A good summary, but I'm not sure I agree with the main benefit to active. Getting around the speakers internal crossovers and, therefore, having the amps directly in control of the drivers is pretty critical, IMO.
I agree with that so should have been more clear. I was thinking in the context of what the OP wanted to do, and the initial benefit assuming no change to the internal crossovers (already in the speakers). I do not know for sure, but suspect a lot of people start by actively bi-amping their speakers using the hi/lo terminals on the back without replacing the internal crossovers.
There are several aspects to consider. Just look at the schematic of the crossover of the Dynaudio Ayres, a simple 2 way speaker. Do you think that you can easily emulate the transfer function of the treble section?
Or if you still do not believe look for the techniques developed by Harman to interactively design the crossovers of their speakers - do you believe that if all it was needed were just some ideal Linkwitz-Riley, Bessel or Butterworth filters they would spend so many resources optimizing its design? Also you have to consider that the speakers themselves have an impedance that is not purely resistive - this means that you have also to consider its variation versus frequency and use a complex model of the speaker impedance. One last aspect that I am thinking about is the variation of the phase of the crossover with frequency - you can not be sure that you respecting it with an active crossover.
I can easily accept that you can built fantastic active speakers, I am not so sure about fiddling with an existing optimized passive design.
This does not prevent a few people from getting excellent results with this technique - but these are particular cases of dedicated people with a lot of expertise.
Even I'm not so sure about this. It sounds dubious. But I would like to understand, specifically, what goes into good passive crossover designs that can't be emulated with digital active crossovers.
I believe one person besides Gary Protein, here Keith W (?) has done exactly that. he emulated the crossover in his speakers with a DEQX and built an active filter or had it built, based on the results from the DEQX whose sonics he din't quite like. He can always chime in ...
Yup that's me. I've already chimed in earlier in the thread. I too, would like to know what a passive crossover in the speaker can do that a digital XO can not.
Well, apart from the obvious degradation of the signal by redigitizing the signal and outputting the signal via cheap DAC's anyway - which is the problem which seems to plague most digital crossovers. That's why my digital crossover controls my sub. Sounds like overkill, but I couldn't offload the damn thing even though I offered it for sale at less than 50% the purchase price with outstanding warranty left.
In theory it's not at all the difficult to do. All you need to do is load the crossover schematic into a program such as LEAP and get the voltage drives. You can do it into a standard load or use the actual measured impedance curves of the drivers mounted in the cabinets. You then take the curves and use them as the Target curves in the Active crossover portion of the program. You will end up with schematics for the active portion. If you have card based analog crossover like the JBL DX-1 you can just build the cards from the schematics. I have done this a couple of times and it works very well indeed.
It can get complicated depending on what type of speakers you are doing the active biamp on. For a horn hybrid with a dynamic woofer and a HF horn and compression driver you have the compensation for the horn to contend with. Many biamped horn set-ups usings analog crossovers have the horn compensation done with passive components.
There are several aspects to consider. Just look at the schematic of the crossover of the Dynaudio Ayres, a simple 2 way speaker. Do you think that you can easily emulate the transfer function of the treble section?
Or if you still do not believe look for the techniques developed by Harman to interactively design the crossovers of their speakers - do you believe that if all it was needed were just some ideal Linkwitz-Riley, Bessel or Butterworth filters they would spend so many resources optimizing its design? Also you have to consider that the speakers themselves have an impedance that is not purely resistive - this means that you have also to consider its variation versus frequency and use a complex model of the speaker impedance. One last aspect that I am thinking about is the variation of the phase of the crossover with frequency - you can not be sure that you respecting it with an active crossover.
I can easily accept that you can built fantastic active speakers, I am not so sure about fiddling with an existing optimized passive design.
This does not prevent a few people from getting excellent results with this technique - but these are particular cases of dedicated people with a lot of expertise.
Why could it not be replicated with an active approach? I am not sure I get your point.. If the filter exist and accomplish .... well .. filtering some phase correction and in some case EQ it can be accomplished in active or in passive. As for the varying impedance of the driver with respect to frequency, and an active solution can be even better and of course can be accomplished by more sophisticated methods, namely digital ... Passive filters in many instances waste a good amount of the amplifier energy in the form of heat (seems to be the case in your example) .. With active this is not the case .. Furthermore Digital filters allows certain things that are not easy or impossible in analog.. Do you know of a filter that can not be replicated by digital means? Now if we are talking about what you believe ..
There are things audiophiles are no comfortable with. Active speakers, active crossovers are among these. Manufacturers are after all business people .. They have to go with what their (very limited) market wants and so far we audiophiles prefer our multiple boxes and the wires we can change and our passive crossovers, the more complex looking and preferably in its own box, the better ...
