LST Tweeter Output

[mike tarelli]

Apologies if this topic has been covered before but I can't find it in the forum.

Is the output of the front tweeters on LSTs meant to be quieter than the side ones?

I believe this is true on the 4 tweeter MST but I can't remember ever seeing that this was normal for LSTs.

Thanks,

Mike

[xmas111]

All four tweeters should have the same output.

[RoyC]

They are supposed to be the same. Due to the nature of their construction and age related degradation, however, the 8 old tweeters in a pair of LST's often vary significantly in output these days. In fact it is not unusual to find just 2 of these tweeters to vary in a pair of 3a's.

Roy

[tysontom]

The tweeters are also wired in a series/parallel fashion, so there are some slight variations between even properly working tweeters.  If one tweeter is defective, it will affect the output of the others as well. 

[RoyC]

25 minutes ago, tysontom said:

If one tweeter is defective, it will affect the output of the others as well. 

That's a good point, Tom. I would add that using any replacement tweeter(s) of a different type in combination with original tweeters will significantly throw things off due to this arrangement.

I don't recall hearing much of a difference, however, when all of the original tweeters were working properly with similar uninstalled output....or if all identical replacement tweeters were used. The tweeter arrangement consists of two parallel pairs of series-wired tweeters, filtered by a single (6uf) crossover cap.

Roy

[mike tarelli]

Thank you gentlemen for the replies.

Looks like it's time for action with the tweeters.

If I made a once in a lifetime decision to repair or renew the 8 front-wired tweeters, what would you recommend?

Chris's rebuilds?

 Hi Vi's with inductors?

I am in the UK.

Thanks again. 

[JKent]

Roy rebuilt some AR-3a tweets for a project I was working on and they’re great!

Of course you'll have to check with him to see if he's willing to take on eight of those. I know there's a lot of work involved. And then there's the trans-Atlantic shipping cost.

You can get the Hi-Vi/Swan tweeters on your side of the pond, so that may be more economical. OTOH, the LSTs are special speakers that are worthy of the investment in rebuilding.

So many decisions. . . .

[ra.ra]

There was some in-depth discussion about these tweeter options here in Kent's recent 3a restoration. 

http://www.classicspeakerpages.net/IP.Board/index.php?/topic/10638-another-ar-3a-restoration/

And for a pic of the wiring mentioned above, schematic is attached.

 

[genek]

Eight tweeter rebuilds is a big chuck of change. HiVi might be something to consider, at least as a stopgap while saving up the pennies for proper rebuilds of the originals. And to keep the speakers usable while the rebuilds are being done. The upside of doing it in LSTs is that dispersion of any individual tweeter should be less of a concern than in a box.

[mike tarelli]

Thank you Kent, ra.ra and genek for your helpful suggestions.

I appreciate your expertise and generous spirit in helping me to decide.

As LSTs are so special, I think I must pursue the rebuild route- not so much biting the bullet but biting the 16 inch shell !

Thanks again. 

[mike tarelli]

Update time.

Thanks again to everyone who replied to my original post.

In the end I decided to contact Chris and go with the rebuilds.

I carefully noted the wiring, only to find out later that it was hopelessly wrong!

All 8 tweeters had been replaced in 1974 and had identical date stamps.

Chris did the work very quickly and the result is excellent.

Don't want to get lost in flowery descriptions of sound, but the speakers sound more spacious.

He has done a fantastic job and provided me with the correct wiring diagram.

Special mention also to Roy, who guided me behind the scenes.

This leads to "A CAUTIONARY TALE".

When I sent the tweeters with UPS they arrived next day, before midday, and cost £50 / $62. UPS also advised the Waybill was marked "temporary export for repair". All was well.

When Chris came to return the tweeters with UPS, in the same packaging, to arrive in 2 days, it cost £264 / $4331. The Waybill was marked, by mutual agreement, "returning repaired items".

OK, it was more expensive, but the real problem happened in the UK. Customs obliged UPS to hold on to the package whilst I provided more information. In the end, they decided the cost of repair  plus the shipping cost  was what the tweeters were worth. To release the package I had to pay a further £192 / $240. Basically, they kidnapped my tweeters and held them for ransom for 5 days!

Everybody involved in this project is a star apart from UK customs!

If you have ever thought about having your tweeters rebuilt, do it! Just try and avoid UK Customs!!