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Pathy Amp Info


cham
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I have a 2002 Pathfinder LE with bose system and Ive heard there is an amp in the rear cargo area powering the rear door speakers. I have just installed aftermarket speakers to both my rear doors and even though they are 2 ohm speakers, they have still dropped in volume. I was wondering if the factory amp that powers the rear speakers has tunability so i can up the gain or something to up the volume on the rear door speakers. If this is possible can someone tell me where exactly it is and how to get to it, thanks! If the amp doesnt have tunability, what are some other ways to increase the speaker volume?

Edited by cham
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There is nothing else you can do at this point other than replace the amp with an aftermarket one like I mentioned in one of your many other threads.

 

For future reference, try and keep all of the same-topic posts in one thread. There's no need to post a new thread every time you have another question regarding the same thing.

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Did you install something like the Scosche OEA-4? It's intended to interface aftermarket radios to the factory amp to avoid your volume issue. That's what I use with the Bose system and I don't have any problems.

 

And I agree with Kingman...keep the posts together please.

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Sorry guys didn't realize that was a big deal. Regarding the OEA-4 though, I had not thought about that. I have a factory stereo. Would replacing the stereo with an aftermarket change the quality and volume of the speakers because there is an amp in each front door powering the front speakers and an amp in the cargo area powering the rear speakers. Wouldn't changing the stereo to an aftermarket just cause the amps to adjust and still put out the same amount of ohms and watts as they did when the factory stereo was installed?

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Ha...I got mixed up because of the broken apart threads...I thought you had changed speakers and headunit, but kept the amp. Not a big deal to keep the posts together, but it you want more comprehensive answers, it's best to keep them all together so that details aren't getting missed (case in point here).

 

But yes, the radio would not affect impedance seen by the amp from the speakers. Changing the radio would change the line-level signal going to the amp (that's what that Scosche unit corrects).

 

Did you end up using aftermarket wiring harnesses to connect to the speakers? Are the polarities correct? The harness connectors to the speaker may only have fit one speaker tab, but that doesn't mean they're connected to the factory wiring correctly at the plug.

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Yeah I used aftermarket wiring harnesses for the rear door speakers but the speakers sound clear up close when I put my ear to it but they just don't get loud enough to where if you were sitting in the back you would notice them. Mostly you just feel some of the bass and the sound coming from the speakers upfront. Also I noticed that the rear speakers make a kind of high pitch frequency that irritates your ears a very little bit when ever symbols are played in a song. Is this a result of bad connection or do you not know?

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Also I want to be clear with what you said. So you're saying if i get an aftermarket stereo and install that with the Scosche adapter, I will be able to increase the sound coming out of the rear speakers even if there is a factory amp along the speaker wire between the HU and the rear speakers?

 

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Yeah I used aftermarket wiring harnesses for the rear door speakers but the speakers sound clear up close when I put my ear to it but they just don't get loud enough to where if you were sitting in the back you would notice them. Mostly you just feel some of the bass and the sound coming from the speakers upfront. Also I noticed that the rear speakers make a kind of high pitch frequency that irritates your ears a very little bit when ever symbols are played in a song. Is this a result of bad connection or do you not know?

 

It's something I'd have to hear, but sounds like distortion. Perhaps the amp is failing? When you turn the volume up, do you get any other noises/pops/static, or does audio quality degrade sharply?

 

Also I want to be clear with what you said. So you're saying if i get an aftermarket stereo and install that with the Scosche adapter, I will be able to increase the sound coming out of the rear speakers even if there is a factory amp along the speaker wire between the HU and the rear speakers?

 

 

Yes. The Scosche unit is a passive line leveler; you can set the gain for the speaker-level output going to the amp, and you can set each channel independently. There's nothing that would prevent you from using with the stock radio, either, but I don't think it'd be much different than using the fader setting on the radio (which btw, have you played with that and the balance to see if one speaker sounds better than the other?)