That's the issue. Do you want to use DSP in the speakers or active crossover??? Do you want to stay all analog?? Analog has limitations an example being the horn compensation. It's sometimes easier to use a combination of active analog and passive components than go all active.
Unhappily some people are entering the debate without reading all the previous posts. The equipment that was being addressed is the DCX2496 or the Marchand crossover, not DSP or custom analog active crossovers that have much higher capability and can not be used or built by the usual audiophile. It was clear that my posts only addressed these units.
Now consider for example that a designer implements a classical Bessel second order filter with inductors and capacitors. This could be easily implemented with a DCX2496. Then, by listening he modifies it adding a few components to implement a notch filter and and an increased slope at another cutoff frequency. When he adds this components, the original curves of the simple circuit will be strongly affected by the interaction of these new components, and the effect of these added components will not be easy to predict also. The DCX only allows you to implement simple transfer functions and add or invert them. Even implementing a lot of them and summing them it can not emulate a response as the one resulting from the Dynaudio crossover depicted in the figure of post #20.
We have to consider that the sections of the DCX are buffered and in a strictly passive filter there is no "buffering" - it is why passive design crossover is a specialist affair.
FIY, I own a DCX2496 and I have used it with the excellent software that allows you to view the response of the filters/equalizers that we can implement with it.
Most speakers have complex crossovers and their transfer functions can not be emulated using the typical active crossovers, such as the Berhinger DCX2496 or Marchand's, that only allows the selection of a few basic filter shapes, slopes and phases. Should we expect that an approximate transfer function is better than the original, carefully studied and optimized by the designer?
If you are screaming at me I missed the post. As far as determining the suitability of a either of those crossovers you would need to look at the Voltage Drives of the passive crossover in LEAP or another suitable program. Passives can be very hard to copy which is why you have too understand exactly what the passive crossover is doing. Analog crossovers are more limited than DSP based such as the DCX2496.
How did you determine what the Voltage Drive is in the posted schematic??
If you are screaming at me I missed the post. As far as determining the suitability of a either of those crossovers you would need to look at the Voltage Drives of the passive crossover in LEAP or another suitable program. Passives can be very hard to copy which is why you have too understand exactly what the passive crossover is doing. Analog crossovers are more limited than DSP based such as the DCX2496.
How did you determine what the Voltage Drive is in the posted schematic??
I only used the crossover schematic as as example of of crossover that can not be emulated with a DCX2496. Nothing else.
I have nothing against active speakers, just do not think that taking an existing passive design and replacing the existing crossover with a low price user configurable active crossover, even if it is of good quality, will forcefully result in a much better sounding loudspeaker.
Some people seem to think that digital is almost miraculous and passive analog crossovers are an evil, or the reverse. I know about excellent examples of both - one of the best existing Hi-End speakers in the world (the Cabasse La Sphere, now in version 2) is an active speaker using a DSP crossover and Class D amplifiers. IMHO, what separates such products from the inferior products is not being active or passive but the talent and expertise of the designers and manufacturers. And most times talent needs money to show.
I only used the crossover schematic as as example of of crossover that can not be emulated with a DCX2496. Nothing else.
I have nothing against active speakers, just do not think that taking an existing passive design and replacing the existing crossover with a low price user configurable active crossover, even if it is of good quality, will forcefully result in a much better sounding loudspeaker.
Some people seem to think that digital is almost miraculous and passive analog crossovers are an evil, or the reverse. I know about excellent examples of both - one of the best existing Hi-End speakers in the world (the Cabasse La Sphere, now in version 2) is an active speaker using a DSP crossover and Class D amplifiers. IMHO, what separates such products from the inferior products is not being active or passive but the talent and expertise of the designers and manufacturers. And most times talent needs money to show.
There are better solutions than others. Active crossovers are a better solution than passives. They have their caveats, they are not for every one and they make systems more complicated and even more costly.. Certain of the function performed in a passive crossover may not need to be emulated in an active... One of them in particular: matching driver output doesn't have to be accomplished with dumping power to a resistive network ( I know I am repeating myself) as it is done in passive crossovers sometimes at great loss upward of 90% of an amp power. IOW this is not a simple tweak.
Trying to improve on a design is nothing new however for audiophiles, we constantly fiddle with things in our system to make the gear better .. Things the "the talent and expertise of the designers and manufacturers" to paraphrase you din't put in the (often expensive) products to start with .. So we use new feet, new power cords, other speaker cables than the one the manufacturers uses or recommend ... We go to great length to use different tubes than those the manufacturer with all his or her wisdom and knowledge use in their designs.. We even change tube types in their gear ... And claim superior results .. We modify their (our?) gears regularly , we call that "tweaks" .. Thus I am asking if one knows how why can't they do the same with speakers?
