AR3a tweeters.

[frankmarsi]

Anyone out there with a good replacement for the LST tweeters. How about vifa, etc. Any suggestions would be greatly appreciated.

 

 

[dynaco_dan]

Hello there

First I think you meant to title this "AR3a tweeters", these are the same tweeters as used in the LST's.

Try ebay, there is every so often, front wired and back wired AR3a and LST 3/4" tweeters.

Don't buy the 8 ohm AR5 version tweeter unless you are prepared to epoxy or hot glue a 4 ohm 10w w-w resistor onto the magnet.

Don't buy AR3 tweeters, as they are really not compatible with the (lower crossover and power handling) of the LST's. What a shame. MMMMM

You would have to replace all 8 tweeters with the same exact model.

When this issue came up for me 10 years ago, Vifa was suggested as a brand.

Vifa, Dynaudio, Seas and maybe Scan. There is also Morel, etc.

A point of interest.

A lot of speakers are not 4 ohms but selling as 6 ohms now.

Be aware of this when shopping.

A 6 ohm tweeter will be lower in volume level in the LST's than a 4 ohm.

The contour can't compensate enough for this, I'm sure.

It would be nice if you could borrow and try out the tweeters before buying. Sort of a test drive.

These LST's are a very high quality speaker and great thought should be given before paying out any of your hard earned money on replacement parts. Try to keep with original AR drivers to maintain this quality where possible.

Once you mount the new tweeters, they are second hand, and have much lower re-sale value.

Hope this helps you.

Good luck.

>Anyone out there with a good replacement for the LST

>tweeteres. How about vifa, etc. Any suggestions would be

>greatly appreciated.

>

>

>See web site

>

>http://www.frankmarsi.CityMax.com/

>

>E-Mail: mailto:: FMARSI@earthlink.net

>

>

[RoyC]

I agree with Vern. That tweeter is unique, and after much searching, I have never found a "drop-in" replacement. It naturally rolls off much more quickly than modern day tweeters, including the AB Tech "replacements". Impedence, frequency response, and sensitivity differences in alternative tweeters will require crossover changes to maintain your speakers' original character. It doesn't make much sense to re-engineer these speakers unless forced to. Unfortunately the changes made to the AR tweeters (ie AR11) were significant enough to make it difficult to find replacements for the earlier models...Then there is also that big hole in the cabinet to deal with. Most tweeters today have smaller faceplates.

The replacement woofer (Tonegan) and midranges are not the same as those from that era either...used drivers seem to be the best bet at present if possible.

[dynaco_dan]

Hello again

Just as a matter of interest, there is in this site, a photo of a stack of LST and LST/2 speakers.

The person experimented as well as I remember.

He had Allison mids and highs in at least one enclosure. I believe these are 6 ohms as well.

He also doubled up with 2 woofers in one enclosure. It appears to be a single enclosure to me. Memory again. MMMMMMM

This is another possible option but impedance again and frequency response should be checked out.

If you had LST/2's then the Seas/Dyna 1 1/2" 8 ohm dome tweeter appears to have been discused on this site as being used.

If only Janszen 130 electrostatics were still being made, oh well.

How many tweeters are you in need of?

Good luck.

>I agree with Vern. That tweeter is unique, and after much

>searching, I have never found a "drop-in" replacement. It

>naturally rolls off much more quickly than modern day

>tweeters, including the AB Tech "replacements". Impedence,

>frequency response, and sensitivity differences in alternative

>tweeters will require crossover changes to maintain your

>speakers' original character. It doesn't make much sense to

>re-engineer these speakers unless forced to. Unfortunately the

>changes made to the AR tweeters (ie AR11) were significant

>enough to make it difficult to find replacements for the

>earlier models...Then there is also that big hole in the

>cabinet to deal with. Most tweeters today have smaller

>faceplates.

>

>The replacement woofer (Tonegan) and midranges are not the

>same as those from that era either...used drivers seem to be

>the best bet at present if possible.

