i've been toyingaorund withthe idea of building a custom stereo using jaycar kit parts. i'm not looking for ultimate SQ because this is more of a learning experience.

my problem is i don't know how the jaycar ratings for x-overs work.
if you look at this: http://tinyurl.com/ls6uc (click on 'Crossover Datasheet' down the bottom)

i need to know which things i'd need for a low pass at 800hz and a high pass at 5000hz. (i don't know if i should go for 6db/octave or 12???)
in the diagrams it has 'L1' and 'C1'. does this mean i pick the 1.6mH coil from the 8 ohm 'L' column for an 800hz low pass and the 4uF cap (capacitor?) from the 'C' column for a 500hz high pass?
(this is for a 6db/octave slope)

if this isn't it, what bits do i need and should i go 12db/octave or 6db/octave?
is it possible to have a 6db/octave low pass and 12db/octave high pass?
when i have the bits, how do i connect them?

thanks in advance
chris

What are you trying to do with the crossover. Whats its purpose, what speaker(s) is it driving? Just out of interest, why those values? they seem a little odd.

Cant really answer the question about what slope/frequencies to use if we dont know why your using them ;P

Heres an example. Splits, can be high passed at, say, 130hz with a really shallow 6db slope and sound fantastic. A sub, might warrant a 24db/oct slope low pass filter (But a crossover that'd handle sub duties, would be huge). Just an example.

its not going to be in my car, just a little stereo thing for my room.
the speakers i planned on using were just going to be some cheap jaycar ones (would of liked to have gone with the response ones but can't afford it).
i planned to use an 8in woofer, 5in mid and a tweeter.
http://tinyurl.com/qjlvx woofer
http://tinyurl.com/pr4ds midrange
http://tinyurl.com/lvfr3 tweeter

i chose those crossover points as it thought it would let me run higher wrms through the tweeter.
the midrange xover points are 800hz and 4000hz, but its rated to 7000hz so i didn't think a 5000hz xover point would hurt it.
there are a few built xovers already done but i don't know which to choose. there's a $17 one http://tinyurl.com/jcmeu with 800 and 5000hz xovers but i didn't think 40wrms would be enough. it has a 6d/octave rolloff.
the other one http://tinyurl.com/j3zz7 has the same xover points but is rated to 65wrms and has a 12db/octave rolloff.

like i said, response ones would have been good but can't justify the price.
what kind of enclosure should they go in? i was thinking ported for the 8inch ones, sealed for the mids and a fiberglass pod for the tweeters on top.

You are better of going active, because to get a set of crossovers right you will to know the cars transfer function and need to use RTA to measure vehicle acoustics. Only then can you tailor a specific custom passive crossover to suit that particular car.


George
Adelaide Pro Sound

Dude if this is your first undertaking, I would suggest trying a 2-way setup first.
a) you'll be able to afford better drivers, as you wont be buying as many
and b) it will be easier to build a crossover for (and cheaper).

I'd even go so far as to suggest the Kevlar Splits and building boxes for them.
Might not be the be all and end all in speakers, but would be far easier to build then the 3-way you're suggesting, and dare I say sound better.

Failing that, check out Vifa drivers @ www.tymphany.com
They make quality drivers if you're prepared to pay a little more.

As for xover points, dont buy components because they're available. Buy components that suit your speakers. If you're unsure about them altogether, then perhaps the Kevlar Splits would be the better option as they come with the crossovers.


As for more info on crossovers, there should be a thread I started about my custom xovers. Has a fair bit of useful information in it that people have posted. Might be worth digging up (do a search for crossovers and fill out fury in the username field), as it could offer some assistance to you.

Cheers.

what type of speakers should i use if i go 2 way?
woofer/mid or woofer/tweeter or mid/tweeter?



are you talking about the jaycar kevlars? i thought they were for cars
with 2 ways will i get the full range of sound? this system will be without a sub thats why i planned to use 3 ways with woofers instead of 2 ways and a woofer.



i just thought buying ready made stuff would make it easier, and they were close to the speaker suggestions anyway.
i'll try the seacrh.
thanks for your help

Oh this is not about CAR AUDIO crossovers i take it?

If so my mistake i apologise.


George
Adelaide Pro Sound

Woofer and tweeter.


Yes... What makes you think car speakers and home speakers are different? In that price bracket anyway, you wont find much difference. Only when you move up in price range and quality, where companies actually throw money into R&D in to car-specific applications (think Rainbows "kick" drivers)...

The jaycar splits would work just as well in a ported enclosure as they would in car (if not better).



The speakers should happily go down below 100hz in a ported box tuned low. You will probably lack a little in the midrange/midbass as seems apparent with these speakers, but I think for a first project (and given the budget) it should be adequate.
Granted they wont replace a sub, neither would a dirt cheap 8" driver. Bigger size does not always mean better (just look at focals 5" sub, now that's a driver that can get low for what it is!).

