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Daddy Dee

What makes some tractrix horns suitable for HF?

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There have been a number od DIY tractrix horns built and posted on the forum. Some of these are most impressive drop in replacements for K400 horns in KHorns and even LaScalas.

It seems, to my observation at least, that all of these tractrix horns are used in three way configurations.

The K 402 and other (little guy can't remember the number) 510? Maybe? which are used for the Jubilee are used with a single HF driver which covers the mid and tweeter ranges.

Are any of the DIY tractrix horns suitable for this type Jubilee or JubScala duty? My impression is that they will not load the higher frequencies properly.

What is needed in a tractrix to make it work for wider frequency duty?

What keeps the diy tractrix from working for the higher frequencies?

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I see the biggest limitation of the DIY tractrix horns being the mating of the driver to the horn....or basically, the inability to design your own phase plug and the difficulty of trying to maintain a smooth tractrix expansion through the throat. The tolerances become a bigger issue as you move higher in frequency too.

Also, the K402 and K510 were designed with EQ in mind and many of the DIY'ers aren't too interested in tackling that challenge. I think the amount of EQ can be deceiving at times because the K402, for example, is still a 108dB speaker at the top end of its response...which is better than a lot of dedicated tweeters actually.

Btw, it's my understanding that the tractrix horn really has no limits to HF extension, but rather the driver is going to be the limiting factor.

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Daddy Dee,

I have read your post to this forum over the years and know that you are very knowledgeble when it comes to the Heritage line of Klipsch speakers as well as other audio related issues so I will as others on this forum would admit that you know and have experience in what you talk about and add to this forum.

In saying all this and not having any sound experience with two way jubilee or jubscala at all, I must speak up for the 2 inch throat tractrix horn from Greg Roberts that I just had in my home for the last two weeks.It is setup for a three way design of course but listening for the last two weeks with this setup of Gregs horn,BMS 4592 mid driver, and the Beyma tweeter with khorn bass bins was just a very eye opening experience.

Two way or three way,what does it matter. We all are after the best audio sound performance we can get for the time and money we have available to put into this hobbie and I will tell you from experience, this tophat of Gregs horn as well as the BMS driver will rock any house.

If this can be added to a jubilee or jubscala which I am sure it can with crossover mods and even if you have to add a tweeter in the mix, I will bet money it will sound wonderful with any kind of music. The tech part of this would be above my head but I would stand in line to hear it.

Just my thoughts and or sound opinion,

Randy

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From the pictures on the forum, it looks like the K402 is a tractrix mouth coupled to a conical throat.

Bill Woods, horn designer forYorkville sound, built this tractrix horn in 1975:

page10-1005-full.jpg

Some remarks of his:

I’m often asked how horns differ from one another, and also how different types of horns differ in sound and design, such as exponential, tractrix, and new versions of these which carry the names of their designers. I’ve put together some observations, backed up by actual frequency response curves and measurements, so that people can decide for themselves what types of horns would work best for them.

For the past 30 years I have designed loud speakers for professional applications and more recently for home HiFi. While designing at Yorkville Sound and in the course of my career, have built and tested numerous exponential and tractrix horns. This includes hybrid profiles using a tractrix and a conical which were created to fulfill specific tasks. In professional audio, horns have to work as intended. They cannot be of unlimited size - in fact, there exists an obvious commercial advantage to building the smallest horn to do a given job well. Tractrix or exponential horns are rarely used in professional applications where clarity and coverage are an issue.

The tractrix profile has been used in commercial products and in DIY. All exponential, and tractrix horns tend to beam as they go higher in frequency due to the squeezing of the side wall of the horn. This results in a "honky" sound and some of the high frequency information is lost, when listening off axis. This is the case no mater what type of mouth correction you might use. The tractrix profile itself is a form of mouth correction.

I can, however, suggest a simple way to make some experiments for yourself, to see how horns differ from each other in a very rudimentary way. Choose a compression driver, and make a number of very short horns of only 4-5 inches in length ---really horn adapters-- for your driver.

The most critical part of a horn is the first few inches. This is often over looked. Start with a section of straight pipe. Listen to that. It will be very loud, and very colored. Next, try an exponential horn of the same length, then a tractrix - they will be progressively less colored. Finally, try the conical section. It will be the most natural sounding and uncolored.

