This active crossover will be good for my speakers?

[Juhazi]

No, not correct if I understood what you wrote. You just dont get it.
Ask your friends and workmates, if someone knows someone who can help you. Otherwise you might destroy your precious Fostexes.

 

[CosmicJazz]

Thanks for try, appreciate if the other fellows that contributed to this thread, can read my interpretation of the crossover, and explain me why is wrong.

Best regards to all.

 

[gene_stl]

You do NOT wire together the woofer tweeter and midrange. If you did how would the music be separated into highs midranges and lows?

Think of the crossover as a black box. It has one pair of inputs labeled + and - which refer to the drivers going in and out (phase) it is important to observe those polarities so that at the crossover frequencies where two drivers are both "speaking" they add or subtract constructively rather than destructively which can happen if phase is incorrect. It has three pairs of outputs each with a plus and minus according to the diagram. These lead to the respective speakers. Additionally the attenuators go between the mid range and the tweeter, after the crossover. This is because if you did not have the attenuators the speakers would sound bright and harsh and not have a desireable frequency response because typically midranges and tweeters are more efficient than wooofers and need to be shelved down.

Juhazi mentions earth and ground. This is not correct. Speaker minus connections should not be considered earth and ground. The minus black connector on many amp outputs is grounded but this is not necessarily the case and on many amps connecting the black to ground will at the very least blow a fuse. Especially on single supply amps such as bridged class D amps.

It would be more economical and easier to biamp or triamp but you would have to solve the crossover question. You seem to not want to go digital.
Building a high level passive crossover requires expensive components such as your beautiful Fostex attenuators which I wonder how much those cost. But they reduce the damping factor by putting (complex) impedance between the crossover and the driver. But you do have to have level controls. In a triamp you just adjust the channels gain rather than amplifying the signal and then throwing the power away in an attenuator. With powerful amps available for practically free nowadays this is not that big a deal but if you are using a tube amp or a class A amp you may not have the power to spare. Additionally separate from the attenuator, crossover networks throw away a tremendous amount of the amplifier's power. The three way more than two way and four way more than three way. Such crossovers with lots of "ways" and steep slopes can easily eat two thirds of the amplifier power.

The Black wooden box you posted above is a very nice job of an external high level passive crossover. Yours should looks something like that.

If you want I could take a look at what you are doing on What'sApp or FB Messenger. (I don't do skype anymore because they keep demanding to know my birthday.)

I commend you on trying to bite off a little more than you can chew. This is how you learn. But the observation above that you need to learn to read a circuit diagram is correct. I can only imagine what those Fostexes cost and you DON'T want to blow them up. There are many tutorials on both schematic diagram reading and crossover network design. Both the crossover schematics you posted are standard looking designs and a crossover is not a moon shot (in spite of what some would like you to think). But implementing it well with high quality components will cost as much as triamping. Nonetheless if you insist on doing it that way, you need to make sure you get it right. Tri amping would actually be considerably easier.

 

[LTig]

Hello, thanks for the feedbacks guys, really appreciate.

Interesting... I must say that sometimes I think it's too much go through the active crossover route on just my first project hehehe...

The other path that I consider, is multi-amplify, but with passive crossover, will put the passive crossover plan here, appreciate if you guys can take a look, and solve a doubt that I have about it.

View attachment 32616

As you can see, the woofer on the crossover plan is a different model to the one that I will purchase, I'm trying to figure out, if the crossover scheme of components will change, or will remains the same.

I will use:
http://www.loudspeakerdatabase.com/Fostex/FW305

Displayed on crossover scheme:
https://www.fostexinternational.com/docs/speaker_components/pdf/w300a2.pdf

Please, let me know, anything must be changed on the crossover scheme using the FW305 instead of the W300A?

Many thanks guys!

Don't go passive, go active, and preferably digital. Why:

• You need no passive crossover with all its limitations, like caps with high tolerances, or attenuators for level matching. Why creating lots of power and then burn it in resistors to heat?
• You can mix drivers of different sensitivity and match levels in the active crossover or at the input of the power amps
• you need power amps with less power (and still be able to reach higher SPL than with a passive speaker):
  • a cheap beefy class D power amp for the bass
  • 2 small power amps for mid and high (low power because the horns are more sensitive then the bass driver)
• You can time align all drivers.
• You can use the EQ in the crossover to get a flat on axis response.
• You can use the EQ in the crossover to fix the room modes below 300 Hz.

