Evaluate this hypothetical 3a rejuvination project

[mantis]

Howdy!

I want to get these things into a state so that I don't have to worry about them causing problems and cost at any moment (the tweeters).

I LOVE the tweeters, I love how it sounds as is... even with unchanged caps, these things sound amazing... but every time I turn them on I dread a pop or something that could fry the tweeters. I just don't like the anxiety or thought of having to blow 100 bucks at least each and having to wait months between being able to use them... You get it, I think a replacement would be a preferable option.

Now, I am pretty confident that the mid ranges last a long while and these sound great as is, so no need to swap them (right?).

So, using replacement tweeters that will be safer are the goal. This will entail a new crossover, that I need to do anyway.... so I figure I should do it all at once and not have to change the crossover later. My questions are: Is the tweeter replacement, but leave mid, a good idea? Or should I just replace both if I am to replace them anyway?

Next is, concerning the particular tweeters, which should I look at? I guess I can spend a little bit of money on each if they are to last me and sound good.... not hundreds of dollars each, but I don't need to select an inferior model due to a 20 or 50 dollar difference in cost... you know.

So how should I do this? Tweeters only and just the new crossover, or tweeters and mids while doing crossover too? I am just really concerned about the tweeters, I can't afford to buy replacements all the time... it hasn't happened yet, but I know it will happen some day.

Thanks for any input.

[Mexicomike]

Recap them as per the AR3 paper on this site and don't worry about them, enjoy them!

[JKent]

Recap them as per the AR3 paper on this site and don't worry about them, enjoy them!

I agree with Mike. And don't do ANYTHING until you download and study the excellent Restoring the AR3a booklet:

http://www.classicspeakerpages.net/_Media/...the-ar-3a-2.pdf

But if you MUST... the subject of replacing the tweeter is thoroughly covered in the guide.

Kent

[dynaco_dan]

Howdy!

I want to get these things into a state so that I don't have to worry about them causing problems and cost at any moment (the tweeters).

I LOVE the tweeters, I love how it sounds as is... even with unchanged caps, these things sound amazing... but every time I turn them on I dread a pop or something that could fry the tweeters. I just don't like the anxiety or thought of having to blow 100 bucks at least each and having to wait months between being able to use them... You get it, I think a replacement would be a preferable option.

Now, I am pretty confident that the mid ranges last a long while and these sound great as is, so no need to swap them (right?).

So, using replacement tweeters that will be safer are the goal. This will entail a new crossover, that I need to do anyway.... so I figure I should do it all at once and not have to change the crossover later. My questions are: Is the tweeter replacement, but leave mid, a good idea? Or should I just replace both if I am to replace them anyway?

Next is, concerning the particular tweeters, which should I look at? I guess I can spend a little bit of money on each if they are to last me and sound good.... not hundreds of dollars each, but I don't need to select an inferior model due to a 20 or 50 dollar difference in cost... you know.

So how should I do this? Tweeters only and just the new crossover, or tweeters and mids while doing crossover too? I am just really concerned about the tweeters, I can't afford to buy replacements all the time... it hasn't happened yet, but I know it will happen some day.

Thanks for any input.

Hi there;

The AR-3A is a great speaker, stock.

When a component in the crossover is bad, it needs cleaned up or replaced with the best option available at the time.

Each time the cabinet is worked on, there is a chance of cabinet, crossover or driver damge.

The woofers, both the alnico and the ceramic magnet versions, with a proper cabinet seal, will handle over 1,000 peaks, so they are very robust.

Please do nothing to test out this comment!

The midrange driver will handle considerably less power but still will far and away outlast the 3/4" dome tweeters.

I will ask my friend if he remembers how many mids he replaced over the years under warantee.

The tweeters are by far the weakest link in both the AR-3A and AR-LST speaker systems.

Don't worry about blowing an older one or a newer replacement tweeter, FUSE them.

AR recommended a 1 1/4 amp Bussmann FNM slow blow fuses for the AR-3A's, back in the old day's.

Perhaps 1 amp FNM would be a better choice today?

A Heathkit/AR equivalent speaker system had an enclosed fuseholder with a 3 amp AGC fast blow type fuse.

AR must have felt that it was adequate for the tweeter at least.

