dumb question - rears OK, but now no fronts??

[ehummelman]

I just hooked up the rear 6x9s and now the front 6.5s don't work. The Alpine manual said that the HU (9813) has a 3way and 2way mode and that you can't use the fader on 3way. I thought that migt be it, so I switched it to 2 way. I can now fade all the way to the front and hear it but it is so soft there is clearly something wrong. The rears BTW are fine.

Alpine HU with RCAS to the amp front and rear channels. It's an Eclipse 5 channel, but I haven't hooked the sub up yet.
The fronts are wired through the crossovers that came with the speakers.
The rears are wired directly to the 6x9s.

I'm 99% sure I have the RCAs to the correct places, as well as the speaker wires but I could have gone wrong. The front speakers are brand new and worked fine before I messed with everything to get the rears installed.

Can anyone point out my brain fart? I am not an audio guy by any means obviously.

[rickpaw]

Check the gain for the fronts on the amp. It could be set at minimums.

[ehummelman]

Here's what the settings look like right now (I have no clue where they should be).
https://static1.pt-content.com/images/pt/2012/02/sg3ad2-1.jpg

Where do I set the gain? Also, do I use the amp high pass crossover AND the external crossovers for the fronts? If yes, where do I set the amp frequencies?

The picture is hard to see, but the gains go from 0.2V to 8V with 1V in the middle where I have it now.
The high pass frequencies go from 50-200Hz. My front components are JL C2-650s with range of 59 Hz - 22 KHz ± 3 dB if that helps at all.

[ehummelman]

OK, I read up a little on setting gains at 75% volume, raising the gain until you get distortion. It works great for the rears, but I can't get the fronts anywhere near loud enough still. If I unplug the rears and set the fronts it's a little better, but still not right. Then, when I plug the rears in and adjust the gain on them, the fronts are now so low I can't hear them even on full front fader.
This should narrow things down some, but I'm still clueless. Listening just on the rears is kick ass, but the fronts are still useless. ??
What next?

[rickpaw]

Another thing to check is polarity of the speaker wires at all connections. Pos to pos, neg to neg. I've heard when you switch polarity on speaker terminals, it can make the speaker output really low. Something about changing the impedance.

[67rally]

Just some quick troubleshooting here:

Try switching the RCA cables around so the fronts cables are plugged into the rear, and vice versa. If this produces music to the fronts and not rears, then you know the front speakers are fine and it's either an RCA cable or one of the settings on the amp.

If that does nothing replace the RCA cables to their original places and try switching the speaker wires around as above (fronts to rear output, rears to front output). If hooking the front speaker wire into the rear speaker output produces music to the fronts, then you know your front speaker wire and front speakers are fine. This could indicate bad front speaker terminals or again incorrect settings on the amp.

Don't worry about the gain yet until you get music from all speakers. You can adjust the gain for fine tuning later, but leave it in the middle position for trouble shooting.

There's nothing wrong with using the crossovers in the amp as well as the speaker, it will just give you a steeper crossover point. If you are running a sub, or will be running a sub and your front speakers are rated from 59hz-22k, you should set your crossover above 59hz. I would choose 70 or 80hz. This will prevent any signals lower than 70 or 80 hz from going to the speakers and causing damage. Even though yours are rated at 59hz, you don't want to push it, and the sub will do a much better job of reproducing stuff in the 20-80 range than the mids will. You want to allow for some overlap, so if your front and rear speakers are crossed over to allow music from 80 and up, you want a sub crossed over to allow 100-120 and down (or whatever number you choose).

[67rally]

A couple more thoughts...On the back of the head unit, you want to chose the 2-way mode (F/R Sub W.), and you want the System Switch in the Norm position.

Also check to see if the PWR-IC is switched to off in the Alpine HU setup menu (this should improve sound quality by shutting down in the internal amp in the HU).

Check the back of the head unit to make sure the RCA jacks are plugged all the way in, and try jiggling them to see if you have a loose connection up front. You can also try swapping these cables. If you switch the front to the rear location and vice versa and nothing happens (fronts still dead, rears still play), then you know the RCA jacks on the head unit are fine, and the RCA cables are fine as well.

[ehummelman]

thanks guys. I will try swapping cables around to see what's up. And thanks for the tip on the 2 way and PWR-IC. I do have it on 2 way now and I turned the internal amp on and off with no difference. I will leave it off though.
I'll get this thing cranking one of these days. :)

[ehummelman]

Oh, and I need to check that system switch. I saw it when I flipped to 2 way, but didn't realize what it was for. I am 90% sure it's on NORM, because the PO didn't have an Ai-NET device on there either. The only thing is that I need to see how he rigged up the ipod cable. It might be to the Ai-NET. If I leave that switch on EQ/DIV what is the harm or effect? Does it really matter? The manual just says to leave it on NORM unless you connect a device to Ai-NET, no explanation of what it does.

