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Discuss problems you have had or are having with your Z4
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TomK
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Post by TomK » Sat Nov 23, 2019 8:57 pm

steve_naive wrote:
Sat Nov 23, 2019 7:52 pm
Pbondar wrote:
Sat Nov 23, 2019 4:53 pm
If you have the 676 mid range amp which you replaced with the head unit that has 4 by 50 watts, depending how your wiring harness works it could have pumped 50 watts into the tweeter as the original system drives the tweeter of its own channel without any capacitors as frequency determination has been done by DSP in the oem amp...so no wonder it glows..
Not sure about any of that.

I think my car came with the standard amp, hi fi system. I thought the Carver system was the one with DSP?

My harness is the standard harness that came with the car, I used an adapter to connect the new stereo.
If It's any help I have the standard 10 speaker hi fi system inc tweeters all removed from my car with known good amp. Not the carver dsp one but regular 10speaker.
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Post by ph001 » Sun Nov 24, 2019 4:47 am

Hmmm, well if there is no capacitor on the tweeter then the crossover must be done on the amp / old head unit and if you have bypassed that then there is full frequency range going to tweeter, hence the smoke.

You could of course buy your own crossover but personally I would just add a 10uF 63V capacitor in series. This will crossover around 4KHz which is about right. You can play around with values from the table below:

http://www.carstereo.com/help/Articles.cfm?id=1

If you pm me your address I’ll post you out a couple for free.
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Post by steve_naive » Sun Nov 24, 2019 9:58 pm

I've just read that the amp does have built in crossovers, so maybe the harness adaptor wasn't enough to address the issue.

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Post by steve_naive » Fri Nov 29, 2019 12:26 pm

Done a bit more digging and indeed, you cannot just wire in a new head unit if you have the 10 speaker system with amp (dsp or otherwise).

Really wish I'd known this before spewing 500 quid on a stereo. :D

Can I really just add a couple of caps to the two tweeters? Maybe even temporarily disable the tweeters?

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Post by Pbondar » Fri Nov 29, 2019 1:14 pm

steve_naive wrote:
Fri Nov 29, 2019 12:26 pm
Done a bit more digging and indeed, you cannot just wire in a new head unit if you have the 10 speaker system with amp (dsp or otherwise).

Really wish I'd known this before spewing 500 quid on a stereo. :D

Can I really just add a couple of caps to the two tweeters? Maybe even temporarily disable the tweeters?
I did try to tell you...you need to sit down with the respective wiring diagrams of the car and the head unit and work out properly what to do..

From what you said you did, the car and the amp it wasnt going to work properly IMHO...

BMW as well as others don’t make it simple to simply unbolt one unit and replace it with a non oem part..
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Post by ph001 » Fri Nov 29, 2019 2:06 pm

steve_naive wrote:
Fri Nov 29, 2019 12:26 pm
Can I really just add a couple of caps to the two tweeters?
...you really can. I wasn’t even joking.

To be fair to the OP, lots of other people (without the premium sound) have done this so you can be forgiven for thinking it was ok.
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Post by steve_naive » Fri Nov 29, 2019 5:32 pm

Pbondar wrote:
Fri Nov 29, 2019 1:14 pm
steve_naive wrote:
Fri Nov 29, 2019 12:26 pm
Done a bit more digging and indeed, you cannot just wire in a new head unit if you have the 10 speaker system with amp (dsp or otherwise).

Really wish I'd known this before spewing 500 quid on a stereo. :D

Can I really just add a couple of caps to the two tweeters? Maybe even temporarily disable the tweeters?
I did try to tell you...you need to sit down with the respective wiring diagrams of the car and the head unit and work out properly what to do..

From what you said you did, the car and the amp it wasnt going to work properly IMHO...

BMW as well as others don’t make it simple to simply unbolt one unit and replace it with a non oem part..
Didn't disagree with you, even if it looked like I did. What I meant was 'I don't understand all that'.

I'm still not sure whether the stereo is connected to the amp or not.

If not, I assume I can go down the route of adding crossovers to the tweeters. But if it is, and the amp is doing some crossover stuff of its own, then won't that affect the values of the caps I'll be wiring in?

In the meantime, I've disconnected the tweeters. Hopefully the other speakers won't explode??

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Post by Pbondar » Fri Nov 29, 2019 5:41 pm

Without the vin number and details of the adapter I couldn’t comment..but it would appear either the new headunit is driving the speakers directly or the headunit is overdriving the existing amp either of which could destroy tweeters

It’s relatively well know that if you overdrive an amp it starts to generate a wide and energetic set of harmonics, that energy by its very nature will burn tweeters out very quickly...

Having leant the hard way not to trust ‘standard’ bmw adapters on the E89 there’s no joy in seeing other people have issues as well..
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Post by steve_naive » Fri Nov 29, 2019 6:47 pm

Pbondar wrote:
Fri Nov 29, 2019 5:41 pm
Without the vin number and details of the adapter I couldn’t comment..but it would appear either the new headunit is driving the speakers directly or the headunit is overdriving the existing amp either of which could destroy tweeters

It’s relatively well know that if you overdrive an amp it starts to generate a wide and energetic set of harmonics, that energy by its very nature will burn tweeters out very quickly...

