[Roger A. Modjeski]

I have been invited by TurboFC3S to discuss this topic in the lab rather than my Music Reference circle. 

Below is the posting which prompted his invitation.

--------------------------------------------------------------------------------
First: The problem and the bad news

Below is a picture of a crossover that the maker is obviously proud of. I must admit it is impressive and congratulate them on a beautiful execution of a bad idea. What is the bad idea? Speaker level crossovers are the weakest link in the high-end audio system. Wouldn't the money spent to make such an expensive crossover be better spent on a second amplifier and electronic or passive line level crossover??? These are the questions so few audiophiles are willing to ask.

http://live.audiogon.com/i/mn2005/h/1113690388.jpg

Here is the insurmountable problem. At the speaker level all the components of the crossover have to pass amperes of current. At 100 watts a 4 ohm speaker and it's crossover experience peak currents of 10 amperes or more if the impedance is lower at that frequency. No matter how good the capacitors are, they have to handle these currents and let me assure you they don't like it a bit. Capacitors store charge, they are not designed to pass current, it isn't in their nature.

The inductors add hundreds of feet of 16, 18 or 20 gauge magnet wire. Look at how many are in the picture below. Seems odd to ignore this common, inexpensive wire, but it's inside where it is not seen. Given the aesthetic attention given to speaker cables it becomes obvious that most audiophiles are only concerned with they can see.

Lets not forget the resistors that are there to convert audio signals into heat. Besides that, 5-100 watt power resistors generally have internal brass wire crimps to connect the nasty resistor wire, which is a poor conductor by definition, to the nasty leads. These crimps can oxidize over time making matters worse.

It is my opinion that any speaker maker who is offering a high end speaker offer it without a crossover at a discount that you can apply toward another amplifier to do it right. When hi-fi started, speakers were cheap in comparison to amplifiers. Now it's the other way around. There are many systems with inexpensive amplifiers that are a fraction of the cost of the speakers they drive. In some systems the cables coming in and out of the power amp cost more than the amp itself. This makes no sense at all. 

From their appearance alone I can see that the components and construction costs of these speaker level crossovers is indeed more than a second quality amplifier.

Now the good news

The simple alternative is both inexpensive and elegant: Crossovers are just filters with slopes of 6, 12, or 18 dB per octave. They are implemented electronically with passive components alone or combined with tubes, transistors or ICs. I have been making 6dB/octave crossovers for knowledgeable listeners who have already caught on to the improvements and flexibility they provide. A two way unit should have a level control to turn down the more sensitive amplifier. A three way would have 2 level controls. They can also be made with one level control for each amplifier for total flexibility. One can easily find the setting that gives the mix of bass, treble and midrange (in a 3 way system) that the speaker manufacturer intended. In addition, the listener can adjust that blend to his liking. A little more bass, a little more treble at the turn of a knob.

Here are the technical advantages:

1. The audio currents in line level crossovers are in micro amperes, one million times smaller than the currents in a speaker level crossover.

2. There are no inductors. No matter how large the wire used to wind them, they add resistance right where you don't want it, in series with the woofer. There goes your damping (woofer control).

3. 1% sub-watt resistors are made with metal films that are much better than resistance wire.

4. Capacitors are of small values in the area of .01 microfarads v.s. microfarads to 100s of microfarads in speakers. The QUAD ESL has a 200 microfarad electrolytic cap that all the audio has to pass through along with series power resistors, ceramic capacitors and miles of wire in the chokes that drive the concentric rings. None of the mods available address the circuits that drive the rings as they operate at 6,000 volts. 

5. It is easy to move the crossover point around and control the output levels so that any speaker and amplifier can be used.

6. No power is wasted and amplifiers can be of smaller size which generally sound better. While the woofer might require 100 watts from a solid state amp with high damping, the tweeter can be driven by a little 5 watt single ended tube amp.

