Crossovers, minimalist vs Complex.
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JimPA
Distinguished Member
The series crossovers are simple and power efficent. Zero plane delay in sloped cabinet for mid bass and tweeter using Butterworth parameters gives phase coherence having voice coil centers close together. Using large gauge wire in coils has a lot to do with efficiency in crossovers. High order crossovers waste current.
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TerryO
Super Member
Series crossovers in most applications can be really hard to get right and I know of only a few people that really seem to have a handle on this. They aren't "simple" by any means, especially compared to parallel crossovers.
Now, if what you're saying is a first order crossover using a capacitor in series with the tweeter with (or without) a parallel crossover to a woofer, that "may" be understood by some people to be a series crossover, but it really isn't what is generally understood to be a series crossover.
The use of large gauge inductors, as you've stated, is an excellent idea as they are perhaps the largest contributor to the "sound" of a crossover, regardless of the type of capacitors in use. In the end it's really up to the designer to decide what trade-off are to be made and sometimes a smaller gauge inductor is called for.
Best Regards,
TerryO
JimPA
Distinguished Member
A series circuit has the cap and inductor in series with the current . The drivers are in parallel of the current. I have purchased many kits from a man who wrote the book on series and t-line dsigns. There are many common denominators I found in all of the crossover designs. I hate to post his name since the designs are owned and don't want to alienate any one. Enclosed is link to a series layout. I like to share info to help people achieve the best sound possible.http://www.humblehomemadehifi.com/Crossover.html
TerryO
Super Member
Well, you certainly found one of the fellows that has an inkling. :thmbsp:
Another one, in the States, that's very good at series crossover design is Dave Rosgaard. He wrote his proprietary software program to use solely with Series Crossovers.
Dave and I are very good friends and have done some collaborative work on a couple of designs. I also know for a fact, that Dave and "Mr. Humblehomemadehifi" (the mystery guest) have often corresponded about Series Crossovers over the years and I believe that some of the work shown on the linked site is a result of that correspondence.
Best Regards,
TerryO
carbonman
It's All About The Music
Richard Modafferi has in-depth knowledge of crossover design; he patented the "Infinite Slope" crossover used by JSE and currently used by Joseph Audio. The technology uses very steep slopes to minimize ringing with metal cone drivers and reduce wave interference between drivers in the crossover range.
There are more parts than found in a simple 1st or 2nd order crossover, but I was surprised to see how simple the circuit is. There is a lot of very advanced math in the design, way beyond me.
There are more parts than found in a simple 1st or 2nd order crossover, but I was surprised to see how simple the circuit is. There is a lot of very advanced math in the design, way beyond me.
4343
Super Member
Simple is as Simple does...
Actually, that IS a very simple crossover, compared to this one, and it's not even finished yet!
Anyone recognize it? (Points only to those of you that are NOT LHS members...)
I like simplicity, but sometimes its just not possible or the best solution.
Actually, that IS a very simple crossover, compared to this one, and it's not even finished yet!
Anyone recognize it? (Points only to those of you that are NOT LHS members...)
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jwalker
Well-Known Member
The math isn't that complicated if you have an EE degree. The "infinite" slope, really isn't "infinite" but rather quasi-elliptic. The basic idea revolves around cross-coupled filtered sections. In the patent, he used magnetic coupling of filter sections via transformers but similar functions can be achieved by coupling the electric-fields of resonators. These types of filters have been used for years in communications systems, but the patent was probably granted because of it's specific application to loudspeakers and other audio related filtering.
I've designed many cross-coupled filters for wireless communications systems by coupling resonators both magnetically and electrically, but these operated in the gigahertz range and were distributed vs. lumped. However, the principle is the same.
jwalker
Well-Known Member
TerryO
Super Member
That picture is a prime example of why people should make crossovers active.
Not to mention the giant increase in the price of copper in the last couple of years. It may turn out that active is cheaper.
Best Regards,
TerryO
JimPA
Distinguished Member
Without seeing a schematic I can't state an opinion on the crossover design. The key in series is constant voltage. With 8ohm drivers Re in parallel of tweeter and mid bass in 2 and 3 way designs are constant values in these designs using a wide variety of drivers. Choosing correct Re [X] value on tweeter+ achieves constant voltage. Knowing the values of C1 and L1 are another topic. Pretty close to textbook values after peaking the corner frequencies. Properly designed series circuits are far more amp friendly then parallel.
jwalker
Well-Known Member
Series crossovers are very rare in current production speaker systems, and anything above first order is even rarer. I think the problem is many of the CAD tools in use today can not properly synthesize high order series crossovers, so this alternative is rarely explored. IMHO, the reliance on these tools and mostly empirical tweaking seems to have supplanted basic engineering ability. It's one thing to be able to use the optimizer in a tool like LEAP and make small changes to cap values, but it's something completely different to understand what LEAP is actually doing.
I can only think of two companies that are actually building commercial systems with series crossovers. Fried and VMPS. I don't know what order series filters Fried uses, but VMPS use first order series crossovers almost exclusively.
Truthfully, I'd rather see a manufacturer take the time and effort to design drivers and select combinations of drivers correctly, so that they don't NEED super-complex crossovers.
IME, most complex crossovers are trying to make up for some deficiency or bad behavior in a driver. Breakup mode, resonance, bad cone geometry, and the like. Or, trying to make drivers work together, that simply are not well-suited to work together.
Now, there are some cases where complexity is added to "optimize" certain aspects of the behavior of a speaker/crossover system. Such is the case, when some manufacturers add impedance compensation circuits, to flatten the impedance response of a system, so that they take out amplifier dependence to some extent (i.e, a speaker with flat impedance will sound less different on different amps with different output impedance, than a speaker with drastically varying impedance). This is a special case, though...
