T line Design - 4th order vs Isobaric

Many of you guys have asked that I cover T-line designs. Here I give 3 designs of transmission line designs I have in mind for my Dayton Audio Reference 8 woofers. Hope you guys enjoy Follow me on Twitter @budgetbass
/ budgetbass
Connect with me on FaceBook
/ budget.basshead.1
Check out my pics on Intagram
/ budgetbasshead
Check out my latest Videos on KZbin
/ budgetbasshead

[@BudgetBassHead]

My Daily Driver: Skar Audio EVL-12: kzbin.info/www/bejne/nZiZdKKvq8ild5I

[@MrDJ317]

This dude sounds like Steve Harvey. Lol. But he’s very smart though.

[@BIGDADDYFRESHx]

The enclosure @ 13:21 is not isobaric because the airspace between the two drivers is not sealed. I would flip your outside woofer around and mount your two woofers cone to cone . This cuts amount volume needed for the sealed chamber of your 4th order in half. You would need an extra baffle but the amount of space needed between woofers is tiny just enough so the cones cant touch.

[@JMHGlass]

Please build them and let us know. No reason for speculation. Build it!

[@liamcooper5202]

Ok your 4th order T-line would be a waste of wood and power. You will loose all of the low end that makes a T-line so good. As for cone excursion use a subsonic filter around the fs of the subwoofer you are using or around 25Hz (depends). But it is rearly needed as the cone needs to push the full mass of the line unlike a reflex box. Now your "iso" setup.... what can i say but that is not a iso config. For it to be an iso config the two woofers must face eachother and be sealed together. A T-line will play 1/2 octave below port tune and 3 or 4 octaves above. Also your back wall is too close to the woofer and reflects right back at the woofer. You are better off extending the chamber and tapering it down so the cross sectionial port area is equal to the Sd of the woofer then 45s or rounded corners. Further more a line area does not need to be the same all the way but can slowly tapper down from the initial area to the Sd of the woofer as the final area. Keep up the work mate.

[@BudgetBassHead]

Thanks for the reply. I have to add, iso setups does not need to 'face each other', but they do have to share a common volume of air(sealed). So you were correct about that. I like the notion of 'tapering it down...' I have actually been interested in that design. But isn't that more of a tapered horn design? Regardless, great comment; it gets my mind to thinking. Keep them coming!

[@liamcooper5202]

BudgetBassHead If what your saying is correct any 2 sub sealed inclosure is an iso setup and that doesnt sound right. Its only a horn if you tapper to a larger area. But tappering to a smaller area is not a horn but rather called something else. The reducing tapper also helps reduce the chance of standing waves but its rare to start with.

[@BudgetBassHead]

To clarify, isobaric configurations can be configured cone to cone(face to face), cone to magnet, or magnet to magnet. As long as they share the same space 'between' the drivers. I did a video on this. kzbin.info/www/bejne/eXm7kIt-dsh0etE Thanks for the feed back.

[@BudgetBassHead]

And to add to this, the shared space between the drivers doesn't necessarily have to be sealed. As long as the amount of pressure there remains consistent throughout operation.

[@liamcooper5202]

BudgetBassHead Ok well this is the first i have seen of the other 2 configs. But now scanning a few engineering designs and articles on the matter i am yet to see one that "vents" the shared chamber, and thinking about it, it would be hard to mantain equal volume and pressure if one cone can move more freely due to the vent. But do try it if you wish but from a theoretical mechanical and physics standpoint i could not see it working in that config you showed but still willing to be proven wrong. 😊

[@louiemares1610]

great videos I'm learning so much I thought putting a speaker in a box was that simple but it has gone way out of control as far as the perfect signal or sound very confusing

[@bshupejr]

On your third example, I think you would have to make the port area equal to the cone area of both woofers not just one. You might get more output but the enclosure would need to be much bigger. Might as well do a single 10 or 12 at that point.

[@BudgetBassHead]

No single bass reflex box could trump a transmission line design; unless SPL is the focus. Bass reflex only cover a narrow frequency response, whereas T-Lines have a significantly broader frequency response range.

[@chaseleim4773]

Cone to cone push pull isobaric Sixth order t line

[@beezwelliver4806]

oh i forgot to mention these boxes really are the most effective in conjunction with a second enclosure(ur car) lol. anyways the backwave is key, leave ur trunk/ hatch open an listen to a tline vs other enclosures. they may sound pretty close but close the hatch and no contest

[@modelnutty6503]

yup, same for "Earthquake" variation of a t-line

[@randomtube8226]

Stick with the original quarter wave t line design. The first one. Build 2. Get 2 plate amps that have five way binding post high level inputs and outputs.

[@michaelfessenden8601]

I want to do an isobaric push pull on the sealed side of the amp chamer and run the port on the other side . You would have to you're sealed side with the right volume. Right?

