1975 Klipshorn Upgrade: Qs on Ohms to drivers, Trachorn and ?1980s Mod'd AA Network

[nola]

I have a pair of "N" Khorns, so they should be from 1975.

While recapping the AA network, I decided to check the Ohms across the input leads to the drivers. Bob Crites has noted that the readings might become bad with age, etc.

Are the following values normal / ok for these drivers?

K 77 tweeter, reads as 6.6 to 6.7 ohms, regardless of physical connection to AA network.

k 55 v mid/squaker driver (to stock horn; smooth outer surface) reads as 0.9 to 1.0 ohms while connected to the AA network. 11.1 to 11.7 Ohms when not connected to AA network. Quite a difference.

K 55 M driver for ALK trachorn reads 10.6 ohms, not connected to AA netork. I was told the K 55 Ms were 4 yrs old.

I unscrewed the door to the woofer, but the ?gasket held tight and I was afraid to pry it loose and then not be sure what or how to reseal it. So i only tested it from the outer wire connector: 2.6 ohms while connected to the AA network, 3.7-3.8 ohms when not connected to the crossover network. Moderate difference.

Input wires from the McIntosh MC240 amp read about 180 Ohms at the spkr input strip.

For ease of testing, I ran 8 foot test leads out from the Khorn and AA network. I placed the ALK trachorn on top of the Khorn and tilted it down a bit. The ?timbre? was slightly different form the stock horn and driver. Seemed slightly louder too, when A - B testing it to the stock driver and metal horn. Didn't really seem to be a big difference. I only listened to a few things, though. Some soft - Dianna Krall, some hard - Led Zep. Both on DVD. MC240 tube amp. I ran the music with all 3 drivers connected per speaker. May try records and a SS amp later this week. Is there much of a difference between the K55 V and M drivers that might account for this lack of a major difference / improvement? Could also be that my 48 yr old ears are not what they used to be.

I recapped what I thought were the original KH AA networks: did only the LT one for now. My "T" LaScalas from 1979 have AA networks that look like the pics on Bob Crites website. But the AAs on the 75 KHs had different appearance. The caps were labelled: tan 12 uF +/- 5% / 200v, and I could not read the labels on the red-brown ?2uFs. They were solid / cylindrical - not oil filled cans. I wonder if they had been mod'd before I bought them (around 1988). Anybody, feel free to chime in.

Between the Crites / Sonicaps recaps - not much change in sound - compared to the untouched RT KH, and the ALK trachorn tests (again, LT side only for now), I was a bit disappointed. Not a big change in sound.

So: maybe the old caps were good - how do you test caps? Why the lack of major change with the wooden horn? Did a prior owner mod the AAs?

Thanx from New Orleans

[Steve Phillips]

They are 1975.

You should test impedance for a driver without the crossover connected. The impedance you suggested is within spec. We suggest between 6 to 8 for the tweeters, 10 to 12 for the mids and woofer between 3.5 to 4

The only way I know to test a cap, it takes a piece of gear most may not want to buy, possibly an electronics service center in your area can check.

2 uF caps were used, I have heard of a 12 uF in the circuit back then, it's within spec. 13 was what the network calls for.

[JohnA]

The values you measured, out of the network, for DC resistance (DCR) are normal.

When I bought my La Scalas, they were from different years. One had a K-55-V and Type AA, the other had a K-55-M and a Type AL network (awful!). i like the -V squawker, better and in the process of making them the same, I ended up changing the caps in the tweeter circuit to Hovland Musicaps. Nice, but not dramatic improvement. Well, if changing the tweeter caps helped, "let's change them all." Changing the 13 uF squawker cap made no difference at all.

I have a multimeter that can measure capacitance and inductance at about 400 Hz. The value measured is not necessarily the same at it would be at 6000 Hz, but knowing what it is at one point is beter than nothing. It cost me about $150. That's the cheapest you will find to measure caps and inductors.

Your old capacitors may not be bad. I believe if a speaker is used regularly, the capacitors will last longer than if it sits in storage. Maybe that's where your K-horns are now.

I also have a Model H from the 50s, I think. it had not been used for years and its caps were shot. I got little output from the squawkerand tweeter until I installed new ones. Now, it sounds very nice and is in my HT system.