[ArnasK]

Hello,
I ordered stereo amp (for speakers) which has a volume controlled 3.5mm stereo out.
I would like to connect to this port a powered subwoofer, which has two RCA inputs (L/LFE and R), but I do not want to run two cables to connect. Can I use '3.5mm stereo to RCA mono combined adapter' like shown in a picture, and run one RCA cable to sub's L/LFE port? Is it safe? Isn't the combined signal too strong for the subwoofer? Thanks.

 

[Roseval]

Why don't you simply run a TRS cable to the sub and use a short female 3.5 to 2x RCA at the sub?

 

[megabigeye]

Hello,
I ordered stereo amp (for speakers) which has a volume controlled 3.5mm stereo out.
I would like to connect to this port a powered subwoofer, which has two RCA inputs (L/LFE and R), but I do not want to run two cables to connect. Can I use '3.5mm stereo to RCA mono combined adapter' like shown in a picture, and run one RCA cable to sub's L/LFE port? Is it safe? Isn't the combined signal too strong for the subwoofer? Thanks.

I wouldn't use an adapter like this unless you know how it's wired. If it's truly stereo-to-mono, I'd think it could cause a short in your amp. If you have access to a multimeter, you can test it by putting the multimeter in continuity mode, inserting one probe into the RCA outlet, and using the other to touch the tip, ring, and sleeve, noting when it beeps. If it beeps ONLY on tip OR sleeve, it's safe to use; if it beeps for more than one, then it's not safe

If you don't have a way to test it, you could/should use an adapter like this:

with an RCA cable connected to the red.

Or do as @Roseval suggests and use an adapter like this:

with a TRS-TRS cable.

 

[ArnasK]

Thanks for your replies. I don't have the adapter I mentioned, just planned to buy it, but now I won't.
I have this adapter you showed:

But if I use only red socket, does it mean that I will have the bass only from one channel?
Thanks.

 

[Roseval]

But if I use only red socket, does it mean that I will have the bass only from one channel?

Of course.

 

[megabigeye]

Thanks for your replies. I don't have the adapter I mentioned, just planned to buy it, but now I won't.
I have this adapter you showed:

But if I use only red socket, does it mean that I will have the bass only from one channel?
Thanks.

Yes, but bass is almost always a mono signal, which is why you can use one subwoofer.

 

[ArnasK]

Understood, thanks. I will connect it this way, since I have this adapter and RCA cable.

 

[tomb]

Yes, but bass is almost always a mono signal, which is why you can use one subwoofer.

Actually, ... that's because the device (amp, receiver, PC, TV, whatever has the subwoofer output) has electrically combined the stereo signals into a mono signal for the subwoofer output. The subwoofer then takes that combined L+R signal and usually uses a cutoff filter above the bass frequencies.

Subwoofers usually work because the human ear has difficulty discriminating direction with lower frequencies. It doesn't mean that those frequencies are non-directional in live performances or in the recording. You may hear them from the center if coming from either channel, but it doesn't mean the microphone(s) have recorded them that way. Subwoofers also will not "work" if there isn't a stereo signal surrounding one. If you place a subwoofer at the back of a room and the left and right channels for stereo at the front of the room, you're not going to like the sound.

Other than a subwoofer output, stereo-to-mono adapters are quite common, but they include a 1K resistor on each non-grounded channel output (Left and Right) to prevent the shorts mentioned above. That's what is internal to devices that have a mono subwoofer output, not because the bass signals are actually mono in the recording.

I'm pretty sure if a stereo signal is fed to a subwoofer input from just one channel - it's going to miss the musical bass notes that are in the other channel.