 

[CosmicJazz]

You do NOT wire together the woofer tweeter and midrange. If you did how would the music be separated into highs midranges and lows?

Think of the crossover as a black box. It has one pair of inputs labeled + and - which refer to the drivers going in and out (phase) it is important to observe those polarities so that at the crossover frequencies where two drivers are both "speaking" they add or subtract constructively rather than destructively which can happen if phase is incorrect. It has three pairs of outputs each with a plus and minus according to the diagram. These lead to the respective speakers. Additionally the attenuators go between the mid range and the tweeter, after the crossover. This is because if you did not have the attenuators the speakers would sound bright and harsh and not have a desireable frequency response because typically midranges and tweeters are more efficient than wooofers and need to be shelved down.

Juhazi mentions earth and ground. This is not correct. Speaker minus connections should not be considered earth and ground. The minus black connector on many amp outputs is grounded but this is not necessarily the case and on many amps connecting the black to ground will at the very least blow a fuse. Especially on single supply amps such as bridged class D amps.

It would be more economical and easier to biamp or triamp but you would have to solve the crossover question. You seem to not want to go digital.
Building a high level passive crossover requires expensive components such as your beautiful Fostex attenuators which I wonder how much those cost. But they reduce the damping factor by putting (complex) impedance between the crossover and the driver. But you do have to have level controls. In a triamp you just adjust the channels gain rather than amplifying the signal and then throwing the power away in an attenuator. With powerful amps available for practically free nowadays this is not that big a deal but if you are using a tube amp or a class A amp you may not have the power to spare. Additionally separate from the attenuator, crossover networks throw away a tremendous amount of the amplifier's power. The three way more than two way and four way more than three way. Such crossovers with lots of "ways" and steep slopes can easily eat two thirds of the amplifier power.

The Black wooden box you posted above is a very nice job of an external high level passive crossover. Yours should looks something like that.

If you want I could take a look at what you are doing on What'sApp or FB Messenger. (I don't do skype anymore because they keep demanding to know my birthday.)

I commend you on trying to bite off a little more than you can chew. This is how you learn. But the observation above that you need to learn to read a circuit diagram is correct. I can only imagine what those Fostexes cost and you DON'T want to blow them up. There are many tutorials on both schematic diagram reading and crossover network design. Both the crossover schematics you posted are standard looking designs and a crossover is not a moon shot (in spite of what some would like you to think). But implementing it well with high quality components will cost as much as triamping. Nonetheless if you insist on doing it that way, you need to make sure you get it right. Tri amping would actually be considerably easier.

Hello Gene, I understood know, what made me think that the wires from horn and tweeter would be unified, was because the other + / - connectors do no appear on the crossover diagram, wondering why there's just + / - symbols behind the woofer at the end of the wires....

I would like to clarify that's not me who will build the crossover, if I choose the passive way, I more or less already know some people that can do it for me where I live, but as I said, I just like to at least understand the basic principles and etc... Yes, the attenuators are expensive, this makes me think that maybe the active way can be considered instead, I more or less done some price calculations, maybe a friend of mine from Japan, can get a good 3 way active crossover for me, half of the price of the 4 attenuators.

But let me not consider the prices for a moment, I would like to propose a hypothetical solution about the active way, maybe I can learn more about the technical side.

Power Amps:
Two 3 channel amps https://www.hifiengine.com/manual_library/denon/poa-t3.shtml

Active crossover:
Analog 3 way: https://audio-heritage.jp/FOSTEX/etc/en3000.html
better pics here: https://www.hifido.co.jp/sold/17-11127-51780-00.html?LNG=E

Let me see if I understood how to set the frequencies division properly according to my drivers.

Low / Mid: My woofer can play till 3.5khz, and the horn starts to play at 800hz, so I can set at low/mid at 800hz or 1.2khz.

Mid / High: My Horn plays till 20khz, and the tweeter from 5khz till 40khz, so I can set the mid/high as 5khz or 8khz.

This thinking of the configurations options are correct? Please let me know your thoughts, I think I can learn more with this hypothetical solution.

