K-77 or K-77-M

[castironandtubes]

I imagine this has been discussed before but I couldn't find a conclusive answer, so if someone has a second to clue me in it would certainly be appreciated. My '85 Heresys have ceramic square-magnet tweeters with the K-77 stamp on them. Are these the same as the K-77-M? Sometimes I see people referring to the K-77 as an alnico tweeter, I know that's not the case for me. Are there actually three different models or are mine K-77-M's just with a different stamp. Thanks.

Dave

[Malcolm]

There are two versions of the EV T35A tweeter used in Heresys. The first version, used from the late 50s through the mid 70s has a round alnico magnet and is labelled K-77. The second version, used from the late 70s until the end of production has a square ceramic magnet and was originally labelled K-77-M. The last ones used in Heresys, without the metal Klipsch medallion, may just be stamped K-77. But, they are the same thing as the ones labelled K-77-M.

[WMcD]

I'm not contradicting any of the above.

The K-77 tweeter was bought from Electrovoice by Klipsch. The EV nomenclature is a T-35. Most probably, that EV number refers to what EV thought was the lower cut off, 3500 Hz. The number shows up in EV specs.

Also, there are reports that PWK had some QC about what he would buy from EV. For one reason or another, the stuff coming off the production line would not always reach the upper end of the treble range. 15 kHz or so. So PWK was demanding the hand picked cherries.

I trust that that QC held true when EV switched magnets.

The alnicos were doing well. Generally round. But cobalt was a component of the magnet (Aluminum, nicklel, cobalt.) Cobalt mines in Africa shut down because of civil war.

The alternative was what is called a ferrite magnet. The process of making a ferrite magnet involves, initially, a slurry, which is baked or consolidated. Somewhat mud-like. So ferrite magnets are called mud magnets. Hence the "M". But this is almost guesswork.

EV had other variation on the T-35. Very early ones had no phasing plug; that little bulb in the center. Reading advertisements, it looks like at one time they had a T-35A and a T-35B. The latter was less efficent; perhaps their own rejects. And they had a T-35W, with a smaller magnet. And there was a larger T-350.

It is probably most fair to say that all the K-77x, round or square magnet, with or without badges, met Klipsch QC. Therefore, they are the very best of the art.

Gil

[TBrennan]

The T-35B was a completely different model than a A and had a smaller magnet. It is shallower than the T-35.

[WMcD]

I stand corrected, by the master.

I am a bit puzzled by the range of speakers in the T-35 family. It doesn't quite make sense to me to have a little brother unless the magnet material is expensive. I would think it is not, compared to everything else.

None the less, it seems that the T-35 W, in the cheapest form, did have a weaker magnet, and less sensitivity.

Gil

[Malcolm]

The TW35 was part of the Wolverine line. Besides all the flavors mentioned, EV built numerous OEM versions for other manufacturers

[Tom Mobley]

I have a question, I bought a couple t-35B on ebay thinking they were t-35. the magnets are definately smaller. I compared them to the known t-35s in my original Heresy's. Does anybody know what the difference in spec's is? Are the smaller magnet version really weaker dB-wise? poorer sound quality? Should I replace them with t-35s? these go in my DIY LS's, which I mostly listen to at low levels. Or should I just forget about the whole thing and run what I've got? I did put new diaphragms in both of them.

Tom

edit: typos

[Malcolm]

The T35B is about 4 dB less sensitive:

http://www.hifilit.com/hifilit/Electro-Voice/119-5.jpg