Transmission Line Speakers are a Trap
ฝัง
- เผยแพร่เมื่อ 28 ธ.ค. 2022
- A pure transmission line speaker will completely absorb the back-wave from the driver, making it behave like an infinite baffle. The advantage an infinite baffle gives is that there's no cancellation from the output from the front of the driver and the output from the back of the driver. The output from the back is thrown away and only the output from the front is used.
In reality, this is almost impossible to do fully, and that's especially true where a speaker box is concerned. You'll never be able to absorb 100% of the back-wave (with current tech), so a compromise is reached in the "transmission line" speaker by using some of the back-wave energy for the overall output. This is done by making the pipe length, damping and taper so that it channels the back-wave out and it is now in phase with the front-wave. This extra energy adds to the front-wave, boosting output.
The pipe is tuned so that by the time the back-wave travels through it, it will have shifted in phase to match the output from the front. And while it seems like it would be relatively easy to do that, designing and constructing a box to hold that pipe is more complex than nearly ever other type of speaker. And in my opinion it's questionable whether the results are better than a much less complex (and typically much smaller) ported box.
But even when he know this, that doesn't stop the DIY speaker builder from taking a crack at it. And I have to admit that while thinking about the subject for this video, I find myself drawn to the idea again.
The one shown in the video thumbnail was very quickly drawn for this video. It shows the typical implementation of the folded, tapered duct with the output opening on the front. Along with this the duct would have to be stuffed with damping material to tune the response and reduce the ripples the long pipe adds to the response. These ripples extend up throughout the effective frequency range of the driver and can be difficult to get rid of. And I'm not unconvinced that the ripples are not what people like about these speakers - that extra "stuff" that's not there in other designs.
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A pure transmission line speaker will completely absorb the back-wave from the driver, making it behave like an infinite baffle. The advantage an infinite baffle gives is that there's no cancellation from the output from the front of the driver and the output from the back of the driver. The output from the back is thrown away and only the output from the front is used.
In reality, this is almost impossible to do fully, and that's especially true where a speaker box is concerned. You'll never be able to absorb 100% of the back-wave (with current tech), so a compromise is reached in the "transmission line" speaker by using some of the back-wave energy for the overall output. This is done by making the pipe length, damping and taper so that it channels the back-wave out and it is now in phase with the front-wave. This extra energy adds to the front-wave, boosting output.
The pipe is tuned so that by the time the back-wave travels through it, it will have shifted in phase to match the output from the front. And while it seems like it would be relatively easy to do that, designing and constructing a box to hold that pipe is more complex than nearly ever other type of speaker. And in my opinion it's questionable whether the results are better than a much less complex (and typically much smaller) ported box.
But even when he know this, that doesn't stop the DIY speaker builder from taking a crack at it. And I have to admit that while thinking about the subject for this video, I find myself drawn to the idea again.
The one shown in the video thumbnail was very quickly drawn for this video. It shows the typical implementation of the folded, tapered duct with the output opening on the front. Along with this the duct would have to be stuffed with damping material to tune the response and reduce the ripples the long pipe adds to the response. These ripples extend up throughout the effective frequency range of the driver and can be difficult to get rid of. And I'm not unconvinced that the ripples are not what people like about these speakers - that extra "stuff" that's not there in other designs.
Transmission Lines come in all shapes and sizes, including sealed transmission line. For me, when I say "Transmission Line" I mean QWTL
th-cam.com/video/jV0Ljnn8L0s/w-d-xo.html
Been designing and building t-line exclusively for over 30 years
th-cam.com/video/3qjWKUBvSNA/w-d-xo.html
th-cam.com/video/-96WAVQdcyQ/w-d-xo.html
th-cam.com/video/qm5K_VVRwXQ/w-d-xo.html
th-cam.com/video/Jdb2mbmL6jg/w-d-xo.html
th-cam.com/video/J92zJIDOi1Q/w-d-xo.html
And of course, the Jensen Transflex th-cam.com/video/6yb2msOQw_4/w-d-xo.html
Your first sentence is not how I understand transmission line speakers - even in an ideal design. And full disclosure - I have designed and built 3 mass loaded transmission line speakers, and I am selling the build manual for one of them.
The back wave of the woofer is definitely being emitted from the terminus opening. In the program I used to design mass loaded transmission lines, called Hornresp - shows this.
And it also calculates the effect of the acoustic path on the *outside* of the cabinet from the center of the terminus opening to the center of the woofer. So, you have to have the cabinet layout and construction, as you work in Hornresp.
The image on your thumbnail shows an "old school" type of TL - the woofer is located right at the closed end. This almost always has a major trough in the output. The current design thinking, is to have the woofer located between 25-33% of the way away from the closed end - this sets up a much better set of resonances, and when done correctly, there are virtually no dips in the output.
And it takes a very sophisticated program to do the myriad of calculations of all the dimensions of the inside of the cabinet. There is simply no way to do this without the 3D acoustic modeling program. You load in the full Thiele/Small data of the driver you want to use, and then you put in the area of each section, and the lengths, and also the amount of polyfil, and where in the TL it is located. It is a long iterative process.
@@NeilBlanchard Hi Neil. My point was that after all of that, you basically worked 5 times harder and longer to produce a speaker that almost certainly has no advantages over a ported design. A ported speaker will be smaller, use less material, easier and more forgiving to design and take less time to build. It also won't be plagued by midbass ripples, like the TL.
That was the point of this video, and not a comprehensive history and technical dissertation on the transmission line design theory.
@@IBuildIt That's not been my experience with TLs - my cabinet uses 10 pieces as functional elements (plus 1 for an access panel). The 3 main additional parts that provide the volumes that form the TL, also act as braces. The 4th is an actual brace, in the closed end, to support the span on the front baffle between the drivers. So, there is near-parity of difficulty of construction. With CNC cutting, it is no more, and no less difficult. As far as material used - I am making a pair from a single sheet of 5x5 18mm Baltic birch. The speakers are 9" wide X 21.5" high X 16" deep standmounts.
