2" 223Hz tractrix horns

[DrWho]

getting down to 80Hz would probably be cutting it with a tractrix horn

So you are with the belief that tractrix can't go that low? I thought we discussed this on the forum before. What was the reason why it can't?

Negative. I just think a tractrix would need to be extra large for that particular driver. I firmly believe that one should always maximize power transfer, so according to Roy and Post tractrix is always the way to go. I also like how tractrix behaves below the Fc.

I'm gonna be out for most of the weekend so won't get around to crunching any numbers any time soon, but I'm definitely interested in more discussion.

Ya, 6dB down at 800Hz...80Hz is easily hittable though. The impedance plot that B&C provides shows that it'll start rolling off at 500Hz. I'd like to see a driver that starts at 800Hz (almost an octave higher), which would mean about half the inductance as the 12PE32.

[jwc]

Yep. I'm following you with that. If I remember correctly the K31 rolls off sooner with Hornresp.

Would you say 12" is out of the question. All of B&C 12" has the impedance swing about the same place.

18 sound and ciare have a bunch of stuff that I think I pondered over in the past. On vacation right now......can't pull those up.

Well. I'm building a pair of tractrix horns right now to go down to 80Hz with dual K31's. Want it to go to 600Hz. The mouth is 45 wide and 35 tall. Horn length is about 24". Straight horn. "Full Space". Throat 90 sq in total. It will also accept dual 10" drivers.

Give me yur thoughts there grasshopper. You realize we discussed this before when you wanted ideas about you project with the JBL woofers....horn vs bass reflex.

jc

[DrWho]

Yep. I'm following you with that. If I remember correctly the K31 rolls off sooner with Hornresp.

Would you say 12" is out of the question. All of B&C 12" has the impedance swing about the same place.

18
sound and ciare have a bunch of stuff that I think I pondered over in
the past. On vacation right now......can't pull those up.

Well.
I'm building a pair of tractrix horns right now to go down to 80Hz with
dual K31's. Want it to go to 600Hz. The mouth is 45 wide and 35
tall. Horn length is about 24". Straight horn. "Full Space". Throat
90 sq in total. It will also accept dual 10" drivers.

Give me
yur thoughts there grasshopper. You realize we discussed this before
when you wanted ideas about you project with the JBL woofers....horn vs
bass reflex.

jc

The plot below is close to
the polar response you can expect from a 12" driver at 500Hz and
1kHz...it's gonna be a bit different for a real driver and you could do
phase plugs and smaller throat sizes, but if you beam too much then the
driver kinda ends up not seeing the horn at all. I think 12" would be
the largest I'd consider.

As a sanity check, Klipsch is claiming
170Hz-1kHz ± 3dB from the KPT-XII-MB (which uses a 12" driver) with a
DI of 8dB ± 2dB 250Hz-1.6kHz. That would imply a DI of 10dB at 1.6kHz.
You'll also note that the mouth area is about half that of the 12"
driver, which is also close to the ka=3 plot shown below. So I don't
think I'm guessing too far away from reality.

I don't think dual 12's are optimal in this case and I don't think
going to dual 10's will gain you much since the center points will be
the same distance apart. Or maybe you're doing something different to
bring the bubbles together nicer? Like maybe firing into a common
throat or manifold? But then you are talking 600Hz so maybe you'll get
away with it...I don't like to be right on the edge unless I know for
sure it'll meet expectations.

It'll be interesting to see your results - have you started already?
I've been thinking about maybe building a midbass before a basshorn
since it'll be easier to obtain semi-anechoic measurements. I've often
toyed with the idea of direct radiating bass below 80Hz and then
hornloaded midbass up to 800Hz and then 800Hz to 20kHz with the tweeter.

I was just thinking, more surface area will give you lower
distortion at lower frequencies, but your HF will be limited on how
well you can avoid phase cancellation of the higher frequencies.

[jwc]

Like maybe firing into a common throat or manifold?

yes..I squench the center of dual throats as close as possible. Infact.....the woofer frame of the two are almost touching....about 1-2mm apart. They fire into a common horn.

The horn part of both is close to being done. The woofer chamber barely assembled.

jc

[DrWho]

Did you angle them at all, or are they both mounted "normally"?

[jwc]

I see where you are going now.

Nope...fire straight forward..."normally". Horn expands vertically and horizontally....unlike the previous bass horn I posted.

jc

[Guest David H]

JW, do you have any plans for 1.4 inch horns? I have received a few inquaries about them.

I personally think the midtrax with an adapter would be the ticket. Love them with K-55's

How are your newest plans coming along?