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Yes I have played with that but once I move the fader towards the rear speakers, the sound up front becomes less clear in quality and drops a tiny bit in volume each number I go in the rear speaker direction. I also heard using an outline converter drops some of the quality and clarity of the sound is this true, I'm wondering if its that noticeable or not. Also I use a tape aux converter as an aux chord for my phone and its static anyways when I increase the volume a lot while using the tape aux. Im wondering if when I replace the front speakers they will drop down in volume too just enough to where they match the back speakers so when I turn up the volume on the HU they both increase at the same level.

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Yes I have played with that but once I move the fader towards the rear speakers, the sound up front becomes less clear in quality and drops a tiny bit in volume each number I go in the rear speaker direction. I also heard using an outline converter drops some of the quality and clarity of the sound is this true, I'm wondering if its that noticeable or not. Also I use a tape aux converter as an aux chord for my phone and its static anyways when I increase the volume a lot while using the tape aux. Im wondering if when I replace the front speakers they will drop down in volume too just enough to where they match the back speakers so when I turn up the volume on the HU they both increase at the same level.

 

You've got a couple things going on in there, so to tackle those first:

 

--I think you're talking about line-out converter that takes a speaker level input and converts to a pre-amp output. I guess that's essentially what the Scosche unit does, though its description is a little vague. I have the unit, and quality seems fine to me (as fine as can be expected from stock speakers, anyway).

--A cassette adapter will definitely introduce noise and degrade audio quality.

--Not sure how new front speakers would react.

 

In all honestly, there are a few variables that can influence things. You'd expect things to be plug-and-play, but when other non-standard components exist in a system, it could easily be apples and oranges. The BOSE system is exactly that: a system. Without knowing the specs of the amp, though, it's hard to know what's going on. Perhaps it has a LPF that was suitable for stock speakers, but now you've added 2- or 3-ways that are being under-utilized. Not saying that's the case here, but a possibility.

 

IMO, the gains from changing the headunit on a stock system far exceed those of changing speakers on a stock system. A new headunit with built-in EQ settings, custom EQs, a loudness setting, and adjustable ranges and cut-offs can liven up even the most basic speakers simply by filtering (HPF/LPF) frequencies and focusing sound where it belongs. New speakers are only going to take the same stock signal and...well, hopefully expand on it if they have better frequency response, and integrated cross-overs. I wouldn't even be surprised if a new headunit has a more powerful internal amp than the BOSE amp(s), so you might get better results just by bypassing it (which is easy to do). Plus, with features like USB, AUX, and BT, those are 3 ways for music playback without degrading sound quality.

 

Out of curiosity, what speakers did you buy? Maybe there's something we can determine from their specs. Are your OE speakers stamped with a 2Ω?

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Ok well I used JBL GX602 coaxial speakers for the rear doors and they are rated at 2 ohms which I was led to believe is the same as the amp. But as I said before the volume still dropped. Second, I'm not sure if I have already told you this, I probable have but there are 2 amps in the front apparently. One in each front door powering each front speaker. Its literally adjacent to the woofer. Finally there is an amp in the rear cargo area powering just the rear speakers. This is just to give you the amp layout. But back to what you said about bypassing, that seems like a huge task, how is that easy. If i were to just replace the headunit and use the Scosche adapter and not bypass the amps would i still get a significant increase in speaker sound quality, like closer to the speakers full potential. Im still confused because I keep thinking no matter what is sent from the HU to the speakers, the amps adapt and just output the same amount of power as it did with the factory headunit. Is that a completely mislead statement?

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No sweat. Sorry the answers are pretty generic...it's because of the unknowns (specs) about the Bose system. I'm familiar with it; I have it in my truck.

 

Bypassing the amps is easy: the audio signal both enters and exits each amp, so you can just unplug its wiring harness and jump the input wires to the corresponding output wires. The wiring harness stays unplugged, and the amps collect dust. You'd only do this with an aftermarket headunit, while running all speakers at 4Ω (typical for aftermarket radios). The front speakers are easier...you just wire the input and output signal to the new crossover.

 

In your current setup with cassette adapter, you're introducing noise. The amp is just amplifying a bad message. Garbage-in, garbage-out.