7. Most speaker crossovers have over a dozen components (count them in the picture). A 6dB/octave 2 way crossover requires one capacitor and one inductor. For 3 way add one more inductor and one more capacitor. For 12 db slope add one more component per driver. For 18 dB add one more. Given that relationship, infinite slope would require an infinitie number of components.  The center crossover in the picture above has 15 components that I can see. There are 4 big inductors whose wire, unwound, would allow you play your speakers a few houses down the block while connected to your amplifier back at your house.

Before you plunk down the money on your next speaker purchase ask the maker if he would be willing to build the speaker without the crossover and give you an appropriate discount. By the amount of that discount you will quickly know how he values his crossover.

I recently fell in love with the little FE 103 speaker that we now offer. I didn't expect it to sound so good. It's just a simple single driver in a box. I have to attribute the detail and coherency I hear to the quality of the Fostex driver and the absence of a crossover. Obviously this little speaker is not going to play high levels or deep bass but with it's passive line level EQ (again something often done inside the speaker and hidden in the complex crossover)
 
 

[NewBuyer]

The only passive speakers that consistently sound better to my ears than the best active speakers I've ever heard to date, are the Joseph Audio lineup. These use their patented "Infinite Slope" technology, which results in a 240db/octave transition (120db/octave in their latest "XL" series speakers), almost no interaction between the drivers, and an extremely easy load on the amp.

The link above describes the implementation fairly thoroughly, with some more tech stuff here.

These Joseph Audio speakers are simply the best sounding speakers I've ever heard. I have to believe it's the Infinite Slope crossover tech along with their metal cone drivers. 

[Duke]

Roger, I can think of at least one highly competent loudspeaker designer who would not agree with your conclusion, though I can't speak to how he would respond to each of your points along the way.  He did not find the (more complex and more expensive) active version of his top-of-the-line loudspeaker to outperform the passive one: 

http://www.diyaudio.com/forums/showthread.php?s=&postid=1542837&highlight=#post1542837

At one time I worked fairly closely with Earl Geddes, and assembled several of the speakers he is referring to there.  The passive components he uses are high quality but not exotic.  He has tested that design to 130 dB SPL.  I read elsewhere that you attribute the use of passive crossovers to laziness on the part of the designer, and I can assure that Earl Geddes is anything but lazy.  And he has an engineer's emphasis on cost-effectiveness (though technically he's a physicist). 

I could accept that the average active crossover outperforms the average passive one, but based on Earl Geddes' comparison it sounds to me like highly competent versions of the two converge in perceived sound quality. 

That being said, there are systems where a passive crossover simply is not feasible, and the only practical solution is an active one.  The Emerald Physics CS-2, Linkwitz Orion, and Sonicweld Pulserod come to mind.  I have a somewhat unorthodox concept in the back of my mind that would only be practical in an active system, but certain parts would be quite expensive to develop.

Note that the eye may be offended by the visual complexity of a passive crossover, but the amplifier does not see that - instead it sees the resulting impedance curve, which may or may not be a good match with that amplifier's characteristics.  If the designer so intends, in some cases passive components can result in a more amplifier-friendly impedance curve than the individual drivers would present if connected directly.

Duke

[Russell Dawkins]

I think this is an important topic and is well worth discussing.

[kyrill]

not being an EE but with sensitive ears i COMPLETELY AGREE with Russell


So I hear a magnitude of difference when actively bi or tramping a speaker by bypassing its internal Xovers with my DEQX

and those many audiophile single driver lovers dont love those drivers for no reason
also single drivers with no Xovers makes many amps, happy amps.
the only reason for xovers is costs, ppl belief triamping is much more expensive and cumbersome and it is also easier for the speaker manufacturer to "control" or predict how its product will sound like

[TomS]

Great topic.  I look forward to hearing more of our manufacturers chime in with their experiences (thanks already, Duke and Roger).  Bob Smith of SP had a lot of great insight into these choices a while back and I know Jim Salk offers both a standard passive speaker level and used to have an active DEQX version of the HT-3.  Hopefully Earl Geddes will stop back by too. 

