# What happens when you use an active and passive crossover together?



## analogrocker (Aug 1, 2009)

I am putting together a simple 2-way set using a pre-made 2-way passive xover. The passive xover high passes the midrange at 500 Hz, 2nd order . However, I want to use my amp's built-in xover and send a 1.5 kHz, 4th order high passed signal to the passive xover. My question is: would the final output from the passive xover to the midrange speaker be a 1.5 kHz high passed signal, or would it be a 2 kHz signal (1.5 kHz + 500 Hz)?


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## smgreen20 (Oct 13, 2006)

It would be a 1.5Hz HP at 24dB/oct.


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## OldSchoolAudioandVideo (Nov 14, 2011)

analogrocker said:


> I am putting together a simple 2-way set using a pre-made 2-way passive xover. The passive xover high passes the midrange at 500 Hz, 2nd order . However, I want to use my amp's built-in xover and send a 1.5 kHz, 4th order high passed signal to the passive xover. My question is: would the final output from the passive xover to the midrange speaker be a 1.5 kHz high passed signal, or would it be a 2 kHz signal (1.5 kHz + 500 Hz)?


We are gonna need more info. From what you are telling me, I can assume the amp is a 2 channel and will be driving a pair of mids and tweeters.
If you use the amps xover and set it at 1.5khz then that passive xover will be useless cause anything BELOW that amps over setting will be unheard. Even the mids will play 1.5hkz. So, if you want to use a 2 channel amp with a pair of speakers you will have to do 2 things, ONE, use a passive crossover that cutes off the tweeters at 1.5khz or whatever high pass frequency the tweeters need. And usually the passives will cut of a mid so the mids stop playing anything higher than the cutoff of the tweeter. TWO you will then have to use your amps xover to cut off the mids so they dont play bass. Somewhere around 120hz.

If your amp has a lowpass cutoff that goes really high, which is unusual, you can actually use the amps xover to cut the mids off at 1.5khz so it dont play any highs. ANd then use the passsive xover on the tweeters so they wont play anything lower than 1.5khz.


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## analogrocker (Aug 1, 2009)

OldSchoolAudioandVideo said:


> We are gonna need more info. From what you are telling me, I can assume the amp is a 2 channel and will be driving a pair of mids and tweeters.
> If you use the amps xover and set it at 1.5khz then that passive xover will be useless cause anything BELOW that amps over setting will be unheard. Even the mids will play 1.5hkz. So, if you want to use a 2 channel amp with a pair of speakers you will have to do 2 things, ONE, use a passive crossover that cutes off the tweeters at 1.5khz or whatever high pass frequency the tweeters need. And usually the passives will cut of a mid so the mids stop playing anything higher than the cutoff of the tweeter. TWO you will then have to use your amps xover to cut off the mids so they dont play bass. Somewhere around 120hz.
> 
> If your amp has a lowpass cutoff that goes really high, which is unusual, you can actually use the amps xover to cut the mids off at 1.5khz so it dont play any highs. ANd then use the passsive xover on the tweeters so they wont play anything lower than 1.5khz.



What I'm trying to do is get around having to add another amp. I plan on running a 3-way system (8" midbasses, 5" midranges, and 1" tweeters). I want the 8s to play from 80 Hz - 1.5 kHz. From there the 5" midranges takes over. To get around adding another amp for the midranges and tweeters, I thought I would use a pair of pre-made passive crossovers. So I found a 2-way passive xover that high passes at 500 Hz/12dB for the midrange. But.... I want it to high pass over at 1.5 kHz/24dB. So what I plan to do is use the active xover on my amp before the passive at 1.5 kHz/24dB. I just want to make sure that the final xover HP frequency after the passive still remains at 1.5 kHz/24dB since I'm using these two xovers together.


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## OldSchoolAudioandVideo (Nov 14, 2011)

You got it all wrong man
You will need a 3 way passive xover.
The amp x-over will be set to high pass at about 80hz so the 8's dont bottom out. 
The passive would be like this

Highpass at about 250 or 350hz so the 8 will play midbass only.
Bandpass of 250 or 350 all the way up to at least 3.5khz so the 5" dont play bass or highs
High pass for just the tweeter so it plays just highs.
Your looking at about 100$ for a 3 way passive xover unless you can find one on ebay for cheap. But the MOST important part is to make sure the passive crossover is made for the SAME Ohm load as the speakers you will be using.
Ive made 3 way passives where every speaker was a different ohm load. 
These types of passive xovers cant be used on any speaker.

Looks like you got lots of research to do cause you are just starting out.
The frequencies you want to choose will not work well with drivers you want to use.
Tweeters are mint to work at very high frequencies. 1.5khz is very low for a tweeter and will sound bad plus burn it up in a short time.
You have 3 speakers. The passive xover will work with one speaker. a midrange. That 500Hz cutoff will be good for midrange ONLY. You still have to cut off the tweeters and that 8. You cant do that with just a passive 500hz crossover and a amp.

