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Transmission line enclosure

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  • Transmission line enclosure

    Anyone know of a suitable bookshelf-sized transmission line enclosure for Peerless 850122 6-1/2" woofers? I've seen 1/4 wave floor standers but I'm looking for a bookshelf.
    * Power handling: 150 watts RMS * Voice coil diameter: 1-1/4" * Voice coil inductance: 1.3 mH * Nominal Impedance: 8 ohms * DC resistance: 6.1 ohms * Frequency response: 38-5,000 Hz * Fs: 38 Hz * SPL: 87 dB 2.83V/1m * Vas: .98 cu. ft. * Qms: 2.22 * Qes: .53 * Qts: .43 * Xmax: 5.5mm

  • #2
    A TL is a 1/4 wavelength device. 1/4 wavelength at 38Hz is 7.4 feet. That's why TLs are floorstanding, not bookshelf.
    www.billfitzmaurice.com
    www.billfitzmaurice.info/forum

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    • #3
      I don't know much about TL speakers, but I googled your woofer and found the "Peerless Pipes" a 2003 DIY design which looks like a transmission line: it's 43" high, 10" wide and 11" deep - so as Bill says above, it's a large cabinet. No idea how it sounds, or whether it's a good design for a TL anyway.

      Geoff

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      • #4
        Maybe you just need a really really big bookshelf?
        Francis

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        • #5
          Thanks for the replies. I was aware of the "Peerless Pipes" so I thought I could just fold up the line into a more manageable size cabinet for my purposes.

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          • #6
            1. Look at how PMC bookshelf speakers are designed - they are quasi TL / aperiodic . Here is an analysis / diy thread https://www.diyaudio.com/forums/mult...30a-dc28f.html

            2. Consider a tapered TL (this will allow you to builder a smaller enclosure)

            3. Consider a higher target frequency for the 1/4 W frequency (maybe 50 - 60 Hz). TL's roll off more gradually than bass reflex designs and complement room gain.


            Hope that helps

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            • #7
              FWIW, I did a quicky model of a single-fold TL with a taper ratio of 30:1 that had a line length of just under 37" that could be built into an enclosure with internal dimensions of 8"W x 18"H x 16.25"D. I didn't spend any time optimizing it but its f3 was in the mid-30s I think and the overall response was smooth. The terminus, however would be on the back panel, so the box couldn't be literally shoved up against a wall or the back of a bookcase.
              Paul

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              • #8
                Paul, thank you for responding. I was hoping to get some input from a transmission line specialist! I intended to use these cabinets on stands, not on a desk top, so a rear terminus wouldn't be a problem at all. Any way I could get a diagram?

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                • #9
                  I want to spend more time on the modeling as I'm considering an alternate possibility. I'll let you know what I come up with.
                  Paul

                  Originally posted by B King View Post
                  Paul, thank you for responding. I was hoping to get some input from a transmission line specialist! I intended to use these cabinets on stands, not on a desk top, so a rear terminus wouldn't be a problem at all. Any way I could get a diagram?

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                  • #10
                    Paul, anxiously waiting for your reply. Got the urge to make some sawdust!

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                    • #11
                      Do you have any specific requirements regarding cabinet size and/or shape as well as hoped-for f3?
                      Paul

                      Originally posted by B King View Post
                      Paul, anxiously waiting for your reply. Got the urge to make some sawdust!

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                      • #12
                        I was thinking something along the lines of an 8" or 9" wide and 18-20" tall, front baffle. Depth isn't as critical. I will be using these on 24" stands and ideally I'd like to have the tweeter at 32"-36" from the floor.

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                        • #13
                          Those dimensions are definitely doable. I'll try to get you something by Saturday. I've been playing with a 2-fold, 3-segment ML-TL that looks very, very promising.
                          Paul

                          Originally posted by B King View Post
                          I was thinking something along the lines of an 8" or 9" wide and 18-20" tall, front baffle. Depth isn't as critical. I will be using these on 24" stands and ideally I'd like to have the tweeter at 32"-36" from the floor.

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                          • #14
                            Thanks Paul. Above and beyond the call. If this will work, I'll document the build of these bad boys. No big hurry as we are leaving on a trip Sunday and we'll be gone for a couple of weeks. As soon as we get back, I'll fire up the table saw.

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                            • #15
                              What are you using to model Paul?
                              Copy of Lou C's speaker pages: http://www.rob-elder.com/LouC/speakers.html

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