However I have a word of advice. You probably wants to replace the factory head unit with a good aftermarket. I say that because the factory unit is not good for subwoofers (as far as I know), and crutchfield says adding a new receiver is one of the first audio upgrades worth doing. So it's possible the Volvo head unit is not good for any bigger speaker upgrades. Don't wanna waste your money on good speakers and amp that are limited by a disappointing head unit.
But if you want to use the Volvo head unit with external amp, you will either tap into the speaker wires with Line Output Converter or use a custom plug adapter to get RCA outputs out of the HU-650.
I'm not too sure the point of adding an aftermarket amp That runs off of the stock head unit, because apparently stock head units can modify the audio signal in a way that makes it sound bad on aftermarket amps or limits their performance. Audio signal will be affected on both the speaker wires or the RCA outputs, which are possible with an adapter. Will be better off getting a good aftermarket head unit.
If you choose to use a custom 5-pin DIN adapter to get RCA outputs, you shouldn't use the built in amp anymore. The RCA output is only good for adding aftermarket amplifier to power your door and deck speakers, and it won't be good for a subwoofer. Reasons: 1. Using the adapter causes noise from the internal speaker amp making it unusable. 2. The RCA outputs are not meant for a subwoofer. My subwoofer doesn't sound very good on them. I may have done something wrong with my sub, but I've heard the subwoofer issue may be due to the Volvo head unit cutting out frequencies to optimize the sound for the factory speakers. And again Crutchfield says replacing the head unit / receiver is one of the first big audio upgrades you can do for a car.
You'll have to replace the head unit to get a good subwoofer sound, I'm going to assume that an aftermarket amp would be able to work with it to power "regular" speakers since the same signal was used for the stock Volvo amp.
Well, it's possible the hu-650 alters the audio signal in a different way than the HU850, which was always designed to run with an external amp.
Helpful overview of a typical subwoofer and amp installation:
Pre-requisites
I have the HU-650 radio, which is the lower end radio that has an internal speaker amp. With the HU-650. you'll need to make or buy a custom wiring harness if you want native RCA outputs or use a Line Output Converter tapping into speaker wires to create RCA outputs.
If you have the upgraded Dolby sound system which uses an amp under the passenger seat (HU-850), you can still add your own aftermarket amp but the wiring process is different and easier (as Metra produces commercial wiring harness/adapters) (explained at bottom).
For HU-650 or other Volvo radios with internal amp:
First, we need to get RCA audio output that your amp needs. To get RCA output, you either have to tap into the car's speaker wires (using something like Posi-Taps, speaker wire, and a Line Output Converter), or use a custom wiring harness to get native RCA outputs from the radio.
- Note: There are 4 speaker output channels provided by HU-650 (front left, front right, rear left, rear right). Each channel's volume/power output is individually determined by the radio fader and balance controls, important to know if you are amplifying a subwoofer as you shouldn't use just the front or rear channels (elaborated on later) or you'll likely have to boost the volume with a line driver.
- If using a LOC (Line output converter) to get your RCA outputs, tap into speaker wires anywhere you like. The speaker wires come out of the grey rectangular connector behind the radio, so you can tap into speaker wires there and hide your LOC (line output converter) behind the stock radio.
- Speaker output pin-out from HU-650 for tapping into speaker wires.
Source: http://victoriana.com/volvo-radio-hu-650-k.html
- I just tried it, and you can use the "antenna" wire for your remote turn on wire
- To get RCA outputs directly, an unused circular 5 pin connector behind the radio provides them.
Source: https://archiwum.allegro.pl/oferta/radi ... 85945.html
- You need to make a special wiring harness by soldering, using these parts: RCA wires, heat shrink tubing or electrical tape (to cover exposed wires), full-size 5-pin DIN male plug. You can also use some pins for a ground and remote turn on signal wire. Instead of making the harness, you may be able to buy a pre-made, homemade wiring harness from an enthusiast (if available). It doesn't look like a company manufactures this harness.
- What each pin of the wiring harness does, if you are building your own. [Just like how there are 4 speaker output channels (front left, front right, rear left, rear right), the wiring harness provides 4 RCA outputs for those channels.
Source: https://rally36.ru/foto/shema-magnitoly-hu-650.html
- The wiring harness will look like this, and the eBay listing I bought from was named Volvo Stereo Radio-Factory HU to Aftermarket Amp cable but is now unavailable.
