K-400 vs. K-401

[tromprof]

I was reading an earlier post regarding the K-401 horn and it was mentioned how it is an inexpensive item and a nice upgrade from the earlier metal K-400 horn. Can anyone who has done this change share their thoughts on sound and ease of installation. Is it as easy as unbolting the old K-400 and dropping the K401 in, or is there some modification that would need to be done to my 1976 K-horns or the K401 horn itself?

[kg4guy]

I replaced both of my K-400's with the K-401's no modification easy to do as far as sound I honestly couldn't hear alot of difference .

[moray james]

I have had a number of Heresy K700 cast horns and none of mine have had clean open (round) throats. This has been as a result of old worn molds where there was considerable flash at the edged (inside) of the mold when cast. I was surprised that they were let out of the factory that way as several were probably in the range of 15 - 20% smalller in terms of the intended throat opening. Some of these I was able to file open and clean and one pair I had machined out to the proper size. You might want to check yours to see what they look like. The cast horns also suffer from ringing (my opinion) and benefit from damping with duct seal or rope cauld. This is easy and inexpensive to do. My guess is that if your horn throats look anything like mine have and if you open them up and damp the horns you will have the same quality of sound you would likely have if you purchase the plastic resin horns. Make sure that your metal adapter snouts have nor flanging either, all internal surfaces and connections should be ablolutely smooth and continous. That goes for the rubber gaskets, I trim mine with a long sharp exacto knife once installed tight in place. Any flanges or discontinuances at or near the throat cause turbulance and will cause considerable distortion. Hope this is of interest. Best regards Moray James.

[Groomlakearea51]

Drop-in replacement.

The issue with the 400's and "ringing" seems to be associated with certain castings as far as I could tell.

The 401's are certainly alot easier to work with in terms of weight and the precision machining of the throat areas, etc.

For Moray; On my 700's (I have about 20 pairs...), I have always "cleaned up" the throats with a dremel tool also. The most desirable of the 700's are the earlier "thick" castings. Resonance can be cured by simply drilling a 1/2" hole in the horn (about midway and off-center), and then putting a lead plug in the hole. Kills any ringing or resonance. I use old wheel weights and a bullet mold melting pot. Clamp a piece of metal to the bottom of the hole, pour away...

[H]

[tromprof]

Well, maybe I will wait on this. I am not trying to cure any problems, just curious. I wonder if this is a better mod for people who like it load (the ringing issue), as opposed to moderate listening levels.

[Groomlakearea51]

Another el-cheapo way to see if the horns are "ringing" or they sound better when completely dampened is to put some soft SCUBA weights on the horn. Couple of 3 pounders (they are basically in vinyl mesh bags). Or.... get a couple of old socks that do NOT have any holes... (and preferably clean....). Go buy a 10 pound bag of lead "bird shot". Smallest diamter... Pour about 3-4 pounds in the sock, tie the top, and place on the horn.

See if there is a difference in how the midrange sounds. If there was any "ringing", there won't be any now... LOL!!!

[H]

[moray james]

Groomlakearea51: that is indeed a cool fix though it might disturb some retentive ``I wanted it stock`` kind of guys. Have you ever compared this to Duct seal or rope caulk applications? I ask as that is 100% reversable. Also just one hole on one side of the horn? Thanks for the good idea. Best regards Moray James.

[djk]

To hear how much energy a horn is storing, and then re-releasing (ringing), I run FM inter-station hiss through the system at a very loud level for a very short time, and then punch the tape monitor button.

It's quite interesting to listen to the artifacts that some horns generate, some metal horns make a 'shwinggg' sound that rises in pitch as the energy decays, some plastic horns make a 'shlupp' sound as the energy decays.

I find it easier to damp a rigid metal horn that rings, as opposed to trying to add rigidity to a flimsy plastic horn.

[seti]

To hear how much energy a horn is storing, and then re-releasing (ringing), I run FM inter-station hiss through the system at a very loud level for a very short time, and then punch the tape monitor button.

