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2015 RDS Manual
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Discussion Starter #1 (Edited)
So I went to tweeter to get my amp installed (the discontinued Alpine MRV-F340) I took forever and the guy took off without telling me he finished the job (As long as a product is finished well I don't really care). So the thing is this amp powers my compnents in the front and the speakers in the rear, but now I don't think the sub is working in the back. I lost a lot of bass... is this normal when adding an amp in our cars?

The speakers do sound better powered by the amp. Oh yeah and I'm going to install all my JL speakers myself... Tweeter charges ridiculous prices (I don't like installing electronics in cars myself that's why I had someone else do it and they were the only ones that weren't booked till March 5th!)
 

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hmm... i'm not familiar with how the factory sub works in these cars, i'm assuming it's powered by the head unit and homeboy at the stereo shop didn't know how to deal with it... I'd say go back and complain if it's at a "real" shop, make 'em fix it at NO additional cost to you.

But first, go in back or wherever the sub is and listen with your ear physically close for it while there's some loud music on to be absolutely sure it's not working..... it might just be that it's out of phase with the rest of your speakers or worse yet all of your speakers could be out of phase with each other (if the guy hooking it up is retarded)
 

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#8 Post ho
1999 Subaru Forester
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If you changed out the headunit I'm pretty sure... that subaru subs are only compatable with the "subaru" factory headunit

But you only mentioned an amp.. so if you really want to know, I'd go there and just talk to the guy for awhile, usually whenever I get work done on my car I try to get a solid idea of whats goiing on :)
 

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Discussion Starter #4
apanthropy said:
hmm... i'm not familiar with how the factory sub works in these cars, i'm assuming it's powered by the head unit and homeboy at the stereo shop didn't know how to deal with it... I'd say go back and complain if it's at a "real" shop, make 'em fix it at NO additional cost to you.

But first, go in back or wherever the sub is and listen with your ear physically close for it while there's some loud music on to be absolutely sure it's not working..... it might just be that it's out of phase with the rest of your speakers or worse yet all of your speakers could be out of phase with each other (if the guy hooking it up is retarded)
yeah I went to the trunk and I can hear it popping
 

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Premium Member
98 Forester...what else
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Umm...IIRC, you had him install a 4 channel amp.

The sub works as a "fifth" channel, so it's probably still hooked up to the head unit. Now, your head unit doesn't have enough power to drive it so you can hear it over the NOW amplified speakers. You will need to have a mono sub amp installed to bring it up to the same levels as the rest.

BTW, on another note, I just had my new (to me, thanks to blitzoid) Alpine 7897 installed. WOW!! That thing is so sweet!! Now to get my DVD-RW on my computer to spit some MP3's onto a disc...

...it keeps telling me that it can't calibrate the laser power to the media I am using.
 

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Discussion Starter #6
thanks a lot for the info Roo! :)

I was wondering if I got a new headunit like you did and also a mono power amp will the stock sub work or?

Thanks
 

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Mr. November 2008
2015 BMW 335d xDrive GT Auto
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I think the guy probably just wired the two fronts and two rears into the HU, so as Roo says you'll need an extra amp for just the sub. The mystery is how the sub has got any power at all.

On mine I got a 4-channel amp, bridged two to make a beefy output for the sub, and the other two channels power the fronts. Then the new HU just does the rears.

In your position, if your new HU is a good-quality amp with a line-level sub output then just adding a mono power amp would do the trick at lowest cost. This should also give you better control of the sub output (level and frequency cutoff) than the original HU ever had.
 

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Discussion Starter #8
karma mechanic said:
I think the guy probably just wired the two fronts and two rears into the HU, so as Roo says you'll need an extra amp for just the sub. The mystery is how the sub has got any power at all.

On mine I got a 4-channel amp, bridged two to make a beefy output for the sub, and the other two channels power the fronts. Then the new HU just does the rears.

In your position, if your new HU is a good-quality amp with a line-level sub output then just adding a mono power amp would do the trick at lowest cost. This should also give you better control of the sub output (level and frequency cutoff) than the original HU ever had.
Yeah I guess I'm going to look into a mono power sub. Thanks Karma... but step 1... gotta install my new component speakers!
 

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AChan10 said:
thanks a lot for the info Roo! :)

I was wondering if I got a new headunit like you did and also a mono power amp will the stock sub work or?

Thanks

er... there's a LOT of different ways you could go from here..

1. Cheapest: use channels A and B from your 4-chan amp to run the front and rear sets together (lose fader control, now it becomes sub level control) and bridge channels C and D to power factory sub. Nothing extra to buy, and likely to give you darn nice sound still.

2. Second Cheapest: go old school and run "phantom channel" through a passive choke from the rear 2 channels of your existing full range amplifier in addition to running the rear speakers through a couple "bass blocker" nonpolarized capacitors -- despite this method falling out of favor in recent years believe it or not you can build a damn clean sounding system this way! This might cost you as much as TEN WHOLE DOLLARS extra for the choke coil!

3. Third cheapest: buy either a mono sub amp or a bridgeable 2-channel amplifier (any kind/brand/model, as long as it's not ULTRAcrapomatic) and daisy chain it from your current amp... if you get a mono sub amp in many cases it will come with a "bass knob" you can mount up front to adjust level

4. Fourth cheapest: buy a new head unit, power front 2 channels from channels A and B of your amp, rear 2 channels from head unit power (use "bass blockers" to improve S/N ratio slightly), and sub from channels C and D of amp.

5. Loudest: Buy either a mono sub amp or a bridgeable 2-channel amp, and a better subwoofer. A 10" in a sealed enclosure is likely to provide the cleanest/most accurate sound (i said LIKELY guys.. i know there are exceptions and variables) , a pair of any size in a slot-ported enclosure will give you the greatest volume output, but depending on the design of the box might not be as accurate as a well built sealed. I personally run a single 10" MTX 5500 woofer in a Sledgehammer vented enclosure and *love* it... but I'm a bit biased there.

Got any questions? ask.... this is what I do for a living :)
 
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