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Old 28th October 2013, 05:04 PM   #1
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Default Vent placement in a QWTL

Hi Forum,

In a quarter wave transmission line design, where is the best place to put the vent? On the front? On the back? Or perhaps on the side? I have searched around quite a bit and found lots of useful information concerning the length of the line etc, but never any information concerning the placement of the vent. Perhaps you guys can enlighten me?

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Old 28th October 2013, 05:34 PM   #2
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Depends on the design, your room, and what you're trying to achieve, since 'best' is unfortunately a floating point that varies with these.

For optimal loading over the widest possible BW, then it should be at the end, in the same way that the driver should be at the throat. Of course, whether you actually want maximum loading over the widest possible BW is another matter entirely. The effects can however be modelled, and this is the best way to proceed unless you want to engage in extensive prototyping.
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Old 28th October 2013, 05:46 PM   #3
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Quote:
Originally Posted by Scottmoose View Post
For optimal loading over the widest possible BW, then it should be at the end.......
.......and down-firing IME, though only if the vent is damped internally or at least is firing into a carpet or similar to damp down its harmonic BW from comb filtering with the driver's output, i.e. only audibly reproduces the BW around Fb[p].

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Old 28th October 2013, 06:11 PM   #4
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Good point.
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Old 28th October 2013, 09:10 PM   #5
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Thanks for your input, guys. Much appreciated. As I enjoy working with wood, and want to improve my skills, I think I will experiment for a while :-)
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Old 29th October 2013, 02:34 PM   #6
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You're welcome! That's the spirit! Nothing like experience to form your own opinions, preferences. We need more knowledgeable DIYers to add to a forum's 'mix', so hopefully this will be a long time hobby for you.

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Old 29th October 2013, 04:18 PM   #7
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+1. Go for it! Best way is always to try things out for yourself.
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Old 29th October 2013, 11:36 PM   #8
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From playing with MJK's models it seems the best location of the port is at the end of the line AND next to the driver. Meaning of course folding is needed.
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