[Pete B]

Hi Frank,

I see that people mention that this is nominally a 4 ohm tweeter, 2.75 Rdc, the same as that in the AR3a. This tweeter has had a reputation of being fragile, I've not seen specs for it, but it would be very interesting to see the input impedance, frequency response, and very important efficiency because if the efficiency is low then more power is required with heating and compression becoming a problem. I see that 4 tweeters are used in the LST in series-parallel so that the crossover loading remains 4 ohms. Two tweeters per panel causes vertical lobing, or poor vertical dispersion.

I would replace these old tweeters with a modern device with higher efficiency, Xmax, and power handling so that only one per panel is needed, 2 for the entire system. The replacements could be 8 ohms wired in parallel to retain the 4 ohm load to the crossover network. The crossover and old tweeter could be analyzed and modifications made to retain or improve the original voicing of the system. This 3/4" Scan Speak D2010/8513 would be my initial choice before doing the analysis: http://www.partsexpress.com/pe/showdetl.cf...tnumber=276-502

http://www.partsexpress.com/images/276-502m.jpg

Even the 1" tweeter with a 3/4" voice coil from the EPI series is much more robust being able to hanlde a very low crossover point, it would be coasting in the AR designs and is available, new, hand made. I would want to measure one first to see if there are any breakup modes below 20 kHz:

http://www.humanspeakers.com/index-d.htm

http://www.humanspeakers.com/diy/parts/images/002m.jpg

You asked for opinions and you got mine as food for thought. Some here seem to view every AR speaker as a museum piece, I don't, these are the Chevys of speakers if you ask me, not the Ferrari. I won't comment further on the use of an autotransformer (requiring a huge capacitor) where one is not really needed, pots where Lpads should be used, etc.

[Pete B]

Correction, just remembered that the tweeters in the LST are two horizontally front firing and one on each side. I'd probably go one for center fill and one front firing for typical home use and this idea of using 2 tweeters. Another alternative might be the tweeter from the 303 would have to see the specs.

[dynaco_dan]

Hello there

I just thought I'd throw my 3 cents more into the pot.

The LST's were and still are a very popular and very much in demand speaker system, albeit old and discontinued.

The original LST's used the front wired tweeters and mids and I'm guessing from the rear cabinet mounted crossover network.

The 3/4" tweeters were about 90 db sensitivity. They were considered quite inefficient at the time, until the big guys came along, Crowns, Phase Linears, etc. Now the speakers could be driven more cleanly.

The only way you can truly maintain an LST is to scrounge for used drivers.

If you choose to change tweeter brands you should at least use 4 ohm and 90 db sens.. This will give you the least variance from the originals.

Dynaudio tweeters would be my first choice for quality if I had the money and had to make the choice.

I would still have the patience to track down used front or rear wired AR tweeters on ebay, etc., before I would ever ruin an LST.

The LST is unique and by changing brands you will have changed the character of the speakers.

You will pay less and still have the LST's.

Approach an ARLST owner and say I own LST's but I changed out the tweeters to this brand and the mids to that brand. See what that person would say.

I've seen on ebay where someone has changed out their tweeter such as a Dynaco A25 with a Phillips tweeter.

Good luck again.

>Correction, just remembered that the tweeters in the LST are

>two horizontally front firing and one on each side. I'd

>probably go one for center fill and one front firing for

>typical home use and this idea of using 2 tweeters. Another

>alternative might be the tweeter from the 303 would have to

>see the specs.

[dynaco_dan]

>Hello there

>

>I just thought I'd throw my 3 cents more into the pot.

Hello again

Just re-read this topic and I have another 2 cents to throw in.

The 3/4" tweeter was not fragile in the power handling or dispersion area. I don't think 1000 watt peak capability is a weak speaker in construction design.

Maybe a metal screen glued or screwed over the tweeter would have kept some fingers off. I'm sure it would have had some sonic effect.

I see the domes of nearly ever speaker in some of the stores I go pushed in, and also on ebay the odd nipple dome.

When I see the realy bad ones on AR speakers on ebay, I usually email it to my brother saying someone found a new way of improving the dispersion characteristics of an AR tweeter.