The ripples you refer to are often there on "old-school" TL designs - *however* with powerful 3D acoustic modeling programs like Hornresp - the response is remarkably smooth and extended. In the case of my design, the driver Fs is 35Hz, while the fundamental response of the mass loaded transmission line is 32Hz. This is a 6" paper coned SB Acoustics midwoofer.
The bass quality is better than any speaker I have ever heard. Since the "column" of air is coupled with the woofer cone, and thereby adding its mass - it is working on a very different mode than a ported speaker. The air is *not* acting as a spring in the TL between the woofer and the terminus opening. So, the air pressure in the cabinet is lower, and this reduces the tendency for the cabinet to resonate.
The bass distortion of a MLTL is lower than a ported design. And the midrange quality is also better, in my opinion, because in its upper range, it is able to operate closer to how an open baffle works.
The *main* improvements come from moving the woofer away from the closed end of the TL, about 25-33% of the distance toward the open end. This allows the design to be smaller than otherwise. The overall "pool" of knowledge about TLs has grown, and the software and computing power has come a long way, over the decades.
I can send you the build manual of my MLTL-6 speakers, if you are interested?
@@NeilBlanchard Can I ask if you've used the same driver in a ported design and did a comparison? You'd have to have both speakers connected and switch back and forth between the two while listening to reliably say which one sounded better. Even better if that could be blind.
See, the way I look at it is this: there are not a lot of TL speakers being made and if they are clearly superior to a ported design you'd think they would dominate. Maybe not the low-end market, but certainly the high end one. Why haven't the big players clued into how much better this design is and turned away from vented as the preferred design?
This video is 100% John talking himself into building a new transmission line speaker!
Complicated? Diminishing returns? A new John Heisz design/build speaker series? Come on, that's what we're here for!
ROFL this vid is just the disclaimer for the new transmission line speaker build.
Yup!
I still think a QWTL is the simplest enclosure to get right without the aid of (toy) enclosure programs, that's why I've been designing and building them exclusive for over 30 years.
th-cam.com/video/jV0Ljnn8L0s/w-d-xo.html
th-cam.com/video/3qjWKUBvSNA/w-d-xo.html
th-cam.com/video/-96WAVQdcyQ/w-d-xo.html
th-cam.com/video/qm5K_VVRwXQ/w-d-xo.html
th-cam.com/video/Jdb2mbmL6jg/w-d-xo.html
th-cam.com/video/J92zJIDOi1Q/w-d-xo.html
And of course, the Jensen Transflex
th-cam.com/video/6yb2msOQw_4/w-d-xo.html
In the early 70’s, my favourite speakers were IMF TLS80’s, phenomenal bass extension and control. I would buy them today if I could 🎉
Brings back pleasant memories. I used to build transmission line speaker in the early 70's based on the original designs of Arthur Radford. Fun times!
Audiophile/woodworkers never ever say "It's too much trouble to build, I'll just make a bass reflex instead"! The building is part of the craft. I made a tapered line from a Speaker Builder magazine article that used a Radio Shack Realistic 4" woofer and poly tweeter. Did I think it would sound better than my Boston A60? Nope, but it sounded decent. But it was my very first made from scratch speaker that actually looked good.
In the late 1980's, employed true pipes. 6 inch ID, Schedule 40 with 4, 90 degree, elbows/driver for a 12 ft long, "Waveguide", 2/channel. Used very little acousta stuff. The ,"Stuffing", back in the Day was thought to couple with the air in the waveguide/line and decrease the Velocity of a propagated wave in the medium, air. So, slow the speed of sound and permit waveguide/line to behave as if it was physically longer. Loaded each pipe with a, 6 inch Morel 164. The output was adjacent and in the case of the lower driver, below the driver, the output above in the case of the upper driver to couple the Morels together acoustically as I stacked the pipes one on top of the other, symmetrically, with 2, H shaped baltic birch plywood pieces siliconed to each line . The reason I chose a 12 ft length, the Mass of the air couples to the driver and lowers the Fs. Did achieve Bass flat to 23 Hz. I believe it was Ben Olney who realized this. I had taken Partial Differential Eqs. a couple of decades earlier and remember the inability of the Discipline to model Turbulence and employed the smooth walls of the pipe to minimize said Turbulence, hence increase laminar flow. Anyways, crossed over at 200 Hz, via single pole filter, to a Speaker Lab RD-57, a 2 inch wide, 54 inch long, push-pull, planar magnetic, dipole, driven by my version of Audio Amateur's Lang Amp. A MOSFET output stage, Class A Topology where I employed Nelson Pass and J. Peter Moncrieff's written advice to build out from the circuit boards. 350,000uf of double bypassed Capacitance, HEXFRED ultra high speed soft recovery diodes, for rectification, source resistors, Caddock metal film in TO 220 packages, 2 Toroids/channel, an output stage-unregulated, and an input/driver stage-tightly regulated, and really large heat sinks with a bias Current of 4 Amps. The Bass performance was very tight, clean and holographic, did what I required, gave me loudspeakers that equaled my Stax Earspeakers.
I really enjoy your channel. You are courageous, highly skilled, and open minded, so interesting too, in presentation.
Few people are able to explain more or less complex things in a simple but accurate and to the point way that it becomes fun to listen to. Also the laidback way of telling with a great sense of humor makes it entertaining. What a great teacher this man would be!
Martin J. King is an invaluable resource on Transmission Lines. He is the first to use computer modelling for this application. Puts it more in the realm of science than the black arts.
Actually George Augspurger was the first to model. He used an electrical derivative and Martin King used an mechanical one, they both overlap very well. I've used both
with outstanding results...
