deciphering my x-over need experienced help

[cmitch]

hey there
now that my exams are over i have time to make my speakers YAY!!!
i have three big problems though and need advice
1) the seller of the kit i bought gave me no dimensions on the box size just the capacity it has to be, how do i calculate the dimesions with max simplicity

2) the tweeter comes out really quiet (i tested all the parts) when hooked up to the x over, i am unsure why

3) there are two "inputs" on the cross over and this has weirded me out i have included pics please please help because i cant wait to start making these

thankyou for your support
curtis

[rabbitz]

1. If you know an internal volume then you can work out a box size. If they are 6.5" drivers, use an external width around 200mm, if they are 5" drivers, use a width of around 175mm. Space out the drivers vertically, with them just about touching, and add another 150-200mm or so for a preliminary height. The rest of the volume is the depth and probably be between 250-300mm. It's hard to say for sure as you haven't mentioned the volume and whether they are floorstanders or bookshelf. You also have to allow for the volume of drivers, vent etc inside the box when calculating the building volume.

2. You say you are not sure about dual inputs, so you might not be wiring correctly, or the L-pad may be attenuating too much. BTW, speakers sound very different outside the box.

3. The 2 inputs are probably for bi-wiring or bi-amping. If you are only going to use 1 amp, then run 2 sets of wires from the amp or get a bi-wire terminal like Jaycar PT3010.

This wouldn't be the kit from eBay with woofers better than Audax and a Vifa tweeter that's being sold for about $80?

I'd aske the seller and give the seller a serve as all that info should be supplied and gives kit sellers a bad name.

If you have major problems, send me a PM.

[Cal Weldon]

Originally posted by cmitch
3) there are two "inputs" on the cross over

That may, I say may be a 4 or 8 ohm taps. Some readymade XO's have that. Or it may be as rabbitz says. Can you draw the circuit for us?

[rabbitz]

Had a look at the eBay listing (I think that's it) and it mentions bi-wireable but only supplies a single terminal.

http://cgi.ebay.com.au/DIY-SPEAKER-K...QQcmdZViewItem

[Cal Weldon]

So the extra set of inputs is for bi-wiring?
ROTFL

[cmitch]

yes it is bi wirable i will post more pics so see if you guys can help with the problem of quiet tweeters

[cmitch]

here is the bottom of the xover?? can anyone help with this quiet tweeter problem??

[Cloth Ears]

Hi cmitch,

with regards the quiet tweeter, this is happening for both cross-overs, right?

Is it still as quiet when you disconnect the woofers and only play the tweeter?

Have you tried reversing the polarity of the tweeter (+ to - & - to +) as sometimes this is required with 2nd order crossobers.

Does it get louder if you short out the 2 resistors with some straight wire (it should)?

When you say really quiet, what exactly do you mean - that is, what are you listening to? Have you measured the output or is this just from listening to music? Does the tweeter only drop out around the crossover point, or is it quiet through it's entire range? Do you have a frequency sweep on CD to listen to (so you can work out where's dropping out from?

[rabbitz]

cmitch

These are a 3rd order electrical crossover and I think the speaker would be a MTM.... think they started life as a centre speaker.

I think you are only wiring into the woofers and not the tweeter at all. Joint the 2 input + wires (+ red + yellow) and the 2 input - wires (- black - black) and try again with the tweeter and the 2 woofers connected. Then connect your speaker wires to the joined inputs. This should solve the recessed tweeter.

Just observe the correct polarity.

As far as the box goes, I need you to send the information as requested in my email. Can't help if I don't have the info.

Another option is to check the guys previous listings and ask the winning bidders on how they went.

[rabbitz]

cmitch

Here's a suggested box for those speakers. A friend of a friend had some volume information and apparently a centre speaker. Have done a rough sketch for a floorstander to help you out.

The sizes are based on 16mm MDF and if you go larger, leave the inside sizes the same. Some bracing between the drivers wouldn't go astray as well as a brace to tie the sides together. Have a look in the wiki at the design and construction guide. In the gallery is some pics that show you some bracing.

Good luck with it as you should have all the info now to proceed.