subwoofer into a stock euro deck

[EUR003act]

what LOC are u guys running?

im just using a cheap one (from jaycar) ive been meaning to disconnect it to find out whether its the LOC inducing the noise, but never really got around to it!

[lilwilliam]

could it be the input levels of the LOC??

[EuroDude]

I am using High Pass speaker inputs instead of a LOC and the hiss is there on both Amps. I tried a LOC (Stinger SALOC) and used RCA inputs but the hiss was still there, along with some dirty noise, popping when the engine fan cuts in, and bass distortion when the Honda HU volume is high, plus there's an electrical hum now. The Hiss is amplified if you turn up the Gain on the Amp, so if you use a LOC and increase its own Gain, then turn down the Amp's Gain, the hiss is minimized.


ps. I think I know why the Honda decks hiss, its because they are using a Balanced Tied Load (BTL) speaker output.

A normal Kenwood/Sony/Clarion/etc head unit sends audio signals through the Positive speaker wire, and an empty signal over the Negative Speaker wire.

A BTL Head Unit sends audio signals through the Positive speaker wire, but BTL sends the Negative Speaker wires the opposite of the Positive wire (180 degree phase). BTL increases the speakers power dramatically because the speaker is driven by the Positive AND Negative wires, instead of just the Positive. But can pose a problem due to the bridging/grounding system of the amplified channels.

To test for a BTL system, you get a multimeter and set it to AC voltage, then connect the Negative Probe to a Ground, and connect the Positive Probe to each speaker wire. A BTL system will give you fluctuating voltages on all the speaker wires, whereas a non-BTL system will only give you voltage on the Positive Speaker wires.

Some Amps may have a problem with BTL and produce noise.

[cutchorama]

I am using High Pass speaker inputs instead of a LOC and the hiss is there on both Amps. I tried a LOC (Stinger SALOC) and used RCA inputs but the hiss was still there, along with some dirty noise, popping when the engine fan cuts in, and bass distortion when the Honda HU volume is high, plus there's an electrical hum now. The Hiss is amplified if you turn up the Gain on the Amp, so if you use a LOC and increase its own Gain, then turn down the Amp's Gain, the hiss is minimized.


ps. I think I know why the Honda decks hiss, its because they are using a Balanced Tied Load (BTL) speaker output.

A normal Kenwood/Sony/Clarion/etc head unit sends audio signals through the Positive speaker wire, and an empty signal over the Negative Speaker wire.

A BTL Head Unit sends audio signals through the Positive speaker wire, but BTL sends the Negative Speaker wires the opposite of the Positive wire (180 degree phase). BTL increases the speakers power dramatically because the speaker is driven by the Positive AND Negative wires, instead of just the Positive. But can pose a problem due to the bridging/grounding system of the amplified channels.

To test for a BTL system, you get a multimeter and set it to AC voltage, then connect the Negative Probe to a Ground, and connect the Positive Probe to each speaker wire. A BTL system will give you fluctuating voltages on all the speaker wires, whereas a non-BTL system will only give you voltage on the Positive Speaker wires.

Some Amps may have a problem with BTL and produce noise.

So...

If it is BTL, what is the best way of having audio set up? Just keep +ve and -ve wires away from speaker cable/rca? Or is an after market HU the best way?

[EuroDude]

^ Well I am still looking into it, it may be caused by the BTL system being interrupted by aftermarket equipment. I am going to try filtering the noise by adding some 0.1uf Caps to the speaker wires. This will eliminate the HU wires from acting like antenna's.

[EUR003act]

your speaker wires shouldnt be showing ground to the cars chasis?!?!

[EuroDude]

Well thats the idea. But I tried connecting one of the speakers to ground (all other speakers were fully disconnected) and it just gave a loud static noise.

[EUR003act]

Well thats the idea. But I tried connecting one of the speakers to ground (all other speakers were fully disconnected) and it just gave a loud static noise.

dont connect speaker negative to the cars ground!! never! youll blow up the headunit/speaker!! same with RCAs (line audio) it should never be grounded to the car!

[EuroDude]

^ Thats correct for a normal car audio system, which is what Sony, kenwood, clarion, pioneer etc.. use.

If its a non-standard common grounded / BTL system, you can actually short the negative wire to ground. Speaker output wont be as powerful, but it should output sound.

[EUR003act]

^ Thats correct for a normal car audio system, which is what Sony, kenwood, clarion, pioneer etc.. use.

If its a non-standard common grounded / BTL system, you can actually short the negative wire to ground. Speaker output wont be as powerful, but it should output sound.

ive never tried it in a BTL system... but i know in a normal system if the headunits earthing isnt too crash hot, itll actually try and pull it negative ground through the speaker! not good...

[EuroDude]

ive never tried it in a BTL system... but i know in a normal system if the headunits earthing isnt too crash hot, itll actually try and pull it negative ground through the speaker! not good...

Yep Ive done that before in a Civic, doesnt sound to good lol

[cutchorama]

Just an idea...

Would a couple of diodes in the circuit help?

It will prevent current going both ways, not sure if this is healthy for the HU tho?