If you want to do a piano black finish then you basically have to bondo or putty fill the whole surface after sealing the MDF, then you sand it as smooth as you can with block sanding, then you spray it with high-build primer and sand it again. Then spray on a very light coat of black, sand that off to make sure that there aren't any low spots hiding from you, then layer on 3-5 coats of black before sanding it smooth up to at least 800 grit but no more than 5000 grit before you spray on between 5 and 8 coats of clear, sanding between every two to three coats with 2000 grit to knock down any orange peel. Finish by using a random orbital buffer and buffing compound. Also, be sure to seal any holes thoroughly with tape and some kneadable mounting putty since you'll have to wet-sand the surface to prevent the paint from clogging the sandpaper. For the absolute best results, try using lapping film as the particle size of the abrasive is even more tightly controlled than it is on standard sandpaper and will result in more consistent polishing. The reason why you can't sand the surface too fine between coats is because the paint bonds mechanically and not chemically between layers and you are relying on the next coat to fill in the micro-scratches in the finish in order to "grip" to the layer below it.
Honestly, Piano black does look absolutely stunning, but it is a huge amount of work to get that finish. I'd rather put a beautiful veneer on the cabinet and lacquer that. Just remember to rub in a thin layer of relatively concentrated lacquer for the first coat to prevent excessive grain swelling and apply two to three additional coats before sanding the finish flat. If the entire surface doesn't develop a hazy finish from the sanding then you haven't gone far enough. If you notice that you are sanding through the lacquer completely then stop and apply more lacquer. The goal is to get the final finish as smooth as possible, not to get the veneer itself as smooth as possible. Once you've managed to get to a point where you can get the surface uniformly flat and hazy, then you can step up to 2000-5000 grit before you apply at least one more coat, then move on to polishing with a random orbital buffer. Of course, this is assuming you want to achieve a glassy finish and you don't want to feel or see the grain and texture of the wood when the light forms a glaring reflection on the surface. I do think that satin finish wood that has just been treated with oil and wax is very beautiful, so it really depends on what you want for that piece.
If you know how to paint, there’s absolutely no reason to sand between color coats. Unless you are a terrible sprayer, you will never notice any of the orange peel in the black paint. As long as your clearcoat is smooth your paint will look smooth.
@@Rayman-cd8bd I didn't say that you needed to sand between color coats. The thin layer of paint that gets sanded off after the high build primer is to act as a marking coat to ensure that you have thoroughly eliminated the high and low spots and have a perfectly flat and true surface to paint on. Also, you will get a different sense of depth to the sheen if the color coat has zero orange peel before you move on to the clear coats. It's not a huge difference, so most body shops don't bother to do so, but piano black is a high end finish for a reason.
My understanding for transmission line is that they will play easily a 1/2 octave below the resonate frequency of the driver.
Hi, very interesting subject, I built a pair of transmission line Cabinets about 40 years ago the plans were out of a magazine from the 70s .
I just recently had to replace the driver units 8 inch woofer with a 4 inch Tweeter SEAS , I have not yet tested the frequency response but I have definitely changed I think they have improved tremendously, The line length is approximately 14 feet and they fire out of the bottom, The only thing that I’ve done differently is that I have raised them off the floor for another inch and I have tilted them forward, Some friends of mine have listen to them and they cannot believe how well they sound, My taste in music is very varied from classical to heavy metal and just recently got into Nordic folk music song is very dark and I listen to quite a lot of blues as well,
I have listened to your tutorials on HIFI by for , and it is always very interested. Keep up the great work.
PHIL FROM THE DARK SIDE OF THE MOULIN FRANCE, 🎼🔊🎶🎸
If you're using Martin King's or Augspurger model there is a difference if you're using a mass loaded model vs a tapered line with (same tuning frequency). He has recently commented that port compression is probably the reason for this, and the reason for last 30 years that I used as little taper as possible, 3:1 Thru 8:1. The ripple can be filtered out with intuitive placement of damping material. Using models from Martin, George Augspurger and even archaic Bailey models I have had outstanding results...
Hi. I was under the impression that a true T-Line uses a consistent line, i hear John mention that the line should always tapper down in size to a percentage of the cone, any thoughts you could share in regards to why it should be this way or benefits of doing this or others ways?
Really good explanation that non speaker designers can understand. The crucial thing about quarter wave transmission lines is getting that ripple under control and unbeknown to the unwary, the relationship of the position of the back of the speaker to the opening of the horn throat is critically important. Moving the driver even an inch off the critical position can cause significant spikes at specific frequencies and ripple beyond which is additive to horn ripple caused by pipe resonance.
The only way around this is to make a series of removable driver mounting baffles to experiment with driver position relative to the horn throat and use measurement to get the best result. Then the horn stuffing needs consideration. Some just stuff the pipe at each change of direction, others use a fixed amount of loose wool stuffing behind the woofer in the throat of the pipe, others line one side of the pipe using acoustic foam. Measurement is crucial to see the effects of tuning the pioe. Some calculate the pipe then shorten it by a percentage guessed at (perhaps 10%) to account for the effects of the stuffing. All that is before the headache of the crossover is concerned.
The biggest trap in most diy speakers is the crossover design. Most diyers guess or “calculate” the crossover values then tune by ear. That is like shooting in the dark and usually ends up miles out with screwed up phase alignment, non linear response, no idea of impedance effects, no consideration to effect of actual crossover point on polar response or driver resonance point/cone break up effects so distortions can be unacceptably high.
I only say this as a designer who hast spent more hours than I care to remember sorting out crossovers for clients who tried but struggled to get it right. Invariably, no client who didn’t use measurement to begin with got anywhere near close.
The other thing frequently got wrong is cabinet resonances resulting in wrong tuning or terrible looking water fall decay plots. Again, correct tuning cannot be merely calculated for port designs. It needs measurement of impedance v’s frequency to fine tune and get it right. Often, ported enclosures are over damped with baff which can sit on dynamics and result in overdamping of the woofer. Just acoustic foam panels are sufficient. Some manufacturers over stuff to get cabinet size down making the speaker cheaper to make.
Transmission lines are undoubtedly the hardest but even vented and sealed speakers have their pitfalls, especially achieving correct crossover, tuning, system Qtc and cabinet design which are all fundamental to sound.
I would agree that TL designs are not worth it to the amateur and no TL design I’ve ever heard convinces. All seem to have bass lag or obvious one note bass where peaks in response dominate.