------------------------------------------------------------------------------------------------------------------------------

For those wanting to try a good, inexpensive conical horn, suitable for a two-way (Jubilee, Cornwall, or dual 12s like the CF4, KLF30), look at this $58 horn:

http://www.loudspeakersplus.com/images/XT1464.pdf

The 1/4W cut-off point of this horn is 340hz, and is said to be useable above 500hz. For prosound use an 800hz crossover point is recommended for pattern control and power handling. I would imagine it would sound fine at 650hz/24dB for home use.

Note: Don't be alarmed by the 60° pattern on this horn. Horns of this type sound so smooth off-axis that the 60° seems to be fine for home use. I am buying a pair for some Beyma CP-755, only $179.50 (no VAT for export).

http://profesional.beyma.com/ingles/pdf/CP755Ti.pdf



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Yup The 402 is a poor excuse of a tracktrix,,Mostly conical 80% with modified tracktrix mouth.. The designer of that horn should be horse whipped,,salt rubbed in his wounds,,and left in the hot sun..

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I wonder ... did that horn make the VW go slower (because of drag) or faster (because of thrust)?

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The most critical part of a horn is the first few inches. This is often over looked. Start with a section of straight pipe. Listen to that. It will be very loud, and very colored. Next, try an exponential horn of the same length, then a tractrix - they will be progressively less colored. Finally, try the conical section. It will be the most natural sounding and uncolored.

I'm not sure I totally agree with the test....are you holding the flare rates constant, or setting a fixed mouth area?

Btw, where you getting the CP-755ti for $180? It's $350 here:
http://www.usspeaker.com/beyma%20CP755Ti-1.htm

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The K510 horn is a tractrix type, AFAIK, and sounds much better than the exponential K400 plus K-77. Of course, its design is 40 years newer and the K-69A driver is much more modern than the K-55V I was using previously. The 2" throat of the 510 may also help.

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Edgar, those guys in that Bug with the horn on top were really "smokin" down the road. If you know what I mean.[;)]

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The Bug has a bigger horn, but the MX5 has stereo! How many car audio speakers help your car do a wheelie?

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I'm not sure I totally agree with the test....are you holding the flare rates constant, or setting a fixed mouth area?

I'm not sure I agree with the blanket statement either. I'm using 8" coaxial drivers loaded in .9 cabinets tuned to 70Hz. The compression driver is mounted directly to the woofer center pole which has a 1" exponential horn machined into it. The woofer acts as part of the horn in the form of a 90 degree conical waveguide. These cabinets are producing some of the most naturally clear uncolored sound I've ever heard in my room (and a half dozen people who've heard all of my systems agree). So, the actual horn is exponential in type -- and we've been programmed to believe that this type is to be avoided. This present experience leads me to believe that what horn type you use (within reason -- some horns just sound bad) isn't the greatest determining factor in how good the resulting sound is.

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No.

I don't want to say much about them here because it would be inappropriate. After hearing them -- my wife, oldest daughter and two sons are trying to convince me to market and sell them. I'm bringing them to AKfest next weekend -- feedback from listeners over the weekend will determine whether I move forward or not. I also have plans to take them over to Michaels place in the near future -- you are welcome to swing by -- but not without your instruments. :)

You have a PM

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ex-VAT is GB122=USD180

http://www.bluearan.co.uk/index.php?id=BMACP755TI&browsemode=category

"I'm not sure I totally agree with the test....are you holding the flare rates constant, or setting a fixed mouth area? "

Doesn't matter.

The point is to listen to different throat expansions using small horns of different types. You cut them off high enough to avoid the natural cut-off point of the horns, so you are just evaluating the throat transition. Some throat transitions measure good, but sound poor (just goes to show we don't know what to measure).

"The most critical part of a horn is the first few inches."

This was my quote of Bill Woods, but I totally agree with it. At one time PWK made a similar statement, almost the same exact wording.

Bill Wood's site:

http://www.acoustichorn.com/

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Wow. $180 each for a compression driver to cover 6 to 800hz and up?

That sounds like a very good candidate for a Jubscala or Jub HF. I'd love to hear if it's up to the task.

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So you saying Bill Wood's horns will sound better than the K402? Or what about the 18 Sound horn?


Do the comparisons need to be done with axisymmetric horns? I've
heard plenty of rectangular conical horns and they've always sounded
real squonky. I agree about the first few inches too, but you also
gotta match the wavefront of the driver/phase plug to the walls of the
horn....so if you change the driver, I wouldn't be surprised if you
could change which horn sounded best (within limits of course).


Btw,
I just wanted to mention that the K402 is a modified tractrix
horn....nobody really knows what that means since nobody has really
measured the area expansion of the horn (that I know of).