 

With an aftermarket headunit (let's ignore the Scosche unit for a moment), you get better sound because you'll have more ability to control it. Not only are you maintaining a much higher signal-to-noise ratio (a good thing) by using some other input method (USB/AUX/BT), but you can control the frequencies to each channel. This allows each speaker to only reproduce frequencies that it should (or can) handle. You want that sort of separation. And that's the advantage of 2-way, 3-way, and component speakers...when you send them a full-range signal, they're already configured to break up the frequencies so that each individual speaker covers a certain range (compared to stock where a single speaker is trying to reproduce all frequencies it receives and can handle). Again, the amp is just the messenger...but it's no longer garbage-in, garbage-out.

 

The signal going into the amp is far more important than the signal coming out of the amp...and far more sensitive. That's why you get higher volt pre-amps, better insulated RCA cables, running cables away from other electrical sources...all things that produce and keep a clean signal. The purpose of the Scosche is ensure the signal between the aftermarket headunit and OE amp is at a sufficient level so the amp can maximize volume and minimize distortion.

 

The unfortunate catch is that none of this really explains why your rear speaker volume is low. :D The JBLs are spec'd at 2.3Ω, which could be enough additional load (15%) to reduce volume (by 15%), but that assumes that the OE speakers are really 2Ω. More resistance, less watts, less volume. If you haven't already, I would also confirm the polarity at the speaker...according to the FSM, the + feed some be coming from an orange factory wire, and — to a black/pink wire. Without hearing it, one or both of those things could reduce volume.

 

If the slightly higher resistance were the problem, you could run a 15Ω resistor with a high enough wattage (10W?) rating in parallel with the speaker to bring load back down to 2Ω. You'd need to know how many watts the amp produces to know how many watts the resistor needs, but according to one online calculator, a 50W amp would send <7W to the 15Ω resistor. 50W is just a guess, and a higher wattage resistor doesn't hurt anything.

Edited by hawairish
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Ok things are starting to click. You're making sense but I wish I knew about this way to remove the factory amps completely before I bought those 2 ohm JBLs lol. So taking the rear amp out and just hooking the input to output wires will work. Home come I couldn't just simply replace the amp then with a better one? Also for the front ones, are you sure you can just put the crossover in the amps place, I doubt they have the same wiring that would work. Would pulling out all the amps and upgrading the headunit and replacing the front speakers with 4 ohm sound better than if I had the amps and an upgraded headunit but used 2 ohm speakers? So basically I'm asking which is better, 4 ohm for front speakers 2 ohm for back and no amps or 2 ohms for all speakers and the factory amps?

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I'll preface things with these:

  1. There are many ways to do the same thing
  2. Impedance has nothing to do with sound quality (at least not directly)
  3. The absolute biggest constraint to answering any of these questions is the fact that we have no specs about the Bose components or system; we just have a system description, some diagrams, and some assumptions
So taking the rear amp out and just hooking the input to output wires will work. Home come I couldn't just simply replace the amp then with a better one?

 

No reason it shouldn't. Nothing stops you from replacing the amp. The harness has everything you'd need...however, you'll rarely (er, never?) see anyone re-using factory wires for an aftermarket amp for a few reasons (fire being one of them).

 

Also for the front ones, are you sure you can just put the crossover in the amps place, I doubt they have the same wiring that would work.

 

You calling me a liar?! Kidding. :D

 

For the same reason above, you have the signals you need. I can't think of why this wouldn't work. If you choose to not use the amp, all you have to do is take the amp circuitry out of the equation. You could re-use the amp...but again, we don't know what its specs are. Keep in mind, too, with stereo installs, it's not uncommon to need to splice, solder, and crimp things.

 

Would pulling out all the amps and upgrading the headunit and replacing the front speakers with 4 ohm sound better than if I had the amps and an upgraded headunit but used 2 ohm speakers? So basically I'm asking which is better, 4 ohm for front speakers 2 ohm for back and no amps or 2 ohms for all speakers and the factory amps?

 

The big question. The answer: entirely subjective and/or difficult to know!