I have had two pairs of "transmission line" speakers ( DCM TimeFrame TF-700 ) for decades and never knew what the term actually meant. Thank you for the post.
I had read about them in the 1970s but the first time I heard one was in the early 80s, a DCM in Texas. I currently have a TF-600 in my living room behind a stand-mounted Polk R200, the Polk has far better clarity and neutrality but the DCM has tighter bass and better spatial cues. It's probably time to refurb the DCM.
@@gregmatula9749 It's not a simple task with the "speaker sock" to deal with, but the drivers probably need it. The internal wiring is super thin and the crossovers aren't built very well either. There is a lot of room for improvements on the DCMs but I have always liked them through the years. I have had and heard better but I still like them.
@@01sapphireGTS I like them too. That little balanced drive Audax tweeter that so many companies were using throughout the 80s three of them, one on the front coax and two on the back, did a good job of an omni simulation. Sensitivity was pretty high on them, over 90 db, not a bad trade-off. My brother has the original Time Window I don't think it was a TL.
John you saved me from wasting my plywood LOL.. thank you. i wish you healthy life happiness and more spare time to build more speakers
Made a pair of sono tube speakers, 4" driver approx 14" long as per 1/4 wave length calculations w/ about 2" of fiberbatting. Super surprised at how well it sounded, recognizing a large part of it was luck.
The idea came from a Popular Mechanic outdoor speaker, comprised of two vertically nested sono tubes filled with sand in between, an up ward facing speaker w/cone reflector.
I commented on another video about phase plugs.
I fell into the transmission line trap as well as the piano black disaster just like you. They were good but they took a year of trial and error. Today they sit disabled in my barn 😢.
I made powered speakers with dsp in a week using drivers robbed from a pair of old Boston Acoustics. They sound like anything I want them to.
Live and learn
Love my DCM TF700 Transmission Line speakers!
My first pair of transmission line speakers and most definitely not the last!
Great video! ✅🍿
Great video, thanks for your knowledge!!!
Many years ago my electronics teacher in high school said, "I have always been able to prove everything I've shown you. Now we start on RF transmission and well there is witchcraft involved". The same is true for all transmission lines no matter the frequency.
One of the worst things that can be done with a TL, is placing the driver at the end of the line. Placing it at 1/3 to 1/5 from the end. This is the most effective way of reducing the ripple. And designing the line length solely on the Fs is really detrimental. Qts, with the woofers crossover inductor resistance needs to be considered.
Honestly, a MLTL (mass loaded transmission line) is much easier to design and out performs a TL
In both designs I talked about in this video the driver was placed part way down the line. Still had ripples to deal with (that also showed up in the modelling software). In reality, I don't think moving the driver away from the end gets you much of an improvement, while stuffing does make a significant difference.
I will disagree somewhat. Moving the driver does not remove the ripple, but decreases the intensity. Just as fill in its proper placement does. In my last mltl, a single fold, the woofer is placed at about 1/3 from the start of the line. Fill was added in the first section only. As could be seen in the impedance plot and freq response, the amount of ripple was negligible and further reduced in upper harmonics by the crossover.
But did you have the exact same design where the driver is at the start of the pipe to compare the two? And by compare, I mean listen to music from both to see if one sounds better than the other. Measurements are useful and helpful, but they'll often highlight things that our hearing doesn't pick up on.
I did not, but as the design was done by Paul Kittinger, one of the most respected MLTL designers around, I don't believe it's necessary. I have done others in experiment and it was audible, though slightly.
I found some old Realistic trans line towers, one single 8" driver and a tweeter, they sound fantastic with the new full range driver I put in.
When where they made? I remember realistic being touch and go, in the UK at least. I remember 4" 2 ways in a cast iron box too.
in the age of dsp a sealed enclosure does the job so much easier.
transmission line is for extended bass with only acoustical tools.
How did those speakers in your console stereo work thinking of trying to recreate that project
The more you study and learn about t-lines the more you Realize that you know nothing and as you said it's a fools errand.
Fool’s errand unless you like the frequency response of a fourth order system with the phase response of a third order system. Transmission lines are just better than ported. It isn’t magic. It’s math.
Meadowlark Audio transmission line from the 90’s to mid 2000’s. Amazing work and sound quality.
V. good treatment of the subject - in terms of a Christmas gift of great sound/bass extension, Santa might be able to make it down my chimney with something of that sort but I reckon he would have a lot of difficulty negotiating his way through all that twisty transmission line …. !!!!
Well, you see, and I created a transmission line from old Polish cabinets and I cushioned it with 3-4cm cm foam and I did not measure anything and I am very satisfied with the sound of :d If you are undemanding, the effect from these speakers will always be good, but of course, if you do it properly, it can be even better. Personally, I think it's better if you don't measure anything - it's better to create a transmission line speaker than a speaker with bass reflex. The bass reflex is just a dirty rumble with a great demand on the space of the :D
Whats your feedback on Irving Bud Frieds work please? Thanks
I heard a pair of TL speakers around 1990; sounded so good I had a friend buy them; less than $1000. Made I think by Genesis. Just a sloping PVC tube inside a slanted cabinet with a single smallish driver and a ribbon tweeter. Maybe I'm misremembering over the years, but I thought they sounded spectacular. Especially for such a modest speaker. IMO blows away the passive radiator speakers I've owned since. So I'm hoping someone jumps back on the derailed TL bandwagon.
Hey John, thanks for your informative video. I just built an open baffle project speaker design using TB W8-1772 FR drivers mounted on a 12X18 oak plank paired with an SVS 10 inch Pro 1000 sub. Although the sound is really amazing, I'd like to couple the design with an 8 inch woofer, ported or sealed box (undecided). Any thoughts on this concept?
Thanks, i do have pair of DCM Time Window speakers that sound incredibly good, spacious.
So if you could manage to add active noise cancelling to the inside of the subwoofer enclosure could you imitate infinite baffle with less spacial cost
Would the Klipschorn bass bin/folded horn be a variation of this style ?