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"Btw, I just wanted to mention that the K402 is a modified tractrix horn....nobody really knows what that means since nobody has really measured the area expansion of the horn (that I know of). "

From what I can see from the photos on the forum, i see a conical throat with a tractrix mouth. The clue is the lack of curvature that can be seen in the sidewalls in the throat area.

You are correct about axisymetrical horns sounding better, that's why the 18 Sound, Faital Pro, and others are elliptical. Newer drivers are eliminating the long stub inside the drivers, these were typically exponential in expansion and could really dominate the sound of the horns.

18 Sound has small conical horns starting at $27.

http://www.loudspeakersplus.com/html/18sound_horns.html

Faital Pro has small tractrix horns starting at $50.

http://www.usspeaker.com/homepage.htm

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I see the biggest limitation of the DIY tractrix horns being the mating of the driver to the horn....or basically, the inability to design your own phase plug and the difficulty of trying to maintain a smooth tractrix expansion through the throat. The tolerances become a bigger issue as you move higher in frequency too.

Also, the K402 and K510 were designed with EQ in mind and many of the DIY'ers aren't too interested in tackling that challenge. I think the amount of EQ can be deceiving at times because the K402, for example, is still a 108dB speaker at the top end of its response...which is better than a lot of dedicated tweeters actually.

Btw, it's my understanding that the tractrix horn really has no limits to HF extension, but rather the driver is going to be the limiting factor.

So are you saying the 510 is better... say with the same driver ?

How about the Beyma 755 driver on either the 402 or 510...

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Time for me to add my 2cents. The conventional tractrix horn is not a CD horn. That is, the frequency response off-axis will not be similar to the on-axis response. The horns that are mentioned by DJK are CD horns. The modified tractrix horn from Klipsch (K-510 and K-402) are also CD horns (they look to have a healthy dose of a conical expansion in them - the details are not public). This distinction is important (conventional vs modified tractrix). The DIY tractrix horns that are being discussed in various threads are not (or probably not) CD horns. The reason why CD is advantageous is best left for a separate discussion

There are others also, Altec's Manta Ray, JBL's Bi-radial, Electro voice, etc. Of course not all CD horns will necessarily sound good. In my very limited experience, the horns that force a great deal of air through a narrow diffraction slot (sometimes necessary to make it CD) can sound pretty rough (especially if they are driven hard and the crossover frequency is low. The JBL bi-radials can be like this.

So let me make a recommendation for a DIY horn that can be used in a two way configuration and please remember the size of the mouth needs to get larger as the crossover frequency is lowered. My suggestion is to look at the links listed below. These are the "quadratic throat" horns from Charles Hughes (Peavey). Their expansion is mostly conical and the important geometric issues are at or near the throat (just like DJK has pointed out elsewhere). There appears to be sufficient detail to build these. The specifics about the throat transition (and its construction) are best gleaned from the patent (2nd link). BTW, this horn design shares much with the Geddes "oblate spheroid wave guide" (which is also a CD horn) but his will not be as simple to construct (especially if the horn is not axisymmetric). The links also provide some measured data (I could not get the links to set up correctly - please cut & paste)

http://aa.peavey.com/downloads/pdf/qwp1.pdf

http://www.patentstorm.us/patents/6059069.html

http://www.excelsior-audio.com/Publications/QTWaveguide/Hughes%20-%20A%20Generalized%20Horn%20Design%20to%20Optimize%20Directivity%20Control%20&%20Wavefront%20Curvature%20(AES107,%201999-09).pdf

Good Luck,

-Tom

If you are not an adventurous DIYer and would like a CD horn that will go fairly low in frequency (and can sound pretty good), there is an Electrovoice HP 640 horn for $30 on eBay. The shipping could be expensive. There are various options on the choice of drivers. However, it was used with the EV DH1A (which can be affordable).

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There are others also, Altec's Manta Ray, JBL's Bi-radial, Electro voice, etc. Of course not all CD horns will necessarily sound good. In my very limited experience, the horns that force a great deal of air through a narrow diffraction slot (sometimes necessary to make it CD) can sound pretty rough (especially if they are driven hard and the crossover frequency is low. The JBL bi-radials can be like this.

I just want to mention in passing that this is often true, but should not be taken as a general guideline. For example, the long-discontinued EV HR9040 CD horn uses a narrow diffraction slot, yet is regarded in "ultra-fi" circles as an exceptionally good sounding horn. As always, YMMV

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