Tricky Problem: Speakers shutdown when sub volume gets turned up 80%

[silenkiller 10+ year member]

So, I just installed an amp and two ssds. Anyway, I've noticed that when I turn the volume up to around 85% that my front comps stop playing. Now it works fine when the sub isn't on. The speakers are fine. The sub seems to play independently fine. When the speakers are off, I checked and both amps are still on so it isn't the remote. At this point I can only assume that maybe something is happening in the headunit? Are there cases where they break in a way that they start losing power out to the RCA's?

Anyone have experience with this? When the system is playing and the speakers are dead, if I unplug the RCA's from the amp the speakers will come back on. So that is what is making me believe that the headunit is failing at supplying voltage to both set of RCA's. Any suggestions?

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[silenkiller 10+ year member]

Hm. I'm going to snag some RCA's and use the RCA out from one of my amps to the other and see if it still shuts off .Then I'll know if its the headunit or not.

 

[CHEMMINS 10+ year member]

Shutdown protection from clipping?

 

[silenkiller 10+ year member]

Shutdown protection from clipping?

See I initially thought maybe that as well. But the speakers play fine without the subs at that volume on their own. It's only when the subs are also plugged in that it kills the speakers around 85%. Oh oh I have an idea. I should try swapping the rcas and see if the sub dies instead of the speakers hah brb

 

[silenkiller 10+ year member]

Okay so I swapped my comp rcas and my sub rcas, cranked it up and lo and behold the speakers still cut out at around 85% with the subs still plaiyng. How the hell does that make any sense? That can only mean that the RCA signal isn't being interrupted. So what in the world is going on.

 

[CHEMMINS 10+ year member]

What amp is it and how are the mids/subs wired?

 

[silenkiller 10+ year member]

Well its a Memphis MOJO2000D that I got off of CACO. I have the subs wired in series/parallel down to a 2 ohm load. The amp is is 2,000 rms @ 2 ohms. Ohm meter shows 1.7 ohms at the terminals but I'd imagine this isn't the problem. The comps are a 3 way setup off a jl 300/2 off passive xovers. The comps have never given me problems until I just installed the amp and sub.

I just sat there, turned it up to 85 %. When it cut out, I unplugged an RCA off the memphis. The subs level went down and bam, the speakers started playing again. I unplugged the other one, switched the right and left, plugged in them both and bam, speakers out. Then I unplugged one again and turned it up more to compensate and once again the speakers went out, so it doesn't seem to be specific to the right or left channel. It seems like if I go over an exact amount of volume with the subs the speakers cut out. I also tried turning the gain way down/up in different configs on the memphis and everytime once the subs got to a certain volume the speakers cut out. I also tried holding the JL amp up in the air for vibration issues and it still cut out. No distress lights on either amp are showing. This is pretty mind boggling.

Edit: Hm at this point I'm wondering if there is something loose somewhere that is rattling from the subs and shorting maybe? I guess a mission behind the headunit is in order.

 

[CHEMMINS 10+ year member]

Do you have 1 set of rcs'a going from deck to jl amp and 1 set of rcs's going from deck to mojo?

 

[mbrooky 10+ year member]

have you tried only going 70% on the HU and turn gains up on the amp?

 

[SPLaudio 5,000+ posts]

my guess is too much input voltage into the amp...

 

[silenkiller 10+ year member]

Do you have 1 set of rcs'a going from deck to jl amp and 1 set of rcs's going from deck to mojo?

Yeah, I have the front set from the headunit to the JL, and the subwoofer set to the mojo.

Okay new info: I hooked up my volt meter and put it on the speaker output on the JL AMP. While the speakers are playing i can see the fluctuating voltage. As soon as I turn it up, the voltage goes to almost to zero while the subs are still playing. So something is causing the JL Amp to stop when the subs are hitting hard. Can you measure RCA voltage by just touching the middle prong and the outside of the rca? Gonna see if the RCA voltage is dropping.

 

[silenkiller 10+ year member]

have you tried only going 70% on the HU and turn gains up on the amp?

Yeah it still dies once the subs get to a certain loudness.

 

[CHEMMINS 10+ year member]

Yes you can check RCA's like that.

 

[silenkiller 10+ year member]

Yes you can check RCA's like that.

Hm can't seem to get a good reading off the RCA's. That should be DC voltage right? Maybe I'm not putting the leads in the right place.

 

[CHEMMINS 10+ year member]

AC for RCA's....and try to play a low tone like 60hz or so. AC will flux a lot while music is playing. A steady tone will give more of a stable reading. If you play on music and it fluxes till the subs get loud then stops, its in the HU