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Acoustic Research LST-2 Speakers


Frank

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Hi

I have a pair of Acoustic Research LST-2 Speakers. They have been lying around in the lounge unused for a number of years. The red/black speaker terminals from the back on one of the speakers has come out, and the other is loose. Apart from that the speakers are in very good condition. Can anyone offer any advise about replacing this terminals. I have made inquiries from speaker repairers, but none seem interested in providing a quote!!!

Many Thanks

Frank

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The red/black speaker terminals from the back on one of the speakers has come out, and the other is loose. Can anyone offer any advise about replacing this terminals.

Hi Frank

If they look the same inside as mine (see picture) you can just screw in either the old or new terminals after removing the woofer.

The terminals are in the center of the picture with the green and the white wires attached.

ar_lst_2_crossover.jpeg

BRgds Klaus

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Hi Frank

If they look the same inside as mine (see picture) you can just screw in either the old or new terminals after removing the woofer.

The terminals are in the center of the picture with the green and the white wires attached.

BRgds Klaus

Hi Klaus and Frank

My guess why you are having difficulties getting a quote is, most service people today have never seen an AR-LST or AR-LST/2.

If you were to carry them both into a service station they would be better able to see what the issue is.

You will likely need to leave them and return at a later date to pick them up.

They would start up an invoice.

After completing their service of, removing, grille cloths, woofers and insulation and either tightening or replacing speaker terminals.

Upon completing that project they would need to test that all of the drivers function properly.

They would then need to re-install, the insulation, woofers, with new caulking perhaps, grille cloths and test the completed system.

You would then be facing possibly $5.00 - $10.00 in parts and 1 hour or more of labour.

Some of the members here have done similar, if not identical repairs/updates to their speakers.

I have never seen a physical pair of AR-LST/2's, but I suggest the following, if you are up to the challenge.

Remove your watch and credit cards first, before starting, because of the very massive magnetic field of these drivers.

You can, if you very patient and careful, complete this task at hand.

First lay the cabinet on it's back on a padded surface, perhaps straddling 2 tables.

Carefully remove the center grill cloth, they are fastened with Velcro.

All caution must be excercised that you do not accidently touch the woofers foam surround with anything during this work.

Also be very careful around the tweeter and mid drivers domes as they also have very strong magnets.

Gently pry the woofer basket up, much care required, more so with Mortite, than with foam gasket seals.

Note woofer leads colour and detach from woofer, either un-soldering or cutting just far enough away from the terminals

so that a later re-connection can be done easily.

This now allows you to turn the cabinet on it's top or bottom for easier access.

Be careful in laying it on it's front, not a good practice, for the tweeter and mid driver domes.

Repair or replace terminals, be certain they are fixed at 3/4" centers, or update them to dual gold plated banana plugs, should be less than $10.00.

Prior to re-installing the woofer you can decide if, refoaming the woofer is necessary and if it should be done.

Re-connect the woofer wires

Use an extremely low level signal or music to confirm they are functioning ok.

Re-install the insulation, be certain that the woofer protective backing sheet is still behind the woofer, re-putty the woofer gasket and re-install woofer.

This is also within the capabilities of members to do.

If the foam is mint then re-fasten the grille cloth and enjoy.

Cap replacement is another much discussed topic here, not just for the AR-LST/2 speakers.

If I missed or explained something incorrectly, another, more knowledgeable member will correct me and help you.

Good luck with your decision.

ps I just returned, 5 hours later, after supper and a visit to ebuy.

There is a pair of AR-LST-2 speakers there for sale.

I copied some photos of them, including the fusing area on the cabinet rear.

I see that there is just the two single terminals, red and black, and the two spring bronze, Bussmann FNM style, open fuse clips.

These terminals look like the same ones as Dynaco used in their classic speakers.

The view of the fuse clip back is blocked by the fuse being in it's proper position.

I do not have the ability to upload that photo for us to discus further.

Again I must caution you and all owners of the AR-LST and AR-LST-2 speakers, when those clips are soldered.

The clip ears are prone to break off at the area where the clip bends in the solder when too much pressure is used to insert or remove the fuses.

This probably from being soldered and the heat affects the temper.

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Hi Klaus

Many thanks for you reply and photograph. Is it a simple task of simply unscrewing the centre woofer, to get to the back of the speaker? What actually hold's the speaker terminals in place from the inside. If I connect speaker wires to the red/black terminals, and hold them in place at the back of the speaker with my hand, I get a sound.

Another member has very kindly given detailed instructions to carry out this task. A little bit complicated for me, but I have a friend who has experience of repairing amplifiers, so hopefully he should have no problem.

