AR LST

[Guest]

Praise, Short Story, Question.

Hi guys,

Praise:

Just signed up. This site is GOLD. Information you can't find any other place. Thanks for all the valuable information!

Short Story:

I am a long time AR admirer. Fell in love with the 3A back in 1973 that I bought four of them to go quadraphonic. Remember that? BUT, when the LST came out, I had to buy them. So, I sold my four 3A’s and went to buy a pair of LSTs. To make a short story, never got them.

I was surprised to find them for sale on eBay, whenever you can find them. And the LST2; the price they want for the condition they are in; very high priced.

Seeing that the drivers are still available, I thought why not build a set using the new drivers from the 303. Just bought a set of 303s a year ago. So, I then have ¼ the drivers needed. I can build the x over network; all I need is to build the cabinets. And I will have a new set of LSTs.

Question:

Are the new drivers in the 303s as good as the ones from the 3a? Am I nuts? What are your thoughts?

[Guest]

They'll be LST replicas granted. What about the transformer they use for the low freq.? Do you have cabinet plans? I would be patient until you can find a set.

I have a set of LST's that I am unable to use due to the small house I live in and to top that toddlers. I will be buying a new home in a year or so and I am just waiting to fire them up. I let a friend use them for a few months and he was in love with them.

[Guest]

I am going to build my own plans for the cabinets. With some measurements from an original that some one will help me, I will figure it out, I hope. Maybe you can help?

I am not going to use a transformer. I like my speakers flat. And at the flat position, according to the schematic for the LST, the tweeters and woofer do not go through the transformer, the mids do in order to be attenuated. And that can be done with a voltage divider with resistors as done in all the other units.

Do you know if the new drivers from the 303s as good as the old 3As?

[ar_pro]

From what I understand of the LST, sacrificing five of the six energy profiles will leave you with considerably less of what that speaker's design sought to achieve. The "flat response" profile is not a real-world absolute, but something derived in anechoic conditions - clearly, the speaker's voicing will be influenced by the room in which it's installed...the energy profiles were an important AR contribution toward (here comes a bad word) "equalizing" the response of the system into its environment. If this capability is eliminated, the result will probably be closer to a "super AR 3a" than an LST, exhibiting only the latter system's power-handling and dispersal characteristics.

As an aside, has anyone ever tried to match the attributes of the LST with what AR accomplshed in the original (and only the original)9 design? I would think the 9's extended low end would be a superb complement to the LST.

Also - although the cabinet design and quality of construction was superb for its time (and for their original selling prices!), I'd be very interested in hearing the classic designs with unmodified electronics and drivers installed in superbly braced and aligned cabinets - it might be worth a try to grab a garage sale pair of 3as and see what better boxes could do.

[Guest Nigel]

>Do you know if the new drivers from the 303s as good as the

>old 3As?

Julian Hirsch said they are better, but the inductors in the 3A are better. If you do your own network, you can pick inductors and caps to suit.

If you are thinking about replicas, consider the original 9 instead of the LST.

Nigel

[Guest]

Interesting point!

Do you think that sacrificing the five profiles will result in what you call considerable less performance? I agree as you do that the six profiles is one of several overall enhancements of the LST design along with the increase power and dispersal improvements, the later two were, in my opinion, of greater importance.

A flat response is not real world absolute, as you have said, but it is a beginning point; a place to set reference to, otherwise it is all relative. There are so many variables involved in the process of making a recording that involving acoustics, equipment and recording techniques. The same can be said for playback. Who is to say that the other five energy profile settings of the LST will make a correction against all these variations? Why only five. Instead of five energy settings, why not resort to pots as done on the AR3a’s giving you more granularity?

What is the original 9 design that you make reference to?

Out of curiosity; I wonder what setting, energy profile, our LST owners use and why.

[ar_pro]

I believe that the current replacement drivers are sourced from Tonegen, in Japan - the original drivers were built by AR in Massachusetts (and later, in the UK). If they are manufactured to the same specs, it would be reasonable to assume that the performance should be the same.

You're right...there's no way to guarantee an absolutely flat response without adjusting for every variable - the AR approach with the LST provided "scientifically"-achieved performance curves that were considered to be both practically useful and not unmusical in the extreme. The variable conrols on the 3a were a less expensive (and failure-prone) approach that wouldn't be advisable on a multi-element, wide-dispersal system like the LST.

The original Model 9 can be seen in the literature section of this site...low frequencies are reproduced by a pair of standard AR woofers per system (this is the nominal 12" driver used in the 3a and LST)...this design made use of a bass extension and Q optimization circuit to achieve what's considered to be the most accurate and lowest extension bass of any AR product. Another innovation in this system was the use of the "Acoustic Blanket" for controlling the interaction between driver and mounting surface. You might want to listen to a pair of 9's before you buy all of those LST drivers!

[Guest]

Nigel,

I'm at a lost; what is the original 9? I missed that one.

Ed

[Guest Barrydor]

> What is the original 9 design that you make reference to?

Information on the AR-9 including specifications, assembly drawing and schematic is available in the AR section of this forum.

If anyone needs exact cabinet dimensions for an attempt to replicate, I will be happy to provide them.

Barry

[Guest]

>I believe that the current replacement drivers are sourced

>from Tonegen, in Japan - the original drivers were built by

>AR in Massachusetts (and later, in the UK). If they are

>manufactured to the same specs, it would be reasonable to

>assume that the performance should be the same.

>

Tonegen started to make the drivers back in the Teledyne days shortly after AR moved from Norwood to the Canton factory. Assuming that AR still obtain from the same source, replacement drivers sent out in the last 15 years would have been from Tonegen.

[Guest]

ar_pro,

You may be right. I did not know of this unit, I was out of touch with AR since 1975 on. This must be some speaker! How was the dispersal characteristics of this unit? That acoustic blanket is an interesting concept.

