RoyC

No question about it... At the very least the controls' wiping surfaces are tarnished resulting in intermittent contact. More likely, they are corroded. Roy

The cabinet's serial number does date it to late '70 or early '71. This was the transition period between the cloth surround/damping ring/alnico magnet woofer and the next version, which had the new smooth cone/foam surround/ferrite magnet. For a short time, the damping ring was used with the new cone when it was first introduced. Although the color of the cone seems off, I agree with Frank regarding the photo. Roy

If they originally had foam on the surface, they are probably the Tonegen replacement tweeter retailed and wholesaled by now-defunct AR authorized service center, AB Tech. This tweeter was a good replacement, but is no longer available. Without the foam, the excellent Midwest and Tonegen replacements are quite similar. If you are otherwise satisfied with your tweeters, you can remove the loose foam, and use them as is. Btw, the current replacement sold by SS is not the same as the Tonegen or MW replacements. Roy

The "Utility" version of the Original Large Advent Loudspeaker always had a vinyl-veneered basic cabinet, as shown in your photo. The "Walnut" OLA always had wood veneer and decorative front trim.

I was thinking the same thing as I looked at your photos. Ha, based on decades of working inside these cabinets, it seems to me that some of the staplers were either having lots of fun with the gun, or just really bad shots.

Thanks for posting. Insight into the hand-made nature of these earlier AR models is always interesting and appreciated. On two occasions I've found remnants of paper shims in the voice coil gaps of AR-3 tweeters. Apologies to fellow geeks of the forum for not posting a photo or two... Roy

I am, but I don't ship internationally. Ask forum member, Chris1this1. His tweeter work is excellent, and he may be willing to deal with shipping between the US and Australia. Roy

The orange wire was added by a previous owner to by-pass the corroded section of the level control/pot, and should not be there. That control is compromised. As part of any restoration of AR speakers of this era, the drivers should first be checked for functionality, then the pots fully restored or replaced before doing anything else. Based on your first photos in this thread, the tweeters should be replaced with something more appropriate. The tweeters in your photo will not provide anything close to the original sound. The mids' response will be close enough, and can always be dealt with at a later time. The back-wired mid on the left in your photo is a later AR replacement, and the one on the right appears to be original to the era. To answer your early question, there is no way to tell the higher impedance AR-5 mid from the lower impedance 3a mid without measuring resistance (DCR), but the chances are good that your mids are both satisfactory. Roy

There seems to be a bit of mythology forming around the Mundorf cap. My experience and measurements have never shown it to be superior to similar decent npe caps (such as those offered by Parts Express, Bennic, and MDL). On the other hand, the now-defunct Erse npe cap did prove to be clearly inferior.

The 33's look great, Norm! Hey, I still have one of those radios living in the kitchen (attached photo). I rarely turn it on these days, but it is where it lives. Roy

Based on what? Audio forums are full of subjective testimonials. You are also not taking the crossover into account. Cartridges are not the integration of disparate drivers, which is why speakers are referred to as "systems". The 3a was not known to have a more detailed midrange. In fact, in the early 70's Consumer Reports magazine subjectively rated the 2ax as "a better speaker at half the price" based on midrange response alone. Dome drivers are considered to have better dispersion, not more detail. The 3a drivers could also handle much more power. "And keeping (resurrecting?) the AR “sound” is a moving target; what was the sound when the speaker was first manufactured? Who really knows?" Those of us who have worked with these speakers for 4+ decades do. You obviously have an idea as to how they should sound...so have at it. Just know that you are basically attempting to re-design them. You certainly would not be the first. It can be fun to discuss....in the mods and tweaks section.