[ehummelman]

What about the subwoofer RCA inputs? There are 2 coming out of the HU (labeled right and left), and 1 input on the amp (along with an out which I'm guessing is to daisy chain amps?). I think I read that you can use either one of the output RCAs or use a Y cable and that using the Y cable gives you -3 more dB. Yes/No?

Also, should I set the HU subwoofer output to stereo or mono? Obviously this is tied to the choice in my first question, I'm just confused because I thought that bass frequencies this low are all mono?

[dcozzi]

If the fronts are going through the crossovers, is the output of the amp going to the speaker input on the crossover and the crossover output going to the speakers?

Is the fader on the head unit (deck) set all the way to rear?

[67rally]

thanks guys. I will try swapping cables around to see what's up. And thanks for the tip on the 2 way and PWR-IC. I do have it on 2 way now and I turned the internal amp on and off with no difference. I will leave it off though.
I'll get this thing cranking one of these days. :)

Here's another quick trouble shoot. Temporarily try switching the PWR-IC on and run the front speakers off the deck power. You can just disconnect the front speaker wires from the amp, and run a couple lengths of speaker wire from the back of the deck to connect to the wires you just pulled off the amp (so you don't have to pull the front speakers to run new wires to the them).

If the front speakers work this way, then you know the front speakers are still ok, the front crossovers are ok, and the speaker wire running from the amp to the front speakers are ok also.

***edit***

This would also let you know that the fader controls on the head unit are not the issue, as well as ruling out the internal crossover on the head unit (deck).

[67rally]

What about the subwoofer RCA inputs? There are 2 coming out of the HU (labeled right and left), and 1 input on the amp (along with an out which I'm guessing is to daisy chain amps?). I think I read that you can use either one of the output RCAs or use a Y cable and that using the Y cable gives you -3 more dB. Yes/No?

Also, should I set the HU subwoofer output to stereo or mono? Obviously this is tied to the choice in my first question, I'm just confused because I thought that bass frequencies this low are all mono?

I would use a Y cable to connect the RCA to the subwoofer input on the amp. The reason being is that even though the bass will be in mono, the music still has a distinct left and right channel. If you only connected one channel and not the other, you would only send bass signals to the subwoofer from one channel of the head unit. For example, if you just connect the left channel subwoofer output to the amp, and the music track had bass notes being sent to the left and right channels unequally, you would lose the bass note whenever they were only coming from the right channel of the head unit.

Wow, that wasn't easy to type, and I'm not sure I explained it well at all. Imagine drumming on a table with your left and right hands. Take one of them out of the equation and that's what your music could sound like if the music track had a lot of intricate stereo separation.

And then I just read the second half of your question...hmm...I'm assuming if you set the head unit to mono, it will combine the subwoofer signals into one channel, and then you could probably get away with just running one cable to the amp. Sorry, not much help here.

[ehummelman]

If the fronts are going through the crossovers, is the output of the amp going to the speaker input on the crossover and the crossover output going to the speakers?

Is the fader on the head unit (deck) set all the way to rear?

yup, for each side (L&R) amp to crossover inputs, then 2 pairs speakers outs to the woofer and tweeter.

I've played with the fader and it doesn't resolve the problem.

Thanks for the thoughts, though. Something will work.

[ehummelman]

I would use a Y cable to connect the RCA to the subwoofer input on the amp. The reason being is that even though the bass will be in mono, the music still has a distinct left and right channel. If you only connected one channel and not the other, you would only send bass signals to the subwoofer from one channel of the head unit. For example, if you just connect the left channel subwoofer output to the amp, and the music track had bass notes being sent to the left and right channels unequally, you would lose the bass note whenever they were only coming from the right channel of the head unit.

Wow, that wasn't easy to type, and I'm not sure I explained it well at all. Imagine drumming on a table with your left and right hands. Take one of them out of the equation and that's what your music could sound like if the music track had a lot of intricate stereo separation.

And then I just read the second half of your question...hmm...I'm assuming if you set the head unit to mono, it will combine the subwoofer signals into one channel, and then you could probably get away with just running one cable to the amp. Sorry, not much help here.

I know, confusing isn't it? Is it a L&R mono or a stereo signal? I think either way it ends up the same. Once I get the fronts figured out, I'll move on to the sub. I'm going to try setting the head unit to mono and use a y cable into the single sub input on the amp. It's weird, every amp I have looked up has the opposite problem - 2 inputs when most people only have 1 output from the HU. Eclipse for some reason did it differently and since they're not in business I can't call their help line. All in all, I'm much less concerned about the sub hookup, I don't think I could hear a difference between 2 mono signals summed into 1 input versus 1 mono versus stereo into 1 input, yada yada yada. The human ear can't discern most sounds that low anyway. Once I get the fronts working right, I'm pretty damn happy. In fact, the 6x9s in the rear deck can put out a somewhat decent bass note. Nothing that hits you in the chest, but it isn't bad surprisingly.

