Passive Crossover true or false

[naughtyca]

that got nothing to do with the thread, i think i need to look at my profile setting everytime somebody post on a thread i posted smd sends me a notification lol

[mrd6]

It can result in a 4ohm load but it is not defying physics or anything. It is because the other components used in the crossovers cause the unit as a whole (crossover, mid, and tweet) to present a nominal 4ohm load at the amp.

Also, it is not "our" theory it is one of the most basic laws of electricity

[Wicks]

This should get interesting......

Please read up on Ohms Law.

Two 4ohm loads connected together in any configuration CAN NOT equal 4ohms.

Also read Kirchoff Voltage and Current Laws.

Power is instantaneous, not averaged over frequency.

Amps don't "send out" a specific amount of power. Loads draw power from the amp.

Amps are capable of a certain amount of power across all frequencies (20-20khz) but speakers will actually have a varying impedance over frequency. Ex: a 4 ohm speaker is not always 4 ohms.

An amp that supplies 125W CAN NOT result in two speakers each getting 125W.

That would mean your speakers are together getting 250W with an amp supplying only 125W....not possible.

regarding your ohm law theory? components works differently, 4 ohm mid and 4 ohm tweets on a passive crossover will and can result to 4ohm load on the amp or is this also false?

There's a reason its called a LAW...and sorry but it applies to EVERYTHING.

This would be the only scenario where something like this could happen:

Some source content is input into the x-over.

The tweeter acts like an 8ohm load due to the frequency its given (speakers actually have varying loads depending on frequency).

The mid acts like an 8ohm load due to the frequency its given.

The combination at that instant would simulate a 4ohm load to the amp.

While this is possible, I'd think that most of the time the amp would see a <4ohm load.

[bcbrassard]

Lots of info going on here. thanks guys. Learning this kind of stuff is important. I am passive bi-amped right now on T265 comp crossovers being power by a T400-4. I plan to install a DEH-80PRS and go active soon. anything i need to watch out for in power output? espeical to the tweeters?

[mrd6]

Lots of info going on here. thanks guys. Learning this kind of stuff is important. I am passive bi-amped right now on T265 comp crossovers being power by a T400-4. I plan to install a DEH-80PRS and go active soon. anything i need to watch out for in power output? espeical to the tweeters?

Not sure what your equipment can do or handle power wise so i wont go into that but ill give you some general active advice. It makes sense to be concerned about your tweeters because its more difficult to know if they are being overdriven than a mid since you cant usually see this visually.

Here is how I would start:

First step, set up your 80prs crossovers just like the passives that came with the set. I.e. same crossover frequencies and slopes. This is obviously a safe starting point and should sound good because after all, RF designed the set to be ran this way.

Then, I would set your gains on the mids first. Set them to the level that you want (max gain before clipping/overpowering). I say do this first because in general mids are less efficient than tweets therefor the mid will be the limit to how loud your system gets. It is also easire to tell if you are overdriving the mid than the tweet. After setting the mids. Then start turning up the gain on the tweeters until the level is matched and has balanced output with your mids. This may mean that your tweeter gain appears to be turned up half as far as your mids and that is just fine. In this step, be sure not to turn the gain up any further than where that channel clips. If it seems like you need to max your gains out to get the tweeters to match the output of your mids, go back and start with the tweeter first, then match the mids to them.

Once this is done, you have the efficiencies matched and you can start experimenting by making small changes to the crossover settings in your deck. Depending on the changes you make, you might have to go back and fiddle with the gains a bit again. But stil make sure you do not push the amp into clipping.

This is generally the procedure I go about when running active and it has worked well for me so far.

Remember, a tweeter's power handling will drop drastically the lower you let it play as it is far easier to excede xmax (which on most tweeter is right around 1mm)

[CstrokerV]

This should get interesting......

Please read up on Ohms Law.

Two 4ohm loads connected together in any configuration CAN NOT equal 4ohms.

Also read Kirchoff Voltage and Current Laws.

Power is instantaneous, not averaged over frequency.

Amps don't "send out" a specific amount of power. Loads draw power from the amp.

Amps are capable of a certain amount of power across all frequencies (20-20khz) but speakers will actually have a varying impedance over frequency. Ex: a 4 ohm speaker is not always 4 ohms.

An amp that supplies 125W CAN NOT result in two speakers each getting 125W.

That would mean your speakers are together getting 250W with an amp supplying only 125W....not possible.

regarding your ohm law theory? components works differently, 4 ohm mid and 4 ohm tweets on a passive crossover will and can result to 4ohm load on the amp or is this also false?

There's a reason its called a LAW...and sorry but it applies to EVERYTHING.

This would be the only scenario where something like this could happen:

Some source content is input into the x-over.

