AR-LSTll

[Guest]

What year did AR change the LSTll from a six position spectral balance to a 3 position switch.

[Guest]

I don't think they changed. Are you sure you're not thinking of the ARLST? I have a pair of ARLSTII's serial numbers 7758 and 7759 that have the three position switches. I also have a technical sheet on the ARLSTII that specifies

three position switches for the LSTII. I also have an instruction book for the LST which explains the six position switch and autotransformer. The schematic in the owners manual also shows the autotranformer.

Do you know if AR used four ohm or eight ohm midrange and tweeters in the ARLSTII? I know the

ARLST had the same ones as the AR3a, but have not been able to determine this for my ARLSTII's.

Richard Boneske

[Guest]

I also have pair AR-LST and a Pair of AR-LSTll.The broucher I have on the AR-LSTll shows the spectral balance plate with 6 positions.

Over on the back then states control:Six postion spectral energy responce.The AR-LSTll I have are using 8 ohm tweeters which will read about 5.00 ohms to 6.2 ohms and also the same readings for the mids.

The AR-LST I have tweeters read between 2.5 ohms to 3.5 ohms and also same for the mids.The drivers in the AR-LSTll are brighter sounding in comparison to the AR-LST due to the resistance differnce of the drivers so therefore there is a differnce in the two and could not be interchanged which also cause a sound quality change.

[Steve F]

My compliments on the sharp attention to detail! Hats off.

The LST-2 was introduced in March 1974.

The preliminary literature for the LST-2 did indeed show a 6-position spectral switch, but the actual production units always had 3-position switches. Often, small details will change between the time a manufacturer shows their intoductory brochure and actually produces the unit. This can be due to parts availability, unexpected cost increases that crop up somewhere else, unanticipated manufacturing complications, or last-minute marketing changes-of-heart.

Another example of a slight inaccuracy of preliminary info vs. actual production unit is the AR-5: early brochures show the 5 with side-by-side midrange and tweeter drivers (a la the 2ax), whereas the real production pieces had staggered drivers like the 3a.

I owned LST-2's for 10 years before I gave them to my cousin, and he used them for another 8 years. Great speakers.

Steve F.

[Guest]

This is why I like this forum.When you need good logical answers you can find them here.Thanks

[Steve F]

>The drivers in the AR-LSTll are brighter sounding in >comparison to the AR-LST due >to the resistance differnce of >the drivers so therefore there is a differnce in the >two and >could not be interchanged which also cause a sound quality change.

The midranges and tweeters in the LST-2 and 5 are essentially identical to the drivers in the LST and 3a, except for the impedance. Their fundamental response characteristics are absolutely the same, and neither the 8-ohm nor the 4-ohm version could be said to be "brighter" or "duller" sounding in comparison to the other. (A quick glance of AR’s own published technical driver data from that time period confirms the identical responses of the tweeters and midranges, whether used in the LST or LST-2, or in the 3a or 5.)

Yet TROUBLESHOOTER brings up an interesting point: the notion that the LST-2 sounds a little brighter or more forward than the LST. This may very well be true; however, it’s not because of any inherent response difference in the 8-ohm vs. 4-ohm tweeter.

There are two issues at play here. One is the difference in radiation pattern between the LST and LST-2: With its front panel forward-facing midrange driver, the LST-2 puts a little more "presence" into the direct listening field than the LST. The LST’s midranges are all on the side panels, and thus they deliver their energy more into the reverberant field. The listener may easily perceive slightly more midrange energy from the LST-2, which would commonly be thought of as "brightness."

