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Learning about crossovers - where to begin?

Discussion in 'Home Theater Projects' started by Kenneth Harden, Mar 16, 2006.

  1. Kenneth Harden

    Kenneth Harden Well-Known Member

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    I will cut to the chase. I would like to learn about designing and making crossovers. Initially, I will be looking at simple, inexpensive 2-way crossovers.

    Any books, websites, etc. where I can learn the basics?

    Are there master designs you normally use, but just use different values of parts to change frequency and other factors?

    Thanks!
     
  2. Patrick Sun

    Patrick Sun Moderator
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    You can start here. But to do it correctly, you need a measuring setup (to capture frequency response of the individual drivers mounted in the front baffle of the speaker, as well as its impedance profile and phase profile, in order to use the crossover design programs, like LspCAD or LEAP, to achieve optimum results).
     
  3. Kenneth Harden

    Kenneth Harden Well-Known Member

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    Thanks Patrick.

    As a long shot, if I have a computer (duh, I'm posting on HTF!), what would it cost for the basic software and hardware to do what is needed for a 'competent' (not Wilson Audio, JM Labs, Harman Internationl stuff) test setup?

    Are we talking a few grand, or tens of thousands?

    Thanks!
     
  4. Patrick Sun

    Patrick Sun Moderator
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    LspCAD and LEAP aren't too cheap, from like $200 for LspCAD standard to $980 for LspCAD pro, or LEAP, which is $795 for enclosure design, and $795 for crossover design or $1495 for both.

    Madisound also offers LEAP designs for a fee.

    If you wanted to do a setup with a microphone to gather driver measurements, here's a link.
     
  5. Kenneth Harden

    Kenneth Harden Well-Known Member

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    Patrick,

    Does not look like FREE designs (unless I missed something), but $30 for a MTM design is a really good deal! Thanks for the lead!
     
  6. Kenneth Harden

    Kenneth Harden Well-Known Member

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    I noticed a lot of the 'free' programs are setup so you put in the drivers T/S parameters, and then you tell it what you have in mind for the crossover, and it will show you the projected frequency responce and all that.

    I need to take a step backwards and learn how to actually DESIGN a crossover - what and how the various compents are. As it is now, I know there are cool little resistors, caps, etc. you solder together and they do stuff [​IMG] - I know nothing about design on them.

    Thanks for the help!
     
  7. Patrick Sun

    Patrick Sun Moderator
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  8. Kenneth Harden

    Kenneth Harden Well-Known Member

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    Agh! Sorry, my bad [​IMG]

    Yeah, the issue I am seeing is the software will show me the output when I feed it crossover designs...but I need to learn about how to make a crossover first! I still can't figure out if it is more of a art or a science!

    Thanks!
     
  9. Joe-M

    Joe-M Member

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    The cookbook is fine for intermediate and advanced reading on the theory of speakers building. For a novice, I recommend Designing, Building, and Testing Your Own Speaker System by David B. Weems. This is a fine book for explaning driver selection, enclosure design and crossover design. Once you read this, you will be more than ready to use the cookbook.

    As a scientist, I can tell you that speaker building isn't a true science. It relies on scientific fact but with the many variables associated with it, it is something of an art as well. But you must start with the basics and go from there.

    I too am somewhat of a novice but but have been spending many hours on the theory and have experience with some two-way designs. I am currently looking at building a three-way system akin to the Genesis Physics 66. This is a three-way design with a tweeter designed by Huw Powell (humanspeakers.com). His web site gives brief but educational essays on various topic in speaker build. He also states his opinions on various other audiophile topics.
    A very good read.
    For a good review of the drivers he builds here is the link: (ldsg.snippets.org/vendors/human.php3)

    Good Luck and happy learning,

    Joe
     
  10. Joe-M

    Joe-M Member

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    a good place to get the books described above is here:
    mfr-eng.com/index.htm

    They have excellent prices and cheap shipping.

    Have at it!
     
