Aadams

You can find a few threads on the AR12. Here is a good one on a restoration:

Yes. Make sure the amp is rated by the manufacturer for 4 ohm loads.

You could use an equalizer and experiment with lowering the band(s) centered on 1k, 2k and 4k.

An excellent presentation by the artist and sound engineer on capturing, editing and mixing acoustic instrument performance using modern recording technology. Focus is Jazz and Classical. https://wyntonmarsalis.org/videos/view/editing-mixing-your-masterpiece-considerations-when-recording-jazz-jazz-congress-2020

Released this week, full concert on the evolution of the American Big Band. Concert performance and sound are top notch.

Which is exactly the kind of material for which the AR5 was built. The original tweeter is the only tweeter that uniformly extends the power response of the AR5/3a domed mid into the next octave. which is a big deal with live recordings or large classical ensembles. The HIVis are more of an on axis tweeter and work fine for studio recordings. Adams

If you can hear to 8k there is a difference. And, it depends on source material as well as your listening habits. RoyC is the only person I know of that can attest to a/b comparison. Adams

You have a nice pair of unmolested 5s. Have you read the AR 3a restoration guide? It will answer many of your questions. JIC originality in both appearance and performance is important to you, are you aware your original tweeters can be rebuilt as long as the bodies are intact? RE the pots: Consensus these days is replace with lpads or new style potentiometers. As a long time pot hold out. I can vouch, Lpads are better. When you reseal the speakers use gasket tape, especially on the tweeters and mids, if you remove them for some reason. AR 5 cabs should be stuffed with approx 22oz of fiberglass. Any other material is an experiment. I have no idea why the duct seal is around the woofer magnet unless to stop a vibration or rattle. Unless they are damaged the answer is no. Adams

Jazz pay dirt from the 21st century. For the of duration the pandemic only, Jazz At Lincoln Center is releasing, to the public, full length performances from its concert archives that are available on youtube. The performance and production standards are top notch. Video is at least 720 Hi def and sound is CD quality stereo. Listener perspective is front row center. If you like jazz quintets, septets and big band arrangements performed before a live audience, by top notch ensembles, this is a cost free opportunity. Streaming live performance sound through Classic ARs is a real treat. This a link to part of a 2 hour performance. https://www.youtube.com/watch?v=3SP3NfxI7dg featuring Coltlrane's Ole'.

Anders, Here is a thread about a woofer like yours. It is worth reading for the information about properly repairing these old woofers.

The outer edge of the new surround is glued to the Masonite spacer ring. The woofer in the photos shows a ring later woofers don’t have the ring.

It is unlikely, especially with the big caps being Spragues. If you are hearing distortion with the woofer out of the cabinet there is probably no need to switch the woofers but it would offer confirmation. Have you checked the attachment of spacer ring on the metal frame?

If it doesn't rub when you do a manual push test, you can further isolate by swapping the woofers to see if the problem moves. If it is the woofer and not in the wiring ,applying a signal directly to the woofer terminals would be my last choice after examining the cone and all of its attachment points. You can Wait for RoyC to reply. He probably already knows the answer from the sound in your video. Adams

If you connect them to your a and b speaker terminals they will show around 2.5 ohms to your receiver. Your receiver will interrupt, maybe permanently. You could perhaps connect in series but you probably would be safer using an amp rated for 2 ohm loads. See what others say. Adams

Here is one from 1999. Recorded live for TV at the Supper Club in NY, originally as reenactment of a 1930's dance club engagement, it was remastered as a CD recording and released in 2000. Captures the live ambience and energy of an outstanding live performance.

This has been discussed several times. The Simple Speakers version is a last resort substitute for any AR 11" woofer after the AR3. There is no alternative for the AR1 or AR3 original woofer if you want original performance, not even a later AR Woofer.

And those had all Compulytics in both cabs.

Assuming you have the Spectral Balance controls at the same setting on both speakers and your electronics are not the source........ You may need new fuses. Have you tried swapping the fuses to move the problem? Failing fuses are reputed to cause this sort of issue in LSTs.

Duct seal works great and is inexpensive but can provide an unfriendly experience on particle board baffles, if you must remove drivers later. I second Jkent's preference for tape. For your project it is the preferred choice. Adams

They were designed ideally to be placed on the floor, back side square against the wall for best bass but not in a corner. Those should be good performing speakers. Even better if you could get all AR drivers.

Yes original. Those look like Unicon caps and they are probably still good. It could be worth it to listen before you replace. Replacing caps can be a low payoff activity. Adams

If everything is original, the internal cab volume and the crossover specs will matter more than appearance. The tweeter appears to be a .75. Any one of the 6.5" named above should sound practically the same as this Redbox version.

I think it is a version of the TSW110 or possibly 100.

Redbox 2, which was a British reissue of the AR18s, has been discussed here in the distant past. Your description seems to fit an AR8b which can be found in the AR section of the library in the "Post Classic Series". It would help if you provide photos.

You sure your problem is not the DAC? The Midwest has been recommended as the most suitable tweeter replacement. There is no new replacement for the UMR.