Building Sphere - First Time Builder Needs Help

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JsoundEngineerUK

Member
2013-02-08 2:47 pm
  • #1
    HAY THERE:D

    First intro - My name is jay, i wish to build a speaker and hope with fellow users i will be able to do so:). i have done some research (nothing to heavy) i have been reading a few good books i have seen people speak about such as:

    Audio power amplifier design handbook by Douglas self
    The Design of Active crossovers by Douglas Self
    The Loudspeaker design cookbook
    loudspeakers for music and production.

    I am wanting to build sphere shaped speaker enclosures which i know has a lot of debate surrounding them but that's what i want lol :) I do intend to use them as studio monitors and would like to make them compete with the SE Munro EGG, yes ambituios i know, this is for my dissatation so it has to be amazing.

    I have these Drive units in mind (speakers/cones - whatever you wish to call them)

    Monacor - DT-25N (pdf attached with specs)
    Monacor - SPH130AL (pdf attached with specs)
    This is down to frequency response and the looks it will give, i wanted to use a white woofer to get that NS10 look, and the DT-25 tweeter to mimic SE EGG.

    With my enclosure for the woofer, i worked out that a 4inch needs approx 0.25 to 0.39 cubic feet of volume within the enclosure. Because the frequency response of the SPH130AL is so low at the low end i am hoping that by using a small enclosure with a port will just boost the bottom end??? i hope i am right on that one. the volume i actually require using 0.25cubic feet as a reference this comes to 432cubic inches, giving me a radius of 4.69 ices for the sphere enclosure. I plan on using GRP to Make the enclosure with support struts and a metal mesh. Like if you take a football and but the struts around that then apply the mesh round that struts then by using the paste on top if the mesh, the allowing it to dry, then by deflating the ball/object inside the casing and pulling it out where the driver unit will sit then using the paste on the inside. then when all is dry and good using a bit of elbow grease and wet and dry sandpaper sand it down to a smooth finish. I know Spheres also generate internal reflections so when i have the electronics done (hopefully with your help) i will find out what sound is making it honk or tweet and treat it accordingly.


    Now with the enclouser delt with its the electronic designs i am confused and bewildered by such as a transformer,power amplifier, and crossover.

    Now i wish to make it an active crossover utilizing a 6th order linkwitz riley design. I went over to 2-Way Crossover Designer / Calculator
    and this is what i got

    6th Order Linkwitz-Riley

    2000 Hertz

    8 Ohm Tweeter / 8 Ohm Woofer [IMGDEAD]http://www.diyaudioandvideo.com/Calculator/XOver/circuit6.gif[/IMGDEAD] Parts List
    Capacitors
    C1 = 5.53 uF
    C2 = 6.76 uF
    C3 = 13.68 uF
    C4 = 18.42 uF
    C5 = 11.14 uF
    C6 = 2.49 uF
    Inductors
    L1 = 0.34 mH
    L2 = 0.57 mH
    L3 = 2.55 mH
    L4 = 1.15 mH
    L5 = 0.94 mH
    L6 = 0.46 mH


    So that's telling me the right stuff, but i would also like to make this as flat as possible. so I am guessing i would also need to place a bandpass filter over the top of the crossover which is where I need help. Because i could build that simple enough, but its the Amplifier, turning this into an active crossover, adding a low filter boost with volume nob and then building the transformer so i can plug in my active crossover to a mains 240v, I don't plan on having the electronic boards in with sphere but a stand alone unit. connected like a normal studio monitor balanced jack plug or xlr I may use a newer connection system.

    Please Can some one help me design this, I know its a lot to ask but a few bits are lost on me with the books and dose not say use this to get this result lol.

    this as i said is my dissertation work and wish for it to over top the markers expectations and to challenge the SE EGG

    btw i am still reading the books ;) in hope i can have my light bulb moment but still think a little guidance is needed.:p

    Thank you for reading I hope you will and can help. J
     

    Attachments

    • dt-25n(1).pdf
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    • sph-130al.pdf
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    AllenB

    AllenB

    Moderator
    Paid Member
    2008-10-18 11:31 am
  • #2
    If you want these to be monitors and expect them to be competitive, you may need to take several measurements of them in their final enclosure and process this data appropriately. Unfortunately, simply choosing a sixth order crossover will not guarantee exceptional sound, nor does it make a lot of sense without the data...and going active won't get around this.
     
