[CarlXu]

Hi, I have a passive subwoofer (Kenwood SW-05HT) with two sets of speaker wire inputs (left and right). However, my amp (Fosi Audio BT30D PRO) for the sub only has only one output to the subwoofer.

How can I connect it to the SUB OUT of BT30D PRO?

[Letitroll98]

That amp's sub output is a line level output, 2v max with a few milliwatts of output.  So it can't drive a passive sub, which needs a power amp to drive it, somewhere between 100 to 500 watts.  You need a separate amp to drive the sub, another BT30 pro might work for that.

[Doublej]

Deleted, what I wrote made no sense as it is a passive subwoofer.

Do what Letitroll98 says. Get another Fosi, feed the pre out of the first Fosi to the input of the second Fosi and then connect the subwoofer to the second Fosi.

[CarlXu]

That amp's sub output is a line level output, 2v max with a few milliwatts of output.  So it can't drive a passive sub, which needs a power amp to drive it, somewhere between 100 to 500 watts.  You need a separate amp to drive the sub, another BT30 pro might work for that.

The amp has SUB OUT for passive subwoofer, but it has only one banana plugs output while my subwoofer has two banana plugs input.

I don't know how to connect from one output to two inputs.

[opnly bafld]

[mix4fix]

That subwoofer has left and right input and output terminals. You can always go from amp to sub to speakers. If you wire it off that single amp terminal, you will need to figure out if series or parallel wiring is needed for it to not under-impedance the amplifier.

[opnly bafld]

The amplifier has a volume control for the sub out, it would unwise to run the main speakers through the sub wiring unless they are the matching Kenwood KS-205HT speakers. It is a class d amplifier, it will be fine with the 8 ohm dual voice coils in parallel.

[mix4fix]

This is the input/output for that subwoofer. Looks like it is a dual voice coil driver with dual 8 ohm coils and a two-way passive crossover.

As for using high-level inputs, that's what they are designed to do. If I had that bass speaker, wiring some cheap and cheerful speakers could be an option.

[opnly bafld]

As for using high-level inputs, that's what they are designed to do. If I had that bass speaker, wiring some cheap and cheerful speakers could be an option.

It is designed to be used that way with the speakers included in the package, not just any speakers.

If wired through the inputs and outputs, how would one adjust for various sensitivities of different speakers?
A pair of 84 dB speakers vs 95 dB speakers are going to need different amounts of power going to the sub vs the main speakers to sound balanced, no way to adjust for that.

By using the 3rd channel of the amp with a volume control, the passive subwoofer is now a powered sub (without the ability to adjust the xo frequency). No adjustable low pass is an issue, but much better than a sensitivity mismatch.

The real answer of course is a powered sub with necessary adjustments, but the OP asked how to make what he has work.

[mix4fix]

It is designed to be used that way with the speakers included in the package, not just any speakers.

If wired through the inputs and outputs, how would one adjust for various sensitivities of different speakers?
A pair of 84 dB speakers vs 95 dB speakers are going to need different amounts of power going to the sub vs the main speakers to sound balanced, no way to adjust for that.

By using the 3rd channel of the amp with a volume control, the passive subwoofer is now a powered sub (without the ability to adjust the xo frequency). No adjustable low pass is an issue, but much better than a sensitivity mismatch.

The real answer of course is a powered sub with necessary adjustments, but the OP asked how to make what he has work.

Since he is wanting to use a low-end passive subwoofer, exact matching shouldn't be at the top of the list.

Since I don't have that amplifier, I would hook it up that way to my current old Denon receiver and run it like that understanding it is not going to be the best. My second system is about hearing something and not listening.

You can always remove the driver from the box, disconnect the cheap wire from it, and run a speaker wire from the driver to his amp's dedicated subwoofer output. Run series or parallel as needed. You bypass the cheap two way crossover and flimsy spring loaded speaker terminals. You can also buy a cheap driver to upgrade from the cheap, old driver that is in it. You don't have to go crazy with it, but you can always put it back to stock to pawn it off/Karma to someone else.

[opnly bafld]

Since he is wanting to use a low-end passive subwoofer, exact matching shouldn't be at the top of the list.

     

Fortunately the OP hasn't been back for a couple of days, hopefully he just paralleled the sub inputs and is happy with the results.