Why did AR do the LST?

[DavidR]

I tought that Willchur left the AR in 1967 and sold it toTeledyne.

If Teledyne years do mean something else...please explain as I do not uderstand.

Best Regards

Kimmo

My bad.

Yes, 1967 NOT 76.

[soundminded]

IMO LST was designed to overcome some problems with AR3a. LST used the same drivers as AR3a but power handling capacity in the midrange and tweeters was quadrupled. This was before the era of AR invented ferrofluid cooling. Dispersion was increased dramatically. The AR 3a/AR2ax tweeter has the second best dispersion of any tweeter I know if, only being beaten out by Allison's own interesting design he produced for speakers under his own brand name. Allison was a great believer in wide dispersion. IMO he got it right and everyone else got it wrong. The way real musical instruments propagate sound into a room is much closer to LST than to any other speaker. The autotransformer in LST and the design of AR 10pi were at a time when graphic equalizers were not available to consumers. Now that they are, those level controls can be bypassed and the system spectral balance can be adjusted inexpensively by better means. As an owner of AR9s IMO in some ways LST was the best speaker AR ever made. In others it was AR9. Too bad there isn't one speaker that combines the virtues of both.

[newandold]

IMO LST was designed to overcome some problems with AR3a. LST used the same drivers as AR3a but power handling capacity in the midrange and tweeters was quadrupled. This was before the era of AR invented ferrofluid cooling. Dispersion was increased dramatically. The AR 3a/AR2ax tweeter has the second best dispersion of any tweeter I know if, only being beaten out by Allison's own interesting design he produced for speakers under his own brand name. Allison was a great believer in wide dispersion. IMO he got it right and everyone else got it wrong. The way real musical instruments propagate sound into a room is much closer to LST than to any other speaker. The autotransformer in LST and the design of AR 10pi were at a time when graphic equalizers were not available to consumers. Now that they are, those level controls can be bypassed and the system spectral balance can be adjusted inexpensively by better means. As an owner of AR9s IMO in some ways LST was the best speaker AR ever made. In others it was AR9. Too bad there isn't one speaker that combines the virtues of both.

That's interesting about the origin of ferrofluid cooling.

Allison uses ferrofluid in the two way systems of the 1970's (tweeters only) that included the models one thru nine.

The three ways such as the Allison One used silicone grease in the tweeters and ferrofluid in the midrange units.

I had the AR 2ax for a number of years. The highs were excellent, but I was hampered by those infamous pots that became intermittent on a regular basis.

Could not agree more about Roy Allison

Bill

[iso]

Allison was a great believer in wide dispersion. IMO he got it right and everyone else got it wrong. The way real musical instruments propagate sound into a room is much closer to LST than to any other speaker.

There are pros and cons in this way of thinking... if we play records made in anechoic chamber without any reverbation, this kind of thinking will create real sound field in the room. But if the recording does include soundfield of its own, reverbation due wide dispersion will create another sound field over the original one. So speaker with only direct radiating sound would be the best solution and speaker with controlled dispersion would be the next best thing...so AR9 may be able to create more realistic soundstage.

But anyway it seems that AR-LST and AR9 were the peaks of Teledyne years.. Villchur must have been aware that market share of AR can only drop from mid 60´s figures, as market share was actually too good to be true. Price he got from Teledyne must have been at least fair... but as market share dropped during Teledyne years, dividends that Teledyne got from invetment may have been less than expected. Unless Teledyne also figured that market share would drop during years to come.

So... was Teledyne good or bad guy?

Best Regards

Kimmo

[frankmarsi]

There are pros and cons in this way of thinking... if we play records made in anechoic chamber without any reverbation, this kind of thinking will create real sound field in the room. But if the recording does include soundfield of its own, reverbation due wide dispersion will create another sound field over the original one. So speaker with only direct radiating sound would be the best solution and speaker with controlled dispersion would be the next best thing...so AR9 may be able to create more realistic soundstage.

But anyway it seems that AR-LST and AR9 were the peaks of Teledyne years.. Villchur must have been aware that market share of AR can only drop from mid 60´s figures, as market share was actually too good to be true. Price he got from Teledyne must have been at least fair... but as market share dropped during Teledyne years, dividends that Teledyne got from invetment may have been less than expected. Unless Teledyne also figured that market share would drop during years to come.

So... was Teledyne good or bad guy?

Best Regards

Kimmo

"Charlie Says. "Love My Good and Plenty"

11-14-15

FM says:

soundminded, on 14 Nov 2015 - 11:07 AM, said:

Allison was a great believer in wide dispersion. IMO he got it right and everyone else got it wrong. The way real musical instruments propagate sound into a room is much closer to LST than to any other speaker.

Charlie Says. "Love My Good and Plenty"

11-14-15

FM says:

I don’t know anymore, information over-load I guess. Perhaps it’s mind travel of the third kind? But, to a large degree, my mind and body are still vital and strong enough.

But, for me, I never question anything “soundminded’ or “SteveF” ever say. They both are some of this site’s most qualified here, regarding their level of experience and even-handed- ness of opinion. “Soundminded” on a few occasions has even ‘set-me-straight’ on certain issues, for which I publically thanked him for!

Many of the original guys who I may have been slightly amused back in 2004 to say 2005 with my silliness about using an AR 12” speaker basket as a head-dress while running through the west side streets of New York City don’t seem to frequent these pages any longer for reasons I can’t speak of.