You would also, in the case of LST, use 4 tweeters to obtain the better dispersion pattern and power handling characteristic not only 2.

FYI: In warantee repair I only ever saw one or more LST tweeters blown in an enclosure. In most cases all tweeters were blown. Mids and woofers seemed to go on forever, almost. The tweeters were the weakest link in their power handling capabilities.

Would you now go out and buy a pair of ARLST's off anyone now that you have more knowledge about speaker substitution.

Why would anyone wanting ARLST's pay for non-AR drivers?

One of my customer had a friend who gave him, yes, gave him his LST's for free because the woofers were rotten. When I saw them he had already bought and installed Radio Shack woofers for them and had thrown the originals away. MMMMMM I cried.

If you really love your LST's, you'll bend over backwards now to track down original drivers, I'm sure.

Good luck again with your choices.

>The LST's were and still are a very popular and very much in

>demand speaker system, albeit old and discontinued.

>

>The original LST's used the front wired tweeters and mids and

>I'm guessing from the rear cabinet mounted crossover network.

>

>The 3/4" tweeters were about 90 db sensitivity. They were

>considered quite inefficient at the time, until the big guys

>came along, Crowns, Phase Linears, etc. Now the speakers could

>be driven more cleanly.

>

>The only way you can truly maintain an LST is to scrounge for

>used drivers.

>

>If you choose to change tweeter brands you should at least use

>4 ohm and 90 db sens.. This will give you the least variance

>from the originals.

>

>Dynaudio tweeters would be my first choice for quality if I

>had the money and had to make the choice.

>

>I would still have the patience to track down used front or

>rear wired AR tweeters on ebay, etc., before I would ever ruin

>an LST.

>

>The LST is unique and by changing brands you will have changed

>the character of the speakers.

>

>You will pay less and still have the LST's.

>

>Approach an ARLST owner and say I own LST's but I changed out

>the tweeters to this brand and the mids to that brand. See

>what that person would say.

>

>I've seen on ebay where someone has changed out their tweeter

>such as a Dynaco A25 with a Phillips tweeter.

>

>Good luck again.

>

>>Correction, just remembered that the tweeters in the LST are

>>two horizontally front firing and one on each side. I'd

>>probably go one for center fill and one front firing for

>>typical home use and this idea of using 2 tweeters. Another

>>alternative might be the tweeter from the 303 would have to

>>see the specs.

>

[Pete B]

I understand where you're coming from, and in some situations I might agree with you. But with all due respect, I don't love any speaker. Since the poster asked I assume he's not too concerned about resale value and in fact this does not "ruin" the speaker. I consider these to be "end of life" designs, exact replacement parts are not available. I assume this person just wants his LSTs to be good sounding reliable speakers, perhaps he does not plan to sell them again. The substitution is non destructive if someone wanted to fish around for the correct drivers used they could do so at a later date. I heard from a very reliable source that the AR3a tweeter "poped" (burnt out) often, he said that's why they had quick release front wiring.

You say you'd rather see 4 - 4 ohm drivers, 90 dB sensitive, I'd estimate lower but I'll take your word for it. Here you go a Vifa with patented new technology, 2.8 ohm Rdc, 90 dB:

http://www.partsexpress.com/pe/pshowdetl.c...r=264-580&DID=7

http://www.partsexpress.com/images/264-580m.jpg

I'm somewhat interested in doing, LST, AR9, AR91 mods just to make them better than they ever were and just for the challenge.

[dynaco_dan]

Hello again I'm back

I don't know why they used front cabinet wiring on AR speakers.

It wasn't because of some design problem with their tweeters or their mid range drivers.

The quick release for the tweeter may be what was used for the AR3 tweeter which used aluminum wire for their voice coils.

It was a spring loaded post.

It was probably impossible for them to manufacture a rear wired connection and so continued on with the front mounted wires afterwards.

I was told that they went to inside connections as the europeans didn't like the exposed wires. Rumour?

I believe we are very gulible for what the manufactures said and what they pushed on us.

I remember asking Roy Allison about the new surround when they started using them.

