[mitko1994]

I have a Logitech X-540 PC audio system. However there's some sort of a problem with the built-in amp so I can't use the system anymore. Currently I went to a 2.0 setup with 2 bookshelf speakers and an external amp. Is there a way to reuse the subwoofer as a subwoofer only (not as the amp for the entire system)? I tried running a 3.5 mm cable from the center/sub output on my sound card to the center/sub input on the sub but no luck? Perhaps it has to do with settings on the PC as well but I'm not sure. Does anyone know if this can be done?
 
Thanks

 

[ProtegeManiac]

  I have a Logitech X-540 PC audio system. However there's some sort of a problem with the built-in amp so I can't use the system anymore. Currently I went to a 2.0 setup with 2 bookshelf speakers and an external amp. Is there a way to reuse the subwoofer as a subwoofer only (not as the amp for the entire system)? I tried running a 3.5 mm cable from the center/sub output on my sound card to the center/sub input on the sub but no luck? Perhaps it has to do with settings on the PC as well but I'm not sure. Does anyone know if this can be done?

 
If there' a problem with the amp on an active speaker then how can it amplify the signal coming from the PC to move that subwoofer?

 

[mitko1994]

The problem is weird. The sound fades away and comes back on its own. I tried using my ipod as the audio source and the result is the same so I assume it's a problem with the built-in circuitry (I call it amp because I'm not really sure what to call it). However the speakers and the sub still play well when the sound is amplified properly. There's more on the problem here:

 

[ProtegeManiac]

  The problem is weird. The sound fades away and comes back on its own. I tried using my ipod as the audio source and the result is the same so I assume it's a problem with the built-in circuitry (I call it amp because I'm not really sure what to call it).

 

It's the amp. That's why you can hook it up to a line level source.
 

  However the speakers and the sub still play well when the sound is amplified properly.

 

I'm not sure what you mean, you're having these problems. They are not being "amplified properly."

 

If you mean "otherwise normal when these symptoms aren't happening," that still doesn't eliminate the built in amp being the problem.
 

  There's more on the problem here:

 

If you've used different cables and got the same problem, it might be the potentiometer. But unless you can diagnose that yourself or know someone who can diagnose and at least clean up the pot for a six pack and some pizza, you might as well buy new speakers.

 

[mitko1994]

Thanks for your reply. Yes I've tried different 3.5mm cables. The result is the same. When the symptoms aren't there the speakers and sub sound great so I know the problem is not with the speakers nor the sub(as a sub) itself. However that still doesn't answer my question. Since the sub itself is functioning perfectly well, is it possible to use the sub as a sub only and hook it up to my sound card through the center/sub ports(or in some other way) so that I only use the sub as a sub and not an amp for an entire system? I currently have a small 20W/per channel 2-channel amp hooked up to some old JVC speakers. Can I make that a 2.1 system by adding the sub?

 

[ProtegeManiac]

  Thanks for your reply. Yes I've tried different 3.5mm cables. The result is the same. When the symptoms aren't there the speakers and sub sound great so I know the problem is not with the speakers nor the sub(as a sub) itself. However that still doesn't answer my question. Since the sub itself is functioning perfectly well, is it possible to use the sub as a sub only and hook it up to my sound card through the center/sub ports(or in some other way) so that I only use the sub as a sub and not an amp for an entire system? I currently have a small 20W/per channel 2-channel amp hooked up to some old JVC speakers. Can I make that a 2.1 system by adding the sub?

 
Well you basically kind of clarified my question and then I'm lost again. So sometimes the sub and satellites work well. How do you know the sub is functioning perfectly well? When the problem kicks in, only the satellites are affected, but sub output is normal?

If that's the case then all you need to do is run a parallel signal from your source. If you're using your computer then just run a cable from the subwoofer output you've been using to the sub, then run a cable from the FL+FR output to the "smal 20w/per channel 2-channel amp."

 

[mitko1994]

So sometimes the sub and satellites work well. How do you know the sub is functioning perfectly well? When the problem kicks in, only the satellites are affected, but sub output is normal?

   When the problem occurs everything is lowered in sound. I believe it's functioning perfectly well because when the sound is amplified as it should be and all speakers are playing as loud as they   should be, the sound is clear so there is nothing wrong with actual speakers nor the sub itself.

 If that's the case then all you need to do is run a parallel signal from your source. If you're using your computer then just run a cable from the subwoofer output you've been using to the sub, then run a cable from the FL+FR output to the "smal 20w/per channel 2-channel amp."

My amp is very basic - it's a 12V unit that only has 4 wire clips and 3.5mm port for the audio source. That's why I was hoping I could reuse the sub through the built-in amp - I can live with the base fading away from time to time but having all the sound fade is driving me crazy. I tried running a 3.5mm wire from the sub out on the sound card to the sub/center in on subwoofer but when I powered it, it wasn't working. I tried setting my speaker configuration to 5.1 in windows but when the sub test ran it barely vibrated. Since this is a 5.1 system it may be design such that it needs the front speaker mono cable plugged in.

 

[mitko1994]

I just tried plugging in the front speakers mono together with the sub/center mono and now the sub is actually playing as expected. I guess I need to have a mono running to the sub as well. With that said, would it be possible to use a 3.5mm headphone splitter on my sound card front speaker output so I can run 2 lines - 1 for my external amp and the other for the sub?