As Roger suggested, the really interesting "tweener" (but largely ignored) is the passive line level, maybe with buffers.  There have been some versions over the years, but usually implemented with lousy sounding op amps and cheezy power supplies.  I could be wrong but I thought the old Dalquist DQ-LP1 was along those lines.  Positioning the DSP XO as just for "tuning" use by the speaker developer, then fixing the design for final production with low power handling passives at line level makes a lot of sense.  A number of people use the DEQX in just this way, though the final design is often implemented as speaker level.  Looking at what's going on in the EP CS2 DCX as an example though, I doubt it's quite as simple a matter to realize it with passives, so perhaps that's a trade-off Clayton Shaw has accepted (sonic effects of conversions and DSP manipulation).  On the other hand, Bob has been very successful in the SP's using massively industrial strength Mundorf components for his speaker level xo's, though it takes some serious power.  The low distortion and extreme headroom of his designs indicate it can definitely be done correctly, though some of that may be the contributions of other aspects of his designs - waveguide, driver choices, cabinet, etc.  Ultimately it's a total system design, so these guys have to make choices.

Good stuff - bring it on!

[Vapor Audio]

The truth is passive crossovers do so much more than just rolloff drivers at certain slopes.  I'm about to walk out the door, delivering a pair of speaks to my Uncle ... and taking my daughter swimming at his place

I'll just throw this out for thought before I go. 

How can a speaker deisgner KNOW the end-user is hearing what they're supposed to be hearing unless what's delivered into their hands is a finished product?  You advocate asking for a speaker with no crossover, is the builder supposed to also deliver a transfer function, or just hope that the end user will get it close?  And if they don't get it close and are unhappy with the speaker, what then ... blame them?
 
That's the reality of why to use passive networks, there's probably <5% of the audiophile community that can take raw drivers, measure and analyze them correctly, and design a network that optimzes their capabilities.  Things like driver cone/motor energy storage and break-ups, distortion components, phase response, step response to achieve time alignment, overall impedance, off-axis response and lobing ... to name a few ... are ALL considered and weighed by the designer.  There are well-known designers who don't even look at the FR response until they're well into the design process, phase and step are  used exclusively in beginning phases of design. 

And on top of that passive networks not only can address and correct these things, they can do it individually to match the L/R speaker ... and deliver guaranteed quality control. 

I'll leave arguments over 'quality' to the engineers.  I think the burden of proof lies on the line-level guys shoulders.  If you're talking simple line-level crossover slopes, they simply don't have enough flexibility ... if you're talking about a full active device like the DEQ, then they all use hundreds more components than any passive, and plenty of potential for degredation. 

[avahifi]

Hope you don't mind my thoughts on this issue.

My concerns pretty much revolve around the musical quality of the electronic crossover.  I suspect it could be considered to be basically another line level preamp stage (with or without gain) in series with the main preamp and amplifiers.  My thoughts regarding the overall performance of an audio system has always been that the system performs up to the level of the weakest link there.  Complex electronic crossovers with all the necessary control functions for adjustable gain, crossover slope, and pole points for each driver almost always use integrated circuit active drivers for the necessary electronic functions.  It seems a bit strange to me for someone who loves tube preamps and tube power amps to not hear what a box chock full of ICs is doing to his system musicality, for example.

Passive line level crossovers much be driven by the preamplifier ahead of it.  This can place an unhappy capacitive load on the preamp line stage unless the preamp is designed to drive significant loads (some are, others are not).

A purpose designed electronic crossover with true audiophile active circuits precisely tailored to a specific loudspeaker design might very well indeed provide the best possible results.  But I wonder then if the musical benefits of the electronic crossover and two or more power amplifiers will be cost effective in comparison to a good speaker level crossover driven by one excellent full range amplifier.

