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building towers, planned out, everything look ok?

Discussion in 'Home Theater Projects' started by JoeGibs, Nov 21, 2005.

  1. JoeGibs

    JoeGibs Well-Known Member

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    I built my first set of towers a few months ago, and you guys pointed out several flaws after i'd already constructed them, so before I even push the order button on anything, I want to make sure i'm not making any big mistakes again.

    Three way towers, one tweet, midrange, and midwoofer in each tower.

    Tweeters:
    DAYTON PT2B-8 PLANAR TWEETER
    http://www.partsexpress.com/pe/pshow...75-085&scqty=2
    [​IMG]



    Midranges:
    DAYTON DC50F-8 2" DOME MIDRANGE
    http://www.partsexpress.com/pe/pshow...85-010&scqty=2
    [​IMG]


    Midwoofers:
    DAYTON RS225S-8 8" REFERENCE SERIES SHIELDED WOOFER
    http://www.partsexpress.com/pe/pshow...95-366&scqty=2
    [​IMG]

    Crossovers:
    DAYTON XO3W-500/4K 3-WAY CROSSOVER 500/4,000 Hz
    http://www.partsexpress.com/pe/pshow...60-152&scqty=2
    [​IMG]


    Amplifier:
    I'm not completely sure on what i'm going to get for this yet. I found a crown amp that I think should work well, but I have the idea creeping in the back of my mind of finding an older yamaha, if possible.
    crown amp-
    CROWN XLS402B POWER AMPLIFIER
    http://www.partsexpress.com/pe/pshow...45-462&scqty=1
    [​IMG]

    I've used the midrange before, and I really like it, so i'm going with that again. I've used the 7" reference mid before, and also liked it, but to match the power of the other two drivers, I stepped it up to the 8" instead of the 7".
     
  2. ThomasW

    ThomasW Well-Known Member

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    You shouldn't use a generic crossover for ANY speaker.

    To properly build a speaker, measurements should be taken of the performance of each individual driver mounted in the baffle where you intend to use it. That specific data is then used to create the crossover SPECIFIC to the design.

    The Dayton RS woofer is a great driver, the midrange is so, so, and the planar tweeters are marginal at best.

    If you want to see the knowledge needed to properly design a speaker read the 1st post in this thread.

    Modula MTM design

    When you can do what Jon does, then design your own speakers. Until such time, copy a design created by someone with experience. That way you're guaranteed to get a good sounding design
     
  3. JoeGibs

    JoeGibs Well-Known Member

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    I dont know if i dare try and design something that complicated, its a little beyond me. Do you think i'd be better off doing something similar like that but something thats already been designed. Just so i can get the feel for the construction aspect of it and get my foot in the door with it.

    where could i find a list of already designed towers?
     
  4. ThomasW

    ThomasW Well-Known Member

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    It appears complicated because he provided all the data that was used to engineer the speaker.

    All you need to do is copy the design. The width of the baffle (11") is important as is the driver spacing

    If you want to make a tower version of it that's not a big deal. I can give you the information for the box

    [​IMG]

    These are pictures of the crossovers. You'd just copy them

    [​IMG]

    [​IMG]

    EDIT: I forgot that Pete Mazz already built a tower pair

    [​IMG]
     
  5. JoeGibs

    JoeGibs Well-Known Member

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    I dont want to go ahead and choose that design if i havent seen others. I may see something that i think i'd like better.

    also wondering what cost would be for something like this, for example the one showed above
     
  6. Ben Ch

    Ben Ch Active Member

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    ok Thomas, I hadn't seen Pete's MTM's...
    I'm sold.

    Too bad the pic is in front of those gorgeous line arrays.
     
  7. ThomasW

    ThomasW Well-Known Member

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    Parts cost is around $215/speaker excluding the cabinet.

    The cab in the pic was built by a professional cabinetmaker for his brother-in-law. You don't want to know what those would cost.
     
  8. JoeGibs

    JoeGibs Well-Known Member

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    I plan on making my own cabinents regardless of what drivers i end up going with. I spose they dont have to be towers as long as i can get the required air space in a bookshelf sized enclosure. I dont want to bother building something extravagant looking, because just like my bad habbit with car audio equipment, i'll most likely change it up and try something new just for the hell of it
     
  9. ThomasW

    ThomasW Well-Known Member

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    The tower enclosure makes slightly louder low bass. But the design as shown in Jon's tread is a perfect match for a sub. (and using a sub with any design having relatively small midwoofers is a very good idea)
     
  10. JoeGibs

    JoeGibs Well-Known Member

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    i'm running a 15" titanic for a subwoofer, so i'm not looking for anything loud on the low end in whatever new speakers i go with.

    are there any other designs that i can look at? i dont really know where to look for that kinda thing
     
  11. Dean Mar

    Dean Mar Well-Known Member

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    There are quite a number of designs as well as complete kits that can be found online. Try a search on this site as well as diyaudio.com and other sites.

    If you provide more information as to what you are going to use the speakers for (mainly home theater vs music etc.)and an approximate budget. You may get others here to give you some specific suggestions.
     
  12. ThomasW

    ThomasW Well-Known Member

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    Yep there are hundreds, if not thousands of DIY designs out there.

    Just type DIY loudspeakers into a Google search.

