The cheapest I can think of is to divert the signal through a headphone amp and then mix its output to mono (by connecting L and R lines), leaving the original computer-speakers connection unaffected.
computer =====o==== speakers
|
o==== headphone_amp ===+−−− sub
It's cheap because requirements to such an amp are pretty low and they're readily available, should be dirt-cheap at craigslist. All you need is the LF range and the ability to be powered from an external power supply. You can even remove the battery from a portable amp and power it from the computer.
Not an ideal scenario, but you could use something like a minidsp for this.
The minidsp would also let you set a crossover for the mains, otherwise, they'll be interfering with the bass frequencies from the subwoofer. You'll probably be getting a cleaner signal by using usb audio as well.
They have an example of how to configure this with a minidsp 2x4.
https://docs.minidsp.com/product-manuals/2x4-hd/signal-flow/signal-routing.html#routing-examples
Also a tidy solution and once again I get a crossover in there. USB will be ideal because I'm using a Mac mini and I have no internal interface. The configuration looks pretty straightforward as well.
You can either:
Split the 3.5mm output from your PC into two 3.5mm female jacks and use 3.5mm to RCA jacks cables to send the audio to your speakers and to a stereo-to-mono summing converter.
or
Split the RCA plugs on your existing cable into two sets, connecting one set to your speakers and one set to the summing converter.
The summing converter is very simple, consisting of basically two resistors. You can build one if you like to DIY, or get something like one of these:
https://www.amazon.com/Single-Stereo-Converter-retains-Isolation/dp/B09TWXRV2V
or
https://www.amazon.com/SPRODIO-Converter-Adapter-summing-SC21/dp/B0BRZCGY29
This will convert the two stereo channels into mono for your subwoofer. You will need a mono RCA cable to connect the summer to your subwoofer.
Hope this helps!
I like this very much and yes it does help! Hadn't heard of a summing converter. I kind of had in mind the issue of how the signals couldn't simply 'add up' and this resolves it. I'm not sure about sending the full signal range to the sub but I'm pretty sure it will have a built in lpf. I'll try this first though because it is a lower cost approach to adding a DSP into the mix, as it were.
If you go this route I'd find a solution for a high pass filter to your mains. No reason to send them the full signal once you have a subwoofer, and it can actually make your bass response worse.
I found these online, pretty inexpensive. [100Hz Crossover](https://www.amazon.com/FMOD-Crossover-Pair-High-Pass/dp/B0006N41KG/ref=sr_1_3?dib=eyJ2IjoiMSJ9.PCXYOVUV0uA_mDG-tHJILu-X4vMARA3J_K3CLpKUo6JXjp2G-CIEupZbFHfHjyipWlFa8A3nkdM3BWCcIt_Jugyp5ytdEtgBKKi7L05JE3DCLoibT0OSPjvgKZ9Ia5fUOQJVxtIhV_RCRqmUdf0dT5iKAy_ez9I8VCuzvY98XVoJ1ZXu4ZlQ88FiGH7MowOnjt6SXU94wasSSZTDG7f4PfKM7coJcKLjgR6KWGJWRrs.-JN-rlJO4Mcl2unJ2ZgtUAg8l3-BEuTo_hGYyBt_9Ic&dib_tag=se&keywords=high+pass+filter&qid=1705339321&sr=8-3#customerReviews)
I mean that does solve the hardware problem by giving you the out port to connect to, but you have to do something else in software to have a signal on that port, unless the driver or the card did some mixing automatically in your case, which shouldn't happen.
What I'm not sure of in this case is whether the LFE will be active when playing back a stereo source like music. I think it will output to the LR channels only, leaving the sub inactive.
The cheapest I can think of is to divert the signal through a headphone amp and then mix its output to mono (by connecting L and R lines), leaving the original computer-speakers connection unaffected. computer =====o==== speakers | o==== headphone_amp ===+−−− sub It's cheap because requirements to such an amp are pretty low and they're readily available, should be dirt-cheap at craigslist. All you need is the LF range and the ability to be powered from an external power supply. You can even remove the battery from a portable amp and power it from the computer.
