The low frequency outputs on my crossover are in stereo. I was Lacking power so I am now using a Mono bridged amplifier to run a dual voice coil subwoofer. I prefer the transparency of the Amp chips that I was using. One by it self lack power. Running one chip per voice coil is ideal. Is it OK to run 2 Phono in to 1 and then back in to 2? My aim would be to sum the line so that both voice coils are running unison.
I'm not quite sure what you mean by the 2 into 1 and then back to 2 bit... but summing stereo outputs is fine but they should be mixed resistively or even better by feeding into a virtual earth opamp (inverting opamp mixer stage) Connecting normal L and R outputs together can cause odd effects because the outputs are normally low impedance and so they end up "fighting" each other depending on the material, its phase and amplitudes and so on.
It is certainly easier to run two mono power amplifiers feeding the two voices coils, rather than using a bridged arrangement feeding the series coupled voice coils.
BUT !!!!!!
The two mono signals feeding the two voice coils must be the same and of the same phase.
This requires the two stereo channels to be summed (that inverting summer Mooly talks about) and filtered (a low pass active filter). This filtered output is then fed to the two power amps. That ensures the power amplifiers are being fed with the same input signal.
Do you need to install a comparator on the two output such that an indicator flashes to tell you that the output from one channel is significantly different from the other?
BUT !!!!!!
The two mono signals feeding the two voice coils must be the same and of the same phase.
This requires the two stereo channels to be summed (that inverting summer Mooly talks about) and filtered (a low pass active filter). This filtered output is then fed to the two power amps. That ensures the power amplifiers are being fed with the same input signal.
Do you need to install a comparator on the two output such that an indicator flashes to tell you that the output from one channel is significantly different from the other?
I disagree that the two signals fed to a dual-coil woofer need to be the same. The left and right channel signals will be effectively summed (in the magnetic domain) by the two voice coils, yielding a summed-mono acoustic output. This approach is used in some commercial passive woofer systems that use a single, dual-voice-coil woofer. Each channel is connected to one woofer coil.
Phase IS important, so make sure to keep the +/- (or red/black) speaker cables oriented correctly. Otherwise, signals that are the same in each channel will cancel, and undesireable effect. And of course, a passive lowpass filter will need to be present between each channel and each voice coil.
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