It's quite interesting to listen to the artifacts that some horns generate, some metal horns make a 'shwinggg' sound that rises in pitch as the energy decays, some plastic horns make a 'shlupp' sound as the energy decays.

I find it easier to damp a rigid metal horn that rings, as opposed to trying to add rigidity to a flimsy plastic horn.

How loud do you have to play to generate this "shwinggg" ?

[Johnny's Jill]

Neither horn sounds better than the other, if you want better sound consider a Fastrac, if you are pleased with the sound, wrap the horn with rope caulk to resolve the ringing associated with the metal horn.

Craig 73

[Guest " "]

I can't hear the horn ringing.....the ringing in my ears must be masking it

[Daddy Dee]

After listening to K-400 horns for a while I put dynamat on them for damping. It helped with the ringing.

I installed K-401 horns just out of curiosity. Could not tell any difference in the sound. The K-401's don't ring.

[Groomlakearea51]

Groomlakearea51: that is indeed a cool fix though it might disturb some retentive ``I wanted it stock`` kind of guys. Have you ever compared this to Duct seal or rope caulk applications? I ask as that is 100% reversable. Also just one hole on one side of the horn? Thanks for the good idea. Best regards Moray James.

Reason I never liked the rope caulk was it seemed to be messy to get it on, and then messy to get it off.

The lead "hole" is on the top of the horn, about 1/2 of the way up from the throat, and centered. Did that a couple times, but that was also "labor intensive", and I had to sand them and re-paint them, etc.

Then having a bunch of 400, 500, 600 and 700's laying around, I started hanging the horns with two strings tied to coat hangers about 2 feet apart at either end (made them stay horizontal) and tapped them with a pokey-stick..... Some rang like a bell, some did not. Then I thought to myself, "Self? what do you do when you want a bell to stop ringing?" Well "cracking the bell" was not a good idea, so I simply added some lead shot to a sock, layed it it on, and that was the end of it.

That also allows the horn to be "I wanted it stock".

Of course there is no problem with a 401 or 701.... LOL!!

[H]

[mikebse2a3]

Then having a bunch of 400, 500, 600 and 700's laying around, I started hanging the horns with two strings tied to coat hangers about 2 feet apart at either end (made them stay horizontal) and tapped them with a pokey-stick..... Some rang like a bell, some did not. Then I thought to myself, "Self? what do you do when you want a bell to stop ringing?" Well "cracking the bell" was not a good idea, so I simply added some lead shot to a sock, layed it it on, and that was the end of it.

When you did these test did you have them mounted to a wood flange/baffle as they were intended to be used..?

PWK was aware of the possibility of metal horns ringing and if one reads the design paper for the K400 horn (can be found in the Audio Papers collection published by Klipsch...," IREE Transactions on Audio Volume AU-11, Nov-Dec 1963, Number 6") the wood flange was an integral part of the design.

To quote PWK from this paper:

"Previouse experiments with metal horns indicated an undersirable 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 3/4-inch plywood board, the resonances disappeared and no evidence of hangover was detectable by ear or measurements."

mike tn

Note: for anyone interested in experimenting with damping horns I have used sandwich bags loaded with sand as a cheap but very effective/reversable treatment when laid on top of the horn.

[JL Sargent]

What Fritz said. Some days worse than others.

[tromprof]

>Note: for anyone interested in experimenting with damping horns I have used sandwich bags loaded with sand as a cheap but very effective/reversable treatment when laid on top of the horn.

Thanks for this idea, I think I will give it a try.

[Chris A]

PWK was aware of the possibility of metal horns ringing and if one reads the design paper for the K400 horn (can be found in the Audio Papers collection published by Klipsch...," IEEE Transactions on Audio Volume AU-11, Nov-Dec 1963, Number 6") the wood flange was an integral part of the design.

Here is a link to the referenced PWK article on the "new K-400 horn".

Chris