Adding amp and sub

**1st TA** · 11-09-2006, 06:32 PM

I would like to an amp and sub to my stock monsoon system. I would like to know if the aoem-gm21c is the correct adapter to do this. I have an 02 TA. The application chart that I have seen lists 98-01 for this item. Any help would be welcome. Thank you.

**mr.yellow** · 11-15-2006, 12:24 AM

let me know how you make out. what is that adapter anyway? I see you are not sure if it is the right one or not but does it connect the amp to high pass connection through the speaker wires or something else?

**White Rascal** · 11-15-2006, 03:40 AM

Originally Posted by 1st TA

I would like to an amp and sub to my stock monsoon system. I would like to know if the aoem-gm21c is the correct adapter to do this. I have an 02 TA. The application chart that I have seen lists 98-01 for this item. Any help would be welcome. Thank you.

The PAC Application Chart says it is for Camaro and Firebird Monsoon systems from 1998 thru 2003.

Originally Posted by mr.yellow

let me know how you make out. what is that adapter anyway? I see you are not sure if it is the right one or not but does it connect the amp to high pass connection through the speaker wires or something else?

The GM21C is a harness that connects a PAC OEM-1 speaker level to line level converter to the factory wiring harness so you don't have to cut and splice any of the factory wiring. However you do need to do some splicing of the GM21C harness because PAC accidently flip flopped the Left & Right channels. There is no high pass connection. The signal is full range.

**mr.yellow** · 11-15-2006, 01:17 PM

So where does it hook in to the factory harness? Do you know if it matters if it is a vert or not? Other than the splicing you have to do is the gm21c worth it to install.? Does it add RCA imputs? Sorry so many questions but you seem to definately know your stuff so again any info you have will be much appreciated? Thanks!

**White Rascal** · 11-15-2006, 01:41 PM

It plugs into the factory harness behind the HU. It doesn't matter if it's a rag top or not. It only adds RCA outputs.

**mr.yellow** · 11-15-2006, 03:26 PM

I do have some experience with adding subs to an after market system but it has obviously been awhile so please correct me if I am wrong. If I add the gm21c and hook up the amp through the RCA's and from the amp to my subs then I shouldn't have any problem right? I mean other than splicing the gm21c! I run my RCA preouts to my amp and add power,ground, and remote on and then tune in the amp. That should be it right? Do you suggest anything like a low pass filter or anything else? Do you think this is the best way to add an amp and subs to the factory system? Many many thanks!

**White Rascal** · 11-15-2006, 04:22 PM

Originally Posted by mr.yellow

I do have some experience with adding subs to an after market system but it has obviously been awhile so please correct me if I am wrong. If I add the gm21c and hook up the amp through the RCA's and from the amp to my subs then I shouldn't have any problem right?

The GM21C is only the wiring harness adapter. You also need the OEM-1 which is the actual speaker level to line level conveter. You need the two together to have a plug and play setup.

Originally Posted by mr.yellow

I mean other than splicing the gm21c!

You don't have to do any splicing actually. Just reverse the Left/Right RCA connections when you connect the amp to the OEM-1. And since most subwoofer applications are mono it really doesn't matter which is left or right.

Originally Posted by mr.yellow

I run my RCA preouts to my amp and add power,ground, and remote on and then tune in the amp. That should be it right?

Don't forget to add a fuse to the power cable near the battery.

Originally Posted by mr.yellow

Do you suggest anything like a low pass filter or anything else?

The amp should have a crossover already built in.

Originally Posted by mr.yellow

Do you think this is the best way to add an amp and subs to the factory system?

No. The entire POS Monsoon system should be replaced. The factory HU puts out a lot of distortion at only moderate output levels. (I know because I used a calibrated test disc and my O-scope to set my gain levels when I only had the POS Monsoon system in my car.) The higher you turn it up the worse the distortion gets. On top of that the POS Monsoon amp is not a true power amplifier. It's what I would call a seriously over-hyped and over-rated power booster. So now you're running a badly distorted signal into this POS power booster which adds it's own distortion. This is why the factory speakers are blowing all the time. In the long run you're better off with an all after-market setup.

**midnightrider** · 11-15-2006, 05:12 PM

Question for you White Rascal. You said the entire Monsoon system is a POS. And I would agree. So I want to change my head unit and front speakers, which I have now. Later I will add and amp and sub. How can I use the factory front speaker wires so I don’t have to try and run new wires through the doors. Is this even possible?

**White Rascal** · 11-15-2006, 05:37 PM

Originally Posted by midnightrider

Question for you White Rascal. You said the entire Monsoon system is a POS. And I would agree. So I want to change my head unit and front speakers, which I have now. Later I will add and amp and sub. How can I use the factory front speaker wires so I don’t have to try and run new wires through the doors. Is this even possible?

I don't recommend using any of the factory wiring. I run all new wries for all my installs. If you insist on using the factory speaker wiring all you have to do is use a wiring harness from your local car stereo shop. It will let you connect the new HU to the factory wiring without having to splice into any of it. Be sure to use the right set of speaker wires in the doors. Firebirds have one set going to the tweeter and another set going to the mid-woofer. There seems to be some debate on how exactly the speaker wires are connected to the factory amp so I would use a multi-meter with a continuity tester to see which wires in the doors are connected to the speaker wires behind the HU.

**mr.yellow** · 11-15-2006, 05:42 PM

I do have the inline fuse from the +battery and I even ran a 6 gauge ground wire from the -battery to the ground on the amp because I heard from a tech that if a spike occurs and it's grounded to the body it could really screw up the electrical system on our cars. Do you think that is true? I didn't realize the system was that bad but o scopes don't lie. I wanted to add an aftermarket system into the car but I really like the steering wheel controls plus I wanted to keep my car original but I could always put the stock one back in. Thanks for everything White Rascal your knowledge has been extremely helpful!

**White Rascal** · 11-15-2006, 06:14 PM

Originally Posted by mr.yellow

I do have the inline fuse from the +battery and I even ran a 6 gauge ground wire from the -battery to the ground on the amp because I heard from a tech that if a spike occurs and it's grounded to the body it could really screw up the electrical system on our cars. Do you think that is true? I didn't realize the system was that bad but o scopes don't lie. I wanted to add an aftermarket system into the car but I really like the steering wheel controls plus I wanted to keep my car original but I could always put the stock one back in. Thanks for everything White Rascal your knowledge has been extremely helpful!

Sounds like a lot of nonsense to me. I've had my system grounded to the chassis for 7 years now as well as every other car I've ever owned and I have never had any problems.

You can keep the steering wheel controls by using a PAC SWI-X and an HU that has an infrared remote control.
This is my HU. The dot below it is the infrared LED for controling the HU. The custom trim ring around the HU was made for me by Mike at F-Body Audio. He only makes then for Firebirds but I don't think he makes them anymore.