Need advice: 5ch amp with OEM speakers (Audi TT MkII)

[mageus]

I want to replace the HU on my MkII Audi TT with Bose amp and 12 speakers. New HU is JVC KW-AV60BT. I can't keep the OE amp with an aftermarket HU, so I bought a cheap 5-channel amp (RF R600-5). I'm keeping the OE speakers for cost reasons. These are the speaker connections in the stock harness that leaves the Bose amp:

- dash center tweeter (not gonna use)

- door 8" woofers, R+L (4 ohms)

- door 3.1" mid and dash 1" tweeter in parallel, R+L (2 ohms)

- rear 6.5" mid and 1" tweeter in parallel, R+L (2 ohms)

- 5.1" ported sub (2 ohms?)

7 channels. I like a little rear fill, and the kids like music when in the car. Here are some ideas:

- amp drives the door woofers, front mid/tweeters, sub, and skip the rear speakers

- amp drives the front mid/tweeter, rear mid/tweeter, and sub. HU drives the door woofers.

Can the HU's 20W RMS drive an 8" woofer?

- amp drives the door woofers and front mid/tweeters in parallel, the sub, and the rear speakers

Could I use a passive x-over to isolate the impedance of the combined woofer and mid/tweeters? In parallel they would give 1.33 ohm, but a proper x-over would present 2 ohms to the amp.

- amp drives the door woofers, front mid/tweeters, sub. Disconnect the rear tweeter from the mid (so the mid presents as 4 ohms) and drive it with the HU.

I'm leaning toward the last option. I'd split the front pre-out signal to both pairs of channels on the amp, disabling the HU front crossover (use the amp's high pass filter). I'd wire the HU rear speaker out directly to the rear mid, using the HU's high pass filter for the rear mids. I'd send the HU sub pre-out to the amp, and could use the HU's, the amps, or both low pass filters. Too bad the amp doesn't have a band-pass filter for the woofer.

Any thoughts?

No one knows the exact impedance of the stock speakers. I presume that the resistance obtained from an ohmmeter will be lower but close enough to confirm it?

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[Epic0318 10+ year member]

actually for the mids and the tweets you will need a crossover for them if the car doesnt already come with one which i think it should.

 

[mageus]

actually for the mids and the tweets you will need a crossover for them if the car doesnt already come with one which i think it should.

Both the HU and amp have high/low pass filters (but no bandpass). So, I need HPF for the front mid/tweet and rear mid, LPF for the sub, and a BPF for the front woofer. Here's my idea:

- At the HU set up a very low HPF for the front channel to define the floor of the woofer. At the amp set up a LPF for the woofer (it's ceiling) and another HPF for the mid/tweet (to raise their floor), thus creating a BPF for the woofer. The rear mid HPF is handled by the HU. The sub can be adjusted at either the HU or amp.

Do you recommend using the HU's x-over or the amp's x-over for the sub?

 

[Epic0318 10+ year member]

Both the HU and amp have high/low pass filters (but no bandpass). So, I need HPF for the front mid/tweet and rear mid, LPF for the sub, and a BPF for the front woofer. Here's my idea:
- At the HU set up a very low HPF for the front channel to define the floor of the woofer. At the amp set up a LPF for the woofer (it's ceiling) and another HPF for the mid/tweet (to raise their floor), thus creating a BPF for the woofer. The rear mid HPF is handled by the HU. The sub can be adjusted at either the HU or amp.

Do you recommend using the HU's x-over or the amp's x-over for the sub?

seems complicated. i would need a wiring diagram of the system. and i would recommend you try to set the sub xover with both.

 

[Louisiana_CRX 5,000+ posts]

What year is your Audi TT ...mine had a 61/2 mid and a seperate tweeter in each door...I reoplaced those with higher end componets...I didnt use the rear speakers or dash center tweeters and added a ported 10 in the rear...The system sounds really good...I eneded up using a Blaupunkt deck because it blended with the stock dash lighting had awesome EQ features and fit behind the factory radio cover. Another deck I tried would hit the power volume knob and couldnt close then I added a steering wheel remote to control the deck when the door is closed and radio hid from view

 

[mageus]

What year is your Audi TT ...

2012. With the full bose system (12 speakers).

I really just wanted to keep the OE amp/speakers since they're decent, but the amp gets its turn on signal from the CAN bus, not from the remote-on wire, so it's not compatible with aftermarket HUs. The JVC is a 6.5" screen DD unit with variable lighting, and customisable wallpaper. I got the Connects2 fascia replacement and their harness, which emulates CAN bus features including stock steering wheel controls.

Epic, here's the layout: