K-horn K-55/K-400 gasket

[jhawk92]

I'll be pinging the good folks at Klipsch for an answer as well, but thought folks here on the boards might be able to supply an answer before dawn.

I had pulled the K-55V drivers (as well as the K-77 drivers and crossovers) and sent them to BEC for his rework. They are on their way back to me, so I thought this would be a good time to do a bit of A/B comparison between the K-400 and K-401 horn. The K-401 horns did not ship with the rubber gasket, and I am able to pull the gaskets from the original K-400 horns in my speakers.

However, since these seem to be the original gaskets, are these still good to use? I don't know if a new gasket is more pliable, but these are a bit stiff. Since I've done a number of rework items, is it worth getting a new set of gaskets, or will the original ones still work for a while? Thanks much.

[wrench_peddler]

I don't know if the softness of the gaskets makes a difference and I don't know if what I did to mine makes a difference but here is what I did. I took the driver off the horn and trimmed the gasket with an eXacto knife so it was flush with the inside of the horn throat. It was hanging over into the hole buy about 1/8". I thought that would probably make a difference. The other thing I did was to take a butcher knife and use it to smooth out the uneven connection of the front half of the 401 horn with the back end. About half way back on the inside was a huge missalignment of the two halves on all four sides of the horn. I thought that would make a difference too. Couldn't tell if either one did anything but I felt smarter for having tried it.

[Frzninvt]

JHawk, those gaskets are old and brittle and should be changed. I bought about 10 of them from Klipsch not to long ago. Let me dig up the part number for you. If you want I'll even mail you a new pair for your speakers. They were like 10-15 cents apiece from Klipsch I think. I did the same thing I replaced them when I swapped out the K-400's for the K-401's.

[jhawk92]

Frz-

A part number would be great, as I think I'd like to have some spare gaskets available for future use. I figured it would make sense to change mine out, as it looks like these are original, so 36yo gaskets are probably on their last legs. Any idea how often they should be changed? I would assume it is years, so maybe this is like a 10yr/100,000 mile check item?

Wrench-

Interesting observations. I'll have to check under the hood this evening and see what I can find.

[Dflip]

The gasket you are talking about, is it the one between the horn and the magnet on the speaker, or do you have one between the horn and the front of the cabinet? I would appreciate the part number as well.

Thanks in advance.

Don

[jhawk92]

Dflip-

I am talking about the one between the horn and the driver. I don't know if there is (?) one between the horn and the front of the cabinet. I'll probably find out tonight as I plan on mounting one of the K-401s in preparation for later events. There wasn't one when I pulled the K-77s off, so I don't think there will be on the mid-range horn.

[Daddy Dee]

Jhawk,

I'll be interested to hear what you think about the K400 vs K401. My KHorns now have the K401's, but it seemed too much like work to do really serious comparison in sound.

[Dflip]

I am talking about the one between the horn and the driver. I don't know if there is (?) one between the horn and the front of the cabinet. I'll probably find out tonight as I plan on mounting one of the K-401s in preparation for later events. There wasn't one when I pulled the K-77s off, so I don't think there will be on the mid-range horn.

The only one I have found is between the driver and the horn, but I needed to ask to be sure. I have had both the horns removed and done some clean-out around the grove in the magnet. You have to take off the driver first to do this and then use tape and a sharp thin edge to remove the filings that accumulate in the groove. I'm sure mine could be replaced, I don't know what if any sonic benefits there are to doing that.

[BEC]

This might be a good place to post a finding on Jhawk's K-55s. I recently had them on my bench for testing. The idea was to see if there was something to be gained by replacing the diaphragms in these K-55Vs, even though they were still working and working well after 36 years. I put them on a k-400 horn and drove the K-55Vs with a sweep of 20 to 10Khz at about 1 watt and looked at the output with a calibrated mic connected to a spectrum analyzer.

The intent was:

1. Test each of the old K-55Vs.

2. Test a new Atlas PD-5VH as a reference.

3. Replace the diaphragms in the old K-55Vs.

4. Retest the old K-55Vs with new diaphragms installed.

Findings:

1. Man, with one watt a K-400 is LOUD.

2. Steps 1 and 2 from above produced 3 traces that were so close to identical in every respect that the test was stopped. It would be impossible for steps 3 and 4 to produce a result that could show improvement.

I will go ahead and say that these findings are not what I expected. I thought I would find that over the 36 years the effect of some age related changes to the diaphragms would be measurable.

My thanks go out to Jhawk for allowing this test to be done. He was willing to "foot the bill" for the diaphragm replacement to see how this would work out. Turns out that we got a pretty good proof on this subject without him having to spend the money.

Bob Crites

[jhawk92]

Dee-

I'll be sure to let the forum know. I do have a slight problem. I pulled off on of the K-400 tonight. Boy, what a pain that was. The two nuts on the bottom were hard to reach, so after pulled off the K-400, I also unscrewed the entire front mounting board (four screws, two on each side) which includes the cane grill cloth. Then I flipped the board on its face and tried to mount the K-401, but the two screw holes on the sides (horn laying horizontal) are about 3/8" too far out in comparison to the existing mounting screws. The other holes will match up ok, but these two on the sides will require drilling new holes.

I figure just a regular drill bit should do the trick, but if anyone has any warnings before drilling in the composite, I'd be happy to hear them. I was going to try drilling tonight, but I want to do it when I am not as tired, so I'll do it tomorrow right after work. And yes, once the K-400 is no longer attached, it certainly does ring like a bell.

Bob-

Thanks for your efforts on these. Even though everything hasn't arrived back here yet (should be tomorrow), I have been very pleased with Bob's service and support. As he mentioned, I sent the K-55V drivers out to him, figuring they would need re-diaphragm-ing like the K-77Ms.

While the K-77s needed work, I was pleased to find out the K-55s did not. Bob called me after this testing to ask what I wanted to do, but before he did anything else. I'm glad he was straight with me and said that he didn't think replacing the diaphragms would make any difference, so I opted not to do the work. It was nice to have that choice!

I'm looking forward to getting things back reassembled, especially the one without a HF cabinet! I've got K-horn parts spread all over the family room, so I'm glad SWMBO is out of town and I have room to spread out.

[jhawk92]

A call to Klipsch Tech Support yielded good results. Steve^2 said elongating or drilling new holes shouldn't cause any problems, so I'll be working on that tonight. They had a good recommendation to put some masking tape on both sides of the flange so as to prevent any extra damage as the drill goes through. I was going to drill into a piece of wood, but will do both now.

They gave me the part number for the gasket too; called a Driver Gasket, P/N 157041. They are $0.19 each, so I got 8, to have some on hand. Minimum shipping is $5, but they should be here early next week. For now, I'll get the 401 mounted with the old gasket and then replace when the new ones arrive.