Hey Lascala, your Tractrix is showing.

[Guest David H]

The Fastrac Lascala project is the byproduct of input from forum members. At first, I wasn't even sure it could be done, however after a few phone calls with JWCullison and a dozen emails to Al Klappenberger I was convinced a Tractrix horn that fits in a factory Lascala cutout was not only possible but a really good idea. Now comes the hard part, design and execution. The design and math for this still eludes me, so I have to thank JWCullison for taking the time out of his unbelieveably busy day to design this fantastic horn. The execution is a good way to describe how I felt after spending 20+ hours in the garage building the tools and Jigs necessary to produce this horn.

I also have to thank Paul B for allowing me to experiment on his Lascala's, Johnny 5 for his time and ears, Greg928gts for his shared ideas, one heck of a sander and keeping this horn on the DL while it was undergoing tests.

[Guest David H]

Here is a side view of the Fastrac Lascala. Because it is a Tractrix design, its total length is only 11" deep for an Fc of 384hz. Correction, thanks to a dope from hope artice, shared by ALK, I was able to drop the Fc to 354hz and occupy the same space.

[Guest David H]

The donor speakers, Paul is a good sport about letting me modify his Lascalas, but he is absolutely thrilled with the results.

[Guest David H]

I had to remove the crossover to install the horn a tilt is a hair to clear the tweeter mag, but overall and simple installation.

[Guest David H]

And the winner is........Yeah its the Fastrac.

[Guest David H]

Close up view.

[Guest David H]

A pic of the well known K-400

[Guest David H]

Here is the response curve of the Fastrac Lascala, driven by a K-55.

[Guest David H]

Same test using the K-400

[jwc]

Those curves look good. The only way on that horn that I could get a lower Fc was to truncate the horn..........I don't want to do that. I would rather have it pure tractrix from throat to mouth.

Looks good. Should be an easy swap out...and use the K55.

Heck...it still looks stock!

jc

[greg928gts]

That's great work Dave, you've got a winner there.

So easy to change out the K400's for the Fastrac, and the K400's will bring some money on ebay to offset the costs.

With a 500Hz crossover point, the Fc384 is just about right.

Greg

[Blvdre]

Great idea for those who want to keep their LaScalas stock, but upgrade the mid-horn. This is the first drop-in upgrade I've seen.

[jwc]

Gothover

On your curve...where did the fast track start to dive? 425-435Hz?

jc

[Guest David H]

Gothover

On your curve...where did the fast track start to dive? 425-435Hz?

jc

Roll off started to occur at 425Hz, but was less than 10db down at 400Hz.

I sent these curves to ALK, he was confident his universal crossover would work fine with these, but said the 500Hz es network would be the ticket.

[Guest David H]

That's great work Dave, you've got a winner there.

So easy to change out the K400's for the Fastrac, and the K400's will bring some money on ebay to offset the costs.

Thanks Greg, I didn't consider loosing the K400 for $$$ on EBay.

[Guest David H]

I would rather have it pure tractrix from throat to mouth.

Good call.

Heck...it still looks stock!

Hmmmmm they don't sound stock. [<)]

[Marvel]

This is the first drop-in upgrade I've seen.

I would considerthe CT125 the first for horns, but for the mids, what a sweet deal!

Right when I thought I might not do more for my LS. []

[Arky]

Man that's sweet, would love to hear it.

[Guest David H]

I went over to Pauls again tonight to do some more listening, we were both amazed at the increased detail, especially at low levels.

[Blvdre]

This is the first drop-in upgrade I've seen.

I would considerthe CT125 the first for horns, but for the mids, what a sweet deal!

Right when I thought I might not do more for my LS.

You are, of course, correct (I was thinking mid horn, but that thought didn't make it to the keyboard). In fact, I'm now looking to sell my APT-200's, and pick up a pair of CT125's. "Oh Bobbbbb......"