Loudspeakers have we really made that much progress since the 1930s?


Since I have a slight grasp on the history or loudspeaker design. And what is possible with modern. I do wonder if we have really made that much progress. I have access to some of the most modern transducers and design equipment. I also have  large collection of vintage.  I tend to spend the most time listening to my 1930 Shearer horns. For they do most things a good bit better than even the most advanced loudspeakers available. And I am not the only one to think so I have had a good num of designers retailers etc give them a listen. Sure weak points of the past are audible. These designs were meant to cover frequency ranges at the time. So adding a tweeter moves them up to modern performance. To me the tweeter has shown the most advancement in transducers but not so much the rest. Sure things are smaller but they really do not sound close to the Shearer.  http://www.audioheritage.org/html/profiles/lmco/shearer.htm
128x128johnk
I don't think there is such a thing as an "ideal speaker."  You can line up dozens of speakers as candidates for the best current speaker, and you will have a WIDE difference in opinion as to which is the "best" (i.e., the closest to an "ideal").  Part of the problem is that there is so much variability in recording techniques, so much difference in approaches to mastering, huge differences in the acoustics of listening rooms and wide variance from perfection of all of the upstream components (e.g., microphones and how they are used), that even if one attained perfection in certain areas (e.g., zero harmonic and intermodulated distortion), that would just be a tiny part of the picture.  There is no one design that could possibly work in all rooms, never mind consideration of personal taste, types of music, etc. It might well be the case that certain obvious tonal colorations would be favorable, not a deleterious variance from an ideal, given such considerations.  Would the ideal speaker be a omni-directional point source, or something with a narrow, controlled dispersion pattern to reduce room effects?  The answer is-- it depends on the intended application (the differences in listening rooms, intended speaker and listener placement, listener priority on type of "image," etc.  

That said, I certainly agree that modern technology and the accumulated knowledge of past approaches certainly give current designers a MUCH greater range of tools to attain whatever sound they want to achieve than was possible in the past.  I don't disagree with the general proposition that, now more than ever in the past, designers can achieve any given kind of "sound" from speakers.  But, whether they are even so much as trying for a sound that is as good as what has been achieved in the past, at least in certain areas, is debatable.  That is why, depending on listener taste and priorities, you will find fans of different designs from the 1930 on up to current models.  I wish that there were more current makers that are interested in the old-school sound that I like, other than the few makers of ultra expensive and massive systems like those using ALE, Cogent and Goto drivers.
I think this is where the comparison with violins falls apart. In theory there is no ideal violin - they are all different, but in theory there is an ideal speaker. My contention is that with modern methods we can get closer to that ideal.

Which speaker is closest to ideal, and why?
Has an understanding of the physics involved in making a loudspeaker gone anywhere in the past 80 years? Of course it has. Ideal is a goal.

Colorations, resonances, compression, high harmonic and IM distortion, … BAD- not ideal. 

Consideration of driver integration, radiation pattern, power scaling, low distortion, preservation of dynamics, … GOOD- closer to ideal.  

"Computers; have we made any progress since the 1930's?" Duh.
It's a New World.

One size won't fit all, I know.  
But if you are going to build an airplane you should know that you want to fly. 



Wrong. If you are going to build an airplane you should know that you want to crash in style.
[...] I wish that there were more current makers that are interested in the old-school sound that I like, other than the few makers of ultra expensive and massive systems like those using ALE, Cogent and Goto drivers.

Exactly my thought as well; a more widespread merger between old school design/sound and new(er) technology, so to see these older designs (or what's inspired by them) brought back to life with componentry and construction bang up to date, newer developed horn geometries, etc.
Obviously you know the answer, but are having a bit of fun.  Of course sound quality has regressed, if the goal is for the sound to be more reminiscent of real music.  

Speakers are, for the most part, smaller.  But there have been big tradeoffs in efficiency, dynamics, distortion, and ease of the sound.  We are left with poorer speakers that have to work harder and that make larger amps work harder.  That all equals worse sound.  It all makes no sense until you consider the lack of room some folks have and the wife acceptance factor.  Course, most folks could fit larger speakers and they could grow a set so they could negotiate with their wives.  
I carefully wade into this discussion by disclaiming, up front, that I am not very technical when it comes to field of high end audio. However, I'm hooked. I feel like I know "good" sound when I hear it but more importantly I know what sounds "good" to me. I've been into audio my whole life and only in recent years have I had the opportunity to settle for fewer compromises in my system. 

