The sonic benefits of an active crossover. A discussion.

[Phelonious Ponk]

Tim,

1) I fail to understand what you learn from comparing "active and passive crossovers with the same speaker design". Such thinks are very different in response, safe for a few designs that have very simple passive crossovers and can not be considered representative of high-end loudspeakers. And sometimes the enhancement in clarity and transient response is carried at the expense of other aspects of the speaker sound quality.

I firmly believe that good designers can idesign great active speakers f they are allocated resources and time - I have listened to examples of them, such as the original B&W Nautilus four way snails twenty years ago. But it needs great expertise. 2) It is not just an affair of picking some amplifiers and tweaking a digital crossover during the weekend.

My reserves come from the hype of the active sector - 3) I own and have played in the past with a Behringer DCX 2496, that most active speaker proponents consider a great crossover. IMHO when it is used as a high pass crossover it sounds poor and clearly compromises my system. My experience was carried with SoundLab A1PXs, bypassing the existing passive crossover (6dB low pass, 12 dB high pass). YMMV, as you often say.

1) Would it make more sense to you to compare active and passive speakers of very different design?

2) I don't think anyone has implied that it is.

3) If ever there was a company that fit the description "Good for the money," it is Berhinger. But they make some of the least expensive pro gear on the market and are still trying to crawl out from under a reputation for poor reliability. Not a good example. In my view, any hobbyist playing with active crossovers and bi-passing passive crossovers in an existing passive system is a very bad example from the start, doomed to deliver bad results. The best active systems I've heard were engineered from the ground up to be active, and fully integrated by professionals, not patched together in someone's living room with cheap pro crossover. Search for synergy that way if you must. I'll seek professional design and execution.

Tim

 

[Robh3606]

But it needs great expertise. It is not just an affair of picking some amplifiers and tweaking a digital crossover during the weekend.

Hello Micro

Well actually it is. You can make it as difficult as you want but the bottom line is if you can match the voltage drives of the passive system you can make any system an active with a good modern digital speaker management system and a couple of pair of amps.

There certainly is a learning curve but you would be surprised what you can accomplish in just a few hours with the right information.

Sorry but you seem to like to make things much harder than they actually are. You should just remember the NIKE slogan

Just Do It

I have converted systems to biamp and while it is not for the faint hearted it is definitely something that can be done. Just takes work.

I fail to understand what you learn from comparing "active and passive crossovers with the same speaker design".

The purpose is so blatantly obvious. Compare them side by side to see what the actual audible differences are. Plain and simple. Geedes has done this with his speakers. His conclusion was the difference in sound quality between the active and passive versions wasn't worth the added cost of an active version.


Rob

 

[microstrip]

1) Would it make more sense to you to compare active and passive speakers of very different design?

Just because one think does not make sense does not imply that the alternative makes sense. I prefer to read about your opinion and experience of many designs, than on dubious tests.

2) I don't think anyone has implied that it is.
3) If ever there was a company that fit the description "Good for the money," it is Berhinger. But they make some of the least expensive pro gear on the market and are still trying to crawl out from under a reputation for poor reliability. Not a good example. In my view, any hobbyist playing with active crossovers and bi-passing passive crossovers in an existing passive system is a very bad example from the start, doomed to deliver bad results. The best active systems I've heard were engineered from the ground up to be active, and fully integrated by professionals, not patched together in someone's living room with cheap pro crossover. Search for synergy that way if you must. I'll seek professional design and execution.

Tim

You are correct - it was not you, but some active proponents imply it and advise inexperienced consumers to bypass their crossovers and replace them with customizable off the shelve crossovers. Happy we agree on the need of experts and original intentions - it is why I think the experiment you have referred was not significant. We only diverge that I think that there is nothing intrinsic with active or passive designs - the difference is in the particular implementation. And perhaps in my feeling that the existing actives are not the proper way of supplying the needs of most audiophiles, specially me!

 

[microstrip]

Hello Micro

Well actually it is. You can make it as difficult as you want but the bottom line is if you can match the voltage drives of the passive system you can make any system an active with a good modern digital speaker management system and a couple of pair of amps.

There certainly is a learning curve but you would be surprised what you can accomplish in just a few hours with the right information.

Sorry but you seem to like to make things much harder than they actually are. You should just remember the NIKE slogan

Just Do It

I have converted systems to biamp and while it is not for the faint hearted it is definitely something that can be done. Just takes work.

The purpose is so blatantly obvious. Compare them side by side to see what the actual audible differences are. Plain and simple. Geedes has done this with his speakers. His conclusion was the difference in sound quality between the active and passive versions wasn't worth the added cost of an active version.