Bose made a Sound Cannon for there panaray system, that used the transmission line concept. They sounded absolutely awesome in a 500 seat concert theatre, spent my late teens early twenties playing with them.
I bought a transmission line speaker (very similar to the japanese made speaker on youtube with millions of views) and the box is fully CNC, with lots of layers glued together. The speaker is not bad, but yes it resonates. You touched the point about TL. It seems almost esoteric to get it right.
an explanation like yours, which is good, would benefit a lot if you graphed (by hand, even on a piece of paper), what you are saying. Unless you only talk to those who already have a proper theoretical background.
You mention correctly the Martin J. King work. That works!
Many years ago I designed a TL using his worksheets and they sound really well!
And they sound differently from a a BR.
I have recently listened to an "Ekta Grande" (designed by Troels Gravesen): I'm sorry, my system is better. And very different.
Since its winter, I decided to move the Magnepans to the sidewalls and fire up the tube amp and Rega NAOS (TL) speakers.
My first experience of TL were the Rega Ela.
A visiting friend had to ask if the REL subs were on, since the bass extension got down to 27hz.
They weren't.
Nuffsaid
🎵🎶🤫🎶🎵
PS
I guess what you were trying to say is that TL design is best left to the pros?
Please build the transmission line speakers!
Alright then, when will the new Transmissionline Speaker be finished?
This question will show that I’m either a genius or I continue to have no understanding of the complexities involved: Could you take much of the complexity out of making a TL speaker by having the last portion of the pipe designed like an enclosed drawer that extends out of the back of the speaker with the port in front? Then, one could slide the drawer in/out (like a trombone) to “tune” speaker to the room and for optimal measurements and sound quality. By making it adjustable you have a built in fudge factor which removes the precision needed in manufacturing, while making it customizable to a variety of situations/rooms.
Such a thing could be built, but it would only be useful as a prototype to experiment with different tunings. In the end, when the ideal tuning is figured out, you would then build a proper one without moving parts (that would start to rattle over time and leak) as the final model. Subs and speakers aren't tuned for rooms, but for the speaker driver operating in the speaker box to get the optimal response.
@@IBuildIt ah well…no Mensa for me….
What about adjusting for altitude and relative humidity?
I think you're onto something...
🎵🎶😉🎶🎵
I use a t-line in my car.
Got a 4” x 100” line which gives an approx tuning of 17Hz.
It’s not that big and is my favorite design.
Ι will never make another speaker with a different bass-loading technique. When done properly it runs circles around other speakers' bass performance. It IS complicated to build and it IS big (especially if you are using 10"-12" woofers like me) but the outcome COMPLETELY justifies the hassle.
The fact that you have correctly placed the apostrophe (so rare!) leads to believe that you have been similarly exacting in your ‘speaker build 🫡
Totally agree, I made a 3” subwoofer that outperforms my store bought 10”
My only problem with them, is the amount of material, it took me almost an entire plank of MDF for one relatively small box. But that also makes it heavy and rigid, keeping away unwanted resonance.
Let's say you have infinite space; maybe an outdoor setup.
Can you just error on the side of being larger than needed and go a whole half wavelength of say, 20Hz (or, 8.5 meters in length)? Does it need to be 1/4 of the resonate frequency?
Seem to recall a channel that plays around with these designs in great detail. Hexibase or something like that. Feel like he is of German decent living in the states. Been a long time since I've paid much attention to the subject.
Write a book on building speakers please
got questions why (at least what ive found )does the mouth of the line have to be on the same face as the speaker. ive built several to this mapping and all had amazing sound range never had to dampenen an of them .
I doesn't have to, but the goal is that front and back wave adds, so you control where they add.
@@pablohrrg8677 They’re going to add the same way no matter where you put them unless the transmission line is not folded. Sound waves are absolutely massive. The size of a box is nothing compared to the wavelength of bass notes.
Maby you can go for a not complex design? A box, then a straight vertical tube out from the top of the box? Chop the tube for needed tuning and use 2 inch mattress foam on the walls of the big tube to rid yourself of resonance. Easiest to go big if you are going to make a TL, the sound and ease of building is night and day, small TL is to hard and as you say simpler with a good ported design. TL line is suppose to have the wave come out the port at the same time as the woofer push out the second turn so both the port and the woofer are in phase as you know. The long waveguide is there to time delay the wave and absorb higher frequencies but you will have a bigger range in bass frequencies on phase with the woofer than a normal bass reflex wich usually just have a small peak where the port and cabinet are tuned, it will also not restrict the woofer more than free air does. a lot of benefits here.
I have built full TL quarter wave for bms12S330 bass at fs 28,6hz and it was more deep bass than i could ask for, the woofer behaved like it played in free air almost so it was important for me to have a good amp to have good control.Class D recommended for driving bass i think. I had to go from almost 3 meters to 1.8m to tune it at speaker fs, used dats v3 to find impedance curve to tune it. I have never heard anything better. Keep in mind i used foam stuffing on the walls of the BIG ports so rid myself of unwanted frequencies. I would not recommend small TL, they are so hard to build. I dont mind a big speaker so i dont have many curves so its much easier to make. The curves brake the sound a lot and lowers db as well. I have been testing and studying this for many years now and it has payed off :)
Thanks for a fine presentation. I agree about the lack of predictability and complexity.
I must confess most of what you talk about on this channel goes way over my head. It still intrigues me though. A long tie ago I looked into chasing down a perfect audio system but gave it up.
What I was curious to know was, are you chasing down listening nirvana or are you just taking a journey to see where it leads?
The setup I have now is as close as I need to get to the idea of the ultimate listening experience, so I'm not necessarily on a quest to find something better. And the concept of "better" can be slippery in that it's completely subjective and affected by a number of factors that can change over time.
But to answer your question more directly, for me it's not really about having this or that piece of gear - it's about me being involved in the making of the gear that gives me the most pleasure.
If you will use acrylic top clearcoat and do a couple coats, and then buff you will get that piano black finish.