If you're willing to take your time and search, there are DIY designs all over the net to suit any budget.
Many different designs can be found on the net... for this, but here's a relatelively cheap one for newcomers.
http://rzaudio.com/rz52/Drawing.htm
(the company is also based in NSW and you can purchase the components necessary from them)

no probs George.

Fury, i only thought that from something i read on the street commodore forum.

"Granted they wont replace a sub, neither would a dirt cheap 8" driver. Bigger size does not always mean better"

yeah i know that, i just thought with a bigger woofer and a midrange that it would go lower and would sound better than just using a woofer for low and midrange sound.
thanks for the link

if i was to go 2 way what size woofer should i get?

the ones i thought would be decent were the 6.5inch one:
Specifications:- Nom impedance: 8ohms- Power handling: 30watts RMS- Freq range: 49Hz - 4000Hz- Sensitivity: 87dB 1watt 1metre- Voice Coil Resistance (Re): 7.3ohms- Resonant frequency (fs): 49Hz

or the 8inch one:
Specifications:
- Nom impedance: 8ohm
- Power handling: 30 watts RMS
- Frequency range: 31Hz - 3500Hz
- Sensitivity: 86dB 1watt 1metre
- Voice Coil Resistance (Re): 7.4ohms
- Resonant frequency (fs): 39Hz

the 6.5 has a polypropylene cone, the 8 is paper cone. whichever one i pick will be used with response dome tweeters.

i was thinking the 6.5 because that has a higher freq range so would provide more midrange sound and the 8 inch one. i was thinking of using it with this:
2 Way Speaker Crossover 3.5KHz
- Crossover frequency 3,500Hz
- 12dB/octave rolloff
- 50 watts RMS
- 8 ohms
for $17 or so

good? bad? how is it going to sound?

I can't tell you how its going to sound, I havent heard the drivers, but for their price dont expect anything mindblowing.

I can sit here and rant and rave about what to get, but the best thing i figure for u to do is to get them and try them. It appears the best way you're going to learn is by doing it yourself.

yeah i realise $25 speakers are probably going to be crap compared to what else you can get. like i said they're just cheap things for my room though, in the family room i have a 5.1 jamo system which is absolutely fantastic but i can't always be in there.

i would really like something better, but i can't afford it ATM and don't really want to wait. i'm sure it would be an improvement from the 20mm speakers in my computer that i have now.

would the crossover i listed work with the woofers i put up? should i get the 8 in or the 6.5in?
thanks for your help

You might want to check this post out.

Also an off-the-shelf ready made crossover will, in most cases, not exactly suit the speakers you want to use.
A speaker rated at 8ohms nominal impedance may actually measure around 6ohms (DC resistance) and a 4ohm speaker could be around 3ohms.
Any changes in speaker impedance (resistance) will effect the crossovers corner frequency (the crossover point). To top it off impedance (in the case of a speaker) is also not constant. It changes with frequency. So in fact passive crossovers can be quite tricky things to get right.

However once you know the speakers characteristics, ie impedance, frequency response, efficiency etc. you can use a crossover calculator to obtain a more accurate result...

http://www.apicsllc.com/apics/Misc/filter2.html

is it hard to make the xovers?
if i went into jaycar and told them what i wanted, would they be able to give me the stuff to best suit it?


i made some 2 ways tonight, haven't had a chance to test them yet. i used prosonic speakers and crossovers which i bought for my car. the woofers are good but the tweeters (i think) are lacking, probably because they are only 13mm.
i built them in a box shaped like this: [ ]
/ ]
/____]
the tweeters are in the top, woofers in the angled part and all the wiring and xovers are on the inside.

What is your budget?

If you are doing this as a learning experience I'd say go ahead, but if it's only for some sound, I'd suggest looking for some second hand speakers.

With cheap drivers and missmatched crossovers(would be tricky to get right) You might find the money better spent on some used bookshelves. You could even look at cheap ones and spend some effort 'tweaking' them, ie making sure they are adequately braced, sealed etc

i don't really have a budget (don't have unlimited $$$ though) if it was 2 ways i'd like to come out of it at around $150 for drivers/xovers (got enclosure material already).
yes it is for a learning experience, but i'd like decent sound. if i was to use the cheap jaycar stuff and of the shelf xovers, what would the wrong xovers do to the sound, assuming they are reasonably close to the manufacturers suggestions?

i found a new speaker site which had much better stuff than jaycrap for half the price.
i tested the 2ways i made, sounded pretty decent but i think the tweeter needed to be further from the woofer (about 5cm apart-good or bad?).

if i was to make 3 ways, could i use two 2way xovers? with the splits i have the signal goes directly to the woofers, then to the xover which is set at 5000hz@12db/octthen to the tweeter.
could i have the signal go to an 8in woofer, then to a 1000hz or so xover, then a midrange speaker, then the 5000hz xover i have, then the tweeter.
i can't see how it wouldn't work, but i'd imagine there would be some kind of time delay.
also, if i make 3 ways, would it be better to go 8in, 6.5in, tweeter or 8in, 4 or 5in mid, tweeter?
cheers