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-   -   Sub Transmission Line (http://www.hardwarecanucks.com/forum/audio/43344-sub-transmission-line.html)

Coach May 15, 2011 11:54 PM

Sub Transmission Line
I hope my thread is not too OT but I thought I would throw my question out there and see if something sticks.

My plan is to build a Transmission Line for a Type R 12 Alpine sub for HT use. I want to use a TL bc I can tune it by length to the "exact" resonant frequency of the sub which happens to be 26hz. That means I will need TL in the length of just over 10.5 feet. AFAIK the math goes: 1100(ft per sec)/26hz(free air resonance of the driver)=42.307ft(size of the wavelength at the fq) I plan the TL to be 1/4 the wavelength and that is how I arrive at ~10.5 feet. I plan on using 12" Sono-tube for the construction of the TL and then fill it with poly-fill as need to adjust the sharpness of the sub response. For an amp I want to use a Alpine MRV-T707 bridge to mono @ 4ohms. I am hoping for an output of ~400watts RMS from the amp but I have not actually checked to see what it can deliver in the real world.

The idea is that my HT needs a lot of help below 40hz and this home brew TL is supposed to be a solution. I have considered SVS subs or a Dayton Sub kit but seeing as I have most of the parts to build a TL I thought it was worth a shot

I would appreciate any questions or suggestions or comments. How do you think this will turn out?

For a visual of what I am talking about here is a pic of two Transmission Lines. I will be making just one. TBH my TL will have to lie on the floor bc I have 8ft ceilings.

Here you can see that the interface to the sub is rather simple to build and should not take long to make.

(Pics are from "The Legend of EL PIPE-O")

Perineum May 16, 2011 07:08 AM

Very interesting designs. Never seen them before. Now I've spent the morning reading up on them.... :thumb:

lowfat May 16, 2011 08:18 AM

It has been a long time since I've looked in to transmission line enclosures, but those don't look right to me. Although I am just guessing here since I can't see the interior.

Coach May 16, 2011 10:43 AM

What should they look like? those sono tubes have "stuff to taste" in them and that is it AFAIK.

lowfat May 16, 2011 10:49 AM

This is a pic of one from the internet.

Coach May 16, 2011 03:46 PM

Ya that is also a TL but afaik it will be inferior to what I plan on building.

HalifaxPete May 16, 2011 06:47 PM

Could you make the enclosure more compact by building an upside down squared U from the Sonotube?

When I considered building a set of speakers with sonotube, I thought about making the top end cap semi-spherical.

In the OP's picture, I wonder how the speaker basket can support all of the weight of the tube, stuffing, and end caps?
Would the sound be affected by that weight?

Coach May 17, 2011 07:00 AM

AFAIK any corners in a TL compromise the effect but not so much that the TL is un useful. Also there is NO endcap. the Sub is at one end and that is all.

Coach May 21, 2011 12:59 PM

I finished my TL and I will post some pics soon.

Coach May 22, 2011 01:04 PM

Here are some pics:




Wow! this sub is doing what I have always wanted. It extends LOW. For you that have subs that extend low I must say give Tron: Legacy a go! trust me! It would be nice to compare my home brew to a boutique sub like SVS or Fathom. It is not that I think mine is better no, just that I would like to know what else I am missing. As is I am finding that my movie experience has increased dramatically. 60% of movie enjoyment is audio and 40% is for the rest IMHO. All in all I achieve the goal I set out to attain, I believe that I now have filled in that all important 20-40 hz range with some authority IMHO.

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