1" versus 2" - A Different Perspective

[greg928gts]

I plotted two horn designs today, to make a comparison between them. Both designs have a Fc of 260Hz and identical mouth sizes, but one is a 1"-throat horn and the other is a 2"-throat horn.

Greg

[greg928gts]

The 1"-throat horn is 5" longer than the 2"-throat horn, all in the throat area. I know there might be technical reasons for not needing a 2"-throat horn/driver in a home environment, but there are subjective reasons. My intuition tells me which horn will sound the best, especially considering the quality level of the new larger-format drivers available these days.

Greg

[greg928gts]

Hmmmm

[seti]

The b&c de82tn is a 1.4 inch so it is in the middle. I understand pwk picked this driver. [EDIT] What I meant was pwk was exploring pro drivers when he picked the b&c and could just have easily gone with a 2 inch so what made them pick the 1.4 inch? I've been running it for many months and really like it. I can't say it is the throat size I like but the driver sounds nice.

[Deang]

"My intuition tells me which horn will sound the best, especially considering the quality level of the new larger-format drivers available these days."

Al's Trachorn has a cut-off of 300Hz, and it's much shorter than your 1" 260Hz template. I never would have thought that 40 cycles would add that much length to the horn. Interesting.

Some people say that the long narrow throat of the K-400/401 is responsible for the harshness people hear at moderate and louder listening levels (air overload distortion). Changing to a different driver doesn't help. OTOH, the entry of the throat for the K-400 is just over a 1/2" in diameter.

I bring this up because I see that long throat and wonder if the 1" driver will be handicapped from the outset.

[Marvel]

I thought you could actually cut off the excess length, where the area stays the same. I know I've read that somewhere. Whether they knew wha they were talking about is another story.

Bruce

[cjgeraci]

The template of the one inch horn has a narrow long throat, and as a result, it appears as though this is not a fair fight as being proposed - at least as the one inch horn is concerned.

I agree with Dean. My one-inch Trachorns from Al are much shorter, and the throat size is much less constricted (as comparison to proposed). Al's horns are smooth as silk and effortless at all volumes.

In comparison, I have tried the K400 with different drivers: to painful results due to the narrow throat.

Carl.

[greg928gts]

I agree with what is being said here, that the longer constricted throat is problematic. I can hear it just by talking into various horns, and certainly by listening to them.

I've been playing around lately with various test throat adapters (basically small horns) with various lengths 4" - 7" long, and various angles of expansion, and drilling them out with different size holes, etc... It's been quite a learning experience. I'm doing this so my customers can add this adapter onto the end of the V-Trac horn and use their k55 drivers until they have the money to step up to the larger drivers.

I had one that I made that was about 5" long, and I started by drilling a 5/8" hole in it, then spoke and sang through it (nobody was around to hear my singing, which is a good thing!), then increased the hole size to 3/4" and it actually sounded different, then increased to 7/8" and finally 1" and each time this small "horn" actually kept getting better sounding as the throat got larger.

I think this is one of the primary reasons the Fastlane LS horns sound better than the K400, even with the K55 driver. Shallower horn, the adapter used has a 1" hole that feeds right into the 1" square throat, there's no restriction to the sound in the throat of the horn, no overloading in the throat area, and the sound can make its way out very quickly and easily.

I remember djk saying that he once cut the throat off the end of K400 and mounted a 2'" throat driver on the end with good results.

So why did PWK use the long constricted throat on the K400? Why does any design call for it? Does it provide more gain? If it does, I think it does so at the expense of coloring of the sound.

I think a shallower horn is doing more to "steer" the sound into the room than it is to amplify the sound. This was evident to me when I listened to the BMS drivers alone on top of my Khorns. The tonal qualities and overall sound from the drivers alone was very much like when they were installed in the Fc260 horns. The imaging was not there at all, but the sound was. Adding the horn had a minimal affect on the overal tonal quality. The horn was doing a very simple job of dispersing the sound into the room. The driver was responsible for the tonal qualities of what I was hearing.

In other words, it's not as much that the horn is making the improvement I'm hearing with the V-Trac horns in my Khorns, it's more the lack of a long constricted throat that allows the driver to provide a greater proportion of the sound I'm hearing from the midrange. On balance, less horn, more driver.

Greg

[seti]

If you look at pwk's last horn as compared to the k5 there is no extension. This doesn't seem to be a Klipsch only change but industry wide. Consider the tad 4002 driver it has an extension tube on it before the horn. If it were such a bad idea I serously doubt TAD would do it? I don't have the education in acoustics or physics to critique one design over another but I do love to listen to them.

[sootshe]

"I agree with what is being said here, that the longer constricted throat is problematic.  I can hear it just by talking into various horns, and certainly by listening to them. I've been playing around lately with various test throat adapters (basically small horns) with various lengths 4" - 7" long, and various angles of expansion, and drilling them out with different size holes, etc...  It's been quite a learning experience.  I'm doing this so my customers can add this adapter onto the end of the V-Trac horn and use their k55 drivers until they have the money to step up to the larger drivers."