Many thanks!!!!

 

[gene_stl]

Yes 800 and 5K would be good.
The Fostex crossover looks very nice if you can find one and its newer than the Sony or Pioneer.
Unless you already have a source for the Denon 3 channel amps I would look at three amps that are better matched to each driver. They don't need to be the same and it is likely better that they aren't. No tweeter can absorb 120 watts except a big PA monster. Not that you would set the volume that high. The Fostex propaganda refers to 120 60 and 50 Watt music power so the RMS continuous handling is probably half that. The music power ratings would be reasonable powers for the amps. The three channels would be convenient from a chassis point of view which would give you two rather than three chasis sitting around. I like more not less chasis

 

[LTig]

[..] I would like to propose a hypothetical solution about the active way, maybe I can learn more about the technical side.

Power Amps:
Two 3 channel amps https://www.hifiengine.com/manual_library/denon/poa-t3.shtml

Active crossover:
Analog 3 way: https://audio-heritage.jp/FOSTEX/etc/en3000.html
better pics here: https://www.hifido.co.jp/sold/17-11127-51780-00.html?LNG=E



Let me see if I understood how to set the frequencies division properly according to my drivers.

Low / Mid: My woofer can play till 3.5khz, and the horn starts to play at 800hz, so I can set at low/mid at 800hz or 1.2khz.

Mid / High: My Horn plays till 20khz, and the tweeter from 5khz till 40khz, so I can set the mid/high as 5khz or 8khz.

This thinking of the configurations options are correct? Please let me know your thoughts, I think I can learn more with this hypothetical solution.

Many thanks!!!!

Yep, your thinking is correct. But let me suggest a better solution (as I think):

• get a Behringer DCX2496 Ultradrive Pro as crossover. It is much more flexible than the Fostex XO and can do all things I wrote about in posting #24:
  • Use a sharp crossover (48 dB/Oct) for bass/mid so you can go as low as possible (800 Hz) with the mid horn. A 12" woofer is not very good at higher frequencies. My 3 way studio monitor has an 8" woofer and the crossover is at 650 Hz! You cannot do this with the Fostex.
  • Use a time delay for woofer and tweeter to align with the mid horn. You cannot do this with the Fostex.
  • Use the volume setting per channel to level match tweeter and mid with the woofer. This you can do with the Fostex as well.
  • Use the channel EQ to fix the on axis frequency response. You cannot do this with the Fostex.
  • Use the input EQ for room correction. You cannot do this with the Fostex.
• get a cheap beefy class D poweramp for the woofers, like the Behringer A500 or the Crown XLS 1502. The higher THD would not matter much because the ear is not so sensitive at low frequencies. On the other hand the woofer must play until 800 Hz ...
• get better poweramps with low power for mid and highs (40-50W could be more than sufficient, important is low noise due to high sensitivity of the horns). Sorry no recommendation here.

 

[gene_stl]

I was not going to harp on that because the CosmicJazz seems to want to have an analog crossover. But I would agree with everything above.
The Crown amp mentioned has a DSP built in that can do most of the tricks that the Behringer can do.
I have seen reliability complaints about Behringer amps bu none about their crossover. Crown amps are great. They did have a period where some Taiwanese capacitors were splurping on some power amps. They weren't the only ones. But there are a very very large quantity of used power amps on the market right now. You can get screaming bargains with only a little effort. (I have friends here in St. Louis that have tons of them. Two guys just got nine Brystons EACH from the st. louis science center IMAX theater. I have so many power amps I haven't even tried to buy any of those.)

I nice big 300 watt per channel woofer amp. Then maybe a couple of Yamaha Mosfet PA power amps for the top two channels. You could use a tube amp on the tweeter channel. The output transformer would render coupling caps unecessary and the extra harmonic distortion that tubes add would be in the inaudible ultrasonic range. Finding a balanced input tube amp might be more challenging.

Your woofer cannot "play until 3.5K". Even if you cross it over at 1.2k it will start "beaming" which is undesireable. You have to consider the wavelength of the sound each driver is trying to produce. This is why tweeters are smaller than wooofers and why violins are smaller than violas cellos basses and double basses.