[jwc]

I'm out of town right now...will return home soon.

I haven't been able to work on the other project we spoke of except for a little. But I'll get to it. Excited about that one.

Any other thoughts of your "riser" for the 223?

I don't have plans for a 1.4" throat for this horn. But I can come up with it. May take a bit as I've got other things on my plate.

jc

[DrWho]

I personally think the midtrax with an adapter would be the ticket.

I don't think the adaptors are a free lunch....On the few horns I've heard with and without adpators, you can tell that there is some kind of funkiness that they impart.

It shouldn't be that difficult to scale the horn down to 1.4" if you wanna go that route...

[Guest David H]

Any other thoughts of your "riser" for the 223?

Yes, I don't love it. I think this horn belongs in a box, I kept the template but scrapped the project.

I don't have plans for a 1.4" throat for this horn. But I can come up with it. May take a bit as I've got other things on my plate.

Not a problem, I am of limited time myself. I am building a VTA SP-6 preamp hopefully this week if all of my parts come in. I think I will do a build thread while I am at it.

haven't been able to work on the other project we spoke of except for a little. But I'll get to it. Excited about that one.

Me to but my back hurts just thinking about it.[]

[Guest David H]

I personally think the midtrax with an adapter would be the ticket.

I don't think the adaptors are a free lunch....On the few horns I've heard with and without adpators, you can tell that there is some kind of funkiness that they impart.

It shouldn't be that difficult to scale the horn down to 1.4" if you wanna go that route...

I am sure you are correct, I have not heard anythig objectionable so far, but I am sure a properly designed horn for a 1.4 driver would be superior.

[tigerwoodKhorns]

Gothover,

What is the change in length of the horn going from a 2" to a 1.4" or even a 1" driver?

I ask because an adapter does not have to be a bad thing. You already have the equation. You can make say 3/4" thick pieces of wood and scribe out the input and output specs, drill a good size hole in the center and then file to fit the equation. You may need to glue a few together (reinforce with screws since they wil be supporting the driver). That way you can maintain the equation and have a versitile horn that will work with 2" drivers or smaller.

This is basicaly what Edgar did in his article but he went the other way. He started with a small driver then started chopping off sections of the horn for larger drivers. If you remember, he also used 1" wide pieces of wood instead of bendable plywood for the sides. I'm sure the above is at least as accurate as what Edgar did and lets face it, engineers can get too caught up in following an equation exactly when the equation is simply a model that has a big margin or error in any event. In the field there are always small (and soemtimes large) variations.

[Guest David H]

What is the change in length of the horn going from a 2" to a 1.4" or even a 1" driver?

The horns vertical taper is a continuous 32 degrees, but the horizontal taper is near 0 degrees at the last 3 inches of the throat. I can see what you are gettting at, but because of one one flair being constant and the other tractrix, I would not know how to accomodate for the change. I do however agree the change in length would be minimal.

Throat 2"

17.5"------------------------------------------------------------------------------------------------ 12"

17" ------------------------------------------------------------------------------ 9.50"

16" --------------------------------------------------------------------- 6.95"

15" -------------------------------------------------------- 5.53"

14" ------------------------------------------------ 4.55"

13" ------------------------------------------ 3.73"

12" --------------------------------------- 3.17"

11" ----------------------------------- 2.72"

10" --------------------------------2.36"

9" ---------------------------- 2.04"

8" -------------------------1.78"

7" ----------------------1.57"

6" --------------------1.39"

5" ---------------- 1.25"

4" -------------- 1.14"

3" ------------ 1.06"

2" ----------- 1.0"

1" ---------- .97"

0" ----------- 1.0"

[tigerwoodKhorns]

What does the profile look like for a 1" driver?

I assume that you cannot maintain the 1/32" hump at 1" from the driver unless you do that with a file. So does the horn wind up being 1" (2" total) from 2" down to the driver?

If you do maintain the 1/32" hump (0.03") at 1" I am guessing the profile for the 1" driver and the 2" driver are identical from the point marked 2" here (which will be some number greater than 2" on a 1" driver profile). If you make the adaper start there you will have a 2" long adapter for a 2" driver and longer adapters for 1.4" drivers and 1" drivers. It should work.

Please post the profile for a 1" driver if you have it.

Did the issue of the tilting of this piece ever get resolved.

[Guest David H]

The one inch horn from 0-2 inches is 0=1" 1=.97" 2=1.02" roughly. I really see no way to adapt this horn, other than fudging.