Then other extreme (and I see this in Infinty designs, among others), is a crossover design that, due to the attempt to "force" drivers to do things they don't want to do, winds up with DRASTICALLY varying impedance... the crossover is "forcing" the amp to put out more power at a certain frequency, in order to "fill in" a response hole that would otherwise result. Some examples of this are high-Q low-pass and high-pass filters... they actually resonate themselves, and result in greater power transfer to the driver, at a frequency, than the driver actually would have connected directly to an amp. It's almost like a frequency-dependent transformer, of sorts. This is to be considered cheating, IMHO... the REAL solution is to pick drivers that INHERENTLY MATCH better, so you don't have to play these amp-sapping (and sometimes amp-blowing) games...
Regards,
Gordon.
IME, most complex crossovers are trying to make up for some deficiency or bad behavior in a driver. Breakup mode, resonance, bad cone geometry, and the like. Or, trying to make drivers work together, that simply are not well-suited to work together.
Now, there are some cases where complexity is added to "optimize" certain aspects of the behavior of a speaker/crossover system. Such is the case, when some manufacturers add impedance compensation circuits, to flatten the impedance response of a system, so that they take out amplifier dependence to some extent (i.e, a speaker with flat impedance will sound less different on different amps with different output impedance, than a speaker with drastically varying impedance). This is a special case, though...
Then other extreme (and I see this in Infinty designs, among others), is a crossover design that, due to the attempt to "force" drivers to do things they don't want to do, winds up with DRASTICALLY varying impedance... the crossover is "forcing" the amp to put out more power at a certain frequency, in order to "fill in" a response hole that would otherwise result. Some examples of this are high-Q low-pass and high-pass filters... they actually resonate themselves, and result in greater power transfer to the driver, at a frequency, than the driver actually would have connected directly to an amp. It's almost like a frequency-dependent transformer, of sorts. This is to be considered cheating, IMHO... the REAL solution is to pick drivers that INHERENTLY MATCH better, so you don't have to play these amp-sapping (and sometimes amp-blowing) games...
Regards,
Gordon.
SET12
Super Member
I prefer simple networks, low part counts, with relatively low values which allow one to explore the very exotic caps, inductors and resistors. All of which have transformed a $1000 speaker into a $10,000 one for me.
I also took the same approach with the rest of my system keeping it minimal while modifying my CDP and amps even further yet and I'm still not done, but am thoroughly enjoying the sound.
To get this kind of performance for my satisfaction I would have to spend an easy $10,000 for speakers instead of the $2000 DIYing.
They same is with the gear I can't afford $10,000 CDP's or $10,000 amplifiers so the only way I can is DIY for a fraction of the price. And I might add to a great level of satisfaction, gone are the days of buying and selling.
Photo of stock vs modified.
Current version
Also on the way are some C-Core Autotransformers that are likely to take My Forte's to an entirely new level of mid-range reproduction they are massive at what looks to be about 4 times the size of the Crites Autotransformers I now use at least, I'm hoping for a similar effect that are had from the North Creek 8AWG inductors which have superb dynamics, sense of ease and a great sense of space and when I say space, The Fortes with these crossover mods literally doubled their sound stage size which is something to hear to believe.
SET12
I also took the same approach with the rest of my system keeping it minimal while modifying my CDP and amps even further yet and I'm still not done, but am thoroughly enjoying the sound.
To get this kind of performance for my satisfaction I would have to spend an easy $10,000 for speakers instead of the $2000 DIYing.
They same is with the gear I can't afford $10,000 CDP's or $10,000 amplifiers so the only way I can is DIY for a fraction of the price. And I might add to a great level of satisfaction, gone are the days of buying and selling.
Photo of stock vs modified.
Current version
Also on the way are some C-Core Autotransformers that are likely to take My Forte's to an entirely new level of mid-range reproduction they are massive at what looks to be about 4 times the size of the Crites Autotransformers I now use at least, I'm hoping for a similar effect that are had from the North Creek 8AWG inductors which have superb dynamics, sense of ease and a great sense of space and when I say space, The Fortes with these crossover mods literally doubled their sound stage size which is something to hear to believe.
SET12
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JimPA
Distinguished Member
To many people buy a program and think they are speaker designers without understanding the basic theory. It has taken years of research to perfect design theories in enclosre and crossover designs. I agree with GordonW comments about optimizing drivers. Loudspeaker companies are very trendy. Kevlar was in fashion now carbon fiber etc. Price dictates what is used. Nomex was a neutral voice coil former and replaced by aluminum and kapton due to manu costs. Most people think poorly of bextrene and don't really know why it was phased out. I have Fried oem bextrenes that are efficent and take high currents that sound very neutral. at high spl levels. Polypropylene was cheaper to manu. It didn't require plastiflex and held up better in auto sound applications. Early poly had problems with surrounds detaching from the cone. Bextrene would deform in auto sound applications being exposed to direct sunlight in the heat of automobiles. Kevlar has the resonance peaks above crossover frequency.Paper cones in it's various forms are still a good choice. Purchasing books written by Vance Dickinson and David Weems are a good start for beginners to learn the basic theories. Back issues of Speaker Builder have most of the answers. There are many good drivers available but all are a compromise in one area or another. Which is better 3/4" or 1" domes, horns or planars.
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PioneerGuy75
Certified Lurker
PioneerGuy75
Certified Lurker
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bowtie427ss
Lunatic Member
WHOA!
I'm guessing that's NOT for a 2-way!
Cool stuff!
I recognize that as a Westlake crossover. Judging by the size it's for a BBSM15. There should be another one nearby as they're built in pairs with hand matched components.
I own a pair of BBSM10's that have a much smaller yet similarly complex and extensive network.