The other issue has more to do with psychoacoustics and the way people interpret the sound they hear, than it does with actual objective spectral radiation pattern measurements. The LST’s bass response (like the 3a’s) extends considerably deeper in the bass than does the LST-2 (or 5). Very often, people feel that the existence of substantial deep bass can somehow "mask" or "obscure" the sound higher up in the spectrum. Two speakers with identical responses above, say, 60Hz, might sound quite different if one goes down flat to 30Hz, and the other rolls off at 55Hz. It won’t just be a difference in the amount of "bass." It can also be perceived as a difference in clarity and "airiness." This is yet another reason why speakers are so endlessly fascinating. It’s difficult to predict their sound strictly by the numbers.

These subjects have been dealt with in a couple of past threads that you may find interesting:

Topic #1222: AR-3a and AR-5 Spectral balance

and

Topic #857: Survey for AR-LST and LST-2 owners

Just as an aside: It’s correct to observe that LST-2 tweeters and midranges are not interchangeable with LST midranges and tweeters. Because of their higher resistance, using LST-2 drivers in an LST would actually result in a duller, not brighter, sounding speaker, because the higher resistance drivers would reduce the effective voltage drive level to the midrange and tweeter sections, attenuating their output.

Steve F

[roundhome]

>The drivers in the AR-LSTll are brighter sounding in >comparison to the AR-LST due >to the resistance differnce of >the drivers so therefore there is a differnce in the >two and >could not be interchanged which also cause a sound quality change.

The midranges and tweeters in the LST-2 and 5 are essentially identical to the drivers in the LST and 3a, except for the impedance. Their fundamental response characteristics are absolutely the same, and neither the 8-ohm nor the 4-ohm version could be said to be "brighter" or "duller" sounding in comparison to the other. (A quick glance of AR’s own published technical driver data from that time period confirms the identical responses of the tweeters and midranges, whether used in the LST or LST-2, or in the 3a or 5.)

Yet TROUBLESHOOTER brings up an interesting point: the notion that the LST-2 sounds a little brighter or more forward than the LST. This may very well be true; however, it’s not because of any inherent response difference in the 8-ohm vs. 4-ohm tweeter.

There are two issues at play here. One is the difference in radiation pattern between the LST and LST-2: With its front panel forward-facing midrange driver, the LST-2 puts a little more "presence" into the direct listening field than the LST. The LST’s midranges are all on the side panels, and thus they deliver their energy more into the reverberant field. The listener may easily perceive slightly more midrange energy from the LST-2, which would commonly be thought of as "brightness."

The other issue has more to do with psychoacoustics and the way people interpret the sound they hear, than it does with actual objective spectral radiation pattern measurements. The LST’s bass response (like the 3a’s) extends considerably deeper in the bass than does the LST-2 (or 5). Very often, people feel that the existence of substantial deep bass can somehow "mask" or "obscure" the sound higher up in the spectrum. Two speakers with identical responses above, say, 60Hz, might sound quite different if one goes down flat to 30Hz, and the other rolls off at 55Hz. It won’t just be a difference in the amount of "bass." It can also be perceived as a difference in clarity and "airiness." This is yet another reason why speakers are so endlessly fascinating. It’s difficult to predict their sound strictly by the numbers.

These subjects have been dealt with in a couple of past threads that you may find interesting:

Topic #1222: AR-3a and AR-5 Spectral balance

and

Topic #857: Survey for AR-LST and LST-2 owners

Just as an aside: It’s correct to observe that LST-2 tweeters and midranges are not interchangeable with LST midranges and tweeters. Because of their higher resistance, using LST-2 drivers in an LST would actually result in a duller, not brighter, sounding speaker, because the higher resistance drivers would reduce the effective voltage drive level to the midrange and tweeter sections, attenuating their output.

Steve F

Steve maybe you can help me I have a pair of lst all drivers are good but no crossover I have picked up a LST II crossover set . now could I sub two lst mids for one lst II mid and some crossover changes to match the same as the lst could I make it work in my cabinets granted only three step adjustmesnts but that would be ok untill I can get the LST crossovers?

that would be two 8 ohm and two 4 ohm tweeters and mids I have the big caps to put in also jsut some coil changes

Thank you

Jim