Ed

[Guest]

Barry,

Thanks for the offer. Can you send me a copy of the cabinet prints; I may be interested. Did not know of this unit. Was this unit produced in the 80's? How will you send the prints; need my email address?

thanks,

Ed

[ar_pro]

Ed - the 9 is voiced very much like the other top-line AR speakers (3a, LST, 10pi), although it uses a large dome (firing from a flared semi-horn) for the upper midrange. It does not have the wide dispersion characteristics of the LST, though its tall vertical orientation provides for excellent driver placement and fine imaging (a lot of credit must go to AR's first use of vertically-aligned drivers and the Acoustic Blanket) - winding up with mirror-imaged systems (as in the the LST, and unlike AR's previous high-end designs), and a really coherent sound source. To my ears, though, the 9's premier strength is the quality of bass response - the AR philosophy of low frequency reproduction reached its peak in the original 9. The system can also be bi-amplified, using the internal crossover, which separates the bass section from the rest of the system, and allows additional flexibility in amplification.

[Guest Barrydor]

If the AR9 was produced over 20 years ago, and regarded by many as the best AR produced, and by some as the best in the world, then; how do the new AR towerers produced today compare to the old AR9?

> In my humble opinion, as an AR9 owner for 26 years, there is no comparison

Barry

[Guest Barrydor]

Can you send me a copy of the cabinet prints; I may be interested.

> The cabinet prints are on this forum. Check them out; if you are still interested, let me know

Did not know of this unit. Was this unit produced in the 80's?

> Produced in the late '80s, I believe. About a four-year run

How will you send the prints; need my email address?

> Yes

[Guest]

ar_pro,

If the AR9 was produced over 20 years ago, and regarded by many as the best AR produced, and by some as the best in the world, then; how do the new AR towerers produced today compare to the old AR9?

Ed

[ar_pro]

Ed - Not much chance that there's going to be a website 20 years from now, dedicated to celebrating, discussing & restoring the current crop of AR designs. It appears that most of AR's important contributions don't extend past the late '70s (with the exception of the original "Magic" speaker, which bears little resemblance to anything that came before, and really stands out)...the groundbreaking contributions of design (the acoustic suspension woofer, dome midrange & tweeter drivers, compact systems that deliver excellent bass) and product execution were produced in the early years. The top-line AR speaker designs leading up to the LST and 9 were evolutionary - building upon previous experience, and utilizing applied science. It can be argued that the tipping point came in the late '70s to early '80s - a good indicator is the life-span of an AR design - take a look at the "AR Model History" list of products to see how long a speaker model was in the line-up. Early on, speaker designs were long-lived, and gave birth to their replacements, or were simply improved in a legitimate manner; not just "disappearing" from the line, to be replaced each year by another vinyl-clad box, indistinguishable from a hundred other such products. Personally, I'd climb over a mountain of current AR speakers to get to a pair of LSTs or 9s!

[kkantor]

Hey, LSTers...

I sold my pair last year. What can I say? I already rent a storage space for accumulated speakers. Foolishly, and being in a time crunch, I shipped them off without measuring them one last time.

If anyone has one in the San Francisco area, or is willing to go to the trouble of getting one to me, I'd be happy to to measure the crossover response, and design passive networks that approximate each tap on the autotransformer. I'd only need the speaker for 15 or 20 minutes.

A 10pi might be interesting, too.

Ken Kantor

Intelligent Audio Systems, Inc.

Benicia, CA

[administrator]

Also .. if anyone is in Southern California with the LST's or 10pi's, I can bring them up to Ken. I am planning on a road trip to the San Francisco area soon!

Mark

[ToastedAlmond]

As a vintage AR-9 owner (albeit only for about the last 6 months), I can state empatically that low end wise, these are the cats whiskers. I am in the process of inserting an Onkyo M-506 muy gusto power amp to drive the woofer section. That should take it to a totally different dimension from what I gather. Can't wait.

Toasted Almond

[tysontom]

>I am not going to use a transformer. I like my speakers flat. And at the flat position, according to the schematic for the LST, the tweeters and woofer do not go through the transformer, the mids do in order to be attenuated. And that can be done with a voltage divider with resistors as done in all the other units.<

Flat in one environment may not necessarily be flat in another. The #2 tap might be too bright in some rooms, so if your room fell into this category you would have shot yourself in the foot by eliminating the autotransformer. In any event, it doesn't hurt anything by staying in the crossover.

The autotransformer in the LST was important to permit users to adjust the relative output levels of the woofer and tweeters relative to the midrange, which remains relatively constant through all switch positions. Each tap on the autotransformer switch had 1-dB increments. The #2 position was the "flattest," in that the output of the woofer, midrange drivers and tweeters was closely matched (the equivalent tap closest to the AR-3a's output was #5 or #6). The #2 position would also give the flattest acoustic-power response in most environments, and it was measured in AR's anechoic and semi-reverberant chambers. The key words are "acoustic-power response," not necessary just "frequency response." The frequency response of each driver of an AR-LST, as well as the system as a whole, is very flat and uniform on- and off-axis, but it is the power response that is so remarkable about this speaker. There are probably only a handful of speakers that can compare to the LST in this respect, and most were made by the same man who designed the LST, Roy Allison.

In the AR-3a, no manner of level-control twiddling can match the output level of each individual driver, even though the 3a's power response was quite flat and uniform also. The LST's autotransformer took care of this problem. Also, of course, the LST has much wider dispersion and much higher power-handling capability. Caution must still be used, though, because the tweeters and midrange driver are wired in a series-parallel configuration, and slight differences in efficiency among those old drivers can result in one driver taking the brunt of a power overload.

--Tom Tyson