Fixed L-Pads

[Zilch]

In terms of frequency response, I did some experimentation with cone drivers and tractrix horns and found that a tractix horn is effective (i.e. has a higher SPL output than the driver alone) for about 4-5 octaves at which point the reponse falls to what it was for the driver without the horn. I have never seen anything published on the frequency range of a tractrix horn.

Perhaps forum horn theorists can fill in the details, but I'd suspect the "rub" in attempting to use a 500 Hz Tractrix for extended VHF is severely compromised power response, as occurs with HL91 in the vertical.

That's why I'm asking dmtp to do some rudimentary polar response measurements once the boosted VHF is working. The hemispherical wavefront may behave differently up there....

[Robh3606]

as occurs with HL91 in the vertical

Hello Zilch

Actually that would be both axis. The lense is what changes the pattern otherwise it's a round horn so it would be symetrical. You should read this thread.

http://www.audioheritage.org/vbullet...ad.php?t=12967

Rob

[Zilch]

For horns with exponential, or Tractrix flare, the most rapid horn wall curvature changes occur towards the mouth of the horn, with the sides exhibiting less curvature near the throat. This means that waves will only diffract into the full angular coverage, defined by the exit angles of the mouth, for wavelengths which are longer than the axial length of the horn. For shorter wavelengths, the coverage pattern approximately conforms to the angle of the horn walls at the ½ wavelength axial position. For most of the other horn curves in fig 7, the angles range from 8°-12° at an axial distance of 3”, meaning that these horns (exponential, Tractrix, hyperbolic and spherical) will be unable to support a beam width of more than +/- 10° at 9kHz and above.

The refractive lens mitigates it in the horizontal, but at expense to the vertical:

http://audioheritage.org/vbulletin/s...9&postcount=74

[Robh3606]

Exactly so you end up with a focused beam on axis. Off axis you get nada above say 10K.

The refractive lens mitigates it in the horizontal, but at expense to the vertical:

Why at the expense??

Rob

[Zilch]

I was hoping Tractrix might defy some of that, but it looks in theory like the horn and driver throat size must be precisely optimized for a successful two-way design with extended HF.

The other thing I'm observing is that LE85/HL91 isn't all that flat in frequency response through the region they're commonly used here. I'll measure a bunch of 'em before concluding that, tho. Could be they'd benefit from a notch or two.

I don't have an agenda in this; I'm just following up on what's appearing in the routine course of doing these investigations....

[Robh3606]

No free lunch. You want horizontal, you pay with vertical.

Not so look at the conical lense. The serpentine and slat lense have minimal effect in that plane. You essentially go back to the horns directivity. Look at the directivity curve for the horn and horizontal pattern they mirror each other. They didn't plot the verticle but it would follow as the other plot does. That 22 degree and less wedge works in well with Jack quoted post.

http://www.lansingheritage.org/html/...nical/lens.htm

Well, I was hoping Tractrix might defy some of that, but it looks in theory like the horn and driver throat size must be optimized for a successful two-way design with extended HF.

This is Deja-vu. We going back to the 4430??

Well, for me it certainly is. I've kinda grown to like 50° vertical beamwidth, but a 20° listening slit is, well, "untenable" thus far....

Yes I tend to agree. One of the reasons I like the 2344 and the PT1010


Rob

[Zilch]

Not so look at the conical lense. The serpentine and slat lense have minimal effect in that plane. You essentially go back to the horns directivity. Look at the directivity curve for the horn and horizontal pattern they mirror each other. They didn't plot the verticle but it would follow as the other plot does. That 22 degree and less wedge works in well with Jack quoted post.

http://www.lansingheritage.org/html/...nical/lens.htm

I noticed that the DI didn't support what I was saying, but chose to ignore it.

[O.K., I get that now.... ]

This is Deja-vu. We going back to the 4430??

Naw, it's de riguer - PT Waveguides at ZilchLab.

For a symmetrical waveguide, the little work I did with the Engebretson indicated it "promising." Maybe I'll continue some with that:

http://www.ddshorns.com/catalog.php?page=ENG190Pro

If it's good, someone should document the profile for DIY.

["Family".... ]

[Zilch]

Why at the expense??

No free lunch. You want horizontal, you pay with vertical.

I had earlier concluded that extending the HF response with HL91 beyond these limits is consequently a fruitless endeavor.

Well, for me it certainly is. I've kinda grown to like 50° vertical beamwidth, but a 20° listening slit is, well, "untenable" thus far....