Installing new speaker. Problem need help!!

[QX4kid]

I just bought a pair of speaker for the driver and passenger side doors. Now when I installed the new speakers I am getting a fuzzing sound(like when your speakers are about to blow) when i turn it up all the way. when Uninstalling the factory bose speakers do i also have to uninstall the factory amp of the speakers too. If so how do I connect the new speakers to the car.BTW I have a kenwood DDX-512 headunit and the speakers I bought are 200w kenwood speakers

[Pwnin O'Brien]

You probably hooked your head unit up to the amp, which you do not want to do. With the factory Bose head unit, the head unit does not power the speakers, they send a low-level signal to the amp, which is then amplified and sent to the speakers.

Assuming you didn't use the low-level outputs on your head unit, you are now sending a high-level signal to the amplifier which is then trying to amplify the already amplified signal. You want to disconnect the amp and remove it completely and send the head units amplified signal to the speakers.

The easiest way is to just remove the amp and patch the head unit outputs to each door to their respective wires into the speakers.

You will also need to do this for the rear speakers.

[korbeano89]

did you accidentally mix up positive and negative

[QX4kid]

i think everything is installed right with the headunit. I meant by factory amp was the one that each doors have a small box. do I have to remove that to install the new speakers.

[Pwnin O'Brien]

I'm not extremely familiar with the Bose setup, but I though that the factory speaker and amplifier for the front doors were one unit, thus requiring you to remove the speaker and amp as one?

Anyhow, let me try to explain what I was talking about before...

The factory Bose head unit does not have an internal amplifier, which means it is not powerful enough to power speakers alone. The Bose head unit will have standard speaker outputs (Front/Right, Front/Left, Rear/Right, Rear/Left) just like every other head unit, with one exception. Those outputs will only output a low-level signal, meaning they output probably a maximum of 2V or 3V.

That low-level signal is then sent to each respective amplifier, which then, depending on the amplifier, will amplify the signal. So let's say (hypothetically) that each factory Bose speaker has a voltage gain of 10 and the factory Bose head unit has a low-level signal output of 3V. Each amplifier will output a 30V signal to the speakers (10 x 3).

Now, when you pull out the factory head unit and replace it with a new head unit with an internal MOSFET amplifier, you are now sending a high-level signal (an already amplified signal) to each respective amplifier. So say your new head unit sends 10V per channel already to each amplifier which have a voltage gain of 10, you are now trying to send 100V to the speakers. Now the speakers may be able to handle the power, but the factory amplifier cannot. Those amplifiers are definitely not spec'd to handle and output of 100V (let alone an input of 10V).

So when you turn up your volume, thus increasing the current, you are in effect pushing the amplifier to the limits, and that is probably causing the static noise.

Now, I could be completely wrong and your head unit may have pre-amp outputs which are connected to those amplifiers, but I have a feeling that they are not. Did you wire your head unit or did you have it done by somebody?

My solution:

When you pull the amplifier out of the door, you want to take the wires that come from the head unit (the harness going into each amplifier) for that speaker, and patch it to the amplifier output for that speaker.

I don't know, I may be nuts and wrong about everything, but from what you've written this sounds like your problem.

[Pwnin O'Brien]

I would also be completely wrong if you had new wires run from the new head unit to the speakers or if the wires had already been patched, bypassing the amplifiers already.

[mda185]

You can't keep the Bose amplifier to drive any other brand of speakers. The Bose speakers are matched to the amp and have an impedance that is not standard. I think it may be 2 ohms but not sure about that. I will know shortly because I am in process of upgrading my system.

The factory Bose system actually has a drive voltage from the head unit that is greater than the standard 2 volts RMS that is used by most aftermarket head units. I found this out when I replaced the Bose head unit with an Alpine DVA-9860 DVD head unit. I used the Scoshe adapter that lets you use low level outputs from a head unit to drive the Bose amplifiers directly. The Alpine could not drive the Bose amps cleanly from the preamp outputs. I installed an old school Precision Power PAR-225 preamp EQ between the head unit and the Bose amplifiers and the sound was improved tremendously. The PAR-225 has a 5 volt RMS output with a lot of headroom. I measured it on an oscilloscope at 10 volts peak to peak before clipping set in. The PPI preamp is out of production but you can find them used. Audio Control also makes a similar unit called the Four.1i.

Having good drive voltage from the head unit will not solve your problem with the aftermarket speakers. If you want to upgrade speakers, you need to ditch the Bose amp and run speaker wires from your new head unit or aftermarket amplifier if you want more power. I am installing an old school PPI power amp in the back to drive upgraded front speakers as my next step. I am fabricating speaker mounting rings out of MDF and Plywood to replace the OEM Bose amp and speaker mounting ring.

If you want to see a super clean install on an R50, go to DIY Mobile Audio forum and search for Pathfinder under the install sub forum. There is a guy there that did a beautiful job including making new door panels. I am not going as far as he did but the build log is very educational. I would give you the link but DIYMA is down right now.
Modified by mda185 at 1:28 PM 8/8/2009