Altec 3000G Tweeter Wiring Question

SongC

New Member
I got a pair of Altec 3000G tweeters that have red cable connects to terminal 2 and yellow cable connects to terminal 1 (see attached picture).

I am confused with which terminal is for the positive (+) lead and which terminal is for the negative (-) lead.

Any help would be greatly appreciated.

Thank you!
 
I'm not sure of the polarity but I can tell you that they have a fairly low power rating and can be damaged very easy. The diaphragm is actually out of Altec's microphone and is no longer available. The Altec 601 coaxials used this diaphragm in there design. Sadly a lot of the 601's on the market have a blown tweeter section.
What are you going to use them for? Maybe you would be better off selling them and getting a more robust tweeter?

BillWojo
 
I am going to use them to pair with Altec 755c in a open baffle setup, driven by 300B SET amp. Surely do not want to damage them.

Song
 
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It probably wouldn't hurt to put a fuse inline with the tweeter for protection purposes.
 
There is an Altec forum, I would ask both about the polarity and protection. It's called the "Altec Hostboard".
Be sure and post some pics when your done.

BillWojo
 
I know there is a "right" answer to this but I would hook them up both ways and decide which one I like the best. With the bigger horn speakers sometimes they sound better out of phase with the woofer. Obviously these are much smaller, so I do not know if the same holds true

Btw sounds like a cool project. Good luck with it!
 
Terminal 2 is the positive.The one on the left in this picture.If you look closely there is a red paint mark by the #2 terminal.
 
Thanks for all the responses!

I think I have learned a lot about Altec speaker polarity in a day. Terminal 2 for + lead it is then. :)

Btw, the 755C will be run at full range and 3000G will help out on with the upper frequency. I borrowed this sample diagram from Lowther site which is originally for its T90A tweeter.
Hopefully the 1 uf cap and the 8 ohm L-Pad will provide enough protection for the 3000G tweeter?
 
Thats a pretty high xover point. Something around 20khz. You will not have to worry about blowing the tweeter but you also might not get a lot of output. Maybe if you crossed it at 10khz with a first order xover it would still be safe and have good output.

Since you are running low power tubes instead of SS you can get away with a 6db slope and not have to worry about tweeter damage.
 
Hi elitopus, I thought that 1uf cap will cross at around 10khz. What value shall I use for crossing at 10khz? Thanks!
 
3000 series tweeters are nominally 8ohm.

However, the only impedance that's important will be the actual measured impedance at the intended crossover frequency, and that will be anything but a nice even number like 8 or 16. To begin to do this right you MUST know the impedance at frequency, or have the ability to measure it.

Also consider that a 6db/octave filter at 20khz is only bringing the signal down 6db at 10khz, 12db at 5khz. That's a lot of signal in the audible range still making it thru.

With a typical compression driver this is perfectly acceptable as their safe operating range usually takes them down to 1khz or lower.

The 3000 series tweeters are NOT typical compression drivers. They are far less robust, much more delicate. Personally, i would want a steeper filter on them, and that defies some of the goals of a system based on a quality extended range driver seeking just a bit of air on top.

Once again the audio iron law of "no free lunch" rears it's ugly head.
 
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Agree with Bowtie as usual ! Remember that a Altec 3000 tweeter has a microphone diaphragm..Extremely fragile if you blow the diaphragm you can throw them in the garbage.. The only place I knew of that could repair them with original diaphragms is no longer in service (Micro Mikes)...Bill Hayes had a stroke and his son sold all the equipment (Jig) and leftover diaphragms and the gentlemen who bought the stuff has no interest in doing repairs...
 
All wise advice...but I would go ahead and wing it with a 1.5- 2uF cap (8 ohms). You'll be OK with a 300B SE amp played at normal levels. Wisdom only gets you so far.

The extra overlap provided by the 2uF first order cap will enhance the leading edge definition of the 755C nicely.

If you use a 1uf or maybe 1.5uF cap on that 8 ohm tweeter, you might find that there is no need for an L pad because the tweeter will be rolling off already where the 755C runs out of action.

I did it before and I'm planning to do it again, when I pick up a pr of 3000s a friend is holding for me. This will be on 756Bs, one of which I got through the kind intervention of Bowtie Tom incidentally!

Every time I do this sort of hookup, I rediscover that the cap type influences the outcome more than the exact cap value. Try a few different approaches and use your ears to decide.

"In theory there is no difference between theory and practice. In practice there is." Yogi Berra

This is ears-on, experiment based system design.

Here's a pic of my 756Bs with 2uf WE caps on top, wired and ready to go, waiting for my tweets!!
If the sound blows my mind, I will permanently install the 3000s in the cabinets.

I am not worried about my tweeters at all with 300B and soon-to-be finished 275A single amps.

 
Agree with Bowtie as usual ! Remember that a Altec 3000 tweeter has a microphone diaphragm..Extremely fragile if you blow the diaphragm you can throw them in the garbage.. The only place I knew of that could repair them with original diaphragms is no longer in service (Micro Mikes)...Bill Hayes had a stroke and his son sold all the equipment (Jig) and leftover diaphragms and the gentlemen who bought the stuff has no interest in doing repairs...

I was very close to repairing a damaged 3000-series tweeter a number of years ago, but the parts got lost in a move. I have two dead examples on a pair of 601Cs, at some point I'll pull them off and try again.
 
It all depends on the crossover you use. 2nd order you wire the driver out of phase. First order in phase. Your first step with the drivers mounted in place apply low power pink noise to both drivers with out a crossover . If they are in phase as you move head between the drivers the sound will add smooth ly if the tweeter is out of phase you will hear different bands of frequencies disappear as you move your head.
 
I sent some 3000s to Bill Hayes for a rebuild, maybe around 1990. They didn't work properly when I got them back. At the time I was super busy, never followed up, and threw them in a box somewhere.

Eventually I took them apart and found that the replacement diaphragms were polyester. I was under the impression that the diaphragms should have been aluminum (duralumin) and the 1940s design mic that was supposedly the donor for the diaphragms specified aluminum.

I no longer remember which mic that was...maybe Bowtie knows. It was a familiar standard Altec microphone.

And the Badmaieff article in Audio magazine when the 601A came out also specified aluminum. I'm wondering if they may have switched parts in later production 3000s.

Sam, when you had parts, were the diaphragms polyester or aluminum?

Anyway, the diaphragms were glued in and mounted on a cylindrical frame that looked pretty much like a dynamic microphone element. Not field replaceable by goobers such as myself, unless the whole assembly was available.

I have since often wondered if that assembly was, in fact, a complete microphone element.
 
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