La Scala Tweeter Mod

[mwiener]

Anyone out there have a replacement tweeter horn for the LaScala? I would like to put one in that increases higher frequency output. Currently I am running a very small piezo to do this, obviously not a good thing.

I want to run the amp flat (no path signal modification). But to get the percussion high end I am used to, I have to run the piezo. I used to play the drums, and I have been told I probably rounded off the upper frequencies of my hearing. So I may be compensating for poor hearing in the 12-20k range. Without the piezo, the high end just doesnt sound right to me without a little treble boost (signal path modification).

Interesting that this does not seem to be an issue with either my Cornwalls or my Heresy IIs in my home theater. But I am not doing critical listening when I watching T2. ;-)

Amp is Adcom 545, LaScalas are late 70s the serial number being 20Txxx for dating purposes. I am the one and only owner, and they are completely virgin. Exactly the way they came out of the box, except for some spikes I added. I have tried the Heresy IIs on the Adcom amp, and it sounded fine to me. So I really think the mod needs to be done on the LaScala.

BTW, anyone do the the external C Clamp bracing modification to keep the cabinet from resonating as was discussed in an earlier post?

[Ray Garrison]

One thing you might want to try is replacing your stock (AA?) crossovers with Al's crossovers (see topic under Updating Older Speakers). Al's have multiple taps on the SQUAWKER transformer, which allows you to vary the midrange level relative to the high / low end. You could pad down the midrange, say, 6 to 12 dB, which would have the same effect as lifting the top / bottom by the same amount. This might give you the high frequency boost you're looking for without swapping out the tweeter. As to the bass lift, that may be a good thing or not a good thing, depending upon your reaction... as you used to be a drummer, you might really like it a lot...

Ray

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Music is art

Audio is engineering

[drobo1]

Ray's right. Get the Al K crossover upgrades or build some yourself. They do wonders for the high end, imaging, and overall tonal balance and clarity. It may not be important to you since you are running a solid state amp that is known to handle impedance swings nicely, but the upgraded crossovers present a very stable and flat impedance load to your amp/amps.

drobo

[mwiener]

I will entertain the idea of the new cross over. I have read the rave reviews. Now I just have to convince my wife to let me spend some more money.

This month I am buying AVR-4800, POA-5200, and A Velodyne CT-150. My commission check just came in. ;-)

I think I need to wait a little while before I approach the wife on spending more.

I would still like to hear any other ideas on replacement tweeters.

Mike.

[oosting]

You know, 20Txxx's were made in 1979. Have you ever replaced the tweeter diaphrams? Do yourself a favor and buy new diaphrams from EV for around $50 including S/H before you rip into the x-over. My LaScala's were made in '78 and needed the diaphhams replaced because I wasn't hearing much high end. They are easy to replace.

Electro-Voice part #89486 A -- diaphrams for T-35A tweeter. Cost $21.70 each + 8.00 S/H. Phone: (800)234-6831.

Ed

[Dick]

Mike.

For my money, and I did spend it on Al's xovers, you couldn't go wrong with a change in the xovers. I don't know if they will compensate enough for your possible hearing loss, but I had a real hard time believing that my La Scala tweeters were actually working until I installed Al's xovers with the 5-2 tap setting -- all the difference in the world. I imagine that the wife will hear/love the difference also.

[drobo1]

oosting,

Can you describe the procedure to replace the tweeter diaphragms?

drobo1

[Ray Garrison]

1) Buy new diaphram

2) Remove old diaphram

3) Insert new diaphram

I'm sorry, it's late, I was sitting here and somehow the post just happened...

[Al Klappenberger]

Ray,

That procedure just too complicated! Try this one:

1) - Do it!

Easy huh?

Al K

[dtximages]

WAIT a minute on replacing the diaphragms. I have taken my older K77 diaphragms out and resoldered them before with no problem until I smashed a voice coil and I got two new EV T35s. The same ones described above. I installed them and both tweets had the same problem. Very very low output. It was not subtle at all. I resoldered and tried to resolve the problem but couldnt seem fix it. So I bought whole new tweets for $250 off ebay and they are great. I dont know if it was something that I had done wrong or what but my T35s didnt work right. Klipsch also uses a cardboard ring around their dia. that is about 2mm thick that EV does not use. That could make a huge difference in where the voice coil sets in the magnet but even when I tried using it with the EV it still wouldnt put out much sound. Has anyone been successful with the T35? These were a light brown color while my origionals are a darker brownish red color. Did I get the right diaphragms???

BTW I do have both diaphrams and both horns with magnets if you want to buy them. You can try the EVs but I would have them professionally installed. I thought I could do it but it guess not.

cls72@hotmail.com

205-601-4890 (cell. ph)

Thanks Chris

[oosting]

cls72,

I replaced the diaphragms on my k-77 tweeters (the AlNiCo versions with round magnets) using diaphragms from EV with no problem. The diaphragms I used are just like you described.

There are only a few possibilities for the low output that I can think of:

1) something stuck in the voice coil air gap, binding the voice coils

2) voice coils both out-of-round or not the right size

3) magnets have lost most of their magnetism

Don't think it is 1 or 2. Check the magnets by placing a large screwdriver close to the voice coil gap. The magnet should grab the screwdriver. You should be able to lift the magnet portion of the tweeters with the screwdriver if you lay it across the front of the magnet portion. That's all I can think of.

Ed

[dtximages]

Yeah thats what I thought too. They were playing clearly without scratching but there was just no volume. When I took them apart the magnet structure fell apart but i didnt think at first that it would make a difference. Hmmmm, how would I make them work again?

[mwiener]

All,

Thanks for the info. Sorry I did not reply before now, I have been out of town. I think the way to go to start will be replacing the diaphrams. Next I will try the new crossover. I think I may put this on the back burner for a couple of months. I just put together my other HT system, and I need to dedicate a little attention there to tweak it.

Besides, I have to let my bank account accumulate a little more.

Mike.

[djk]

quote:

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Originally posted by cls72:

Yeah thats what I thought too. They were playing clearly without scratching but there was just no volume. When I took them apart the magnet structure fell apart but i didnt think at first that it would make a difference. Hmmmm, how would I make them work again?

---

Replacing the diaphragms is not as simple as "do it".I have done over 100.Three points.Mark the location of the crossover lead,the wire going from the bottom of the coil to the top,it determines polarity.Make sure this lead fits into the slot milled into the top plate,otherwise it will rub.If the top plate of the magnet moves during dis-assembley throw it away.On alnico magnets they go dead if this plate moves(cls72).On ceramic magnets if you can get it back to within 25uM(0.000984")it will be fine.This is almost impossible to do because the magnet makes it wants to pinch over.Depending upon the adhesive EV used and the age of the tweeter success rates were from 80~90%(in other words I had to throw it away as often as one out of five repairs).A speaker repair shop mith a magnet charger can repair them.