But, with 29 posts and 441 views on this post, the question beckons, who has, owns or really knows the sound and glorious satisfaction of hearing/using LSTs?

And not to be a stick in the mud while defecating and telling you it’s an earthquake, to me, “soundminded” is usually, just that, sound minded with his responses and point of view. While SteveF is a great AR soldier and a worthy speaker (human that is) on all accounts!

To my simple mind, ‘soundstage’ is heightened by the LST because of it’s design, the midrange spreads out and paints a realistic picture of the ‘stage’, whereas an almost direct sound field like that created by the AR-9 may lesson this affect by radiating sound directly at you. Let us think about listening to a classical orchestra, cause there’s where the answer lies in terms of taking it all in. In an auditorium, sound is reflected and comes at you from many directions, creating the whole picture of musical enjoyment.

Speaking with little experience of their use because, I only used my AR-9s for a few months as I wasn’t that pleased comparatively speaking because their sound was radiating directly at me, although their bass did give some sense of depth of the stage.

When, I quickly returned to the AR-LST’s, I was once again greeted by a depth and expanse of their well known and heralded deep ‘sound-stage’. And in consideration of the Allison Ones, Roy Allison once again was proving his point.

On a similar note, the much disliked Bose top of the line speakers attempted to give the depth of a realistic ‘sound-stage’ but, he-he, apparently failed for all intents.

Am I getting lost in semantics here or is everyone else?

For those as old or older than me, might remember the ‘Sweet-Sixteen’ design array from way back, I think that too tried to portray a certain measure of a realistic’ ‘sound-stage? What about those “Empire” Grenader’s what ever they were called and a host of others. Look at what “Bob Carver” did with his bigger speakers back in the day.

Mental note: I must check out his designs some day and I see what he was attempting and, probably succeeding at.

Folks can even do it with multiple sets of tweeters and mids like the “Micro-Statics”. By facing one set towards the listener and the other set facing a reflective wall.

Every time I sit and listen (very-often), to my set-up I realize the design goals and the accomplishment of the LST speakers. These speakers can’t help themselves at creating a huge sound-field whilst allowing for much depth of the ‘stage’ because their side mounted mid-range drivers succeed with how the enclosure was designed and allows sound to be spread over a larger field, this, by being reflective or otherwise. At the same time, their bass is almost non-directional, but that’s how bass is.

Lately I’ve really gotten into a set of new phono-cartridges and the lesson has been taught to me once more. It has become very clear to me, the better the cartridge, the deeper and more realistic the ‘sound-stage’ is, henceforth more realism to sum it up. And for those of you using upper tier AR speakers, but not with clean and quality vinyl play-back, but using 'low to mid-level' CD decks instead, shame on you.

So, I’m having a great time enjoying a more defined and realistic listening experience because the combined affect of the newer cartridges and the LSTs are really working well together to render that level of realism by deepening and spreading the focus of realistic sound across the sound field, more depth, more hall-affect echo, and more detail in all the correct measures.

fm

[iso]

To my simple mind, ‘soundstage’ is heightened by the LST because of it’s design, the midrange spreads out and paints a realistic picture of the ‘stage’, whereas an almost direct sound field like that created by the AR-9 may lesson this affect by radiating sound directly at you. Let us think about listening to a classical orchestra, cause there’s where the answer lies in terms of taking it all in. In an auditorium, sound is reflected and comes at you from many directions, creating the whole picture of musical enjoyment.

Lately I’ve really gotten into a set of new phono-cartridges and the lesson has been taught to me once more. It has become very clear to me, the better the cartridge, the deeper and more realistic the ‘sound-stage’ is, henceforth more realism to sum it up. And for those of you using upper tier AR speakers, but not with clean and quality vinyl play-back, but using 'low to mid-level' CD decks instead, shame on you.

Dear Frank

That is my point. I have never heard AR-LST but I have owned pair of AR9 in early 80´s for couple of years. So.. I can say nothing about sound quality of AR-LST and very litlle about AR9, as too many years have passed since early 80´s. But... if the goal of High Fidelity is to reproduce soundfield or stereoimage of original recording, then omnidirectioanal or wide dispersion concept is not way to go... widest possible dispersion will create "widest" possible soundfield of the room, as there is good ammount of reflected sound energy involved. This soundfield is not truthfull to recorded soundfield as it is created in the listening position and it will change when sytem is moved to other room. This may sound good, realistic or whatever you like... but stereoimage and soundfield can not be trutfull to the original, due to the fact that reflections in the room create soundfield of the room. When this new soundfield is "added" to the original soundfield, soundfield that we will hear is not the orginal and it is not the soundfield of the room either.

I fell in love in turtables again too... they are simply great, even I do fancy vintage ones.

Best Regards

Kimmo

[der]

As far as I'm concerned, reproducing an original sound field would only matter with live recordings. Everything else would seem to be at the discretion of the recording engineer. (studio) I have a few live jazz albums recorded at clubs and with some of them, at least, the re-creation of the room appears uncanny.

Of course, you would have needed to be present at the time of the recording to truly know that.

der

[frankmarsi]

https://www.google.com/?gws_rd=ssl#q=define+%27sound+stage%27

11-15-15

This could help us all.

Long after regularly reading the two biggest magazines since 1988 printed in this country about Hi-Fi along with the big three, Stereo-Review, High-Fidelity, and Audio magazine since 1966 and earlier, this link speaks more specifically about the definition of ‘sound-stage’. There are many other opinions besides mine of course, so loook up those opinions up on the net for yourself.

