Question about Transmission Lines

[svtcontour 10+ year member]

Hi everyone, I know this is not car audio related, but maybe you can still help. I'm interested in building my very first 3-way home speakers (I've already built a 2 way vented system which turned out real nice), and was going to go with a vented cabinet but I've been thinking about transmission lines because i've heard a lot about them but dont really know 100% what the benefit is over a vented cabinet.

Anyone have a quick and dirty answer as to why a transmission line might be better than a ported cabinet? I assume downsides would be complexity and size. I'm trying to decide on an alignment that would give me the most clean, extended and articulate bass. The goal is not SPL but just a sense of effortless bass. If I can hit a solid 30Hz, that would be idea.

Speakers will each contain a single Dayton RS28F tweeter, single Dayton RS150 6" drive and dual 8" Vifa PL22WR09 drivers.

Thanks in advance.

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[MANTI5 10+ year member]

DIY Speakers and Subs - AVS Forum

 

[svtcontour 10+ year member]

I'm guessing that you're telling me thats where I should be posting to get an answer //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[MANTI5 10+ year member]

There may be some here who can answer, but that forum I linked specializes in what you're looking for.

 

[kr15 5,000+ posts]

a tline provides an actual bandwidth where output is generally linear over that range, where as a ported enclosure will have a sharper response and a more pronounced peak. Downsides to Tlines are space they take up, and the fact that you CANNOT over power a sub in a basic tline. Positives are that they are so efficient and the bandwidth can be so linear and full, that you can literally shake a whole house with say 1 6" driver in a tline on moderate power

 

[Moble Enclosurs 10+ year member]

Great post kr15.

I will add my viewpoint on them, and try to keep it simple. Tlines are really not as simple so discussing them can get quite detailed, but for sake of argument, Ill be brief.

First, I must say that the Vifa drivers you chose are great candidates for the tline enclosure. You might have known that based on research but just to give you a designers point of view on them.

A tline can be expressed as an acoustical form of the electrical tline in which the impedance is reduced as a goal of transience. The ideal tline in HT design is one that is tapered negatively from the drivers radiation to the output opening (mouth area). This allows for the existence of low end reproduction without losing efficiency. Output may suffer in this design style (reverse tapered) due to compression constraints or reverse coupling effects, but the response smoothness is increase over that of a standard design.

The overall output of a tline is not based on resonance curves, though most websites may say otherwise, but more so on the entire pass-band of frequencies as a focal point, much like kr15 mentioned with linearity. This allows for accurate reproduction by separating the higher frequencies of NON interest with that of the lower end response all from the same driver. The distance separation and phase separation creates the FULLNESS that was previously mentioned, and also reduces distortion.

In a conventional ported design, a lot of the effects of reproduction is based on a separate goal of output, where compression is higher, and enclosure parameters limit the responses ability to produce low level distortion at the same efficiency as the tline.

I can go much further than this, but I hope that helped a little. lol

 

[svtcontour 10+ year member]

Great information. Sounds complicated!! I think i will need a really big book //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[hotcress 10+ year member]

Nah. Just get him to design one for you!

 

[Moble Enclosurs 10+ year member]

Nah. Just get him to design one for you!

Much agreed, lol. But seriously, that is what I do. And I am one of the best! (no overconfidence intended, just being honest)

 

[duanebro 10+ year member]

I like t-lines, I won't use big words, but they are worth researching. I would like to recommend asking this question over at partsexpress's forum. Just go to there page and click on the tech-talk link. You will most likely be asked about your xo and speaker layout. But you will get answers. And free design work if you are nice.

 

[svtcontour 10+ year member]

Man that would be great if i could get some guidance or a starting point. What info would you need? I have one of those Dayton woofer testers so I can try and get some actual measurements from the speaker instead of relying on the spec sheets. BTW I really like those Vifa PL22 drivers. I didnt initially buy them for any tline setups, but I was aware of many using assorted Vifa drivers in different transmission lines. I also have a pair of old Vifa P17WJ00 drivers. I think those also work well in this type of enclosure so if I ever did a 2 way, I guess that would be a candidate as well //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Much agreed, lol. But seriously, that is what I do. And I am one of the best! (no overconfidence intended, just being honest)

 

[CJL 10+ year member]

Heres a thread explaining it a little,dont know how correct he is.

Quarter Wave / T-Line tutorial-UPDATED - SMD Forum

 

[Moble Enclosurs 10+ year member]

Interesting thread. It does simplify the easier part of it I assume. But the ear can be very forgiving and I am taking a guess that no phase response or excursion control, or efficiency calculations are done during this method. I still tend to take into consideration much more than quarterwave theory. Quarterwave is only a beginning step for those who do not know much about acoustics. You can actually hear the difference between that and a proper Tline. Not bashing the thread at all, I think it is great for those who do not want much but a good box to use, but not all drivers work in a tline, even tapered. Much can be done that is not accounted for here. But again, great thread and thank you for posting it for everyone.

 

[wenn_du_weinst 10+ year member]

there is a huge difference in a tline made for subs and one that is designed to be used as your main speakers. It is much easier to make a bass cabinet sound ''good'' then making a full range enclosure respond flat and not beam. Do not forget the cross over, it's much more then just getting a preassembled 3 way and throwing it in an enclosure.

 

[Moble Enclosurs 10+ year member]

there is a huge difference in a tline made for subs and one that is designed to be used as your main speakers. It is much easier to make a bass cabinet sound ''good'' then making a full range enclosure respond flat and not beam. Do not forget the cross over, it's much more then just getting a preassembled 3 way and throwing it in an enclosure.

This is very important if you plan to do one for the vocals and highs, or even utilizing a full range driver. I find that the best one to use in the vocal reproduction is a reverse tapered tline-no compression chamber. Works very well for tonality.