Regards

Frank

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Hi Klaus

Many thanks for you reply and photograph. Is it a simple task of simply unscrewing the centre woofer, to get to the back of the speaker? What actually hold's the speaker terminals in place from the inside. If I connect speaker wires to the red/black terminals, and hold them in place at the back of the speaker with my hand, I get a sound.

Another member has very kindly given detailed instructions to carry out this task. A little bit complicated for me, but I have a friend who has experience of repairing amplifiers, so hopefully he should have no problem.

Regards

Frank

it's just that easy. there are some nuts inside that hold them in place. I can't remeber if they're a #10 or #12 screw basically.

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Hi Klaus and Frank

My guess why you are having difficulties getting a quote is, most service people today have never seen an AR-LST or AR-LST/2.

If you were to carry them both into a service station they would be better able to see what the issue is.

You will likely need to leave them and return at a later date to pick them up.

They would start up an invoice.

After completing their service of, removing, grille cloths, woofers and insulation and either tightening or replacing speaker terminals.

Upon completing that project they would need to test that all of the drivers function properly.

They would then need to re-install, the insulation, woofers, with new caulking perhaps, grille cloths and test the completed system.

You would then be facing possibly $5.00 - $10.00 in parts and 1 hour or more of labour.

Some of the members here have done similar, if not identical repairs/updates to their speakers.

I have never seen a physical pair of AR-LST/2's, but I suggest the following, if you are up to the challenge.

Remove your watch and credit cards first, before starting, because of the very massive magnetic field of these drivers.

You can, if you very patient and careful, complete this task at hand.

First lay the cabinet on it's back on a padded surface, perhaps straddling 2 tables.

Carefully remove the center grill cloth, they are fastened with Velcro.

All caution must be excercised that you do not accidently touch the woofers foam surround with anything during this work.

Also be very careful around the tweeter and mid drivers domes as they also have very strong magnets.

Gently pry the woofer basket up, much care required, more so with Mortite, than with foam gasket seals.

Note woofer leads colour and detach from woofer, either un-soldering or cutting just far enough away from the terminals

so that a later re-connection can be done easily.

This now allows you to turn the cabinet on it's top or bottom for easier access.

Be careful in laying it on it's front, not a good practice, for the tweeter and mid driver domes.

Repair or replace terminals, be certain they are fixed at 3/4" centers, or update them to dual gold plated banana plugs, should be less than $10.00.

Prior to re-installing the woofer you can decide if, refoaming the woofer is necessary and if it should be done.

Re-connect the woofer wires

Use an extremely low level signal or music to confirm they are functioning ok.

Re-install the insulation, be certain that the woofer protective backing sheet is still behind the woofer, re-putty the woofer gasket and re-install woofer.

This is also within the capabilities of members to do.

If the foam is mint then re-fasten the grille cloth and enjoy.

Cap replacement is another much discussed topic here, not just for the AR-LST/2 speakers.

If I missed or explained something incorrectly, another, more knowledgeable member will correct me and help you.

Good luck with your decision.

ps I just returned, 5 hours later, after supper and a visit to ebuy.

There is a pair of AR-LST-2 speakers there for sale.

I copied some photos of them, including the fusing area on the cabinet rear.

I see that there is just the two single terminals, red and black, and the two spring bronze, Bussmann FNM style, open fuse clips.

These terminals look like the same ones as Dynaco used in their classic speakers.

The view of the fuse clip back is blocked by the fuse being in it's proper position.

I do not have the ability to upload that photo for us to discus further.

Again I must caution you and all owners of the AR-LST and AR-LST-2 speakers, when those clips are soldered.

The clip ears are prone to break off at the area where the clip bends in the solder when too much pressure is used to insert or remove the fuses.

This probably from being soldered and the heat affects the temper.

Hi Vern

Many many thanks for your reply and detailed instructions. A little bit complicated for me but I may take my time and give it a go, or enlist the help of a friend. If you can hear a sound coming from all the drivers, is that sufficient to assume they are all working as they should, or is there a way of testing them?

Regards

Frank

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Hi Frank

It is a very simple task of tightening two nuts after removing the woofer and the damping material, here is a magnified photo.

BRgds Klaus

Hi again

When I first read your writeup, I assumed that the one terminal was completely missing, not just loose.

After seeing Klaus' great closup photo of his inside terminals, it is obvious to me now that you can just tighten the nuts.

This is assuming you have the complete terminals.

Maybe a lockwasher, brass washer and extra brass nut would be a good idea as well.

You will still need to follow my suggested procedure of removing and re-installing everything.

Caution and care is the most important issue that I stress.

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Hi Frank

It is a very simple task of tightening two nuts after removing the woofer and the damping material, here is a magnified photo.

