Ringing effect in midrange horn

[redwood forest]

I've heard that the Khorn midrange horn has a tendency to ring due to harmonic problems. Is this true? If so what can be used to eliminate this problem? I've heard that caulk or silicon around the horn will work. Is there any validity to this claim?

[WMcD]

I've pretty much stayed out of the argument. I made some midranges, variations on the K-400, out of plywood and believe there is no "ringing" problem with mine. Maybe there are other problems with my work. Smile.

Let me say that if there is a problem with "ringing", it is not one which would generate harmonics. They are two different things.

Some people with tap their cast metal midrange horns and hear a "ting" or the like. The solution seems to be coating the outside surface of the horn, the side inside the cabinet rather than open in front, with Moretite window caulking clay. It is well reported tweek. I can't say one way or the other, not having done it. I do have some suspicion that the problem and solution is overstated. But it does no harm, either.

If you poke around the forum, you'll see that Mr. Builder suspects some problems arising from minor casting imperfections. I don't know about that one either.

Gil

[artto]

In the Klipsch Audio Papers, A New High-Frequency Horn, IEEE Transactions on Audio, Vol. AU-11 No.6 Nov-Dec, 1963, Paul Klipsch describes the design of the K-400 horn used in the Klipschorn & LaScala as follows.

Previous experiments with metal horns indicated an undesirable ring or hangover. The K-400 experimental prototype was of sheet iron, coated with damping compound on the outside. This did not prove satisfactory. A further experiment with cast aluminum exhibited the undesired ringing quality, but when the necessary flange was attached in the form of 3/4inch plywood board, the resonances disappeared and no evidence of hangover was detectable by ear or measurement.

For what its worth, I have my midrange horns wrapped with several layers of Moretite rope caulk that is used for weather stripping as Gil described above.

As a side note:

My own experience has found that vibration of the overall speaker structure seems to be of more importance than any ringing that may remain in the metal horns after mounting the horn flange to the wood cabinet structure. The only explanation I can come up with is that the diaphragm excursion on the high & mid horn drivers must be moving such small distances, that vibration in the overall cabinet structure relative to those excursion distances is relatively large. Imagine, for instance, holding a speaker cone in your hand, moving it back & forth, & at the same time moving it up & down & around too. The result is a loss of definition, or blurring of the mid & high frequencies. The only practical (?) way around this is mass loading. That doesnt mean putting a 50LB rock on top of the speaker (the speaker already weighs 240Lbs). You can mass load the speaker by placing it on 3 of those machined speaker isolation cones made from brass or stainless steel. However, do not use the floor discs that often come with these. The idea is to increase the weight (mass) per square inch. This is maximized by having the cones tips resting on the smallest possible area. The floor discs may protect the floor from the very sharp point of these cones, but they defeat the very purpose of using the spikes/cones in the first place.

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7

The other method is to literally, physically secure the speaker structure to the building floor/walls, or even foundation. In my case, the Khorns are secured to the foundation of the house & the Belle center speaker is resting on 3 cones that poke thru the heavy carpet/padding to the concrete floor.

[JohnA]

With certain tones and female voices, I can (well, could) feel the throat of my metal K-400 horns vibrating. Early on, I posted questions about it and soon after wrapped the horns with Dynamat. The result was a much calmer, smoother, more relaxed sound. I may have been one of the initial causes of the discussions about damping. Several don't like the effect saying it makes the sound too lifeless. I do like it and believe it is impossible to overdamp any of the horns, or cabinets. The structure should not contribute any thing to the input signal.

The unmounted K-400 makes an outstanding bell, delivering a clear tone in the 500 Hz range with several overtones as the fundemental slowly dies. Mounting it to the motor board kills almost all of that, but there are still bits of it left.

Use Moretite, aka rope caulk, and if you don't like it, it is easily removed. It is apparently as effective as the Dynamat and much cheaper.