However, from what I’ve understood from the last two magazines in this country and with intense listening to speakers since I was a kid long before I, in 1972 bought my first AR-3as, but heard AR-4 speakers in my dentist’s office in 1962.

I feel ‘sound-stage’ may mean more than what is commonly understood in this thread.

From what I’ve learned, it means the ‘depth’ and ‘location’ of sound and of each musical instrument’s location, along with its ‘overtones’, ‘harmonics’ and perceived ‘echo’.

That, in of itself is speaking of many things.

When I listen to a well recorded, well ‘mike-ed’, and a quality pressing of classical music on a vinyl record, I’m able to hear an oboe, flute, bassoon, strings, drums and any other instruments precisely where it would normally be located in a classical orchestra set-up, speaking from my experiences solely of such, of course.

Higher quality recordings and higher quality ‘play-back’ components seemingly are able to help better locate where each instrument is placed upon this ‘sound-stage’.

Solo instruments are typically from the center-stage whereas a second violin may show itself behind the first-violins, violas, double basses and so forth.

A ‘canned’ or over produced rock/pop recording and such have the luxury to hand pick the location according to the recording artist’s desire or recording engineer’s decision while being in a studio.

Better quality equipment allows, especially with ‘classical music’, the listener to hear these subtle differences of ‘location’ of each instrument and its positioning in the rendered play-back. When the perceptions and locations of each instrument is precisely aurally located correctly and when the whole ‘sha-bang’ is generally accepted as correct in these terms, music is making us feel good.

However, with classical music, things maybe more accurate, in terms of instrument locations afforded by the ‘AR-LST’ speakers inherent and because of its ‘designed-in’ sound-quality. You can thank those guys who designed these wonderful LST speakers.

Speaking for myself, I’ve always been torn between live classical music in person compared to vinyl records and or studio-produced music.

I’ve been a ‘music-head’ from the 1960s and earlier than that but, always relied upon my classical/opera listening sessions on 78 rpm records and fifties and sixties LP records given/played for me by my oldest sister Angelina and my father Frank Sr.

They’re both gone now, so you’re stuck with me, here and now!

SteveF’s post I trust, was implying this knowledge and the understanding of the AR-LST’s ability to portray the orchestra’s/ band sound location more realistically by virtue of its design engineering and utmost portrayal of music rendering quality.

This may be why a couple of years ago when one of those two or both magazines ran articles about and including the AR-3a

and LST speakers as being some of the original best speakers to afford this quality of sound reproduction to the public. Ever!

Forgive me as, I can veer off too far sometimes because I become so excited in my own way, about how great I believe with all of these considerations in ‘my’ mind how my system sounds, to me. I have a strong feeling any who have delved into music and reproducing equipment as I have will take me seriously as necessary to understand! I trust many others have gone and done more than I.

Yes, the old vintage AR-LST speaker might be the pinnacle of such realistic quality of recorded music ‘transducers’ in the last 50 plus years and more!

“Excuse me, while I kiss the sky”

Sincerely, Frank

fm

[Steve F]

Frank--thanks very much for the kind words.

A few additional LST thoughts:

That transformer was a very well thought out design. It was not a “level control,” in the way the pots were on regular bookshelf AR speakers.

The LST control was designed to give the speaker a set of six repeatable, knowable spectral balance curves that would be precisely available to the recording engineer (nod, nod, wink, wink) at any time. The autotransformer control kept the output level of the midranges constant, so the apparent loudness of the speaker remained the same, regardless of switch position. That would be important during the monitoring process, since, as we all know, a “louder” speaker tends to sound better.

Each successive position of the switch raised the woofer level by 1dB and lowered the tweeter level by 1dB, rotating around a fixed (constant loudness) midrange level.

Switch pos 1 had the tweeters 1dB up (over the mids) and the woof 1dB down (to the mids)

Switch 2 was “flat.”

Switch 3-6, the woofer level is raised by 1dB and the tweeters are cut by 1dB for each succeeding position.

AR said that positions 5 and 6 were roughly equivalent to an AR-3a with its controls set to “Normal,” but that was really pretty useless, irrelevant info, since, 1) the radiation patterns of the two speakers was so wildly different and 2) no one—no one—ever used the 3a with its level controls set to “Normal.”

The LST didn’t really need a graphic EQ since its far-field power response was so smooth and the switch provided those six precise spectral profiles. But just for the record, in the early-mid ‘70’s there was an affordable 10-band/octave 2-channel equalizer available for home use, the Soundcraftsman 2012A.

Interesting side note: When AR was doing their prelim work for the 1976 Neil Grover drumset live vs. recorded demos, they tried the LST along with the 10Pi. The 10Pi beat it easily for purposes of replicating Grover’s drumset sound. There was too much audibly-destructive interference between the LST’s multiple mids and tweeters, and it didn’t do anywhere near as good a job as the single-driver-per-band-all-forward-facing 10Pi. I offer that little tidbit without any implied or explicit comment as to the LST’s superiority or inferiority at reproducing an already-recorded soundfield, vs. the 10Pi.

Steve F.

[owlsplace]

Frank--thanks very much for the kind words.

.....

The LST didn’t really need a graphic EQ since its far-field power response was so smooth and the switch provided those six precise spectral profiles. But just for the record, in the early-mid ‘70’s there was an affordable 10-band/octave 2-channel equalizer available for home use, the Soundcraftsman 2012A.