About a a year ago I had the opportunity to purchase a pair of Zellaton Concert speakers. I had heard these speakers set up at a friend's house and fell in love with their open, layered presentation of music. I'm not saying they're the best speakers on the planet, but for my ears and my budget they are pretty close. 

But, I say that to say this: the patent for the Zellaton driver was filed in 1930! I assume that the design is fundamentally the same and I know that each driver is still painstakingly made by hand. While I'm sure that the technology involved with the cabinet design, crossovers, etc. has changed, fundamentally this may support the case for a slower advancement over the years. 

http://www.audioarts.co/zellaton/pdf/patent.pdf
I carefully wade into this discussion by disclaiming, up front, that I am not very technical when it comes to field of high end audio
. 
JHConnor said the above.  

Don't worry, JH, most high end speaker manufacturers are in the same boat as you.  And that's one reason for so little progress.
I personally think technology has Improved for boxed speakers. I had a pair of Linn Isobariks DMS speakers, which were considered up there with the best available back in the 1970's/ 80's. Today I think they are bested by the ELAC cheap as chips range. I do not know what has changed internally with Klipschorns since they were first thought of by Mr Klipsch in the 30's, but I think my 'new' but old Klipshorns sound rather good to my ears.
Great article by Art Dudley in October Stereophile.  He comes down squarely on the side of the best vintage speakers not having been surpassed or even equalled by modern speakers.
One reason for that sal is that Art doesn’t consider "vowel colorations" (as J. Gordon Holt coined them) particularly bothersome, or very high on his list of priorities in a loudspeaker. I couldn’t disagree more. The first good loudspeaker in that regard, it can be argued, was the Quad ESL, which ironically has not been surpassed!
I can remember puzzling over "vowel colorations" when JGH used that term many eons ago.  I wasn't sure what he meant then, and I really don't have any better understanding now.  Can you explain how you understand it?  It must be something I am not tuned into.
One reason for that sal is that Art doesn’t consider "vowel colorations" (as J. Gordon Holt coined them) particularly bothersome, or very high on his list of priorities in a loudspeaker. I couldn’t disagree more. The first good loudspeaker in that regard, it can be argued, was the Quad ESL, which ironically has not been surpassed!


Midrange naturalness and coherency is indeed a prime trait of the Quads, but there's more to overall naturalness here I find than they can achieve. While in some areas they may be unsurpassed, in others they don't even begin to approach much older designs, and this is true not only with the Quads but indeed most of contemporary loudspeaker designs. However, liking both vintage horn-type speakers and the Quad ESL's doesn't seem out of the question in the view of Mr. Dudley (nor mine):

And let me not miss this opportunity to preach: The Altec Valencia and the Quad ESL are polar opposites. The former is all about touch and impact and drama and the ability to present sonic detail in a musically convincing manner. The latter is about timbre and transparency and spatial relationships and presenting musical detail in a sonically convincing manner. Neither is terribly good at what the other does well. Both are superb, both are listenable, both are fun. Both are valid: I have nothing but respect for the person who chooses either, because either speaker is a window that looks out on at least half of what's going on. And that's more than you can say of most loudspeakers.

http://www.stereophile.com/content/listening-125-page-2#pJ5tiOBSqOagiOgK.97

I'd even preach a merger of sorts between the two is possible with currently built vintage-style all-hornspeakers using modern horn geometries, better cross-overs and cabinetry/materials (actually in the latest Stereophile Mr. Dudley hints at an upcoming review of a pair of speakers combining old and new). These may not yet approach the Quads on their core traits, but I'd wager the midrange from a great compression driver fitted to a well-built and -designed modern horn brings other vital qualities to the table like ease, presence and dynamic capabilities, while maintaining virtues that are not incompatible with stats and not least avoiding "vowel colorations." 

Prejudice still sticks to this old segment of speakers (and their contemporary siblings), or as Art goes about it his latest Stereophile article:

The fact is, contemporary audio consumers are even worse than contemporary audio designers when it comes to letting go of the things they think they know, in an effort to know something new about music playback - something new that is, in fact, very old. Modern designers and modern consumers alike must learn to ignore what they already know in the hope of gaining new ground.

[...]