Crossovers DONT double up on each others cutoff frequencies when used together like you are assuming.
A 1.5khz and 500hz crossover doesnt make a 2000hz crossover.
If you want a 3 way with one amp you need to get a passive 3 way xover. Plain and simple no way around it..


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## analogrocker (Aug 1, 2009)

I don't need a 3-way passive. I am running the 8s active.

Let me explain....


I have a 4 channel amp and a 2 channel amp.

The first two channels of the 4 ch will be for the midbasses (high passed @ 80 Hz/24dB and low passed at 1.5 kHz/24dB - active). The other two channels of the 4 ch will be for the midranges and tweeters (active + passive).

The 2 channel amp is for my sub. 

I was going to use widebanders instead of the seperate midrange/tweeter combo but I am unable to mount the widebanders on-axis and yet remain stealth.




OldSchoolAudioandVideo said:


> Crossovers DONT double up on each others cutoff frequencies when used together like you are assuming.
> A 1.5khz and 500hz crossover doesnt make a 2000hz crossover.


OK, good. That's what I wanted to know.


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## OldSchoolAudioandVideo (Nov 14, 2011)

I still have no idea how you will get that 8 to play just mid bass with just the amps xover. You can make it play from a certain frequency ( lets say 500hz ) on down but will not beable to make it play the bandpass frequency of 80hz to 500hz .

you need have the PROPER passive xover
You DONT
When you connect the tweets and mids to the same channel and use the amps xover at 1.5khz, All you are doing is sending everything 1.5khz and HIGHER to BOTH the mids and tweeters.
You dont want that
So basically if you have a 4 channel amp and want a 3 way setup in the front
you will need
a bandpass xover for the midbass ( <running active at 80hz highpass and passive 500hz lowpass> channels 1-2 )80-500hz
A bandpass xover for the midrange ( <running active at 500hz highpass and passive 3.5khz lowpass> channels 3-4) 500 - 3.5khz
and a high pass over for the tweeters ( < running from passive high pass only > channels 3-4) 3.5khz

So basically your passive 500hz highpass xovers that you got is useless.


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## OldSchoolAudioandVideo (Nov 14, 2011)

This is also if you actually have a amp that can even high pass at 500hz. Some dont. And some dont high pass at 80 Hz.

Would help even more to know the amp model and speaker models so we can maybe design a passive/active system for you


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## analogrocker (Aug 1, 2009)

OldSchoolAudioandVideo said:


> So basically your passive 500hz highpass xovers that you got is useless.


Well according to the specs of the 2-way passive xover I plan on using, it says the following:



> Frequency ranges:
> 
> Midrange - 500Hz-3.5KHz
> *
> Tweeter - 4.5KHz-20KHz


If I am reading that correctly, it means that it high passes the midrange at 500 Hz and the tweeter at 4.5 kHz. If that's the case, then I should be able to do what I want. I just want to send a 1.5 kHz signal to the passive and let it handle the rest. As long as the midrange gets 1.5 kHz up to the tweeter cut-off, that's all I care about.

BTW, I am intentionally trying to have my midbasses play up high. I don't want to cross them low.


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## OldSchoolAudioandVideo (Nov 14, 2011)

Ok great. then that passive will do fine. Not many passives will do a bandpass.
So just connect it and go. No need to even use the amps xover on those 2 channels. the passive got that under control. Switch that xover on those 2 channnels OFF

As for the 8... you will just have an almost full range 8. If you cut it off at 80hz high pass from the amp then it will play EVERYTHING on up and that wont sound to good but it will work.


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## snyderd758 (Feb 21, 2011)

they are additive the hertz and the slopes.why are you using a passive with an active? Toss the passive and use the crossover in the amp you will have more tuning ability. You also lose power with the passive.


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## nick650 (Feb 7, 2011)

Here is what I do. My Zed has crossover and so does my MS-8.

When I want quality: I turn off my HPF on my Zed and run the normal 18dB slope of 72Hz.

When I want loudness: I turn on my HPF on my Zed at 55 Hz 24dB slope. This effectively is -18dB at 36 and 41.25 at -12dB. So you see my low end is GONE from my driver. If you add this up it would be roughly -26dB at around 38Hz.


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## OldSchoolAudioandVideo (Nov 14, 2011)

snyderd758 said:


> they are additive the hertz and the slopes.why are you using a passive with an active? Toss the passive and use the crossover in the amp you will have more tuning ability. You also lose power with the passive.


They are additive? WTH?


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## nick650 (Feb 7, 2011)

Slopes are not hertz buddy.


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## BuickGN (May 29, 2009)

Worst thread ever.


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## OldSchoolAudioandVideo (Nov 14, 2011)

BuickGN said:


> Worst thread ever.


yea its pretty bad..


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