Interesting side note: When AR was doing their prelim work for the 1976 Neil Grover drumset live vs. recorded demos, they tried the LST along with the 10Pi. The 10Pi beat it easily for purposes of replicating Grover’s drumset sound. There was too much audibly-destructive interference between the LST’s multiple mids and tweeters, and it didn’t do anywhere near as good a job as the single-driver-per-band-all-forward-facing 10Pi. I offer that little tidbit without any implied or explicit comment as to the LST’s superiority or inferiority at reproducing an already-recorded soundfield, vs. the 10Pi.

Steve F.

Yep, used the Soundcraftsman EQ with my AR-5's -- long ago and far away

Roger

[rl1856]

The AR5 was an excellent speaker; much better than the 2ax and in some ways better -in room- than the 3a. The cost of the 5 was too close to that of the 3a, while most consumers could not discern a difference between the 5 and 2ax. Their loss.

Why was the LST created ? Criticism of the 3a design and changes in the marketplace. The 3a had a stepped driver response with the response of the midrange roughly 3db lower than the woofer response, and the tweeter response an additional 3db lower (and -6db relative to the woofer). However the 3a was designed to replicate the listening perspective of a 10-15th row seat at a classical concert. Translated to a domestic room, that meant far field positioning. AR recommended a listening distance of 12-15 foot from the plane of the speakers. Excellent dispersion characteristics of the AR dome drivers meant that the sound reaching a listener 12-15 feet away would be a mix of direct and reverberant content. Thus the overall balance in situ would seem to be better than what measurements would imply. Consumers agreed with and the AR approach and by the late 1960's AR had a 60% market share.

What happened?

Critics were persistent in noting the stepped measurement response of AR speakers. The composition of the market changed, with younger buyers who preferred pop music gradually replacing older buyers who preferred Classical and Jazz. Pop buyers had a preference for flat response, like what they head at a concert. Competing speaker designs delivered flatter FR, with AR like bass and could play rock music at appropriate levels. Dynaco A25, Advent, EPI, Boston Acoustics, and of course the JBL 100.

The inherent flaw of AR dome speaker design was fragility. The drivers could not handle large amounts of power nor could they produce loud SPL at the listening position.

AR wanted to produce a speaker that addressed critics and the needs of a changing market. That meant a flat in room response and loud in room SPL. The solution was multiple dome drivers arranged across a 120 degree plane. Measured response was indeed flat in room (+/- 3db 50hz-15khz), with the ability to absorb prodigious amounts of power, and play at 105db+ for extended periods of time. However this solution brought additional problems. Audible phase distortion between the multiple dome drivers and the need for a very complex auto former driven crossover. In reality the LST was not suitable for a wide range of listening rooms.

The LST led directly to the AR9, which solved many of the problems of the LST. Single forward facing dome drivers eliminated phase distortion. Ferofluid (first used in the AR 10pi and AR 11) significantly raised the power handling ability of the dome drivers. The result was flat in rooms response, loud SPL and a design that was more room friendly. Like the 3a, and LST, the 9 advanced the state of the art.

[tysontom]

The AR5 was an excellent speaker; much better than the 2ax and in some ways better -in room- than the 3a. The cost of the 5 was too close to that of the 3a, while most consumers could not discern a difference between the 5 and 2ax. Their loss.

Why was the LST created ? Criticism of the 3a design and changes in the marketplace. The 3a had a stepped driver response with the response of the midrange roughly 3db lower than the woofer response, and the tweeter response an additional 3db lower (and -6db relative to the woofer). However the 3a was designed to replicate the listening perspective of a 10-15th row seat at a classical concert. Translated to a domestic room, that meant far field positioning. AR recommended a listening distance of 12-15 foot from the plane of the speakers. Excellent dispersion characteristics of the AR dome drivers meant that the sound reaching a listener 12-15 feet away would be a mix of direct and reverberant content. Thus the overall balance in situ would seem to be better than what measurements would imply. Consumers agreed with and the AR approach and by the late 1960's AR had a 60% market share.

What happened?

Critics were persistent in noting the stepped measurement response of AR speakers. The composition of the market changed, with younger buyers who preferred pop music gradually replacing older buyers who preferred Classical and Jazz. Pop buyers had a preference for flat response, like what they head at a concert. Competing speaker designs delivered flatter FR, with AR like bass and could play rock music at appropriate levels. Dynaco A25, Advent, EPI, Boston Acoustics, and of course the JBL 100.

The inherent flaw of AR dome speaker design was fragility. The drivers could not handle large amounts of power nor could they produce loud SPL at the listening position.

AR wanted to produce a speaker that addressed critics and the needs of a changing market. That meant a flat in room response and loud in room SPL. The solution was multiple dome drivers arranged across a 120 degree plane. Measured response was indeed flat in room (+/- 3db 50hz-15khz), with the ability to absorb prodigious amounts of power, and play at 105db+ for extended periods of time. However this solution brought additional problems. Audible phase distortion between the multiple dome drivers and the need for a very complex auto former driven crossover. In reality the LST was not suitable for a wide range of listening rooms.

The LST led directly to the AR9, which solved many of the problems of the LST. Single forward facing dome drivers eliminated phase distortion. Ferofluid (first used in the AR 10pi and AR 11) significantly raised the power handling ability of the dome drivers. The result was flat in rooms response, loud SPL and a design that was more room friendly. Like the 3a, and LST, the 9 advanced the state of the art.

rl1856:

This is an interesting message, and while it contains some truths, it's mostly based on imagination and presumption. As the old saying goes, "a beautiful hypothesis slain by an ugly fact." Therefore, taking each paragraph individually, here is my admittedly long-winded assessment of your comments:

1. The AR5 was an excellent speaker; much better than the 2ax and in some ways better -in room- than the 3a. The cost of the 5 was too close to that of the 3a, while most consumers could not discern a difference between the 5 and 2ax. Their loss.

