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    jaygeorge1979's Avatar
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    Designing a crossover for a DIY speaker project

    alright guys i need some more help here...i have been browsing over alot of the DIY projects lately and i cant figure out how these ppl design the crossovers...i understnad how to build them ( i am an engineering student) but i cant figure out how they can choose a driver and know:

    A. How to design the box, how big, seperate chambers, etc
    B. How to design a crossover that fits the speaker perfectly

    anybody wanna take a stab at teaching me?



    gooooooose




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    Re: Designing a crossover for a DIY speaker project

    You need to buy a book to get the general idea, the topic is too advanced to cover in
    one post.

    Pick a random midwoofer from PE with charts and maybe we can give you a
    though process on how to tackle the crossover issue, simplified.

    If you really want to expedite your learning, do this;

    1. Buy a woofer.
    2. Buy a midwoofer.
    3. Buy a tweeter.
    5. Buy a Behringer DCX2496.
    6. Buy 1 amplifier channel, full range.

    This will be a test bench rig so you can learn FAST on what goes on.
    I can guarantee that you will understand if you follow my lead.




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    Re: Designing a crossover for a DIY speaker project

    http://www.partsexpress.com/pe/showd...number=296-145

    i chose this audax midwoofer cuz it looked kool...it has all the charts on there, so if someone could enlighten me

    also, i have been looking at the passive crossover explanation on the12volt.com, and it has cleared a little of it up, but im still no understanding why to build them certain ways depending on which speaker you get...anyone?

    thx thylantyr



    gooooooose

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    Re: Designing a crossover for a DIY speaker project

    Quote Originally Posted by thylantyr
    You need to buy a book to get the general idea, the topic is too advanced to cover in
    one post.

    Pick a random midwoofer from PE with charts and maybe we can give you a
    though process on how to tackle the crossover issue, simplified.

    If you really want to expedite your learning, do this;

    1. Buy a woofer.
    2. Buy a midwoofer.
    3. Buy a tweeter.
    5. Buy a Behringer DCX2496.
    6. Buy 1 amplifier channel, full range.

    This will be a test bench rig so you can learn FAST on what goes on.
    I can guarantee that you will understand if you follow my lead.
    how much am i looking at spending? what is a behringer DCX2496? wouldnt i also need to get crossover parts/etc? how about a box?



    gooooooose

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    thch's Avatar
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    Re: Designing a crossover for a DIY speaker project

    typically there are 3 engineering methods to use:

    1.) get drivers that have a large overlap in bandwidth, then use a simple filter.
    2.) use a complex, steep filter with speakers that have little overlap in bandwidth.
    3.) use modeling software to find a middle ground for speakers with some overlap using moderatly complex filters.

    from here, the crossover points are chosen based upon driver performance. drivers have well-known issues at both high frequencies (beaming, breakup) and low (overexcursion, T/S model). these issues help to define usable bandwidth. for instance, a speaker may have an excelent response up to 3khz, but then have a terrible response at 4khz. this means that even with a steep filter, the cutoff may need to be 2khz.

    generally, filters should be below 300hz and above 3khz. 300-3khz is the most important band for voice recognition. this is only a loose rule though. i've used filters at 2khz with no issues.



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    Re: Designing a crossover for a DIY speaker project

    Quote Originally Posted by jaygeorge1979
    how much am i looking at spending? what is a behringer DCX2496? wouldnt i also need to get crossover parts/etc? how about a box?
    DCX2496 is a digital crossover. $250 shipped.
    Amplifier - you choose.
    Drivers {individual speakers} - you choose

    Get a cheap dome tweeter, cheap midrange to start the learning process.
    Connect the DCX to your source and the speaker to your amplifier and play
    with the digital crossover so you can understand what happens when you
    change settings.

    http://www.behringer.com/DCX2496/index.cfm?lang=ENG

    For DIY, I only use 'active systems', one without passive crossover because it's
    elite.

    For business, it's not practical to design an 'active loudspeaker' system, but
    they do exist. It's more economical to do passive crossover design and just
    hook up the speaker to an amp.

    But, many DIY loudspeakers are passive crossover based too.

    I prefer complete control over the drivers in loudspeaker design, hence all
    active system so I can change settings.

    You could develop on an active test bench to find the best settings then try
    to make a passive crossover to mimick performance.




