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AR LST HElp!


Guest vintagestereogeek

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Guest vintagestereogeek

Hi, I have a pair of AR LST speakers. Yesterday I was listening at a pretty good volume and the right channel went dead. I turned off the amp for a few seconds, and the problem went away until I turned the volume up pretty good. Also, I have noticed that this speaker is not quite as loud as the other at low volumes. I believe there may be issues with the rt. speaker crossover. Mainly bad capacitors. I haven't opened the box yet to take a look. I wanted to ask you guys before I sent them to my technician. How many capacitors are there? Can these be bought new? Is there anything else in the speakers that deteriorates that yields these symptoms? John

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Check the fuses. The LSTs will play with blown fuses but at reduced level and reduced hi-fregs. I learned this lesson with mine about two months ago - thought I had ruined them but they were fine, just blew the fuses. Put a jumper wire across the fuse terminals and see if the sound changes.

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Hi, I have a pair of AR LST speakers. Yesterday I was listening at a pretty good volume and the right channel went dead. I turned off the amp for a few seconds, and the problem went away until I turned the volume up pretty good. Also, I have noticed that this speaker is not quite as loud as the other at low volumes. I believe there may be issues with the rt. speaker crossover. Mainly bad capacitors. I haven't opened the box yet to take a look. I wanted to ask you guys before I sent them to my technician. How many capacitors are there? Can these be bought new? Is there anything else in the speakers that deteriorates that yields these symptoms?

I don't think loss of sound due to bad capacitors, blown fuses or any other component inside the speakers would go away or improve in any way because the amp was turned off for a few minutes. It sounds to me more as if the protection circuit of your amplifier is shutting down and then resetting when the amp is turned off.

What is the amplifier that is being used with these speakers, how much power does it have, is it rated for 4 ohm speakers, and how high up is "up pretty good?

Before opening the boxes, the first thing to do is

(1) Make sure the amp has at least 25 watts per channel RMS (50 would be better) according to the OLD power rating system in use during the 1970's (RMS watts, measured across operating frequency range with BOTH CHANNELS powered). If you're using a newer "home theater" amplifier, this is equivalent to 50-100 watts per channel. The amplifier MUST be rated for use with 4 ohm speakers. These specs will be sufficient for AVERAGE sound levels (you should be able to carry on a converstion with someone at normal speaking voice while the music is playing). To turn the volume up to elevated levels, you'll need double or triple the power (75-100 watts per channel by 1970's specs, 150-200 watts by today's "home theater" specs).

(2) If the amp meets the above specs, run the speakers for an extended period of time at low to moderate levels (about the same level as speech) and see if you notice any of the same problems.

(3) Try swapping the left and right channels and see if the problem moves to the other channel.

(4) Try the amp with different speakers and the speakers with a different amp that meets the specs in (1) and see if you detect any of the same problems.

Classic ARs can handle massive amounts of clean, undistorted power, but their tweeters will fry if subjected to even moderate levels of clipping. If that right channel speaker sounded ok before you turned the volume up and "not quite as loud" means there are now reduced or no mids or highs from any of the drivers, it may mean those drivers have been damaged or destroyed.

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Guest vintagestereogeek
I don't think loss of sound due to bad capacitors, blown fuses or any other component inside the speakers would go away or improve in any way because the amp was turned off for a few minutes. It sounds to me more as if the protection circuit of your amplifier is shutting down and then resetting when the amp is turned off.

What is the amplifier that is being used with these speakers, how much power does it have, is it rated for 4 ohm speakers, and how high up is "up pretty good?

Before opening the boxes, the first thing to do is

(1) Make sure the amp has at least 25 watts per channel RMS (50 would be better) according to the OLD power rating system in use during the 1970's (RMS watts, measured across operating frequency range with BOTH CHANNELS powered). If you're using a newer "home theater" amplifier, this is equivalent to 50-100 watts per channel. The amplifier MUST be rated for use with 4 ohm speakers. These specs will be sufficient for AVERAGE sound levels (you should be able to carry on a converstion with someone at normal speaking voice while the music is playing). To turn the volume up to elevated levels, you'll need double or triple the power (75-100 watts per channel by 1970's specs, 150-200 watts by today's "home theater" specs).

(2) If the amp meets the above specs, run the speakers for an extended period of time at low to moderate levels (about the same level as speech) and see if you notice any of the same problems.

(3) Try swapping the left and right channels and see if the problem moves to the other channel.

(4) Try the amp with different speakers and the speakers with a different amp that meets the specs in (1) and see if you detect any of the same problems.

Classic ARs can handle massive amounts of clean, undistorted power, but their tweeters will fry if subjected to even moderate levels of clipping. If that right channel speaker sounded ok before you turned the volume up and "not quite as loud" means there are now reduced or no mids or highs from any of the drivers, it may mean those drivers have been damaged or destroyed.

The protection circuit in the amplifier is definately kicking in. I am using an Acurus a200 which supplies 300 plus watts into 4ohm. Both speakers sound great until about 11 o'clock on the preamp (adcom gtp 400) then the right speaker quits. For some reason, the protection clicks on the amplifier.

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Guest vintagestereogeek
The protection circuit in the amplifier is definately kicking in. I am using an Acurus a200 which supplies 300 plus watts into 4ohm. Both speakers sound great until about 11 o'clock on the preamp (adcom gtp 400) then the right speaker quits. For some reason, the protection clicks on the amplifier.

I just wanted to add that I switched the speakers to Dahlquist DQ 20's and I can go to 3' oclock on my preamp and they are absolutely blaring... no protection circuit problem. When I had my Conrad Johnson Premier 12 mono's hooked up for the last year, the rt. speaker was just a tad softer also. I know that tube amps aren't affected as much by speaker problems. John

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The protection circuit in the amplifier is definately kicking in. I am using an Acurus a200 which supplies 300 plus watts into 4ohm. Both speakers sound great until about 11 o'clock on the preamp (adcom gtp 400) then the right speaker quits. For some reason, the protection clicks on the amplifier.

What happens if you swap the speakers left to right?

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Guest vintagestereogeek
What happens if you swap the speakers left to right?

I was going to switch the actual speaker wires in the back of my amp while the problem occurred. Didn't get that far. I also reasoned that since I have used the Conrad Johnsons (rt channel was always weak) Marantz 1200b protection rt channel, and the acurus, again protection rt channel; that there would seem to be a problem with the speaker. I talked to my tech, and he said that there is either a "smoked tweet or mid" that is lowering the impedance to make the amp. protection kick in, or there is a problem with the crossover. I am going to drop off both speakers to his house for diagnostics. He has the same Adcom tuner/pre, and the same Acurus A200. John

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I talked to my tech, and he said that there is either a "smoked tweet or mid" that is lowering the impedance to make the amp. protection kick in, or there is a problem with the crossover.

If a driver is shorting, it's possible. I think on a system like the LST it would probably take more than one shorted driver. A short in the crossover is also possible, but less likely than within the driver.

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Guest vintagestereogeek
If a driver is shorting, it's possible. I think on a system like the LST it would probably take more than one shorted driver. A short in the crossover is also possible, but less likely than within the driver.

HI guys. Thanks for all the help. I dropped the speakers off at my tech's house. They ran perfectly and all caps, inductance cap, tested great. I am pretty sure that I had a bad connection via speaker wire. It was badly frayed and I think it could have contacted the foil strip on back of post as well. I will try banana plugs to remedy this. Thanks again. John :lol:

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