[shep]

I have been reading about OB's until my head is burning, to say nothing of other types you all rave about. Fact is almost no one talks about TL's. Is there something horribly flawed about this approach? Obviously self-interest motivates this topic since I have a pair and adore them! Here's the link and if you are good you will find my wimpy review. http://www.crafty.nl/ I don't want to read a white paper about how and why, but I would appreciate more sharing from experienced users... driver types, crossovers, cabinet etc.
I am astounded at how much good, deep bass my tiny drivers can create and the general sense of ease and spaciousness. I don't know if this is typical of the breed or I just got lucky. I have always avoided the topic of room treatment...I don't want to add to the obsessions, but perhaps small drivers+downfiring/porting, reduces the issue of exciting room nodes somewhat. Just a thought, probably wrong too.

[JLM]

Shep,


I've been a fan and user of transmission line (TL) speakers for 30 years.  I've not heard all brands/types by any means and understand very little about the underlying math behind how they work.  But one listen (and months of pondering what I'd heard) was an epiphany to me.  Bass response is extended with slow roll off that "tricks" the ear into augmenting even more bass than what's there while better complimenting room gain.  The typical impedance bass hump is reduced, making it an easier to drive load.  Most of the sound inside the cabinet is vented out versus coming back out through the semi acoustical transparent speaker cone as a smearing of midrange frequencies. 


The three reasons most cited for TL speakers not being more popular are:

1.)  They're large.  That's bunk.  Your speakers show that.  A friend had standmount 2-ways with 6.5 inch midwoofer that easily fit on a stand.  Yes they can be large, but compared to OB or horns that could go as deep, they're tiny.  Still smaller than comparable performing sealed boxes and about the same as vented.

2.)  They're complicated to build.  TLs typically require additional internal panels used to create the "tube".  Certainly not rocket science and IMO easier than veneer to deal with.

3.)  They're difficult to design.  Until the Martin J. King MathCad application was developed a few years ago, they could only be "designed" by trial and error.  Even with the application it is more difficult than the  very simple (elementary school level of math) used to design sealed or vented cabinets.  And the application also requires mathematical trials to achieve the optimal design versus the one time through method for sealed or vented.  But this can be done in less than an hour once you have the software and know how to use it.


Previously I owned various forms of Irving M. (Bud) Fried speakers.  Bud was a contemporary of Paul Klipsch and an audio pioneer, but had the misfortune of having his companies ripped out of his hands a couple of times.  His love was acoustical music, but his family realestate holdings kept him from doing more with audio.  Bud has passed on a few years ago, but a company still exists by his name that apparently is still trying to carry on his work.  A good starting place to learn more about TLs is:

http://www.t-linespeakers.org/

My current speakers were designed and built by Bob Brines.  They use a single driver, the mighty Fostex F200A, and are rated 30 - 20,000 Hz in room, 89 dB/w/m, 8 ohms.  Bob (and I) believe in inert cabinets, so these are MDF, concrete backer board, and braced.  He offers a few different designs and can be comissioned into others (that's how I got the first pair of FTA-2000 speakers  )  BTW Bob does good work, offers very good prices, and is most pleasant to deal with.  He also offers his speakers in plan, panelized kits, raw cabinets, or fully completed forms.  Here's his link:

 http://www.geocities.com/rbrines1/

[chadh]

It's funny that this topic should come up right now.

My current speakers are Omega Super 3 XRSs, and Louis now has the new 4.5" hemp drivers available.  If and when I get the replacement drivers, I'll have a little pair of 4.5" fostex drivers without a home.  So I thought it might be fun to try a project like the ones this guy does:

http://www.t-linespeakers.org/projects/sampson/index.html

Making transmission lines out of 4" PVC seems about the level of difficulty with which I could comfortably deal.  I think he tapers the line by inserting tapered 2x4s into the PVC, although I wonder if there are better options.  Does anybody have any experience with this sort of project?

Chad

[GHM]

I have always avoided the topic of room treatment...I don't want to add to the obsessions, but perhaps small drivers+downfiring/porting, reduces the issue of exciting room nodes somewhat. Just a thought, probably wrong too.

I don't know Shep..you maybe on to something. Until I experienced a good TL...I thought the room was my problem with boomy ill defined bass. The TL changed my thinking completely on this. All the issues with bass are a distant memory. I've read many post where guys consider room treatments to be a must. I'm sure in some systems they are...just not in mine at the present. If I still owned those fullrange bass reflex speakers I'm certain I would have all kinds of bass traps trying to cure the speaker's flawed bass hump.  Instead of trying to bandaid a poorly designed speaker. I personally would rather start with a well designed speaker and work the room and equipment around it.