There is actually some truth to this statement about the AR-5 vs. the AR-3a; the cost of the AR-5 was too close to the AR-3a, and there were some "in-room" differences in favor of the AR-5 over the AR-3a. The AR-3a had a heavier spectral balance than the AR-5, and it therefore sounded a bit different in a room because of this balance, despite the nearly identical measured acoustic-power response above 500-600 Hz. The AR-5 sounded a bit "clearer," for lack of a better description, throughout much of the midrange, than the AR-3a, mainly because of the power of the AR-3a woofer.

The AR-5 didn't particularly outshine the AR-2ax except in spaciousness and acoustic-power output into a room and, in fact, did not sound as good as the AR-2ax in the near-field response. The AR-2ax was more directional, however, and the crossover from the woofer to the 3.5-inch midrange was much higher than the AR-5's crossover to the 1.5-inch dome tweeter, and thus dispersion in the lower midrange was much to the AR-5's advantage. Because of the stellar acoustic-power response of the AR-5, however, it was more spacious and 3-dimensional in sound (vs. the AR-2ax) once well back in the reverberant listening environment.

2. Why was the LST created ? Criticism of the 3a design and changes in the marketplace.

The AR-LST was created because of "criticism in the marketplace" of the 3a design? Hardly! Some individuals and anti-AR critics complained about the "laid-back" or reticent quality of the AR-3a's spectral balance, but the overwhelming critical acclaim and magazine reviews of this speaker were simply stellar, probably never exceeded in perceived excellence by any other product ever reviewed in the audio press. In 2010, The Absolute Sound, a tweak, golden-ear magazine by any measure, and not one to like any establishment loudspeaker—especially Acoustic Research—voted among all its editors that the AR-3a was the 2^nd most important loudspeaker in the history of audio. That's a pretty good endorsement. So, the AR-LST didn't come about because of "criticism in the marketplace" of the AR-3a's design

3. The 3a had a stepped driver response with the response of the midrange roughly 3db lower than the woofer response, and the tweeter response an additional 3db lower (and -6db relative to the woofer).

The actual sensitivity of the AR-3a drivers is not identical across the board, as suggested in this statement, but this statement is based on the AR-3a published data sheet (1967) that shows the relative output—superimposed as if a total-system frequency response—on a single graph. "The 3a had a stepped driver response...." This is nonsense. If you listened 3-4 feet in front of an AR-3a, this so-called "stepped" response might be bothersome (but not as much as the interference effects and diffraction). But no one listens up that close, and what one hears in the reverberant field is overwhelmingly reflected energy with only a small percentage of "direct" energy from the AR-3a. This is simply because the 3a has outstanding dispersion, and once you are just a few feet back from the speaker, depending on the room constant, you are hearing reflected energy with directional clues only in small proportions. So, what about the reduced sensitivity of the AR-3a midrange and tweeter? In the reverberant field, this lack of on-axis energy does show up in a slightly downward-sloping extreme treble response, but the total energy in the reverberant field is astonishingly flat and uniform all the way out to nearly 20kHz! The most amazing part of this is that some speakers with flat treble energy on axis out to 20kHz, actually sound duller than the AR-3a back in the reverberant field. This is the magic of wide dispersion into the listening environment.

4. However the 3a was designed to replicate the listening perspective of a 10-15th row seat at a classical concert. Translated to a domestic room, that meant far field positioning. AR recommended a listening distance of 12-15 foot from the plane of the speakers. Excellent dispersion characteristics of the AR dome drivers meant that the sound reaching a listener 12-15 feet away would be a mix of direct and reverberant content. Thus the overall balance in situ would seem to be better than what measurements would imply.

10^th-15^th row seat at a classical concert? Huh? Speculation, but in truth the spectral balance did mean somewhere farther back in the concert hall. Yes the AR-3a was designed to be a speaker listened to back in the reverberant field. AR intentionally chose dispersion over efficiency of the midrange and tweeter to get the desired acoustic-power response. And it is true that the overall balance "in situ," was better than what the measurements would imply, but understanding the meaning of the AR-3a measurements is not what happened here.

Again, AR superimposed—into one graph—the output of each driver measured anechoically to let the reader understand what each driver was capable of doing. It was not a "system frequency response," as is interpreted by poster rl1856, and it was never intended to be interpreted the way that rl1856 has read it. Those response measurements were there to show the linearity and smoothness of each individual driver, not its efficiency or more correctly, sensitivity.

But look at competitive speakers, such as the Large Advent, the JBL Century L100, Dynaco A25 or others with greater-efficiency tweeters on axis, and look at them within their acoustic-power output framework. In the near field, these speaker are decidedly "brighter" and more "forward-sounding" than the AR-3a, yet back in the reverberant listening field, each of those speakers sounds less 3-dimensional or "spacious" than the AR-3a! Some actually sound downright dull well back in the reverberant field because the lack of total acoustical energy reaching the listener's ears is slightly truncated due to poorer dispersion. The simple reason is that what we hear back in the reverberant field in most moderately absorptive rooms is predominantly reflected energy, and if a speaker has less than stellar off-axis output, the integrated acoustic-power response will be more "drooped" and poorer.

