Jump to content

Can Subwoofers Be Tapped Into Stock Bose Rear Amp?


QX4nicate
 Share

Recommended Posts

'02 QX4 - Completely stock bose system 

 

I know the right way to do this is to get a new head unit, amp, and subs that all work well together. But that's boring... And I don't want to spend the money on it right now. I plan to in the future however. 

 

Anyway for right now, I was looking at the stock rear amp a few minutes ago and it got me wondering if I could tap off the connector RR/LR speaker outputs somehow and take it into the +- inputs of the subs? I'm a fire alarm technician and I know with a fire alarm speaker system you can't do what we call a "T-tap" of the speaker wires so I imagine this works the same with car audio as it's the same concept.

 

So instead would I tap off the rear speakers' input terminals to 'continue the circuit'? Do they have output terminals? 

 

Found all the info I need as far as what terminal/wire does what, in the factory service manual. Just need a better understanding of how it all works. I've never installed subs before, nor an amp. 

 

I know wattage and resistance plays a role in what I'm trying to do but I don't know what's expected of these two dudes. 

 

Again this would just be temporary but if it works may be long term temporary. I'm really not looking to spend more than $50 on rigging this up. I'd like to do this as non-destructively as possible so that if it sucks I can undo it. 

 

Thanks! 

 

 

Link to comment
Share on other sites

I haven't looked at the back of the rear speakers, but there is no reason they should have output terminals. You can splice into the circuit anywhere between the amp output and the speaker inputs.

 

If you do this, don't use a true "t-tap" with the metal saddle that slices the insulation. They work terribly for speakers. There are a couple ways to do it, but my favorite way is to cut the wire and use a heat shrink butt splice wire connector. As you are crimping it in place, on one side run another pigtail wire out of it to act as a tap.

 

Another way is if you want to remove the speakers, and where the voice coil is wired and soldered, to go into the harness connector, you could put a dab more solder on, and solder on the pigtail there. But if you aren't an experienced solderer this way is more trouble than its worth. 

 

Connect that pigtail to a line output converter before you wire it into your new amp for the sub. Line output converters are a dime a dozen. Here is one. I've never used this particular one before.

 

https://www.bestbuy.com/site/metra-two-channel-line-output-converter-black/1265702.p?skuId=1265702

 

Edited by colinnwn
Link to comment
Share on other sites

If there was a good way to add subs for $50, there'd be a lot more people with subs!

If your plan is to piggyback the subs onto the existing speakers, that's gonna be way more current than the factory amp was built to take. If you disconnect the stock speakers and run those wires to the subs, that might work, if the resistance of the subs is the same as the resistance of the stock speakers. If the resistance is lower, again, that's more power you're trying to push through a system that was not built for this. Maybe you could get away with one sub if you bridged the two rear speaker channels (connect inputs and outputs so the two channels share the load), but I still wouldn't expect much from it, and of course it would mean losing your rear speakers.

If you get a proper amp to go with your subs, it'll want a line-level (not amplifed for speakers) input. On a proper install this would go to the RCAs on the back of the head unit. This is where the converter Colin linked comes in. Tee off the stock wiring, the converter drops that speaker-level signal back to line-level, to the amp, Bob's yer auntie. I'll bet you could tap into the line-level from the head unit to the amp instead, so you don't need the converter, but that would mean digging deeper and hacking up a part of the harness that would be more complex to put right if you wanted to go back to stock later.

Link to comment
Share on other sites

When I upgraded my audio system, I replaced the Bose head unit, speakers, and amp. I wasn’t looking for a competition sound system, just something a little better than stock. I did add a subwoofer. In order to save money and avoid losing cargo room, I shoehorned an Alpine MRP-F450 amp into the cavity where the OEM Bose amp used to live. I have the amp powering the front speakers, with the rear channel bridged to power the subwoofer, a JL Audio Stealthbox. The head unit powers the rear speakers.

 

As far as I’m aware, the stock Bose amp cannot be bridged to power a subwoofer. Besides, the Bose system is kinda strange anyway. The front speakers are amped in each door, and the rear speakers are driven by the amp behind the cargo panel. The head unit has no line-level output.

Link to comment
Share on other sites

I think I assumed too much in what the original poster was asking - in that the "sub" he was proposing to use was internally amplified or he knew he had to have a separate amp and just needed to tap into the speaker wires to get a line level output signal for it.

 

As XPLORx4 said, Bose systems are completely "non-standard" to typical car stereo components. Whereas most car speakers and amps for midrange and tweeters are 4 ohms, Bose amp/speaker combinations are generally 1 or 2 ohm, low-wattage, non-bridgeable design. The Bose pre-amp head unit to amp inputs typically run higher voltage than normal - 5 to 6 volts, though I think 5 volts is getting more common in aftermarket too. But for some reason Bose amps don't generally like to be driven by an aftermarket stereo even with a high volt pre-amp. I think it is an impedance mismatch, you get bad turn on thump, and sound clipping. Though I haven't ever researched those measurements. It's easier if adding an aftermarket headunit to use an adjustable line level converter to input to the Bose amps, and adjust it till it sounds good.

 

Subs happen to run 2 ohms generally, but need higher wattage than midrange speakers, to drive their large voice coils for the thump. To run subs you need either a sub specific single channel high wattage amp, or a 2 to 1 channel bridgeable amp that can drive the lower impedance. 

 

So using a line level converter off the rear Bose speakers, to get an input to the sub amp input is still valid. But you can't run an aftermarket sub directly off of a Bose amp in any way. You need to budget for a line level converter, sub amp, and sub - or- a line level converter and  internally amplified sub box. You could maybe do this with $50 using garage sale or Craigslist components, but you won't do it with new components.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...