Jump to content

Quarter Wave / T-Line tutorial-UPDATED


Recommended Posts

I still don't understand how all this works. I thought it was cone area = port area, port length tuned to fs of the sub. Apparently there's way more to it :shok:

Its just like designing a ported box with torres, WAY more to it than what torres is capable of.

Owner of BigAss Ports

VTLOGOnotext.jpg.667f65a91c14a3f8b00ad9ab5ecdb92f.jpg

 

 

 

 

Link to post
Share on other sites
  • 1 month later...

  • Replies 1.6k
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Popular Posts

UPDATED with new pics, different subs, sorry about the wait people Okay, some people will hate me for posting this, hopefully no one on the great world famous SMD forums  :^  But I see alot of peo

There is a bit of a complicated answer to this.  Subs have two limitations on how much power they can take, there is the mechanical limit of how far the cone/coil can travel before bad things happen,

Fun with t-lines... well, there's no sub I guess.. but yeah

Posted Images

on youtube a poster named HexiBase built a few t-lines. the one that I'm interested in if anyone seen it is the one he built for his personal vehicle. he stuffed 3 12" SA-12's into what he called a t-line in the back hatch of a Suzuki Grand Vitara or an XL7 not sure which. I've seen the size of the OP build for 2 12's in the back of what looks like a Tahoe or a Suburban, so I'm not sure how this guy HexiBase did 3 in the hatch of a small SUV/Crossover

Does anyone know what programs the guy (HexiBase) was using to build his boxes? and how he made a "small" t-line enclosure for his personal vehicle???

You can make a transmission line virtually any volume you want. You can make it bigger than a ported box, you can make it the same size as a ported box, you can make it smaller.

That's actually one of the things that make it so confusing; there aren't any 'standard' alignments, unless you count the ones that were published in Speaker Builder back in the 90s.

For the most part, the efficiency will be dictated by box size, due to Hoffman's Iron Law. IE, if you want a smaller box, you're going to take a hit on the efficiency. If output is all you care about, you can go crazy with the size and raise the efficiency. Taken to an extreme, you wind up with something like the Danley Matterhorn. (Google it.)

As far as how to do it:

1) The easiest software to make them is Hornresp. If you really want to go nuts, you can use Akabak

2) I generally find that the easiest way to design a tline is to copy Bose. I posted a thread here that has good info on how to do that: http://www.diyaudio.com/forums/full-range/243483-improved-transmission-line-alignment.html

Edited by Patrick Bateman
Link to post
Share on other sites
  • 2 weeks later...
  • 3 weeks later...

Iv been reading through this here and there for a couple days... Iv got a kicker 06cvx d2 (I used to have 2) w/ a kicker zx1500.1. I'm trying to get this single 12 as loud as I can until I have the disposable income to upgrade the whole shebang. (Which likely won't be for awhile) I'm pretty decent with power tools so I figure I may try building one of these 1/4 wave boxes one of these weekends. One of my questions is, how big of a deal is the # of folds/turns? I have an explorer so I can be kind of flexable with box dimensions but would prefer to keep the box as small as I can, I still gotta be able to put a stroller and shit back there once in awhile haha. So far if I did a U turn box with a 15x6 port at 40 hz it'd have to be something like 39x16.5x14.25ish, which would work ok if I design it to be a side firing port, (would that sound fine?) but if I want a rear firing port, that'd end up being right against my tailgate. Which is why I'm wondering about the # of folds so I can change that. BTW my mind is kind of set on doing a down firing-woofer box either way. So the sub doesn't get damaged by other stuff I throw back there. My entire cargo area measures 42" wide (between wheel well humps) x 35" deep x 17" to the top of the back seat. (At 14" tall I could go 38" deep due to the seat angle) Maybe somebody could come up with a better design? I'm going off tuning the box to bass boost freq method. The 06cvx has fs-27 hz, qts-.360. Thanks for any input.

Link to post
Share on other sites

Yeah screw it once ya gotta start involving flares and tapers and all that I'll just stick with a regular ported style box. No computer and not enough phone storage for all the different box building apps and all that. Seems very interesting though, eventually I'll try it.

