Please evaluate my Tritrix Tower design

[lunchmoney]

Using 7 liter sealed enclosures... a bit worried that they'll be too top-heavy... gonna create a chamber in the bottom and fill it with sand... if that's not enough I may have to create some kind of outrigger system...

Whaddya think?

[Hdale85]

Looks good to me

[Bill Schneider]

The curves you've created remind me of the work of a local sculptor, David Hostetler.

http://www.davidhostetler.com/



Maybe it's because his work is all over campus here that I see the resemblance.

I like the idea.

Bill Schneider

[ThomasW]

Should consider massing load the bottom or bolt them to a plinth.

[Hdale85]

Wouldn't that be what creating a box in the bottom and filling it with sand would be? :B

[lunchmoney]

Further development... with center channel and bases for the towers...

I decided that the towers were going to definitely be too top-heavy, even with a sand-filled chamber in the bottom, so I added a base to them... the extra slabs of 1" mdf in the base (shown in the 3rd picture in black) are simply to add weight... the upper most slab (shown wood-colored) is going to be doweled to the side walls of the tower for strength.... a big 'ol lag bolt through the middle of these slabs will fix the tower to the base.

The center channel is as large as it is in order to work well with the TV stand (the TV is going to sit directly on top of it)... the center channel has internal walls to create a sealed 7 liter enclosure, to match the towers...

Not sure what color I'm going to paint them yet... gotta consult with my better half on that one.

[---k---]

That isn't a further development. Further development would be cutting some wood.

[lunchmoney]

That isn't a further development. Further development would be cutting some wood.

lol... I'm gettin there... just gotta figure it all out first... it's how I roll

[ThomasW]

The plinth needs to be much larger too offset the mass at the top of the speaker. 3 little pieces of MDF aren't going to do anything toward mass loading the bottom

[lunchmoney]

The plinth needs to be much larger too offset the mass at the top of the speaker. 3 little pieces of MDF aren't going to do anything toward mass loading the bottom

hmmm... I was hoping that the plinth would be wide enough to make it stable... perhaps it isn't... no biggie to make it larger.

[ThomasW]

You might want to make up several size plinths then experiment regarding the smallest one that will prevent tipping. I think you'll be surprised at how big it actually needs to be to effectively stabilize the structure

[lunchmoney]

You might want to make up several size plinths then experiment regarding the smallest one that will prevent tipping. I think you'll be surprised at how big it actually needs to be to effectively stabilize the structure

Agreed... fortunately they're very easy to make and play around with.

My concern at the moment is whether or not I'm going to be happy with the MTM center... I've read that this format is less than ideal, but that the Tritrix is better for centers than most MTM's since the drivers are so close together...

The tritrix is the only center channel design I've found that is 8 ohms... my Yamaha HTR 5930 isn't rated for 4 ohms... I've heard that it might be ok at 4 ohms, but no one seems to know for certain... definitely don't want to do all this work and then blow my receiver.

[lunchmoney]

Please evaluate my Tritrix Tower design

It's a vented Tritrix with an internal volume of 22.3 liters... drivers, port, crossover, and foam lining volumes have not been subtracted from this volume... Dayton shielded 5.25" classics, Dayton silky tweeter... crossover not shown, yes it will be inside the enclosure (haven't decided where yet).

Depth and height of the enclosure have obviously been changed from Curt's original design, but the baffle width has not been changed... all walls are 3/4" mdf, except for the side walls which are 1"

The curved back walls will be an adventure in kerfing and bondo

They might be a bit top heavy... I'm prepared to make a wider base if need be.

Lining is PE 1/2" open cell foam... think that's thick enough?

Let me know if you have any concerns with this... bear in mind that I'm not after absolute perfection here, but if there's anything glaring please let me know.

Many thanks for your help with this...

[Hdale85]

I'd like to know how the heck your going to curve a piece of wood like that

[lunchmoney]

I'd like to know how the heck your going to curve a piece of wood like that

Kerfing and bondo... experimenting, patience, and probably a good deal of cursing... I'll get it... not too worried

[Hdale85]

Good luck! Looks great though.

[Mazeroth]

If you're going to go through all the effort to build these why not up the ante and build something with better SQ? Maybe cjd's RS MTM or, if you want to go bigger, the Natalie P or Modula?

[Jed]

I agree with Mazeroth. I recently heard some Modula designs at the Dayton DIY and they were very good sounding for the money.


