How do I build a subwoofer cross-over ???

[stuparumihairadu]

hello.

I got my hands on a car amp.doesen`t have any bass bost, lpf etc.
only rca-input know from 400mv to 4 V
and a dyn gain knob max-min.

so i thought that I could get some tips on how to do a sub cross-over.
better still if I can make it with lest say 3 various levels...(ex. 400 hz- 600hz - 1000 hz something like this.)
It`s a 2 channel amplifier with bridged option.
I`m thinking that if I get tips one how to build one i`ll build 2 of them (for each channel).


I am sorry if I post in the wrong section.

Thank you and lets hope i`ll get this sorted out.

[carshateme]

There is a site that shows you how by DIY

http://www.diyaudioandvideo.com/Tutorial/Crossover/

There is also four post previously about cross overs if you look under forum search.

[TheBaronGroog]

A 6dB per octave crossover would just use a coil of the appropiate value, as linked by carshateme above. However, bass frequencies are much lower than 400Hz-thats midbass territory, you want to be looking at freqs of 100Hz and down. Also coils aren't used commonly for sub crossovers in car audio(power handling and cost/lack of adjustability)-you may be better off using an active crossover, most stereos over £100 will have HPF and LPF filters built into them now days.

[ODougbo]

Here is a good site, easy to use and car oriented. There are also crossover calculation “windows” for use. The site is pretty extensive with charts and diagrams also.

First Order Passive Crossovers, 6 dB per Octave

[ODougbo]

This site is also very good – self explanatory:
http://www.apicsllc.com/apics/Misc/filter2.html#second

[stuparumihairadu]

thnx a lot.


Got all the info I needed.Run once in the past with the same type of problem.forgot the websites doh....any how...

thx a lot for posting! once again this forum (for wich i am a newcommer) gave me up to date and speedy answers.

cheers to all of you and diyaudi...nr 1

[epa]

do you want an active or passive crosover?
passive crossover for a sub of 100 hz 12 db/oct needs a verry large coil and cap.
for active sub crossover something like this?

[carshateme]

Originally Posted by stuparumihairadu

thnx a lot.


Got all the info I needed.Run once in the past with the same type of problem.forgot the websites doh....any how...

thx a lot for posting! once again this forum (for wich i am a newcommer) gave me up to date and speedy answers.

cheers to all of you and diyaudi...nr 1

Its what the forums is for. Feel free to ask any other questions. A lot of experienced peopld on these forums. I'm just an entry.

[stuparumihairadu]

i`m thinking on something like this .And here is where i am asking if its posible?
In theory is the same as using a single coil for sub freq.
I wanna use a switching device to select freq. between lest say 100-200-300. (or someting like that).

could it work or should I use only 1 ?

The frec on whom the switch is switched to is in contact.and the others are off basically.

[ODougbo]

It's next to impossible to use a 6db passive crossover for a 100hz subwoofer. I guess you would get some results, although the inductor would be huge.

What impedance is the woofer?