The sonic benefits of an active crossover. A discussion.

[microstrip]

thought it might be good to hear from an actual speaker designer as well.

Roger Sanders, from Sanders Sound Systems is a person I deeply admire and whose opinion on ESL and audio topics in general I deeply respect.
In an interview, he clearly explains his position on active vs passive and some of the benefits of actives:

"Passive crossovers have dreadful performance. This is another extensive topic that I cannot address adequately in this interview. So just allow me to summarize by saying that passive crossovers have the well-known problems of phase shift, hysteresis losses, group delay, inadequately steep crossover slopes, and distortion. Less appreciated is the fact that they insert inductors, capacitors, and resistors between the amplifier and the speaker's drivers. This isolates the woofer from the amplifier and prevents the amplifier from having tight control of the driver. Or to put it another way, the damping factor of the amplifier is degraded by passive crossovers.

Since it is essential to use the amplifier to control the woofer, the amplifier must be connected directly to its driver without any intervening crossover components. Therefore electronic/active crossovers are essential to obtaining good integration. The amplifier must have a high damping factor. This excludes the use of tube amplifiers for driving woofers because their output impedance is too high. Powerful, well-designed solid state amplifiers have incredibly low output impedance (typically less than 0.1 Ohm), and massive current flow capacity, so they have the high damping factor and power needed to really control a woofer.

It is necessary to use electronic/active crossovers to achieve the best from any speaker system. I continue to be amazed by all the speakers on the market with passive crossovers that claim to be "reference" quality or SOTA systems. The truth is that electronic/active crossovers and multiamplifier systems are superior to any passive crossover system. All speakers will be improved with the proper use of electronic/active crossovers. So any speaker that uses passive crossovers simply cannot be considered the finest available. I am unwilling to compromise and so do not use passive crossovers in any of my current speakers.

There are many diverse types of electronic/active crossovers with many different features. Also, both analog and digital electronic crossovers now are available. I consider digital crossovers to be one of the greatest advances in modern audio. They offer features that I have wanted crossovers to have for years, but which were unavailable. "

From this article: http://www.dagogo.com/View-Article.asp?hArticle=991

Based on all my experience, Roger is 100% correct.

This passionate interview only addresses technical issues, as far as I know the thread topic is the sonic benefits of an active crossover. Unless these technical aspects are correlated with sound quality they are just technical opinions from a single speaker manufacturer.

The main technical argument is on the effect of the passive crossover in the damping factor. It is not proved that an infinite damping factor is needed to have good sound. Effectively, some speakers known to have exceptional bass performance have controls to adjust the low bass damping for proper optimization of sound quality in your room. Some speaker designers use the passive crossover to damp the resonances of the speaker.

This does not mean that a good damping factor is a nice thing for bass performance - surely an amplifier for subwoofer must have very low output resistance. But I am not prepared to sacrifice all the good things I listen to in excellent passive speakers coupled with excellent amplifiers just to have a little better low bass performance. For me music is much more than listening to a test recording of a drummer playing at high level in my room.

All IMHO. But I would love to know if all your experience. is just your own system.

 

[microstrip]

(...)

99% of the available product is in pro audio. See Adams, Events, JBLs, Genelecs, Dynaudio, Tannoy...the list is long. Anyone who is really interested has a journey ahead of them. And if you're not prepared to accept more for less -- substantially less -- if you're not prepared to believe that an active speaker system could replace not only your speakers, but your amps and preamp and cables, and sound better doing it, for a fraction of what audiophiles commonly pay for speakers alone, don't bother going out the door. You're also going to have to be prepared for a relatively transparent view into your recordings. You may not like it.
Tim

Tim,
You said it all in the last sentence. Why should some one listen in a way he does not like? Professionals do it to earn their lives, as these speakers are excellent tools. Some people also enjoy listening this way. But why should the majority of audiophiles think that listening to reproduced sound should be considered as a stay in Purgatory?