  11. ThomasW

    ThomasW Well-Known Member

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    Here's how it works.......

    First you decide on the drivers you want to use, (a bit hard for a noobie). Then you buy the drivers and mount them on the baffle you intend to use for the speaker. (Choice of the baffle size and shape depends on the kind of loading you want the drivers to have.)

    With the drivers mounted you take a series of measurements of the frequency response of each driver. You then import that measured data into a modeling program and start designing the XO. (plan on $200-$1000 mininum for proper test equipment and software.)

    After several passes with the software optimizer, you buy the parts for the XO and build it up. (BTW you must know how to design a crossover in order to use any design software)

    Now you start a new series of measurements using the crossover. You adjust the values of the components in the XO for optimal performance. (hint plan on doubling the cost for the components IF you've never built a speaker before)

    Or ............

    You can build someone's tested and proven design.
     
  12. Kenneth Harden

    Kenneth Harden Well-Known Member

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    How do you learn HOW to design a crossover so you can use the design software?

    Thats the sticking point! It seems once you get the basics down, there are tons of resources available (software, books, parts, etc.)
     
  13. Greg Monfort

    Greg Monfort Well-Known Member

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    Greets!

    Historically, you learn electrical filter theory either in college or at the library, then once you have a handle on it you step up to acoustic filter theory.

    That said, the aforementioned Weems book is pretty good, as is Ray Alden's Advanced Speaker Systems, as are these:

    http://www.trueaudio.com/st_mr1.htm
    http://www.trueaudio.com/st_mr2.htm
    http://www.trueaudio.com/st_xov_1.htm
    http://www.trueaudio.com/st_zobel.htm
    http://sound.westhost.com/beginners.htm
    http://sound.westhost.com/miscc.htm
    http://sound.westhost.com/vda.htm
    http://sound.westhost.com/bafflestep.htm
    http://sound.westhost.com/z-effects.htm
    http://sound.westhost.com/lr-passive.htm
    http://sound.westhost.com/parallel-series.htm
    http://sound.westhost.com/pcmm.htm
    http://www.pispeakers.com/Speaker_Crossover.doc

    Anyway, there's tons of info on the 'net, but if you can get the basics down, then you can do your own research/experimentation. Understand though, that filter theory makes certain ideal assumptions, so textbook XO's are at best just bandaids to protect the drivers against over excursion.

    Also, two ways can be hard enough, but each added XO point increases complexity ~exponentially. Ask Pat Sun (moderator) if he still has his well documented 3-way crossover design trials n' tribulations on line to read.

    GM
     
  14. Dave Poehlman

    Dave Poehlman Well-Known Member

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    HERE is a site with 2-way formulas so you can do the math yourself.

    I've been looking at getting one of these. I think if you couple it with a Rat Shack SPL meter, you'd have a measurement set up good enough for the curious noob or casual builder.
     
  15. ThomasW

    ThomasW Well-Known Member

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    Nope using a generic crossover 'forumla' isn't a good idea. Nothing is optimized for the performance of the specific speakers and baffle being used.

    Woofer Tester is designed to measure T/S parameters, not measure frequency response on a baffle. Doing that takes gated time domain (ETF/LMS) measurements. Those are done using a test mic, mic preamp with phantom power, a PC, and the appropriate software. Price of admission is $200, + the PC with a duplex soundcard. The high end solution is something like Praxis for $1000

    If all one has is the RS meter and a online crossover design program, your chances for making a good sounding speaker are ZERO! You'd get a better sound speaker buying something from Best Buy....
     
  16. Dave Poehlman

    Dave Poehlman Well-Known Member

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    "good sounding" is a subjective term.. so, I'm not sure I agree with that.

    My point was, someone could drop a couple hundred bucks on equipment and get an understanding of the process and forces at work here. Once they reach a level where they want to pursue the more minute tweaks, they can then decide to invest $1k.

    'Cause let's face it, building speakers isn't a very practical hobby for most people.
     

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