I have been building speakers as a hobby for at least 40 years or more. I have experimented with different designs (haven’t tried horn or open baffle yet). In my opinion speakers are the weak link in most systems. They are the weak link because they have the most difficult job, converting an electrical signal to pressure/acoustic waves in air. I believe speaker design always involves compromises and listener taste is a big part of deciding what compromises are acceptable. Also the intended use of the speaker can be a factor.
I have concentrated on home stereo speakers and for me clean accurate sound reproduction has been my goal. I prefer low to moderate listening level and enjoy a range of music genres.
To that end I found tapered quarter wave lines to be the most satisfying. I did not find the basic design and building all that difficult. I used high quality mid base drivers (5” Focal w cone design) and matching 1” tweeters. I used Martin Kings alignment tables and a bit of tweaking to get the sound I wanted. I believe TLs do a great job of taming the woofers reducing mid range distortion. I tuned them to just below the drivers Fs as recommended, experimented with placement of the driver on the baffle and with stuffing. I used a calibrated test mic with decent test software. I was so happy with the result that I haven’t built another speaker yet in about 14 years!
A poor mechanic blames his tools.
They are actually incredibly simple to make, but.. properly and easily made, they are very large.
How tall? The lowest note you need to ever produce cleanly for western music is 27.5hz, or the lowest note on a piano. Below that, it's kind of counter-productive as even drummers will tune their bass drums to 41.2 hz ( same as the lowest Timpani ), though low F ( 43.65 ) is more common so as to stay in tune with other instruments. 27.5hz is 2 meters. Yep. And the gears start turning as that's not home decor friendly. With a proper base and thickness of wood, plus room for the 6-8 inch speaker to be mounted, that's 7.5 feet. For a "not quite full range" but a good compromise design.
And this is indeed the trap. Everyone wants to make one that is smaller, and even going to a half-wave design is still a meter tall and full of acoustical issues unless you really dampen it and do some fine tweaking. Most that I see have the path at 1/4 of a wavelength, and that's now an engineering headache. Simple just turned into a mess of calculations and trial and error, on a cabinet that is (still) huge for a normal speaker. I mean, why build something as large as an old JBL theater speaker that takes a lot more work and sounds about the same - versus just a standard large sealed box? These really only work as "advertised" if the tube has no bends in it.
So it's not good for small speakers? I found this kind of design only through 3D printing of small speakers in the first place.
Thanks for this, it's good food for thought! I built a couple of closed and vented boxed speakers and I'm sort of debating where to go with my next project. I was considering building a transmission line box to fit old CSS fr125s drivers I have laying around. Open baffles would be fun too but I think I lack the space to position them far enough away from the walls to get an optimal result.
So wait then a voigt pipe is same but better then? & much easier to build.
Have you tried a maximally damped sealed woofer? A little EQ to make up the missing low end and your rear wave is gone. Near perfect transient response as well. There was a guy in the 80's in Speaker Builder magazine that was doing well stuffed Transmission lines. Very stuffed by today's standards and he was truly absorbing the rear wave as well. So many ways to skin a cat. Meow. John Cockcroft was his name.
Mark
I would seriously question whether it was all absorbed, but I'm a "100% is actually 100%, not just really, really close to it" type of guy.
Like the infinite baffle setups that are not completely soundproof from the front to back. They get rid of most of the cancellation, but not all. I know that the wall my subs are in is too thin and pretty much see-through for low bass.
But the point was the more used implementation and how it's needlessly complex. A vented speaker will get it done more efficiently.
@@IBuildIt You could double or triple the drywall. Pretty sure in your travels in work you may have done some soundproofing work. CGC has great manuals on this. Yeah you are right 100% is a silly statement. Lets go with most. As for vented. I place them preferably on the bottom, or back. Never on the front. You can hear the phase delayed midrange through the vent on the front. Once you pick it up, you canna unhear it!
Mark
@@KravchenkoAudioPerth Its not just the delay you are hearing. Ported speakers are almost always Tuned to a certain low frequency. This creates an Artificial sounding bass response... well.. actually because it IS artificial. Yes, it allows your speakers to go Lower in frequency... however, that comes at a cost of it distorting the actual music, to do that. Properly designed Sealed speakers, provide natural sounding bass... the way that the bass was meant to be heard. Not tweaked artificially, to be a droning mess.
I think if I did a double layer of 5/8" drywall on top of the 1/2" that's there now I might make a measurable difference and reduce some dips and peaks in the low end response, but I'm not sure that doing it will make a difference I would hear. I already have solid response down to 15Hz that's getting the job done.
Did "soundproof" doors in some locations, which were mostly about making as tight a seal when the door is closed than anything else. Complicated sound seals that are a pain to install and adjust, the doors reduced sound transmission but in no way could they be called sound proof.
Adding EQ to a sealed system will destroy the transient response, especially when you begin turning that volume knob up. it all good at a 1 Watt input but when you put in 20 watts continuous input there is a significant difference in group delay and cone travel.
I have a pair of tdl studio 1 there great.
Learned a ton. Thanks.
Appreciate the honesty, John.
I thought transmission lines were meant to boost the lower bass with the pipe, and trap the mid-bass, mids and highs with some foam in the line.
The bowers and Wilkins nautilus gets close to what John is describing as a transmission line speaker.
Sounds like someone needs to build a S.A.F.E. symmetrical air friction enclosure that I read about in Speaker Builder Magazine in High School in the early 80s.
I agree. I saw no benefits over the ported stuff Ive built. Im so lazy now, I don't think I'd tackle another transmission line set. I've actually become partial to passive radiators for smaller speakers and open baffle stuff for larger speakers. It's fun having so many options though
Not only are they more complex, but I get the impression that even if your back impulse is in phase with the front, it is still time delayed, so you'd always have a little smear going on in the lows. Maybe not much, but I'd know it's there and that would bother me.
A vent design needs more waves to enchant a resonance. 5, may be 10. That’s a bit slower than 1 for the trap
The best way is a double powered amplifier, but these days one driver with Qts about 0.7 is for five with Qts 0.3. So, it’s not easy to find a good one. Typically manufacturers have only few drivers in entire model line of woofers. Like a single 10” model and a single 8-6”
much less than vented.