Greg, I agree with your theory here...I've been doing some experimenting here with my K55's mounted to an ALK Trachorn. I first removed the bug screen & noticed a considerable improvement in detail, then I removed the rubber washer between the driver & the horn...again a noticeable improvement. On closer inspection I notice that the Selenium Adaptors (APT 25-25) have a length of 25mm in the neck of the adaptor, whilst the threading on the K55 is only 13-14mm, leaving a nominal distance of 11mm of extra length before the sound actually enters the horn flare. I could hear a difference when I removed the washer in this area so I'm wondering what it would sound like with the driver feeding directly into the horn flare. Does anybody know where you can get adaptors for the K55 that are only 12-14mm long in the threaded neck, so that when you screw the driver on ......the exit from the driver feeds direct into the horn flare?

[greg928gts]

Does anybody know where you can get adaptors for the K55 that are only 12-14mm long in the threaded neck, so that when you screw the driver on ......the exit from the driver feeds direct into the horn flare?

I wonder if you could get a tap and tap it right to the end?

It might crack apart instead of cutting the threads.

Use a 1" threaded coupling and figure out a way to glue it to the end of the horn with epoxy?

Greg

[Klewless]

"So why did PWK use the long constricted throat on the K400? Why does any design call for it? Does it provide more gain? If it does, I think it does so at the expense of coloring of the sound. "

I believe the longer mid horn was based on lowering the cutoff frequency from 500 Hz to 400 Hz. Standard "horn theory": lower freqs means longer wavelength means longer horn. Tradeoff means more beaming of the high frequencies.

[Don Richard]

So why did PWK use the long constricted throat on the K400? Why does any design call for it? Does it provide more gain? If it does, I think it does so at the expense of coloring of the sound.

The flare rate (length to double area) determines the low freq cutoff of an exponential horn. When one uses a sub 1" throat that is a lot of extra doubling versus a 2" throat horn. While that makes the horn suitable for 400 Hz operation it does increase harmonic distortion at higher freqs. I believe the K-400, as are most exponential designs, is constructed to increase efficiency

I think a shallower horn is doing more to "steer" the sound into the room than it is to amplify the sound.

This is exactly what Earl Geddes was saying in his "How Horns Work Revisited" paper that was linked in a recent post on this forum. The point of his paper was to show that maximum efficiency, as a design goal, is not as necessary in this age of high power amplification. What he says, and what many manufacturers are doing, is to use midrange and higher horns as waveguides instead of as acoustic impedance matching devices. The benefits are better directional control and lower distortion.

[sootshe]

Does anybody know where you can get adaptors for the K55 that are only 12-14mm long in the threaded neck, so that when you screw the driver on ......the exit from the driver feeds direct into the horn flare?

I wonder if you could get a tap and tap it right to the end?

It might crack apart instead of cutting the threads.

Use a 1" threaded coupling and figure out a way to glue it to the end of the horn with epoxy?

Greg

Yes, if you tapped it right to the end you could then cut the excess length off & have the horn exiting right at the start of the flare, but you'd have to be very careful cutting the thread....will look into that one.

[greg928gts]

This is exactly what Earl Geddes was saying in his "How Horns Work Revisited" paper that was linked in a recent post on this forum. The point of his paper was to show that maximum efficiency, as a design goal, is not as necessary in this age of high power amplification. What he says, and what many manufacturers are doing, is to use midrange and higher horns as waveguides instead of as acoustic impedance matching devices. The benefits are better directional control and lower distortion.

That is SO interesting.

Greg

[greg928gts]

Yes, if you tapped it right to the end you could then cut the excess length off & have the horn exiting right at the start of the flare, but you'd have to be very careful cutting the thread....will look into that one.

What if you found a 1" nut with the correct thread and epoxy glued it to the end of the horn?

Does anyone know the thread/pitch of the K55 driver?

Greg

[Guest David H]

Does anyone know the thread/pitch of the K55 driver?

1-3/8" 18 TPI

[deafbykhorns]

If its 1-3/8, could the throat also be drilled out to give a true 1" opening? Its not like this is holding any water pressure

[sootshe]

Yes, if you tapped it right to the end you could then cut the excess length off & have the horn exiting right at the start of the flare, but you'd have to be very careful cutting the thread....will look into that one.

What if you found a 1" nut with the correct thread and epoxy glued it to the end of the horn?

Does anyone know the thread/pitch of the K55 driver?

Greg

Yes, thats the go.....If I can find a nut the right size I'll glue that to a round plate or even get it spot welded to the plate for extra strength & then I can screw the whole assembly to the Trachorn in the existing holes.....that will keep the Trachorn unmolested & I can go back to stock or change drivers at any time in the future.

Thanks Greg,

John[]

John

[gaspr]

Does anyone know the thread/pitch of the K55 driver?

1-3/8" 18 TPI

This could be tough to find...standard fine thread for 1-3/8" is 12 TPI ....

(edit) Look for UNEF extra fine thread.