[@dustinmoore6551]

Would you have been able too add rings to the face of the box to bring the speaker out as oppose to offsetting the chamber in the rear of the first box you show in the video

[@BudgetBassHead]

You have a point there. Thanks fur the tip. Demo of the T-Line coming this week. Stay tuned.

[@430Xsidian]

Great morning Sir, your thoughts on a transmission line enclosure using two 12inch AmericanBass XRd4s subs I also have two 12inch Rockford Fosgate P2d4s.. which one do you think is better for the SQL goal I'm looking for. My application is in 02 GMC-Yukon XL

[@thecartruthreport8451]

My guess is it is super unlikely you would unload the driver in the second design as it is sealed behind the sub. 3rd design may not work as the subs will behaving differently as the back sub is sealed. If you face to faced the woofers in the 3rd tho...

[@UniCrafter]

I recently made a 4th order T-line, and its an odd one. So, its 1ft3 sealed, with a PA bass speaker as a driver, 12", ported into 1ft dia PVC stormwater pipe, about 4ft long. Thing is tuned around 50Hz, and holy crap is it efficient. The woofer is already 95dB efficient, and this box must bring it to 100dB. Thing on 100w is like my old 15" on 1000w. Something to note though, is the T-line loads the driver a ton, 5mm of driver excursion turns into 40mm air movement at the mouth. So, this is a tricky one. If you put the driver in a small sealed section, it should bring up its efficiency up higher, making a more smooth response curve. The T-line would have to be longer than mine though. Projecting from my results like 9ft for 20Hz tuning. It'd be a neat experiment to do though, hook it up to a small amp, or limit its power, try 4th order then standard config, and see if theres any results. From what I can tell though, with a longer line like this one has, if its a 4th order it'd just be a rumble box, nothing higher than 30 or 40. I did make a massive 8' tall T-line, with about a 15' long line, though I put too much packing material in it, so its effectively clogged and acts like an infinite baffle. Great animation too, enjoyed the vid, keen for more.

[@BudgetBassHead]

Wow! You have any photos of that? It sounds interesting. Thanks for sharing.

[@UniCrafter]

Not sure if this discord link will work, you can see its ratchet strapped together lol, waiting to install a more permanent mount for the pipe media.discordapp.net/attachments/341540422566281216/462271411721994241/IMG_3451.JPG?width=648&height=484

[@BudgetBassHead]

Wow that "is" massive! If you place it behind a couch or something that would be a great addition to a home entertainment set up. Thanks for sharing.

[@milesbachelor8747]

Again, late to the channel. Seems like the iso-B configurations to seal section subwoofer would be blocked by subwoofer in front. Bass waves would conflict

[@BamBamMotorsports]

In the third isobaric design, would you have to double the cross-sectional area of the port because there are two drivers?

[@kevinr4128]

whats the best design for 2 6" txx bdc4 audiopipe? looking at a tline horn!

[@gooblio]

If your isobaric was out of phase could it cause sound cancellation or interference ? It might even sound like an echo ? I don't know what I'm talking about , but just a thought.

[@suicidejoker4098]

Why not just put a double or triple baffle to compensate your mounting issue

[@kevinr4128]

how would a 6th order tline sound??????

[@williamnixon4056]

Delicious if I designed it.

[@BudgetBassHead]

You got my wheels turning...

[@kevinr4128]

@@BudgetBassHead any testing on this design thanks

[@Durolith]

your isobaric isnt proper isobaric it is a sealed sub with a massive air leak

[@trinithings5384]

What's up

[@bisnathlinc]

ok ok ok so which box is best?????????????????????????

[@williamtoth6186]

Man I just got a tline put together! I never thought of combining it with a 4th order. But my box has an old school jl 8w1im hoping it bumps. I just need to finish the stain on the box and it's ready to go. If you ever use a mid-range or full range speaker, you will really need to stuff the line with poly fill or something similar or the mids will come through the port all echoey. Sorry to ramble on, it's what I do on your vids. But keep it up man love the vids

[@williamtoth6186]

I think the iso 4th box would over extend that outside woofer. It looks like it's gonna run like a regular tline while also being pushed by the woofer behind it. Just my thoughts.

[@BudgetBassHead]

Wow, JL makes some quality drivers, let us know how it turns out for you.

[@BudgetBassHead]

It's just a thought(4th order) But with some of the comments, so far, I may dismiss it. But we'll see.

[@AmulLuthra]

Awesome information brother. Can you please help me out once i wanna know which subwoofer enclosure software do you use. 😇😇

[@BudgetBassHead]

WinISD Pro

[@AmulLuthra]

@@BudgetBassHead thank you so much brother 😊😊

[@magicyeti9256]

ISO SPL

[@gabrielflores411]

where do you get the air specs for your boxes

[@jonanderson4474]

From my research. One shouldn't mix sealed with vented. Especially in the same box. As for the fourth order. It would lose the half the cone efficiency. Plus if you are distorting or over powering. One wouldn't really hear it until it's too late. Unless you have an ear for it and pay very close attention to it. Not to mention the added work digging the woofer out for replacement. Classic t line would be the easiest to do. Why over complicate a known well configured design?