Sometimes the the line level crossover will win, sometimes not, your results may vary.

Regards,

Frank Van Alstine

[Roger A. Modjeski]

The only passive speakers that consistently sound better to my ears than the best active speakers I've ever heard to date, are the Joseph Audio lineup. These use their patented "Infinite Slope" technology, which results in a 240db/octave transition (120db/octave in their latest "XL" series speakers), almost no interaction between the drivers, and an extremely easy load on the amp.

The link above describes the implementation fairly thoroughly, with some more tech stuff here.

These Joseph Audio speakers are simply the best sounding speakers I've ever heard. I have to believe it's the Infinite Slope crossover tech along with their metal cone drivers. 

I went to the links given to Joseph Audio and learned nothing of their technology. They do a good job of not telling you what is going on. Here is a link to what is going on: http://www.freepatentsonline.com/7085389.html

Scroll down about 20% of the page and you will find the schematic that the patent is based on. This 3 way crossover employs 5 caps, 3 inductors, 4 resistors and 2 iron core transformers.

Something they don't mention and something I have not seen discussed is off axis performance. That's what the person next to you is hearing. Depending on the relation of wavelength (speed of sound/freqency) to cone diameter it may not be wise to quickly (120 dB/octave) change from one driver to the next. Measured on axis there will not be a problem. Measured off axis there will be sharp peeks or dips as the woofer transitions to the mid and as the mid transitions to the tweeter.

[Roger A. Modjeski]

I believe I said the dealers and listeners are the lazy ones. The speaker designers are far from lazy. I admire their efforts to use a most awkward tool (the speaker level crossover) to do a job that is far more elegantly done at line levels. Since many speaker designers use easily adjustable active crossovers to determine crossover points, they would have a much easier job if they just handed over the slopes and crossover points to the buyer. Then the buyer could order up an active or passive line level crossover.

Passive speaker level crossovers are difficult to design for several reasons that go away in a multi-amped system.  Because dynamic drivers present frequency dependent impedance bandaids like Sibel networks are needed to help the crossover see a fairly constant load. In a multi-amped system with amplifiers of decent damping (4 or more) the Zobels are no longer needed.

[Roger A. Modjeski]

The truth is passive crossovers do so much more than just rolloff drivers at certain slopes.  I'm about to walk out the door, delivering a pair of speaks to my Uncle ... and taking my daughter swimming at his place

I'll just throw this out for thought before I go. 

How can a speaker designer KNOW the end-user is hearing what they're supposed to be hearing unless what's delivered into their hands is a finished product?  You advocate asking for a speaker with no crossover, is the builder supposed to also deliver a transfer function, or just hope that the end user will get it close?  And if they don't get it close and are unhappy with the speaker, what then ... blame them?
 
That's the reality of why to use passive networks, there's probably <5% of the audiophile community that can take raw drivers, measure and analyze them correctly, and design a network that optimizes their capabilities.  Things like driver cone/motor energy storage and break-ups, distortion components, phase response, step response to achieve time alignment, overall impedance, off-axis response and lobing ... to name a few ... are ALL considered and weighed by the designer.  There are well-known designers who don't even look at the FR response until they're well into the design process, phase and step are  used exclusively in beginning phases of design. 

And on top of that passive networks not only can address and correct these things, they can do it individually to match the L/R speaker ... and deliver guaranteed quality control. 

I'll leave arguments over 'quality' to the engineers.  I think the burden of proof lies on the line-level guys shoulders.  If you're talking simple line-level crossover slopes, they simply don't have enough flexibility ... if you're talking about a full active device like the DEQ, then they all use hundreds more components than any passive, and plenty of potential for degradation. 

Turbo,

Thanks for inviting me to air these points in the lab. Let me more carefully state what I am suggesting.

I don't expect the user to figure that out. I request that the speaker designer publish the slopes and crossover points. Kudos to those who already do.