Rob

Rob,

Each of us has his and experiences. How accurately do you match phases and amplitudes in the units? What crossover are you using?

 

[Robh3606]

Each of us has his and experiences. How accurately do you match phases and amplitudes in the units? What crossover are you using?

As long as the voltage drives are identical the rest will fall into place. The important phase information between the drivers is locked into the slopes of the curves. The amplitude may need some adjustment but it's all possible and amplitude is a very easy adjustment. In the system I did I used a JBL DX-1. It's a rare cardbased analog crossover. In a digital crossover it would be much easier, no custum cards to build and you could also adjust for the physical driver offsets to improve the impulse response over the passive original.

Rob

 

[microstrip]

As long as the voltage drives are identical the rest will fall into place. The important phase information between the drivers is locked into the slopes of the curves. The amplitude may need some adjustment but it's all possible and amplitude is a very easy adjustment. In the system I did I used a JBL DX-1. It's a rare cardbased analog crossover. In a digital crossover it would be much easier, no custum cards to build and you could also adjust for the physical driver offsets to improve the impulse response over the passive original.

Rob

Rob,

If people accept your sentences I quoted in bold, it is easier. I am not prepared to accept it. Let us hear from the experts.

 

[opus111]

Yes, my perception tells me that when you refer to "signal quality in a cable" ignoring the whole context you are oversimplifying and the conclusion will not be correct.

Ah then your perception is indeed distorting as I surmised. I am not 'ignoring the whole context' rather looking at the cable's function and exploring it within the whole context of a complete system. Do please explain what I'm leaving out though, I'm eager to learn.

No. The originating signal is affected by the cable and the charge.

The originating signal is still the originating signal at the origin. What is 'the charge' - the price paid for the cable? If so then that indeed is a system aspect, and nothing to do with the signal.

I hope you are not referring to the famous null test next.

I am not, not that I know what it is. It might help discussion if you just stuck to the words you see from me without inferring that I'm throwing in allusions.

Dangerous because it suggests the old wire with gain methods and analogies. Take it as an humorous statement.

I am not familiar with those, so then you're adding in things I'm not actually saying. Perception again.

BTW, my opinion is that none of the typical and widely accepted known electrical measurement will correlate with the cable sound.

I concur with your opinion - you'll see wherever cables get mentioned on WBF and I contribute, I'll talk about common-mode noise typically. There's no currently accepted measurement for that.

So we must currently debate cable sound using listening tests, not measurements.

Yes I agree there too. You'll note I wasn't debating cable sound.

 

[opus111]

My reserves come from the hype of the active sector - I own and have played in the past with a Behringer DCX 2496, that most active speaker proponents consider a great crossover. IMHO when it is used as a high pass crossover it sounds poor and clearly compromises my system.

A colleague brought one to me for me to have a poke around inside a couple of years back. A disaster in engineering terms for SQ because no attention had been paid to noise control. A DSP system is an electrically very noisy item (not quite as noisy as a PC though, the clock rates are considerably lower) and I think they were powering it from a SMPSU. But then such boxes sell on specs and price, not SQ so its a great product in its niche. The niche not being high-end.

 

[opus111]

The purpose is so blatantly obvious. Compare them side by side to see what the actual audible differences are. Plain and simple. Geedes has done this with his speakers. His conclusion was the difference in sound quality between the active and passive versions wasn't worth the added cost of an active version.

I've had some private correspondence with Earl Geddes. I don't find his approach at all consistent. He decries listening and claims that designing an audio system is all about pure objective engineering. But then he claims that actives don't sound better - when all along to him ears are the least reliable test. Something doesn't stack up for me there. I suspect its more that passive suits his particular skill set and particular market. Also he does make claims for 'proprietary crossover design' which presumably won't be able to be used as a marketing slogan if he were to go active.

 

[Phelonious Ponk]

Just because one think does not make sense does not imply that the alternative makes sense. I prefer to read about your opinion and experience of many designs, than on dubious tests.



You are correct - it was not you, but some active proponents imply it and advise inexperienced consumers to bypass their crossovers and replace them with customizable off the shelve crossovers. Happy we agree on the need of experts and original intentions - it is why I think the experiment you have referred was not significant. We only diverge that I think that there is nothing intrinsic with active or passive designs - the difference is in the particular implementation. And perhaps in my feeling that the existing actives are not the proper way of supplying the needs of most audiophiles, specially me!

I think it is about implementation as well. And I believe that both approaches can yield excellent results. But I also believe that there are intrinsic advantages in integrated well-designed active systems that allow them to much more efficiently achieve excellence.

Tim

 

[KlausR.]

Back to sonic benefits of active crossovers.