 

[CosmicJazz]

Yes 800 and 5K would be good.
The Fostex crossover looks very nice if you can find one and its newer than the Sony or Pioneer.
Unless you already have a source for the Denon 3 channel amps I would look at three amps that are better matched to each driver. They don't need to be the same and it is likely better that they aren't. No tweeter can absorb 120 watts except a big PA monster. Not that you would set the volume that high. The Fostex propaganda refers to 120 60 and 50 Watt music power so the RMS continuous handling is probably half that. The music power ratings would be reasonable powers for the amps. The three channels would be convenient from a chassis point of view which would give you two rather than three chasis sitting around. I like more not less chasis

Hello Gene,

Thanks for this enlightening info, let me ask you some question about amp choices, and another thing about the crossover functionality.

Corssover: What is the 12 or 18db/octave function? I notice this on a lot of crossovers, what's the point of this function and how affects the sound? Also would like to understand more the 0 or 180 phase function, for what I understood about this, when taking a look at the top of the line active crossover that Fostex made, the EN3020, manual is available here: https://www.fostexinternational.com/docs/tech_support/manuals.shtml I think this one do not appears to sell very often like the EN3000 in Japan, and probably much more expensive, anyway, I noticed on the manual, that you can adjust the phase selecting between 0 or 180, and moving manually all the drivers in a way that their "motors" become aligned which other, which is what I can do with my speakers, see picture:

Amps: Would like to understand more about amp choices for each driver, and the power relation that you mentioned, I always thought that power is never too much, much more power available than the drivers will ever need, makes the amp work easy, and with more quality (big headroom of power available), but appears this is a misconception? But I also understand that one of the advantages of multi amp, is the option to choose amps that will combine their sound signature with the drivers characteristics, for example, low power Class A for the high sensitivity horn and tweeters, or tubes and etc....

Yep, your thinking is correct. But let me suggest a better solution (as I think):

• get a Behringer DCX2496 Ultradrive Pro as crossover. It is much more flexible than the Fostex XO and can do all things I wrote about in posting #24:
  • Use a sharp crossover (48 dB/Oct) for bass/mid so you can go as low as possible (800 Hz) with the mid horn. A 12" woofer is not very good at higher frequencies. My 3 way studio monitor has an 8" woofer and the crossover is at 650 Hz! You cannot do this with the Fostex.
  • Use a time delay for woofer and tweeter to align with the mid horn. You cannot do this with the Fostex.
  • Use the volume setting per channel to level match tweeter and mid with the woofer. This you can do with the Fostex as well.
  • Use the channel EQ to fix the on axis frequency response. You cannot do this with the Fostex.
  • Use the input EQ for room correction. You cannot do this with the Fostex.
• get a cheap beefy class D poweramp for the woofers, like the Behringer A500 or the Crown XLS 1502. The higher THD would not matter much because the ear is not so sensitive at low frequencies. On the other hand the woofer must play until 800 Hz ...
• get better poweramps with low power for mid and highs (40-50W could be more than sufficient, important is low noise due to high sensitivity of the horns). Sorry no recommendation here.

Hello LTig,

Thanks for the Behringer suggestion, my concern with digital crossover, is that my main source is vinyl, don't want the phono signal be converted to digital and back to analog again, and I really liked the easy to use approach on the Fostex EN3000, veery straight forward, but we can talk about this subject later, otherwise my mind will be saturated with too much variables to start to learn at same time, and I will get lost again hehhehe.

Thanks guys, very grateful for your teachings.

 

[Krunok]

my concern with digital crossover, is that my main source is vinyl, don't want the phono signal be converted to digital and back to analog again

You shouldn't worry about that. Search the forum, this has been tested by @Blumlein 88 and even after 8 conversions back and forth there was no audible difference.

 

[sergeauckland]

Hello Gene,

Thanks for this enlightening info, let me ask you some question about amp choices, and another thing about the crossover functionality.

