# old speakers use crossovers? capacitors?



## Cruzer (Jul 16, 2010)

so i was talking to my dad about audio and he has some old fisher svt-724 home theater speakers. he doesnt think they use a crossover(he has no idea, he has never taken the towers apart, he says its glued other than the front clip on grill/panel.)

if it doesnt use a crossover, what does it use? just capacitors?

if it doesnt use a crossover, why do todays speakers use crossovers?

these are questions he asked me and idk the answers. i guess he just so used to it being so simple. i mean he has subs and sets subsonic and lpf he isnt "old skool" or against anything, he just doesnt know everything


----------



## Robert_J (Nov 9, 2006)

> if it doesnt use a crossover, what does it use? just capacitors?


A capacitor is a first order, high pass crossover.



> if it doesnt use a crossover, why do todays speakers use crossovers?


Some don't but most do. Because a crossover is how you passively distribute the signal to each driver.


----------



## minbari (Mar 3, 2011)

depends on what kinda drivers it had. there is no rule saying that a woofer has to have a crossover on it. it wont hurt anything. if it has a piezo tweeter then it wont need one either.

most cheaper speakers I have opened have had crossovers on em, even if it was only a cap on the tweeters.


----------



## Cruzer (Jul 16, 2010)

Robert_J said:


> A capacitor is a first order, high pass crossover.
> 
> Some don't but most do. Because a crossover is how you passively distribute the signal to each driver.


have there always been crossovers? or did we start out with just capacitors?

did we go to full blown crossovers to have 2nd order, and more than just high pass filters?

the fisher speakers he has have a 3" tweeter, 4" midrange, and a 15" woofer


----------



## thehatedguy (May 4, 2007)

Those speakers aren't THAT old...lol.


----------



## Cruzer (Jul 16, 2010)

not all the questions are directed just at those speakers, im just asking for knowledge and to tell him as well


----------



## thehatedguy (May 4, 2007)

Sometimes companies will let a speaker roll off naturally without a cap or a coil on them...usually that's with a woofer in a 3 way setup or maybe the top side of a midrange to the tweeter. Like mentioned above, piezo drivers don't really need a component on them since they by nature will only turn on above a certain frequency.


----------



## zoomer (Aug 2, 2009)

Cruzer said:


> have there always been crossovers? or did we start out with just capacitors?
> 
> did we go to full blown crossovers to have 2nd order, and more than just high pass filters?
> 
> the fisher speakers he has have a 3" tweeter, 4" midrange, and a 15" woofer


crossovers are filters that have been around since the early days of telephony and audio. so yes. crossovers have been around for a long time. 
a single cap or a single inductor is a first order filter with 6db/octave slope. that means that an octave away (that is twice or half the frequency) the output is 6db down.. that my be still too much power going to tweeters. So a second order filter would have a cap and an inductor and give a 12 db slope. cutting off much quicker. This is all basic stuff that any speaker book would tell you.


----------



## thehatedguy (May 4, 2007)

1st order electrical, but could could add to the speaker's natural roll off to make a 2nd, 3rd, or 4th order acoustical filter.


----------



## zoomer (Aug 2, 2009)

thehatedguy said:


> 1st order electrical, but could could add to the speaker's natural roll off to make a 2nd, 3rd, or 4th order acoustical filter.


correct but now you are getting into the intricasies of speaker and crossover design and that is beyon what the OP wanted to know


----------



## thehatedguy (May 4, 2007)

True...sorry.


----------



## musicfan (May 31, 2011)

thehatedguy said:


> Sometimes companies will let a speaker roll off naturally without a cap or a coil on them...usually that's with a woofer in a 3 way setup or maybe the top side of a midrange to the tweeter. Like mentioned above, piezo drivers don't really need a component on them since they by nature will only turn on above a certain frequency.


Interesting. I just pulled apart a set of 3-way KLH outdoor speakers, and I was surprised to find the only visible filter component was a 3.3uf cap on the 1.5" *midrange*. The tweet leads were soldered to the woofer terminals--full pass! I guess those must be piezo tweets.

With that mystery solved, I can go back to scratching my head about the choice of cap on the mids. 3.3uf to a driver that measures 3.7ohms on the voltmeter, that works out to about a 12khz 6db lpf, does it not? Lots of overlap; not sure if that is a sonic strategy or just minimum protection for a cheap POS speaker!


----------



## prion (Dec 11, 2011)

To determine the actual crossover frequency for that driver you would need to test its impedance (resistance) at a specific frequency. That is to say, its dc resistance may not be the same as its resistance at 12kHz.


----------



## Cruzer (Jul 16, 2010)

zoomer said:


> correct but now you are getting into the intricasies of speaker and crossover design and that is beyon what the OP wanted to know


Doesn't hurt to expand on the original question. I knew all of what had been discussed other than how long crossovers have been around. I told my dad these things and basically created this to let others explain and have others in agreement with what I thought.

He agrees with everything said except he thinks 16 year old cabinets are old and someone said their not old lol


----------