Some - but far from all - vintage loudspeakers also leave out entire swaths of notes and their overtones. Take, for example, another well-loved Altec drive-unit, the 755. Introduced in 1948 by Western Electric, the 6"-diamter 755 was designed primarily to amplify voices, and so ignores frequencies below 70Hz and above 13kHz. What the 755 does it does with virtually perfect ease and impact and coherence and clarity and touch and nuance and physical presence. But listeners who are spoiled by generations of more modern loudspeakers that play notes from 20Hz to 20 kHz - but with virtually none of the 755's ease, impact and coherence - are usually deaf to the older driver's magic, until such a time as they can jettison musty expectations in favor of fresh ones. New expectations and old products go together nicely.

Great article by Art Dudley in October Stereophile. He comes down squarely on the side of the best vintage speakers not having been surpassed or even equalled by modern speakers.
What is meant by 'the best vintage speakers'? old Quads? Hartsfields? AR-1s?
What is meant by ’the best vintage speakers’? old Quads? Hartsfields? AR-1s?
The article is somewhat general in its references, but emphasizes field coil drivers in particular. It also states:
The people who designed the classic products sold by Western Electric, RCA, Siemens, Tannoy, and other golden-age companies weren’t just reshuffling the audio-technology deck in an effort to get last year’s consumers to buy next year’s models; they were using all of their engineering know-how and the best materials at their disposal to achieve a breathtaking level of realism in music and speech reproduction. The companies they inspired -- including Altec, Acoustical Quad, Leak, Neumann, Ortofon, Garrard, EMT, Klipsch, Jensen and Marantz -- strove to do pretty much the same.

The result is that, **in certain aspects of their performance,** [emphasis added by me, Al] many audio products made in the 1930s through the 1960s outperform virtually everything made since that time, often by generous margins.
A well done and thought-provoking article IMO, regardless of which side of the issue one may be on. And as Phusis alluded to, it concludes with an intriguing reference to a "currently manufactured loudspeaker that has one foot planted firmly in the world of vintage audio and the other in the realm of modern design and manufacturing. It’s a remarkable product ... [to be] described in detail next month."

One clarification to what Mr. Dudley had to say, as quoted above in the post by Phusis: I’m pretty certain that all of the Western Electric and Altec 755 variants were 8 inch drivers, not 6 inch. 6 inches was probably the diameter of the cone, less surround.

Best regards,
-- Al

I am in agreement with most of what Art Dudley says about vintage 1930-60's gear, generally speaking, but, the specific examples he mentioned in the excerpts quoted above, are not what I would be setting out as examples.  The Quad? Yes, a terrific sounding speaker if one can accept its volume limitations, requirement to be seated in a very narrow listening window, low image height, etc.  But the Altec Valencia?  If one is limited in experiencing horns to just such speakers, it is easy to see why someone would say that they hate horn colorations.  As for the 755, that is certainly and "interesting" speaker--very clear, dynamic and exciting, but, it is extremely colored and quite limited to the kind of music that sounds good through it (pop vocals, jazz).  If one insists on a single driver vintage system, the 756 is far better sounding to me, although even rarer and more expensive. 

Given the thread of Art Dudley's articles over the years, I do wonder if he has had that much exposure to some of the real gems of the past, such as the 555 field-coil compression driver on a 15A horn, or Jensen M-10 or M-18 field-coil cone drivers, or Western Electric 713a,b,c or IPC compression drivers, or Yoshimura Labs compression drivers.  There is also the monster Shearer system that the original poster mentioned that is certainly a contender for best of vintage gear.

I read somewhere that Art Dudley is planning to review the Auditorium 23 system, which is a modern system that utilizes Line Magnetic knock-offs of the Western Electric 555 compression driver, 22A horn and 597 tweeter.  That should be quite interesting.  I have not heard this system myself; it looks terrific in pictures.  My only issue is that those I have talked to that have heard the Line Magnetic replicas of the Western Electric field coils say that they sound decent, but, nowhere close to what the real drivers can do.  It would be interesting to see if Art Dudley has, as a personal reference, experience with the real deal, without which, it would be hard to frame his comments in any kind of meaningful context--where does the system stand compared to the original masters?  That is the burning question.

I also run systems with combinations of vintage and modern. Running on modern amplification and with modern sources. A upgraded 30-60s design can easily compete with modern efforts and in many cases are the better option.
I revive this thread since my findings and feelings on this issue haven't changed and I have noticed a increase in interest in horns more offering horn designs and more media attention. Much of whats offered are re-worked vintage designs some even using old drivers or replicas of such. I see reviewers exploring vintage horns comparing them to modern loudspeaker designs.  So it does seem like we made limited progress and are re exploring the past for design ideas for future horn systems.
Yes, this thread is very interesting and well worth reviving.  Since the last posts here, I am now running a 3-way vintage speaker built around a YL Acoustic (Yoshimura Labs) compression driver and horn.  To my ears, it provides a very natural, warm, dynamic sound.