. . . .I have nothing against active speakers, just do not think that taking an existing passive design and replacing the existing crossover with a low price user configurable active crossover, even if it is of good quality, will forcefully result in a much better sounding loudspeaker. . . .
First, active crossovers are not necessarily inexpensive. True, they are not in the cost range of large full range floor standing speakers, but $3500-8000 MSRP, sometimes more, isn't exactly peanuts-not to me anyway. I have to work for a living. By comparison, the passive crossover in speakers is usually inexpensive. But the important thing is this: being user configurable is an asset. Being able to select slopes, shelving, crossover frequencies, and volume/gain adjustments for each frequency range is what makes them so valuable, add to that the fact that you have allowed the amplifier to directly control the speakers drivers is what is so beneficial. I'm NOT saying you can take an active crossover out of the box and set it up as fast as you connect a headphone to an iPOD, but the time you spend in tweaking it will significantly reward you in the end.
There are better solutions than others. Active crossovers are a better solution than passives. They have their caveats, they are not for every one and they make systems more complicated and even more costly.. Certain of the function performed in a passive crossover may not need to be emulated in an active... One of them in particular: matching driver output doesn't have to be accomplished with dumping power to a resistive network ( I know I am repeating myself) as it is done in passive crossovers sometimes at great loss upward of 90% of an amp power. IOW this is not a simple tweak.
Trying to improve on a design is nothing new however for audiophiles, we constantly fiddle with things in our system to make the gear better .. Things the "the talent and expertise of the designers and manufacturers" to paraphrase you din't put in the (often expensive) products to start with .. So we use new feet, new power cords, other speaker cables than the one the manufacturers uses or recommend ... We go to great length to use different tubes than those the manufacturer with all his or her wisdom and knowledge use in their designs.. We even change tube types in their gear ... And claim superior results .. We modify their (our?) gears regularly , we call that "tweaks" .. Thus I am asking if one knows how why can't they do the same with speakers?
Frantz,
You are slowly moving the subject of the debate. My main point was the one you addressed in your fist sentence.
Considering the tweak, IMHO tweaks are small changes - carrying a modification that changes the FR does not look like a tweak for me ... And yes, you are right, although many tweaks do not detract from the original performance I have seen many systems completely ruined by improper tweaks.
When addressing changing passive for active crossovers we are clearly in field of large DIY modifications, the zone where bias expectation and preference dangerously mix.
For reference from a quick look and foggy memory, crossover prices:
miniDSP (digital) is about $100 - $200 USD
Cheap passive (analog) inline crossovers, $20 - $50 each
Behringer DSP units ~$300
dbx, Rane active analog crossovers ~$300 - $600
Marchand passives, maybe $200 - $500, active analog up to ~$1k
Bryston active analog about $3500, probably about the top of the consumer active analog crossovers
DEQx and similar high-end DSP units range from ~$5k to $10k and up
Active = opamp or other amplifier, passive = RLC network (no gain or buffer). I am sure there are others but this is the range I saw when looking for a crossover last year.
(...) First, active crossovers are not necessarily inexpensive. True, they are not in the cost range of large full range floor standing speakers, but $3500-8000 MSRP, sometimes more, isn't exactly peanuts-not to me anyway. I have to work for a living. By comparison, the passive crossover in speakers is usually inexpensive. But the important thing is this: being user configurable is an asset. Being able to select slopes, shelving, crossover frequencies, and volume/gain adjustments for each frequency range is what makes them so valuable, add to that the fact that you have allowed the amplifier to directly control the speakers drivers is what is so beneficial. I'm NOT saying you can take an active crossover out of the box and set it up as fast as you connect a headphone to an iPOD, but the time you spend in tweaking it will significantly reward you in the end.
Gary, you are an honorable exception in this game. You are an experienced audiophile and have an expertise that few of us can dream about. IMHO, for you being user configurable is an asset, for the great majority of people it will be an entry into Dante' Inferno.
I will use this answer to remember that direct driving a tweeter with a normal solid state amplifier is a dangerous game. The transients created by power on/off sequences of most of them are not of concern to woofers or other units in series with the capacitors of a passive crossover, but can easily destroy a tweeter or some medium speakers. Remember that a new coil/diaphragm assembly for a professional tweeter is usually reasonably priced, but your precious hi-end tweeters can easily cost over usd 500.00. An active system must have some protection and a well thought power up/down sequence.
The transients created by power on/off sequences of most of them are not of concern to woofers or other units in series with the capacitors of a passive crossover, but can easily destroy a tweeter or some medium speakers.
All you need to do is put a protection capacitor in series. It's a common practice in the SR field. Compression driver diaphrams are not inexpensive either. The Be's can run up to $900 a pop.