There was no audible difference so I was led to believe.

I don't believe Roy or anyone else at that time knew about the rot to come.

Even grille cloths and AR turnatable mats to name a few objects other than the surrounds.

We accept the foam even today.

Built in obsolescence and future sales of repairs or replacement drivers or new speakers in total.

What are the British and Europeans still doing with neoprene and not dealing with our rot.

They build for durablity.

End of life is when we aren't able to buy equivalent drivers from ebay or other sources.

Yes, the time will come when you won't be able to find them on ebay but until that time it's worth the look.

I'm treating this post as if my son or your son was asking for advice.

The LST's are special to me as well as several other speakers I have.

We can encourage and support the contination of the original product for as long as parts, albeit used, can be found.

You use this site for your pleasure and relaxation as do I and all viewers.

Those that do leave comments add to the knowledge of newbies.

We have both spoken as to our feelings and have offered our opinions and advice.

I feel he can now make a much more informed decision and he still has choices as to which way he wants to go.

I wish I had help when I needed it when I was less knowledgeable.

Good luck again.

>I understand where you're coming from, and in some situations

>I might agree with you. But with all due respect, I don't

>love any speaker. Since the poster asked I assume he's not

>too concerned about resale value and in fact this does not

>"ruin" the speaker. I consider these to be "end of life"

>designs, exact replacement parts are not available. I assume

>this person just wants his LSTs to be good sounding reliable

>speakers, perhaps he does not plan to sell them again. The

>substitution is non destructive if someone wanted to fish

>around for the correct drivers used they could do so at a

>later date. I heard from a very reliable source that the AR3a

>tweeter "poped" (burnt out) often, he said that's why they had

>quick release front wiring.

>

>You say you'd rather see 4 - 4 ohm drivers, 90 dB sensitive,

>I'd estimate lower but I'll take your word for it. Here you

>go a Vifa with patented new technology, 2.8 ohm Rdc, 90 dB:

>

>http://www.partsexpress.com/pe/pshowdetl.c...r=264-580&DID=7

>

> http://www.partsexpress.com/images/264-580m.jpg

>

>I'm somewhat interested in doing, LST, AR9, AR91 mods just to

>make them better than they ever were and just for the

>challenge.

[Pete B]

Hi Vern thanks for your thoughtful reply and I generally agree with you.

Noticed your comment about Dynaudio, I also always thought that the Dynaudio D21AF looked very much like the 3/4" AR tweeter, I do have a pair but they're around 6 ohms and no longer available from US distributors. Perhaps something could be worked out, there might be a 4 ohm autosound version, and perhaps one of the distributors could get them.

I also just want to help, I lean towards making them what I view as a better speaker but respect those who want to retain the original frequency response and characteristic sound of the speaker. This might require a small level, impedance, frequency response compensating network between the crossover and a replacement driver and I would try to implement such a circuit so that it was easily removed if one wanted to go back to the original drivers.

On the other hand, if a person wanted a complete crossover upgrade, I would probably suggest fabricating a replacement and saving the old crossover.

Just trying to help here and I completely understand those who prefer keeping a speaker completely or as close to original as possible. I would like to learn more about this tweeter, as we did in the other thread for the Advent, and if someone has a dead one I'm willing to disect it to determine the physical characteristics however, reassembly might not be possible.

Would like to determine the following:

Coil height

Gap height

Former inside diameter

Coil outside diameter

Voice coil wire guage

Number of layers

Former material

Former length

Former thickness

Position of coil on former

Pole piece shaping

Pole piece diameter

Pole piece cavity?

Top plate inside diameter

Damping material under dome?

Grease or fluid of any kind?

Voice coil + former weight

Dome weight

Dome material

Dome thickness

Mounting plate OD

Mounting plate thickness

Required cutout diameter

I have hand wound voice coils and repaired voice coil wire breaks many years ago and this is also a possiblity as a last resort. Many times there's a common failure mode that can be eliminated. I hand fabricated this woofer voice coil many years ago:

http://members.aol.com/basconsultants/hand_vc.htm

http://members.aol.com/basconsultants/HAND_VC_WEB.jpg

Perhaps the person behind Human speakers would be willing to rebuild or offer a hand made AR tweeter replacement.

