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Passive crossover design

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Earplug View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 21 April 2017 at 11:34am
For what you´re trying to do, just use a 2-way passive and then add a piezo tweeter. No need to complicate this any more.

Or better, just use this:

http://www.ebay.com/itm/DC-5V-20W-2-1-Dual-2-Channel-3D-Surround-Digital-Stereo-Class-D-Amplifier-Board-/172625385634?hash=item28314658a2:g:LVIAAOSwU8hY8Nz~


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markie View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote markie Quote  Post ReplyReply Direct Link To This Post Posted: 21 April 2017 at 1:07pm
I've often looked at these 2.1 amps but they never seem to mention any filter frequency for the sub output. Do they have a filter? Or are you supposed to be clever enough to work one into the circuit somehow.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Modeller Quote  Post ReplyReply Direct Link To This Post Posted: 21 April 2017 at 1:33pm
Thanks Earplug, but this is way too big for our application. I was hoping somebody could specify components specific for our needs.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 21 April 2017 at 2:01pm
Originally posted by Modeller Modeller wrote:

Thanks Earplug, but this is way too big for our application. I was hoping somebody could specify components specific for our needs.


if you aren't worried about high fidelity just run the mid driver full range - it will roll off by itself at some point and putting high frequencies through it won't do any damage. put a capacitor in series with the tweeter and change the value till the tweeter rolls off at approx the same place as the mids. even a decent polypropylene cap of the correct uF value will be pence rather than pounds.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Modeller Quote  Post ReplyReply Direct Link To This Post Posted: 21 April 2017 at 2:46pm
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
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Post Options Post Options   Thanks (0) Thanks(0)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 21 April 2017 at 3:19pm
There is no getting away from a little bit of measurement and maths required for best results vs least effort. Although just taking values directly from spec sheets would do it.

Read this page thoroughly first of all, it might answer quite a lot of your questions: http://sound.whsites.net/lr-passive.htm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote markie Quote  Post ReplyReply Direct Link To This Post Posted: 21 April 2017 at 3:21pm
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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 21 April 2017 at 3:29pm
Originally posted by markie markie wrote:

I've often looked at these 2.1 amps but they never seem to mention any filter frequency for the sub output. Do they have a filter? Or are you supposed to be clever enough to work one into the circuit somehow.


I´ve never actually used any of those, but I presume that they do come with the filters built in. The blurb seems to indicate that it does, but who knows. Maybe send the seller a question.




Edited by Earplug - 21 April 2017 at 3:29pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 21 April 2017 at 3:42pm
Originally posted by Modeller 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


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Modeller Quote  Post ReplyReply Direct Link To This Post Posted: 21 April 2017 at 5:15pm
No problem Earplug, if that's what it takes.

A previous question on this website helped us produce a debut model that won a lot of incredible reviews, so with that success in the bag I wanted the relationship to continue.

As we produce models that give very generous donations to industrial heritage charities (£12,500 so far), we need to keep costs down as low as possible, so asking the right enthusiastic people for as little financial outlay as possible is our aim.

We all have our specialities, but crossover design is not one of mine or my electrical engineer's, who is more geared toward drive and supply systems. In assisting (in more than just general terms) you will help donate over £10,000 to another charity preserving Britain's proud and pioneering industrial heritage, but I'm not forcing you to do that.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote markie Quote  Post ReplyReply Direct Link To This Post Posted: 21 April 2017 at 8:13pm
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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 25 April 2017 at 10:45am
Originally posted by Modeller Modeller wrote:

No problem Earplug, if that's what it takes.

A previous question on this website helped us produce a debut model that won a lot of incredible reviews, so with that success in the bag I wanted the relationship to continue.

As we produce models that give very generous donations to industrial heritage charities (£12,500 so far), we need to keep costs down as low as possible, so asking the right enthusiastic people for as little financial outlay as possible is our aim.

We all have our specialities, but crossover design is not one of mine or my electrical engineer's, who is more geared toward drive and supply systems. In assisting (in more than just general terms) you will help donate over £10,000 to another charity preserving Britain's proud and pioneering industrial heritage, but I'm not forcing you to do that.


That's all fine but part of a relationship is being honest. So you should have said it was a semi commercial design with charity affiliations in your first post, people wouldn't have minded but engineers are a cranky bunch at the best of times.

Anyways if your engineer knows what a Laplace transform is he can figure out a crossover. The design of plant control systems have a lot in common with crossovers in terms of a transfer function and its associated gain/phase.

You will have to provide quite a bit more data on your drivers etc if you want serious answers.

Edit: Because I can't spell sometimes


Edited by odc04r - 25 April 2017 at 10:46am
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