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Passive crossover design

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URL: http://forum.speakerplans.com/forum_posts.asp?TID=95547
Printed Date: 25 April 2017 at 1:31pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com


Topic: Passive crossover design
Posted By: Modeller
Subject: Passive crossover design
Date Posted: 19 April 2016 at 12:37am
Hello, I'd like to design a passive crossover for a modelling project I have underway at the moment.

I have two drivers, both with a limited acoustic range, but because of space constraints these are the only ones I can use. The bass/mid driver tails off dramatically at about 10kHz down to 13kHz and the tweeter starts at approx 2kHz to 20kHz. I'd like to have my crossover engage the tweeter at around 8-9Khz.

Is there a simple PCB design using standard components that I could build to these specs?

Any help you could give would be much appreciated.
Steve



Replies:
Posted By: Conanski
Date Posted: 19 April 2016 at 2:05am
There are all kinds of textbook crossover design tools on the web that will show you what component values are needed to generate your crossover. Designing a passive crossover that sounds good goes way beyond a basic crossover though, and that is because the acoustic result is the product of the output from the crossover and the speakers they are attached to which usually have a response that is far from textbook. And you may also want to consider the polar response(horizontal coverage) you want to achieve when selecting a crossover frequency, the response of low frequency drivers narrows to a beam in front of the driver at pretty low frequencies, a 15" beams above 1khz for example, a 12" at 1.2khz and that is why most PA speakers systems have relatively low crossover frequencies. If you don't care at all about off axis coverage then use whatever crossover frequency you want.. higher is better for high frequency drivers, I'm trying to make you aware of of the tradeoff you are making.


Posted By: haymere
Date Posted: 19 April 2016 at 6:38am
I want to do the same thing but a much more common scenario at say 1.6khz

Can you post some links

Also where is best to get quality components in the uk


Posted By: Earplug
Date Posted: 19 April 2016 at 9:55am
Take your pick:

https://www.google.es/search?q=crossover+design&ie=utf-8&oe=utf-8&gws_rd=cr&ei=vPEVV6jJOoGoa7iwk_AO#q=crossover+design+calculator

Smile





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Earplugs Are For Wimps!


Posted By: Modeller
Date Posted: 19 April 2016 at 1:10pm
Thanks Conanski and especially Earplug for the link.

Using the first link in the search it came up with a very simple crossover, attached below. This crossover links two 8 Ohm drivers at 8kHz.

My application is a very low fidelity project – we're not talking audiophile quality. The sounds I'll be reproducing are engine, mechanical and environmental sounds, rather than expansive musical tone, so this simple layout seems to suit my application.

One more question – where do I buy the parts?




Posted By: Earplug
Date Posted: 19 April 2016 at 5:44pm
Blue Aran:

http://www.bluearan.co.uk/index.php?id=CNVMPC25082_4PK&browsemode=manufacturer" rel="nofollow - http://www.bluearan.co.uk/index.php?id=CNVMPC25082_4PK&browsemode=manufacturer

(Use 3 in parallel)

http://www.bluearan.co.uk/index.php?id=CNVFCS016&browsemode=manufacturer" rel="nofollow - http://www.bluearan.co.uk/index.php?id=CNVFCS016&browsemode=manufacturer

Monacor:

http://www.monacor.co.uk/categories/film-capacitors/vnr/112300/" rel="nofollow - http://www.monacor.co.uk/categories/film-capacitors/vnr/112300/

http://www.monacor.co.uk/categories/air-core-coils/vnr/124760/" rel="nofollow - http://www.monacor.co.uk/categories/air-core-coils/vnr/124760/




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Earplugs Are For Wimps!


Posted By: Andy Kos
Date Posted: 20 April 2016 at 9:24pm
This is very close to being ready to launch for public use:

http://www.bluearan.co.uk/speakerwizard_design/Crossover_Designer.php" rel="nofollow - http://www.bluearan.co.uk/speakerwizard_design/Crossover_Designer.php

just chuck in what you want on the left, and it will tell you what need from standard parts.