[RoyC]

Hey Pete, I would be very interested in your take on the original tweeter if you can get your hands on one.. It really doesn't have much output below its intended range without ANY crossover compared to a modern tweeter (or for that matter any of the others you mentioned....)

Its obvious that when the AR engineers were inventing these things they (hand)built the drivers to blend together with minimal filtering. How else do we explain that crazy looking midrange?

The physical characteristics of the tweeter, like the "3-blob-of-foam" suspension probably has alot to do with its unique character. No ferro-fluid was used until the AR11 which was when a tweeter similar to the current "replacement" tweeter was introduced.

Its probably going to take someone with your technical resources to figure out how to replace it at some point, without major design changes. (I've been following your work on the Advents).

As an aside, the walnut veneer is approx. 1/16 of an inch thick on these babies allowing them to be restored to very attractive, nice sounding furniture...with a retro character. There is value in that without them becoming museum pieces. I enjoy making them look and sound good again. It would cost alot today to have cabinets like that built.

A restored (not necessarily "souped up") 57 Chevy is still a thing of beauty and a joy to drive for some folks ....

So we need to get you some parts to dissect. They will be getting scarce and as worn out as old stereo buffs like me. I believe dogmeninreno (Dale) on this board mentioned he had some non-functioning 3a tweeters...

Roy

[Pete B]

Hi Roy,

Yes I think we're in agreement on most of this.

I have the 8 ohm version of the tweeter and it was clear from inspection that the blobs form a fairly stiff and probably not very linear suspension. This will give it a high Fs, which simply means that there's a 2nd order acoustical rolloff probably in the low kilohertz range which is higher than most modern tweeters. I do plan to measure this tweeter, no guarantees on when I'll get around to it.

I agree with you completely concerning the cabinets and I've done it myself but I used new drivers. It's all fine whatever each person prefers:

http://members.aol.com/basconsultants/klh_rebuild.htm

I also like old Chevys, was not knocking them, but usually when one is not perfect or worth restoring as a collectors item we relax about keeping it 100% original. Say we picked one up missing a motor and it was not worth restoring as a collectors item, many would not hesitate to put in a later small block V8 (bolts right in) rather than work so hard to find all the right, usually expensive, pieces for the exact original motor. I did this with a car from the 50's where it was nearly impossible to get even a motor of the same time frame, but the newer version of the motor bolted right in and replacement parts were readily available.

I would appreciate getting a tweeter to disect, and it might be possible to come up with some fairly simple solution.

Pete B

[RoyC]

OK Pete...looking forward to your research.

Those KLH 20's look great.

I got a kick out of the "tired" drivers comment. They mostly looked like that fresh out of the factory in those days.

It reminded me of one of my greatest speaker regrets. When very much younger I destroyed a pair of AR2ax's in previously perfect repair thinking I was going to improve them. Of course the motivation was having gotten a gander at those old "crude" looking drivers. I think I've been overcompensating ever since! They didn't sound bad when I was finished (I thankfully didn't trash the woofers) but, in my case, I should have waited for a pair "requiring a new motor"....

Roy

[Pete B]

"I got a kick out of the "tired" drivers comment. They mostly looked like that fresh out of the factory in those days."

Oh that's funny! I didn't even think of reusing the old drivers, didn't know about this site at the time.

"It reminded me of one of my greatest speaker regrets. When very much younger I destroyed a pair of AR2ax's in previously perfect repair thinking I was going to improve them. Of course the motivation was having gotten a gander at those old "crude" looking drivers. I think I've been overcompensating ever since! They didn't sound bad when I was finished (I thankfully didn't trash the woofers) but, in my case, I should have waited for a pair "requiring a new motor"...."

I wouldn't feel too bad, I won't get started about the AR2ax's but let's just say they're not my favorite. Do you still have your improved 2ax's?

