AR-2a tweeter replacement

[kcbluesman]

Hello. I've got a pair of AR-2a's with the older tweeter (orange dome). I restored these speakers some time back, and really like them....enough, in fact, that they replaced a pair of AR-5's that I'd owned for quite some time.

Anyway, I'm thinking about replacing the tweeters with the HiVi's due to the fact that their output - especially one of them - has declined so much with time. Given the very low resistance of these tweets, can anyone tell me what the proper modification to the crossover would be to use the HiVi's?

Thanks!

[kcbluesman]

Wow...with all of the discussion and work regarding use of the HiVi tweeters in other versions of the large AR's, I would have thought that someone used them with the 2a's. Anybody?

[pstrisik]

Wow...with all of the discussion and work regarding use of the HiVi tweeters in other versions of the large AR's, I would have thought that someone used them with the 2a's. Anybody?

I just installed them in 2ax'. Is it the same original tweeter?

[JKent]

2a and 2ax used different tweeters. The 2a tweeter is the same as the AR-3 (but not the 3a). I'm thinking the Hi-Vi should work but Roy is the expert on this so let's see if he chimes in.

Kent

[Steve F]

Actually, the 2a and the "old" 2ax used the same tweeter, which was the AR-3 tweeter. This was the 1 3/8" original "fried egg" tweeter.

The "new" 2ax used the 3/4" hard dome, the same as the 5 and (except for the impedance) in the 3a.

Steve F.

[kcbluesman]

I could certainly follow the instructions for using the HiVi's in other versions of the AR large cabinet speakers - in fact, I've used them in a set of LST2's I restored several years ago - but before doing so I was hoping to get input from one or more of CSP's resident AR restoration experts

To be clear...I've asked the question because of my understanding that the impedance of the 2a tweeter is quite a bit lower than the HiVi "replacement" (and lower than other iterations of the large-cabinet AR tweeters). Assuming that this is the case, I would think that it will be too loud relative to the mids and woofers without some sort of modification to the crossover (a modification different than the "standard" inductor). Frankly, I don't mind if the resposne of the HiVi's goes a bit higher than the original tweeters, but I do want to keep itheir output and their relationship with the other drivers fairly close.

[pstrisik]

I could certainly follow the instructions for using the HiVi's in other versions of the AR large cabinet speakers - in fact, I've used them in a set of LST2's I restored several years ago - but before doing so I was hoping to get input from one or more of CSP's resident AR restoration experts

To be clear...I've asked the question because of my understanding that the impedance of the 2a tweeter is quite a bit lower than the HiVi "replacement" (and lower than other iterations of the large-cabinet AR tweeters). Assuming that this is the case, I would think that it will be too loud relative to the mids and woofers without some sort of modification to the crossover (a modification different than the "standard" inductor). Frankly, I don't mind if the resposne of the HiVi's goes a bit higher than the original tweeters, but I do want to keep itheir output and their relationship with the other drivers fairly close.

I didn't do any crossover mod with the HiVi in 2ax'. There are the rheostats for some control. I do have the new tweeter somewhat below the midpoint and midrange somewhat above. But, in the end, the speakers are very balanced.

Perhaps modding the crossover could offer a different, maybe more original sound quality, but I have no idea if that's true.

[RoyC]

I could certainly follow the instructions for using the HiVi's in other versions of the AR large cabinet speakers - in fact, I've used them in a set of LST2's I restored several years ago - but before doing so I was hoping to get input from one or more of CSP's resident AR restoration experts

To be clear...I've asked the question because of my understanding that the impedance of the 2a tweeter is quite a bit lower than the HiVi "replacement" (and lower than other iterations of the large-cabinet AR tweeters). Assuming that this is the case, I would think that it will be too loud relative to the mids and woofers without some sort of modification to the crossover (a modification different than the "standard" inductor). Frankly, I don't mind if the resposne of the HiVi's goes a bit higher than the original tweeters, but I do want to keep itheir output and their relationship with the other drivers fairly close.

