One for the Audioisti

My head unit has stereo preouts for a subwoofer. I'd like to make use of this rather than using the crossovers on the amp as it lets me alter settings from the driver's seat rather than by fiddling with an amplifier. The amp I'm thinking of getting is an Alpine MRV-F407. The manual for it has instructions how to wire it up for a subwoofer, but using the HPF in the amp.

The manual is here FWIW, wiring diagrams around page 18:

formatting link
What I'm wondering is can I connect my stereo sub output to input channels 3 and 4 on the amp, then bridge the output to run a sub? I know bass isn't directional for your ears, but that doesn't mean that both left and right channel are going to be the same on the actual recording... I'm thinking of getting an Elemental Designs sub as they're cheap and small, and they have dual voice coils, which would mean I could wire each channel to a voice coil, but I suspect that would also be A Bad Thing.

I'd be very pleased if someone actually knows...

Reply to
Doki
Loading thread data ...

Make up an adaptor with a 10kohm resistor in series with each output 'live' ie the centre connection of the phonos etc and parallel the output from those. The grounds can be simply paralleled - or use just one.

I can't access the link you've given on this machine but I'd expect a good head unit to have low impedance drivers to external amps and those resistor values should be ok for most.

Reply to
Dave Plowman (News)

I'm not following this. Are you saying I connect the two "live / hot" wires together with the resistor and leave everything else in place, so the amp sees the same signal on both inputs?

According to the specs in the back of the book for the headunit:

"Preout max output level / output impedance" "6.5V / 100 ohms"

The spods on the audio forums reckon it chucks out 4.8V RMS in reality.

Reply to
Doki

Argh. Another reading of the manual suggests that when using a single stereo input to channels 1 and 2, you can set output channels 3 and 4 to take their input from 1 and 2, then set the HPF and it'll happily run a bridged sub, which suggests it doesn't mind being bridged with stereo input. I need to find out more about how car amplifiers work - there's no need to add an actual bridging wire to this amp, so I suspect there's something funny where the negative output for channel 3 and the positive output for channel 4 are always at the same voltage.

Reply to
Doki

Yes. You can usually just parallel inputs - it's paralleling outputs that can cause problems.

I'd expect the sub amp to have enough spare gain to make up any loss from the attenuation of the resistive mixer.

Reply to
Dave Plowman (News)

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.