Johnk, I noticed you don't have an AudioGon system page with details of your setup.  Any chance we can twist your arm and get you to post a description and perhaps some photos?

Sal,

Those are really nice photos of your amazing system.  I find YL drivers and horns to be fantastic sounding--very dynamic, yet totally relaxed and natural sounding.  The drivers with the diaphragms that are duplicates of the WE 555 can, with the right horn, go incredibly low. 

Deja Vu is getting in some G.I.P. drivers that might be interesting.  I am particularly interested in the field coil woofers that are replicas of Jensen/ERPI/WE woofers.  I think they might work well in an open baffle system, although I don't have room for the giant systems I've seen utilizing such drivers in an open baffle.  Perhaps, a G.I.P. 15" field coil woofer with a G.I.P. replica 597 field coil tweeter for a killer 2-way system?

I thought that for the horn to go very low it had to be the size of a house. Was I wrong?
I looked up the YL and saw that both of you guys were discussing this on the Hoffman forum. Someone else on one of the fora had mentioned Deja Vu recently, in connection with recreating old WE horns. 
I've been using a commercial horn system (Avantgarde Duo) for 11 years and love their strengths- the "bespoke" vintage approach fascinates me- if it could sound coherent between the bass and mids, which has always been the challenge for me. I had also seen anecdotal reports on the GIP but have not heard any of these recreations. It sounds like the YL is actually vintage recreation which is appealing if it isn't as costly as some of the WE or other early stuff.
I just got my Quad based system restored, and as noted above, within their limitations, using restored Quad IIs with real GEC glass, they are breathtaking to listen to. 
I guess on both systems, the horns (with Lamm SETs) and the Quad-Quad system, i live with their shortcomings to revel in their strengths. I wouldn't mind assembling an all out horn system, but for space and cost. 
Sidenote: sorry if I mentioned this before, but the one thing I like about the Avantgarde design is that the mid horn is run directly from the amp with no crossover. It is very transparent, and with an even better driver, this arrangement would make much sense to me-- so much is in the midrange and if you can avoid the crossover there, it would seem to allow optimal performance. The issue then becomes making the bass (and treble) cohere. 

At home I run 3-4 systems while I do run modern loudspeakers many advanced for my own enjoyment I run horn systems. Most are combinations of old and new but when I can I try  to experience the best of vintage stock. If I have stock I mod so I can reverse and return to such. My office mains are community leviathan mid bass horns with 4- 515b woofers modified TAD 2001 on a giant community 10 cell multicell horn. I use costly passive networks but otherwise this could have been set up in 1970s. I do run a massive modern sub built to look like a old RCA MI booth monitor just much larger. My main system is 2-RCA MI shearer horns Viva amp I again run audiophile passive and use with fostex t500amk2 or faital driver on small 15 cell. 3rd systems 1920s RCA W bin with RCA radial horns and drivers and faital on matching tweeter horn again modern networks I use this at times with a massive front loaded bass horn. My garage system is a giant 1920s pair of RCA horns I used the RCA drivers at times but enjoy swapping in modern drivers my RCA drivers are  95 years old and I like to keep them functioning. I am all over social media you can google search if you want far too many pics.
inna house sized no shed sized yes if you want sub bass. Still if you look at how modern loudspeakers generate bass a large horn hitting 45hz without roll off at incredibly low distortion levels pretty much trumps the  high excursion, massive power, low bass by resonance approach and its  high distortion levels, limited dynamic range and associated  fatigue factors. The horns weakness maybe in coloration but at the listening levels homes use these massive designs are just coasting along.           
Rice and Kellogg, Harry Olson,John Hilliard, John Blackburn much of whats available today they invented in the 1920s-30s thus why I started the thread how much progress has really been made when the best of today is lucky to be as good as the best at that time and is most likely a evolution of these 1930s designers work.
LarryI, thanks for the nice comments.  The last time I was at the DejaVu store, I heard a really nice sounding setup that used the YL 5500 in a big horn with a 200 Hz crossover and 15" Goodmans woofers in open baffle.  It had a Jensen RP-302 crossing in at 10K.  Voices were very realistic over these speakers.
My speakers at home are made by Classic Audio Loudspeakers. I may have mentioned this on this thread a long time ago.