By the way, you described the sound of a good TL very well!

[JLM]

Chadh,

Those PVC tubes strike me as better suited for someone that prefers the workshop to the listening room. 

OTOH I've stumbled across several designs that use PVC pipe which makes sense in that the basic shape is inherently strong and the material should be fairly inert.  According to classic TL design, it seems like the pipe should be bigger and have the driver mounted about 1/4 down from the closed end. 

He also mentions the need for baffle step compensation.  Louis found (and I heard it too) that the Super 3 had better midbass fullness with it's wide baffle versus the earlier TS-3's narrow baffle.  Now you're looking at designing a circuit or adding some sort of panel on the front.  BTW there are a couple of wide baffle TL designs out there.  The E J Jordan site has one for their 92S extended range driver.


Shep/GHM,

Interesting thought regarding need for room treatments with TLs.  I've lived with them for so long I never considered that factor.  But it does explain why adding  six GIK 244 panels didn't really rock my world (noticable difference, but nothing major).

[shep]

aa Nice! I expected.. a few polite comments, along the lines of "well he hasn't heard a good OB or my ribbons"! This is more like it. I guess my guy did his math correctly, chose his drivers well, his crossover ditto, and knows how to build a good cabinate because I can't fault what I hear. I have had many kinds of speakers ranging from Maggies to various boxes, mostly British like Pro-ac. This is my first experience with TL's and I am very impressed. I wish I knew what the drivers were but a know legable friend said "Very Good", just looking at the photos. Speaking of room loading, these are really easy to set up. I found the sweet spot in one afternoon. With other speakers, in various rooms, it was a real pain, The Maggies in particular drove me crazy: one person in one spot and don't move your head. I'm exaggerating a bit but with these it was a joy. They just slotted into their place in the most natural and rational way.
I will probably never understand (being a math dunce) how a tiny driver can go down to 40 with such consummate ease and authority. To add to this I must say that I am not driving them "properly". It is a miracle they sound so good since I'm presently using a T-amp that hardly puts out 10 watts. I will soon have a "real" match with a 100watter, also Tripath design. Then I will really get to hear what they can do.
It may be just good old synergy or luck but the Tripath-based amps are a joy on this speaker.

[Daygloworange]

Shep,

While touring the high end shops a few years ago, I came across PMC speakers. They use a lot of TL designs. I really liked what I heard. (FB1 and OB1 models, I believe) They were quite pricey.

This led me to building a pair of GR Research AV/3's which are a TL design. I loved them. Very good bass. I now also have GR Research OB 5 (3 way's) which are open baffle mids, with a ported cab for the bass section. The OB 5's were more difficult to integrate in my room. I had to do quite a bit of bass trapping to get them sounding right in my room. Same thing with other ported speakers. It has since tightened up very nicely. Interestingly, the AV/3's were no problem at all. I don't know why exactly, but I think the TL has very different room loading characteristics. They are easier to set up and less of a drama. They integrated seamlessly with my sub as well. No issues. It was too easy.

I have also heard some custom built TL's using Lowther single drivers. They also sounded very nice.

I think your gut feeling about TL's to be right. Everthing I've heard that is a TL design, I've found to sound very nice, and perform remarkably for the size and driver configuration.

Cheers

[SET Man]

Hey!

  I'm no speaker expert but I built my TQWT Single driver speaker. This is a relative to the TL scheme. I have to say that from what I've seen and expriecne building my own speaker I have to say that TL is a much better way to load the woofer than... say simple bass reflex box.

   But like JLM said it is not easy to do and they tend to be larger than BR box. But when done right the bass is much better... well at least to me.

   Well, hard to say some people like bass sound of sealed box, some like bass reflex, some like TL and etc.

   You know if I had time, money and more importantly space.... I want to build myself a sub with 10"-12" woofer in a 8'-10' long TL/TQWT cab aa

Take care,
Buddy

[Double Ugly]

The best bass I've ever heard came from a transmission line speaker, the SP Technology Revelation.  Sooner or later, I'll have a pair or a pair of their successor, should there be one.

Check here for more comments about the Revelations' bass from myself and others.

-Jim

[shep]

Nice to be in such good company or rather I should say, to have it confirmed..that I am not making this up...you know, having bought something, needing to be reassured. I just wish this speaker wasn't a European-only offering, costing too much to ship. It really is a honey. I wanted "small" but I wasn't expecting such a big bold assured sound. Now to give them the best amplification and source I can manage.