The tweeter acts like an 8ohm load due to the frequency its given (speakers actually have varying loads depending on frequency).

The mid acts like an 8ohm load due to the frequency its given.

The combination at that instant would simulate a 4ohm load to the amp.

While this is possible, I'd think that most of the time the amp would see a <4ohm load.

what? if you take a tweeter thats 4 ohms and a mid thats 4ohms and hook it to a passive crossover without power running to them the load is 4 ohms... im confused what your trying to say

[naughtyca]

This should get interesting......

Please read up on Ohms Law.

Two 4ohm loads connected together in any configuration CAN NOT equal 4ohms.

Also read Kirchoff Voltage and Current Laws.

Power is instantaneous, not averaged over frequency.

Amps don't "send out" a specific amount of power. Loads draw power from the amp.

Amps are capable of a certain amount of power across all frequencies (20-20khz) but speakers will actually have a varying impedance over frequency. Ex: a 4 ohm speaker is not always 4 ohms.

An amp that supplies 125W CAN NOT result in two speakers each getting 125W.

That would mean your speakers are together getting 250W with an amp supplying only 125W....not possible.

regarding your ohm law theory? components works differently, 4 ohm mid and 4 ohm tweets on a passive crossover will and can result to 4ohm load on the amp or is this also false?

There's a reason its called a LAW...and sorry but it applies to EVERYTHING.

This would be the only scenario where something like this could happen:

Some source content is input into the x-over.

The tweeter acts like an 8ohm load due to the frequency its given (speakers actually have varying loads depending on frequency).

The mid acts like an 8ohm load due to the frequency its given.

The combination at that instant would simulate a 4ohm load to the amp.

While this is possible, I'd think that most of the time the amp would see a <4ohm load.

what? if you take a tweeter thats 4 ohms and a mid thats 4ohms and hook it to a passive crossover without power running to them the load is 4 ohms... im confused what your trying to say

yes

[CstrokerV]

yes i know it will.. but how you worded it in your answer confused me made it sound only if power is running to it maybe i miss read it im tired wanting to go to sleep but waiting on ups

[Wicks]

This should get interesting......

Please read up on Ohms Law.

Two 4ohm loads connected together in any configuration CAN NOT equal 4ohms.

Also read Kirchoff Voltage and Current Laws.

Power is instantaneous, not averaged over frequency.

Amps don't "send out" a specific amount of power. Loads draw power from the amp.

Amps are capable of a certain amount of power across all frequencies (20-20khz) but speakers will actually have a varying impedance over frequency. Ex: a 4 ohm speaker is not always 4 ohms.

An amp that supplies 125W CAN NOT result in two speakers each getting 125W.

That would mean your speakers are together getting 250W with an amp supplying only 125W....not possible.

regarding your ohm law theory? components works differently, 4 ohm mid and 4 ohm tweets on a passive crossover will and can result to 4ohm load on the amp or is this also false?

There's a reason its called a LAW...and sorry but it applies to EVERYTHING.

This would be the only scenario where something like this could happen:

Some source content is input into the x-over.

The tweeter acts like an 8ohm load due to the frequency its given (speakers actually have varying loads depending on frequency).

The mid acts like an 8ohm load due to the frequency its given.

The combination at that instant would simulate a 4ohm load to the amp.

While this is possible, I'd think that most of the time the amp would see a <4ohm load.

what? if you take a tweeter thats 4 ohms and a mid thats 4ohms and hook it to a passive crossover without power running to them the load is 4 ohms... im confused what your trying to say

You can't hook a DMM to the input of a crossover and measure the actual load the amp will see.

You guys are mixing DC and AC measurements.

Here is a basic 24dB/octave x-over:

If the image is hard to see, click on the pic and/or save it to your computer and look at it with a white background.

It's the quickest I could find online.

If anything, search "Linkwitz-Riley 24dB/octave crossover".

See those capacitors inline with the tweeter?

At DC (DMM-ohmmeter) those are opens and won't put the tweeter in the measurement.

So you'd only be measuring the mid speaker by itself (inductors are close to shorts at DC).

That's why you're always seeing 4ohms........

[White Lightning]

WOW ... Way too much sugar for a dime in this thread.

Too much complication for such a simple application ...

Its very simple ... That's giving that the amplifier can ACTUALLY produce its rated power on "all" frequiencies ... And I know of only a select few that can do this ...

The passive crossovers are designed to give the drivers what they need and restrict them from what they don't need ... And nothing more ... Crossovers are designed to make the components work together, not against each other and rob power from one another ... To make a component set work correctly, one can not work without another ...

Components can normally handle more power than rated, but you have to understand that they need headroom and dynamics (driver control) verses raw power just to make them play louder ... They will sound just like you are throwing distortion to them ... Which is what I normally see in most cases ...