K-77Fs delicate as used in AK4 or AK5? Or not?

[garyrc]

Rumor has it that the diaphrams of the K-77Fs are lighter duty
than the K77Ms, that they resemble the old K-77s of the '60s that could
take repeated pulses of 4 watts (Dope from Hope), but were not as tough
as ones rated @ 5 wt continuous used in the '80s and '90s.

• In the AK 4 & 5 does the 36 dB/octave crossover slope (compared to the old 6 dB/octave slope) make up for this, i.e., did the old ones blow because too much midrange energy was let through by the shallow slope?
• Did they go with a thinner diaphram because it would respond more accurately within its power handling capacity?
• I used to really push my Khorns. In the last few years they have been in a rather small, bad, room so they didn't get turned up so far. It was during this time period that we installed the AK4 upgrade, Now we are moving them into a big (4,500 cu. ft) room, and we would like concert hall/movie theater levels. I guess I'm wondering how careful I need to be, given that the SPL at or above 4.5K is much lower than the SPL in the bass and midrange. Comments?

[Guest " "]

I don't think there is anything special about the coils in the k-77-Fs. I had a display model pair of khorns shipped to me straight from klipsch which arrived with damaged voce coils. Klipsch sent me standard k-77 coils to put in them. Don't think they would have done that if the coils were special.

The xovers in the khorns in question where eqiuv to AK-4's, so that tells me that none of the tweeter protection circuitry in that crossovers works. There's a poly switch and associated components.

[garyrc]

I don't think there is anything special about the coils in the k-77-Fs. I had a display model pair of khorns shipped to me straight from klipsch which arrived with damaged voce coils. Klipsch sent me standard k-77 coils to put in them. Don't think they would have done that if the coils were special.

The xovers in the khorns in question where eqiuv to AK-4's, so that tells me that none of the tweeter protection circuitry in that crossovers works. There's a poly switch and associated components.

If I understand your post, I see that the voice coils are probably the same. What I heard was that the diaphram itself is a little thinner...more like the old diaphrams. Way, way back, probably when Klipsch was using thin diaphrams, I remember PWK saying (somewhere) that moving to a heavier duty diaphram would not produce a tweeter "worth the name." Yet, I think the "M" diaphrams (that came out later) may have been heavier duty ....?

[djk]

The later EVs had a flat BeCu lead-out wire, superior to the ones where the VC wire ran straight to the solder lugs.

[garyrc]

The later EVs had a flat BeCu lead-out wire, superior to the ones where the VC wire ran straight to the solder lugs.

Do you know when (what year) EV changed to the flat BeCu wire? We actually have some old T35s (c. 1975 -1977??) in a home brew system in the bedroom that were used & abused in preferred SPL experiments @SFSU, and they seem indestructable.

[Guest " "]

" What I heard was that the diaphram itself is a little thinner...more like the old diaphrams. "

Understood. The voice coil is attached to the diaphragms. So when klipsch sent me a standard voice coil/diaphragm assembly for their 15K Khorn system, my assumtion is that the coils/diphragms in the 60th annivesary Khorn is interchangeable with all the proceeding models. I would think that Klipsch would not want to short change me on spec's by down grading me to a lesser coil, if the system used a different one.

I have seen strange looking coils in my days. One version has what looks like rope wire coming from the coils to the solder terminals. I have also seen more transparent looking ones.

[JohnA]

All of the reports and comments I have gotten from Klipsch was that the K-77-F was identical to the K-77-M, but with tighter tolerences in some places to ensure good VHF response. Adding a 36 dB/Octave crossover most assuredly makes them NOT FRAGILE. .Crank away.

No one has ever said the diaphragm were thinner, but since the voice coils and leads usually fail, a thinner diaphragm should not be a power limiting feature.

............... What I heard was that the diaphram itself
is a little thinner...more like the old diaphrams. Way, way back,
probably when Klipsch was using thin diaphrams, I remember PWK saying
(somewhere) that moving to a heavier duty diaphram would not produce a
tweeter "worth the name." Yet, I think the "M" diaphrams (that came out
later) may have been heavier duty ....?

From the K-77 to the K-77-M (T-35 to T-35A) the change was to the voice coil and connection leads, not the diahragm. The power rating changed from 2 watts continuous/20 watts program/40 watts peak for the T-35/K-77 to 5/50/100, same as the T350.

[garyrc]

Thanks everyone! So University bought the right to male T35As from EV? Or did the companies merge? Were the last K77Ms made by University?

[djk]

Telex rolled it all (Altec, EV, University, Gauss) into one basket, then divided it out as they saw fit.

EV drivers showed up in Altec product. EV product like the 30W, T35, 1824, 1828, 1829 showed up in the University line. Some EV horns showed up in the Gauss line.