Forty Tweeters Later.............

[frankmarsi]

6-3-12

With 20 HiVi and 20 AB-Tech tweeters and 40 coils on hand, would some one please come forth and tell me about the ‘new’ crossover mod for the 'LST'?

This stuff was bought when the ole inductor was in CSP fashion.

If one searches the site from a few years ago, I first asked if a resistor and cap would work? I read in different places that inductors were the way to go. No, I never did install any tweeters, except for one and it blew. I continue to rely on the Micro-Statics as I have. They're not bad, and they handle huge amounts of power with out a flinch, but having all originals was better as I experienced some time ago before the originals were all blown after a number of 'life-like' listening sessions.

Now I’m reading that HiVi tweeters are not the way to go on the LST either. I am not a low-volume listener so, if anyone knows of a low cost high power handling unit that has been tried with good results, please come forth.

Yes, I know it's been sometime since then, but now, I’m befuddled even more so! It's almost a good thing that I didn't install any tweeters, they would be blown by now too.

Again, I find the Micro-Static's sound good, but I still don't have the 'completeness' and full-width dispersion of four tweeters across each cabinet.

FM

P.S. I apologize for bringing up this old topic, but when I read of newer methods and comments regarding these replacement tweeters I was curious. Can some one tell me the values and source of the resistor and cap combo?

[RoyC]

Hi Frank,

If you are replacing all of the tweeters in a cabinet, either brand of tweeter could still be used. Problems arise when mixing original tweeters with new tweeters in the same cabinet.

The HiVi and the ABT tweeters will handle more power than the original tweeter if properly installed. The previously discussed installation of a parallel coil, or a smaller tweeter crossover cap (around 2uf) is required.

Roy

[ligs]

Hi Frank,

This is just a thought. How about spreading 2, 3 or 4 high quality HT satellite speakers on top of the LST to provide the dispersion pattern you desire. I am using Infinity TSS 750 as an example because it is available from eBay and is of high quality http://www.hometheater.com/content/infinity-tss-750-speaker-system-ht-labs-measures

In addition, TSS 750 has a 3/4-inch hard dome and is very flat from 2 k Hz and up. You probably can blend them with LST very easily with a simple capacitor in the path.

I have a set up where I use a single TSS 750 as a fullrange sitting on top of AR 3(woofer only) and this combination has some promise and it can be played very loudly without stress.

BTW, your advice of not putting plastic peanuts when packing raw drivers is excellent and I still follow it.

[frankmarsi]

6-5-12

Hi Roy, and thanks for throwing in a life preserver, I’m drowning here!

So, as dense as I may seem; it’s not completely clear to me. I have all of the recommended coils values (5mh & 7mh) for both individual tweeter brands; can I go ahead and install them as mentioned? I was under the impression that the four coils would cause problems with the LST’s X-over. In terms of power handling, which is more capable, the HiVi, or the AB-Tech? I must say again, I often listen at ridiculously high levels and I’d feel really bad if I start blowing tweeters again. In my defense, forgive my crazy habit of listening at realistic levels but anyone who has experience with these AR models would surely agree that it’s hard not to want to crank them up. LST’s don’t actually seem to get louder, it’s more like they simply sound ‘bigger’ and can thrill to great untold pleasure giving heights. Apparently I lack a degree of personal self-control, I must admit. Funny thing is, I’m not sorry as I truly do enjoy myself, over-blown self-indulgence should have been my middle name.

While we’re at it; in terms of using the AB-Techs, which value inductor would give me a ‘touch’ more of extended high frequencies, the 5mh, the 7mh coil or another, which is best respectively for the HiVi or AB-Tech, or ain’t that gonna happen? Or, which cap/resistor combo is recommended if at all? I read somewhere that the AB-Tech’s ‘fall-off’ or don’t reach that high, do the HiVi’s?

To respond to “ligs”, using the micro-statics is somewhat visually acceptable as they mimic the LSTs in styling, I wouldn’t want to add a square box on top speaking purely of esthetics. Also, I’m just hungering to allow my speakers to play and look as they were intended to originally, albeit if possible with a touch of more high-frequency response as most would agree AR’s can benefit from.

FM

[RoyC]

Frank,

The coil values were determined to put the replacement tweeters in the ballpark for the AR-3a. I do not know of anyone who has replaced all of the tweeters in a pair of LST's, so you have to be willing to experiment. As you know, past discussions regarding the LST have been conjecture.

Both the HiVi and the ABT tweeters have plenty of high range output, but the ABT tweeter is more sensitive (4 ohms) and has a 3/4" dome like the original. Since you have them, you should probably start with those.

As for the crossover mod, the difference between the coil values is not of much consequence relative to your concerns. To begin with, try one .07mh coil across the tweeter arrangement in the same way the 1.35mh coil is placed across the midrange drivers (refer to the schematic). A possible simpler alternative would be to replace the original 6uf cap with a 2uf cap (or put a 3uf cap in series with it), and not use any coils. When replacing all tweeters in the cabinet, you only need one coil (or one capacitor) per cabinet.

If I recall, you were reluctant to tackle the crossover work last time we discussed this. There is no way around it. My offer to assist you still stands.