You might consider a single fast blow fuse for the entire speaker system at maybe 1 1/2+/- amp AGC open fuseholder type, instead.

Only a fast blow fuse will truly protect the tweeters, as best as possible at least, not the slow blow type.

AGC 3 was fine when the drivers were new and readily available, now the drivers are available only on the used market and they deserve to be respected more.

Idealy the different drivers should be appropriately separately fused but that is not practical without butchering somewhat the cabinetry.

Just my thoughts on this subject.

Vern

[RoyC]

So how should I do this? Tweeters only and just the new crossover, or tweeters and mids while doing crossover too? I am just really concerned about the tweeters, I can't afford to buy replacements all the time... it hasn't happened yet, but I know it will happen some day.

Thanks for any input.

Hi Mantis,

Given your enthusiasm for the original sound and concern for the drivers, I would suggest buying backup original drivers as the opportunities arise. Although there are acceptable approaches to replacing the original tweeter, they require crossover changes, and, for better or worse, will not sound exactly the same as the original. Changing the midrange driver is asking for real trouble. There are currently no "drop-in" replacements for any of the drivers.

Roy

[mantis]

hmm. The fuse approach would be acceptable if it would mean excellent security. Assuming that is the case, and the crossover is simply replaced with modern components (no changes), then what would be the appropriate fuse type for best protection of the tweeter if I only used a single fuse for the whole speaker?

[Carlspeak]

hmm. The fuse approach would be acceptable if it would mean excellent security. Assuming that is the case, and the crossover is simply replaced with modern components (no changes), then what would be the appropriate fuse type for best protection of the tweeter if I only used a single fuse for the whole speaker?

http://www.classicspeakerpages.net/library..._systems_1.html

[kimberley]

When worried about lending 'speakers (best advice - don't!) or fearing abuse on odd occasions I have used car lightbulbs as a protection device.

A 21w 12volt bulb in series with the loudspeaker has a resistance of about 0,5ohm when cold, but this rises with heat: higher power leads to increased resistance - effectively a 'compressor' or 'limiter'.

When input power rises, the bulb also glows, so you know what is going on; if high power continues or increases, the bulb will 'blow'.

The surprise, for me, has always been how rarely the bulb glows - we use a lot of power on transient signals, but remarkably little continuously.

With the 3-terminal wiring of AR-3a & AR-2ax 'speakers, it would be quite easy to use a 21w/5w double filament bulb to protect the bass (21w filament) & midrange+tweeter (5w) separately. Other values of bulb can be used as appropriate, dependant mainly on your local automotive trade counter stocklist. Bear in mind that the lower wattage bulbs have considerably higher cold resistance. (The 'luxury' answer is to bypass the bulb filament with a polyswitch).

I am not going to claim that this is a perfect solution to the problem of blown tweeters. If used permanently for critical listening the resistance of the filament must be considered as part of the crossover/potentiometer/L-pad calculation and yes, there will be some compression at high power output: that is what it is for!

It is, however, a cheap, easy & non-invasive (& fully reversible) way of buying peace of mind. You may even conclude that the lights come on so rarely that the tweeter is at less risk than you thought...

Adam Kimberley, London, U.K.

[onplane]

I want to get these things into a state so that I don't have to worry about them causing problems and cost at any moment (the tweeters).

I LOVE the tweeters, I love how it sounds as is... even with unchanged caps, these things sound amazing... but every time I turn them on I dread a pop or something that could fry the tweeters. I just don't like the anxiety or thought of having to blow 100 bucks at least each and having to wait months between being able to use them... You get it, I think a replacement would be a preferable option.

Lot's of good suggestions so far from fellow CSP'ers.

I would 2nd the notion of NOT changing anything. I would replace only if a driver fails.

Several folks have offered good ideas on how to protect those fragil tweeters. One new idea I would offer is passive bi-amping. Here you use a mid to low power amp to drive the mids/tweeters. Then a substantial amp to drive the power hungry woofers.

You can further minimize the chance of drving the tweeter amp into clipping by turning down the bass tone control.

The smaller amps with their significantly lower rail voltages rarely start with that huge "thump". Then by attentuating the fundamental frequencies (via the bass tone control), you can pretty much avoid the entire issue of clipping.

