AR2ax tweeters

[Carlspeak]

Carl

Carl's Custom Loudspeakers

This is an open question to the classic AR experts who frequent this site. I'm contemplating substituting a later (earlier) vintage1 3/8 inch tweeter for thr 3/4 size. It looks like physically, it can be done. I just don't know if the crossover need some tweaking to compensate for the 1 3/8" size.

Help!

Carl

[charger3834]

I don't Know Carl, I'm sure it's possible but why would you want to do that ?

The old 1 3/8" tweeter operated with a 7500 HZ crossover instead of the 5000 HZ crossover of the 3/4" version. The older version has somewhat inferior dispersion characteristics and acoustic power response. It is also a little less efficient.

[dynaco_dan]

>

>Carl

>Carl's Custom Loudspeakers

>

>This is an open question to the classic AR experts who

>frequent this site. I'm contemplating substituting a later

>(earlier) vintage1 3/8 inch tweeter for thr 3/4 size. It looks

>like physically, it can be done. I just don't know if the

>crossover need some tweaking to compensate for the 1 3/8"

>size.

>Help!

>Carl

Hi Carl;

First off Carl, I am not an expert.

If you want to just do it, for the sake of trying it out, that would probably be interesting reading your opinion of the results.

I don't know what the 1 3/8" tweeter output is, if at all, at the lower 5khz crossover frequency.

There may not be output or it may be much lower than with the 3/4" model.

You quite probably would have to change the tweeters capacitor.

There would be less dispersion, lower power handling capabilities, possibly lower output and maybe even less clarity.

If you are just wanting to experiment please let us know your results.

The earlier 1 3/8" tweeters had aluminum wires so you may have come across the brass posts that were used to connect them to the leads inside the enclosure.

They would wrap a few turns around the post and push the spring loaded plunger down to bite into the aluminum wire.

Surprisingly, I found the posts, chrome plated though, still listed in a parts catalog recently.

Normally you can't solder aluminum wire to copper wire so these mechanical clamps worked back then.

Perhaps with extreme care, cleaning the aluminum leads and the copper leads, maybe the 2 part epoxy, silver based is supposed to be conductive.

This might do if the aluminum wires are short and you wanted to add some tinsel to make the leads longer.

I have an old piece of Sears aluminum solder bar that must be 50 years old.

Just on the opposite side of the coin what would happen if one was to replace an old AR-3 1 3/8" tweeter with a 3/4"?

Oh no!

What have I started now!

Yikes!

Good luck with your idea, Carl.

[Carlspeak]

Carl

Carl's Custom Loudspeakers

Thanks Vern for the insights regarding the 1 3/8 inch aluminum wires. I recently removed them from some dusty AR2ax boxes and sure enough, the wires broke when I removed them from those brass posts.

Funny thing though, I've seen those 1 3/8" tweeters on AR3a pics shown on this web site and, I've attached a picture of an AR2ax currently for sale on e-Bay at:

http://cgi.ebay.com/vintage-ar-2ax-speaker...1QQcmdZViewItem

. It's got the same tweeters I want to use. Couldn't it be possible AR actually made some 2ax's with these 1 3/8 tweeters???

I agree, a capacitor change may be necessary. I'm not as concerned about efficiency since the pots are designed to compensate for this. I'm considering getting a larger cap (maybe 8 or 10 microfarad) assuming these larger domes usually can take a lower xover point. Maybe someone has 2ax's with those larger tweeters and knows what caps are in there?

[dynaco_dan]

>

>Carl

>Carl's Custom Loudspeakers

>Thanks Vern for the insights regarding the 1 3/8 inch aluminum

>wires. I recently removed them from some dusty AR2ax boxes and

>sure enough, the wires broke when I removed them from those

>brass posts.

>

>Funny thing though, I've seen those 1 3/8" tweeters on AR3a

>pics shown on this web site and, I've attached a picture of an

>AR2ax currently for sale on e-Bay at:

>http://cgi.ebay.com/vintage-ar-2ax-speaker...1QQcmdZViewItem

>. It's got the same tweeters I want to use. Couldn't it be

>possible AR actually made some 2ax's with these 1 3/8

>tweeters???

>I agree, a capacitor change may be necessary. I'm not as

>concerned about efficiency since the pots are designed to

>compensate for this. I'm considering getting a larger cap

>(maybe 8 or 10 microfarad) assuming these larger domes usually

>can take a lower xover point. Maybe someone has 2ax's with

>those larger tweeters and knows what caps are in there?

>

>

Hi Carl;

I believe I was wrong with the capacitor change.

Or that I was at least premature.

If you remove a 3/4" AR-3A tweeter the crossover will be above 5khz.

The AR-3 4 ohm 1 3/8" tweeter is above 7.5khz.

I don't know what will happen to the 1 3/8" tweeter with the lower crossover frequency.

I am sure someone else will be along soon with this answer.

There may be a void between 5 & 7.5khz, or resonance, or far worse, maybe damage.

Can we hear this?

I don't think you saw a 1 3/8" tweeter in a AR-3A speaker.

You would definitely have seen one on a AR-3, 2, 2A, or 2AX (earlier model), although the 2 series were 8 ohms versions of the same size tweeter.

Because the 3 series is 4 ohms and the 2 series is 8 ohms I believe they will use different value caps.

In regards to the pots, I believe you were advised by someone else that the efficiency would be less, not more.

By doing the mods with the 3/4" 4 ohm into an AR-3, I gather from all that I understand now, that the tweeter pot may be needed in that application as the tweeter would be then more efficient.

I have seen on ebay, the 1 3/8" and 3/4" tweeters wrongly advertised for replacements for both 4 and 8 ohm series.

When the mood moves me to suggest the correct information to the seller, the advice so far, seems to be well received.

Like I say, I am not an expert, Carl.

Still looks interesting though.