If you're more interested in the technical side of things, try this:

http://www.bluearan.co.uk/speakerwizard_design/Crossover_Calc_v2a.php" rel="nofollow -


Posted By: studio45
Date Posted: 21 April 2016 at 1:10pm
The various wizards (that's a very good one by the way Andy, thanks!) make calculating your basic filters very easy, you shouldn't have any problems there. I charged right into the field that way before I even understood what an inductor does. However, all my first attempts sounded pretty terrible, even though I used the right filter components. It was this point that I realised there were several important things I had to understand, as well as the basic filters:

-L-Pads
-Asymmetrical filters (Highpass and lowpass at different frequencies) 
-Notch filters 
-Zobel networks
-Shelf filters (aka "baffle step correction")
-Series resonant filters to equalise HF response
-importance of proper winding technique (if making your own coils). 
-the differences between cheap and expensive capacitors, in terms of sound and longevity.
-Speaker dispersion and how it should influence choice of crossover point.

If you want to really understand, be prepared to read up on all or most of that ^^. 


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Studio45 - Box Builder Commotion Soundsystem -Mobile PA


Posted By: DJ-Versatile
Date Posted: 28 April 2016 at 3:28pm
Sorry to hi-jack this thread a little, but I have a question or two. For instance if i'm making a Sub and a full range box and wanted to HPF the sub at 35hz and LPF at 120 hz, then HPF the full range box at 120 hz. 

I would need to build 2 crossovers rated at 8 ohms with the above values to put in the dedicated box. Would the Amp then see 4 or 16 ohms? The aim is to get it to a 4 ohm load....

help me... my eyes have gone square from staring at the screen!


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If you are the smartest person in the room, you're in the wrong room....


Posted By: odc04r
Date Posted: 28 April 2016 at 3:47pm
When a passive crossover is working in its passband, it contributes effectively a zero resistance in series with the driver assuming no other eq etc is built in.

I advise getting LTspice and learning how to use it to sim crossovers with AC and transient analysis. Little bit of a learning curve but all the parts you need are as basic as it gets so drawing out the schematic is easy enough.


Posted By: Andy Kos
Date Posted: 28 April 2016 at 3:57pm



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just a guy with a warehouse and a few speakers... www.bluearan.co.uk


Posted By: DJ-Versatile
Date Posted: 28 April 2016 at 4:04pm
Thanks, i'll look into it now!

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If you are the smartest person in the room, you're in the wrong room....


Posted By: snowflake
Date Posted: 28 April 2016 at 5:24pm
Originally posted by DJ-Versatile DJ-Versatile wrote:

Sorry to hi-jack this thread a little, but I have a question or two. For instance if i'm making a Sub and a full range box and wanted to HPF the sub at 35hz and LPF at 120 hz, then HPF the full range box at 120 hz. 

I would need to build 2 crossovers rated at 8 ohms with the above values to put in the dedicated box. Would the Amp then see 4 or 16 ohms? The aim is to get it to a 4 ohm load....

help me... my eyes have gone square from staring at the screen!

use an active crossover with separate subs and tops


Posted By: DJ-Versatile
Date Posted: 28 April 2016 at 5:40pm
I always do usually, but i was wondering if there was a way to do it passively as the system i'm designing is meant to be as portable as possible without going active.  

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If you are the smartest person in the room, you're in the wrong room....


Posted By: markie
Date Posted: 28 April 2016 at 5:50pm
Passive crossovers on sub are rather inefficient, need huge inductors which add weight to the box and cause a worldwide copper shortage. Go active from sub to mid/top.


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If it's got wheels or tits it's gonna cost a fortune


Posted By: snowflake
Date Posted: 28 April 2016 at 5:57pm
use a LPF first and then split it to high and low. fit the crossover in the top box so they can be used alone.

you will need huge components to do even the 120Hz crossover passively. the 35Hz HPF is better done by an amp or crossover with an active filter.


Posted By: Modeller
Date Posted: 28 April 2016 at 6:56pm
Originally posted by Earplug Earplug wrote:

Blue Aran:

http://www.bluearan.co.uk/index.php?id=CNVMPC25082_4PK&browsemode=manufacturer" rel="nofollow - http://www.bluearan.co.uk/index.php?id=CNVMPC25082_4PK&browsemode=manufacturer

(Use 3 in parallel)

http://www.bluearan.co.uk/index.php?id=CNVFCS016&browsemode=manufacturer" rel="nofollow - http://www.bluearan.co.uk/index.php?id=CNVFCS016&browsemode=manufacturer

Monacor:

http://www.monacor.co.uk/categories/film-capacitors/vnr/112300/" rel="nofollow - http://www.monacor.co.uk/categories/film-capacitors/vnr/112300/

http://www.monacor.co.uk/categories/air-core-coils/vnr/124760/" rel="nofollow - http://www.monacor.co.uk/categories/air-core-coils/vnr/124760/


Much appreciated Earplug. Are these available any smaller? I have just a few millimetres to cram all this in. Is there are simple variable crossover on a chip available?