No you don't. All you have to know is how to calculate line area and tuning, which is infinitely more simple than calculating a conventional vented or bandpass enclosure. I've built lines with reduced area, oversized area, without wave guides, tuned above Fs, tuned below Fs and not one of them was "bad".

You may build a line that performs less well than it could but you'd be hard pressed to build one that sucked.

  • Like (+1 Rep) 1

Facebook: facebook.com/audioanarchyllc

Instagram: audioanarchyllc

Youtube: youtube.com/bbeljefe

aaresizehorizontal_zps47821bb2.jpg

Link to post
Share on other sites

Yeah screw it once ya gotta start involving flares and tapers and all that I'll just stick with a regular ported style box. No computer and not enough phone storage for all the different box building apps and all that. Seems very interesting though, eventually I'll try it.

No you don't. All you have to know is how to calculate line area and tuning, which is infinitely more simple than calculating a conventional vented or bandpass enclosure. I've built lines with reduced area, oversized area, without wave guides, tuned above Fs, tuned below Fs and not one of them was "bad".

You may build a line that performs less well than it could but you'd be hard pressed to build one that sucked.

ok, so if I built one that just had a simple constant area, would that make it a "one note wonder"? Also, I'm a little confused about the method of tuning to the bass boost freq and how the woofers fs correlates with that, if I did that would that mean that it would have a flatter response at and below the tlines tuned freq? Maybe I'll give it a shot with a constant 15x6 port for starters and see how it goes. I just don't wanna risk the time/money but sometimes ya gotta, right? Thanks Edited by Christopher Cleveland
Link to post
Share on other sites

Yeah screw it once ya gotta start involving flares and tapers and all that I'll just stick with a regular ported style box. No computer and not enough phone storage for all the different box building apps and all that. Seems very interesting though, eventually I'll try it.

No you don't. All you have to know is how to calculate line area and tuning, which is infinitely more simple than calculating a conventional vented or bandpass enclosure. I've built lines with reduced area, oversized area, without wave guides, tuned above Fs, tuned below Fs and not one of them was "bad".

You may build a line that performs less well than it could but you'd be hard pressed to build one that sucked.

ok, so if I built one that just had a simple constant area, would that make it a "one note wonder"? Also, I'm a little confused about the method of tuning to the bass boost freq and how the woofers fs correlates with that, if I did that would that mean that it would have a flatter response at and below the tlines tuned freq? Maybe I'll give it a shot with a constant 15x6 port for starters and see how it goes. I just don't wanna risk the time/money but sometimes ya gotta, right? Thanks

I've never heard a line with that narrow a bandwidth. And I have no idea what you mean by tuning to bass boost frequency so I can't speak to that.

As for tuning to Fs, that's the starting point, not the only point. If you're building a line for the purpose of pure sound quality or if you're building a full range loudspeaker, tuning at Fs is important. But if you're building a subwoofer line, with a typical high Fs car audio sub that performs well at lower frequencies, tuning below Fs is a good idea. And the loss of upper end frequency response will be negligible.