Left to right matching is usually done by the speaker maker measuring and matching the individual drivers. I assume he would still do that in a speaker sans crossover. If he decides to sell you unmatched drivers (at a good discount) the user can easily achieve matching with separate left and right output pots on the line level crossover. Do you know manufactures who match L/R by fooling with resistors in the crossover? If so they are doing it the hard way. I am constantly amused by those who give their undying respect to designers who create excellent executions of bad ideas.

[bummrush]

I wonder what Chrishma Audio says

[Roger A. Modjeski]

Hope you don't mind my thoughts on this issue.

My concerns pretty much revolve around the musical quality of the electronic crossover.  I suspect it could be considered to be basically another line level preamp stage (with or without gain) in series with the main preamp and amplifiers.  My thoughts regarding the overall performance of an audio system has always been that the system performs up to the level of the weakest link there.  Complex electronic crossovers with all the necessary control functions for adjustable gain, crossover slope, and pole points for each driver almost always use integrated circuit active drivers for the necessary electronic functions.  It seems a bit strange to me for someone who loves tube preamps and tube power amps to not hear what a box chock full of ICs is doing to his system musicality, for example.

Passive line level crossovers much be driven by the preamplifier ahead of it.  This can place an unhappy capacitive load on the preamp line stage unless the preamp is designed to drive significant loads (some are, others are not).

A purpose designed electronic crossover with true audiophile active circuits precisely tailored to a specific loudspeaker design might very well indeed provide the best possible results.  But I wonder then if the musical benefits of the electronic crossover and two or more power amplifiers will be cost effective in comparison to a good speaker level crossover driven by one excellent full range amplifier.

Sometimes the the line level crossover will win, sometimes not, your results may vary.

Regards,

Frank Van Alstine

Frank,

Thanks for your comments. I have great respect for your contribtions to audio over many, many years.

What I am suggesting is passive line level with a very few components. I have built several two way, 6dB/octave units for MR customers for $250. Most preamps do fine with them. Buffering is available if needed.

While adjustable crossovers are applicable for speaker design and experimentation there is no need for the bi-amp listener to go down that road.

Although there are good full-range amplifiers out there, including mine, we both know that the output transformer for a tube amp whose bandwith is optimized for the midrange/treble can be much smaller not to mention economical. As I often tell audiophiles, "If you take two octaves off the bottom end of the amp you can put them on the top." Furthermore the output transformer will have less copper and iron and sound better for their absence.

For those who want to keep their crossover as they change speakers I offer the RM-3. The resistors and capacitors that determine frequency and slope (up to 24 db/octave) are on plug in cards that are easily changed out the back via a removable plate. I even attached the two thumb screws to the cover so they can't get lost.

For the ultimate in simplicity I eliminate the need for a preamp alltogether by adding two inputs and a volume control to the RM-3. A lot of cabling is eliminated which alone improves the sound. The user can connect two sources directly to the crossover. The high and low outputs are buffered so that long or short interconnects can go directly to the amplifiers.

[Vapor Audio]

Turbo,

Thanks for inviting me to air these points in the lab. Let me more carefully state what I am suggesting.

I don't expect the user to figure that out. I request that the speaker designer publish the slopes and crossover points. Kudos to those who already do.

Left to right matching is usually done by the speaker maker measuring and matching the individual drivers. I assume he would still do that in a speaker sans crossover. If he decides to sell you unmatched drivers (at a good discount) the user can easily achieve matching with separate left and right output pots on the line level crossover. Do you know manufactures who match L/R by fooling with resistors in the crossover? If so they are doing it the hard way. I am constantly amused by those who give their undying respect to designers who create excellent executions of bad ideas.

