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Speaker build tips, Tri Trix TL

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Forum topic by OldBull posted 08-21-2021 03:11 PM 421 views 0 times favorited 12 replies Add to Favorites Watch
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OldBull

516 posts in 544 days


08-21-2021 03:11 PM

Good Morning,

I am diving into another project, Tri Trix TL components only speaker build. https://www.parts-express.com/TriTrix-MTM-TL-Speaker-Components-And-Cabinet-Kit-Pair-300-702

I did not purchase the cabinets in this kit just the drivers (speakers) and hardware. I have the companies cabinet and crossover PDF’s they supply.

Anyone who has built these, I would appreciate any tips. I found an old thread from a member named Blake and messaged him but if you have built these, any tips would be appreciated. The build will be with 3/4 MDF and not sure of the finish as veneer would double the cost.

Donny


12 replies so far

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knotscott

8431 posts in 4624 days


#1 posted 08-21-2021 06:05 PM

Hi Donny – I haven’t built the Tri-Trix (or any kits), but have built many original designs, including a transmission line (TL) design (my favorite). The TL has numerous benefits, but is more difficult to build, and requires more subjective tuning via trial and error to perfect.

Since you have the cabinet PDFs, and it’s a fully developed model, I would suggest following their plans as closely as you can….at least for the t-line component. Altering the dimensions much will likely alter the intended bass results. Keep the driver centers as close together as you can….some people even truncate edges of the some of the drivers for closer proximity.

One tip I can offer is to splurge for wool fiber or Acousti-Stuff fiber fill if you’re fussy about sound. Both have superior sound absorption to typical polyester fiberfill, but likely costs more. If that’s not doable, pre-compressed poly fill, such as from an old pillow works better also. At the very least, I would put the fill into something like an old stocking to keep it somewhat compressed, then fill the t-line with that. The amount and density of the fill will likely need some adjustment within the t-line to get results in your room, but that’s one of the benefits of DIY.

Another option is to spray the inside of the t-line with something like an automotive rubberized undercoating to help reduce panel resonance. Easy to do in a DIY project, and there’s really no downside other than a small cost and a bit of time.

My cabinets were MDF that’s been painted with an automotive finish (including body fill and primer), then the outside panels were added after, using flexible rubberized adhesive. Those outside panels (hand painted to look like wood) with the rubberized adhesive makes for a desirable sandwiched panel that’s remarkably inert and has very low vibration.

Use at least a decent grade of oxygen free copper wire for internal wiring….12-14 awg is good, even 16 is ok. Inductors have a magnetic field, so if there are more than per crossover, place them as far apart as possible on the x-over board. Rounding the front cabinet edges helps reduce reflections. If you build a grill for them, you can bevel the inside edges to also help reduce reflections. If you feel ambitious and are fussy about sound, one other option is to install separate binding post inputs for the low and high frequency drivers…one of the tweeter, one of the woofers. This separates the tweeter and woofer crossover inputs at the terminals instead of inside the cabinet. which will allow for bi-amping or bi-wiring at some point in the future. (bridge them together with external connections until that time). It’s just another small tweak that some will deny any benefit from, but others hear it, and again, there’s really no down side other than the small cost of more binding posts and wire. Tweaks like these are very system, setup, and user dependent, but they’re just a few of the small things that can add up to an audible gain on a good system.

Good luck, and keep us posted on your progress.


-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

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tvrgeek

2292 posts in 2898 days


#2 posted 08-21-2021 09:28 PM

Built many a speaker. Actually that was what got me started in woodworking. I do my own designs, but that one is reasonably respected.

Read up on Olson and diffraction. It makes a huge difference in top end edginess. ( sorry for the pun, but that is the way it is)

Personally, what kind of damping material does not make much difference. Its placement and density does.
Please use flairs on both ends of the port.
Tune by measurement, not by drawings
The only reason to use poly caps is they don’t degrade like electrolytics. You have to move way up the line in driver quality before the difference is audible. Same with any BS about fancy wire, silver solder and other such nonsense. Yes Virginia, zip cord is almost perfect as a speaker wire.
I do not know if the crossover is a correct D’Appolito alignment or not. If it is, speaker placement and depth as well as the exact crossover values are critical. If done correctly, a very good design.
The Dayton drivers are great value. To step up is at least double the price. Used well, they can beat a lot of expensive parts not used as well.

Unfortunately, a great many “experts” build beautiful cabinets, but do not understand the physics, so they fall victim to the advertising hype and logical but wrong magic parts. The amount of flat out well meaning but totally wrong advice out there is overwhelming. I am an engineer. Built speakers off and on for 45 years. Think about it. What is two feet of hookup wire going to do compared to some fancy oxygen free garbage when you are running ointo drivers with hundreds of feet of standard copper, aluminum foil in caps and more hundreds of feet in the inductors. Ever looked at an amplifier output stage? ( Yea I built high end amps too) Just one more bit of fake magic that the magazine writers invented as they had nothing better to say. Ever see a studio board? You might be amazed to find out your CDs went through several hundred 5558 Op amps.