First of all, a tweeter with a higher rated impedance or dcr would not be expected to play "louder" than one with a lower impedance. All things being equal it is the other way around. At any rate, it is a non-factor in this case.

As Steve stated above, the AR-2a and early 2ax use the same, larger orange dome tweeter with a (low) dcr of 2 ohms, and the later 2ax uses the black 3/4" dome tweeter with a dcr of around 6 ohms...yet they ALL use the same crossover caps in the tweeter/mid circuit. The HiVi Q1R's dcr is 5.5 ohms. As you know, even though the Q1R has almost the same dcr as the later (2ax/5/LST2) tweeter, a crossover modification is still required to integrate it. The reason has more to do with differing mechanical properties of the various tweeters, not rated impedance or dcr. The level controls easily deal with resistance issues and level matching. (As an aside, only the series leg of the dual midrange pot is used in the AR-2a. The dcr of the AR-2a's parallel dual mids is also around 2 ohms...vs 6 ohms for the AR-2ax mid)).

The bottom line is the HiVi Q1R will work as well with the 2a as it does with both versions of the 2ax, AR-5, and AR-3a. Use the "standard" .05 mh parallel coil and replace the 4uf cap with a 2.5 to 3uf cap to get it into the original ballpark. Make sure the level controls are in good working order.

Roy

[pstrisik]

Roy, Would there be any difference in sound quality between 1) change out the cap and 2) not change cap / control level with the level controls? I'm trying to decide if it is worth changing that cap value or leave it as is.

Thanks.....Peter

[RoyC]

Peter,

Some people prefer the stronger output provided by the HiVi tweeter with the original cap, and others don't. The upper midrange is more pronounced with the HiVi tweeter/original cap combo. This is true of the other AR models as well. The higher the volume, the more it can be noticed.

If the goal is to get as close as possible to the original sound it is advisable to reduce the tweeter cap value. If you are inclined to do so, it is worth experimenting to determine your own preference, but there is no reason to dig into your speakers if you are happy with them as they are.

Roy

[pstrisik]

Peter,

Some people prefer the stronger output provided by the HiVi tweeter with the original cap, and others don't. The upper midrange is more pronounced with the HiVi tweeter/original cap combo. This is true of the other AR models as well. The higher the volume, the more it can be noticed.

If the goal is to get as close as possible to the original sound it is advisable to reduce the tweeter cap value. If you are inclined to do so, it is worth experimenting to determine your own preference, but there is no reason to dig into your speakers if you are happy with them as they are.

Roy

Thanks Roy, I'll make it a "maybe sometime" project! .......Peter

[kcbluesman]

First of all, a tweeter with a higher rated impedance or dcr would not be expected to play "louder" than one with a lower impedance. All things being equal it is the other way around. At any rate, it is a non-factor in this case.

Roy

Yes, of course...I twisted up my statement. My concern was that the original tweeter would be louder than the replacement, given the difference in impedance.

Thanks for the guidance regarding appropriate crossover modifications for the 2a.

On a related note....what would be the impact/effect of 1) not adding the coil, as I assume is pstrisik's case, and 2) using a coil of higher or lower inductance?

[pstrisik]

Yes, of course...I twisted up my statement. My concern was that the original tweeter would be louder than the replacement, given the difference in impedance.

Thanks for the guidance regarding appropriate crossover modifications for the 2a.

On a related note....what would be the impact/effect of 1) not adding the coil, as I assume is pstrisik's case, and 2) using a coil of higher or lower inductance?

I do have the coil on the tweeter. I just didn't change the cap in the xover.

[pstrisik]

Roy, Carl, et.al.,

I'm thinking I will go ahead and replace the tweeter cap. My 2ax' now have the HiVi tweeters with the inductors (a la Roy) and the caps are replacements I obtained from Carl for the original restoration. Without opening it up, I'm reading that I have a 4mfd cap for the tweeter and should replace it with a 2.5-3 mfd to better replicate original sound. I read through a bunch of threads and looked at caps on Madisound, and I feel like I know less than when I started! Caps made from different materials (poly is brighter but lasts longer?), different voltages, ClarityCaps has different lines (ESR, MR, SA, etc. lines). Anyone have a specific recommendation for a pair of tweeter caps I could go with?