I power my AR-3a's with:

1. 170 wpc (rms measured) on the woofers

2. 30 wpc (rms measure on a good day) on the mids/tweeters

Regards,

Jerry

[johnieo]

Several folks have offered good ideas on how to protect those fragil tweeters. One new idea I would offer is passive bi-amping. Here you use a mid to low power amp to drive the mids/tweeters. Then a substantial amp to drive the power hungry woofers.

I respectively suggest that we cease all discussion of bi-amping speakers that were not designed to be biamped. These discussions are best carried on in the "Mods and Tweaks" Forum. The suggestion of bi-amping a three-terminal speaker is not new. People visit this site for advice on how to restore speakers properly and this kind of "advice," given to someone not versed in engineering, creates utter confusion. Here are comments I'm hearing off line:

* I have lost interest in posting.

* I rarely post anymore, as the flavor has changed.

* "---" gets a lot of business from confused TCSP readers.

Mark has spent significant resources in building a respected site; let's focus on maintaining that quality.

Cheers

[dynaco_dan]

I respectively suggest that we cease all discussion of bi-amping speakers that were not designed to be biamped. These discussions are best carried on in the "Mods and Tweaks" Forum. The suggestion of bi-amping a three-terminal speaker is not new. People visit this site for advice on how to restore speakers properly and this kind of "advice," given to someone not versed in engineering, creates utter confusion. Here are comments I'm hearing off line:

* I have lost interest in posting.

* I rarely post anymore, as the flavor has changed.

* "---" gets a lot of business from confused TCSP readers.

Mark has spent significant resources in building a respected site; let's focus on maintaining that quality.

Cheers

Hi John;

I will definitely agree that this type of AR non-supported information should be in the "Mods and Tweaks" forum.

In fact there should be a dedicated bi-amping topic there, kept on topic.

It should have drawings and warnings.

Up to and including the AR-LST, at least, AR did not provide the consumer with bi-amp information at all.

Possibly there was AR internal documents on that subject later but I am not aware of any.

I urge anyone even contemplating doing it to think carefully about the possiblity of touching two amplifier speaker hot leads together, even for a micro second.

Touching the ground leads together are not the problem but the hot leads may cause speaker damage, irrepairable damage to one or both channels of one or both amplifiers.

Heathkit AS-103/AS-103A which was their equal kit form of an AR-3A speaker system mentioned in their manual that the speaker could be bi-amplified and that was all.

Sadly it left anyone not familiar with that terminolgy in the dark about how to do it correctly.

Maybe Heathkit was not suppose to have mentioned that fact because of the different equipment out there in the field and possiblity of goof-ups.

At that time or maybe it was much earlier, possibly JBL I believe, made their amplifier with separate grounds which could not be connected together.

This is the only memory I have about a single amp with non-connectable speaker ground leads.

Can you imagine a pair of those new amps connected to a pair of new speakers and they all go up in smoke.

Not a pretty thought.

Vern

[mantis]

um ya, no bi-amping

I found fuses and a fuse holder (looks like utter sh!t, if someone could suggest a decent one I would appreciate it!), the rest of the crossover seems good to go (solen parts), except the 150uF cap... which seems not common. Is there a decent part that will work that you guys use, or, can other sizes be used... eg 140 or something?

Thanks.

[RoyC]

um ya, no bi-amping

I found fuses and a fuse holder (looks like utter sh!t, if someone could suggest a decent one I would appreciate it!), the rest of the crossover seems good to go (solen parts), except the 150uF cap... which seems not common. Is there a decent part that will work that you guys use, or, can other sizes be used... eg 140 or something?

Thanks.

Mantis,

Madisound sells 150uf Solen caps. You can also use 2 parallel 75uf caps.

Roy

[mantis]

Thanks for the tip Roy, they seem to have everything. Yikes kind of expensive! What about the inductors? Should those be replaced, or are they OK?

[JKent]

Thanks for the tip Roy, they seem to have everything. Yikes kind of expensive! What about the inductors? Should those be replaced, or are they OK?

You can use their Bennic 150 mfd non-polarized electrolytics. They're $3.10 each and should last another 20 years. No--you don't have to replace inductors. As Roy and/or John told me, it's just a coil of wire--it won't go bad.

Good luck

Kent