 

[ProtegeManiac]

  I just tried plugging in the front speakers mono together with the sub/center mono and now the sub is actually playing as expected.

 
I can't understand how you did that. Did you use a spltter and split the signal into four?
 

  I guess I need to have a mono running to the sub as well. With that said, would it be possible to use a 3.5mm headphone splitter on my sound card front speaker output so I can run 2 lines - 1 for my external amp and the other for the sub?

 
Why are you using the front "speaker" output for the sub? You have a sub-center combo output, just use one stereo cable there.(and just to be clear this is the green 3.5mm socket in the back, not the "front headphone jack" literally at the front of the PC case?)

 

[mitko1994]

The back of the sub has the usual 3, 3.5mm ports for 5.1 audio which are "Front", "Rear" and "Center/Sub". It also has a single RCA port where each of the speakers plug into. I did not use a splitter, in fact I don't have one, otherwise I wouldn't have asked - I would've just tried it myself.
 
Here's what I did(using only ports on the sound card):
 
1. At first, I had the "Front" output on my sound card connected to my external amp and I wanted to add the sub to get a 2.1 system. I connected the sub using a mono(3.5mm) cable to the "Center/sub" output on the sound card(That was the only connection). That alone was not enough to "power" the sub. When I ran the windows 5.1 sound test, the sub barely vibrated.
 
2. I disconnected my external amp and instead tried running the "Front speaker" line into the sub. That's when the sub was "powered" properly and it was playing normally. I t was just the sub( no speakers connected to it) but I had to run 2 lines into it, 1 for the Front speakers, and the other for the "Center sub".
 
Conclusion: This lead me to think that the built-in amp in the sub works in such a way that it needs to have the "Front" port connected no matter what.
 
Now my question is, can I use a splitter for my sound card "Front" speaker output so that I can run 2 lines from it - 1 for the external amp, and the other for the sub?
 
Thanks

 

[ProtegeManiac]

  The back of the sub has the usual 3, 3.5mm ports for 5.1 audio which are "Front", "Rear" and "Center/Sub". It also has a single RCA port where each of the speakers plug into. I did not use a splitter, in fact I don't have one, otherwise I wouldn't have asked - I would've just tried it myself.

 
I was asking about the splitter because I can't understand how exactly you wired four channels into mono.
 
 

  Here's what I did(using only ports on the sound card):
 
1. At first, I had the "Front" output on my sound card connected to my external amp and I wanted to add the sub to get a 2.1 system. I connected the sub using a mono(3.5mm) cable to the "Center/sub" output on the sound card(That was the only connection). That alone was not enough to "power" the sub. When I ran the windows 5.1 sound test, the sub barely vibrated.

 

OK, first off, the signal from the sound card does not power the sub. That is only a line signal. What powers the subwoofer is the amplifier built into the cabinet of the subwoofer. Pick it up and look at it - see the power cord? That power cord supplies electricity to the amplifier built into the subwoofer, and in a multimedia speaker like that, it also has the amplifier for all the other channels.

 

Second, if it wasn't producing any sound via the Windows sound test, how are you sure that this time the amp on the sub was otherwise working properly? Maybe it was having the symptoms again. Or maybe your soundcard is the one with a problem. Or both of them. Or heck, maybe the 5.1 sound test doesn't have loud bass. This part of the test basically did not pin point where the problem might actually be.

 

 
2. I disconnected my external amp and instead tried running the "Front speaker" line into the sub. That's when the sub was "powered" properly and it was playing normally. I t was just the sub( no speakers connected to it) but I had to run 2 lines into it, 1 for the Front speakers, and the other for the "Center sub".
 
Conclusion: This lead me to think that the built-in amp in the sub works in such a way that it needs to have the "Front" port connected no matter what.

 
My conclusion here is that the sub output on your soundcard might be busted.
 
Or...was there any signal coming out of the Center? You should have hooked that up. If there was no sound coming out of the center either that isn't automatically a problem with the amp built into the Logitech speakers but could be a matter of soundcard settings, ie, if it's set to output stereo (note if manually set as such it will downmix 5.1 signals into 2.0) then there really will be nothing coming out of the Center and Sub.
 

  Now my question is, can I use a splitter for my sound card "Front" speaker output so that I can run 2 lines from it - 1 for the external amp, and the other for the sub?

 
You can. Not the best way to do it since you lose sub output control in case the soundcard has that, but it's doable. If at least to eliminate what the problem is since the splitters are cheap.

 

[mitko1994]

Yes I know it doesn't power it - that's why I put it in quotes. I used that for a lack of a better word. I just tried running the sub/center line only from the sound card to the sub and powered it up. I also plugged in the center speaker and there's no sound output. If I plug-in the "front" line into the sub they both play. I'm sure it's not having the symptoms because I had set to almost full volume which would've deafened me if it was amplified properly. It's definitely a problem with the built-in amp because when sound fades it fades away for all speakers not just some of them - as I said it before I tried a different audio source (Ipod) and it still had the same symptoms. I don't know about the center/sub output on the sound card - you may be right. I tried running just the "front" line to the sub and that worked so perhaps I was never getting true center/sub signal all this time. What makes me think that the output is not broken however is the fact that during the sound test, the sub still vibrates slightly which means that there is signal fed to it - perhaps it's some sort of a setting but I can't find anything about it online(my sound card is labeled as "SoundMAX Integrated Digital HD Audio" under device manager).