Facebook: facebook.com/audioanarchyllc

Instagram: audioanarchyllc

Youtube: youtube.com/bbeljefe

aaresizehorizontal_zps47821bb2.jpg

Link to post
Share on other sites

UPDATED with new pics, different subs, sorry about the wait peopleOkay, some people will hate me for posting this, hopefully no one on the great world famous SMD forums :^ But I see alot of people asking about 1/4 wave T -line, Horn design/theory. All I ever see is people sending links, and thats all I ever did to, was send links- to confusing brain boggler websights. When honestly, 1/4 wave theory is easier than trying to calculate port dimension with no program. Anyone with simple 8th grade- no scratch that, 6th grade level math can calculate tline enclosure dimesnions.Most websights say how Tlines are un-realistic for cars, yeah, a 15" with a 24hz Fs, is pretty unrealistic. But a 12" with a 40hz bass boost can be as small as a sql box, for the same subwoofer. 40hz quarter wavelength is only 7.06ft long (round to about 7ft) When 24hz is 11.77ft long, and then multiply that 11.77ft by the SD of the cone... Pretty damn big box Just 1 -15" tuned at 24hz will yeald about a 14+cf box. Maybe good for a large van, but definitley not a car. Over the years I have learned tricks, and short cuts to tlines. I stick with tlines, because personally, its the Perfect box, for your sub. No more of that, "What box sounds best for my sub?" If you do a tline based on your subs Fs, That IS the perfect box POSSIBLE for that sub. Its in the environment that subwoofer is built for, with absolutley NO amplifier strain, yet huge db outputs. I still have never pwersonally ran over 500watts to a tline, yet I always stay in the low 140db-high 130s with awesome SQ. Another Main plus side to tlines are, there is no back presure to keep efficiency up, xmax up, and allows the subwoofer to stop on a dime, and start back up faster than sealed, or ported designs.So, heres the formula, its simple, you would just need a pen , paper, and calculator. Quarter wave is all based on speed of sound, and length of the sound wave.Sound travels at 1130ft / secto calculate length of Freq Devide 1130 / (freq) say 30hz1130/ 30 = 37.66 ft long Full wave length But we need to devide this by 4- for 1/4 wave wich equals= 9.41ft longPretty long huh? And the worst part is, to have a true T-line, you need to keep the port/tunnel/line - a Line, that equals Cone area, or pretty close to it. If you have a 10" The average SD/Cone area is about 50-60sq inches (to find SD in inches, you measure the cone, by useing a tape measure, and measure from middle of surround, to middle of surround on opposite side) 10" is usually close to 9"- 8.5"-9". This is where Pie comes in 9"/2 = 4.5-------- 4.5"x 4.5"x 3.14" = 63.58sq"That is your Port AREA ( usually round this number Down- say 60sq")So, a Tline for a 10" with a Fs of 30hz, and a cone area of About 60sq inches, will be about 9.25ft-9.5ft long (rounded) Its okay to be a little off, because this is car audio tlines, the cars accoustics will not notice it, because of cabin gain. But, when building a t-line for a sub based on Fs, you need to keep in mind the speakers Qts, and Qms, they should be low for SQ, Qts of .40 and lower, and Qms of 7 and lower will work great. Qts is speakers total quality in Ratio to its electrical, and mechanical characteristics, Qms is the Mechanical ratio.If you want to run a sub for more of a spl use, its better to run a woofer off of a Bass EQ/ Amp bass boost circuit/ Deck boost. But it cant be mixed frequecies, like a deck with a 60hz boost, and a amp with 40hz boost, you need to cancel 1 freq out, or level the 2 freq's (there will be cancelation, and the sub will sound like its being pushed to hard-boost for tline have to be close to the quarter wave of the box as possible) This allows you to use a shorter tline length, in comparison to the speakers natural Fs quarter wave length. But Tlines, with Low Q woofers, like .30 and lower, you will be amazed how low the subs will play, lower than the boxes quarter wave length- almost down to the next octave- Cleanly. So, your looking at about 20hz almost as loud as the subs 40hz peak tunning. (depending on cabin resonace of vehicle ofcourse)So, enuff explained. Lets go over the math, because thats where people get stumped the most.... This box in the tutorial I made sunday, I kind of dont want to give away to much, the rest you guys need to learn first hand. And the camera ran out of batteries, and the sun was going down, I REALLY wanted to finish it before night fall. So SOME pics, towards the end are missing.So, math--- Box is tuned to about 41hz. So... useing the formula up there^6.89 feet long x's The combined cone area of these 2 12s, I needed to keep a Constant 160sq port, 6.89' long. This box is PB- 3/4" The customer isnt paying full amt for MDF- haha.. oh well, I braced it very well. Notice all the 45s, even seperateing the 2 woofers, that is to keep the air flowing Cleanly, so no turbulance effects sound, or spl, and again, Reinforces the box for strength. I even filled larger gaps with Bondo, and painted the inside with blue paint, to keep the box from absorbing to much moisture- I will resin it soon-where I can.So, I started off with the wood cutting. I got all my basic cuts, then copied all the OD cuts with a router, so I dont screw up sealing joints later.

this is where I got the idea about tuning the enclosure to the bass boost freq (40hz) instead of the Fs of my sub (27hz)
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.




×
×
  • Create New...