The delay should be half cycle only.
This is what makes me question the worth of this design (specifically, ending the transmission line with a port. You'd be adding artifacts acoustically. Furthermore, if the port at the far end of the line just abruptly ends, some of that acoustic power is going to reflect back up the line and push on the speaker. I guess all's well if you like how the result sounds but philosophically this isn't a way I'd want to go.
Just like antenna theory! Minimizing VSWR will maximize power delivered to the loadn (air ), by the driver
50 ohm coax connects a 50 ohm source to, you guessed it, a 50 load, The TL is lossless. LOL So inside the source
is 50 ohms. Impedances if you will.
VSWR = reflection back to the driver. Hey ISOBARIC, fake it.
A mirror has a silvered backing, a short to incoming light ( waves ) so . . . the light that gets to your eye is
180 degrees out of phase i.e.: Backward.
A voigt pipe adds a stub ( position of the driver along the pipe) same as an antenna Amigo. The closed end of the pipe
will have really low VSWR, no end of the TL, so to speak, pressure waves go in, but do not come out. really cool, with
little to tune.
I have the same opinion on this. It is much complex and almost no profit.
Why would somebody want to have a 7 foot long tube in a speaker?... as opposed to using a passive radiator setup.
*Guesswork?* Have a look at *AJHorn* which is a calculation program for any loudspeaker, especially Horns and Transmissionlines ( _call it M.King developed to a 'german engineering level'_ :)
It was guesswork 22 years ago when I made that first pair. I wasn't aware of any modelling software that was available back then for a TL design.
People say things are too complex to understand. I say the person trying to explain it sucks. People are proud of their knowledge and they absolutely want you to know it when they are explaining it to you. The bitch of it is this guy proves its the teacher not the student. He dont give a f!?k about impressing you with his knowledge, hes just trying to have some fun and low and behold overcomplicated engineer bulls!?t makes perfect simple sense. Thanks buddy and screw you engineers, were not robots
@2:47 I don't mean to say you're wrong at all and you didn't invent the term of course, but I recognize the term "transmission line" and this explanation is the exact opposite of what a (non-audio) transmission line does. In radio, a transmission line is a specific type of waveguide and, I believe, is or was considered lossless - all energy going in, comes out. Your explanation sounds like it would improve the speaker, but I don't know if it deserves to be called a transmission line by anyone.
I found a Bose transmission based Wave Radio... with the CD changer add on, for like $20 at the thrift shop. I decided to pick it up for testing. It doesnt sound that bad, at low volumes... but mid to high volume levels... and the bass sound droning, artificial, and distorted... just like every Ported speaker, that Ive ever heard. Transmission line speakers are just Glorified ported speakers... and while they might be a little more "Bassy" than a typical port... either way, its still Sh*tty sounding, "artificial sounding" bass.
Properly designed Sealed boxes, and Passive Radiators, are vastly superior in accurate, and excellent.. natural-sounding bass.
Sounds like you haven't heard a properly designed vented speaker. Or more probably, you haven't heard a good vented speaker that you didn't know was a vented speaker, so as not to prejudge it.
@@IBuildIt Ive heard plenty of different speakers... including that POS Bose radio, I got for 20$ at the thrift shop. Are you telling me, that Bose team of Engineers, are not making their Transmission designs properly?!
You know, its not just about the design. Its Physics. You dont get something for nothing. There is always a Price to pay.
Either you have such bad hearing, as not to be able to tell what "Droning" artificial bass sounds like... Or.. you are never going above 5 on your volume knob.
The louder you push ported speakers, the more likely you will hear the "Port Chuffing" distortions, as well as the single-tone artificial sounding bass note (droning). Ports are similar to how a wind based instrument works, they are designed to make a specific bass tone, as the air exits. But that is NOT the natural bass sound, from the actual recording. Its an artificial bass note/sound , and it sounds awful... especially at higher volume levels.
There is also a lot of various distortions, from all of the inner turbulence, and constant vector changes.
There are also times when the Woofer might blow more air out of the speaker, and when it rapidly hits again... there isnt enough equalized air pressure in the box. A sealed speaker, can never have these problems.
It takes less than 5 min of a google search, to find the positives, negatives, and reasons for each speaker type. Might take a little longer, to find the most detailed of responses.
Now heres the thing... Transmission lines were mostly created to allow for a much smaller enclosure, to have decent levels of bass. Thats why Bose started using them in their tiny ECO Trash speaker systems.
If you scale up to much larger speaker boxes, then ports are less of an issue... because most people cant crank an 800 watt speaker... to high / max volume levels. And at those volumes, you are not hearing clarity of music... you are just feeling your chest being kicked in, with each bass blast.
The smaller the speaker box and drivers... the easier it will be to hear port droning and chuffing distortions... at medium volume levels. Again, its not due to bad design. Its merely the Physics of using a Ported design.
Here's some physics: Your sealed speaker doesn't put out enough bass to excite the room modes that a vented speaker will. If you are actually hearing anything that drones or is strong in one frequency (boomy), it's your room and not the speaker.
A well designed ported speaker seamlessly integrates the output from the driver with the output from the port. What it doesn't do is make the listener understand the other acoustic factors involved in listening to sound, and certainly won't do anything at all for any prejudices he has against it based on inaccurate second-hand information and assumptions.
Passive radiators can have at best the same group delay as ported but are typically worse, as the mass of the drone is much higher than the column of air in a port. I tend to much prefer the sound of every ported speaker/sub I've owned with a towel stuffed into the port, but I've never listened to a vented sub tuned properly low, like in the mid 20's at most - those boxes are massive. At those frequencies our ears are much less sensitive to any delay in output, and at higher freqs they behave like a sealed box.
Transmission lines are absolutely different than ported. In a TL the point isn't to boost the output by resonance, instead it's to delay the output from the rear of the driver by 1/4th the wavelength at that tuning frequency so that the rear wave and front wave add together (nearly) instead of canceling eachother out. I would not trust the sound of a wave radio to give you a true picture of what they're capable of. ATC on the other hand...
