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Old 8th December 2009, 02:57 PM   #1
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Default fine tuning of tapered TL...can i do this???

my TL design i have been working on is nearly done. Before i build i want to make sure i can tinker with tuning if necessary. I know you can do this with varying stuffing amount and location, but i would also like to know if i am correct in thinking that if i reduce the vent area, i am effectivley lengthening the effective length and lowering the tuning and vice versa.

IE if i drill for eg. 3 1" diameter holes for the vent and find that the tuning is slightly low, i could drill an additional hole to increase the total vent area slightly, thus increasing tuning frequency, by shortening the effective length seen by the LS, as the taper ratio will also be slightly effected, and hence the actual length required to maintain the same tuning would thus increase.

I could EVEN drill say 4 or 5 holes to make up vent area with a +/-1inch³ variation, and open or close them as necessary to tune optimally and then fix them permanently when im satified with the result.

What do you think TL fraternity?

Is that a viable idea?


I think it will work but i have yet to find anyone who has tried it to confirm my suspicions.
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Old 8th December 2009, 04:18 PM   #2
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no-one?

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Old 8th December 2009, 04:42 PM   #3
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You didn't say but I'm assuming your TL is not tapered? It has a constant cross-sectional area along the whole line's length? In any event what you propose will have the effects you've stated but it's kinda hit and miss, if you ask me. Better would be to model the line using an appropriate set of driver T/S values which will allow you to accurately determine the proper density and length of stuffing as well as the proper terminus area, leaving nothing to guess at after the fact.
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no-one?

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Old 8th December 2009, 04:44 PM   #4
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It's not rocket science, go for it!

It's not that unusual. Some guys will stuff a foam ball in their vented sub's port when listening to music, and pull it out for home theatre.
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Old 8th December 2009, 04:49 PM   #5
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Originally Posted by leadbelly View Post
It's not rocket science, go for it!

It's not that unusual. Some guys will stuff a foam ball in their vented sub's port when listening to music, and pull it out for home theatre.
figured it wsnt rocket science....but thanks i will give it a go to fine tune it, as unlike many i dont RELY on calcs alone to produce a design...much tuning is needed by EAR IMHO.

so Thanks

and thanks also to the other guy but i HAve already modelled it......eg maybe i want to stuff optimally and then tune higher to return to a flatter rolloff?
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Old 8th December 2009, 04:54 PM   #6
pkitt is offline pkitt  United States
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Well, okay, whatever floats your boat, but if you have modeled the design correctly with optimal stuffing and terminus area, why do you think there will be a need to change that tuning? Are you trying to correct for room effects?
Paul

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figured it wsnt rocket science....but thanks i will give it a go to fine tune it, as unlike many i dont RELY on calcs alone to produce a design...much tuning is needed by EAR IMHO.

so Thanks

and thanks also to the other guy but i HAve already modelled it......eg maybe i want to stuff optimally and then tune higher to return to a flatter rolloff?
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Old 8th December 2009, 05:05 PM   #7
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NOT entirely.
basically i have 2 drivers and after much run in time their t/s params are a little less identical than i wouldve liked...so the idea is to tune each box relative to the driver it is going to be used with, WITHOUT changing stuffing density to achieve the same effect. In this way i hope the suppression of pipe harmonics will remain equal due to the use of equal stuffing densities/amounts.
also, my design will maybe use up to 8" of variable density absorbent fixed to the 'walls' of the TL, which may (will have to see) help to damp some of the upper pipe harmonics, reducing the need for AS much polyfill, and hopefully increasing vent sub Fs output, without comprimising FR smoothness greatly. as before i will have to see if that pans out!

I have measured and calc'd the ts params and im satisfied with the accuracy, but the variation is enough that although i have averaged the results in order to calc TL taper, length, open area etc; I would still like some additional adjustment to be available, for room reinforcement, (of which i have little to medium amounts of) and driver variation. especially variation with age.

my home is built with plasterboard/drywall, 2 layers with green goo between, and i have been lead to believe this CAN soak up an awful lot of LF, hence tuning options would be handy, if nt essential.

Last edited by mondogenerator; 8th December 2009 at 05:09 PM.
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