    However I doubt you'll find many designed by someone who's been engineering loudspeakers for ~30yrs, and is a twice published member of the AES (Audio Engineering Society), unless you go with one of Siegfried Linkwitz's designs... :wink:
     
  13. JoeGibs

    JoeGibs Well-Known Member

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    would there be anything wrong with running (4) of the Modula MTM design mentioned above? i remember in my last attempt at making towers, i was advised to not use two tweeters on the same plain. if i were to do 4 of them, as in 4 seperate enclosures, i'd most likely have a pair on right and a pair on left channels.
     
  14. ThomasW

    ThomasW Well-Known Member

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    Running 2 tweeters/side whether they're in one box or two boxes creates the same problem = comb filtering.

    Why the fixation with multiple tweeters?
     
  15. JoeGibs

    JoeGibs Well-Known Member

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    its not about the tweeters this time. the speakers mentioned above use two of the 7" dayton reference woofers, and in each of my towers i have now, there's two of the same. I want to get a little more output than what i have now, so i was thinking it might not hurt to run two pairs of these.

    but something else just popped into my head, my receiver has a speaker output for a center channel. how much of a noticeable difference does a center channel add? and is there anything that would pair up with the MTM design well?
     
  16. Michael Hartwig

    Michael Hartwig Well-Known Member

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    Have a look at full range speakers. I just finished a set of three (2 mains and a center). Integrated with my 15" Tempest sub I think they sound really good. There is no need to design crossovers.
    This a good site if you're interested in the full range route.

    http://www.diyaudio.com/forums/forum...?s=&forumid=51

    I used the Creative Sound Solutions FR125s drivers for my build. I put them in a miniOnken design box (plans found on CSS site).
    [​IMG]
     
  17. ThomasW

    ThomasW Well-Known Member

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    A center channel primarily plays the dialog from a movie

    If you want more output build the MTM and set it on top of a bass bin containing some woofers. That takes the low end workload of the MTM so they can play louder.
     
  18. JoeGibs

    JoeGibs Well-Known Member

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    i use my stereo mainly for playing music, as long as it played music when i have the receiver in 5 channel mode, i think that'd be my best option.

    as for the full range speakers, i've never been a fan of them. Thanks for the idea though
     
  19. JoeGibs

    JoeGibs Well-Known Member

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    k, so for my center channel, would a single modula mtm be fine? then another two to use as the right and left channels?
     
  20. MichaelSmith

    MichaelSmith Member

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    John has a specific design for the Modula Center. Here it is:

    Modula MTM-CT Design and Construction- Introduction

    Last updated 2-10-2005

    This thread is going to detail the driver measurements, contruction details, crossover design, and final performance tuning for the MTM speaker using two Dayton RS180 and a ScanSpeak D2904/6000-01 tweeter. This is intended to be a high bang for the buck system, but to get the optimum level of performance from these drivers, a slightly more expensive crossover is usually necesssary. Still, the bottom line looks attractive compared with the performnace. This post will be edited and updated to reflect work in progress as steps are completed.

    My personal versions of this design will be built in Parts Express 1 cu. ft enclosures designed for MTM's.

    The long Xmax of the Dayton RS180 and the low non-linear distortion suggests it should provide compeitive performance, as long as a lower crososver point is used.

    Measurement show that SS D2904/6000-01 offers low non-linear distortion and smooth wide frequency response; it should, since it's not exactly inexpensive. What it brings to the party is a very small footprint due to the use of nedymium magnets, and very low distortion due to the SD1 motor design from ScanSpeak.


    Drivers - The Dayton RS180


    The RS180 is a 7" aluminum cone driver using a phase plug, and featuring a relatively long Xmax for a driver of this type. Furthermore, as Mark K and MFK have shown, measured non-linear distortion and ETC tests are very good, competitive with well known drivers costing much more. However, like most metal cone drivers, they have upper range resonances which require more care in crossover design.






    Cabinet Design and Construction

    I chose to develop these projects for the PE (Parts Express) cabinets, because for the money, it's very hard to beat the quality and finish considering the time involved. The cabinets are well braced internally, also.




    If you want to go deeper on the enclosure and use a larger port for more bottom end extension, then you may want to build something your self similar to the FP layout of the 1 cu ft enclosure.

    Shown below is the front panel layout diagram for the center channel MTM. The tweeter is offset substantially because this allows moving the midwoofers in close to each other, and produces a flattter boundary and diffraction behavior in the 1-3 kHz reigon, according to Baffle Diffraction Simulator.






    Crossover Design


    Top optimize the performance, considering the large distance between the midwoofers and the cone resonances of the midwoofer above 5 kHz, a low, steep crossover point is preferred. The schematic below shows the topology for a cauer-elliptic filter two way crossover, and the component values for these drivers developed from the measured data. The crossover is designed to provide baffle step compensation and an acoustical 8th order Linkwitz-Riley transfer function for the first 48 dB of attenuation. The crossover frequency is nominally 1200 Hz.

    These are the release candidate component values being ordered for testing; I spent some time and effort to try to have standard values so that unwinding coils, for example, wouldn't be necessary. The tweeter series caps will have to be made up from paralleled values; the values shown should be used with tolerances of a few percent, no more than 5% deviation.

    If I did my work well, the final actual values "should" be pretty much as shown- this worked out pretty well with my last project, the Arvo Part. I really only expect that there might be some change in the tweeter LPAD resistances- I doubt any other component changes will occur. But who knows?

    Note that rather than optimize primarily for on axis flat amplitude, I optimized the design more for total power response, especially off axis to 15 to 30 degrees. This results in some slight compromises in the on axis performance, but I believe that for the special case of a center channel speaker, this is a better choice, unless there's only one viewer/listener sitting dead on axis. In MOST home situtations, this won't be the case.
     

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