[67rally]

I know, confusing isn't it? Is it a L&R mono or a stereo signal? I think either way it ends up the same. Once I get the fronts figured out, I'll move on to the sub. I'm going to try setting the head unit to mono and use a y cable into the single sub input on the amp. It's weird, every amp I have looked up has the opposite problem - 2 inputs when most people only have 1 output from the HU. Eclipse for some reason did it differently and since they're not in business I can't call their help line. All in all, I'm much less concerned about the sub hookup, I don't think I could hear a difference between 2 mono signals summed into 1 input versus 1 mono versus stereo into 1 input, yada yada yada. The human ear can't discern most sounds that low anyway. Once I get the fronts working right, I'm pretty damn happy. In fact, the 6x9s in the rear deck can put out a somewhat decent bass note. Nothing that hits you in the chest, but it isn't bad surprisingly.

Yeah, I guess what I was saying is that if you leave it in stereo mode, and only hook one rca wire up to the sub, then you will only be getting a signal from one channel. If the music is mixed in such a way that the lower frequencies are sent out to one channel and not the other (ie when you can actually hear the sound stage travel from left to right or vice versa), you would lose that channels bass notes.

Run it in mono from the head unit to a Y connector and you should be good to go. I'm not sure what the -3db reference was.

[ehummelman]

OK, update on my problem. I hope someone can help confirm my amateur diagnosis.
I made sure that the system switch on the amp was set to NORMAL (not EQ/DIV) and the other switch was set to 2 way (not 3 way). Double checked all RCAs are routed correctly to the amp from the HU. Double checked all speaker wire connections and polarity, etc. Turned off the internal amp, and set all the HU crossovers to 80 (hi, lo, and mid). Set the amp crossovers to THROUGH.

As before I can get great output from the rears, and almost nothing from the fronts. I can swap the front and rear RCAs at the amp between front and rear on the amp and either way only the rear speakers work right. There is only a barely audible sound from the fronts either way.

If I swap the speaker leads from the amp from front to rear, I get good sound from the front speakers now. The rear speakers are giving sound, but it isn't as strong as before (although way better than the fronts were when hooked up the other way.)

I am really confused, but it seems like the amp is only giving me a good rear signal output and the front output is shot. I guess I mean the problem is the front RCAs on the amp, not the speaker outputs.

Does this sound like a reasonable conclusion or did I miss something? If it's the amp, that's fine, I can shop for another one. I just want to know before throw money at the wrong problem.

[67rally]

If you can swap the rca's at the amp and the rears still work and fronts don't, then the HU is fine, the settings on the HU are fine, and so are both RCA cables and RCA connections on the amp.

If you can swap the speaker wires at the amp and you now get sound from the front speakers, then that indicates that one set of speaker terminals on the amp is good, and the other is the problem.

[67rally]

I am really confused, but it seems like the amp is only giving me a good rear signal output and the front output is shot. I guess I mean the problem is the front RCAs on the amp, not the speaker outputs.

Does this sound like a reasonable conclusion or did I miss something? If it's the amp, that's fine, I can shop for another one. I just want to know before throw money at the wrong problem.

Your first conclusion is right, the amp is only giving a good rear speaker output, and the front speaker output is shot.

The second half of your conclusion was wrong. The RCA's are the input. When you swapped RCA's and the sound still came out of the rear speakers and not the front speakers, what you did is take the front channel from the HU and sent it to the rear speakers. The rear speakers are playing the front channel in this setup. This means that you have a good signal from both sets of RCA's, but one of the signals is getting lost either inside the amp or at the speaker terminal. If it's not the speaker terminal, then the only other option would be an incorrect setting on the amp for the front speakers, and it sounds like you ruled that out by setting all x-overs to through.

[ehummelman]

OK, thanks. So either way I guess my amp is toast. At least for the front channels. Maybe I can find someone to repair it on one of the audio forums. Thanks a bunch for the help though, it's always nice having someone walk you through the first time.

[67rally]

OK, thanks. So either way I guess my amp is toast. At least for the front channels. Maybe I can find someone to repair it on one of the audio forums. Thanks a bunch for the help though, it's always nice having someone walk you through the first time.

No problem. It could be a loose/corroded terminal. Since you are getting some sound, there is hope. Maybe you can find someone to fix it.

[ehummelman]

Yeah, it's weird. This morning I swear it sounded a little better, but still the fronts are like 25% as loud as the rears. I might take it to the stereo shop here and see what they think. I just don't want to take their time and not buy anything from them, while at the same time don't want them to try to sell me a new amp.