Where you need to spend your money is in the room. Imaging is a function of near reflections. If you can damp above 2K within two feet, you will be amazed. First time a sound comes from not only outside the speakers, but outside the room, you will jump! Owens Corning 407 is your friend.

There are much better forums for speaker building advice. diyAudio is one. But be careful, as I suggested well meaning but wrong advice. Parts Express sponsors their own Tech forum and I am sure you can find many builders there.

Anyway one can write a book on this. I did. It barely scratched the surface as the physics involved are actually very complex. Made very confusing by psycho acoustics and how your brain mas the environment and makes expectations of what should be natural. Hint: Flat is not it! Ever!

Best of luck. The good thing is unless you really screw up, there is a documented principal that the more effort you put into them, the better they sound to you. Maybe not to me, but to you is what matters, so go for it!

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OldBull

516 posts in 544 days


#3 posted 08-21-2021 10:35 PM

Thank you both very much for the advice. TVR they have a poly fill that is included. Yes, lots of talk. What makes that so bad is that the actual info is so deep and spread out that even getting an available driver through the cabinet and crossover calculators can be tough. I have been working toward this for many many months and finally tried to just get an in-stock moderatley priced mid-range driver figured out and had a hard time doing that.

I know the tweeters have a sealed case so no cabinet space needed and it does not interfere with the other speakers. The 2 woofers are 4 ohm in series and they are of course vented as a transmission line. Learning to understand just that much by yourself is complicated.

The problem now is the drawings are so incomplete, I will post some pics of this example and the actual production cabinet. They have a slot for the transmision line divider in the side and a knotch on the ends of the divider. Is this necessary ? Should I fill the corner deflectors? I want to build but as you say the specs are not to be toyed with without the ability to tune. In the last picture there are 2 small crossmembers in the middle of the cabinet he did not glue, do you think this was a mistake ?

””Please use flairs on both ends of the port””. Do you mean to roundover the ends so that are not straight edges? Also, thanks, I found the PDF, Direct Radiator Loudspeaker Enclosures by Harry F. Olson.

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knotscott

8431 posts in 4624 days


#4 posted 08-22-2021 12:16 PM

There should be no need to fill those corners. They just become empty chambers to avoid having 90 degree corners in the t-line, and keep the area of the tapered line uniform. You could fill them with sand to add some mass, but they really aren’t likely to contribute any sound.

Both ends of both braces should be fastened somehow, whether with glue, screws or both. The braces are less critical to the actual transmission line function, but should help reduce cabinet resonance, so are beneficial over all.

I’m not sure I understand the question about the notch on the end of the slot for the t-line divider…..if you mean the rounded end of the slot, that’s likely just the result caused from using a router bit to cut the slot. It should pose no issues.

This cabinet design uses a transmission line, so there are no traditional ports involved.

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

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OldBull

516 posts in 544 days


#5 posted 08-22-2021 04:47 PM

”“I’m not sure I understand the question about the notch on the end of the slot for the t-line divider””

When using glue and MDF is the slot even neccessary ? After looking closer the slot is wide enough for the entire 3/4” board (divider), they just cut a notch in the ends of the divider so it can sit flush (see pic 2), the divider is longer than the slot. . Can I do away with the slot and just glue the board directly to the surface, what is the purpose of the slot, for correct angle ? Especially since most woodworkers can correctly achieve 78 degrees.

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View tvrgeek's profile

tvrgeek

2292 posts in 2898 days


#6 posted 08-22-2021 05:23 PM

Decent midrange for a fair price? Ha, ha, ha, ha…..

Actually the RS 100 if tamed ( steep crossovers) will do OK, but midranges are for some reason really hard and really expensive. Tried several of the “full range” like Mark Audio. Measured fine, but not happy with the sound. I have done far better with 5 or 6 inch 2-ways. Multi-mid-base, as you are building, gives you some advantages in the distortion, but adds complexity in lobeing. I see the tweeter is offset, so it is an MTM, not a D’Apolitto alignment. Bummer. That was pure genius if the drivers were tame enough.

Most DIY speakers are way over-built. PVA glue is stronger than the MDF so no fancy fastening is needed. Just whatever holds it in place. I favor a pin nailer. I have seen speakers with more screws in them that Evil Knievel’s legs.

Personally, I am not a fan of TL alignments. If well done, they can work fine, but I can do better overall with ported. TL’ were a safe go-to before we understood the physics better. I prefer low Q sealed for subs as port noise becomes a problem. Spent months trying to get 6th order alignments to work with the available drivers to no avail. They offer a substantial advantage in distortion if you can get them to work.

I have my go-to suite of design and measurement tools, mostly open source, as well as calibrated mic, preamp, old Pulser, scope, generators, meters and everything. You can’t use the impedance or frequency plots the OEM provides for design. They are only good enough for selection and then you can still get surprised.