BRgds Klaus

Hi Klaus

Thanks for the magnified photo. I can see clearly the two nuts holding the terminals. One last question do you need to just unscrew and remove the centre woofer, and damping material only to get to the nuts holding the terminals?

One repairer I asked for a quote said it would probably need new caps and surrounds, and another said the terminals were part of the crossover board which may need replacing. Looks like I have saved quite a bit of money with your help.

Many Thanks

Regards

Frank

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One last question do you need to just unscrew and remove the centre woofer, and damping material only to get to the nuts holding the terminals?

Assuming that your speaker looks the same inside, yes.

One repairer I asked for a quote said it would probably need new caps and surrounds.

If the surrounds are damaged or defragmented by age (if they have not been replaced since new), it is probably time to do so. In that case, You only need to hand in the woofers not the whole speaker. Caps might need to be replaced, I have not replaced the caps in my LST-2 and they sound fine.

BRgds Klaus

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Assuming that your speaker looks the same inside, yes.

If the surrounds are damaged or defragmented by age (if they have not been replaced since new), it is probably time to do so. In that case, You only need to hand in the woofers not the whole speaker. Caps might need to be replaced, I have not replaced the caps in my LST-2 and they sound fine.

BRgds Klaus

Thanks....Do you use your LST-2 with a high powered amplifier? I had mine connected to a Luxman receiver rated at 75 watts per channel, but the sound seemed to lack depth without the loudness switch on, even at fairly high volume levels. Do you have the same experience?

Regards

Frank

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Thanks....Do you use your LST-2 with a high powered amplifier? I had mine connected to a Luxman receiver rated at 75 watts per channel, but the sound seemed to lack depth without the loudness switch on, even at fairly high volume levels. Do you have the same experience?

Regards

Frank

In general it is my experience that AR speakers benefit from being driven by a powerful amplifier, and the AR-LST-2 is no exception. With my somewhat limited knowledge of Luxman receivers, it is my impression that they are a bit anaemic in the power supply. The LST-2 is rated at 8 Ohm, and that also requires relatively more power. I would try to drive them with a well supplied amplifier with at least a 100 watt RMS in 8 Ohm. The 10" woofer in the LST-2 has a different and more subtle bass than the 12" in the LST-1, but the LST-2 is definitely not bass-shy.

BRgds Klaus

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Since you have to go in there anyway, I'd replace the caps. I thought my 3As sounded fine as well when I got them. I didn't plan on replacing the caps but I decided to do so and the new ones made a quite obvious difference in clarity. I suspect if you recap one of the speakers and a/b it to the other, before you recap it, you will be surprised at the difference.

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Luxman receiver rated at 75 watts per channel, but the sound seemed to lack depth without the loudness switch on, even at fairly high volume levels.

Regards

Frank

Hi again

Leave the loudness switch off, you are asking for trouble overdriving the amp and blowing the woofers.

You must also have the correct Allen wrench to remove the switch knob.

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Since you have to go in there anyway, I'd replace the caps. I thought my 3As sounded fine as well when I got them. I didn't plan on replacing the caps but I decided to do so and the new ones made a quite obvious difference in clarity. I suspect if you recap one of the speakers and a/b it to the other, before you recap it, you will be surprised at the difference.

I am a novice when it comes to inside working of a speaker enclosure. What are caps and can you give a brief explanation as how to replace them? Are they readily available from a speaker parts centre for the type of speaker I have?

Many Thanks

Frank

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Hi again

Leave the loudness switch off, you are asking for trouble overdriving the amp and blowing the woofers.

You must also have the correct Allen wrench to remove the switch knob.

Hi

I thought the loudness switch was there to boost the frequencies depending on the type of speakers you have. Some people seem to like the switch on, as it makes the system sound better. Telling then otherwise makes no difference. I would have though most high powered amp's, and speakers rated at a 100 watts plus would be able to handle it. Obviously at fairly moderate levels. Much less than half of the amp's capability. Perhaps not I don't know!!!!. Any other opinions out there?

Regards

Frank

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Hi

I thought the loudness switch was there to boost the frequencies depending on the type of speakers you have. Some people seem to like the switch on, as it makes the system sound better. Telling then otherwise makes no difference. I would have though most high powered amp's, and speakers rated at a 100 watts plus would be able to handle it. Obviously at fairly moderate levels. Much less than half of the amp's capability. Perhaps not I don't know!!!!. Any other opinions out there?

Regards

Frank

A loudness switch is there for when you listen at low levels. It compensates for our poor hearing at high and low frequencies there. At normal levels it sounds awful and will damage both amps and speakers. I actually thought most decent amps didn't have them.Beware! It's like too much Technicolour sorry Technicolor.

Mike.

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