 

Impedance is irrelevant in terms of "what's better", unless you're asking, "what's better for the power source". Amps (amplifiers or headunits) have their own levels of efficiency at different power outputs. You manipulate the impedance (or really, the perceived impedance by the power source) to get different power outputs. There are numerous ways to do this: speakers in parallel or series; speakers with dual voice coils (DVC); speakers with different impedances; bridging channels; resistors, etc. The decision to do any is largely based on the design of the system (how many amps, how many subs, etc.) and the specs/features of each component. Specifically for amps, some can handle different impedances better than others.

 

Personally, I'd keep the amps, keep the speakers, and upgrade the headunit at this point. I think that provides the next best step in improvement, requires the least amount of work, and provides the most new features. Even the most basic headunits have great features, including pre-amps should you decide to add some amps down the line.

 

Not to drone on as I usually do, but take a look at the features on the most generic and inexpensive stereos at Crutchfield. A 13-yo Bose radio can't even remotely compare.

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Haha I kind of got lost when duel voice coils was brought up but I get the overall just of what you're saying. Also yeah I agree with you about just upgrading the headunit for now which is originally what I was going to do but one of the crutchfield advisors claimed it would not improve my system by much because of the amps. So I'll be traveling down that path except I will be replacing the front speakers as well. If I'm installing a component set, I'll be able to use the factory front door amp with the new woofer and tweeter and just not use the crossovers at all right? Not using the crossover won't create any problems would it? Or should I just rip those god for saken front door amps out of there and replace them with crossovers because I'm confused as to if I rip those amps out will it affect the rest of the system like the rear cargo amp or anything? Lastly, does replacing the HU just add features to in turn use to improve the quality or does just installing it make the quality better by itself without messing with the features.

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Haha I kind of got lost when duel voice coils was brought up but I get the overall just of what you're saying. Also yeah I agree with you about just upgrading the headunit for now which is originally what I was going to do but one of the crutchfield advisors claimed it would not improve my system by much because of the amps. So I'll be traveling down that path except I will be replacing the front speakers as well. If I'm installing a component set, I'll be able to use the factory front door amp with the new woofer and tweeter and just not use the crossovers at all right? Not using the crossover won't create any problems would it? Or should I just rip those god for saken front door amps out of there and replace them with crossovers because I'm confused as to if I rip those amps out will it affect the rest of the system like the rear cargo amp or anything? Lastly, does replacing the HU just add features to in turn use to improve the quality or does just installing it make the quality better by itself without messing with the features.

 

DVCs add flexibility to getting the impedance to a particular level, among other things. For instance, a 4Ω DVC sub can run as 1x 2Ω, 2x 4Ω, or 1x 8Ω depending on how you wire it, and what the amp is capable of powering.

 

The Crutchfield advisor is right in the sense that everything downstream of the radio is essentially unchanged, but is grossly neglecting what I've mentioned previously: the ability to shape the sound image (the function of an equalizer) can play a big role, even on basic components.

 

If you install a component set, you should use the crossover that is supplied. It is specifically designed to cut frequencies that the component speaker or tweeter should not play. Lower frequencies require more power to reproduce, and tweeters in particular should not attempt to play them. As before, we really don't know what the front amps are spec'd out, so if changing the speakers, I would recommended to not use the front amps. Not using (or removing) the amps should have no impact on the rest of the system, according to the FSM. I previously mentioned that you could use them, but that's really only if you know what they're spec'd at, and that's the problem.

 

If you decide to play your music (via phone, iPod, USB stick, etc.), it will most certainly sound better even if no qualifier settings are enabled. Using the cassette introduces noise because it has a lower signal-to-noise ratio. Those other means have higher SNR's, which is what you want. As such, you're already making a difference.

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Ok I'm agreeing with just the components up front and aftermarket stereo install. I only have a couple questions left haha bear with me a little longer. What would you suggest I should tinker with equalization wise on whatever new aftermarket stereo I get? What categories i.e. treble, fader and things of that nature are the most important in shaping the tone and sound imaging? Finally,what exactly does the Scosche adapter do? I know you stated this already before but I couldn't quite follow. My questions is, why do I need it rather than not using it at all. Is there benefits to using it or is it a necessity for aftermarket radios in a system like mine?