@@IBuildIt No mention of what kind of Ports there are... ehh? Very dishonest of your reply.
You see, there are two main types of ports. Large Rectangular or Non-Tuned ports... and Funnel shaped TUNED ports.
Tuned ports, are in fact designed to create a specific bass frequency, as air blast out of them. And yes, it is DRONING... because its the same exact Tone/Frequency, every single time.
Non-Tuned ports... are usually much larger in size. Often rectangular. They are far less likely to produce that same sort of droning effect.
The thing is, MOST speakers sold to the masses today, have Tuned ports... and they all sound like total TRASH. Especially compared to a quality sealed speaker. There is No comparison, Period.
This has Nothing to do with the Room. Its the actual design, and intended functionality.
The ECO radicals wanted the massed to use less overall power, and so started making ECO speakers. The Tuned ports were a way for them to get away with using weaker magnet + coil strength woofers... and still getting good "Volume" levels out of them. The trade off, is a speaker that has Artificial bass. Its not what the recordings intended to be heard. And the moment people hear what is Supposed to be heard... they will Rage, just like I did... for missing out on how much better the music does sound... and how they had been ROBBED of such beauty, for many decades of their lives.
I dont come here, as a battle of Egos. I come here, speaking the TRUTHS, from real world experience. From the love of high definition audio. The collecting of many different speakers. And the testing and modifications, in my foolish days, before understanding why none of it actually worked. Until one day, by chance... running into a pair of actual Audiophile level speakers... and INSTANTLY hearing the massive differences in performance / capabilities.
Actually no. A tl does not need to taper. At all. Allso the quarter wave length is.. a minimum length. Basicly you can Just by PVC pipe at a long length that can accomodate the driver , and 2 right angle elbow. You make an U shape , at yay lenght. And there you have it. Thats a proper tl setup.
And your ears will bleed. Its an inferior setup. You can kindof heal some of the extreme shifts if you place the driver 1/3 down the tube. Still your ears will bleed. It sound shite.
Now , there are tl boxes that sound acceptible. Remodell the trapped air in those boxes , along with the dampening effect of the stuffing material. And you will see, that any and all of those boxes are Just actually sealed boxes. Modell it as a sealed box and you will see the correct response .
In reality once you taper the tl , account for its effects and all the heavy dampening , you will be near where an infinite baffle would be. Absorbing as much as possible from the backside of the cone , to get rid of the accoustic short circuit.
To summ thibgs up , the best tl you will ever have is eighter a needlesly complicated sealed box , or a needlessly complicated and inefficient infinite baffle.
There is nothing to be gained. Expect , if you are only interested in 1 single frequency sine wave. Like an organ pipe. And thats all.
TL sound for me artificial...
Like horn speakers just something isn't right
build a ipl transmission line and your change your mind
A good song played on a $10 speaker is better than a crappy song played on a million dollar system.
You think ppl who can afford $Ms systems play “crappy songs” on them…??? lol!
Why does every do the talk but then no demo useless
Ported speaker bass is not from the instrument, it is bass from the box without the real quality of the original recorded instrument
That's like saying the sound a trumpet makes is not from the player.
Ports and transmission lines are not high fidelity. They don't reproduce the recorded bass, they resonate or invent different bass from the out of phase information. Sealed cabinets reproduce the bass. Learn to properly EQ a sealed box and then you have high fidelity. Two woofers in sealed boxes will always be better than one woofer in a huge transmission line box and likely will cost about the same.
Not worth it...
Bullshit. Look for a quadral titan.😅😅. Or T.A. criterion. 😅😅
amogus thumbnail
What are you talking about?
The Trap is, in phase doesn't mean in Time. The Transmission line adds delay to the Signal. It's maybe not audible but it's there.
Sorry you really have no idea what you are talking about. Bass extension from a properly designed TL is measurable. As is the lower fs. You fail to mention Dr A.R. Bailey's 1965 paper on TLs, any of the work of Bub Fried, the variable rates of attenuation which is key to how TLs work. Given your stated design presumptions and goals I'm not surprised this design approach does NOT work for you. However, the fact is does not work for you does NOT mean it does not work. This video should be ignored by any serious speaker designer/builder, instead read the work sited above. More audio BS.
Sorry you didn't listen to what I said in the video. For example, why are you saying that bass extension is measurable from a properly designed TL? Of course it is, if you've designed it to do that.
But it's also measurable from a ported box and will be just as deep. But a ported box is easier to design and build and generally smaller than a TL. You might fool yourself into thinking the bass from a TL is "better", but the fact that very few big manufacturers market a TL is proof that any difference is marginal at best.
Before you tell people to ignore the video, try actually listening to what's being said in it first.
Transmission lines are simply phase inverters.
Back in the 1930's speakers did not produce much bass so Benjamin Olney Invented the "acoustical labyrinth" AKA transmission line enclosure to acoustically get more bass out of the speakers available at that time. A patent was filed in 1934 skip forward to modern times and we have speakers that produce bass and don't need a special complex cabinet. The bass reflex & sealed enclosures dominates the market for a reason. Still people love back loaded and front loaded horn enclosures and transmission line enclosures mainly in the DIY community. The DIY guys like myself usually know the history of audio and dig back into the past and find an interest in a certain design then combine that with the internet and online forums and that's how the interest in things like this grow. But If transmission line speakers did sound a great deal better and were easy to design,build,tune then every manufacture would be making and selling them and that's just not the case because they are very difficult to get right and when you do get them right you will find they are not worth the effort over a ported box.
What about a port designed like a "Tesla Valve"? I wonder how or if it would work.
Might be tough to tune, but it could, in theory, be done.. You would likely need two, however, so you don't end up losing neutral average pressure inside the cabinet. One alone would essentially rectify the pressure wave in one direction
I built a transmission line for my car, tuned to 30hz, single 10" savard woofer, I'm giving it about 1300 watts. I promise you, you've never heard or felt bass like this! It's unbelievable, and a bit ridiculous. It's trying to eat my car lol.