I favor LR-4 acoustic alignments for the simple reason of taming the top of the mid and the distortion of the tweeter. Usually, they are a 3rd electrical, but that sometimes pushes the drivers out of their happy land so I have built 4th order electricals. If I could find or afford better drivers, I would use less aggressive crossovers.

FWIW, my living room set was loosely based on the SR-71 design but a lot of additional effort to smooth out the top end. I have always thought of an upgrade as the new SB and Santori divers look very good and several net tweeters. Transducer Labs I would love to try. But, they play loud enough to damage your hearing without distortion that bothers my wife ( very sensitive) so I have moved on to other hobbies. My HT is RS 150’s with Seas tweeters. Fountek on my desk. Got rid of all the rest. I think I have a pair of HDS tweeters still on the shelf if anyone is interested. I need to get busy and advertise my boxes of resistors, caps, coils and stuff. PE or DIY I guess.

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knotscott

8431 posts in 4624 days


#7 posted 08-22-2021 06:35 PM

I don’t think that slot is absolutely necessary, but it should add some strength, and can help assure proper angle. The PDF plans will likely take the slot into account when it calls out the width of the divider. If you forego the slot, be sure compensate the divider width accordinly.

The infamous “notch” might be to allow the last few inches of the divider to land beyond the slot, though I’m far from 100% certain about the what or why of it. Maybe for fine tuning of the t-line tunnel area?

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

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Foghorn

1301 posts in 635 days


#8 posted 08-22-2021 10:13 PM

I don’t know much about speakers but appreciate learning from those who do. I find it interesting that the dimensions from Olsen are similar to my Totems except that mine are wall mount and only 3.5” deep. The sound is spectacular though. I have a Pioneer SC-79 driving them along with a sub for both TV and stereo. Pretty easy to cause hearing damage if you’re not careful. Do any of you have comments on the specs and whether I could build better for cheaper with limited knowledge?(pretty sure the answer is yes). Here’s a link and made in Canada! https://totemacoustic.com/product/tribe-iii/

-- Darrel

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OldBull

516 posts in 544 days


#9 posted 08-22-2021 10:33 PM

Thanks for all the help guys, Foghorn it is obvious one of the others will have to answer your question as I am really new to speaker builds, however there are kits that walk you through the process, see https://www.parts-express.com/

The question about a slot or no slot would be any accoustical value from the slot which would lead to the question is glue-on-MDF just as good as solid MDF ? I would guess the slots are for the ease of the build but the slots corners inside the cabinet for the divider and the the braces might be better off just glue to MDF. I might just build it that way but have no way of comparing. I also see that the corners for the T-line are notched as well for the other half of the cabinet. Could it be they are afraid of gaps and thus use the slots ????

Wish me luck and thanks again for the help !!!!!

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knotscott

8431 posts in 4624 days


#10 posted 08-23-2021 10:39 AM



I don’t know much about speakers but appreciate learning from those who do. I find it interesting that the dimensions from Olsen are similar to my Totems except that mine are wall mount and only 3.5” deep. The sound is spectacular though. I have a Pioneer SC-79 driving them along with a sub for both TV and stereo. Pretty easy to cause hearing damage if you’re not careful. Do any of you have comments on the specs and whether I could build better for cheaper with limited knowledge?(pretty sure the answer is yes). Here’s a link and made in Canada! https://totemacoustic.com/product/tribe-iii/

- Foghorn

Given that the Totem drivers are proprietary and custom built, you’ll have a tough time duplicating them, which also will likely mean that you’ll need to alter the crossover design to match whatever drivers you end up using. Doable for less money for sure, but duplicating their sound will be a challenge. That doesn’t mean you shouldn’t try….if you’re committed, and see it through until you have something you love the sound of, you’ll learn a ton and end up with something you’re proud of.

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

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OldBull

516 posts in 544 days


#11 posted 08-23-2021 12:49 PM

Knotscott what do you change to tune a transmission line speaker ?

Anyone offering their suggestion for a clean $250ish amp with digital inputs ?

What would happen if the corners were double thick but rounded on the inside ?? I am starting to get stupid here and may ruin the sound if I am not careful !!

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knotscott

8431 posts in 4624 days


#12 posted 08-23-2021 01:35 PM

You can change the density and distribution of the stuffing in the line….a little more, a little less, compact it a bit, etc. For most DIYers its just done by ear to suit your preference, and room response. You can also line the inside of the T-Line with some foam, then add the stuffing too, but the stuffing is what really impacts how the T-Line works, because its slowing down the speed of sound in air through that fill. Note that it’ll take a few hours of playing time for the woofer suspension/surround to loosen up and reach their intended specs, so I’d hold off on any fine tuning until they’ve loosened up some.

Rounded corners on the inside should be no issue. If you double the corner panels, theoretically it can alter the area just a tad, but I doubt it’ll make much difference.

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

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