motorola hf850 and kenwood kdc mp443u

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dickw5000

Member - Posts: 7

Joined: July 07, 2009

Location: Australia

Posted: July 07, 2009 at 11:52 PM / IP Logged

Hi all,

yet another question about muting a handsfree. I've checked all of the posts and seen some info already. I have a new Kenwood KDC MP443U headunit and a Motorola HF 850 bluetooth handsfree. They are working a treat, the headunit is muted when I take a call. What it doesn't do is route the handsfree sound to the speakers (which my Nokia CK-7W does).

I'd like to toss the little under dash speaker that comes with the Motorola and route the sound to the driver's side door speaker. There is no external amp on the car audio.

I'm assuming I can't just cut the plug and cable off the external speaker and splice it into the drivers door speaker. Or can I? I've seen mention of using a relay to switch the speaker. I'm assuming I put the relay between the speaker wire and the handsfree, have it off and use the mute wire to close the relay. Is that correct? I'm assuming the mute wire triggers the Kenwood headunit to kill the signal to the speakers, so once the mute is activated there is no current in the speaker wires. Do I need to do anything else?

Thanks in advance, from Australia, Dick

dickw5000

Member - Posts: 7

Joined: July 07, 2009

Location: Australia

Posted: July 08, 2009 at 5:50 PM / IP Logged

Oh, and do I just use a standard 30amp horn relay???

Ween

Platinum - Posts: 1,364

Joined: August 01, 2004

Location: Illinois, United States

Posted: July 08, 2009 at 9:05 PM / IP Logged

hi,

it would be best to find a 12V DPDT (double pole, double throw) relay which will interupt both positive and negative speaker leads. the kenwood unit is high power, it won't take too kindly to having other electronics connected to it. using the relay will isolate it. look for a relay with a coil resistance of 100 ohms (higher would be better). the contacts of the relay should be able to switch at least 2-3 amps.

connect the common contacts to the speaker leads leading into the door. the normally closed ones to the kenwood radio. and finally the normally open ones to the hf kit. usually the terminals are in line (two rows) . make sure the positive and negative leads each connect to independent poles of the relay. this will make sure the speaker remains in phase when the radio is operating normally. the coil terminals of the relay will connect to 1. battery voltage and to 2. mute lead of the hf kit and mute of the radio.

hope this helps

dickw5000

Member - Posts: 7

Joined: July 07, 2009

Location: Australia

Posted: July 09, 2009 at 7:52 PM / IP Logged

Excellent! That makes sense. I've been to JayCar and got a Double-Pole, Double-Throw relay (12v/10Amp, and it's clear, so it's easy to see what goes where), for the princly sum of A$17. I'll install it on the weekend and let people know how it goes, but it looks really straight-forward.

Thanks :)

dickw5000

Member - Posts: 7

Joined: July 07, 2009

Location: Australia

Posted: July 13, 2009 at 6:13 PM / IP Logged

Oooooooo, it's so close!!!!!! I've hooked it all up, when a call comes in, the radio mutes, the sound is routed to the drivers door speaker. Sound quality is excellent, way easy to hear than the supplied "5w under the dash" speaker.

My only problem now is when I start the car, or finish a call, my headunit is in "Attenuation" mode, (silent/mute, where it is 20db less than before). Once touch of the volume knob and it kicks back to normal. I wasn't getting this with the supplied speaker.

Any clues, tips or suggestions?

Thanks in advance :)

Ween

Platinum - Posts: 1,364

Joined: August 01, 2004

Location: Illinois, United States

Posted: July 13, 2009 at 7:30 PM / IP Logged

hi,

some testing for diagnosis:

if you remove the power feed from the relay, does the headunit 'unmute' properly? if it does then i think two diodes will solve your problem. acquire two 1N4001 or equivalent diodes. connect the banded ends together and connect those to your hf kit. connect the other ends of each of the diodes to the relay coil and the mute lead of the headunit.

dickw5000

Member - Posts: 7

Joined: July 07, 2009

Location: Australia

Posted: July 13, 2009 at 9:26 PM / IP Logged

Hi Ween,

yes, if I disconnect either the power feed OR the mute wire from the relay, the radio works as expected again.

I'll get some diodes and see how I go.

Thank you :)

dickw5000

Member - Posts: 7

Joined: July 07, 2009

Location: Australia

Posted: August 18, 2009 at 6:00 PM / IP Logged

Woo hoo!!! I finally got around to adding the diodes to the circuit and it works a treat!!!! Up until now I just had 3 speakers hooked up to the car audio, and the drivers door speaker hooked to the handsfree, which kinda felt like I had a blocked ear all the time.

I added two diodes, each of the handsfree mute wire, one to the car audio and one to the relay. I now have all four speakers hooked to the car audio, and the drivers door speaker is hooked to a DTDP relay and the handsfree mute trips it to route the handsfree speaker output to the drivers door speaker. When I end the call, the handsfree unmutes the car audio and sound returns to all 4 speakers.

I am very happy. Many thanks to Ween.

danschwarz

Member - Posts: 3

Joined: October 27, 2009

Location: New York, United States

Posted: October 27, 2009 at 10:02 AM / IP Logged

Great thread- I'm trying to do the exact same thing with my HF 850, connecting to a Blaupunkt RDM 168. I want to do as clean an install as possible and avoid cutting the Motorola HF 850's speaker wires off. Anyone know where I can source a replacement speaker wire connector that will fit the HF 850?

Also, I'm not too clear on the directions for installation of the diodes. Exactly what connects to each end of each diode? Thanks for clarifying!

danschwarz

Member - Posts: 3

Joined: October 27, 2009

Location: New York, United States

Posted: October 27, 2009 at 2:34 PM / IP Logged

I wonder if one of these harness adapters would work well instead? My Blaupunkt head unit has a mute wire - will this serve in place of the relay setup, or do I still need the relays given that the HF 850 is only providing speaker level outputs?

They also sell a more complex adapter and a relay box that probably work just like the DIY relay shown above.

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