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Honestly, each radio brand has its own way to provide both simple and advanced ways to shape sound. Because sound quality is completely subjective and variable, it would be difficult to say how to best achieve the right sound.

 

But, let's put it this way: nearly all brands offer some sort of Presets setting. These are EQ settings based on "your" type of music, like Pop, Rock, Jazz, Country, Bass, Dynamic, Vocals, Acoustic, etc. At the most basic level, you could just toggle between the presets and see which sounds best to you. You'll definitely notice a difference between them. If none seem to be great, then you can usually start with one, and tweak the high/mid/low settings from there and make your own custom profile. Not only is this probably the fastest and easiest way to shape the sound, but it's also really the basis of any other settings you might use.

 

What the Scosche adapter does exactly...well, it adjusts the gain of the speaker output of the radio before it hits the amp. The OE amp does not have an adjustable gain setting; the Scosche unit adds this function. You would not need it with an aftermarket amp because practically all of them already have it built in. Adjusting gain is a fundamental step when configuring any custom system. You don't need it if using the OE amps, but if the output from the radio is low, the volume will be low without it.

 

That said, if you get it, there are also some additional steps to properly configure it, much like configuring an aftermarket amp.

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So what have you settled on doing at this point?

 

As I read the whole thread, I realized that you had only replaced your rear speakers, is that right? And they are 2 ohm like the originals...

But here's the thing. These babies are 60wRMS and your originals? I have NO IDEA. They might be 20w. In this case, you have speakers that require a heck of a lot more power to be properly driven than the amplifier is putting out. Hence the crappy performance.

 

You will need to replace your rear amp to properly power these speakers. (if so, make sure the amp is properly sized for those speakers)

And if you just bypass that amp and drive it off of your head unit directly, same problem.

If you get an aftermarket head unit, you will be pretty much stuck at about 20w RMS because that's about the limit of what you will get out of the 12v supply power to the head unit.

 

Since the stock head unit is designed to be used with the amplifiers, it's possible that the output signal going to the amps is a low-level output designed for pre-amp signals.

Or, it could be a high-level signal for line output to speakers and the amplifiers are expecting the line level input.

 

I think that it's the latter, because when I installed a new head unit, I wired the line-level output to the wiring harness and that feeds my stock amp and it works fine....however, I have the non-Bose stereo (with 1 amp in the rear), and it's conceivable that they differ in this regard.

 

You can check this with a volt meter BTW.

 

 

Also, I think hawairish might have been wrong above, regarding the Scosche adapter. I believe these are simply line adapters that will let you take a line-level output from your head unit and step it down to a low level pre-amp input so that you can feed an aftermarket amp with a stereo that either doesn't have pre-amp outputs, or in case you simply prefer to use the line-level outputs to feed your aftermarket amp because you don't want to run new RCA cables.

 

 

Another misconception I see that you had is that you believe there is separate output signals being sent from the front amps in the doors to the door speaker and the tweeters. You are assuming it's already doing the crossover function for you. It's not. Both are getting the entire audio signal. They are wired in series. The door speaker can handle getting the highs, or has a built in (to the speaker) low-pass filter and the tweeter has a resistor that acts as a high-pass filter.

You WILL need to use the supplied crossovers if you replace those speakers, even if you keep the original amps in the doors.

 

 

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Ok so then what if I replace the factory front door amps with crossovers completely. Just have crossovers in place of the factory amps. I believe you were saying it's possible but is it very difficult? Also what were you saying about bypassing the rear amp? Were you saying even if you did bypass it the HU would still only put out 20wattsRMS? Should I replace the rear amp of bypass it, which would be better?

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I tore my entire factory Bose system out of my '04. The front doors did not have an amp, it's a cross over like I had mentioned in another thread. The doors receive the full signal, then from there is split by the cross overs to the mid driver and tweeter. That's why I had said all you need to do is literally install the component set with the aftermarket cross over in the factory spot with the factory wiring.

Edited by Kingman
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