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Passive crossover design

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    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
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post 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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote haymere Quote  Post ReplyReply Direct Link To This Post 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
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post 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





Edited by Earplug - 19 April 2016 at 9:56am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Modeller Quote  Post ReplyReply Direct Link To This Post 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?


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 19 April 2016 at 5:44pm
Earplugs Are For Wimps!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Andy Kos Quote  Post ReplyReply Direct Link To This Post Posted: 20 April 2016 at 9:24pm
This is very close to being ready to launch for public use:


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:


it's all work in progress at the moment, feel free to contact me with any feedback/comments.




Edited by Andy Kos - 20 April 2016 at 10:44pm
just a guy with a warehouse and a few speakers... www.bluearan.co.uk
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Post Options Post Options   Thanks (1) Thanks(1)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post 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 ^^. 
Studio45 - Box Builder Commotion Soundsystem -Mobile PA
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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 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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Post Options Post Options   Thanks (0) Thanks(0)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post 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.
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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 3:57pm



Edited by Andy Kos - 28 April 2016 at 3:58pm
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 4:04pm
Thanks, i'll look into it now!
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