[@BudgetBassHead]

For the sake of science and FUN, brother! :) You make some valid points, but if you got the time and spare material... why not? Thanks for the comment.

[@marvinjohnson2173]

Go for it waiting for the update

[@bluestangGT2001]

No experience at all, but maybe just do a double front baffle so you don't have to do that offset on the inside?

[@BudgetBassHead]

Someone just made that same comment.

[@iiNgONYaMa]

What free program is good

[@bisnathlinc]

too much talking

[@gsxroyce256]

I designed my own boxes and I didn’t know until now, but what I’ve designed is t lines boxes in a way. I took a horn and straightened the port pretty much

[@Hesbonful]

You have fantastic videos and content sir. Unfortunately you rarely define things. Eg what is a T line? What unique does it do ? When is it indicated? At the end you end up speaking over our heads. Kindly, define things, at structural and functional level before diving into the meat of the matter . This way the 1M + of us not so technical, will be able to follow up , subscribe and recommend, Unfortunately, you have restricted your self to the audience of only the tech people. Thank you once again, I pray you consider my advice.

[@lawrencemiller2379]

In your experience what box configuration produces the most efficient variable sound for 2 dual 12 in subs ?

[@BudgetBassHead]

Either a dual 4th order or dual 4th order is common.

[@lawrencemiller2379]

@@BudgetBassHead so much has changed in a year.lmao I started with Wal-Mart's cheapest subs Duel. I have 4 Star duel 2 ohms 12 in.subs. I'm on my 4 th different box since then. Ive removed one back seat to stack them. Don't really want to lose all my back seating area. Its a four door titan. I really need a bed cover to move it all back there.

[@BudgetBassHead]

@@lawrencemiller2379 Sounds like you may have a blow-through build in the future! Keep us posted.

[@rightsidelanechoice7702]

If both woofers are in phase I think your pressure in the port will be less because the front woofer will cancel out the pressure of the sealed driver some what, try putting them face to face in phase.

[@terryfarmer170]

Would u need to wire it out of phase or not

[@BudgetBassHead]

Not unless the woofers were facing each other.

[@snytty]

I definitely want to see results of the iso, and then with both subs inverted 180°.

[@dwaynehendricks7842]

I'd say build one version of each, sell the ones you don't like.

[@haroldhprittjr7007]

I’d go for the push pull and see how bad it is it might be the next big thing !

[@clementc7297]

The driver are not isobaric in your shown configuration

[@randomtube8226]

Also another enclosure design to check out is the tapped horn.

[@iyona14granturismogt6gtspo7]

I like both of your interpretations of the t.line.

[@UltraCon79]

You can just add additional baffles or speaker rings to elevate the Subwoofer

[@BudgetBassHead]

True, But not flush mound after that.

[@beezwelliver4806]

did you ever end try this on a smaller scale? been thinkin of doing something like this with a passive radiator. Need something to experiment on to cure cabin fever

[@BudgetBassHead]

I got an eight inch T-Line on the channel. Go check it out.

[@jamest.5001]

Do you have any idea how a ported box sub would perform in a small sealed box? I Wes looking at it the other day. It looks like a 10" box. Cut out for a 12" it barely fits. It's running at 1 ohm. The amp is a soundstream tower series. And if it's doing what it says. It's getting 900watts. The sub says 250/500w it does better with that amp. But it still doesn't do how I think it should. It's the cheaper Rockford subs. Maybe the box is just way too a small. I been waiting for t lines!!!

[@BudgetBassHead]

I always try and stick with the manufactures specifications for sealed enclosures. Typically a 12 needs at least 1cu.ft. but that varies from company to company. The Vas parameter really plays a big role in determining this. You need good compression in a sealed enclosure. to much is too punchy, and not enough is inaccurate phasing. But focus on the f3 and try to stick with the maker's specification.

[@jamest.5001]

BudgetBassHead all I knows is. It sounds like crap! Even for a single 12" should do better. It doesn't go low at all. I don't have an exact frequency but it drops off hard below 40hz. And nearly nothing in the 30hz area. I tried a bass enhanced track. And my earbuds sound better. I didn't put this system together. And I never heard one sound so bad. It's like its highpassed at 45-50Hz! Most of the time when I build a system. I low Pass at 60 hz or so. It had a JL 250 watt mono amp on it. Then a duel 400, I put the soundstream DTR1. 900 on it. Supose to be 600 @ 2 ohm. And 900 @1 ohm. It is twice as loud .but that's not saying much. I have thought about doing a infinate baffel in a escalade. With 1-2 15" and the soundstream. Maybe . Lowpass at 60hz. Depending on the vehicle. I think it peaks around 40hz. Or the resonate of the vehicle.

[@terryfarmer170]

Isobaric and maybe flipping the outer speaker around to see if that affects the sound. But I like the design makes sense👍