Presenting the Trynergy - a full range tractrix synergy.


Presenting the Trynergy - a full range tractrix synergy.

This speaker spun-off from the PRV 5MR450-NDY thread here:
and is sufficiently OT from the main thread which deals with the PRV driver and a FAST implementation that I think it deserves its own thread. The 1.0x scale tractrix horn design was calculated using Volvotreter's tractrix spreadsheet using a 2.78in square throat and a 175Hz flare frequency.

The spreadsheet as I used it to build my horns is on post 90 here

I then took the dimensions from every inch of axial distance and plotted the curve for the horn profile. I then fitted the curve with a two-point spline in Solidworks, then made a 3d model using the lofting tool, then I unrolled the curved shape to a flat 2d pattern using the sheet metal "flatten" tool. This pattern, once cut onto foam core (scored with parallel cuts every 3 to 5 mm on on the concave side) self-formed into the tractrix profile when enforcing the mechanical mates of the mouth, throat, and edge boundary conditions via hot melt glue to the top and bottom panels. For the 0.70x case, the throat is 2.0 in square and the mouth is 20 in wide and horn is 15.3 in deep. Glue the throat section first, then the mouth, then the middle.

Cut plan for 2d panel on post 94 here

Here is the cut/glue plan for the flat top and bottom panels on post 175:

The idea for this speaker came from a large 300Hz 28in wide x 17in tall x 22in deep tractrix horn driven by a full range driver. I then scaled that horn down to 0.70x for a 400Hz 20in wide x 12in tall x 15in deep tractrix. Originally designed with the Faital Pro 3FE25 in mid, I stuck a Vifa TC9FD in it for grins. With some DSP EQ'ing I was able to get the following response from the little Vifa:


With semi-decent polars:


And the Impulse response isn't too shabby either:


Here is a closeup of the horn driver throat flange fitted with the TC9FD (note that a FC spacer with a cutout had to be made to prevent the surround from rubbing the flange plate):


Here is the rear sealed chamber (6in x 6in x 4in and lined with open cell grey foam):


Here is the horn before I put the woofers on (note the black panels on top of the white panels - those are the constrained layer damping (CLD) layers used to reduce panel resonances using latex caulking in between the white horn walls and the black foam sheets):


I normally model stuff before building, but in this case, I had some buyout PE 6.5in woofers lying around. There is only so many ways to fit these drivers into the tractrix so I went for the build it as you go approach sans modeling and got this after 90 minutes of cutting foam core/cardboard and hot glue:


After building it, I then modeled it and saw that it needs a rear sealed chamber on the woofers otherwise there is no bass to speak of due to proximity of the backside of woofers and the mouth causing cancellation. Here is the predicted response with the woofers and the TC9FD:


With 3.5 mm xmax being reached at 21 volts:


Giving a corresponding max SPL capability of about 113dB at 1m and 21v:


With the corresponding electrical power input predicted to be 30 watts per 6.5 in driver, which is OK per the manufacturer's rating:


The $40 cost break down is as follows:

- Qnty 4 Parts Express buyout 6.5 in polycone woofers (same driver as used in ther well-regarded B652 speakers) $5 ea x 4 = $20

- Qnty 1 Vifa TC9FD driver $12

- 4 sheets of foam core $4

- 1 tube of latex caulking for the constrained layer damping $2 (n.b., DO NOT use Liquid Nails - as the solvent vapors will melt the foam in the foam core!)

- 1 dual banana post binding terminal $1 ( Edit: technically $3 now with qnty 3 binding posts)

- Hot melt glue sticks $1

Note that you will need active EQ and bi-amping to make this work. It is not a passive speaker. If you have a miniDSP 2x4 and a couple of amps you are set. If you need tips on how to do this, check out the "Cheap and FAST OB, Literally" thread.

I still need to install the rear sealed chamber and get a measurement with the woofers on.

Let's see if a point source synergy speaker can be built for $40 and if it sounds good. Stay tuned!

Measurements and sound clips to follow.

Update Sept 3, 2014: the tractrix fullrange Synergy is completed and it sounds wonderful! See post 13.



Edit Sept 4, 2014: New tweaks on EQ provide linear phase from 600Hz to 5kHz and cleaner impulse response. Note all data smoothed at 1/12th octave.



Edit: Sept 7, 2014 - Faital Pro 3FE22 driver with 4-way miniDSP XO and bass horn sub.