- The seller https://www.ebay.com/usr/briang9525 had a lot of different Volvo radio harnesses for sale, not sure why they stopped selling.
- Warning: you may see Volvo radio harnesses on Amazon, e.g. Metra 70-9223, but the 5-pin cable that comes with them is a female connector instead of the necessary male plug. The Metra harness is not the right product to get RCAs from the HU-650.
Source: http://metraonline.com/part/70-9223
That is all you need to get RCA outputs. Simply plug the RCA plugs you obtained into your amplifier for use.
Warning about the speaker output channels
The speaker wires or native RCA outputs are separated into front and back channels, an issue for adding a subwoofer. For the subwoofer, you'd want full output power regardless of the radio's fader setting. If you use only the front or rear channels for the subwoofer, the fader controls can affect the subwoofer's performance. For a sub, I am guessing you'd have to combine the rear and front outputs together to a single output for left and right channel to get proper volume and performance from the subwoofer. But it seems equipment for that is expensive so I ended up getting a cheap $7 line driver to boost the RCA volume.
- Example: I used the front left and front right RCA outs for my subwoofer, but it doesn't sound good unless the radio is fully faded to the front speaker channels.
My speakers have a quiet whine, like a tinnitus whine when the engine is running after installing the wiring harness and amp/subwoofer. If I unplug the 5 pin wiring harness, it doesn't whine. I'm using the special 5 pin DIN adapter to get 12v turn on signal and RCA outputs to connect to my subwoofer. Not sure why the whine happens then.
Maybe the head unit is not intended to use both internal amp and the RCA outputs at the same time. (since the RCA outputs are probably meant to allow the internal amp to be bypassed entirely, like on the factory upgraded Dolby system. Technically, the Dolby system doesn't have an internal amp.) I think it's out of my scope to figure that out
Extra things to do while radio is out
If you live in a cold climate where you use the heater a lot, you should probably check behind the radio for air leaks from the HVAC ducts. There's a foam gasket directly behind the radio that disintegrate and allows HVAC air to blow onto the back of the radio. If it's hot air, I'm guessing that harms the radio.
Since it's likely a big pain to replace that foam, I would just cover the leaking gap with some foil HVAC tape to at least reduce airflow. Maybe add an insulating layer between back of radio and that HVAC duct area.
if you have the upgraded Dolby factory radio (HU-850) that has an external amp under seat
My understanding is that it is a slightly different setup than the HU-650. Your radio has the gray rectangular speaker output connector, but it's unused (in fact, I don't think it works at all on the HU-850 since there's no internal amp). The 5 pin connector is used by default, a wire snaking down to under the passenger seat carrying RCA signals to the external amp. Then the external amp sends speaker wires back up behind the radio. The speaker wires from the external amp plug into the rectangular gray wiring harness behind the radio to provide amplified speaker signals for your car. (if you had the HU-650, the speaker wires come directly from the radio as it has an internal amp)
To install your own amp, replacing the factory amp, you will probably buy the aforementioned METRA 70-9223 harness (5 pin female connector). Unplug the 5 pin male connector from the factory amp and plug it into their female 5 pin connector to get your RCA outputs for the aftermarket amp.
Then buy METRA 70-9221 which is an adapter to plug into the gray rectangular speaker wiring harness. http://metraonline.com/part/70-9221 Behind the radio, unplug the gray wiring harness from the factory amp and use Metra's adapter instead, then wire the adapter into the aftermarket amp. Or maybe you want to install completely new heavier gauge speaker wires, then just ignore the gray wiring harness and run your own speaker wire.
Since the factory amp is no longer used, you can unplug the power connector from it. (on a related note, that power connector is present even on Volvos that didn't come with the external amp)
Or you can modify these steps to keep the factory amp but add a new amp to power a subwoofer.
I'm not sure if an aftermarket amp would retain all the surround sound features, but Crutchfield says that if it's an analog external amp system it is plug and play for a new amp.
https://www.crutchfield.com/S-mEkmcshUn ... ystem.html
And as far as I know, the only connections going from HU-850 to its external amp are the 4 RCA channels, ground, and remote turn on wire. So that means that any amp can replace the factory amp, as long as it has 4 channels.
Thanks to Imgur for hosting the images!
