Altec 755C + Super Tweeters - Altec 3000H, Realistic 40-1375 and Peerless MT225

L > R: Peerless MT225, Altec 3000H and Realistic 40-1375

Although I prefer listening to my Altec 755As neat like a double shot of fine aged single malt or scotch, for certain well-recorded music, I hanker for richer harmonic overtones from the better spec'd Altec 755Cs.

Altec 3000H

My primary purpose for using a super tweeter is to enrich the zone where the 755C begins to lose sparkle, which is earlier than its older sibling, the 755A. The additive effect has to be subtle and nuanced. If crossed too low, its presence will be immediately apparent and too prominent. IME, this causes long term listening fatigue.

Altec 755C in a Silbatone box + Altec 3000H

To my ears, the Altec 3000H horn tweeter is a tough act to follow in reproducing the upper harmonics of a flute + the airy and lingering sheen of brushed cymbals, just to cite a few of its innate qualities. Unfortunately, the extremely fragile diaphragm, which produces the ribbon-like sound quality, can no longer be repaired because the jig for proper installation was lost. I'm writing about these tweeters for the sake of the few fully functioning samples in existence. This horn tweeter is for music lovers who appreciate the finer things in life!

CAVEAT: As good as the 3000H is, Altec 755C (or 755E) + 3000H doesn't = 755A 😉

Paper in Oil Caps

AFAIAC, this experiment can't be replicated properly using modern high tech plastic caps. If that's how you roll, you're on your own. 😜

Forget about crossover calculators because my crossover is very simple and the cap value is chosen by ear. Because of the very low values used, an L-Pad becomes redundant. For the 755C + 3000H = 0.5µf. I strongly recommend NOT exceeding that value for reasons already stated above. Since the Realistic 40-1375 is the least sensitive in this group, a 1µf cap sounded about right. With the Peerless MT225, I built up paralleled cap values to = 0.75µf. Always keep in mind that the proper blend between the super tweeter and the 755C is an exercise in subtlety and finesse. 

Realistic 40-1375

My Altec aficionado buddy, Mark H, has written quite favorably about this leaf tweeter in internet forums.

Sadly, I can no longer walk into a Radio Shack store to pick a pair of 40-1375s from the shelves, get my credit card imprinted by a Zip-Zap machine and go my merry way. 1986 was the final year this tweeter was listed in a Radio Shack Catalog. Thus, it took a while for me to acquire a pair. But it was well worth the wait.

As long as you don't expect ribbon-like performance, you won't be disappointed with this planar-type leaf tweeter. It's more honey-flavored than the Fostex FT17H derived Realistic 40-1310.

Peerless MT225

Peerless MT225

During our 2024 visit to Manila, I found this pair of MT225s in the attic. If memory serves, these were given to me by my late audio mentor, Tom Cadawas. Tom worked for Saul Marantz in Long Island City, NY. After Marantz left NYC, he collaborated with Mitch Cotter, Joseph Grado, Sidney Smith, Dick Sequerra and produced his own line of speakers under the Cadawas Acoustics brand.

This 2" paper cone/alnico tweeter should look familiar to those who read my Fulton FMI 80 article. It was also used by McIntosh, as well as in the early 80s iteration of Dick Sequerra's Metronome 7, KLH Research Ten Series Model CB8, CB10 and CL3B + many more. Peerless produced this cone tweeter well into the dome tweeter era.

Altec 755C in a Silbatone box + Peerless MT225

 Matsushita even produced its own version of the MT225. As Oscar Wilde said, "Imitation is the sincerest form of flattery that mediocrity can pay to greatness." 

Blending the Peerless MT225 with the 755C was practically effortless. In spite of the 755C's relative lack of snap compared to its older 755A sibling, I believe I would have had a much harder time finding a dome tweeter that would've harmonized just as well.

CODA

Western Electric 755A in an Open Baffle

At this point some readers, especially those who aren't well versed in classic speakers, are probably wondering about the discrepancy between the 70-13,000 Hz rating of a 755A vs. the 45-15,000 Hz of the 755C and 755E. I can only deduce that the 70-13,000 figure given by Western Electric was a much more conservative rating compared to when Altec became a wholly independent entity and had to compete in the open market. 

Next time an RTA wielding spec nerd tells you that the Western Electric/Altec 755A was designed merely for PA systems, remind the person that Edgar Villchur used this driver in 1954 as a midrange tweeter for his TOTL original and highly successful AR-1 acoustic suspension speaker. When Altec ended 755A production, It prompted him to develop a dome tweeter.