TL sweetspots

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I've been designing a couple sets of TL's. One set is built and I'm in the process of tweaking it with stuffing, and I've started the carpentry on another set. I used the rule of matching 1/4 wave tuning frequency to the resonance of a driver in a sealed enclosure of the same volume as the TL.

To find a reasonable tuning frequency and line taper, I used Winisd sealed enclosure simulations to perform calculations. I started with fairly low box volumes, about 1/2 Vas. Then increased the volume gradually, linearly and the Fsc ofcourse decreased, quite rapidly at first. I noticed that the rate of decrease in Fsc values lessened as well, maybe logarithmically with respect to the increase in enclosure volume. At about 2x Vas, there was already very slight decrease in Fsc.

Could there be an ideal ratio of the Vas of a driver to TL volume, a sort of sweet spot?
 
Time for some reading:
Martin King's site: www.quarter-wave.com

Read his 'Anatomy of a Transmission Line' article, then his 'Classic TL alignment tables'. Afterward, you might wish to download his seminal MathCad worksheets.

This is not just another set of rules of thumb. They're not rules of thumb at all. Martin is the man who's comprehensively cracked the alleged mysteries of the TL. You want to design one? This is how you do it.

A word of warning. There is heavy math involved on this site. However, don't become discouraged if you can't cope with it all. The important thing to remember is that Martin's done it all for you. All you really need to do is select the appropriate values from the tables, though it's worth persevering with the theoretical side if you can. It's well worth it, because you will then have a thorough understanding of the principles, and it might even encourage you to download the worksheets.

Regards
Scott
 
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