Currently my adapter is a .5 inch thick piece of mdf with a 1 hole drilled in it, then I bevelled it out to approx 1.75 inches. I know this is not an Ideal adapter but it sounds prety good as it is.

Did the issue of the tilting of this piece ever get resolved.

You lost me here.

This may be another option: http://cgi.ebay.com/Horn-adapter-for-Altec-Driver-1-4-to-JBL-Gauss-TAD-2_W0QQitemZ140294783610QQcmdZViewItemQQptZVintage_Electronics_R2?hash=item140294783610&_trksid=p3286.c0.m14&_trkparms=72%3A1234%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318%7C301%3A0%7C293%3A1%7C294%3A50

[tigerwoodKhorns]

Did the issue of the tilting of this piece ever get resolved.

You lost me here.

Check out this thread:

http://forums.klipsch.com/forums/t/113409.aspx

It makes sense, the equation seems to be for the center of the horn, not the top and bottom pieces, so an adjustment needs to be made. Either (1) Edgar made a mistake and did not notice this, (2) Edgar did notice and thought that it was not a big deal, or (3) the thread is wrong and the equation does account for the angle.

[Marvel]

It makes sense, the equation seems to be for the center of the horn, not the top and bottom pieces, so an adjustment needs to be made. Either (1) Edgar made a mistake and did not notice this, (2) Edgar did notice and thought that it was not a big deal, or (3) the thread is wrong and the equation does account for the angle.

I thought it was mentioned that Edgar did notice this. Al's Trachorn is the same way, getting slightly narrower close to the throat. Since the top and ottom are a constant angle, close to the throat, the sides must come in more to maintain the tractrix expansion area.

That is what you are asking about, isn't it?

If the top and bottom were to have a flatter angle close to the throat, the sides wouldn't have to come in narrower at the one inch mark.

I hope I'm not just confusing the issue. I believe Gil had pointed out the reason, previously.

Bruce

[Guest David H]

That is what you are asking about, isn't it?

If the top and bottom were to have a flatter angle close to the throat, the sides wouldn't have to come in narrower at the one inch mark.

That actually makes sense to me. But just to be clear you are saying the constant vertical expantion grew to fast, so an adjustment had to be made in the horizontal flair near the throat.

[greg928gts]

Did the issue of the tilting of this piece ever get resolved.

You lost me here.

Check out this thread:

http://forums.klipsch.com/forums/t/113409.aspx

It makes sense, the equation seems to be for the center of the horn, not the top and bottom pieces, so an adjustment needs to be made. Either (1) Edgar made a mistake and did not notice this, (2) Edgar did notice and thought that it was not a big deal, or (3) the thread is wrong and the equation does account for the angle.

This is such a hard issue to describe in writing. I think JC and I finally came together on this one. I think we might have been thinking the exact same thing all along, but the communication was not conveying our thoughts so that we both understood one another.

Anyway, the calculation from the volvotreter website is figuring the center plane curve of the side of the horn (probably all tractrix calculators are doing it this way). JC has come up with a method that adjusts the math so that the curve that is plotted on graph paper is the "flare" curve, which is the inside joint between the top piece and one of the side pieces of the horn (or any of the other three joints for that matter). The flare curve is slightly different from the center plane curve.

I plan to update the other thread once I've had a chance to review the process from start to finish, for myself, and make notes so I'm able to do this again in the future. It's going to be difficult to put into words though.

Greg

[greg928gts]

It makes sense, the equation seems to be for the center of the horn, not the top and bottom pieces, so an adjustment needs to be made. Either (1) Edgar made a mistake and did not notice this, (2) Edgar did notice and thought that it was not a big deal, or (3) the thread is wrong and the equation does account for the angle.

I thought it was mentioned that Edgar did notice this. Al's Trachorn is the same way, getting slightly narrower close to the throat. Since the top and ottom are a constant angle, close to the throat, the sides must come in more to maintain the tractrix expansion area.

That is what you are asking about, isn't it?

If the top and bottom were to have a flatter angle close to the throat, the sides wouldn't have to come in narrower at the one inch mark.

I hope I'm not just confusing the issue. I believe Gil had pointed out the reason, previously.

Bruce

Bruce, the issue of the sides of the horn ending up being slightly smaller than 2" wide at the begining of the throat is different than what tigerwoodkhorns is talking about. He's referring to my question about the difference between the curve of the side of the horn at the center plane, and the curve of the joint where the top piece of the horn meets the side piece.

The amount that the sides actually come in less than 2" is miniscule, but it is there in the calculation.

Greg