They differ from vintage stuff in several ways. First, the midrange driver, which employs a 3" compression driver coupled to a machined maple horn. is different in that the diaphragm is built of beryllium, but using a Kapton surround rather than a metal surround. This extends the bandwidth of the driver and prevents breakups- the first being at 35KHz. It is also field-coil powered. The horn is a new design and does not have the typical peak at the bottom end of the pass band which is caused by an error in design- common in a lot of vintage midrange horns.

So as a result is it faster, smoother and more detailed than vintage midrange horns. People often comment that is sounds like an ESL, but of course its a lot easier to drive and has greater dynamic range.

The woofers are a pair of 15" TAD drivers with Alnico magnets. One of the woofers has a free air resonance at 22Hz. Both drivers can handle 150 watts no worries. They are in series so the speaker can handle 300 watts. I don't think any of the vintage stuff can do that. In addition, the Theil/Small parameters were not understood until the mid 1960s or so- so port openings were a bit of a guess in the vintage stuff. These days computer modeling has the ports spot-on.

The crossovers are 6db with Mundorf silver and gold foil caps. Those parts didn't exist in the vintage days.

The result is overall the speaker is faster, more transparent and has more deep bass than vintage designs (with a sacrifice of some efficiency since the speaker is bass reflex rather than horn loaded).

I like the vintage stuff and if priced right can be nice to play with. But they don't hold up to the new stuff.
Atmasphere Capacitors have existed in some form since the 1740s silver and gold are not advancements just evolution of early design. Your TAD drivers all based on early 1920s designs,the horn of the CAR is just a evolution of a 1940s design. OTL amplifier is from the 1950s sure you improved but you didn't create invent. Thus my point about real progress progress in orignal design and thoughts. This to me seems missing today.

Perhaps there cannot be any more breakthroughs for a very long time, who knows? When all you really want to do is sell sell sell, you will create nothing except more ways to sell.
One does have to take a financial risk when working with or bringing out new innovations could be a bit of corporate repression of design in favor of safe bets thus more profit? Could be that reproduction of sound for human use can only be effectively generated by a limited num of combinations thus replication? Maybe humanity copies and improves more than invents and innovates? Maybe my perceived biases do not allow me to see or hear all the massive innovations in audio reproduction?  
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Well, all these questions go far beyond audio. Perhaps, nothing is ever new under the sun. I view speakers making as a fine art, unlike everything else in a chain, that is just art.
John, I think you stress the emotional component, which in my mind is also the most important. I heard a few fine instruments that didn't give that no matter who played them, and I heard other instruments that sounded a lot like the vintage design speakers you are talking about. And I heard two that got everything right. Custom acoustic guitars. I can't really play a guitar but I can strike a few accords. Wow, that was quite a sound. The other even much better guitar was played by Paco de Lucia - custom Conde Hermanos.
Something is being lost in modern sound reproduction, I think, and it cannot be compensated by anything.
kosst_amojan -Zonda is a evolution of whats considered the 1st sports car 1914 Vauxhall.  Zonda did not create the idea of a sporting car it evolved its design based on the many many sports cars before it. What are Zondas original  advancements to automobile  tech? Its just near the pinnacle of a very advanced vintage technology.
inna we do rely  much on computers for design might be why so much made today seems to not be-able to give soul or life to music and that we keep mining the past a time when humans designed for ideas horn speakers, tubes, LPs, tape all still being made why if modern tech is so advanced? are we looking for something that is not available otherwise?    If I sim loudspeaker designs I can hear how wrong some of the sims can be in reality. I trust what  I am hearing thus make empirical changes to design to get what I want out of it not what works well within the confines of a limited software program.  Might be others put more trust into the computer end and less on the human and with art like music that might be a issue. After all you are trying to trick human senses into hearing actual music,sound-stage and feeling any emotions the music generates. 
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John, I think the more people rely on computers the more they will become like computers. And I don't want to see it let alone participate.

