Question About Sub Setup...

mitchell allard

Active Member
Oct 30, 2015
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Apollo beach
OK so I just installed 10 inch cvx Kicker sub in sealed box and a 500watt rms at 4ohm amp. And it's all wired correctly except the line in converter tapping into the two rear speakers.

OK so here's the deal. The line in converter is split into both the rear speakers. The sub plays fine if either of the right or left rca cables is in but if both rca cables are in the bass drops to basically nothing. Now idk why this is. Maybe it's because it's a mono amp and one sub so it only needs one rca. I don't know if I should just leave it with one plugged in or if I should maybe do a y converter and see if that makes a difference. It sounds good with the one rca it just doesn't look right.
 
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Sounds like a phasing problem to me. I'm not sure what the wiring from the stock speakers to the line converter looks like, but I imagine there is a +/- wire you are tapping into. If they are swapped on one side, you now have 2 audio signals where one is 180deg out of phase with the other, when this happens, it cancels out the audio signal. Since low frequencies don't benefit a whole lot from panning, that's why it sounds like it completely drops out.

This picture helps show that (the yellow combined wav is your resulting signal):
PhaseCancellation.jpg


If the signal was in-phase, wave 2 would lie directly over top of wave 1, resulting in a combined wav that follows the same shape just with greater values on the peaks of the curve since it is the result of combined waves.
 
The speakers themselves are probably wired fine, it may be how you are tapping into them that is cross crossed...basically the lines from the speaker to the line converter. Again it is just an assumption.

Edit: the easy way to find out if its phasing, have both RCAs plugged up and go into head unit and pan the stereo either all the way to left or right. You should hear the sub comeback if it's phasing since one of the audio signals won't be there to fight against the other.
 
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The speakers themselves are probably wired fine, it may be how you are tapping into them that is cross crossed...basically the lines from the speaker to the line converter. Again it is just an assumption.


Edit: the easy way to find out if its phasing, have both RCAs plugged up and go into head unit and pan the stereo either all the way to left or right. You should hear the sub comeback if it's phasing since one of the audio signals won't be there to fight against the other.

Hmm I'll have to try that cause it makes sense. Cause either of the rca can be plugged in but when both are they cut each other out.
 
You'll be fine if you leave only one plugged in. I would suggest the left one (white). Make sure you tape off the red one if you end up leaving it disconnected. With it being MONO you really don't need Left and right signal.
 
You'll be fine if you leave only one plugged in. I would suggest the left one (white). Make sure you tape off the red one if you end up leaving it disconnected. With it being MONO you really don't need Left and right signal.
I connected them both tried to change balance both ways it sounded fine but for some reason it gets louder when only one input is in I really don't need louder I just didn't understand why this was occuring
 
But I feel like on certain songs it's missing certain notes and I think that's because both aren't plugged in cause some songs will play bass through one side and not the other for certain parts so that the bass kinda switches sides which is why I think it was missing these notes
 
Maybe it's just me but wouldn't you be better off to tap into the wires feeding the door subs to get better low end frequencies to the amp?? I am planning to add a sub and that's what the stereo shops I have talked with say to do.