update amps and speakers

[infiniti2007]

Hi guys, I got 2007 infiniti g35x (sedan) with non bose HU. I would like update all the speakers with 4 channels amp, and sub woofer with another 2 channels amp. How do I hooks them up? Thanks.

[pfarmer]

Hi guys, I got 2007 infiniti g35x (sedan) with non bose HU. I would like update all the speakers with 4 channels amp, and sub woofer with another 2 channels amp. How do I hooks them up? Thanks.

With wire.

Perry

[infiniti2007]

I know, If I hook 4 speaker's wire ( 2 front and 2 rear ) to the high input of the 4 channels amp. Where do I hook up the wires for the sub woofer 's amp?.

[pfarmer]

I know, If I hook 4 speaker's wire ( 2 front and 2 rear ) to the high input of the 4 channels amp. Where do I hook up the wires for the sub woofer 's amp?.

I think you need to do research using the Infiniti factory service manuals located on this site.

One of the issues you need to consider is that the output of the head unit is not simply a ground and a plus. It is instead a negative and a positive which means the signal swings past the zero centerline. You new amp on the other hand probably has a ground and a plus. You may have issues taking the negative of the head unit to ground without providing isolation.

Perry

[infiniti2007]

Wow, it sounds too complicated. Is there any simple way to do this? If not I just use two front channel for my sub.

[pfarmer]

Wow, it sounds too complicated. Is there any simple way to do this? If not I just use two front channel for my sub.

There are several ways of doing this. Without doing a little more research I hesitate giving a suggestion beyound a couple of the ways possible. One method is what amounts to an audio transformer which isolates the primary (the head unit side) from the secondary (the new amp side). In this situation you need to impedance match the primary which I am not sure of what to match it to. Basically the same occurs on the secondary with one leg grounded.

Another method is to simply use a 1-1 preamp that is fairly easy to build. In this case basically the signal to the base of a transistor is connected to the output of the head unit. One side of that (either positive or negative depending on the transistor - pnp or npn) is also connected to a resistor with one end of it at ground potential and attached to the emitter, the other end of the resister is attached to the negative side from the head unit. The collector is then attached to either another resistor or a similar audio transformer mentioned above. The aim here is that the emitter is floating at ground potential which provides the isolation.

Another method is an opto-isolator (be careful using this term as it means different things in different industries) which provides no electrical connection between the two sides.

Still another method involves a set of diodes (think half wave rectifier).

The part I do not know at the moment is the impedence at the input of the Infiniti amp. The signal voltage is plus and minus 1 volt.

You may do some research into this as you may run across a ready made unit that matches the criteria. Units for doing what I mention do exists. Some of these are simply pre-amps with isolated inputs (often used for headphones).

As far as the amp goes instead of a 4 channel and then a sub you may consider going with a 5 channel instead which simplifies things. The 5 th channel is often designed as a sub.

Some have been ignoring this and just put in an amp but it also may explain some of the failures with head units.

Perry

[pfarmer]

Wow, it sounds too complicated. Is there any simple way to do this? If not I just use two front channel for my sub.

This is an example of one with opto-isolators. Note it is powered by 12 ac but has to be dc internally.

One typical use of these is for home theatres which may be a good search keyword.

What occurs is that in some cases many will use multiple ac outlets. As you know if you have a 3 wired plug you have a ground, neutral, and hot. The neutral and ground is normally connected at your load center (breaker box)

At the outlet however they can be at a different potential, in fact are at a different potential. Also not all components use a 3 wire plug. Also not all components are plugged into the same outlet. The point here is that the ground side of your RCA audio (and video) connections can easily be at different potentials. If so they you have current flow in the grounded shield which can be induced in your signal carried on the center conductor within the shield. The result is the 60 cycle hum often heard. The opto isolator will essentially disconnect the shielded side of the of one components output from the other components input (the same for the signal side as well).

An audio transformer does basically the same thing but puts a load on the output side of the source which is ok but needs to be impedence match. Audio transformers also have issues with essentially modifying the signal since it is an inductor.

In the case of the opto isolator it may be necessary to impedence match to the head unit if the head unit expects a load. Now the importance of this statement is that it is entirely possible that the Bose amp is actually connected to the head unit through internal opto isolators already. This would not be unusual in newer automobile applications where ground loops can easily be present (hint aftermarket grounding mechanisms). This may be able to be partially confirmed by testing the normally grounded side of the RCA aux jacks to chassis ground. If they are not at ground then that may be an indication of what is present. This is not a sure fire method since the aux inputs actually go to the head unit but may well show the logic present in the overall system design.

I'll see what else I can figure out.

If you decide on the 5 channel amp there are some variations here as well. I would go with one designed with the 5th channel being one for a sub woofer with its input coming from the other 4. The reason is that in the Bose system this is done internally in the Bose amp, you probably want to duplicate this function for simplicity. If not then basically you need to take the 4 other inputs from the AV unit and combine them to obtain the sub woofer input signal to another amp. This would be done in a similar way to what you need to do with bringing in the other channels into the 4 channel amp inputs.

If you want a separate amp for the woofer then there are simple circuits for doing this at the rca standard input levels, many designed for aviation headphone use to combine various voice based systems into one, such as navigation, radio, etc. Don't let the aviation aspect get to you, they are very, very cheap, as in cheap to roll your own, the schematics readily available.

Perry
Modified by pfarmer at 11:31 AM 7/19/2009

[infiniti2007]

Thanks for your inputs Pfarmer. Yes, I would like a separate amp for my sub. You said , there are simple circuit for doing at RCA standard input levels. Could you show me the schematic, please?.

[pfarmer]

Thanks for your inputs Pfarmer. Yes, I would like a separate amp for my sub. You said , there are simple circuit for doing at RCA standard input levels. Could you show me the schematic, please?.