Well, I'd submit that most if not all the speaker manufacturers here only ship matched pairs of final speakers ... I know when I build something for a customer I settle on nothing less.  There ARE significant differences, even between sequential numbered drivers from high end manufacturers.  And I've often seen those differences magnified once the driver is placed on my cabinet baffle.  The L/R matching is HUGE in determining the width, depth, and solidy of a soundstage.  It's absolutely crucial, and that's why the builders here do it ... because we're not the Polk's of the World, we cater to a discriminating clientel. 

Now can the same thing be done with an active that takes complex transfer functions, of course it can.  But like I said, then we're not talking about simple low-component-count passive line-level filters, we're talking about units like the DEQ that have hundreds of components of questionable quality and a cheap power supply ... how's that a theoretical improvement over passive networks with components that have been highly optimized (like Mundorf, Sonicap, Alpha Core, etc). 

True you don't need a Zobel with active xovers, but Zobels are about the easiest part of the passive network to implement ... the simulator always nails em, and from there all there is to do is tweak the Q if you want some shaping. 

My point is that passive networks are the de-facto standard.  When I see a post like your original that only points out theoretical advantages of an active network, while glossing over it's disadvantages ... I think to myself "prove it".  Personally I'd never put a stock DEQ in my audio chain, and even a modded one I'd be wary of.  Passive line-level networks simply can't do what's needed to deal with the vast majority of drivers on the market ... active units aren't built to the standard those here expect, and even if they were they're much more complex. 

The main advantage I see to an active network and multiple amps is being able to eliminate back-emf, but that's not exactly a major concern.

[Vapor Audio]

Oh, and thanks for posting here Roger so we can all chat about it    I definately want to check out your room (if you get one) at the RMAF!

[JoshK]

Roger,

Aesthetically I completely agree with you and feel this is one of the advantages that a knowledgeable DIY'er has in his favor over someone who can only buy commercially.  However, I think there are a number of practical issues left to be addressed.

1)  There is no mention of BSC in this discussion.   Most off the shelf active crossovers make no provision for the 2pi to 4pi transition, that I know of.

2)  Audiophiles with their insistence on every conceivable crazy preamp/amp combos wouldn't always mate the line level crossovers to appropriate preamps and amps and thus end up with results far off what the speaker designer had intended.  E.g. passive line level driven by passive preamp.  Mixing set amps with plate amps without proper ways of dealing with the radically different drive requirements. 

3)  You are asking the speaker designer to give up freely his one real value added proposition.  The crossover is his IP that sets him apart.  Anyone can see the drivers he used and the box he made and copy it.  Speaker designed market their IP as the value proposition.  Would you free give away your amp design schematics?   I guess I see the only thing keeping a commercial speaker from being a commodity is the crossover.
Notice I am not saying anything about the real value of this IP, just how the manufacturer makes his money.  Theoretically, a speaker designer could make the passive line level crossover and deliver it with his speakers and have strict impedance/drive requirements for the preamp/amp that mate with it, but that would change the landscape and be a hard sell.

[Roger A. Modjeski]

Turbo,

Thanks for inviting me to air these points in the lab. Let me more carefully state what I am suggesting.

I don't expect the user to figure that out. I request that the speaker designer publish the slopes and crossover points. Kudos to those who already do.

Left to right matching is usually done by the speaker maker measuring and matching the individual drivers. I assume he would still do that in a speaker sans crossover. If he decides to sell you unmatched drivers (at a good discount) the user can easily achieve matching with separate left and right output pots on the line level crossover. Do you know manufactures who match L/R by fooling with resistors in the crossover? If so they are doing it the hard way. I am constantly amused by those who give their undying respect to designers who create excellent executions of bad ideas.

Well, I'd submit that most if not all the speaker manufacturers here only ship matched pairs of final speakers ... I know when I build something for a customer I settle on nothing less.  There ARE significant differences, even between sequential numbered drivers from high end manufacturers.  And I've often seen those differences magnified once the driver is placed on my cabinet baffle.  The L/R matching is HUGE in determining the width, depth, and solidy of a soundstage.  It's absolutely crucial, and that's why the builders here do it ... because we're not the Polk's of the World, we cater to a discriminating clientel. 