[JLM]

It's apples and oranges to compare cabinet size of BR to TL as the roll off is of different orders.  Its a common misconception that TL are bigger than BR.  Probably because those interested in fast, musical bass also want deep bass so the overall speaker naturally ends up getting bigger.

I wonder if the term "TL" gets overused as some sort of elusive marketing verbage because of some of the very small and perhaps questionable products I see it associated with including the dreaded Bose radio and TBI subs, the tiny TBI Majestic Diamonds single driver cubes, even SP Tech speakers (that are good products but don't provide information of the interior and have relatively small cabinets compared to the drivers used).

Generically a TL is a quarter wave resonator, so maybe all the above qualify that that basis, but it leaves me scratching my head.  OTOH now that TLs can be designed the bar has been raised (at least in my mind).


Shep,

Since the bass impedence hump is minimized with TL, they make for an easier load.  The resonator aspect of TLs allow them to couple with the air inside the cabinet to improve bass performance.  I was running my Bob Brines FTA-2000s (89 dB/w/m, 8 ohms) with a Clari-T (similar to your amp) with acceptable results in a 2,000 cu. ft room.


Buddy,

Careful what you wish for  .  I've had two pair of 8 inch driver based TLs.  My current FTA-2000s are single driver but rated down to about 30 Hz at 103 dB (plenty for nearly all musical forms).  The previous ones where Irving Fried Model H derivatives (each channel were 6 cu. ft cabinets) and were rated up to 114 dB at 17 Hz.  I simply couldn't afford a big enough room for them to sound good, but they sounded so mavelous in a 20,000 cu. ft. chapel (using a 20 wpc NAD) that I donated them. 

[Dan Banquer]

I've owned Fried G3A's for years which have T Line midrange, and a "line tunnel" for bass. If Fried Products comes out with a kit of the Studio 7 I might go for it.
I've essentially stopped going out to audition other speakers as the rest of the market leaves a lot to be desired, and I"ve got better things to do with my life than listen to crappy speakers.
Subjectively speaking, you can't beat the linearity of well implemented T Line, and the G3'As are one of the least reactive speakers to the room that I have ever dealt with.
                    d.b.

[Double Ugly]

I wonder if the term "TL" gets overused as some sort of elusive marketing verbage because of some of the very small and perhaps questionable products I see it associated with ...  even SP Tech speakers (that are good products but don't provide information of the interior and have relatively small cabinets compared to the drivers used).

Generically a TL is a quarter wave resonator, so maybe all the above qualify that that basis, but it leaves me scratching my head.

Wow... what happened, JLM?  Wake up on the wrong side of the Peninsula today?  It's not like you to cast aspersions w/o cause, especially when it goes to the heart of a business someone relies upon for their food and shelter. 

First, have you heard an SP Tech product?  Just wondering where the "that are good products" comes from, irrespective of the "but" that follows.

Secondly, is this -



your idea of "relatively small cabinets" compared to any driver 10" or less in size?

Since the Revelation is the only SP Technology speaker to have a transmission line, you're gonna have to 'splain this one to me.

Addendum - As for not having provided information on the interior, the Revelations employ a "Proprietary Optimized Transmission Line" according to SP Tech's website.  The proprietary nature of the design might have something to do with Bob not providing the information, and I can only assume it has a lot to do with the fact that they sound better than any TL, sub or 'conventional' woofer set-up I've heard to date.

-Jim

[nodiak]

Good thread shep. As a hobbyist I made alot of the TL designs that showed up in Speaker Builder magazine in the 80-90's and loved them. Small ones like John C0ckcroft's up to some larger 8" mtm tl's. I only strayed form any floorstanders because life got in the way for awhile. You're right they are smooth and work well in the room.
Good to hear from Dayglo and his experiences with GR A/V-3. I've been looking at that one lately. Thought about the OB5's too as I like ob's also. I think loading the bass drivers in a TL instead of vented could work well for the OB5's.
I still haven't tried any of the recent wave of mltl's, need to get to that with the 8" hemps.
Don

[shep]

Does my speaker, as seen in cross-section on their site, qualify as a quarter-wave resonator? i.e; a "true" TL. As a matter of interest, they SEEM to really like the solid core single OCC wire I feed them with (shades of Anti Cable). I say seem, because I have nothing else at hand...nor wish to. I ordered more of this wire to try it running freely rather than twisted (I'm the twisted one!)

[shep]

http://www.crafty.nl/techniek/images/PICT6576.JPG