changing resistances in crossed over systems to achieve more power to certain speaker

[skylineTT 10+ year member]

lolz..

sooo i'm pretty much wondering if it affects anything for me to run a lower impedance woofer on a crossed over system that i am trying to get more power out of. i have a nice set of kenwood cabinets and wanted to change the woofers to a lower impedance to feed them more power.

in simple circuits, the power will flow down the path of least resistance so if you have a 4 ohm speaker paralleled with a 2 ohm speaker, it should feed the 2ohm speaker 2/3 of the total power and the 4ohm speaker 1/3..

when things are crossed over though, how is all of that affected? i would like to add a lower impedance woofer and turn the gain up to give it more power and also balance out the power to the other speakers as well.

what's the deeze?

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[skylineTT 10+ year member]

I figure that as long as the final impedance isnt below my amps limit, it should work well. i just want to be certain that the crossover doesnt some sort of power limit or something. they are rated at like, 250w a piece or so and i want to run closer to 350 and feed most of that extra power to a different woofer.

 

[skylineTT 10+ year member]

well, i found that the crossovers do somewhat have a power limit due to the inductors and capacitors within the crossover. I am going to experiment with this and see how it works out. I believe the woofers in my cabinets are 8ohm single so i will try a 4ohm or 2ohm woofer to steal a lot of power so i can ramp it up on the gain and try to make it wang harder. now i just need to find a good woofer to use. Dayton?

 

[keep_hope_alive Premium Member]

The crossover point of a passive crossover is dependent on the impedance. Change the impedance and you change the crossover point. This is important since it will either overlap or create a hole in the response. If you change drivers' impedance you should change passive component values to compensate.

Some passives use zobel networks or pads that adjust the impedance seen by the amp, though usually on mids and tweeters and not woofers..

Making the woofers louder without compensation for The other drivers won't improve how they sound. If you don't like your speakers, buy or build new ones. also note, different woofers will perform differently in the enclosure. You'll want to get similar T/S parameters or run the design again with the new drivers to verify performance.

 

[skylineTT 10+ year member]

ahh crap, didnt think about the crossover point. i know that i can find a woofer that would perform well in the enclosure but that *****. is there a formula to calculate how much it will be affected by different resistances?

 

[keep_hope_alive Premium Member]

certainly is!

This covers 4 and 8 ohm, but you can see the relationship is linear. I found a 2 ohm table somewhere (or made my own table in excel)

Crossover Component Selection Guide at Parts Express

A 1kHz low pass (6dB/oct, inductor) for an 8 ohm woofer is a 500Hz low pass for a 4 ohm woofer, and also a 250Hz low pass for a 2 ohm woofer.

if you halve the impedance, you halve the 6dB/oct low pass crossover frequency. that's a big deal.

Conversely, a 1kHz high pass (6dB/oct, capacitor) for an 8 ohm woofer is a 2kHz high pass for a 4 ohm woofer, and also a 4kHz high pass for a 2 ohm woofer

if you halve the impedance, you double the 6dB/oct high pass crossover frequency. that's also a big deal.

this means for 12dB/oct (or greater slopes) the crossover is useless when the impedance changes since the cap and inductor have inverse relationships!

there are crossover component calculators available online. if you want to change the woofer impedance while using passive crossovers, you need to build new crossovers. and really, crossovers are unique to the speaker combination in order to achieve the flattest response based on component separation. that is what the Alpine Type-X crossovers do, allow for crossover point and slope adjustment based on driver placement and aiming.

 

[keep_hope_alive Premium Member]

I hope this was helpful and not discouraging.

 

[bubbagumper6 5,000+ posts]

At a bare minimum, you could modify the current crossover so you could lower the impedance of the woofer and keep the same crossover point. Just know, without modeling them your kind of shooting in the dark as far as the final sound but my guess is your not exactly an audiophile so you'll probably be satisfied.

 

[keep_hope_alive Premium Member]

yea, reusing the PCB for your current crossovers is handy, but then you no longer have a truly matched crossover. i'd rather leave that one as-is and build a separate one.

Parts Express sells blank 2-way and 3-way crossover boards.

 

[audioholic 5,000+ posts]

I hope this was helpful and not discouraging.

You bastard. lol

 

[keep_hope_alive Premium Member]

You bastard. lol

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[bubbagumper6 5,000+ posts]

yea, reusing the PCB for your current crossovers is handy, but then you no longer have a truly matched crossover. i'd rather leave that one as-is and build a separate one.
Parts Express sells blank 2-way and 3-way crossover boards.

I know it's not ideal, I was just trying to give him an easy way to reach a solution. If he doesn't want to put in the man hours to build/design a new crossover it would be easy to modify the old one which is better than just swapping the speakers...

 

[skylineTT 10+ year member]

I am somewhat of an audiophile but have never built my own crossovers before. I've heard SQ systems and i know acoustics and can pick out differences really well so if i was to just play around with parts swapping, i would be able to tell the differences without actually performing the calculations. I wouldn't know exact specs of course, but I would know what sounds okay or not okay. i guess i could hit up those calculators then try different parts to see if it is okay.

As of now, it sounds very balanced and smooth but I was wondering about all of this because I never see people doing it and it would seem to be a very simple alternative to building high dollar component cabinets.

I might end up buying some boards on PE and calculating which parts will give me right crossover points so that I could run more power. Seems to be the right way to go about it.