Posted By: Andy Kos
Date Posted: 28 April 2016 at 7:13pm
Originally posted by Modeller Modeller wrote:

I have just a few millimetres to cram all this in. Is there are simple variable crossover on a chip available?

Not in passive format, only active.

Thing is with passive components they need to be a certain size in order to handle the power levels.

An active crossover does this at line level (before the amplifier) where the power levels are minimal.


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just a guy with a warehouse and a few speakers... www.bluearan.co.uk


Posted By: DJ-Versatile
Date Posted: 28 April 2016 at 8:23pm
Thanks for your help guys! 

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If you are the smartest person in the room, you're in the wrong room....


Posted By: snowflake
Date Posted: 29 April 2016 at 10:47am
if u r worried about portability it is worth considering that the weight of two or three huge inductors is possibly more than a 1U active crossover


Posted By: DJ-Versatile
Date Posted: 29 April 2016 at 11:09am
Originally posted by snowflake snowflake wrote:

if u r worried about portability it is worth considering that the weight of two or three huge inductors is possibly more than a 1U active crossover

Crikey! OK, I've had a little redesign and know where I am headed with it now.

Thanks for everyones help as always!Thumbs Up


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If you are the smartest person in the room, you're in the wrong room....


Posted By: Modeller
Date Posted: 29 April 2016 at 1:46pm
Originally posted by Andy Kos Andy Kos wrote:

Originally posted by Modeller Modeller wrote:

I have just a few millimetres to cram all this in. Is there are simple variable crossover on a chip available?

Not in passive format, only active.

Thing is with passive components they need to be a certain size in order to handle the power levels.

An active crossover does this at line level (before the amplifier) where the power levels are minimal.
Thanks Andy, but I only have 3-5 Watts in my system. Is there an alternative, less precise way I could adapt to use as a low power crossover?


Posted By: Earplug
Date Posted: 29 April 2016 at 5:35pm
You could try lower power/voltage components, eg:

http://www.digikey.com/product-detail/en/wurth-electronics-inc/74458303/732-3931-2-ND/3316515" rel="nofollow - http://www.digikey.com/product-detail/en/wurth-electronics-inc/74458303/732-3931-2-ND/3316515

2 of those in parallel.





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Earplugs Are For Wimps!


Posted By: Modeller
Date Posted: 21 April 2017 at 1:15am
It's been a while from when I originally posted this (the model world moves very slowly...) but I've got some details on the amp I'm tied to using.

As I said in a previous post, this is for model sounds, so high fidelity is not a key requirement, but separating the frequencies is quite important.

The amp is 3W at 4-8Ohm. I'm going to be using 3 drivers (1x sub, 2x mono mid/high). I need to build a passive crossover to suit and select the drivers most suitable within these limits. Any help with the crossover would secure my gratitude for life!

Cheers, Steve


Posted By: Earplug
Date 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~" rel="nofollow - 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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Earplugs Are For Wimps!


Posted By: markie
Date 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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If it's got wheels or tits it's gonna cost a fortune


Posted By: Modeller
Date 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.


Posted By: snowflake
Date 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.


Posted By: Modeller
Date 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


Posted By: odc04r
Date 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" rel="nofollow - http://sound.whsites.net/lr-passive.htm


Posted By: markie
Date 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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If it's got wheels or tits it's gonna cost a fortune


Posted By: Earplug
Date 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.




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Earplugs Are For Wimps!


Posted By: Earplug
Date 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" rel="nofollow - http://forum.speakerplans.com/newbie-essential-reading_topic14681.html




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Earplugs Are For Wimps!


Posted By: Modeller
Date 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.


Posted By: markie
Date 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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If it's got wheels or tits it's gonna cost a fortune


Posted By: odc04r
Date 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



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