basic car stereo questions - Drew20
help please
I have a four channel head unit, 4 three way speakers (one in each corner) and 2 tweeters (L and R at front). The speakers are already fitted in the car and the head unit is currently in my old car (which only had 4 speakers). How do I connect this into my new car?

I have been advised to connect the two front channels to a tweeter and a 3 way unit each in parallel but I have also read that this could lead to blown final stage transistors.

I have also been advised to connect the two front channels to a tweeter and a 3 way unit each in series but I have also read that this might lead to problems as the speakers connected in series will have passive crossovers wired in them and conneting in series would lead to frequency confusion at both speakers.
Is this correct? I confess to knowing nothing about car audio other than how to fit a chocolate block!!

would a suitable compromise be to connect the two front channels to a tweeter and a 3 way unit each in parallel but also connect a 4 ohm resistor in series with the parallel connections?

yours,
confused of kennington
basic car stereo questions - 3500S
Ignore the rears, they can run each off a separate channel.

The best way I've found for separate tweeters on the fronts is in series by using a passive crossover AFTER connection to the main front 3-way not before. There will be no frequency confusion. I've always done this with every set of fronts I've fitted and never had any problems.

I think running in parallel will not help the power output from the 3-way at all and it will place more current into the tweeter potentially overloading the output transistors.

You don't want those tweeters to dominate the front as they should really only fill the high-end sound you are losing from the front tweeter usually because the 3-way is at leg height in the front door.

Finally, if you are going to fit these speakers get some Dynamat to blank off the surrounding area of the speaker bracket, that stuff will do more for the sound quality of your stereo than any wiring decision you make.

basic car stereo questions - Drew20
yes I've no probs with the rears.

I think I'll rule out connections in parallel as I value my power tranistor. So, going back to series connections... how does fiting the the passive crossover after the tweeter help?
I think I've misunderstood but if in series then the tweeter, the crossover and the 3 way unit are all connected on the same loop, no? Does it make a difference in which order I connect the three components? And given the tweeters are currently connected to a head unit (to be replaced) will there be a crossover in the circuit already?

yes you're right about the 3 ways, they're in the doors, the tweeters are fitted in the back of the dash, just to confirm they are already fitted, what would I do with the dynamat?

thanks
basic car stereo questions - MikeyM
Is is possible for you to wire the separate tweeters in parallel to just the tweeters of the 3 way unit?
If you have access to the wiring of the 3 ways, then that would solve some of the impedance problems that would potentially damage your output transistors. You could also skip the passive crossovers on the separate tweeters as the crossover of the 3 way will do the job for both tweeters.




basic car stereo questions - Drew20
I like your thinking, I\'ve been looking at various options but that one hasn\'t been covered off yet.

As a related question, given that the tweeters and front 3 ways are currently connected up to the current head unit are there going to be passive crossovers already in there? There is no seperate amp in, all six speakers are currently driven by the 4 channels of teh unit.

the tweeters are a pink fluffy dice to get at as they\'re right underneath the windscreen and so you can\'t even get a stubby screwdriver on the retaining screws.
basic car stereo questions - MikeyM
The passive crossovers will be part of the 3 ways. They will be very simple,possibly just a single capacitor in series with the tweeter or mid range unit.
If you cant get to the separate tweeters very easily and cant bypass the passive crossover that is probably integral with the unit, it wont matter too much. Leave it there and connect it to the tweeter. Overall performance wont be affected too much.
If you have a multimeter, try measuring the impedance of the tweeter. You may find that its much higher than 8 or 4 ohms. If so, then it can easily be connected in parallel with the 3 way units with no fears of damaging the output stages. To be honest, this would only ever be a worry if you really wind the volume up. In case youre not aware, the reason is that if you connect two units in parallel it halves the impedance. eg 4ohm with 4ohm would result in a 2ohm load. This would try to draw twice the current from the output stages (ohms law applies voltage=current X impedance so half the impedance=twice the current). As it will only try to do this at very high volumes, unless youre a head banging reggae freak, it shouldnt be a problem. You can actually protect the amp by fitting the correct fuse in the power line.
basic car stereo questions - Drew20
Mikey,
I've poked around the door speakers and there is no way of getting to the tweeter contacts so can't use that plan.

I've also had a look at tweeters for sale, some of these come with high pass filters and some don't. Is there an obvious way of checking mine to see if there is one there (preferably without digging the speakers and wiring out of the dash). I have a fluke and was thinking the resistance of the unit would be much higher if there was a capacitor in series.

Yes I remember Ohms law from school, but another concern of mine is getting the balance right between the tweeters and the door speakers, ie I don't want the tweeter to be too dominating. I've come up with a few options (involving variable resistances in series with various parallel speaker configs) but need to know if I need to add a capacitor or wether the tweeter already has a dediciated filter in already, I kind of assume it must. I also need to know how a capacitor will affect overall impedance of the parallel circuit

cheers
Drew
basic car stereo questions - steve52
"Finally, if you are going to fit these speakers get some Dynamat to blank off the surrounding area of the speaker bracket, that stuff will do more for the sound quality of your stereo than any wiring decision you make."

Lets hear some more about Dynamat. Where do you place it and is it really worth it regarding sound quality?
basic car stereo questions - MikeyM
If your fluke can measure capacitance, then this is a fair way of checking to see if there is a passive in line with the tweeter. The capacitance with no filter present will be negligible, but with a cap in series will be noticeable (impossible to say what though, it varies enormously between speaker maufacturers but maybe 10uF?). Youre correct to assume that the resistance will be higher with a capacitor in line. Thats one reason why the impedance effect is considerably less if a filter capacitor is present. The fact that you may struggle to get a reliable impedance reading can be an indication of the presence of a capacitor. As the voltage is applied by the meter to get a resistance reading, the capacitor will charge and cause the reading to slowly rise (or fall). Reversing the polarity will cause the converse effect. If you see this characteristic, then a capacitor is present. Its only a little cap so the rise and fall effect wont be dramatic.
To get the balance right, try it firstly as it is. It may be fine. If not, then an in line potentiometer (variable resistor) will allow fine tuning. If you dont think that there's a capacitor already there and you want to add one, make it somewhere between 4.7uF and 10uF. Make sure the voltage rating is over 12 volts too!
These guide lines are all a bit vague and ignore all the formulae and calculations that you should do to get things exactly right. This is simply because, in practice, its best to try it and see. In the environment of a car with fairly basic speaker units, the best solution may be far from the theoretical ideal.
basic car stereo questions - Monaro
Sorry to hijack the thread - I felt this didn't deserve a thread of its own.
Where can I buy a blanking plate to fit over a radio single din socket that no longer has a radio in it? The local Halfords don't have them and I am struggling to find one.

Paul
basic car stereo questions - SteveH
I got one recently, had similar problems. local ICE specialist ordered one for me-£3. Same sort of places sometimes do fleet installs and have loads of spare blank plates leftover...
Scrappy's might have one.
 

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