[jt1stcav]

Art, you said you use 3 isolation cones under your Belle Klipsch (with no discs). Does it matter where the cones are placed (1 in front; 2 in rear, or visa-versa)?

Are you familiar with Tekna Sonic C-12 vibration absorbers for subwoofers? These 5 sandwiched plates (in a single unit) is attached magnetically to the back of each cabinet, and are designed to remove distortion caused by low range vibrations in the cabinet (that make boomy bass and distorted midrange). See www.audioadvisor.com for a description. Just wonder if this is an alternative for rope caulk on the squawker...or the 3 cones, of course.

[artto]

Jim, I dont think it matters where/how the cones are placed other than to get the speakers weight balanced. I use 3 cones simply because its the minimum number of cones one can use without doing a balancing act & it puts more mass per square inch on the cones than 4 would, therefore increasing the mass load.

I have never see or used the Tekna Sonic vibration absorbers. I did however do a little research on it. I must say Im always a little skeptical of products such as these. I wasnt able to find any patent or REAL engineering information on it. A few things I did find were somewhat disturbing. Such as:

http://www.audioreview.com/Others/Tekna+Sonic+C-10+Vibration+Control+Absorbers/PRD_118089_1590crx.aspx#reviews

3 out of 6 reviews are favorable. 3 out of 6 are unfavorable. To me that means no difference.

And statements such as the following from

http://www.sonic.net/soundscape/teknason.html

when the TEKNA SONIC Vibration Absorber was placed on the back panel of the loudspeaker system all of the Harmonics were reduced significantly; the 2nd Harmonic was reduced by 17.3 dB. 17.3Db? Makes me wonder how much total harmonic distortion the speakers this guy was listening to have. That much reduction in harmonic distortion on a Klipschorn should bring it down to zero. LOL

Also from the same review: Editor Note: The better braced the cabinet the more dramatic the improvement. This statement is obviously flawed. Gets the yellow button award.

I dont see how this product could used in place of something like rope caulk on the horns. It appears to be an alternative to the cone spikes which are 1/5th the price or less.

[artto]

Last night I decided to do some vibration checking again. To make sure I had a good over-exaggerated bass continuously thumping, I used the Insane Clown Posse CD Bizaar. For those of you who are interested in finding out where any low frequency standing wave problems are in your room, this is the CD for it. Bootsy Collins will do too.

Anyway, even though my Khorns are literally, physically, bolted to the walls & foundation of my house for mass loading & vibration damping, it was amazing how much vibration was still present. In particular, the top unit that house the squawker & tweeter were vibrating much more than the bass horn. Subjectively, Id say at least twice as much vibration. The Khorns are secured to the walls/foundation via the bass horns rear tail board & a custom made tail board corner plate made from 2x12 wood.

Im going to do some experimenting to see if I can decouple the top unit better. At present I do not have the top unit bolted on (wing nuts removed) on one Khorn. The other has the wing nuts on, but not tightly. Just enough so they dont come off. The top units are resting on thin closed cell foam weather striping placed along the edges of the bass horn, primarily to seal the bass horn air tight. And who knows? Maybe coupling (instead of decoupling) them more securely to the bass horn is the thing to do.

[johnnyp]

artto,

I vaguely recall that PWK said that it was of upmost important that the upper cabinet of the K-horn be securely mounted to the bass bin.

As deaf as I am, I definitely heard a difference between one resting on top and one secured. So, I replaced the wing nuts with regular nuts plus fender washers, and tightened all assemblies with a wrench.

I think you'll hear a difference too.

[jt1stcav]

Art, thanks for the info...appreciate it. I kinda had my doubts about the Tekna vibration absorbers. If they worked as well as they say, I would think that everyone would use them!

As for the cones, I have the risers on my Cornwalls, and most big cones I find are only 2" long (so are the risers). I don't want to remove the risers.

Thanks again.

[Colin]

I wouldn't confuse the dampening that conventional cone speakers need with the more natural resonances of the horn loaded driver; vibraton in and of itself is not necessarily bad ...