Need help designing small bookshelf speaks with WinISD

Discussion in 'Home Theater Projects' started by Shawn Shultzaberger, Nov 11, 2003.

  1. Shawn Shultzaberger

    Shawn Shultzaberger Supporting Actor

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    I just recently set up a small HT system in my bedroom but am using some cheap Bose speakers (2" or 3" paper cone with plastic wedge shaped enclosure). The enclosures are rattling at below moderate volume levels and is quite distracting. The Bose speakers run thru the passive crossover (about 80Hz I think) in my small 8" Klipsch sub.

    So to give me something to do I was thinking of creating some small bookshelf speakers to sit next to my TV in the armoire. I'd like to keep the cost of all drivers and tweeters below $100.00 (and thats either for 6 units or 4 units). The space I have to work with is 5"w x 20"t x 15"d. Since the width is 5" I was looking for 4" midbass drivers (1 or 2 of these) and a warm sounding tweeter. I'm still not sure whether I want two 4" drivers per side or one (MTM or MT). I want them to be as rich and full sounding as possible should I not have the sub turned on.

    I checked out Parts Express and found: Tang Band W4-992S 4" woofers. They say they provide excellent bass in a small package.

    Parameters are:

    Power Handling: 50 watts RMS/100 watts max / *VCdia: 1" / *Znom: 8 ohms / *Re: 7.0 ohms / *Frequency range: 55-2,500 Hz / *Fs: 55 Hz / *SPL: 86 dB 1W/1m / *Vas: .20 cu.ft. / *Qms: 2.93 / *Qes: .40 / *Qts: .35 / *Xmax 3 mm / *Dimensions: A: 4-9/16", B: 3-3/4", C: 3"


    Using WinISD .50a6, with the above parameters and a few more, 1 driver per box, in a vented enclosure I get the following:

    Enclosure Volume = .128 cu.ft.
    Port = 1
    Tuning Freq. = 63.23Hz
    Port Diameter = 4.02 in.
    Port Length = 63.62 in.

    And I am -3Db at 64.0 Hz. What am I doing wrong? If I change port Diameter to 1" I get a port length of 3.39" which seems fine. The enclosure volume seems awful small for a vented enclosure (.128). If I up the box volume to .20 I get a bump in db's at 74Hz and then I'm -3db at 56.96Hz.

    How in the world do you design these things??? I haven't even gotten to tweeters and crossover's yet. ACK!![​IMG]
     
  2. Shawn Shultzaberger

    Shawn Shultzaberger Supporting Actor

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    Oh, I forgot to mention that currently I am only using 2 speakers. If the DIY's turn out nice then I'll build the rest for a full HT bedroom system.

    I've been looking into these 4" drivers:

    Tang Band
    Audax
    Vifa
    Hi-Vi

    Or maybe:
    Adire AV3
     
  3. Mark gas

    Mark gas Second Unit

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  4. Shawn Shultzaberger

    Shawn Shultzaberger Supporting Actor

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    Thanks for the link Mark. But most of the kits I am finding that use 4" drivers are just to wide for me. I might be able to eek out a width of 5 1/4" per side. Using a solid .5" thick MDF or maybe Birch should be OK for this application.

    I've decided to go with the Tang Band W4-992S. This little driver in a vented box seems to be the way to go.

    Box volume = .128 cu.ft.
    Tuning Freq. = 59Hz
    Vent dia. = 1"
    Vent length = 4"

    This gives me a pretty flat Transfer Function up to 100Hz where it starts to gradually roll off. At 54Hz I'm -6db. I dont' think that's to bad.

    Am I doing this right??[​IMG] :b
     

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