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T line \ bass reflex enclosure suggestions
T line \ bass reflex enclosure suggestions
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Old 13th July 2019, 12:13 AM   #11
GM is offline GM  United States
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Originally Posted by 3rutu5 View Post
What would this be? I thought it was a TL.
Technically ducted port since they have well defined low pass filter chambers and constant area 'vent', so can be designed using a basic reflex calculator such as is one of many types of alignments in Hornresp.

If it was inverse tapered from the top to the bottom, then it would be a TQWT.

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Old 13th July 2019, 03:10 AM   #12
3rutu5 is offline 3rutu5  Australia
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thats a bit of information to digest. I wasnt sure if going any of the horns and TL's would result in a smaller enclosure than a vented for a 3.5in FR driver, but cant honestly see how it would if you are needing quite the length.

I'll give it a good read later today when the kids are asleep and do a concept or two to see if i understand.
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Old 15th July 2019, 12:46 PM   #13
Squeak is offline Squeak  Denmark
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Originally Posted by 3rutu5 View Post
Oh ok, makes sense.

What would this be? I thought it was a TL.

On the assumption that it is,would I need to size the first enclosure? Ps this was called a transmission line for a subwoofer and I have just scribbled on it, so please pardon the mess
The difference in path length, was possibly to not have two ports with interfering output next to each other.
Good idea, bad implementation, and setup is wrong in scope and intent to care about stuff like that.
With such small initial chambers, bass frequencies output, is still going to be directional. You'd want the port out the sides ideally.

For a boombox type setup you'll want regular BR ports, or other restricted tuned vented cabs (aperiodic etc). Or possibly even closed with the right size cab and driver type.
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Old 17th July 2019, 09:40 PM   #14
krakatoa is offline krakatoa  Romania
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The key word here - at least that's how I see this thread - is "boombox" and that means the rules of the game are different, things like driver sensitivity, driver weight, enclosure weight, enclosure size to low frequency extension ratio are key factors... not to be confused with the way things are done when designing a box to sit/play in a room.
The TL in the attached image in the first post is most likely this one: YouTube - which is neither small nor really that full range, more like a bass heavy tuning, subwoofer type thing... and awfully heavy. Let's go back to the "boombox" rule - the lightest smallest enclosure that can deliver bass should be a closed box with a large passive radiator (and passive radiators can be very light! no need for a steel basket)... which is what the standard commercial portable audio proposes... plus a neodymium driver, smaller magnet means less weight, stronger (neodymium) magnet means more SPL.
Of course this is just engineering for the more likely desired qualities... you can always make is out of pure dinosaur fossil just to make it really really unique.
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Old 17th July 2019, 09:51 PM   #15
Scottmoose is offline Scottmoose  United Kingdom
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Actually, I take one look at the image in the first post & 'boom' is about the last thing I would anticipate. Unless the scale is misleading, that's in effect an extremely long, high aspect ratio port (in this sense it wouldn't make much difference whether the chamber was eliminated; the details will change but not the general trend), which will almost certainly result in a low tuning, but very little gain, viz. a highly [over]damped alignment.
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Old 17th July 2019, 11:07 PM   #16
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T line \ bass reflex enclosure suggestions
Quote:
the lightest smallest enclosure that can deliver bass should be a closed box with a large passive radiator
If there is a pasive rasiator the box is vented not sealed.

And there are many other factors at play.

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Old 18th July 2019, 08:26 AM   #17
krakatoa is offline krakatoa  Romania
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Originally Posted by planet10 View Post
If there is a pasive rasiator the box is vented not sealed.

And there are many other factors at play.

dave
I'm not an authority in passive radiator designs but to my knowledge the air inside a passive radiator enclosure is separated (not communicating with the outside) from the outside... my thinking was that it's a lighter version of the sealed enclosure because one of the walls (a portion) is replaced with a passive radiator which is much lighter that the wall it replaces and gives better bass... and my comment was about size/low freq reproduction to weight/size ratio. Also sound quality is secondary to sound quantity in such cases (portable audio).
By the way, if "And there are many other factors at play" you might want to explain you vision of the portable box design philosophy.
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Old 18th July 2019, 09:20 AM   #18
3rutu5 is offline 3rutu5  Australia
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ok, ok, ok, look i always get caught up thinking that maybe i can grab a router and carve me out a maze/labrynth arrangement, or build a proper t line one that actually lets me hit those notes around the mid 50's out of my 3.5inch drivers.

But from what i've been reading outside of this forum, the time you calculate your length required, take into acount wood thickness and the intial chamber, a transmission line may not be as small as i thought. Using an online calculator it would appear that the travel length needs to be around 700mm+ long and i have no idea yet what the inital chamber has to be to cater for 2 drivers.

I'm not too concerned about weight to be honest, just wanted something smaller than my first boombox which ended up being about 450-500mm long. It sounds pretty good for what it is. What got me going with a bit of wood working was the T-Line i just copied from this site, based on the same driver and measurements, it did a nice job, (lacked a little in the lower end), until i lined it up against a vented 0.18cuft enclosure which blew it away (tuned to a FS of 58hz). All to date has used the TEBM65's which i actually like.

On another note, i've researched isobaric, which most information to date only seems to relate to sub woofers and cars, Linkwitz circuits, which look to be only sealed boxes, stuffing the box, which seems to reduce the Q, smaller vented boxes, mazes, bass reflex ports, T lines and honestly completely confused. Most Youtube out there is geared towards subs, where if there is a TLine or maze, it is japanese and listening to classical music, which isnt what i would be listening to.

Just really want to make something smaller (at least 1/2 to 2/3rds the size of the bigger brother), which was tuned to around 60hz, that sounds thumpy when required, not caring if it weighs a kilo.
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Last edited by 3rutu5; 18th July 2019 at 09:28 AM.
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Old 18th July 2019, 09:31 AM   #19
3rutu5 is offline 3rutu5  Australia
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about 6 months ago i got caught up in this video, purely because i thought it would be fun to do the woodworking.

YouTube

I did briefly look at the Passive radiator as well, just got put off with the WinISD modelling, seemed to go wonky and suggest i needed 3 or 4 to 1 in the PR's to Driver.
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Old 18th July 2019, 09:52 AM   #20
Scottmoose is offline Scottmoose  United Kingdom
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If a goal is to make the smallest possible enclosure, then a TL / QW variation is not the way to go: for a given tuning / alignment they are physically larger than conventional vented boxes. Also, as noted, if you want a one-note 'thump' / 'boom' then a TL is usually also the reverse of what you need, since most such alignments are more highly damped. To a point you can do it, but it's making life more complicated than it actually needs to be.

Note that lambda / 4 only 'works' for untapered lines (and ignores end-correction also); line acoustical length (tuning frequency) is a function of axial length and taper, not length alone.
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Last edited by Scottmoose; 18th July 2019 at 09:55 AM.
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