Now can the same thing be done with an active that takes complex transfer functions, of course it can.  But like I said, then we're not talking about simple low-component-count passive line-level filters, we're talking about units like the DEQ that have hundreds of components of questionable quality and a cheap power supply ... how's that a theoretical improvement over passive networks with components that have been highly optimized (like Mundorf, Sonicap, Alpha Core, etc). 

True you don't need a Zobel with active xovers, but Zobels are about the easiest part of the passive network to implement ... the simulator always nails em, and from there all there is to do is tweak the Q if you want some shaping. 

My point is that passive networks are the de-facto standard.  When I see a post like your original that only points out theoretical advantages of an active network, while glossing over it's disadvantages ... I think to myself "prove it".  Personally I'd never put a stock DEQ in my audio chain, and even a modded one I'd be wary of.  Passive line-level networks simply can't do what's needed to deal with the vast majority of drivers on the market ... active units aren't built to the standard those here expect, and even if they were they're much more complex. 

The main advantage I see to an active network and multiple amps is being able to eliminate back-emf, but that's not exactly a major concern.

Turbo,

We are both giving long responses to this question. This is the only forum I participate in and thus am not fully knowledgeable about partial quoting or the most efficient way of going about this rather complex discussion. Just this morning I completely lost my reply to Frank Van Alstine and had to start all over again.

Now to the technical point you have raised.

I am not suggesting Digital Crossovers for high end systems. I have already mentioned their shortcomings.

A simple zobel cannot fix the loading of a driver if that driver's impedance rise is anything other than 6 dB/octave. I have yet to see a driver whose impedance rises at 6dB/octave, have you? In my opinion Zobel networks in crossovers are bandaids. On the other hand they are very useful in amplifiers and I use them when needed, but they need to be in the amplifier or as close to the output terminals as possible. Their proper application is before the output choke in solid state amplifiers. On the speaker side of the choke they are worthless. They actually work with the output choke to load the amp at high frequencies where the speaker cables and speakers do not.

Transfer functions? Just who is really writing those for speaker crossovers, how complex are they and how are they being implemented?

Just because speaker level crossovers are the "de-fecto standard" doesn't make them good.

What are the disadvantages of line level crossovers as you see them?

What's the point of back EMF? The amplifier has to deal with that whether the speaker level crossover is there or not.

[Roger A. Modjeski]

Josh,

Forgive my ignorance but what is an IP and a BCS?

One of the problems I have with the use of these abreviations is how do newbee's find what they mean. Is there list somewhere?

As to the technical issues like mating a passive crossover with a passive preamp the solution is education. Let's not be so lazy about a hobby we all love. "Knowledge is power" and knowledge lets us out of the box the dealers and manufactures want to keep us in.

Any maker whose crossover is the only thing that he has to hang his hat on is in a mighty poor state of affairs. High end speakers have become more works of art in the past years with exotic woods expertly finished and cabinets made of materials with skills that are not available to the average builder. Most high-end speaker makers claim to modify and match the drivers. Is the hobbyist going to buy a dozen drivers to find two that match?

In my experience there are very few people who would do as your suggested to copy a speaker. The people who make their own speakers from scratch would actually benefit from a line level crossover saving the time and expense of working out one at the speaker level.

[JoshK]

Roger,

Sorry... I guess I thought it was clear in the context of the topic, but I have been there where the acronyms weren't obvious.

IP = intellectual property
BSC = baffle step correction, or the baffle enduced 2pi to 4pi radiation change; correction required to match the levels of low frequency with the higher frequency (not always conveniently at the crossover between drivers).

[JoshK]

Mild tangent.... here is a thread with an example of a diy'er who created such a passive line level crossover.  Unfortunately there is more discussion about the preamp then the speakers this was intended for.

The Water Babies thread