Acoustic-power response of a quite-expensive JBL speaker (higher in ranking than the Century L100). Note the rapid fall-off in treble out into the upper midrange and treble. This measurement was done in AR's "house-of-horrors" reverberant test chamber in 1967.

Acoustic-power response of the AR-3a and AR-5, taken in AR's "house-of-horrors" reverberant test chamber in 1967.

5. Consumers agreed with and the AR approach and by the late 1960's AR had a 60% market share.

Wrong again. AR had a 32.2% market-share in 1966, the highest of any loudspeaker manufacturer in the history of the high-fidelity industry, but it never had 60%!

6. What happened? Critics were persistent in noting the stepped measurement response of AR speakers. The composition of the market changed, with younger buyers who preferred pop music gradually replacing older buyers who preferred Classical and Jazz. Pop buyers had a preference for flat response, like what they head at a concert. Competing speaker designs delivered flatter FR, with AR like bass and could play rock music at appropriate levels. Dynaco A25, Advent, EPI, Boston Acoustics, and of course the JBL 100.

Again, there's no such thing as "stepped-measurement response," as in the AR speakers; but yes, the high-fidelity market did change, and classical music gradually became less popular than pop music, no argument here. Pop buyers were simply less discerning about replicating the "concert-hall" experience; rather, they were looking for bright, overpowering midrange ("honkiness" in some cases) and "in-your-face" treble response, often experienced up close within a narrow listening window. It was therefore not "flat" response that pop-music lovers wanted so much as thumping bass (predominantly 60-80 Hz) and high clarity in the midrange and treble. This was the illusion of "hi-fi" sound for many of the later baby-boomers and perhaps millennial music-lovers. Not all were that way, of course.

7. The inherent flaw of AR dome speaker design was fragility. The drivers could not handle large amounts of power nor could they produce loud SPL at the listening position.

The AR-3a was not "fragile." It was low in efficiency (sensitivity) and impedance, and therefore it drew a huge amount of amplifier current at low impedances when playing at high output levels. For example, the AR-3a could absorb 400 watts for 2 seconds continuously within its thermal rating, and it could sustain instantaneous peaks of 1000 watts; however, tweeters were easily overpowered by amplifiers not up to the task or by listeners wanting to listen to electronic or pop music at "true" levels. Both of these conditions usually accompanied one another. So, the AR-3a was by no means a "fragile" design.

8. AR wanted to produce a speaker that addressed critics and the needs of a changing market. That meant a flat in room response and loud in room SPL. The solution was multiple dome drivers arranged across a 120 degree plane. Measured response was indeed flat in room (+/- 3db 50hz-15khz), with the ability to absorb prodigious amounts of power, and play at 105db+ for extended periods of time.

No, this wasn't the reason for the AR-LST. It was not designed to "address the critics and needs of a changing market." This is not the place to go into the reasons for the etiology of LST, but what rl1856 says is just speculation and imagination. It is true that the LST could produce even flatter acoustic-power response than the AR-3a, and it could produce higher sound outputs with lower distortion than the AR-3a, and it could handle significantly higher input power (one reviewer friend of mine said that he once measured brief, instantaneous peaks of nearly 5,000 watts into the LST). But the LST wasn't produced for this reason.

9. However this solution brought additional problems. Audible phase distortion between the multiple dome drivers and the need for a very complex auto former driven crossover. In reality the LST was not suitable for a wide range of listening rooms.

There was absolutely zero (zilch, nada) "audible phase distortion in the reverberant field with the AR-LST." Again, speculation and imagination. If you measured an LST at 1 meter on axis, and then you measured again a little below the first measurement, and so on, you would get all sorts of phase shifts, anomalies and irregularities, but that's not what you hear with the LST, because no one listens up close to this speaker, ever (well, some have). Therefore, the interference effects are "swamped" in the reverberant field, and you could never detect any phase distortion, even if your life depended upon it.

The autotransformer was a "spectral balance" control, not a phase corrector! It was designed to give different spectral balances, all relative to the midrange, in the LST from flat to sloped output. It had nothing to do with "phase distortion," which is a serious misnomer.

10. The LST led directly to the AR9, which solved many of the problems of the LST. Single forward facing dome drivers eliminated phase distortion. Ferofluid (first used in the AR 10pi and AR 11) significantly raised the power handling ability of the dome drivers. The result was flat in rooms response, loud SPL and a design that was more room friendly. Like the 3a, and LST, the 9 advanced the state of the art.

The AR-LST did not lead directly to the AR9. The LST happened to be the flagship of the "classic" AR product line during the early 1970s, but the AR-10Pi was the next flagship, and then product development lead to the tower speakers and the famous "electronic automatic transmission" developments. There were distinctly different approaches for different needs. In actuality, the AR9 probably will not handle more peak power than the LST, if as much, especially into the critical mid-range and treble frequencies. It definitely will in the deep bass!

It is very true that each of these speakers (and the all-conquering AR-3 preceding the AR-3a) advanced the state of the art!

So there you have it. "A beautiful hypothesis slain by an ugly fact." Things aren't what they seem to be, but I think the intent was to give forth some ideas on what the writer had on his mind.

—Tom Tyson

[iso]

The autotransformer control kept the output level of the midranges constant, so the apparent loudness of the speaker remained the same, regardless of switch position.

This may be where Quad got the idea for their "tilt" type tone control in their preamplifiers? Or were this kind of tone controls used earlier in commercial gear?

