That would depend on how it's implemented 🙂.
For this particular example of a 1000 cm^2 vent that's 75 cm long, I replaced it with a "venturi" vent that starts at 1000 cm^2, decreases to 600 cm^2 and expands back to 2000 cm^2 over the same length.
From the sim, Fb remains the same as the straight vent, and there are some minor changes in the FR above 200 Hz.
Attachments
OK, but it hasn't worked out that way for me, though in retrospect mine had much more taper with 10:1 being the 'sweet spot'.
That said, if it remains the same, how much lower is the vent mach?
WRT driver positioning in a fold, for subs it shouldn't be an issue due not normally needing more than ~2 octaves and since max gain is with the driver, vent at the extreme ends, easy to fold.
GM
That said, if it remains the same, how much lower is the vent mach?
WRT driver positioning in a fold, for subs it shouldn't be an issue due not normally needing more than ~2 octaves and since max gain is with the driver, vent at the extreme ends, easy to fold.
GM
Right, tapered pipes have a dip at the 3rd harmonic, which is ~2 octaves. That's really low for 50V; how much stuffing?
GM
GM
Hmm, my TQWT is 100% loosely stuffed and still peaks at 10+ m/s, but just noticed yours is tuned much higher, so never mind. Still a bit surprised it would be cut in half with such a modest flare though. I don't recall having any luck reducing WFO carb intake 'honk' until the scoop flare got pretty extreme with simple parabolic horns, so wound up with wide/flat hypex scoops.
GM
GM
Any chance a 10:1 taper with offset driver would work in the 8 cu ft that JBL spec'd for the BR?
For my hifi usage, not using all of the driver's capabilities, like 25 Hz low end and decent mid-bass, they say, seems wasteful. Heavily stuffed is usually my preference though. These drivers are surplus bits from a prosound buddy who has moved on to Labhorns. They have been reconed more than once so may not have the same specs as the original; will have to be measured before sawdust.
Ummm, did somebody forget to ask some key questions?
For example, with all the fuss about low end, just how high is the intended band?
A lot of TL construction (esp commercial units) is based on the lower-range driver handling music into the mid-range. Meshes with the benefits of using a small woofer drivers that naturally handle mid-range signals. Makes a lot of good sense given the natural shape of TL enclosures and the fact that it does makes a lot of acoustic sense. These systems tend to be two-way, again for the same reasons. And I am puzzled that TLs tend not to be identified as subs as often as I'd expect (and my own interest just now).
But, with that 18-inch hero, I wonder if you have a good mid-range concept and don't plan on going too high?
Turns out, the design notions look somewhat different when you are aiming for great bottom and don't care much about combatting those horrible mid-range irregularities. For example, the "one-third length gap" at the start of the pipe or padding or turns or taper or....
Is it an instance of amateurs like us seeing the trees but not the forest? Perhaps others who know much more about TLs than I do could comment.
B.
For example, with all the fuss about low end, just how high is the intended band?
A lot of TL construction (esp commercial units) is based on the lower-range driver handling music into the mid-range. Meshes with the benefits of using a small woofer drivers that naturally handle mid-range signals. Makes a lot of good sense given the natural shape of TL enclosures and the fact that it does makes a lot of acoustic sense. These systems tend to be two-way, again for the same reasons. And I am puzzled that TLs tend not to be identified as subs as often as I'd expect (and my own interest just now).
But, with that 18-inch hero, I wonder if you have a good mid-range concept and don't plan on going too high?
Turns out, the design notions look somewhat different when you are aiming for great bottom and don't care much about combatting those horrible mid-range irregularities. For example, the "one-third length gap" at the start of the pipe or padding or turns or taper or....
Is it an instance of amateurs like us seeing the trees but not the forest? Perhaps others who know much more about TLs than I do could comment.
B.
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One clue is where the thread is situated, subwoofers?
However if this was part of a full range system, bass/mid and treble would not be skimped, with high end units from ScanSpeak, Volt, Seas etc in the mix
Yes you are right, it was shamefully inadequate of me not to have the psychic powers to know you meant 160 Hz. Or 60 Hz? Or 120 Hz?
But back to my question. Would a TL design be better when targeted for a sub-woofer rather than usual bass and mid-range band.... with the examples of proband parameters I listed before?*
For sure, the lower-middle-range bumps in the FR would not need to be controlled if a low and sharp-slope Xover was planned.
B.
*Brian - even if OP couldn't care less, me and others might be interested in your viewpoint
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With a big driver like this probably a subwoofer.
I am guessing this would need careful modelling to avoid ripple in the upper response.
If it was to be part of a full range loudspeaker then the bass section would have to be driven actively from below 200Hz or so
DM 🙂
Depends on who you ask. 😉 If ~two octaves is all you want, then a TL need only be damped just enough to keep from sounding hollow, so quite efficient. For wide BW 'subs', MLTLs are the way to go IME.
GM
Thanks. That's sort of what I was wondering about. Typically two 8/aves is in the sub ballpark.
Then no taper, large Sd/Vas duct area, large vent, definitely no "one-third" wasted length...? Getting real big.
When you say "hollow", next question would be what frequency(s) because that would define the kind of absorbent to install. Would it also be right you would want to avoid a wide but skinny cross-section in order to drive the "hollow" freq up or do you mean acoustic-length partials?
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Brian, may I ask; what excel sheet are you using to map out the TL?
Regards, Raoul
18-inch, facing down, lots of pillow stuffing in the tube, might make a great labyrinth.
https://www.diyaudio.com/forums/subwoofers/322418-17-foot-pipe-sub-12-230-hz-5db.html
Like its cousin, the bass reflex concept, a TL needs to be a close match of driver and box. Sim is a quick-and,-sadly,-dirty estimate. Easy to re-tune a port but hard to change a length. A labyrinth, like a sealed box, works for all sizes.
B.
https://www.diyaudio.com/forums/subwoofers/322418-17-foot-pipe-sub-12-230-hz-5db.html
Like its cousin, the bass reflex concept, a TL needs to be a close match of driver and box. Sim is a quick-and,-sadly,-dirty estimate. Easy to re-tune a port but hard to change a length. A labyrinth, like a sealed box, works for all sizes.
B.