Edit: Sept 12, 2014 - How to adjust and optimize time alignment between HF and mid woofers -

Edit: Sept. 20, 2014 - Stereo pair completed, sound clips in post 269

Edit (Dec 14, 2015) - micro Trynergy with 13 X 8.5in mouth and 2in driver:

More info here


Edit (Dec 20, 2015): uTrynergy in a dipole bass enclosure - more info here Presenting the Trynergy - a full range tractrix synergy.


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Let me clean up the code a bit and then I will post it. High Qts drivers are not necessarily bad for horn loading. This is a myth from the days of high impedance amps of past. The low mechanical damping may pose issues with oacillations in freq response but that is more of a high Qms. For the woofer injection ports those really are not horn loaded but rather convenient entry points into horn mouth. For the fullrange driver I admit the Vifa is not the best choice and I am waiting for the Faital Pro 3FE25 or 3FE22 to arrive. Even there, the high Qts was not so bad to make it sound bad. In fact, I thought it rather nice sounding. Of course not as good as the $105 5MR450NDY but I can't complain for a $20 horn (before 6.5 in woofers).
Oke, I await it.

I have play some with the Xmax, and have in akabak the ports adjusted so that I have 120 dB 5mm Xmax (speaker is max 8 mm), the implemention of the reflex ports is very nice for this.

the FRS8M from visaton is also very good for you it is a small fullrange who go to 20 Khz.

I have change your script a little, like the power to them, high has now 1.5 and not 1.95.
chamber is smaller because it is little woofer, but handle 40 watts.

I get 120 +dB with 20 volts on it xmax 4mm that is small, wauw.

second photo are the phillips woofers in normal conic horn.




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That is some impressive bass you are getting out of the Phillips and it would appear seamless integration with the Visaton. 120dB+ is very good without hitting xmax.
You should build it based on how good the sim is coming out. My quad 6.5 in woofers can get lower bass but then the box volume has to be very big because they are rather large Vas drivers.
How big do you estimate it would need to be? Would it be feasible to make an enclosure for the whole unit, that doubles as the sealed rear chamber for the combined woofers?

That is normally what is done and this provides sufficient volume for a bass reflex. For a sealed system I only need 11 liters per two drivers. Or a 8x14x6 in box per side with two drivers. I am going sealed to get clean bass transients. If I made the total volume 2 cu ft for all four drivers with bass reflex ports I can reach 60Hz.
xrk971, congrats! This is your best FAST project so far, a real marvel!

Do you hear any resonances in the horn? 3mm plywood for tractrix side panels? Perhaps some PU insulation foam on the backside for damping and a cabinet for the whole thing - presto!

Thanks for the kind words! I had bad resonances with one layer of foam core. I was audible and measurable as harmonic distortion. I then used constrained layer damping


Here is before and after CLD on the bigger 1.0x scale horn:
First Sound!

The sealed rear chambers may just be a simple box, but it took almost as long to cut and assemble as the tractrix horn (lots of cuts whereas the horn was two panels and a top and bottom sheet)! I ended up reducing the volume down to about 9 liters for more bass punch at expense of extension. I checked in the model and a 9 liter rear chamber provides a 97dB at 2.83v and 1m sensitivity and about 103Hz as the -3dB point. The other reason for a smaller chamber was to keep the physical size smaller with the box being 8in x 14 in x 5in tall. I installed grey open cell foam on the inside, added a layer of cardboard on the large top panel to add stiffness as bracing is tough to put here with magnets in the way, I added one cross brace, binding posts, and wired in series on each side. This gives me option of externally wiring for series/parallel for 4 ohms or bi-amp each side at 8ohms (which allows me run the woofers like a DVC subwoofer in pseudo-mono).

Here is the inside of the rear sealed chamber:


Here is the speaker during the rear chamber mounting process. I used really long wood screws to go through the main horn flat panel to bite into triple-layer cardboard "nuts" glued into the box corners. This allows the box to be fairly clamped tight yet still removable.


Here is a view of the tractrix Synergy sitting on the stool-cum-speaker-stand fitted with a couple of foam blocks to stabilize it. The exposed parts give this speaker a bold chunky look that reminds me of a Transformer robot :) Kind of cool...