 

[microstrip]

To have the analogy hold up then there'd need to be some correspondence between a dirty pipe and the capacitors and inductors used in high quality speaker level crossovers. Is there?

Incidentally 'finest amplifiers' means the most transparent ones (for subjectivists), or the ones with lowest IMD with music signals (for objectivists).

No, IMHO there is not any correspondence. If you see it you have explain what it is. And not all subjectivists will define 'finest' amplifier as the 'most transparent one'. Personally I love the Nelson Pass definition you can find in the manuals of the XS series.

 

[DonH50]

I am not sure damping factor as the "main" advantage though it is one of them and probably most often cited. Other significant factors are the reduction in overlap of the drivers' frequency ranges since line-level crossovers typically offer much higher filter slopes than speaker-level crossover, reducing how hard each driver works and much much they interact sonically, and the ability to fine-tune the delay and phase response to each driver to optimize time- and frequency-domain response. Plus all the degradation passive components can have that Roger cited, especially for high-power components.

I seem to recall various articles stating a DF of 100 is essentially "ideal", improvements beyond that are unheard. Other articles (and no I do not recall which, would have to dig deep) claim as low as 10. Certainly how large a factor amplifier output impedance matters to the sound is highly dependent upon the speaker (i.e. the load it presents to the amplifier, among other things).

 

[opus111]

No, IMHO there is not any correspondence. If you see it you have explain what it is.

So what have you based your opinion that there's no correspondence on? Measurements of IMD with real music signals and listening tests?

And not all subjectivists will define 'finest' amplifier as the 'most transparent one'. Personally I love the Nelson Pass definition you can find in the manuals of the XS series.

What's that (too lazy to pull those up) ?

 

[microstrip]

So what have you based your opinion that there's no correspondence on? Measurements of IMD with real music signals and listening tests?
What's that (too lazy to pull those up) ?

Did you measure the IMD of dirty pipes? Congratulations! (It was the only correspondence you have asked our opinion about ...)

Nelson Pass addresses musical enjoyment ... You should read the section "Comments by Pass".

https://passlabs.com/images/uploads/manual/Xs_amp_om.pdf

Unless you prefer just reading "A few nominal specs: Xs 150"

 

[opus111]

Did you measure the IMD of dirty pipes? Congratulations! (It was the only correspondence you have asked our opinion about ...)

I only asked Tim for some basis for the dirty pipes he cited being analogous to crossover components. I can't understand the basis for your question.

I see on re-reading that you might have been responding to the earlier part of my post, which perhaps accounts for my confusion.

Nelson Pass addresses musical enjoyment ...

Thanks. Transparency correlates with musical enjoyment for me. Do you ever find yourself enjoying lower transparency more than increased?

 

[microstrip]

I am not sure damping factor as the "main" advantage though it is one of them and probably most often cited. Other significant factors are the reduction in overlap of the drivers' frequency ranges since line-level crossovers typically offer much higher filter slopes than speaker-level crossover, reducing how hard each driver works and much much they interact sonically, and the ability to fine-tune the delay and phase response to each driver to optimize time- and frequency-domain response. Plus all the degradation passive components can have that Roger cited, especially for high-power components.

I seem to recall various articles stating a DF of 100 is essentially "ideal", improvements beyond that are unheard. Other articles (and no I do not recall which, would have to dig deep) claim as low as 10. Certainly how large a factor amplifier output impedance matters to the sound is highly dependent upon the speaker (i.e. the load it presents to the amplifier, among other things).

Yes, I remember some arguments in this line about the damping factor. Just as an aside, non proved and very subjective comment, some of the best subjective bass I have listened was from the big 52 tube Atma-sphere MA2 OTLs, that have a damping of 10.

Most designers will refer that some controlled overlap is a good thing of their designs - I am not prepared to debate it. And they use the speakers units within their specified zones. If a driver is prepared to operate with quality up to 5 KHz, should we think that it sound better if it is operated only up to 2 kHz?