This should work once you are at the RCA level using an opto isolator first.

https://matronics.com/aeroelec...J.pdf

What we are doing here is using this as a capacitive coupled mixer. The amplification is 1-1. You would use about 1/2 of this circuit since it is designed for two headphones. It uses a common ground. This is intended for combining the 4 audio - FLeft, FRight, RLeft, and RRight to use as an input for the aftermarket sub amp.

Perry

[infiniti2007]

That 's too confusing for me , Perry. I think, I stick with 4 channel amp to drive to 2 front for the sub woofer. I don't have factory sub or amp, so I just run the speaker wires from Hu to the high level inputs. Will it cause any problems to HU later on?. Thank you for your help Perry.

[pfarmer]

That 's too confusing for me , Perry. I think, I stick with 4 channel amp to drive to 2 front for the sub woofer. I don't have factory sub or amp, so I just run the speaker wires from Hu to the high level inputs. Will it cause any problems to HU later on?. Thank you for your help Perry.

I just reread your original post, you have a non-Bose unit. Forget everything else. If you are going with the aftermarket amp using the high level inputs you may want to protect the head unit by loading the speaker outputs from the head unit. Most will just put in resistors (which you may get away with) but in reality you should be using a load that simulates the speaker (inductor). You want to impedence match. Don't mistake this as simply resistance as many do.

I am not saying you can't get away with resistance loading but for best results and for best protection of the head unit you want to impedence match. This should help you out if you are going to use the high level inputs on another amp. You may be able to select an amp that does this for you.

In my case I would take this as an opportunity to replace everything which becomes somewhat of a project for interfacing some of the other functions besides audio present dealing with the stock display. I would go with a carputer.

Perry

[infiniti2007]

Ok ,I 'll do that, thanks for everything ,man.

[infiniti2007]

By the way, you wouldn't know the color wires for speakers for this car , would you?. If you do , please share them with me. Thanks.

[pfarmer]

By the way, you wouldn't know the color wires for speakers for this car , would you?. If you do , please share them with me. Thanks.

Note that you are still dealing with plus and minus, not plus and ground (+1v to -1v):

This is a device that should work:

Terminal number on AV unit, value, and color

Front Left #2, +, (L) Front Left #3, -, (W)

Rear Left #4, +, (LG)Rear Left #5, -, (SB)

Front Right #11, +, (BR)Front Right #12, -, (R)

Rear Right #13, +, (L)Rear Right #14, -, (P)

http://www.installer.com/item/...SVEN4

Note the term of importance here is balanced to unbalanced.

Balance is referring to the plus and minus situation I mentioned above. The advantage is that any noise is introduced into both lines and then is rejected since the amplifier is a 'differential amplifier'. That is it will amplify the difference between the plus and minus lines coming in. It will output to an unbalance signal (rca) which is referring to the fact that one side is grounded.

There are a lot of these types of devices available but keep in mind the term 'balance' as that is what is important here.

You can also easily build one of these with three op-amps and a few resistors for each channel.

Perry

[infiniti2007]

I was looking at the manual book (Rockford fosqate amp) and it shows that I can hook up 3 CHANNEL MODE on TWO CHANNEL AMP. You can have 2 speakers with 2 ohm and then bridge the third sub with 4 ohm. So if I install the 4 CHANNEL AMP. Can I have 2 FRONT and 2 REAR speakers with all 2 ohm, and BRIDGE all four channel together to produce my sub woofer ( 4 ohm).

[pfarmer]

I was looking at the manual book (Rockford fosqate amp) and it shows that I can hook up 3 CHANNEL MODE on TWO CHANNEL AMP. You can have 2 speakers with 2 ohm and then bridge the third sub with 4 ohm. So if I install the 4 CHANNEL AMP. Can I have 2 FRONT and 2 REAR speakers with all 2 ohm, and BRIDGE all four channel together to produce my sub woofer ( 4 ohm).

I do not believe so. The amp is essentially 4 amps internally with a common chassis. You can bridge the outputs of 2 or more amps together if designed to do so. What they are telling you is that you can use 2 channels in normal mode and bridge two more to form a 3rd channel for the sub. This would be a good setup for example in a truck or a coupe without a back seat set of speakers.

In my other car I am using 2 five channel amps. With this setup you have 4 separate channels for the 4 doors and one channel for the sub. The advantage of this over a separate sub amp is the 4 channels are internally combined to form the input for the 5th channel for sub use.

This type of setup usually use some form of isolation such as a set of internal opto isolators similar to the circuit I sent you previously. If the amp is not designed this way you need to do this externally or use a sub amp designed to do this which some are.

On some sub amps you can do this with simply four 'y' rca jumpers but keep in mind the concept of current loops if the setup is not properly grounded to the same exact point. Isolation would be of benefit here as well to insure you don't introduce noise.

If you ground these amps do not inproperly stack grounds like you will see on many poorly designed grounding kits being sold for various cars including Infiniti.

A proper stacked ground would have no more than two conductors. The frame and other metal components of your car will be at ground potential as long as the factory ground has not been compromised. A proper stacked ground will only have 2 conductors. The reason is that the bolt connecting the ground to the frame can at best provide the same ground potential to the head of the bolt in direct contact with the top conductor as the frame is providing to the bottom conductor. If you place more than two conductors in the stack then the the center conductors are now part of a set of series resistors, the resistors being the resistance of all the connections in the stack. The more conductors the greater the possible chances of differential grounding and noise being introduced.

If you need to ground multiple conductors to the same grounded bolt, etc. use a grounding block. This is good advice even if only two conductors are involved but get a grounding block for at least four. The block is grounded and then the ground conductors are connected to it.

Perry