Passive crossover design

You sound like you have a pretty good idea of what you want. Conventionally the xover is the last part of the system to be built and installed but as you are at a premium with space I see why you are thinking about it now.

The best bet is probably keeping it simple. The bass driver already has a modest roll off due to its natural inductance. If you measure its impedance and do some simple maths you could double the roll off slope with an appropriately sized series capacitor.

Your problem is going to be that steeper filters for good sub/high separation require more passive components and complex design. Is it possible to apply active filtering before an amplifier? That might solve a lot of your problems and with surface mount parts an active xover could be made very small.

I think I'm getting a clue here....This isn't for a soundsystem, it's a scale model of some machine or other, and you're putting a very small set of speakers into it because you want it to make the same noises as the full-sized version?

You'll find people on here are very helpful, but you really need to give us more information.

1). How much room have you got to fit the amp and speakers.

2). How are you going to power it, mains or batteries.

3) What sort of sounds are you trying to reproduce.

Modeller wrote: Thanks Snowflake, but I'm afraid that means not a lot to me at the moment. If you could start from the basis I know nothing at all. I have designed my own cabinets in the past, but I've used off-the-shelf crossovers or salvaged units and bought drivers to suit. This is a ground up design and I'm free to choose components suitable. I need an unpowered unit that is very small – to fit in a model – that can separate the bass frequencies from the mid/highs at the point where the mid/high drivers are effective. How do I work out which components I need depending on the switch to the next driver? If, for example, I need the switch at approx 8kHz, what do I need to achieve that and what would the wiring diagram look like? I can then get it produced at my factory. Thanks in advance and apologies for my total lack of knowledge. Steve

If this is going to be some sort of commercial product, maybe you really need to find/hire someone to design the unit for you and get it done properly, rather than flapping around when you don´t seem to understand the very basics needed to get going.

You´ve already been given plenty of good advice on how to get this done. Maybe do some reading:

http://forum.speakerplans.com/newbie-essential-reading_topic14681.html

If you don't need high fidelity why not use a simple full range driver, which will eliminate the crossover entirely.

If you include a sub driver the necessary crossover components will inevitably be big.

If you want some extra high end then use a mid driver plus a piezzo tweeter. Piezzos don't need a crossover, just a  resistor in series.

Thanks Snowflake, but I'm afraid that means not a lot to me at the moment. If you could start from the basis I know nothing at all. I have designed my own cabinets in the past, but I've used off-the-shelf crossovers or salvaged units and bought drivers to suit. This is a ground up design and I'm free to choose components suitable.