I also don't understand why you would spend all that time on curving a part of the speaker you'll never see (the back).

Jed

[Deward Hastings]

You've got yourself a nice 150 Hz. organ pipe there, and the foam will absorb just about nothing at that frequency.

[---k---]

I believe that he is going for the Tritrix because it is 8 ohm and an easy load on his existing receiver.

Got a source for the 1" MDF? It will be harder than you think to find.

[John_E_Janowitz]

Just a quick comment. If you make the back piece the full width of the enclosure it will be much easier to build. In your drawing you have it between the sides. If you cut the sides first, then put the back over it, you'll have something to form the curve with. Easiest way to do that curve is to get 1/8" or 1/4" masonite. Bends very easily. Do one layer at a time and then laminate each layer until you get to the correct thickness.

John

[lunchmoney]

If you're going to go through all the effort to build these why not up the ante and build something with better SQ? Maybe cjd's RS MTM or, if you want to go bigger, the Natalie P or Modula?

1. Cost

2. Want something 8 ohm

[lunchmoney]

Just a quick comment. If you make the back piece the full width of the enclosure it will be much easier to build. In your drawing you have it between the sides. If you cut the sides first, then put the back over it, you'll have something to form the curve with. Easiest way to do that curve is to get 1/8" or 1/4" masonite. Bends very easily. Do one layer at a time and then laminate each layer until you get to the correct thickness.

John

That's a great idea! Thanks!

[lunchmoney]

I also don't understand why you would spend all that time on curving a part of the speaker you'll never see (the back).

Jed

For the love of the challenge... I'm a designer by profession, and I really get into this sort of thing... this will be in my portfolio with pictures from different angles.

...also, if the back were just a flat wall, and I was still planning on having the curved sides, I'd have to make the whole enclosure much deeper in order to maintain the volume.

[lunchmoney]

You've got yourself a nice 150 Hz. organ pipe there, and the foam will absorb just about nothing at that frequency.

Can you elaborate more please? Do you think this design has significant issues?

[Jed]

For the love of the challenge... I'm a designer by profession, and I really get into this sort of thing... this will be in my portfolio with pictures from different angles.

...also, if the back were just a flat wall, and I was still planning on having the curved sides, I'd have to make the whole enclosure much deeper in order to maintain the volume.

Maybe you could find a way to curve the front too.

[ThomasW]

1/2" foam won't absorb anything other than treble and a higher midrange frequencies.

Did you model the tuning of this box with a loudspeaker design program?

Aesthetics is one thing and loudspeaker design is usually something completely different.

There's a reason Curt's designs for this are deep as opposed to shallow.

[Deward Hastings]

Do you think this design has significant issues?

I think that if you don't stuff that pipe with absorbant it will honk like a wing of Canada Geese, with severe ripples every 150 Hz. all the way up to crossover. And that if you do stuff it enough to stop that you will lose much of the benefit of the port tuning. If you want to make it a transmission line you need to treat it as such from the beginning, understanding that that's a whole different design.

[lunchmoney]

There's a reason Curt's designs for this are deep as opposed to shallow.

Curt's 7 liter sealed version of the Tritrix is about this shallow... perhaps if I want a design this shallow I should go back to a sealed design?

[lunchmoney]

I think that if you don't stuff that pipe with absorbant it will honk like a wing of Canada Geese, with severe ripples every 150 Hz. all the way up to crossover. And that if you do stuff it enough to stop that you will lose much of the benefit of the port tuning. If you want to make it a transmission line you need to treat it as such from the beginning, understanding that that's a whole different design.

Is it because of the shallow depth that you see this problem? How deep do you think it needs to be?

[djg]

Suggestion

Make the top of your design the sealed version. You could still curve the back and maintain much the same shape and volume of the original box. Continue the back to the floor. It would be a little deeper than what you have now.

[lunchmoney]

Make the top of your design the sealed version. You could still curve the back and maintain much the same shape and volume of the original box. Continue the back to the floor. It would be a little deeper than what you have now.

Yeah, maybe I'm in over my head trying to make a ported one this shallow...

Oh well, easy enough to make it sealed... Curt's 7 liter version is about this shallow... is that too shallow? Should I base it on the 10 liter version instead?

[Deward Hastings]

Is it because of the shallow depth that you see this problem?