Here is a front view of the horn with the bass injection ports visible. The ports are hand cut using a template from the backside, but by the time the razor goes through 3 layers it looks a bit jagged. In any case, the CSA is eyeballed at about equivalent to a 2 in dia round port. Thus I used 5cm dia for the port in the model. In order to measure the volume of the driver chamber, you will never guess how I measured it! Well, since the surround is rubber, the cone and dustcap are polyethylene, all waterproof - I simply poured water into the cone like a bowl and poured the water out and measured the volume with a graduated cylinder :D It is exactly 185 mL :) No harm done...


Ok, so let's get to the good stuff... measurements. I used the EQ that I previously set for the TC9FD tractrix, but I removed the two rather agressive peak cuts for now. I set the woofer to flat (no EQ) and set the XO's per the simulation: -24dB/oct BW @ 300Hz LPF and 90Hz HPF for the woofers, and -24dB/oct BW @ 350Hz HPF for the TC9FD. I threw in a 0.5ms time delay on the TC9FD (to be tweaked later). Based on the simulation, I also set the TC9FD gain at -6dB to match the lower sensitivity of the four woofers (which is predicted to be 97dB at 2.83v), making the predicted TC9FD sensitivity about 103dB at 2.83v before the cut.

Here is the combined and individual responses of the TC9FD and the four woofers in the tractrix Synergy. As you can see, the XO frequencies worked out perfectly. Akabak is a great help for initial XO setups. There is a well-known room mode dip at 80Hz and 150Hz in my speakerlab. You can see those here, but otherwise, the woofer behaves just as predicted.


Here is the harmonic distortion (HD) of the system - below 100Hz, the drivers are exciting panel resonances that are below the bandwidth of the constrained layer damping (CLD) that was used which was very effective for sub 1kHz vibrations. This just means that if one wants to make a clean sounding Synergy for sub 100Hz, it probably needs to be made of something heavier like wood. :) My goal was to use this down to 100Hz where it will be crossed-over to a bass horn sub, so it has satisfied that goal very well. Above 100Hz, the HD levels are very low - characteristic of a TC9FD, which is already low, and when combined with horn loading for very small excursions, the HD is even lower. This results in a super clean purity of tone. Despite what some may say if harmonic distortion is perceptible or meaningful, in this case, the ultralow HD *IS* perceptible when listening to music. Especially vocals or complex passages with many instruments. The notes are distinct and "clear as bell".


The EQ could be cleaned up a bit more to smooth things out, but as is, it gives a pretty decent impulse response as seen here:


I also tested out what the woofers could do if I set the XO highpass at 70Hz for a little more extension:


Now finally, for the subjective question of how does it sound? Well, drum rol........... In a word, MAGICAL! There is something very special about a single point source covering a 100Hz to 18kHz coming from a tractrix horn that reduces the room wall reflections due to directivity. There is less junk bouncing around the room to mess with your perception, and the sound is *CLEAR* and clean. I have heard this description of the Synergy before: like listening to a big headphone without headphones, but this is in a good way. I can imagine that with two of these in stereo, the imaging and soundstage will be unbelievable. So for only $40, a little sweat, lots of modeling and designing, I am now a Synergy convert and can say without a doubt, this is perhaps the best sounding speaker I have ever built or listened to. Superlatives like best are difficult to use, as there generally will always be something better somewhere. So to caveat this, it will probably lose out to its bigger brother, the 1.0x scale tractrix with the 5MR450NDY, if that were ever "Synergized" with the dual 12in Kappalites for bass drivers.

I haven't had time to do extensive listening, maybe 4 test tracks so far. But each one just blows me away - it's like watching HD TV for the first time. Here is the first sound clip I recorded. One of my favorites to check vocals and articulation. Hope you like it...


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That is some impressive bass you are getting out of the Phillips and it would appear seamless integration with the Visaton. 120dB+ is very good without hitting xmax.
You should build it based on how good the sim is coming out. My quad 6.5 in woofers can get lower bass but then the box volume has to be very big because they are rather large Vas drivers.

How How, the bass is include tapped horn you did als include.

this is without that horn, my tapped horn I have fold and drawn go to 70 Hz, so it fit well here just for the overlap to bass mid, however efficienty of the tapped horn is not extreme in comparison of your tractrix, and i need analog so I go use a amp for the tapped horn and a stereo amp for tractrix or in my case conic first..

ML-TL picture go to 16 Hz


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