. . . .I have nothing against active speakers, just do not think that taking an existing passive design and replacing the existing crossover with a low price user configurable active crossover, even if it is of good quality, will forcefully result in a much better sounding loudspeaker. . . .
Have you ever tried biamping?? There are systems that are user configurable to go from fully Passive to Biamped. That's about the easiest way to compare the difference between passive and active.
Frantz,
You are slowly moving the subject of the debate. My main point was the one you addressed in your fist sentence.
Considering the tweak, IMHO tweaks are small changes - carrying a modification that changes the FR does not look like a tweak for me ... And yes, you are right, although many tweaks do not detract from the original performance I have seen many systems completely ruined by improper tweaks.
When addressing changing passive for active crossovers we are clearly in field of large DIY modifications, the zone where bias expectation and preference dangerously mix.
Not really the point remains that one can get better objective results with such modifications. Tweaks such as fuses directions, cable elevators, fuses with directionality , cryogenic treatment and the likes are where to paraphrase you expectation bias and preferences dangerously mix .. but I am sure you got my points .. And I did agree with you that such modifications require knowledge and are not plug and play ...
Confusion arises when people talk about an "active system" or "going active."
To clarify a few definitions:
Active speaker--one that has its own built in amplifier(s) Passive speaker--one that you connect to a power amplifier-a typical speaker that most of us use
Passive crossover-a crossover network after the power amplifier that divides the frequencies to be sent to the drivers. Active crossover-a crossover after the preamplifier that divides the frequencies to be sent to the power amplifier.
An active speaker (one with a built in amplifier) does not necessarily have an active crossover. It can have a single amplifier and a passive crossover after the amp and before the drivers. An active speaker may have an active crossover inside and two or more channels of amplification, one channel for each type of driver, e.g, woofers, midranges and tweeters.
A passive speaker (one without a built in amplifier) does not necessarily have a passive crossover. A passive speaker does not have it's own built in amplifiers, but it may have an active crossover in the signal path after the preamp to divide the spectrum into specific frequency ranges to be sent to separate power amplifiers that will drive the woofers, midranges and tweeters. The amplifiers here are just not inside the speaker cabinets. (This is what I have in my system--passive speakers with active crossovers.)
Most of us use passive speakers that have passive crossovers.
Keith, Barry, Don and I use passive speakers employing active crossovers after the preamp and separate amplifiers for woofers, midranges and tweeters.
Some may use the new active speakers like the new TADs or Brystons that have built in active crossovers and discrete amplifiers for woofers, midranges and tweeters.
I am not aware of audiophile quality active speakers that have passive crossovers and one channel of power amp for the entire speaker, but it is common among amplifiers used in PA systems and guitar amplifiers.
Sorry Gary, I prefer using these terms because they cause less confusion
Low Level Crossover (LLXO) - a crossover that deals with low level (preamp level) signals. These need to be inserted between the preamp and power amps. There are two types - an active (ALLXO) means that it is powered. A passive (PLLXO) means that it is unpowered. All DSP based crossovers, my Marchand, your Pass XVR-1, the Bryston, etc. are active. I would need to check, but I believe the crossover in the B&W Nautilus "Snail" is a PLLXO, and you can buy PLLXO's from Marchand.
High Level Crossover (HLXO) - a crossover that deals with high level (amplified) signals. These are always passive and are inserted between the power amp and the speakers. By far the majority of speakers on the market have a HLXO.
Active Speaker - any speaker which is powered from mains. If a power cord runs to your speaker, it is active. This is irrespective of whether the speaker has a LLXO or HLXO. The tweeter on my Acapella is active. Speakers made by Adam are active. The bass section on Avantgarde Uno's and Duo's are active. The Quad ESL is active. Many people use the term "active speaker" to mean that the amplifier is connected directly to the driver (implying the presence of a LLXO), but I believe that it is more precise to simply specify the type of crossover present because that by itself implies that the amp is directly connected to the driver.
Passive Speaker - any speaker which is powered by a power amp. By far the majority have a HLXO, but some are crossoverless, e.g. so-called "full range" speakers.
We all have different definitions for what we're talking about!
At least we agree on active and passive speakers definitions. I also agree that the Pass, Marchand and Bryston crossovers are powered because you do plug them into the wall.
Uh-hum, I do like my definitions better!!!!!!!!!!!!
When I say "full range speaker," I mean at least 20-20kHz, not one driver that does everything, vs a speaker that lacks a full bottom end which would be "restricted full range" as Stereophile defines it.
Active speakers -- speakers with separate amps for each driver, and crossovers before amplification, built in.
Powered speakers -- passive speakers with built in amps.
The distinction is not small, though audiophiles often are confused, referring to small active monitors as "computer speakers." They are forgiven their ignorance, as their ears have likely been blunted by the distortions of passive speakers.
