# Crossover question



## bruklyndodga (May 21, 2012)

I'm looking to do a simple HPF crossover for some small drivers around 100-150 hz, so when looking at impedance lets say I have an 8 ohm woofer & 8 ohm tweeter in parallel do I consider the woofer an 8 ohm or 4 ohm driver as far as selecting a cap for it? Thanks Jeff


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## robbo266317 (Sep 22, 2008)

The crossover isolates the two drivers even though they appear to be in parallel. A useful tool is the crossover calculator found here:- http://www.diyaudioandvideo.com/Calculator/XOver/

Use the Re value for the driver if you know what it is.


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## bruklyndodga (May 21, 2012)

So if you had 2 4 ohm woofers wired in series you would need separate caps for each woofer and they would be considered 4 ohm as far as the crossover is concerned? Also it wouldn't matter if they were wired with any other speakers you base crossover component selection based on the rates impedance of each individual speaker? I'm trying to over simplify it and start with an easy HPF then work my way up from there. Thanks Jeff


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## robbo266317 (Sep 22, 2008)

bruklyndodga said:


> So if you had 2 4 ohm woofers wired in series you would need separate caps for each woofer and they would be considered 4 ohm as far as the crossover is concerned? Also it wouldn't matter if they were wired with any other speakers you base crossover component selection based on the rates impedance of each individual speaker? I'm trying to over simplify it and start with an easy HPF then work my way up from there. Thanks Jeff


Two 4Ω drivers in series is treated as one 8Ω driver and you only need a single inductor for the woofer and a single capacitor for the tweeter.

Do you have the model numbers of the drivers you are going to use?

A typical circuit would be:-


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## bruklyndodga (May 21, 2012)

That was just an example to help me understand the concept, I'm making a little MP3 player/boombox for work and was going to use 2 of these in parallel http://www.madisoundspeakerstore.com/approx-3-fullrange/aurasound-ns3-194-16a-3-paper-cone-16-ohm/ along with a cheap Pyle tweeter http://www.pyleaudio.com/sku/PDBT18/375-Aluminum-Bullet-Titanium-Horn-Tweeter


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## robbo266317 (Sep 22, 2008)

You can do the same with two 16Ω in parallel to give 8Ω overall. 

If you chose those drivers you should crossover at around 3 kHz and you would need to add a level matching circuit as the tweeter sensitivity is 99dB and the midrange/bass is only 82dB.


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## bruklyndodga (May 21, 2012)

Wiring drivers together will increase their overall sensitivity right? But not enough to match the tweeter but would 4 drivers per channel get it close? Not sure how to figure it out myself, if not other than an L pad how would I go about matching them? Know of any links or anything with info? Thanks again


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## fusseli (May 1, 2007)

Sensitivity (dB/W) will increase for wiring together in parallel, but not in series.

A tip for getting "textbook" filters to work better is to add a Zobel filter to each section (per HPF/LPF). This helps to flatten the impedance of the driver, which makes the textbook filter much more accurate in implementation. As you will see if you checkout the spec sheets of your drivers, the impedance of a driver is far from constant yet a "textbook" filter is sized as if it were a constant value (like 4Ω). You can use a Zobel filter calculator to give you R and C values to use just like your other filter calculators.


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## robbo266317 (Sep 22, 2008)

On the same pages as the crossover calculator he has an attenuation calculator and probably Zobel networks as well. - http://www.diyaudioandvideo.com/Calculator/LPad/
It's a very simple circuit and easily implemented.


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## bruklyndodga (May 21, 2012)

Ok thanks for the help ill look more into it and if I have anymore questions ill be back lol. Thanks again


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## robbo266317 (Sep 22, 2008)

Feel free to ask any question, no matter how trivial you think it is, as we are here to help you out.
When you have a final configuration we will gladly offer comments or suggestions.

I look forward to seeing your project reach fruition. :T


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