Corssover: What is the 12 or 18db/octave function? I notice this on a lot of crossovers, what's the point of this function and how affects the sound? Also would like to understand more the 0 or 180 phase function, for what I understood about this, when taking a look at the top of the line active crossover that Fostex made, the EN3020, manual is available here: https://www.fostexinternational.com/docs/tech_support/manuals.shtml I think this one do not appears to sell very often like the EN3000 in Japan, and probably much more expensive, anyway, I noticed on the manual, that you can adjust the phase selecting between 0 or 180, and moving manually all the drivers in a way that their "motors" become aligned which other, which is what I can do with my speakers, see picture:

Amps: Would like to understand more about amp choices for each driver, and the power relation that you mentioned, I always thought that power is never too much, much more power available than the drivers will ever need, makes the amp work easy, and with more quality (big headroom of power available), but appears this is a misconception? But I also understand that one of the advantages of multi amp, is the option to choose amps that will combine their sound signature with the drivers characteristics, for example, low power Class A for the high sensitivity horn and tweeters, or tubes and etc....







Hello LTig,

Thanks for the Behringer suggestion, my concern with digital crossover, is that my main source is vinyl, don't want the phono signal be converted to digital and back to analog again, and I really liked the easy to use approach on the Fostex EN3000, veery straight forward, but we can talk about this subject later, otherwise my mind will be saturated with too much variables to start to learn at same time, and I will get lost again hehhehe.

Thanks guys, very grateful for your teachings.

In answer to your questions:-

12 or 18dB/octave indicates how rapidly the crossover attenuates outside the operating band. In general terms, the faster the better, as this reduces the amount of energy each driver gets outside its operating band, thus reducing distortions of all sorts. I use 48dB/octave which my DCX2496 provides. I don't see any benefit from using a lower rate when a higher rate is available.

As for choice of amps, unless you're into the whole 'audiophile' sound-signature thing, all amps should be completely transparent, so the only choice is the amount of power needed. In general terms, and this depends very much on he relative sensitivity of the drivers, you need around half the power in the mid that you use for the bass, and probably half again for the treble. I don't see any problem with using more power, I myself use three identical 120 watt amps, but if you're using excessively powerful amps, you may get noise problems, as the signal to noise ratio of an amplifier is relative to full power, so, for example, a 100dB S/N 100 watt amp will generate more noise than a 100dB S/N 10 watt amplifier.

Finally, I don't worry about analogue to digital to analogue conversions. I use the analogue outputs of my turntables, CD player and Squeezebox, through a conventional analogue pre-amp, then into the Behringer crossover which converts to digital, then and out again analogue for the power amps. It's still measures transparent end to end.

S.

 

[CosmicJazz]

Thanks...

Hey, still about the active crossover situation: there's any specs related to the crossover, that I must pay attention, related to the output voltage and input sensitivity? just like when you are choosing a preamp to match a power amp you know? Where you must have to check if the preamp offers enough output voltage in order to be able to drive a particular power amp..

For example, for what I remember, in order to know if a preamp will drive a power amp properly, with considerable headroom, you need to know the preamp gain, and convert the gain measurement (dB), to voltage measurement (Volts), also must have to know the output voltage of your source, (phono stage or CD player for example) and add to the preamp gain, so you check what's the power amp input sensitivity, and you know if your preamp will driver the power amp properly.... important do know this when choosing a preamp and power amp from different manufacturers, or preamp and power amp that was not designed for each other....

Anyway...

This also applies to the active crossovers? They affect the relation of output voltage / input sensitivity in any way?

Many thanks.

 

[Julf]

Hey, still about the active crossover situation: there's any specs related to the crossover, that I must pay attention, related to the output voltage and input sensitivity?

Apart from crossover frequencies and the steepness of the slope (6, 12, 18 etc dB/oct), passive crossovers are designed for a specific driver impedance behavior, and have a limited power capacity.

This also applies to the active crossovers? They affect the relation of output voltage / input sensitivity in any way?

Real, active crossovers are a very different animal, as they work at line-level voltages and impedances. They are pretty much like preamps in that regard.

 

[sergeauckland]

Active crossovers are nominally unity gain devices, insofar as the output voltage is the same as the input voltage, with +- gain adjustment around that, to take account of differing driver sensitivities and amplifier gains.

What you need to check is that the maximum voltage the crossover provides before clipping is sufficient to load the power amp fully. I would be very surprised is that wasn't the case. Crossovers typically can provide anything up to 7 volts output, whilst most power amps don't need more than 2 volts. What I've done in my system is to put an attenuator on the crossover outputs to reduce the maximum voltage to match more or less the amplifier's sensitivity thus having to drive the crossover harder and thus reduce noise. There's more than enough gain elsewhere in the system to ensure that I get sufficient volume without clipping anything.

