Basic set-up; sub and head unit

[generae]

Hi all,
Everyone on this forum appears more knowledgeable than me, which wouldn't be hard!
Problem; I have a basic (cheap) 4x25W RMS output head unit (no sub-out) and recently wired a 600W max (maybe 200W RMS) subwoofer to it via the rear speaker circuit just before the HU and after a few weeks of use, suddenly no sound from the speakers at all, including the subby. HU still does everything it's supposed to do except no sound output. Power still going to the sub as the light is still on. No fuse issues. Wiring at the speakers and the sub and the back of the HU looks fine.

Rear speakers are 30 years old but front ones maybe 6 years. Car is a 1993 Saab 900 Turbo.
I am thinking that the amplifier in the head unit is blown because of the sub.

My current thought on a solution is to replace the head unit with one that has a sub-out.
An upgrade on this solution might be to get a HU that has RMS output greater then 4x25W as well as the sub-out but I'm not sure if this is necessary or would be of any benefit.

Any advice will be wonderful.

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[CarAudio.com - Hal AI Bots]

Hi all,
Everyone on this forum appears more knowledgeable than me, which wouldn't be hard!
Problem; I have a basic (cheap) 4x25W RMS output head unit (no sub-out) and recently wired a 600W max (maybe 200W RMS) subwoofer to it via the rear speaker circuit just before the HU and after a few weeks of use, suddenly no sound from the speakers at all, including the subby. HU still does everything it's supposed to do except no sound output. Power still going to the sub as the light is still on. No fuse issues. Wiring at the speakers and the sub and the back of the HU looks fine.

Rear speakers are 30 years old but front ones maybe 6 years. Car is a 1993 Saab 900 Turbo.
I am thinking that the amplifier in the head unit is blown because of the sub.

My current thought on a solution is to replace the head unit with one that has a sub-out.
An upgrade on this solution might be to get a HU that has RMS output greater then 4x25W as well as the sub-out but I'm not sure if this is necessary or would be of any benefit.

Any advice will be wonderful.

It sounds like you've been trying to push your head unit beyond its limits by wiring in a subwoofer without a dedicated line-out for such an application, which can definitely result in damage to the head unit over time. Let’s break down your situation and explore the best options for you.

### Diagnosis:
1. **Head Unit Output**: It’s quite likely that the internal amplifier of your head unit has been damaged, especially if you were pushing the limits of its output by connecting a subwoofer directly to the rear speakers. This can lead to clipping, which often causes damage.

2. **No Sound**: The fact that there is no sound to the speakers (including the subwoofer) suggests that the head unit may no longer be amplifying the signal.

### Solutions:
1. **Replace the Head Unit**:
- **Selecting a New Head Unit**: Look for a head unit that has:
- A dedicated subwoofer output (sub-out).
- Higher wattage output (ideally, 4x50W RMS or higher) to better suit your speakers and potential future upgrades.
- Built-in amplifier capabilities to ensure it can drive all speakers adequately.
- Features you find appealing (Bluetooth, USB, AUX input, etc.).

2. **External Amplifier**: If you want to retain your current head unit, consider:
- **Using an External Amplifier for the Subwoofer**: This would involve using a high-level to low-level converter which allows you to connect the speaker wires from the head unit to the amplifier. This way, you can drive the subwoofer more efficiently without overloading the head unit.

3. **Speaker Condition**: Since your rear speakers are 30 years old, they could also have degraded over time. If you replace the head unit, consider replacing or upgrading the speakers as well, especially if they are also underperforming.

### Recommendations:
- **Upgrading is Wise**: Given the age of the vehicle and components, investing in a new head unit and potentially new speakers could significantly enhance your audio experience without risking damage to equipment.
- **Test with a Multimeter**: If you have access to a multimeter, you might want to check if there is any output voltage reaching the speaker outputs of the head unit, which can confirm if the unit is functioning properly.

### Summary:
1. It’s very likely that your head unit is damaged, so replacing it is a good first step, especially with inherent upgrades that will allow for better overall sound.
2. Acquiring a head unit with a dedicated sub-out and higher RMS ratings will provide benefits in performance and could preserve the longevity of the new system.

If you need help selecting a specific model or have any more questions, feel free to ask!

 

[1aespinoza Premium Member]

Power still going to the sub as the light is still on.

I assume this means you have a powered subwoofer and you spliced in the high input harness from the sub into the speaker outputs. Generally this would not harm the radio since the high input presents a higher load than the speakers. Try disconnecting the subwoofer module for testing.

 

[Old_Slapper]

What brand HU do you have? What subwoofer do you have, and is it being powered by a separate amp?

 

[generae]

What brand HU do you have? What subwoofer do you have, and is it being powered by a separate amp?

The existing HU is probably beyond repair if its internal amp is kaput. It is a KDX R-03JBT. RMS 4x25W. Sub is an active one with its own internal amplifier, image attached. No separate amp.

 

[Mitchell Fosgate III]

Time for a new head unit upgrade. No sounds technically means bad speakers, bad head units, or bad connections. Electronics and technical term no sounds could mean many or any of the above. Irregular signal inputs and peak amplitudes causes no sounds. Volume. This is called a DC offset. 12 volts normally above zero, yet at irregular intervals. Old radio, junk speakers. Are the causes for a DC offset. Time to replace some components then.​