When I was shopping for loudspeakers in 2001, it was an old article in Audio Magazine written by Bob Stuart (Meridian) that convinced me of the inherent technical superiority of the active approach: “The case for active speaker systems”, Audio September 1987, p.64-70.

In this article Stuart says that active speakers “can perform substantially better in the areas of resolution, detail, dynamics, efficiency”.

Further, “An active loudspeaker can give a much cleaner, more detailed and defined sound, and unlike most passive designs, this sound is consistent at different levels. In fact, although active speakers are more efficient and capable of producing very clear, loud sounds, a good active system will surprise equally by its capacity to produce exquisitely clear sounds at low levels”.

When I had my current speakers new, a guy came to listen who had a system with Magnepans and Audio Research components. He brought some of his favorite music and to his surprise discovered that on one of the tracks the bass guitar was actually playing distinct notes, not the muddy noise he was hearing on his own system.

In the past Klein+Hummel manufactured a passive and an active version of the same monitor, the active had more bass (-3dB point at 56 vs 72 Hz), and played louder (111.5 vs 107.7 dB SPL). The frequency response of the active was somewhat flatter.

Passive


Active


I actually never bothered investigating passive speakers in more detail back in 2001, so I don’t have any listening experience worth mentioning. The speakers I had before my current ones were a no-name and two DIY designs.

Klaus

 

[Groucho]

When we talk about comparing passive to active, or converting passive designs into active, are we assuming that there will be an element of measurement and driver correction? Once DSP is brought in, it seems to me that implementing an active version of any speaker becomes a 'no brainer'. Not only have you got the benefits of direct coupling of amp to driver, less work for the amp to do and so on, but you are able to perfectly match the phases of the drivers and attain time alignment between them. Is there anything not to like?

Converting an existing passive design to active is an interesting experiment, but it may not be a sensible starting point for a real product: passive designs are exercises in compromise, with attention being paid to efficiency and matching of sensitivity and other factors between drivers. The chances of pulling off a successful three way design are far lower than those of a passable but inherently limited two way, for example. The active designer doesn't have to worry about such trivialities and has access to a far wider range of configurations, drivers and permutations thereof.

 

[Phelonious Ponk]

When we talk about comparing passive to active, or converting passive designs into active, are we assuming that there will be an element of measurement and driver correction? Once DSP is brought in, it seems to me that implementing an active version of any speaker becomes a 'no brainer'. Not only have you got the benefits of direct coupling of amp to driver, less work for the amp to do and so on, but you are able to perfectly match the phases of the drivers and attain time alignment between them. Is there anything not to like?

Converting an existing passive design to active is an interesting experiment, but it may not be a sensible starting point for a real product: passive designs are exercises in compromise, with attention being paid to efficiency and matching of sensitivity and other factors between drivers. The chances of pulling off a successful three way design are far lower than those of a passable but inherently limited two way, for example. The active designer doesn't have to worry about such trivialities and has access to a far wider range of configurations, drivers and permutations thereof.

What he said. And the answer to the question above is no, unless it is poorly done. Micro's right about implementation. I'm right about the inherent advantages. Blow the implementation and you'll blow the advantage. Duh.

Tim

 

[JonFo]

When we talk about comparing passive to active, or converting passive designs into active, are we assuming that there will be an element of measurement and driver correction?

In a conversion scenario, measurements are an absolute must. An appropriate measurement rig, knowledge on how to interpret the results and knowledge on how to define the DSP settings are all required.
With those, one can indeed correct on a per driver basis, but more importantly, one can optimize for total system performance in-room. That last part is a huge win IMHO, as that's what matters when considering the 'sonic benefits'.

 

[LL21]

What he said. And the answer to the question above is no, unless it is poorly done. Micro's right about implementation. I'm right about the inherent advantages. Blow the implementation and you'll blow the advantage. Duh.

Tim

Thanks, Tim. Just so i am clear, are the inherent benefits (in sound terms) that i get a more linear sound? Coherence? Transparency? I am tempted to try using the Wilson Active Crossover, get the crossover specs on my X1s and then bypass the bass passive crossover network and drive the bass directly from an old Gryphon amp. My Wilson dealer has agreed to help me do this. What should i expect to hear? Thanks!

 

[microstrip]

I am tempted to try using the Wilson Active Crossover, get the crossover specs on my X1s and then bypass the bass passive crossover network and drive the bass directly from an old Gryphon amp. My Wilson dealer has agreed to help me do this. What should i expect to hear? Thanks!