Thanks..... Peter

[kcbluesman]

I do have the coil on the tweeter. I just didn't change the cap in the xover.

Ahh, so you did make some modification to the crossover...just not the cap. Thanks!

[RoyC]

Yes, of course...I twisted up my statement. My concern was that the original tweeter would be louder than the replacement, given the difference in impedance.

Thanks for the guidance regarding appropriate crossover modifications for the 2a.

On a related note....what would be the impact/effect of 1) not adding the coil, as I assume is pstrisik's case, and 2) using a coil of higher or lower inductance?

KC,

I had a feeling you mixed it up....Anyway, stated another way, due to significant mechanical differences most modern tweeters will have greater output than these original AR tweeters, regardless of rated impedance or dcr.

The purpose of the coil is to electrically cut off the (much) greater lower frequency response of modern tweeters. Not using the coil would produce an unbalanced midrange response, and at the very least, result in sound much different than the original. The larger the parallel coil value, the greater the lower frequency response of the replacement tweeter. The series crossover capacitor has the same effect on the tweeter's response. Varying one or both components will electrically vary the crossover frequency and slope as it interacts with the unique mechanical characteristics of each tweeter, and the rest of the system.

These variables become very complicated in the world of speaker design, which is why successful professional designers and engineers like Ken Kantor receive the respect they deserve. Our relatively simple implementation of the affordable, easy-fitting HiVi Q1R is an attempt to approximate the original AR sound in the absence of original tweeters, with a minimal amount of electrical and carpentry skills. Playing around with coil and cap values (AND other tweeters) can still be fun and interesting for the adventurous. The suggestions I make in this regard are based on personal experience, feedback from other AR enthusiasts, and Ken Kantor's suggestions (which were made some years ago relative to the AB Tech replacement tweeter). Forum member, Carlspeak, has also provided much insight by providing practical experience and measurements.

Sorry for the bloated response to your question, KC, but it was a good opportunity to post this stuff.

Roy

[JKent]

I'm thinking I will go ahead and replace the tweeter cap. ...

I'm reading that I have a 4mfd cap for the tweeter and should replace it with a 2.5-3 mfd to better replicate original sound. I read through a bunch of threads and looked at caps on Madisound, and I feel like I know less than when I started! Caps made from different materials (poly is brighter but lasts longer?), different voltages, ClarityCaps has different lines (ESR, MR, SA, etc. lines). Anyone have a specific recommendation for a pair of tweeter caps I could go with?

Peter,

Stop reading!

The world of capacitors can be daunting/confusing/maddening. Asking which cap is best is like asking which religion is best.

Having said that, you want a film cap. Any brand film cap.

If you are shopping at Madisound, I would recommend the 2.7uF Panasonic Surplus Caps--a bargain at 30 cents each. In fact, if you send me a PM I'll send a pair for cost + 1st class postage. The Clarity Caps are good quality but why spend that much dough? But if you do spring for them I'd go for the SA. It's a higher quality than the PX but is currently on closeout sale at Madisound for a lower price ($3.95 ea). If you want to fine-tune it, you could also get a pair of Bennic PMT 0.22uF or 0.33uF caps to try in parallel with the 2.7 (personally I doubt you will hear a difference).

Kent

[pstrisik]

Peter,

Stop reading!

The world of capacitors can be daunting/confusing/maddening. Asking which cap is best is like asking which religion is best.

Having said that, you want a film cap. Any brand film cap.

If you are shopping at Madisound, I would recommend the 2.7uF Panasonic Surplus Caps--a bargain at 30 cents each. In fact, if you send me a PM I'll send a pair for cost + 1st class postage. The Clarity Caps are good quality but why spend that much dough? But if you do spring for them I'd go for the SA. It's a higher quality than the PX but is currently on closeout sale at Madisound for a lower price ($3.95 ea). If you want to fine-tune it, you could also get a pair of Bennic PMT 0.22uF or 0.33uF caps to try in parallel with the 2.7 (personally I doubt you will hear a difference).

