V8V Premium Audio Problem - Sub

[00aston]

So after owning the car for the last 12 months, its come to my attention that the subwoofer in the car hasn't been working this whole time, hence why I was wondering why the positive reviews about the Premium Audio.

Car was taken into the dealership for a service and they quoted 4 hours labour just to access unit and put everything back together. No repairs and no troubleshooting time included,

They did however report a fault in that the sub was in open circuit.

I'm hopeful that someone who has experienced this issue will be prepared to provide some guidance. I'll number my questions below for your convenience.

1. Is the sub located behind the passenger seat (RHD)?
2. Would replacing the sub with a factory replacement repair the issue?
3. Or would the amp powering the sub require replacement?
4. Best way to gain access to the amp powering the sub?
5. Best way to gain access to the sub?
6. Any aftermarket options when it comes to replacing the sub?

Looking forward to the responses.

Cheers

[Murph7355]

00aston said:

1. Is the sub located behind the passenger seat (RHD)?

Yes

00aston said:

2. Would replacing the sub with a factory replacement repair the issue?
3. Or would the amp powering the sub require replacement?

Depends why it's broken It could either be the speaker or the amp or the cables I would think...

I suspect you may have a bad connection at either end.

00aston said:

4. Best way to gain access to the amp powering the sub?
5. Best way to gain access to the sub?

Your best bet here is to download the workshop manual. It's not massively informative, but enough to get you going if you can wield a screwdriver. If you can't my advice would be to pay the 4hrs labour as it would be pretty easy to damage the interior

There's an order that panels need to be removed in and once you twig the logic in the design it's straightforward (though frustrating in places as so much has to be removed to get at what should be more readily serviceable parts). But there are plenty of sharp edged bits of metal and fiddly screws.

00aston said:

6. Any aftermarket options when it comes to replacing the sub?

The std set up is very good IMO. The main costs are likely to be in dismantling/reassembling so I'd personally just replace whichever part is broken with an OEM replacement.

[divetheworld]

Murph7355 said:

Your best bet here is to download the workshop manual. It's not massively informative

I had a look but couldn't find the sub assembly removal in the manual. There is a drawing in the parts book, not helpful.
If I recall, its a case of remove the lower rear shelf, remove aluminium extrusion (sharp, watch the leather) and 4x bolts for the sub. Two at the top and two like feet at the bottom front.
Something like that.

[00aston]

Thanks gentlemen. I'll make my way into the sub enclosure section this afternoon.

Whats are the methods to test the sub, such that how can I ascertain whether its the amp or sub? I do have a multimeter on hand that I purchased a few years ago.

Cheers

[divetheworld]

Multimeter on ohms. Test the sub. If it's open circuit then it's fubar.
You might find the sub is dual voicecoil. That means it has four terminals. You'll need to test both coils.
If your meter is accurate, you should see 4ohms per coil.

[00aston]

divetheworld said:

Multimeter on ohms. Test the sub. If it's open circuit then it's fubar.
You might find the sub is dual voicecoil. That means it has four terminals. You'll need to test both coils.
If your meter is accurate, you should see 4ohms per coil.

Will do.
I wouldn't have to remove the sub to check this, would I? Taking off the trim to gain access to the plug will suffice?

[divetheworld]

00aston said:

Will do.
I wouldn't have to remove the sub to check this, would I? Taking off the trim to gain access to the plug will suffice?

The multiplug is under the sub, on the right hand side as you look at it if I remember correctly. Sorry..

[Impasse]

They occasionally pop up on Ebay as the entire unit for £100-£200 if you're happy with a used item.

[00aston]

Ok so after a long ordeal I managed to remove the sub out to test the reading is approx 4 ohms per coil.

On the harness that connects to the sub, the 4 wires read as follows on the multimeter (in ohms set at 200):
-The Red and black red reads 16; and
-The Black and blue black reads 26.
(Not quite sure what this means).

After getting behind it I also found that the sub is working, but it's heavilymuted. Almost sounds as though it's not getting enough juice to power it up.

What are your thoughts?

[divetheworld]

00aston said:

Ok so after a long ordeal I managed to remove the sub out to test the reading is approx 4 ohms per coil.

On the harness that connects to the sub, the 4 wires read as follows on the multimeter (in ohms set at 200):
-The Red and black red reads 16; and
-The Black and blue black reads 26.
(Not quite sure what this means).

After getting behind it I also found that the sub is working, but it's heavilymuted. Almost sounds as though it's not getting enough juice to power it up.

What are your thoughts?

4ohms is bang on. Your sub should be fine. Just to be sure, hook it up to another source and play a tune through it. Keep the volume down incase there is a mismatch or no filter on your source. It should act like any normal speaker.

So......
From beginning to end, there can only be few culprits.
1. Source. The head unit isnt putting out sub frequencies (check sub output level in menu and in the EQ. settings).
2. The Sub amplifier is U/S (either an amp stage or a sub filter).
3. Sub is U/S (unlikely since your impedance test)
4. Broken wire from sub amp to one coil or common rail.

To find out, you'd need to test each part. Unfortunately the source outputs via MOST (optical) so you cant test the source easily. You can test the amp to a certain degree.
Best bet with limited test kit is to get your AVO out and put the tunes below on and measure the output of both sub circuits. Adjust the volume and see if you can measure the output voltage. Hook up the sub and measure current if possible.
You're looking for a strong output of the right polarity on both sub output pairs matching the frequencies of the test signal in the files below.

If you dont get it, its either wiring or sub-amp.


www.n90.ltd.uk/insecure/48 1-3 Octave Pink Noise A...
www.n90.ltd.uk/insecure/sub-test.zip

[00aston]

Advice is gold- thanks for the detail that you provided and the links. I'll measure the output voltage next.

When you say strong output, what sort of numbers are we talking? Which mode and # should the MM be in?

Edited by 00aston on Wednesday 13th July 18:14

[divetheworld]

00aston said:

Advice is gold- thanks for the detail that you provided and the links. I'll measure the output voltage next.

When you say strong output, what sort of numbers are we talking? Which mode and # should the MM be in?

Edited by 00aston on Wednesday 13th July 18:14

For a pretty close approximation, hook up your voltmeter to your speaker leads when you play that horrible track I posted (sub connected too). Use the equation voltage squared then divided by impedance.
For instance, if your voltmeter says 10 volts and you know your speaker to be 4 ohms then simply calculate 10 volts times 10 volts which is 100, then divide by the impedance 4 =25watts… Very simple!

Don't use this method to see HOW MUCH power your amp has when turned all the way up. You could bust the sub, that track is for max SPL competition use. It will exercise it well though.
Also it will not be accurate at all frequencies since the speakers impedance is not constant at all the frequencies.
Its a good measure to see if the output is dicked or not.

Mode doesnt matter as long as the sub is on.

Edited by divetheworld on Wednesday 13th July 23:08