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Passive crossover design

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snowflake View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post 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
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DJ-Versatile Quote  Post ReplyReply Direct Link To This Post 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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Post Options Post Options   Thanks (0) Thanks(0)   Quote markie Quote  Post ReplyReply Direct Link To This Post 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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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post 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.


Edited by snowflake - 28 April 2016 at 5:58pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Modeller Quote  Post ReplyReply Direct Link To This Post 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

(Use 3 in parallel)

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

Monacor:

http://www.monacor.co.uk/categories/film-capacitors/vnr/112300/

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?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Andy Kos Quote  Post ReplyReply Direct Link To This Post 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.
just a guy with a warehouse and a few speakers... www.bluearan.co.uk
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DJ-Versatile Quote  Post ReplyReply Direct Link To This Post Posted: 28 April 2016 at 8:23pm
Thanks for your help guys! 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post 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
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DJ-Versatile Quote  Post ReplyReply Direct Link To This Post 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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Post Options Post Options   Thanks (0) Thanks(0)   Quote Modeller Quote  Post ReplyReply Direct Link To This Post 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?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post 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

2 of those in parallel.



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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 1:15am
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
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