unequal or no output from dual subs

[camperjoe]

Using a Y adapter for my single sub out on a Pioneer VSX-515 I get either very low or no output from second sub. Either sub works fine with or with out the Y dapter in place by itself but 2 subs just isn't working. Any suggestions as to why this is happening?
The subs are Small Yamaha subs, YST-W015 I think is the model ID. Any input would be appreciated.

 

[Exit]

I think you have a certain level output from the subwoofer output connection and when you split it, the signal is lowered and the volume is decreased. If just one subwoofer is low then I would turn up the volume on that subwoofer. If both subwoofers are low output, I would turn up the subwoofer output through the receiver controls. The volume control is often automatically set through the auto set up calibration but you can go through the settings manually and raise the subwoofer volume.

 

[GlocksRock]

You could be experiencing cancellation of the waves, try adjusting the phase on one of the subs and see if it makes a difference.

 

[camperjoe]

"I think you have a certain level output from the subwoofer output connection and when you split it, the signal is lowered and the volume is decreased..."

Thanks so much for the quick reply. When calibrating the speakers using the tone generated by the reciever I set the sub woofer volume at +9.5 in order to get a reading of 75 on the SPL meter at the prime seating position. There's only .5db left to boost but I will double check my settings and see if there's any change.

 

[camperjoe]

You could be experiencing cancellation of the waves, try adjusting the phase on one of the subs and see if it makes a difference.

Thanks for your quick reply though in this case I'm not sure this is what's happening and I'll explain why. Last night while recalibrating the spkr set up due to some room rearranging I could get a sound reading from only the left sub, nothing from right side sub. I turned off left side sub and right side sub was still unresponsive. It was late and I did pull the shelf unit away from the wall to mess with wiring but past experience has shown me that if only one sub is connected to the reciever's sub ouptput with or w/o Y splitter either will work. Hook up both via the splitter and only one will work.
The set up is this:
1. Pioneer VSX-515 w/ one RCA sub output
2. Two Yamaha YST-W015 subs with L/R inputs, L is also denoted as mono input
3. X over is set to 80 in reciever
4. using a 'found it in the junk drawer' Y spiltter to connect to sub's L(mono) input. Note that with splitter in place I can disconnect either sub and the other will work
5. volume on both subs is set to 12:00 position. Range is from 7:00 - 5:00
6. Sub phase set to in phase.
7. Sub output in reciever is set +9.5 in order to achive 75db reading on SPL meter at seating position when main volume is set at -25db.
8. One sub is connected via 15' cable the other via 25' cable.

I'm thinking of replacing splitter with better one with gold plated connectors and sub cabling with shorter lenghts now that both subs are up front 6'-8' should do it. But I'm just shooting in the dark with no real idea why this set up is not working as it seems to for many posters on this forum.

Any additional input/feedback would be appreciated.

 

[Exit]

"I think you have a certain level output from the subwoofer output connection and when you split it, the signal is lowered and the volume is decreased..."

Thanks so much for the quick reply. When calibrating the speakers using the tone generated by the reciever I set the sub woofer volume at +9.5 in order to get a reading of 75 on the SPL meter at the prime seating position. There's only .5db left to boost but I will double check my settings and see if there's any change.

If you are at the limits of your volume control, then maybe you are getting phase cancellation as suggested. My search function is not working today but I was trying to find "crawliing for bass" writeup for positioning the first sub, then some articles on "dual subs setup" to help you out. Before you start moving things around you might try changing the phase control on one of the subwoofers. If bass output increases, then you are on your way. If not then you can dig deeper and see if you find a technique that helps you. I know I have limited options for speaker placement so I didn't really follow the setup articles myself. But I only have one subwoofer to set up.

 

[Exit]

Here is one article on multi subwoofers which you might have noticed:

http://forums.audioholics.com/forums/showthread.php?t=40242

 

[Exit]

Here is another page of subwoofer setup references.

http://www.audioholics.com/tweaks/get-good-bass/

 

[camperjoe]

Thanks so much...

...for being willing to help a movie buff on a buget kinda guy. I have looked at the suggested reading material via the links provided and it's all good.
Now the happy news, both subs are working and I have even been able to reduce the bass output at the reciever somewhat. How? Almost embarassed to say, I junked the Best Buy house brand sub cable and Y adapter and replaced them with what are apparently better quality products. Presto, just like that, everything is as I had hoped when I first began this experiment bass is not boomy, to my old ears it sounds richer more enveloping
Now back to going through the movie library to hear what rocks as never before.

Gratefully