Hello!

 

Another trip to the scrapyard another lucky find.These are 2 Hertz Speakers

 

 

 

 

I want to install them,but I have a question....why do I have 4 wires for each front speaker?They are joined 2 by 2 at the speaker terminal

 

2 feed the tweeters I think

You also (ideally) need the crossover unit
 
Hertz Dieci DSK 165.3

yes should be for the tweeters, look like component speakers so go back for the rest of the kit (tweeters) inc the crossovers if you can

These need to be amped really mate. They will run off your HU but they do require an external amp to be very honest. You can pick a good second hand amp up from Ebay for £50 and an amp kit for around £15.  You will be shocked at the difference an amp can make due to the levels in freq' it can drop to and that extra power will drive these so well.

I know ,you are right.But where I live I can't get an amp for 50 and for the moment I can't afford one

I tested them today on the car....wow!They sound great,I'm impressed.I don't really need an amp,but I need a crossover......and some spacers.

These mid/bass speakers should be running between 80Hz-400Hz, you dont want any higher than 400Hz coming from these.  I will have a hunt about for you mate as have loads of Car Audio around, if I can find any x-overs then you can have them for free.  

thank you very much,but I'm like 2000 miles away from UK

You don't have post?

yes,I do

IulianE, what type of headunit do you have - any chance it has a crossover in it ?

It a Pioneer DEH-2100UB ,I don't think it has

the manual says 'no'

These mid/bass speakers should be running between 80Hz-400Hz, you dont want any higher than 400Hz coming from these.  I will have a hunt about for you mate as have loads of Car Audio around, if I can find any x-overs then you can have them for free.  

Good luck finding a small tweeter that will genuinely reach down anywhere near as low as 400Hz...

 

I'm pretty certain they're designed to be crossed over at above 4kHz rather than .4kHz. That would be rather ridiculous unless running a 4" as a mid driver and using these purely for bottom end.

Says on that advert I linked to the cross is:

 

Crossover cut off - 3,5 kHz @ 12 dB Oct.

 

The advert claimed the freq response of the combined midbass+tweeter is 50Hz to 23KHz

 

So I guess you need find/make a crossover for between 50Hz and 3.5KHz

 

You need to find someone who makes custom crossovers really ...

It's pretty simple to make a 12dB slope crossover at a chosen frequency. You won't really be able to go below 3.5kHz for the crossover frequency as the tweeters will blow their tiny little minds.

 

Alternatively, since the mid/bass driver won't really be bothered by having the full frequency spectrum presented to it, you could just make a simple 6dB slope filter for the tweeter. Which is - just one capacitor.

So you think at the end I don't need a crossover?

For tweetets I'm using OEM from a Merc CLK ,they are superb,very crisp and warm,and I think it has a capacitor in it

 

 

If you are certain there is a capacitor connected, then it will be safe. But it would perform a lot better with a proper 12dB or better still 18dB slope filter at a frequency suitable for the CLK tweeter (without the capacitor that is currently inline)

just one capacitor.

 

How do translate this into selecting the right part from the RS (or similar) catalog ?

 

Never worked with analog audio electronics, and not found a good explaination of how you get from db to µf ?

 

eg I can read values from this table, but haven't really understood it enough to be confident in order a part from RS

Ahhhh, right, now dB to uF (for some reason I can't use ALT 234 to get the micro sign on this site!!!!!! It keeps going back to index) is irrelevant.

 

What 6dB (12/18 etc) refers to is the slope.

 

The crossover frequency is not a cutoff point, where frequencies above this (or below this) are stopped dead, the frequencies are attenuated gradually. Lets look at the bottom end. For a 6dB filter high pass filter you would simply place an inductor in series (which you simply interrupt either the + or - and place the inductor between the terminal and the feeding wire). Lets say we had an inductor designating the crossover frequency at middle C. On a 4ohm speaker you would need an inductor of approximately 2.45 milliHenries to create a crossover frequency around 261Hz(ish)  For each octave (for instance, middle C known as C4 which is 261.626Hz to the C one octave above that known as C5 at 523.251Hz) there will be a difference of 6dB. So if you had a crossover frequency of 261.626Hz (for arguments sake we will assume that the value of inductor is correct), the middle C will be exactly as loud as all other frequencies below it. C5, an octave above it will be 6dB quieter. C6, an octave above that (1046.502Hz) will be 12dB quieter than middle C and so on.

 

For a 6dB low pass filter (again the capacitor is simply in series with one of the tweeter feeds) it works much the same way. For 261Hz you would need around abouts a 153uF capacitor (which is whoppingly huge, btw) and the C3 an octave below C4 (middle C) would be 6dB quieter than middle C and everything above it.

 

However, a 6dB crossover filter is pretty basic, and doesn't really offer much protection to the tweeter. Crossover points have to be chosen carefully to a ) protect the speaker, and b ) try to keep an even overall frequency response. Ideally, individual drive units should be picked to complement each other, rather than just throwing things that you like the look of together. There are so many things that go into loudspeaker design, and quite often results can be surprisingly unpredictable, and far from desireable. A 12dB filter is of slightly more complicated nature, but offers much better protection, and power handling is improved as a result of drive units not having to produce frequencies that could easily damage them. This is not so much of an issue with low frequency drivers, since higher frequencies are less damaging in general, but tweeters are easily damaged by over excursion. Which can be caused by too much volume (voltage) causing the tweeter to move further than it can physically handle, or by too low a frequency forcing the tweeter to move slower, but further. Cooling is also compromised by this slower movement (caused by the coil emulating the lower frequencies).

 

 

I could go on and on for days about this subject, but for most people it is easier to find programs and tables with given circuits to calculate what is required for 12dB or 18dB slope filter crossover networks. Myself included most of the time. But I will tailor them for my own requirements, for sure. However, it has been a good few years since I've done any serious crossover designing, or speaker building.

I'll inwardly ingest that over my cup of tea