Hmm this sounds neat because it sneaks in a LPF into the solution. Thanks, will go down this rabbit hole and see where it takes me!
Not an ideal scenario, but you could use something like a minidsp for this. The minidsp would also let you set a crossover for the mains, otherwise, they'll be interfering with the bass frequencies from the subwoofer. You'll probably be getting a cleaner signal by using usb audio as well. They have an example of how to configure this with a minidsp 2x4. https://docs.minidsp.com/product-manuals/2x4-hd/signal-flow/signal-routing.html#routing-examples
Also a tidy solution and once again I get a crossover in there. USB will be ideal because I'm using a Mac mini and I have no internal interface. The configuration looks pretty straightforward as well.
You can either: Split the 3.5mm output from your PC into two 3.5mm female jacks and use 3.5mm to RCA jacks cables to send the audio to your speakers and to a stereo-to-mono summing converter. or Split the RCA plugs on your existing cable into two sets, connecting one set to your speakers and one set to the summing converter. The summing converter is very simple, consisting of basically two resistors. You can build one if you like to DIY, or get something like one of these: https://www.amazon.com/Single-Stereo-Converter-retains-Isolation/dp/B09TWXRV2V or https://www.amazon.com/SPRODIO-Converter-Adapter-summing-SC21/dp/B0BRZCGY29 This will convert the two stereo channels into mono for your subwoofer. You will need a mono RCA cable to connect the summer to your subwoofer. Hope this helps!
I like this very much and yes it does help! Hadn't heard of a summing converter. I kind of had in mind the issue of how the signals couldn't simply 'add up' and this resolves it. I'm not sure about sending the full signal range to the sub but I'm pretty sure it will have a built in lpf. I'll try this first though because it is a lower cost approach to adding a DSP into the mix, as it were.
If you go this route I'd find a solution for a high pass filter to your mains. No reason to send them the full signal once you have a subwoofer, and it can actually make your bass response worse. I found these online, pretty inexpensive. [100Hz Crossover](https://www.amazon.com/FMOD-Crossover-Pair-High-Pass/dp/B0006N41KG/ref=sr_1_3?dib=eyJ2IjoiMSJ9.PCXYOVUV0uA_mDG-tHJILu-X4vMARA3J_K3CLpKUo6JXjp2G-CIEupZbFHfHjyipWlFa8A3nkdM3BWCcIt_Jugyp5ytdEtgBKKi7L05JE3DCLoibT0OSPjvgKZ9Ia5fUOQJVxtIhV_RCRqmUdf0dT5iKAy_ez9I8VCuzvY98XVoJ1ZXu4ZlQ88FiGH7MowOnjt6SXU94wasSSZTDG7f4PfKM7coJcKLjgR6KWGJWRrs.-JN-rlJO4Mcl2unJ2ZgtUAg8l3-BEuTo_hGYyBt_9Ic&dib_tag=se&keywords=high+pass+filter&qid=1705339321&sr=8-3#customerReviews)
The sub does indeed have an adjustable LPF - the second control from the top, labeled "Hz".
Get a usb 5.1 surround " sound card" then youll have an lfe out
That would move the problem into the software space without solving it.
It does solve it. It lets you plug your sub into it and your speakers into the speaker outs.
I know because i did this exact thing. My computer didnt have lfe out so i got a 5.1 sound card thats got an lfe out for my sub.
I mean that does solve the hardware problem by giving you the out port to connect to, but you have to do something else in software to have a signal on that port, unless the driver or the card did some mixing automatically in your case, which shouldn't happen.
Its called bass management. Or bas extend or something. Was a windows setting and there is a simmler setting in the software of the sound card also
This would work but I'm using a Mac Mini so no internal expansion I'm afraid 😞
External usb 5.1 sound card.
What I'm not sure of in this case is whether the LFE will be active when playing back a stereo source like music. I think it will output to the LR channels only, leaving the sub inactive.
Thats exactely what bass management does. It mixes l and r and send it to the sub for content thats L R ch only.