Aadams

3a 575hz and 525hz This thread is drifting BUT the 3a vs 5 vs LST vs AR9 mid range clarity topic was aired out about three years ago. The AR3a is equal to the AR5 and AR9 in mid range clarity if it is optimally placed in relation to the listener’s position. For the 3 or 3a this means you start by recessing in a bookcase or a wall. Roy Allison wrote a paper explaining the problem after he left AR. Almost any other practical placement of a 10 octave, front facing, three way is a compromise and often results in mid range “suck out” due to cancellations from boundary reflections if the woofer is also reproducing mid-range frequencies. This research led to the Allison 1 and the AR9. Welcome Back Adams

Does this explain why the chart below appears to show a 24db/octave curve for the mid

Very Nice. Thanks to member Carlspeak and others the empirical evidence suggests this is generally true. I have 3as with Spragues and 3as with new Daytons, both with rebuilt tweeters and lpads. There is no practical difference in the sound. If you don't hear a problem now there is no reason to change the caps. The narrow tape will work ok.

Members @RoyC and @Chris1this1 repair the original 3a tweeter with three orange blobs around the dome base. You can send them a message.

It can make an audible difference if your speaker needs it. More importantly, the product from Vintage AR and member @RoyC is the only sealant for sale that will not cause long term damage to your cloth surround. It won't hurt to try it.

I agree with Giorgio. There is something odd about these woofers. I have examined the front baffle photo on three different monitors and it looks to me like the voice coil covers are concave, the surrounds are attached on the back side of the cone and are shiny like butyl rather than dull like foam. Tell me I am wrong please.

According to bits and pieces of info scattered around CSP, there were never more than 2000 pairs made in the US. It is surprising to me how many current LST owners have multiple pairs of those that remain. Good luck.

Ported and downfiring? My guess is probably not, but boundaries will still affect the output. You just need to experiment.

A practical example from Roy Allison's research on Boundary Effects

I apologize for that conservation, I recall being a bit obstinate. Had I been less so, I would have immediately picked up on a key piece of information you passed along at the time, instead of realizing much later. You have been posting useful, durable, juicy nuggets for twenty two years. Thanks for your patience and endurance.

Outstanding, carefully polished work with important anecdotal knowledge. I especially like the inclusion of these two excerpts from page 10. AR9 proved to be an exceptionally potent low-frequency loudspeaker, but one that hardly called attention to itself. The speaker has such low harmonic distortion and smooth response, that some listeners—expecting heavier bass—felt the speaker was perhaps bass-shy, yet the true measure of a high-quality bass reproducer is no bass reproduction unless called for in the program material. During AR’s presentation of the AR9 to the Boston Audio Society, Tim Holl acknowledged Roy Allison’s work in this area in describing the design of theAR9, similar in approach of the Allison: One speaker’s pioneering “Room-Matched” design.

Agree with Giorgio. You will wait a long time to find a better unmolested pair. At 130 BP = 175 US the price is very reasonable.

That version used Velcro on the grills. No glue.

What is the impediment?

For optimum performance, the literature makes it clear that the Allison ARs were best when recessed in a wall or a wall sized bookshelf with no void space, excluding the LSTs.

I found this bit of irony embedded in the Allison Archives. Here is the link if you want to read http://www.classicspeakerpages.net/library/allison/other/technical_articles_by_roy_f/technical_articles_by_roy_f_20.html#previous-photo Here is the ironic part.

This is the widest dynamic range music recording I have ever heard that did not use special effects. Performed live 2013. Beautiful performance, beautiful recording of The Firebird. You will need a silent listening space to hear all the music. There are several 12- 15db peaks, almost all in the last eight minutes.

Roy A. was a sly one. He knew that the ESW worked better on Allisons than on most other brands including AR. Any Acoustic Suspension Speaker that could withstand the stress such as a Large Advent or AR3, 3a, also had a crossover so high into the midrange that phase or “doppler” distortion could become a problem. The Allison One, Two and Three had a low crossover of 350hz, low enough that such distortion could not be an issue. An ESW combined with the 1000hz crossover of a Large Advent or AR3 would be a doppler distortion generator. AR didn’t avoid phase distortion from amplified low bass frequencies until the AR9.

Pretty sure these are non polar.

Can you show the printed label on the side?

They weren't polarized. They were radial NPE vs axial.

Looks like a 58S cabinet to me.

If your 58s has the original Unicon caps you might want to stay with those. They have a reputation for durability.

Whenever someone mentions consecutive numbers in reference to Classic AR speakers it immediately triggers skepticism; Not impossible but highly improbable. The speakers were never built in pairs and consecutive serial numbers are not considered important in the AR world in general but could be of value to you. All that matters is the drivers and crossovers are correct for an AR1. If the joinery and hole cuts are identical then they might be consecutive serials but more likely they were built with the same tooling. If the cabinets are not identical then they are 99.9% not consecutive. Even if the cabs are modern copies all that matters is the drivers and crossovers are correct. Consecutive serials mean nothing to a careful AR buyer. Do you have better images of front and back? Adams

First time I have seen a thread like this here at CSP. This link will take you to the service manual and drawings in the library if that will help http://www.classicspeakerpages.net/library/acoustic_research/special_sections/electronics/ar_electronics_schematicsse/ar_electronics_service_manu/ar_electronics_service_manu_43.html#previous-photo