    Mark.Clappers

    Mark.Clappers

    Member
    2010-01-18 2:34 pm
    The Netherlands, near the German border
  • #3
    Try simming the response of your design with programs like this:

    LinearTeam
    Boxsim - Homepage
    Home of the Edge
    Leonard Audio - Coming Soon

    I would seriously consider DSP for a project like this, Hypex DLCP & MiniDSP come to mind

    Hypex Electronics BV - Home
    Home | miniDSP

    And when you build your design measure it with a program like this:

    ARTA Home

    The reason I really advice a DSP for a system like this is the freedom it gives you to tweak the response without building a lot of X-overs, passive or active..

    And if you have to build your own X-over for your dissertation the DSP can help you figure out what you need to build! Just stick with IIR filters in that case.

    The filter you designed is passive btw ;)

    Additional link: http://www.linkwitzlab.com/filters.htm
     
    Last edited:
    B

    Boscoe

    Member
    2010-02-07 6:52 pm
    England
  • #5
    I find it hard to believe you write like this and completing university. Can I ask what course you are doing? Music tech? Something like that?

    Designing a two way speaker is easy as long as you know a few things. If your going to go to the trouble of making a sphere (which IMHO is pointless from an audio quality perspective) you should use some better drivers. Look up Falcon Acoustics and have a look at the SB Acoustics range of drivers, they are very well priced and are some of the best only the likes of Scan speak and Seas are better.

    Look up Linkwitz Riley active crossovers and 6th order is overkill, use 4th order.
     
    flg

    flg

    Member
    2005-07-06 1:13 am
    North East
  • #6
    B

    bjorno

    R.I.P.
    2005-03-17 9:36 am
    Jacobsmountain
  • #9
    Hi,

    Studio Monitors? No Way, PC speakers at a listening distance ~<= 1m is Ok.
    IMO: The Visaton Driver xmax= 2.3 mm is the mayor limiting factor.

    Even when (if) ported it would be a low performer...

    b:)


    Ps: Supporting calculations : Posting a quickly made Picture:
     

    Attachments

    • Monacor - SPH130AL_Sphere.jpg
      Monacor - SPH130AL_Sphere.jpg
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    C

    Charles Darwin

    Member
    2009-11-18 7:03 pm
    Birmingham, UK
  • #10
    What would the insertion loss of a 6th order xover be?

    Just looking at the low pass series inductors at 200Hz the 1.15mH inductor has an impedance of 1.45 Ohm, the 0.94mH 1.18 Ohm and the 0.46mH 0.6 Ohm (all NOT counting the inductors DCR which would have to be added).
    Do they just add up being in series to about 3 Ohm at 200Hz?

    The series capacitors in the high pass have impedances of 2.8 Ohm, 2.4 Ohm and 1.16 Ohm respectively at 10 000Hz.
    Do they simply add up 6.36 Ohm?

    I used these impedance calculators: Pronine Electronics Design - Capacitor Impedance Calculator and
    Pronine Electronics Design - Inductor Impedance Calculator
     
    J

    JsoundEngineerUK

    Member
    2013-02-08 2:47 pm
  • #11
    @Mark.Clappers Thank you so much for the reply, unfortunately the program i have installed WinISD says something about my parameters and that i can not save it????? and it will not link to the help server? any help with this would be amazing. as for DSP i would really like one but the cost is a bit to much even though they are amazing from what i have read.
    @AllenB I do understand that the crossover is passive in the picture that's why i asked how do i make it active? i know the crossover its self will not make it sound amazing this is why i am here asking for help.
    @tvrgeek I know its uncommon that's ONE of the reasons why i chose it. there are other reasons.
    @flg , Thank you I came across one of them before whilst deciding on shape of enclosure, I will give the other two a look.
    @bjorno - Thank you I will look at picture. and maybe look at different drivers

    NOW TO MY FAV POST - Boscoe
    I find it hard to belive that someone would conduct them selves on a website in the manner in which you just did to me, how rude do you wanna conduct an introduction to yourself ?
    and this is a forum not my paper. also not that its any of your business but i have certain learning difficulty's but its not like any of the greatest inventors or painters did not have learning disability's, some suffering with o.c.d. I will however look at the speakers you suggested but as for my personal life your opinion matters none.

    @prairieboy Thank you, your a gentalman and a scholor ;-)
     
    Pano

    Pano

    Administrator
    Paid Member
    2004-10-07 6:05 am
    Panama
  • #15
    :cop: JsoundEngineerUK - you are new here and should review the rules. Personal remarks are not welcome by anyone. You appear to have bitten off more than you can chew with this project, you can expect a bit criticism from more seasoned forum members.

    Further personal remarks (by anyone) will be removed.
     
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