[RoyC]

>I wouldn't feel too bad, I won't get started about the AR2ax's

>but let's just say they're not my favorite. Do you still have

>your improved 2ax's?

No Pete, they are long gone. This took place in the late 70's..They were subsequently stolen from the home of a friend who I had given them to. The thief probably wanted to return them when he realized they weren't AR's!

I had used Morel tweeters, Peerless mids and NO level controls, but had no clue how to make them better than they had been!

In those days I was just amazed at the bass response from those little speakers (in my opinion, better than the original Advents I also owned at the time)....

Destined to be "classics", "collector's items", Ebay hotties shipped to Asia in a world full of "subwoofers"...who knew?!

[Pete B]

"I had used Morel tweeters, Peerless mids"

Those sound like much better choices than the original drivers, you were off to a good start. You like 2ax bass better? Might match room gain better for certain speaker locations with it's higher Fc.

[Pete B]

I'd like to throw in 2 cents more here concerning the 4 ohm AR 3a versus the 8 ohm AR5 tweeter. People often speak of efficiency as dB/W/m and this is usually taken as one watt into the rated Z, 4 or 8 ohms. This is an interesting characteristic but what is more important for crossover design and driver replacement is voltage sensitivity usually given as dB/2.83V/m. A lower impedance driver such as the AR3a tweeter usually has higher voltage sensitivity as compared to the 8 ohm version. This makes it reasonable to add some series resistance, to bring both the impedance and voltage sensitivity back into the correct range. If we had all the data on the drivers the correct resistance could be calculated, or a compromise value to get the best match to input impedance and voltage sensitivity.

There's a 3/4" tweeter on sale at Madisound that is 6 ohms which is too high for the LST. But 4 in parallel will result in 12 dB higher voltage sensitivity and an input Z of about 1.5 ohms, a series resistance of 1 to 1.5 ohms will drop the voltage sensitivity and better ch the input Z to the crossover network. It's the Seas H586 (19TFF) 3/4" Fabric Dome tweeter $13.50 each: http://madisound.com/sale.html

[Pete B]

It's been noted for some time that there are problems with the early higher viscosity ferro fluids used in many tweeters probably well into the 1990s time frame. The problem is that the viscosity changes greatly with temperature and alters the damping and linearity. It also seems that the ferro fluid is nonlinear when it's cold. This was first reported by Linkwitz, as I understand it, where he observed it in Dynaudio tweeters that he was testing, see the links below.

This will be more of an issue with low crossover points and 1st order crossovers. The AR tweeters are crossed over very high but it's still worth checking in the ARs that use ferro fluid and any potential replacement. It's easy to remove from tweeters that have replaceable voice coil assemblies. Most of the better tweeters recently designed use a lower viscosity ferro fluid and do not seem to have this problem.

http://www.linkwitzlab.com/images/graphics/sb186-48.gif

http://www.linkwitzlab.com/images/graphics/sb186-50.gif

[RoyC]

While knocking around the Madisound site I noticed an inexpensive tweeter made by Hi-Vi Research (X-1R). Its impedance is below 4 ohms and the mounting flange is large. Both characteristics compatible with a possible Ar3a replacement tweeter. Its inexpensive enough to check out.

Roy

[Guest loudsubz]

I too am in the same boat. I recently picked up some new Pots for my ar3a's but would like to replace the tweeters. A couple of years ago the original tweets were blown so not knowing, we replaced them with some cheap generic Radio Shcak tweets that are 8 ohm. There very harsh.

I have been looking for awhile now for good replacements for the 3s but havnt seen many at all, and when I do there ridiculously priced, like $120 US for 1 driver. I dont care to ever sell these speakers, but would like to get them back to working condition to I can enjoy them.

[Pete B]

Hi Frank,

Just wondering how your LST repair turned out if you happen to check in here?

Regards, Pete B.

>Anyone out there with a good replacement for the LST

>tweeteres. How about vifa, etc. Any suggestions would be

>greatly appreciated.

>

>

>See web site

>

>http://www.frankmarsi.CityMax.com/

>

>E-Mail: mailto:: FMARSI@earthlink.net

>

>