This is because the HiVi tweeter (and associated inductor) is meant to emulate the original when it is not available or is damaged. It was never meant to be an "upgrade". (Bear in mind that this site is primarily oriented around restoration.) I agree with Aadam's comments above, so I'll just add some of my own. Sensitivity, other electrical and (often overlooked) mechanical characteristics of individual drivers, crossover design/integration with other drivers, outboard enhancements such as equalizers and tone controls all significantly influence what you are generalizing as "detail". Simply dropping a more expensive (or favorite) driver into the cabinet hole of an existing design and believing it to be perfect for that system's crossover seems a bit naive, imo. On the other hand, I'm sure it is understood that your own satisfaction is the only thing that matters. Now, off to the mods and tweaks section with you!😁

Bill, Have you ever heard the AR-3a? You really should post your project(s) in the mods and tweaks section of the forum Roy

Interesting...Variations in cone mass or construction would have a greater impact on response than .2 ohms dcr (which is not very much). Roy

Hey Jessi, I have worked with both woofers, but don't recall noticing a difference. I never, however, did a direct comparison between the two. Before assuming there is an actual difference, I would try a couple of things if you haven't already done so: -listen with the amp channels reversed. -listen to the woofers without the tweeters connected. -switch woofers to opposite cabinets. -remove woofers and compare resistance and inductance. Roy

Do some measurements and let us know the results. The tacky butyl materiel was also used on a number of tweeters (not AR) over the ages.

Agreed...Not to mention the risk of damage via shipping.

Nice project, Norm. On the surface it all makes sense. The larger ported cabinet would explain the difference in the character of the bass response, and an additional 4 ohms of series resistance with the tweeter would have a noticeable effect on the midrange response.

The sealant is not at all "thick" nor is it "messy" if properly applied. In fact, it is deliberately very thin to act as a supplement to the original (which did not magically go away). It remains tacky so it will not form an additional membrane, which has the potential to affect performance by altering mass and compliance. The high percentage of toluene in it can also serve to loosen any hardened original sealant. As for not liking the way it "looks"...well these are, after all, AR speakers. Eye of the beholder, etc.:). Much time and measurement (primarily Fc and Fs) went into developing the formula, along with some information from Roy Allison (through Tom Tyson). It should also be noted that much experimentation was conducted with various membrane-forming materials beforehand. Roy

Yes

No...primarily because it wouldn't be able to compensate for the difference in capacitance. Besides, a toggle switch arrangement is more maintenance-free than any variable potentiomemeter (like an L-pad). Imo, there is no getting around removing the components connected to the old corroded rotary switches in order to proceed. It should be noted that AR finally eventually went to toggle switches after the troublesome potentiometer era.

We need to back up, Norm...I only mentioned the L-pad in reference to Jessi's illustration of by-passing the 7.5 ohm resistor, not replacement of the switch's 3 circuit options. The switch is providing a choice between 3 different circuits. As I said above, I only used the L-pad as a replacement for the 7.5 ohm resistor after "opting" for the "normal" position. I did completely remove the switch, but rebuilt the crossover up to the 7.5 ohm resistor. The L-pad was just an enhancement of the normal circuit. I essentially eliminated the "increase" option while providing the ability to variably attenuate the "normal" circuit to that of the original "decrease" position. Unfortunately, If you want to retain the original increase/decrease/normal configuration a switch is necessary. I still like the reliable 3-way toggle used in the 17. Roy

I recommend replacing the rotary switch with a 3-way toggle switch. The rotary switch of the 33 is the same as that used in the 23 and 5 and was not nearly as reliable as the 3-way switch of the KLH 6, 17, etc...which is a standard on/off/on single-pole/double-throw type. In fact I think I still have some nice used KLH originals in the parts bin someplace. On the other hand, Jessi's recommendation regarding the elimination of the switch is a simple solution and would work fine. I personally prefer the normal position for both the 17 and 6. I once eliminated the rotary switch, opting for the "normal" circuit in the schematic Jessi posted above, but Instead of by-passing the 7.5 ohm resistor I replaced it with the series leg of an 8 ohm L-pad. This allowed me to vary the resistance from 0 to 8 ohms. It was fun, but certainly not necessary. Roy

...along with many other similar, popular, speakers. I'm trying to figure out what "aluminum *anything*" could possibly do to "color" the sound. Roy

In what way? What exactly did you "scope"? Any identifiable differences are likely due to the behavior of electrolytic capacitors vs film capacitors (in this case, Dayton). The original Sprague capacitors were very well made electrolytic capacitors. Some years ago Ken Kantor (design engineer with AR) suggested that modern electrolytic capacitors sold by reputable speaker parts retailers are good replacements when necessary, and are technically closer to original spec than (any) film capacitor for these old speakers.