Bob Adams


Joined Nov 30, 2010
Reversing the polarity of only the low frequencies is bad. Fortunately, the speakers have wires that you can connect backwards.

Did I figure out your question correctly?


Joined Dec 26, 2010
The signals presented at the speakers do indeed have to be in phase, although as mentioned this may possibly be arranged by choosing which way around to wire them. If ALL the signals are inverted there would be no obvious effect, but reversing say the woofer with respect to the mid-range would be a problem.

There may be some subtle effects in the ear's response to the relative phase of harmonics, but one nasty effect comes from the fact that division of the signal into different bands to drive the different speakers cannot be perfect. Near to the "crossover" frequencies, some signal goes to more than one speaker. The result of reversing one of the speaker signals but not another may be that the sound from them does not blend together properly. The result may not be as obviously bad as reversing one set of a stereo pair, but it's worth getting it right