Having leant the hard way not to trust ‘standard’ bmw adapters on the E89 there’s no joy in seeing other people have issues as well..
I've PM'd my vin.

This is the connector:
https://www.halfords.com/technology/car ... r-ct20bm02

Any help greatly appreciated!

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Post by Pbondar » Fri Nov 29, 2019 7:34 pm

steve_naive wrote:
Fri Nov 29, 2019 6:47 pm
Pbondar wrote:
Fri Nov 29, 2019 5:41 pm
Without the vin number and details of the adapter I couldn’t comment..but it would appear either the new headunit is driving the speakers directly or the headunit is overdriving the existing amp either of which could destroy tweeters

It’s relatively well know that if you overdrive an amp it starts to generate a wide and energetic set of harmonics, that energy by its very nature will burn tweeters out very quickly...

Having leant the hard way not to trust ‘standard’ bmw adapters on the E89 there’s no joy in seeing other people have issues as well..
I've PM'd my vin.

This is the connector:
https://www.halfords.com/technology/car ... r-ct20bm02

Any help greatly appreciated!
Thnx I’ll look over this over the weekend for you..got the pm :thumbsup:
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Post by Pbondar » Sat Nov 30, 2019 10:40 am

Hello, I’ve looked at the details you sent me..you do have the 676 HiFi fitted

https://www.newtis.info/tisv2/a/en/e85- ... ut/llHlnwX

As a result you have the incorrect adapter when used standalone...

Your new head/amp is overdriving the old amp 676 so it’s likely that you fried the tweeters through overdriving it, causing harmonic distortion, creating n harmonics and frying the tweeters...

There isn’t a simple solution as you have a complex speaker set up as part of 676..

A possible way forward would be to insert some attenuation between the new head unit and the old amp with some inline audio attenuators aka resistors ..

https://www.amazon.co.uk/Rothwell-RCA-I ... B00B7383F8

I would suggest the 15db - 20db preferably 20db ones but it’s a bit suck it and see

You would have to put these in the adapter harness in line ..

Offering advice of this nature remotely is fraught with possible errors /issues but that’s my best guess on the way forward
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Post by steve_naive » Sun Dec 01, 2019 10:19 am

Pbondar wrote:
Sat Nov 30, 2019 10:40 am
Hello, I’ve looked at the details you sent me..you do have the 676 HiFi fitted

https://www.newtis.info/tisv2/a/en/e85- ... ut/llHlnwX

As a result you have the incorrect adapter when used standalone...

Your new head/amp is overdriving the old amp 676 so it’s likely that you fried the tweeters through overdriving it, causing harmonic distortion, creating n harmonics and frying the tweeters...

There isn’t a simple solution as you have a complex speaker set up as part of 676..

A possible way forward would be to insert some attenuation between the new head unit and the old amp with some inline audio attenuators aka resistors ..

https://www.amazon.co.uk/Rothwell-RCA-I ... B00B7383F8

I would suggest the 15db - 20db preferably 20db ones but it’s a bit suck it and see

You would have to put these in the adapter harness in line ..

Offering advice of this nature remotely is fraught with possible errors /issues but that’s my best guess on the way forward
Makes sense, will look into it.

Thanks!

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Post by ph001 » Tue Dec 03, 2019 1:09 am

The thing is though, if you are overdriving the amp into clipping it would sound awful. If you are getting good quality sound then I doubt its clipping. A 10uf 63v capacitor in series with each tweeter is probably all you need to do to get an acceptable solution but I’m not going to keep going on about it!
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Post by Pbondar » Tue Dec 03, 2019 10:06 am

ph001 wrote:
Tue Dec 03, 2019 1:09 am
The thing is though, if you are overdriving the amp into clipping it would sound awful. If you are getting good quality sound then I doubt its clipping. A 10uf 63v capacitor in series with each tweeter is probably all you need to do to get an acceptable solution but I’m not going to keep going on about it!
Hi ph001...if the output from the OE amp was broadband / flat then this is logical, in theory, the output has been processed by the amp to specifically segment the frequencies into their respective ranges for the relevant speakers..

Of course belt n braces is not bad as an engineer gaffa tape...what do you compute the cut off frequency and slope based on your suggestion?

There have been cases where harmonics have not been heard by the user but done rapid damage to tweeters due to the extended range of frequencies well above audible range..

Interestingly my after market amp has dire warnings about tweeter destruction due to either over driving the new amp and/or not having a suitable frequency roll off..
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Post by ph001 » Tue Dec 03, 2019 11:31 am

A 10uF cap will crossover a 4ohm speaker at around 4Khz and rolloff at 6db per octave.

Depends how teccy you want to get but the impedance of a tweeter is dominated by 2*pi*F*L so as the frequency rises, so does the impedance. I have never seen a tweeter damaged in practice by feeding it frequencies over 20kHz, despite the scare stories you might read on the web.
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