The proper way of emulating the response would be taking the woofer out of the speaker, attaching a signal probe (nice name for just two wires) and measuring the transfer function of the crossover. As you have two speakers, you can always keep one unmodified during the development phase and tune the active crossover driving both with the same signal and differentially comparing them - a nice use in this case for a null test.

As your main amplifier is high quality and high power, and the speaker is very efficient asking for little current, the main difference will be due to the change in damping of the subwoofers due to the suppression of the resistance of the series bass inductor. Most probably this inductor is a high quality low resistance one and the difference will not be large. You have to try to know what will be the change.

IMHO asking for what will be the difference to people who have never listened to your system and your room is just a nice way of creating bias expectation! If your Wilson dealer has experience doing this modification, trust him. Ask him if he wants to use the active crossover to modify the response of the speakers or to emulate the response of the passive. It is an important question.

 

[LL21]

As your main amplifier is high quality and high power, and the speaker is very efficient asking for little current, the main difference will be due to the change in damping of the subwoofers due to the suppression of the resistance of the series bass inductor. Most probably this inductor is a high quality low resistance one and the difference will not be large. You have to try to know what will be the change. .

Thanks.

IMHO asking for what will be the difference to people who have never listened to your system and your room is just a nice way of creating bias expectation! If your Wilson dealer has experience doing this modification, trust him. Ask him if he wants to use the active crossover to modify the response of the speakers or to emulate the response of the passive. It is an important question.

Spoke with Wilson dealer who said in his opinion the greatest improvement is control, linearity, transparency.

 

[Phelonious Ponk]

Thanks, Tim. Just so i am clear, are the inherent benefits (in sound terms) that i get a more linear sound? Coherence? Transparency? I am tempted to try using the Wilson Active Crossover, get the crossover specs on my X1s and then bypass the bass passive crossover network and drive the bass directly from an old Gryphon amp. My Wilson dealer has agreed to help me do this. What should i expect to hear? Thanks!

I can't help but think that you'd be better off, and get a much better test not knowing what to expect, , but what I hear as characteristic in most active speaker systems is clarity, manifested most noticeably in great definition of note-leading transients that makes the mids and highs feel very dynamic, in clear definition space between instruments and voices, in precise, almost hyper-real imaging. But I suspect the imaging would blend some in a larger room at a greater distance from the speakers. And most of these are characteristics in the midrange and treble, If you're just going to make the bass active, and you have enough amplification do drive your speakers without any strain now, I'm not sure I'd expect much. Active sub woofers, as I'm sure you know, can take a lot of strain of of amps that need the relief and can deliver cleaner, better defined bass with an absence of "boom." But if you're unable to place the bass drivers separately, you'll lose a good bit of the advantage. I've not heard all that many floor-standing speaker systems with built-in subs - half a dozen maybe - but I've felt that better results were achieved when the subs are moveable.

Tim

 

[LL21]

I can't help but think that you'd be better off, and get a much better test not knowing what to expect, , but what I hear as characteristic in most active speaker systems is clarity, manifested most noticeably in great definition of note-leading transients that makes the mids and highs feel very dynamic, in clear definition space between instruments and voices, in precise, almost hyper-real imaging. But I suspect the imaging would blend some in a larger room at a greater distance from the speakers. And most of these are characteristics in the midrange and treble, If you're just going to make the bass active, and you have enough amplification do drive your speakers without any strain now, I'm not sure I'd expect much. Active sub woofers, as I'm sure you know, can take a lot of strain of of amps that need the relief and can deliver cleaner, better defined bass with an absence of "boom." But if you're unable to place the bass drivers separately, you'll lose a good bit of the advantage. I've not heard all that many floor-standing speaker systems with built-in subs - half a dozen maybe - but I've felt that better results were achieved when the subs are moveable.

Tim

Thanks, Tim. Micro felt the same way...a nice incremental change perhaps but not earth shattering. The Wilson X1s are known to be efficient and not a particularly difficult load and the Gryphons will take an enormous amount of punishment and be fine, so perhaps not an effort worth pursuing. As for active moveable bass, i run a big Velodyne (in parallel) that i cut off around 40hz or so which i would not live without. Period. Changes everything for the better when set up well.

 

[microstrip]

Lloyd,

Andy Payor says lots of nice thinks about actives in the interview referred above, but he also is very clear:

" I make it a point to affirm that the active Arrakis has no “subwoofer” section, but that the extremely light, very compliant, low-distortion twin 15” woofers, each with approximately four cubic feet of volume, should be viewed as the foundation of the system, not merely an adjunct to extend bass. Because we are not attempting a lawless coercion of nature to extend the bass response, the integration is exceptional."

This is what you must look for in your system. A system and room with exceptional integration of bass, more than quantity and ultra-flat response. Just MHO.