Considering the degradation, there is lot of ink on it, but is is a double sword argument. Almost all the time some one suggested that improving a component passive crossover component resulted in an sonic improvement, the objective crowd shouted and stoned him. Why should we believe them now? If they considered that a capacitor, a resistor and an inductor could not have a sound in the past, why are now they changing opinion?

 

[Phelonious Ponk]

Tim,
You said it all in the last sentence. Why should some one listen in a way he does not like? Professionals do it to earn their lives, as these speakers are excellent tools. Some people also enjoy listening this way. But why should the majority of audiophiles think that listening to reproduced sound should be considered as a stay in Purgatory?

That's why I ended with that sentence, micro. IMO, the most striking and consistent sonic signature of good active speakers is not bass control, but midrange transparency and precision of imaging. And not everyone will like it. Some consider a very high level of fidelity to the recording "a stay in purgatory." I wouldn't recommend active systems to them. I'll have trouble hiding my amusement, however, that the same people who insist they can hear an obvious difference between two simple pieces of wire will push their signal through this on its way to their speakers....



...and fail to see the problem.

Tim

 

[Kal Rubinson]

I don't know it - would be very interested if its not a whole lot of bother...

I have not yet been able to find it but it was "Passive Crossover Networks for Bi-Amplifier Systems" by B. B. Kuist, Audio, Nov. 1969, p52.

 

[microstrip]

That's why I ended with that sentence, micro. IMO, the most striking and consistent sonic signature of good active speakers is not bass control, but midrange transparency and precision of imaging. And not everyone will like it. Some consider a very high level of fidelity to the recording "a stay in purgatory." I wouldn't recommend active systems to them. I'll have trouble hiding my amusement, however, that the same people who insist they can hear an obvious difference between two simple pieces of wire will push their signal through this on its way to their speakers....

View attachment 8083

...and fail to see the problem.

Tim

Do not bother to have this trouble - the same people are not hiding their amusement with your choice of showing a Parasound - CX 1002 - 120Hz Passive Crossover for subwoofers filled with non polar electrolytics to be used with in wall speakers to document your point ...

 

[Phelonious Ponk]

Do not bother to have this trouble - the same people are not hiding their amusement with your choice of showing a Parasound - CX 1002 - 120Hz Passive Crossover for subwoofers filled with non polar electrolytics to be used with in wall speakers to document your point ...

I'm a visual guy. I like the hand and knew that there was no such thing as a crossover I could show that you wouldn't take exception to. Besides, a great wad of resistance is a great wad of resistance, micro. You can minimize it. You can't turn it into anything but a negative.

Tim

 

[microstrip]

I'm a visual guy. I like the hand and knew that there was no such thing as a crossover I could show that you wouldn't take exception to. Besides, a great wad of resistance is a great wad of resistance, micro. You can minimize it. You can't turn it into anything but a negative.

Tim

Although I can not understand you post, I can show you an appropriate high-end crossover.

 

[Robh3606]

Just for fun I am putting up 2 schematics. One for a simple 6.5" 2 way speaker with a passive crossover and the second an active crossover.

Take a look at the number of passive componenets that the signal has to go through in the active crossover compared to the simple passive crosover.

My question is this.

If passive parts are the evil of all evils that degrades performance how can you possibly see the active crossover as the better solution???

 

[Phelonious Ponk]

It's lovely. It's probably more wire, more resistance, more opportunity for noise, distortion and compromise than the sum of every interconnect in your system, and it is soldered directly in the path between your amplifiers and your speakers, but it's appropriate high-end.

Active crossovers have their issues too, but they work a lot better.

We are an odd lot: We praise the virtues of simplicity even as we complicate. But as long as the complications are a part of our conventional wisdom, they're "high end." I'll modify my original post to suit. Thanks for the research help.

Tim

 

[Phelonious Ponk]

Just for fun I am putting up 2 schematics. One for a simple 6.5" 2 way speaker with a passive crossover and the second an active crossover.

Take a look at the number of passive componenets that the signal has to go through in the active crossover compared to the simple passive crosover.