Best Regards

Kimmo

[Steve F]

The theory behind using the autotransformer in the LST was that since the LST was intended to be a professional monitor speaker, it would be critical to the recording/mixing engineer that the apparent loudness of the speaker stayed the same, regardless of spectral balance. A pre-amplifier designed for home use—like the Quad—would have completely different goals for its tone controls.

A few other quick comments, in addition to what Tom says above (he is absolutely spot-on with all of his observations).

8. AR wanted to produce a speaker that addressed critics and the needs of a changing market.

Referring back to my original post No. 1 in this thread, when the LST was conceived in 1969, the “changing market” and “critics” being referenced above didn’t really exist.

Why did AR do the LST? That’s an intriguing question. The first thing you need to know is that products take a very long time to go from a ‘napkin sketch’ to finished goods that are shipping out the door. If it’s a product based on an existing product—filling in a gap in an existing product line, like, say, the AR-5—then those can be done in perhaps 9 months to a year, at the very fastest. It just takes longer than people realize to design things, prototype them, get sample parts in, approve them, fend off the inevitable schedule-ruining interference from the “higher-ups,” etc. etc. That’s for an AR-5, about as “simple” a design/introduction process as a company is likely to have.

The LST was intro’d in fall 1971, meaning it was probably a glimmer in someone’s eye at AR in 1969. In 1969, AR still ruled the roost. Advent and EPI hadn’t yet made any impact and the 4x-[1^st-gen] 2ax-3a were the stars of the day.

The market hadn’t “changed” yet in 1969. The “critics” and retail dealers weren’t yet disparaging AR products like they would be just a few short years later. The stereo market moved very quickly in that timeframe. 1971 was a long, long way away from 1969. As I said—quite accurately, because I lived through it and witnessed it first-hand—Advent (for example) went from non-existent in 1969 to being the No. 1 retail showroom speaker in 1971.

People tend to look at a product’s reason-for-being at the date of introduction. That’s the wrong way to do it. It’s the date of concept that counts. For a hugely complex product like the LST—a product with absolutely no similar products (cabinet shape, use of multiple drivers, autotransformer, etc., etc.) in the past for AR to draw upon—the gestation period would be at least two years. I’ve done the marketing concepts and directed the engineering/production development of hundreds of products at Bose, Boston Acoustics and Atlantic Technology. In 1969, developing the LST would have been nearly as complex as, well, putting a man on the moon.

Another error in looking at the LST is to think it was somehow intended for a mass buying audience. The statement “to address the needs of a changing market” implies that AR thought the LST was intended to sell to the everyday stereo customer. “Hey, think that 3a is a little dull compared to that JBL L-100? Here, listen to this LST instead. Yeah, I know the 3a is $250, the L-100 is $273 and the LST is $600, but if you want that great AR bass with a little more top end, then this LST is for you. Cash or charge?”

No.

The LST was not intended for or marketed to the “average” stereo customer, so in no way was its mission to “produce a speaker that addressed critics and the needs of a changing market.”

Steve F.

[owlsplace]

.....

6. What happened? Critics were persistent in noting the stepped measurement response of AR speakers. The composition of the market changed, with younger buyers who preferred pop music gradually replacing older buyers who preferred Classical and Jazz. Pop buyers had a preference for flat response, like what they head at a concert. Competing speaker designs delivered flatter FR, with AR like bass and could play rock music at appropriate levels. Dynaco A25, Advent, EPI, Boston Acoustics, and of course the JBL 100.

Again, there's no such thing as "stepped-measurement response," as in the AR speakers; but yes, the high-fidelity market did change, and classical music gradually became less popular than pop music, no argument here. Pop buyers were simply less discerning about replicating the "concert-hall" experience; rather, they were looking for bright, overpowering midrange ("honkiness" in some cases) and "in-your-face" treble response, often experienced up close within a narrow listening window. It was therefore not "flat" response that pop-music lovers wanted so much as thumping bass (predominantly 60-80 Hz) and high clarity in the midrange and treble. This was the illusion of "hi-fi" sound for many of the later baby-boomers and perhaps millennial music-lovers. Not all were that way, of course.

....

Since you mentioned the "boom-squaker" designs that came to dominate the marketplace, Tom, I still think the preference for that design came about because of a generation that never heard acoustic music having been weaned on electronically produced music from day one.

I think the LST harkens back to an earlier era, perhaps becoming the epitome of it.

Wouldn't it be nice if there was one design that could match all tastes and integrate into every listening environment?

I grabbed an old pair of ESS speakers at the thrift the other day thinking I would experiment with the Heil drivers. They didn't age so well compared to the Classic AR's. By the same token, I saw a movie at an IMAX theatre yesterday -- not very well done at all compared to the first IMAX theatre I visited in a much larger city many years ago. Maybe everyone really is getting "dumbed-down!" They certainly seem to be settling for less in my opinion.

Roger

[tysontom]

Why did AR do the LST? That’s an intriguing question. The first thing you need to know is that products take a very long time to go from a ‘napkin sketch’ to finished goods that are shipping out the door. If it’s a product based on an existing product—filling in a gap in an existing product line, like, say, the AR-5—then those can be done in perhaps 9 months to a year, at the very fastest. It just takes longer than people realize to design things, prototype them, get sample parts in, approve them, fend off the inevitable schedule-ruining interference from the “higher-ups,” etc. etc. That’s for an AR-5, about as “simple” a design/introduction process as a company is likely to have.