I like the sound of Classic Audio speakers.  They do represent a successful utilization of old school technology (field coil magnets) and modern materials and technology.  But, whether they are superior to old systems or modern systems using old drivers, that, is purely a subjective call.  I personally do not think they sound better than a well done implementation of old drivers.  It is probably a matter of voicing; I find them to be a bit too lean and bright and brittle sounding as compared to some of the systems using old drivers that I really like.  Still, the Classic Audio systems are great sounding and  do outperform vintage systems in terms of bass impact and depth and ability to play loudly.  I happen to prize very highly other qualities that some vintage drivers deliver--ability to sound very dynamic and lively at low volume, delivery of a really relaxed, smooth sound while remaining dynamic and clear sounding. 

It is also a BIG deal to me that vintage drivers are VERY efficient.  My favored amps happen to be quite low in power output.

koksst_amojan I cant answer a non sequitur. Threads about progress in loudspeaker design since the 1930s and maybe a lack of innovation or similarity of design in such things. 

larryi, Glad CAR exists and its a great option but there product in no way obsoletes vintage and I find it a bit funny that CAR was used as a example of advanced modern design since much of what they offer is cool modernized vintage design. And that would support my orignal assumption of how little progress has been made since the 1930s.
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And we are still infinitely far from fully mastering the fire, whatever this means.
I thought we got past the limitations of horns about 35 years ago  - once transistor amplifiers became of good quality and allowed more power to be widely available.

Horns are simply not the best in terms of accuracy but they do deliver exceptional SPL for little power - great for live music sound reinforcement.
kosst agree that we may just be copying much of what came before with slight improvements and innovations with time and agree this could go as far back as fires discovery or farther. The reason that I point to the 1930s is that most of what we use today in loudspeakers was created in a  early spurt of innovation driven by early theater and telephone technology.. Might be  the telephones popularity and theaters going from silent to talkies that stimulated so much innovation but also at the time the largest corporations in the world put massive resources into creating it. This new technology also attracted some of the great minds at the time. Today audio technology design is of extremely low priority and is mostly done digitally. And is no longer attracting the best and brightest. I understand that being engaged by music is a fading activity and I really shouldn't be surprised by the lack of innovation and small time nature of companies that market such. We are a niche. 
shadorne    Horns have lower distortion than conventional drivers faster transient response than conventional drivers,are easier for amplifiers to drive can produce higher SPL than conventional drivers also exhibit greater dynamic range. and radiation pattern control. Consider much of the music that audiophiles collect was mastered on Altec, TAD, RCA and other horn systems. And many modern studios are still using horn monitors.
Your TAD drivers all based on early 1920s designs,the horn of the CAR is just a evolution of a 1940s design. OTL amplifier is from the 1950s sure you improved but you didn't create invent.
OTLs: yes I invented my circuit myself. I didn't know about other OTLs at the time. I got two patents- more than anyone else in the field. More on the way.

While the drivers might be loosely based on the prior art, the fact is nothing like them existed or could have existed as early as the dates above. The simple fact is that computer technology has made speakers better- including horn designs.

Horns are simply not the best in terms of accuracy but they do deliver exceptional SPL for little power - great for live music sound reinforcement.
Actually a good horn can be quite accurate- if you think about it, the driver does not have to have a lot of excursion to do its job. If its properly designed, it can be lower distortion as a result. Since the electronics don't have to work as hard to drive the speaker, its also possible for them to be lower distortion too.
Speaker evolution these last rather many decades roughly seems to have been more about refining a concept born by Edgar M. Villchur when he brought forth the AR-1's in the 50's. Few would or should really contest the perhaps most notable feature here being the catering to a domestic demand (rather than the search for and proclamation of a more real sound), or certainly seeing a product's more widespread use through the limitation of size (made possible with the advent of the more powerful transistor amps to counter another limitation: sensitivity). Within this concept I can see some progress through the years (followed not least by an uptick in price), but in the bigger scheme of things the older, much larger and much more sensitive (horn-)speakers, though limited in the frequency extremes, to my ears are still substantially in the lead (particularly combined with low-wattage, single-ended valve amps) when it comes to an effortless, dynamic and encompassing live/emotional imprinting. From this perspective it could be argued that over a longer timeline speaker evolution has really seen a decline, in some vital aspects at least, in not re-accepting the need for sheer size and high sensitivity of speakers. From my chair we'd need to re-visit these older horn designs more frequently, and build/design further on from them to truly make progress. 
Atmasphere -Look at 1920s WE 555- 1930s 596A compression driver your saying TADs design isn't based on these early compression drivers?  Whats so different besides materials used?                                   I never knew you invented OTL I assumed it was created in 1954 by Mr Cecil Hall for EV.