My question is this.

If passive parts are the evil of all evils that degrades performance how can you possibly see the active crossover as the better solution???

It's an excellent question. I don't really see it as the better solution. I hear it as such. And I'm nowhere close to alone on that. But maybe I'm dead wrong about the cause of the problems in passive systems; it wouldn't be the first time. Maybe it has nothing to do with the resistive components. Maybe it has everthing to do with the placement of those components in the signal chain.

Tim

 

[mojave]

Just for fun I am putting up 2 schematics. One for a simple 6.5" 2 way speaker with a passive crossover and the second an active crossover.

Take a look at the number of passive componenets that the signal has to go through in the active crossover compared to the simple passive crosover.

My question is this.

If passive parts are the evil of all evils that degrades performance how can you possibly see the active crossover as the better solution???

When an active crossover is part of your source, then there are no additional components. With an active crossover you can reduce the added components to almost zero.

I use an HTPC as my source and could easily implement active crossovers in my playback software. All that would be required would be to add two more channels of amplification (which I already have) and two binding posts per speaker. I've been thinking about going active, but have only had my speakers for about 5 months and am enjoying listening to them.

 

[microstrip]

It's lovely. It's probably more wire, more resistance, more opportunity for noise, distortion and compromise than the sum of every interconnect in your system, and it is soldered directly in the path between your amplifiers and your speakers, but it's appropriate high-end.

Active crossovers have their issues too, but they work a lot better.

We are an odd lot: We praise the virtues of simplicity even as we complicate. But as long as the complications are a part of our conventional wisdom, they're "high end." I'll modify my original post to suit. Thanks for the research help.

Tim

Tim,

We are an odd lot, but some find they need to be coherent and technically correct within their limited knowledge of audio design. Happily you do not have these concerns. You pick technical aspects randomly, exactly like if you were choosing good aspect nice color fruits for your salad fruit, your mix everything adding what you consider contradictory aspects of high-end, but are simply consequences of the variety of implementations and schools of thought of system design, and voila - no need to debate - final conclusion. Sorry to say this is not serious. Nice humor, but nothing else.

We have people who prefer simple passive crossovers - sometimes only a quality capacitor in series with the tweeter, or even full range crossoverless speakers. Others prefer complex crossovers. I have owned the SonusFaber Extrema that only had a high power resistor and an two inductors in the whole crossover and the circuit I have shown is just one of the five boards of my current speakers. I know which I prefer, but can not associate any of the perceived sound differences with crossover complexity. Can you?

 

[opus111]

It's an excellent question. I don't really see it as the better solution. I hear it as such.

Doesn't it just mean that active speakers are your preference then? Why all the technical stuff to support your preference?

 

[Phelonious Ponk]

Tim,

We are an odd lot, but some find they need to be coherent and technically correct within their limited knowledge of audio design. Happily you do not have these concerns. You pick technical aspects randomly, exactly like if you were choosing good aspect nice color fruits for your salad fruit, your mix everything adding what you consider contradictory aspects of high-end, but are simply consequences of the variety of implementations and schools of thought of system design, and voila - no need to debate - final conclusion. Sorry to say this is not serious. Nice humor, but nothing else.

We have people who prefer simple passive crossovers - sometimes only a quality capacitor in series with the tweeter, or even full range crossoverless speakers. Others prefer complex crossovers. I have owned the SonusFaber Extrema that only had a high power resistor and an two inductors in the whole crossover and the circuit I have shown is just one of the five boards of my current speakers. I know which I prefer, but can not associate any of the perceived sound differences with crossover complexity. Can you?

Can I associate sound with crossover complexity? I believe I hear a consistent character among good active speakers. I believe I could easily differentiate between the same speakers in active and passive implementations. But then again, we believe so many things like that which seem to vanish under the scrutiny if blind listening, so who knows? Perhaps you have an answer for Mojave? He seems to be more technical, and if he's right that an active crossover can reduce the added components to near zero, my little joke will have lost its humor.

Tim