Roy

[frankmarsi]

6-5-12

Hi Roy, sounds like an offer I may not be able to refuse.

Let me get my act together and I’ll make contact with you as soon as I am able to. Any further suggestions you may have are certainly welcomed.

If you feel the way to go may be easier in using only one coil or cap and only opening the back panel of the cabinet and exchanging only one component, I'm all for it.

I'm surprised other owners of LSTs haven't tried this yet, I haven't seen it reported here.

And thanks for the offer.

FM

P.S. Pete B. thanks to you also, as time permits I will be in touch.

[Pete B]

I've said before that when a system is really clean, with a lot of power,

it doesn't seem to sound loud, I agree perhaps bigger and I think this is

because most of us associate "loud" with distortion.

The coil will significantly improve the power handling by more quickly

attenuating out of band material - I'd say use them. If either of the

replacement tweeters are more efficient and require padding, you can

put a small cap (1 to 2uF) across the pad to push up the top end

extension.

I'd be happy to help you also Frank as I really enjoy big powerful

systems.

[RoyC]

If you feel the way to go may be easier in using only one coil or cap and only opening the back panel of the cabinet and exchanging only one component, I'm all for it. I'm surprised any owners of LSTs hasn't tried this yet, I haven't seen it reported here.

And thanks for the offer.

FM

P.S. Pete B. thanks to you also, as time permits I will be in touch.

Most LST owners are typically trying to replace one or two tweeters in a cabinet, which is actually more difficult due to the nature of the LST crossover.

Frank, it would be nice to get at least one pair of your beasts "whole" again as a starting point, if nothing else.

Pete, I would personally find your input regarding the LST replacement tweeter situation most welcome!

Roy

[frankmarsi]

6-5-12

Roy C. and Pete B. might it be to much trouble to see a wiring diagram of the proposed additions and or changes?

If it's a hassle let it go, then we could discuss it all when we finally get together.

fm

[RoyC]

6-5-12

Roy C. and Pete B. might it be to much trouble to see a wiring diagram of the proposed additions and or changes?

If it's a hassle let it go, then we could discuss it all when we finally get together.

fm

Frank,

Below is the schematic in the CSP Library. See if it makes sense to you regarding the discussion above. You will need to get into the cabinet to proceed.

Roy

[frankmarsi]

6-5-12

Hi Roy, well to be open about it, I can read a schematic but, that doesn’t mean I know what to do or how to interpret it. A simple man such as I depends perhaps on a simple line drawing, or even better a LST X-over photo that shows exactly where the new components are to be soldered in and what is to be disconnected or simply cut out of the circuit might be better for me. I really couldn't say until I drop the back panel and see, but even then I just know I'll run into problems. My apologies for sounding simple-minded here, but if I were given a diagram with instructions I might be able to pull this off, and if its any trouble to you, then I will find a way. Instructions like; locate this coil or this cap etc. at this terminal lug and cut at this point and re-attach the new cap between these points and so on I could pull off….. I’m rather silly, I know.

I know the symbols of the components, but tracing their contact points relative to one another in an actual circuit stumps me in terms of the components polarity and so on.

fm

[RoyC]

6-5-12

Hi Roy, well to be open about it, I can read a schematic but, that doesn’t mean I know what to do or how to interpret it. A simple man such as I depends perhaps on a simple line drawing, or even better a LST X-over photo that shows exactly where the new components are to be soldered in and what is to be disconnected or simply cut out of the circuit might be better for me.

fm

Frank,

Take some photos of your crossovers and email them to me, as I do not have LST's or adequate crossover photos to use as a reference. It would be easier if we are both looking at the same thing. This is uncharted territory. :-).

Roy

[frankmarsi]

6-5-12 10PM

Roy, sounds like a plan, however I'm out of here till Saturday at which time I will attempt at opening a back door to a LST.

You say it "is uncharted territory" do you? It sure will be as I'll have to move a number of things to get to them, but I will do so.

Here's something I pulled of this site just to get an idea, this particular cabinet has obviously been upgraded with new caps, whereas mine are all original so maybe this photo isn't worth looking at?

This doesn’t exactly look like a basket of joy in any event, does it?

FM

 

[RoyC]

6-5-12 10PM

Roy, sounds like a plan, however I'm out of here till Saturday at which time I will attempt at opening a back door to a LST.

You say it "is uncharted territory" do you? It sure will be as I'll have to move a number of things to get to them, but I will do so.

Here's something I pulled of this site just to get an idea, this particular cabinet has obviously been upgraded with new caps, whereas mine are all original so maybe this photo isn't worth looking at?

This doesn’t exactly look like a basket of joy in any event, does it?

FM

Those are original Sprague capacitors (on an LST-2 crossover board), Frank, not replacements. LST's have point to point wired boards similar to the LST-2 board in your photo as well as printed circuit boards. There are variations in crossover boards and wire colors.

Attached is a photo of an LST with a printed circuit board. The green "X" indicates a tweeter cap which was out of spec.

Another issue you may have to deal with is converting the back-wired replacement tweeters to front-wiring.

Roy