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    Re: Designing a crossover for a DIY speaker project

    Quote Originally Posted by jaygeorge1979
    http://www.partsexpress.com/pe/showd...number=296-145

    i chose this audax midwoofer cuz it looked kool...it has all the charts on there, so if someone could enlighten me

    also, i have been looking at the passive crossover explanation on the12volt.com, and it has cleared a little of it up, but im still no understanding why to build them certain ways depending on which speaker you get...anyone?

    thx thylantyr
    Everyone has their approach to loudspeaker design. My metho involves more
    listening to drivers than measuring them .. because in the end, I plan to listen
    to them not measure them --

    I prefer a top-down approach to loudspeaker design. Start with tweeters and
    work down.... because an excellent tweeter is harder to get than mids. After
    you find 'your magic tweeter', find the matching midwoofer and so forth.

    The frequency response for that midwoofer {midrange/woofer} you linked is
    fine;
    http://www.partsexpress.com/pdf/296-145g.pdf

    Since my preference for audio is to use a tweeter that can perform well with
    a 2khz crossover, maybe as low as 1.5khz using a steeper slope like 8th order,
    we need a midwoofer than can play in this region well, with good SQ and
    no nasty frequency response anomies like cone breakup modes in this region or
    even higher.

    The next question to ask. Does the midwoofer sensitivity mate well with your
    tweeter? That midwoofer says 84dB sensitivity which is very low and inefficient.
    Second, xmax is rated for 2.7mm so you need to understand that high excursion
    isn't really possible with this midwoofer.

    If you use a tweeter with higher sensitivity then make arranges by designing
    an L-pad into the design to make sure you have a tweeter volume control to
    attenuate the treble.

    If you use an all active system, driver sensitivity matching is moot as you
    will adjust levels on the source side.

    What I like to do is make a list of driver candidates for a design and buy one
    of each and hook them up to listen to them, this will be the final judging phase
    on which one to choose. If you listen to enough tweeters and midranges,
    you start visualizing in your mind on which ones mate better to certain drivers.




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    Re: Designing a crossover for a DIY speaker project

    wow...that really helped alot

    is there anything about a tweeter that would make me want to use an 8th order crossover at 1.5kHz for the tweeter, or are you just saying that is what you prefer? once you decide 8th order 1.5khz, is there a calculator out there that tells you what value capacitor to use?

    how about for the midrange...if i want it to play freq between 300Hz and 3kHz, how do you figure out how to design that crossover?

    i am still trying to figure out if there are any characteristics of certain speakers or brands that help you figure out WHERE you want to cross it over...i understand that once you know what tweeter you are using, you want the mid to overlap...but how to figure out if that frequency for the tweeter is efficient for THAT tweeter?



    gooooooose

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    Re: Designing a crossover for a DIY speaker project

    Quote Originally Posted by jaygeorge1979
    http://www.partsexpress.com/pe/showd...number=296-145

    i chose this audax midwoofer cuz it looked kool...
    Just for future referance, please don't ever choose anything audio based upon looks.



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    More proof.
    Quote Originally Posted by Andrew_as View Post
    I need a program or something that will help me find mounting depth without having to build box and such...
    No, Andy, I'm sure the context is fine.

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    Re: Designing a crossover for a DIY speaker project

    Quote Originally Posted by UndercoverPunk
    Just for future referance, please don't ever choose anything audio based upon looks.

    You mean my audiobahn chrome flamed subs don't hit 189db's? What?....Liar!




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    Re: Designing a crossover for a DIY speaker project

    haha...i know...i just needed to pick one so that someone could explain to me how the system of deciding on crossovers works...which, i still dont quite get...see previous questions...



    gooooooose

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    Re: Designing a crossover for a DIY speaker project

    Here is something thylantyr said in one of his posts helping me design my line array... Main thing is the link.
    Or would it be better to make my own? I can solder, I just don't know anything about making a crossover.

    I think it would be better.

    read this and tell me what you think.
    http://www.caraudioforum.com/vbb3/sh...d.php?t=227180

    the passive crossover design will make or break that system so
    you need to choose the tweeter, ideally find one with response graphs
    to determine best crossover region to use then plan a strategy.

    Linkwitz Riley slopes are just better for SQ, i'd use those, but
    the LR 24dB/octave is more complicated to build and cost more
    because it has more parts.
    It has some good information and calculators on there, I found it helpful

    -Ryan
    Last edited by ballstothewall; 11-06-2005 at 07:02 PM.




  13. #13
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    Re: Designing a crossover for a DIY speaker project

    link is out




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    Re: Designing a crossover for a DIY speaker project

    Link Fixed




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    Re: Designing a crossover for a DIY speaker project

    wow...that IS beneficial...is the Linkwitz-Riley crossover the regular one that most ppl use?

    i didnt know that all you needed to calculate crossovers was speaker impedance...thought it would be more complicated

    i cant figure out how i would use taht calculator for a bandpass crossover for a midwoofer...say i wanted to filter out freq below 300 hz and above 2khz...how would i do that?



    gooooooose

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