The LST was intro’d in fall 1971, meaning it was probably a glimmer in someone’s eye at AR in 1969. In 1969, AR still ruled the roost. Advent and EPI hadn’t yet made any impact and the 4x-[1^st-gen]2ax-3a were the stars of the day.

So did Roy Allison say to someone, “You know, we could do this speaker with four ea. of the 3a’s mids and tweets, angle them and the thing would have truly flat power response in the forward hemisphere. Recording studios would eat it up, they’d jump at the opportunity to have a recording monitor as accurate, and repeatable as their best electronics.”

Maybe he or someone else actually said that.

Or maybe it was something like, “You know, if we took 4 ea. of the 3a’s mids and tweets, angled them, we’d have a speaker that could handle enough power in the mid-high end to have a flat power response in the forward hemisphere. We could do it. It’d be cool.”

“Why would we want to do that? What the heck would we do with it? Who’d buy it?”

“Beats the heck outta me. But we’d get great reviews and publicity for having the “World’s Best Speaker,” and we could leverage that PR to the bank. Who knows? Maybe some recording studio would want the thing.”

And then in a very rare stroke of marketing genius, AR decided to sell the LST to individuals only by “special permission”: the customer had to place an order at an ‘authorized’ AR LST dealer, pay for them up front, and then IIRC, AR would ship them directly to the customer’s home. Ooooooo…..so secret…..so special. (In time, of course, you could simply buy them at the store.)

As a product, the LST was one of the truly great audio products of all time. The autotransformer feature must’ve taken quite a while to design and perfect, as did the decision on what the spectral balance would be for each of the six transformer positions. I can imagine hours of listening and many hours of arguing. I’ve been there, many times. I’ve read that AR minimized the inevitable interference between all those closely-spaced mids and tweeters and that also must’ve taken a lot of prototype cabinets and a lot of listening and measuring.

Remember also, the LST was done eons before there was today’s degree of automated computer analysis and measurement, so every curve was swept individually, mic placed by hand, the pen scrolling out the curve on the moving graph paper. Tedious.

Considering the amount of discussion over exactly what to make, how many drivers, pointing in what direction at what angle (this is known as the ‘product definition,’ and settling on a hard def—a “frozen def” as we say— is often the hardest part of the entire process), the drawing of the cab, sending it out for samples, getting quotes from prospective vendors (assuming anyone even wanted to make a crazy cabinet like that!), doing all the measurements and listening, etc.----man! I’m surprised they could do this in just two years. Maybe they started the LST in 1965!

Gentlemen, you simply listen to and enjoy the LST as a finished speaker. But as someone who has spent many decades on the inside and has been part of the conception/engineering/manufacturing/marketing process for countless products from Bose, BA and Atlantic Technology, I can’t even begin to imagine the complexity involved in bringing an earth-shattering product like the LST to market. Even beyond the “Manhattan Project” nature of the nearly-equally-impossible AR9, because the LST was done mostly by hand. (Much like Apollo 13 that flew to the moon in 1969, being designed and engineered mostly by hand.)

However much you respect and admire this speaker, double it. No, quadruple it.

Steve F.

"Why did AR do the LST? That’s an intriguing question."

The genesis of the AR-LST is interesting. After Ed Villchur retired from AR, his long-time friend and treasurer, Abe Hoffman, took over as president of the company. Hoffman guided AR through the late 1960s until the end of his 5-year employment contract with Teledyne Corporation in 1972, but was "let go" by the company in that year to be replaced Victor Amador, who knew little about the about the high-fidelity audio industry. Amador lasted not quite two years before he was sent packing, and Teledyne appointed Martin "Marty" Borish to be president. Previously, in 1967, Teledyne brought in Borish to conduct AR's "overseas operations.". He was made Vice President International, stationed in AR's Houghton-Regis, England, operation and had close contact with agents throughout Italy (the largest market), Germany, France and England.

While VP International, Borish was approached by AR's biggest international customer, Italy, requesting a "high-end" AR system to compete with the best products from Quad, KEF, Wharfedale and the like. They requested a speaker with prodigious power-handling capability and flat acoustic-power output, beyond anything produced in Europe at the time. The Italians had great influence on AR, so Borish returned to Cambridge and sat down with Roy to discuss this new product. At the same time, commercial customers and recording studios in the US were calling for the same thing, so Roy set about designing the AR-LST, a speaker ultimately with four-times the power-handling capability of the AR-3a and with flatter, adjustable-slope acoustic-power response. The AR-3a woofer was known to be robust, so using four midrange and four tweeters was the answer, arranged in the special cabinet we know as the AR-LST, clearly one of the finest loudspeakers of all times. This complex project design apparently began in the 1968 to 1969 time-frame, as suggested by Steve, and was not an insignificant project through its completion and introduction in 1971.

AR-LST File Image 1971

--Tom Tyson

[Sonnar]

Very interesting Tom ! AR speakers were popular in Italy since early sixties, my father had a pair of AR 2 at the time of my birth, september 1960, and in late sixties and seventies AR has a leader position in the market. It's very easy to find AR products from the golden era in Italy. Two of my neighbours have AR speakers , one has a pair of AR 90, and the other has AR 2ax . AR 3a, LST , 10 Pi, and the very popular AR 6 are still very respected and sought after speakers even today. My father bought his AR LST in 1972/73, but unfortunately at the time SS amps were unable to drive it seriously. I 'd like to hear a pair of LST with a modern, high power, high current power amp. Best wishes, Adriano