Adjustable Passive Crossover?

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Hey all,
Are there any "adjustable" passive crossovers out there? The only one I could come up with is this guy, but it's a but more than I wanna spend.

http://www.vidsonix.com/vidsonixnew/boxlit2.pdf

Thanks!
With bipolar capacitors and switches it would not be to expensive, only coils will be and high cost.

serie coils you can ad the value parallel them L=1/(1/L+1/L)
capacitors parallel you can ad the value series C=1/(1/C+1/C)

Why make it this difficult, just calculate the XO. And buy a big coil then unwind the to big coil to the right value. You need to measure the value with a LCR meter. Or buy 3 coils one almost the right value and two small ones who you can place in series and paralel lets say 3mH and two 1mH. Then you can make 0,42mH 0,5mH 0,75mH 1mH 1,75mH 2mH 3mH 3.5mH 4mH 5mH .

buy not the calculated capacitor but parallel small ones to the right capacitance so you can remove rome and have smaller value or bigger when adding more capacitors.
 
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With bipolar capacitors and switches it would not be to expensive, only coils will be and high cost.

serie coils you can ad the value parallel them L=1/(1/L+1/L)
capacitors parallel you can ad the value series C=1/(1/C+1/C)

Why make it this difficult, just calculate the XO. And buy a big coil then unwind the to big coil to the right value. You need to measure the value with a LCR meter. Or buy 3 coils one almost the right value and two small ones who you can place in series and paralel lets say 3mH and two 1mH. Then you can make 0,42mH 0,5mH 0,75mH 1mH 1,75mH 2mH 3mH 3.5mH 4mH 5mH .

buy not the calculated capacitor but parallel small ones to the right capacitance so you can remove rome and have smaller value or bigger when adding more capacitors.

Easier said than done, I'm not an "internals" expert. lol
But i'm learning :)

Thanks for this!
 
A passive filter's cut-off frequency is dependent on load impedance. A two way speaker system including two woofers and two tweeters would give you three different crossover frequencies switchable at the speaker.

For the woofers, one woofer can be connected into the network and the other one left out, or the woofers can be connected in series or parallel. If the nominal impedance of each of the woofers is 8 Ohm, this gives you 8, 16, or 4 Ohms load impedance.

The switching of the pair of tweeters would be the same as that of the woofers.

When connecting in parallel, the voltage sensitivity would increase by 6 dB relative to the two other load settings. Compensating for that would make the set-up somewhat complicated, but if you can live with a 6 dB jump in that one case, the manual switching circuit isn't going to be too difficult to implement.

Unlike a L-pad, the above only allows for large steps in the crossover frequency, not at all close to an infinitely variable change. If you wanted something infinitely variable and passive, then that is probably relatively much more complicated and expensive.

Another possibility would be a ganged L-pads for each of a single woofer and single tweeter in a two-way system, except that you modify the variation of series and parallel resistance of each L-pad to increase or decrease load impedance.

My apologies if either of the two above proposals are the same as the vidsonix method (I didn't take a look at that yet).

Regards,
Pete
 
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Hey all,
Are there any "adjustable" passive crossovers out there? The only one I could come up with is this guy, but it's a but more than I wanna spend.

http://www.vidsonix.com/vidsonixnew/boxlit2.pdf

Thanks!

Did you want to have an adjustable crossover frequency adjustment as a permanent feature of a finished speaker system, or a temporary rig for settling on the best crossover frequency for a speaker?

I like the idea, so I'm just curious as to what you hoped to accomplish with it.

Regards,
Pete
 
Did you want to have an adjustable crossover frequency adjustment as a permanent feature of a finished speaker system, or a temporary rig for settling on the best crossover frequency for a speaker?

I like the idea, so I'm just curious as to what you hoped to accomplish with it.

Regards,
Pete

Yes, as a permanent feature of the speaker. I think it would have good advantages like driver swap outs and possible room adjustments, wall distance, etc.... IDK, something different... tired of the same ol :)
 
Rod Elliott shows that changing the impedance of either the woofer or the tweeter in a first order two-way series crossover network shifts the crossover frequency while the summed response stays the same. See http://www.sound.westhost.com/parallel-series.htm

So here is simple two-way system using a first order series crossover network that I believe should work. Assuming 8 Ohm impedance of the woofer, find a suitable matching tweeter of nominal impedance approaching 16 Ohm. That is probably difficult to find, in which case you are stuck with wiring a pair of 8 Ohm tweeters in series. Connect the tweeter and woofer in a first order series crossover network. Connect a 100 Ohm pot in-series with a 6 Ohm fixed resistor across the input terminals of the tweeter. Voila! You can now shift the crossover frequency by adjusting the pot.

Using parallel resistance across the tweeter's input terminals avoids the change of sensitivity of the tweeter that connecting a resistance in series with the tweeter would cause. You want to change the impedance of the tweeter rather than that of the woofer as the power loss is much less in the mid/ treble range compared to the bass/ mid range.

How much change of the crossover frequency will this cause? You've got me!

If I weren't involved with a bunch of other stuff now, I would try rigging up a system like this myself. Maybe sometime in the near future.

Regards, Pete
 
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Rod Elliott shows that changing the impedance of either the woofer or the tweeter in a first order two-way series crossover network shifts the crossover frequency while the summed response stays the same. See Series vs. Parallel Crossover Networks

So here is simple two-way system using a first order series crossover network that I believe should work. Assuming 8 Ohm impedance of the woofer, find a suitable matching tweeter of nominal impedance approaching 16 Ohm. That is probably difficult to find, in which case you are stuck with wiring a pair of 8 Ohm tweeters in series. Connect the tweeter and woofer in a first order series crossover network. Connect a 100 Ohm pot in-series with a 6 Ohm fixed resistor across the input terminals of the tweeter. Voila! You can now shift the crossover frequency by adjusting the pot.

Using parallel resistance across the tweeter's input terminals avoids the change of sensitivity of the tweeter that connecting a resistance in series with the tweeter would cause. You want to change the impedance of the tweeter rather than that of the woofer as the power loss is much less in the mid/ treble range compared to the bass/ mid range.

How much change of the crossover frequency will this cause? You've got me!

If I weren't involved with a bunch of other stuff now, I would try rigging up a system like this myself. Maybe sometime in the near future.

Regards, Pete


Interesting.... maybe I'll try that out
 
Hi,

They don't really exist because they will always be wrong.

So too will be adjustable active analogue crossovers and digital crossovers
with only preset functions and level controls. Only a fully flexible digital
crossover that allows any transfer function possible is more flexible than
correctly designing a passive crossover for the case in question.

rgds, sreten.

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Zaph|Audio
FRD Consortium tools guide
Designing Crossovers with Software Only
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Jay's DIY Loudspeaker Projects
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HTGuide Forum - A Guide to HTguide.com Completed Speaker Designs.
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Great free SPICE Emulator : SPICE-Based Analog Simulation Program - TINA-TI - TI Tool Folder
 

Hi,

Yes its very wrong, try getting it to emulate this excellent 3.5 way c/o design :

ZDT3.5-crossover.gif


Zaph|Audio - ZDT3.5

Or most of the designs on his site, some it can manage, but
only the simplest most straightforward ones : Zaph|Audio

rgds, sreten.
 
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