AR LST Crossover differences

[Mexicomike]

Here are some pics showing both sides of the Xovers out of my pair of LSTs. the lighter colored one is the older version. The newer one is out of LST serial number 59. THe paper is missing on the other so I don't have a reference as to when the change took place. The old one had 5000uF worth of caps for the transformer "filter," the newer one used 2500uF. I'm replacing them both with 2500uF.

There are no prizes for finding the differences in the circuitry!

[roundhome]

Here are some pics showing both sides of the Xovers out of my pair of LSTs. the lighter colored one is the older version. The newer one is out of LST serial number 59. THe paper is missing on the other so I don't have a reference as to when the change took place. The old one had 5000uF worth of caps for the transformer "filter," the newer one used 2500uF. I'm replacing them both with 2500uF.

There are no prizes for finding the differences in the circuitry!

I'm sure the 5000uf cap set up is in fact four 5000uf polar caps with the negs connected to make two 5000uf nonpolar then when put in parralel come out to 2500uf if this is in fact true then we can make new 2500 uf caps the same way and it would be vary cheap to do this is also the layout in one of the crossover schematics. please check this to be sure it would help with all the speakers that use this big cap

Thank you

JIm

[Mexicomike]

Each pair of 5000uF 50V caps that are "head to head" have all their connections soldered together, pos to pos and and neg to neg. Then there is a jumper wire between the positives of the two head-to-head pairs. The wires to the crossover circuit are connected to each side's negative terminal. You guys who know way more about this than me will have to figure out what it comes out to uF-wise!

[roundhome]

Each pair of 5000uF 50V caps that are "head to head" have all their connections soldered together, pos to pos and and neg to neg. Then there is a jumper wire between the positives of the two head-to-head pairs. The wires to the crossover circuit are connected to each side's negative terminal. You guys who know way more about this than me will have to figure out what it comes out to uF-wise!

Thank you that is all I needed to know they made bipolar caps so we can do the same thing AR did and get four 5000uf polar caps and make the ones we need or

like the way they did it here in this one pos to pos in out on the negs

[onplane]

Thank you that is all I needed to know they made bipolar caps so we can do the same thing AR did and get four 5000uf polar caps and make the ones we need or

like the way they did it here in this one pos to pos in out on the negs

You guys have the ultimate in speaker technology. Those LST's were an engineering marvel at their time.

Instead of fooling around with that huge cap bank and transformer, why don't you try passive bi-amping?

Bi-amping woiuld make the circuits much simpler and the work of the amps that much simpler. Further, with integrated amps you'd gain far more control over balance than you have with that 6 position switch.

Now, I well understand the desire to remain "classic", but why not push the ultimate speaker for the ultimate sound?

Regards,

Jerry

[roundhome]

You guys have the ultimate in speaker technology. Those LST's were an engineering marvel at their time.

Instead of fooling around with that huge cap bank and transformer, why don't you try passive bi-amping?

Bi-amping woiuld make the circuits much simpler and the work of the amps that much simpler. Further, with integrated amps you'd gain far more control over balance than you have with that 6 position switch.

Now, I well understand the desire to remain "classic", but why not push the ultimate speaker for the ultimate sound?

Regards,

Jerry

Maybe because I would need 30 amps and five 3way two channel electronic crossovers and just think about the wire

[KlausDK]

Thank you that is all I needed to know they made bipolar caps so we can do the same thing AR did and get four 5000uf polar caps and make the ones we need or

like the way they did it here in this one pos to pos in out on the negs

Hi Jim

According to John O'Hanlon, the bank of 4 polar capacitors made up for a 5000 uF bipolar cap, which turned out to be too big a capacitive load for some amps, hence the change to 2500 uF.

I am not sure that the use of polar caps "back-to-back" is as good as a polar cap.

The cross-over you posted is one I made of my modified AR-LST's cross-overs.

BRgds Klaus

[roundhome]

Hi Jim

According to John O'Hanlon, the bank of 4 polar capacitors made up for a 5000 uF bipolar cap, which turned out to be too big a capacitive load for some amps, hence the change to 2500 uF.

I am not sure that the use of polar caps "back-to-back" is as good as a polar cap.

The cross-over you posted is one I made of my modified AR-LST's cross-overs.

BRgds Klaus

I thought it was yours but could not remember that part is getting old fast. all of my LST's are of the 2500uf type but they still have the old 2500uf cap all the rest have been changed with solen caps

[onplane]

Maybe because I would need 30 amps and five 3way two channel electronic crossovers and just think about the wire

roundhome, under passive bi-amping you would need two amps as you would use the frequency selecting components already present in your LST's.

One amp would power the woofers and the 2nd amp the mids/tweeters. Only component I would add is a single 16 ohm resistor across all 4 mids. Idea here is to knock down the mids relative to the tweeters. Naturally, you could put in a pot similar to the AR-3 circuit, if you felt you needed complete control.

Anyhow, below is how I would do it ....

Regards,

Jerry

[roundhome]

roundhome, under passive bi-amping you would need two amps as you would use the frequency selecting components already present in your LST's.

One amp would power the woofers and the 2nd amp the mids/tweeters. Only component I would add is a single 16 ohm resistor across all 4 mids. Idea here is to knock down the mids relative to the tweeters. Naturally, you could put in a pot similar to the AR-3 circuit, if you felt you needed complete control.

Anyhow, below is how I would do it ....

Regards,

Jerry

I do know what I'm doing I have 8 LST and two LST II's for the center. and to gain much from separating the channels out you would need electronic crossovers I have DBX driverack PA units just for this. other wise you are still sending the complete signal to the amps only to be separated by the existing crossover in the LST. were with a electronic crossover at higher and lower points then the LST crossovers then the amps would handle just the parts for the bass mids and highs this is what makes the amps run cooler and have no drain on the highs from the bass beat. with your method you would not have much control over spectral balance. the way the LST is set up it balanced all three in respect to each other the only way to gain this same amount of control would be with three amps and a electronic crossover. any way its just a hobby.

[onplane]

... to gain much from separating the channels out you would need electronic crossovers ... with your method you would not have much control over spectral balance. the way the LST is set up it balanced all three in respect to each other the only way to gain this same amount of control would be with three amps and a electronic crossover. any way its just a hobby.

roundhome, I will respectfully disagree and my rationale is:

1. with my scheme you eliminate that cap bank and transformer - less is better - there is no way these components will "improve" the resulting sound plus they can create a drag on the amp

2. yes you have 6 different switch positions - only 6! In 3 of those the woofer is not attenuated. In 5 of the 6 the tweeter is ahead of the mids. Only in position 6 are the tweeters and mids at the same level. Bi-amping offers you an infinite number of positions.

3. you can attenuate the bass beat (fundamentals) via tone controls so they don't interfere as much with the highs. Please bear in mind, that with the woofer isolated from the mids/tweeters there is very little current draw in those frequencies even if voltage is present.

Totally, totally agree with your ascertain that "this is just a hobby"! Experimentation for me is the fun part of that hobby.

I bi-amp my 3a's with the stock three connections and just love the result. The woofer impedance changes significantly when disconnected from the rest of the circuit. In short, it's better behaved. Next, I really, really like the ability to change the tonal balance "on the fly". I find huge differences when I change sources and even FM stations.

Regards,

Jerry