As one adds damping and the box goes toward aperiodic, the impedance peaks start at a typical BR double hump and then they start disappearing. If you succeed in getting the impedance perfectly flat (likely not totally achievable) then (almost) all the back wave is absorbed, very little gets out the terminus. Q will drop (althou we ususally don’t much talk about Q in a box with a hole in it). Response will be simialr to sealed — althou i may heve data (not mine) that shows at least initial roll-off is slower. So one does not get the “same” as sealed.
This is particualrily useful in a midTL, it is most often not the goal with a typical TL where we are trying to use the quarter-wave resonance to gain some bass.
dave
Another observation on aperiodic vents. These try to acheive aperiodicity with a resistive element that is very thin — millimetres in some cases. If one uses the entire line as a source of the resistance, then one has a much longer resistive path to absorb the back enerfgy of the driver. Given that it typically takes at least a quarter-wavelength to kill a resonance, this makes a lot more sense.
It should be noted that Onley’s 1st acoustic labyrinth was as long as possible, not a quarter or half wave length. The idea was to absorb the entire rear wave.
http://p10hifi.net/planet10/TLS/downloads/Acoustic-Labyrinth-Olney.pdf
dave
I'm not scared of flat bass...the thin, accurate bass, that people aren't always accustomed to...is welcome in the sound engineering studio...I'm trying to create that for my 18h+....at this point I can't tell if a resistive vent, is one step closer or away from this....and maybe the large sized stuffed seal is the only option outside of a back-wave eating TL....
If I could I would model a Sealed transmission line. I know you have to tune by 1/2 WL but I just want to see what I can't make happen within the size I am aiming for.....I believe that impedance is much lower, from the experiments I tried on HornResp, to mimic a Sealed TL.....I think it lowers tuning as well...both desirable. But how does one model a seal TL properly? And the sealed configuration in HR does not seem much affected by dimensions if volume is unchanged.
Correct and at some high value, HR returns an error message, which presumably is when it becomes basically a solid mass.
An earlier thread: https://www.diyaudio.com/forums/sub...olyfill-stuffing-explanation.html#post4972578
Some testing: GlassWolf's Pages
That said, open my recommended 10:1 [ML]TQWT, then in the LW/power & 'filling', input segment 3 = 1000/100% and look at the other fields to see what it did.
Now you know all you need to know about the so called aperiodic vent that it's not since it didn't take out both impedance peaks.
Re TL Vs sealed, compare this to HR's 'IB' default to learn all you need to know about any trade-offs.
GM
You guys are so helpful!
So can we talk Decay? Is this being left out? Sealed is the one with the shortest decay....this also increases sound quality....so its like either; short decay....or short excursion....how do you pick one? Horn Resp does not calculate decay for enclosures with lining...There's no way for me to tell what type of decay any of my TL designs have and thats concerning....If thats how its going to be, I might as well error in safety and build the enclosure with the least decay....sealed.
So can we talk Decay? Is this being left out? Sealed is the one with the shortest decay....this also increases sound quality....so its like either; short decay....or short excursion....how do you pick one? Horn Resp does not calculate decay for enclosures with lining...There's no way for me to tell what type of decay any of my TL designs have and thats concerning....If thats how its going to be, I might as well error in safety and build the enclosure with the least decay....sealed.
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I know from Horn Resp that a TL can be designed that is much more dampened than a Sealed, its just that I cannot see a decay chart for said design.....Without a large amount of trial and error, theres no way to fully model a TL....that I know of....when I say model, I want to see all specs that matter, and decay, is just as important than any other spec. I can model a ~2000 cm2 CSA with a length of 20-25hz....stuff maybe the first 1/4 heavily and get impedance down to the 30's and maintain 7db boost in the sub bass region....You know the decay on this model is just like most Bass reflexes...yet the impedance is so low... Nothing in HornResp to guide the way......yet.
I also think that maybe a better way to use a TL or any vented design is just to tune them no different than a horn.....If you wanted to be stritch in your use of a CD+horn.....Horns tuning would be almost twice as low as intended spectrum keeping the passband away from ill behavior of resonance (high Decay/high group delay)
I also think that maybe a better way to use a TL or any vented design is just to tune them no different than a horn.....If you wanted to be stritch in your use of a CD+horn.....Horns tuning would be almost twice as low as intended spectrum keeping the passband away from ill behavior of resonance (high Decay/high group delay)
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Double click on [Fta] and a red [clo] pops up; works in Horn Wizard too, just [Show Baseline] won't let us switch back n' forth to compare both closed and open. 🙁
GM
With the update you can model a Sealed TL with Sealed plus stub....unless I'm mistaken..
Sealed TL, lower FC, lower impedance (dampening) also lose some output....no free lunch here either.
Sealed TL, lower FC, lower impedance (dampening) also lose some output....no free lunch here either.
Yes...You cannot model Decay for TL/vented enclosure [including dampening material]....unless I can trust what I see in REW when I export the IR....wait, you can't export the IR with dampening material in the equation...So I tried send the FR of the stuffed enclosures too Vituix and then turning the FR into a IR and then sending it to REW...but this way, REW won't calculate decay anyway sooo....
Lower effective Qt and any alignment will reduce decay, so want a really 'fast' speaker? Just use one with a very low effective Qts' in an IB, but the trade-off is it can't come close to accurately reproducing the signal since it will clip off the transient peaks, then start the next note before the first one can properly decay.
GM
Dunno, I'm using an older version.
Physics, it's the Law! 😉 TA Speaker Topics: Loudspeaker Design Tradeoffs
GM
Aaaaaaaaagh Gm you are backing me into a corner...thank you =) Outside of the fact....I can't see the modeled Decay of any vented enclosure using dampening material...
If I could convert the polyfil spec in horn resp to wool, that would give me a lot of encouragement to try a TL design =)
If I could convert the polyfil spec in horn resp to wool, that would give me a lot of encouragement to try a TL design =)
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Thats literally me putting the 18h+ in a large, sealed, stuffed, box GM...(right?)....Are you describing an enclosure with a Q lower than critical dampening? Or am I fine with a sealed box. I want a fast speaker, but I don't want to cut the transients off right? Is that the definition of critical dampening? How can it be cutting off transients if its sensitivity is at 0 transfer function....
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