Kent

Thanks Kent. I wasn't necessarily looking for a recommendation for the best cap - looking at least for an appropriate cap. So many options I had no idea what to order.

.......Peter

[kcbluesman]

Sorry for the bloated response to your question, KC, but it was a good opportunity to post this stuff.

Roy

Actually, your response explains exactly what I wanted to understand. As always, thanks!

I'm still a bit on the fence about replacing these tweeters....I really hate to do it. I put many hours into bringing these speakers back from the dead (from both a cosmetic and operational standpoint). But it's quite clear that one of the tweeters is fading. I've thought about replacing them with other originals, but it seems to me that at their age (over 50 years old!) I am likely to be facing the same issue again in the near future. In any case, these speakers will stay with me for the long run.

I've just completed a major purge of my "collection", keeping only the speakers that are in regular use. As noted in my earlier post, it was between these and my AR-5's for a spot in my workshop. The 5's are probably a better all-round speaker, but the 2a's had much more of my blood, sweat and tears in them...and I love the funkiness of the midrange arrangement, the masonite spacers on the woofers, the historical tweeter and the stick-pin "a" badges. Of all my "classic" AR speakers, the only one left now are these 2a's, a set of AR-4x's and set of AR-6's. Somewhat surprisingly (to me), I ended up keeping three pairs of early KLH's as well (Five's, Sixes and 23's). On a related note...I sometimes run the AR-2a's and the KLH Sixes simultaneously....they sound very, very good together.

Again, thanks to Roy and thanks to the CSP community.

[RoyC]

I'm still a bit on the fence about replacing these tweeters....I really hate to do it.

If I were you I would keep the old tweeters going as long as possible, especially if the speakers are not exhibiting any obvious problems. Most issues with the orange dome tweeter can still be resolved.

...can't argue with your selection of KLH models. I like 'em too!

Roy

[kcbluesman]

If I were you I would keep the old tweeters going as long as possible, especially if the speakers are not exhibiting any obvious problems. Most issues with the orange dome tweeter can still be resolved.

...can't argue with your selection of KLH models. I like 'em too!

Roy

Thanks!

What are the likely reasons for the decline in output from the 2a tweeters, and what can be done about it? The pots are in good shape, with no dead spots and just a bit of "crackliness" in a few spots. The caps have been replaced and I've re-soldered all of the crossover connections. I've NOT had the tweeters out, as I try to avoid messing with these front-wired units as much as possible. I'll post some pics of them tomorrow, for what it's worth.

By the way, I've been following a thread over on AK regarding a set of KLH 28's that a fellow found and is now restoring. I've never seen a pair in the flesh but from the pics they look like KLH's version of the LST models.

[RoyC]

Thanks!

What are the likely reasons for the decline in output from the 2a tweeters, and what can be done about it? in the flesh but from the pics they look like KLH's version of the LST models.

The usual issues are:

-broken or oxidized aluminum leads...special solder required to extend leads with tinned copper leads after removing oxidation.

-reduced sensitivity due to stiffened suspension...solvent required to remove some of the old rubber compound. (I use toluene.)

-foam suspension "blob" detached from dome...re-glue without getting glue into the voice coil gap.

-popped/raised dome due to complete separation of the suspension foam... not an easy fix.

If the tweeters sound OK, don't disturb them.

Roy

[kcbluesman]

Both still sound ok, other than the fact that one of them has noticeably lower output. To isolate, I turned down both pots and listened to the woofers alone....both speakers sound just about alike. Turned up the mids, same thing, Turned off the mids, turned up the tweets. This is where the reduced output from one vs the other becomes most obvious. WIth pots at my usual settings (95% on tweets, 60% on mids), it is quite a bit less noticeable...although if I shift the balance from full right to full left, the difference in tweeters gives one speaker a noticeably different character than the other....a bit duller, less defined.