S.

 

[CosmicJazz]

Not understood yet...

Real active crossovers? for example this one:

https://audio-heritage.jp/FOSTEX/etc/en3000.html
https://www.hifido.co.jp/sold/17-11127-51780-00.html?LNG=E

It's a "real active crossover"? that works as a line additional preamp or not?

Here are the specs:

Model Channel divider
Specifications 2-3way electronic dividing network
Bandpass characteristic 18dB / oct
Input impedance 47kΩ
Input sensitivity 0.5V (rated output)
Rated output 1V (Low: 100Hz, Mid: 1kHz, High: 10kHz)
Maximum output 8V (+ 18dB / dBV, distortion 0.05% or less)
Output impedance 470Ω
Total harmonic distortion 0.005% or less (rated output)
Crossover frequency 2way-1: 500, 650, 800, 1.2kHz
2way-2: 2k, 3k, 5k, 8kHz
3way: 500, 650, 800, 1.2kHz (Low / Mid)
2k, 3k, 5k, 8kHz (Mid / High)
Output phase switching 0 °, 180 ° (Low, Mid, High)
S / N 100dB or more (IHF-A)
Input / output terminal RCA pin terminal (pure gold plating)
Power supply AC100V
Power consumption 4.3W
Dimensions Width 482x Height 44x Depth 235mm (19 "/ 1U Standard Rack Mount Size)
Weight 3.5kg

For what I understood, taking this crossover by example, is that: will not occur changes on preamp output voltage with the crossover between the preamp and power amps, but I not understood how a preamp can have such a high output voltage to drive 6 power amps for example, I was thinking that the active crossover would increase the output voltage in order to drive multiple power amps...

Little lost here...

 

[Julf]

Not understood yet...

Real active crossovers? for example this one:

https://audio-heritage.jp/FOSTEX/etc/en3000.html
https://www.hifido.co.jp/sold/17-11127-51780-00.html?LNG=E

It's a "real active crossover"? that works as a line additional preamp or not?

Yes. They are real active crossovers, working at line level (so like preamps).

For what I understood, taking this crossover by example, is that: will not occur changes on preamp output voltage with the crossover between the preamp and power amps

It might or it might not, depending on the gain and level settings of the crossover.

but I not understood how a preamp can have such a high output voltage to drive 6 power amps for example, I was thinking that the active crossover would increase the output voltage in order to drive multiple power amps...

A preamp or crossover has a low output impedance, so loading it with the high input impedance of (one or 6) power amps doesn't cause the voltage to drop. In any case, you wouldn't need more voltage, you would need more current, but in this case it isn't an issue.

 

[CosmicJazz]

I'm beginning to understand, so the active crossover act like an additional line level preamp, in fact, each channel is a line level preamp, that's why is possible to drive 3 separated power amps, that's makes sense?

 

[Julf]

I'm beginning to understand, so the active crossover act like an additional line level preamp, in fact, each channel is a line level preamp, that's why is possible to drive 3 separated power amps, that's makes sense?

Yes, and no.

Yes, the active crossover act like an additional line level preamp. Yes, each channel is a line level preamp. But... any individual channel could easily drive 10 power amps.

 

[CosmicJazz]

Hmm.. so in resume, in order to know if a given active crossover will provide synergy with determined power amps, the specs verification is just like what you do when you consider a preamp + power amp combo

That is:

Verify what would be the output voltage (considering the source on the calculation), must be two times greater than power amp input sensitivity, impedance must be at least 10 times lower than the power amps.

That's correct?

Thanks!

 

[Julf]

Hmm.. so in resume, in order to know if a given active crossover will provide synergy with determined power amps, the specs verification is just like what you do when you consider a preamp + power amp combo

I would not use the word "synergy", but rather talk about compatibility.

Verify what would be the output voltage (considering the source on the calculation), must be two times greater than power amp input sensitivity, impedance must be at least 10 times lower than the power amps.

Why two times greater? You don't want/need to exceed the input sensitivity. In this case not an issue, as the crossovers have adjustable levels.