No, it is because it is long . . . a pipe . . . with a natural resonance related to the length. The reason we keep boxes box shaped is to keep all dimensions relatively small, and the standing wave resonances high enough to be easily damped (or not excited at all in the case of subwoofers) without interfering with the lower frequency mass/volume resonance of the port. Working around the resonances of a pipe makes for very difficult enclosure design. The only choices that are likely to work are highly damped sealed (almost IB) and transmission line (wihch will take careful attention to design, measurement and stuffing detail.

[lunchmoney]

No, it is because it is long . . . a pipe . . . with a natural resonance related to the length. The reason we keep boxes box shaped is to keep all dimensions relatively small, and the standing wave resonances high enough to be easily damped (or not excited at all in the case of subwoofers) without interfering with the lower frequency mass/volume resonance of the port. Working around the resonances of a pipe makes for very difficult enclosure design. The only choices that are likely to work are highly damped sealed (almost IB) and transmission line (wihch will take careful attention to design, measurement and stuffing detail.

Thanks Deward... I really appreciate your input... I think I'll just make it sealed...

If I make it similar in depth to Curt's 7-liter design, it wouldn't need to change much at all... do you think that's deep enough? or should I base it on the 10-liter design?

[---k---]

Did you model the tuning of this box with a loudspeaker design program?

I had that thought too. But, I wandered over and looked at the ported design Curt posted and it is a 22L vented. He claims his curved cab is also 22L. :shrug:

[---k---]

foam lining volumes have not been subtracted from this volume...

You don't subtract out this volume. The foam actually works to increase the volume seen by the drivers.

As others are pointing out, you'll want much thicker behind the drivers. On the sides won't be so important. Top and bottom could get important.

If he mounts the port up higher, and stuffs the whole bottom of the speaker with Acustic Stuff or Fibre Glass, would that work to get rid of the resonance?

[lunchmoney]

You don't subtract out this volume. The foam actually works to increase the volume seen by the drivers.

As others are pointing out, you'll want much thicker behind the drivers. On the sides won't be so important. Top and bottom could get important.

If he mounts the port up higher, and stuffs the whole bottom of the speaker with Acustic Stuff or Fibre Glass, would that work to get rid of the resonance?

Thanks...

Yeah, I wouldn't have any problem having the port be higher.

Would that work?

[lunchmoney]

Ok, how about this then?... 9 liters sealed... lining not shown.

Internal height and width is exactly the same as Curt's sealed designs... obviously I've gotten a bit creative with the depth... but according to Curt anything between 7 and 15 liters is acceptable... the 7 liter design is certainly shallower than this.

Think this will sound ok? Being used in conjunction with a sub...

[Deward Hastings]

If he mounts the port up higher, and stuffs the whole bottom of the speaker with Acustic Stuff or Fibre Glass, would that work to get rid of the resonance?

That's a good question. If there's enough fiberglass to take out the 150 Hz. resonance would the port "see" the stuffed volume, and how would it effect the tuning? I just don't know. The closest comparable that I can think of is the Linkwitz PLUTO, where he stuffs the pipe until it behaves like an IB (no port). In PLUTO the pipe resonance is quite bad without the stuffing . . .

[Deward Hastings]

Ok, how about this then?... 9 liters sealed... lining not shown.

. . .

Think this will sound ok? Being used in conjunction with a sub...

Don't "line", stuff. Pick you box size not by "looks" but to give a Q of .7 and an F3 at your desired crossover frequency, or reasonably close. Any box modeler will "do the numbers" for you . . . WinISP Pro or whatever.

Form follows function, and all that . . .

[lunchmoney]

Don't "line", stuff. Pick you box size not by "looks" but to give a Q of .7 and an F3 at your desired crossover frequency, or reasonably close. Any box modeler will "do the numbers" for you . . . WinISP Pro or whatever.

Form follows function, and all that . . .

Ok, supposedly the Q of a 10 liter box for this design is .707... so I guess I'll make it 10 liters.

Ok, stuffed it is... Curt recommends "100% fill" for the sealed enclosures... what exactly does this mean?

Thanks for your help!

[Deward Hastings]

Ok, supposedly the Q of a 10 liter box for this design is .707... so I guess I'll make it 10 liters.

Ok, stuffed it is... Curt recommends "100% fill" for the sealed enclosures... what exactly does this mean?

That will determine, then, what your crossover frequency to the sub should be, give or take, more or less.

""give or take, more or less" is what "100% fill" means, too. I had a Dahlquist DQ1W that had the box so full of foam and fiberglass and "stuff" that looked like the scrap box from a carpet store that when you unscrewed the driver it popped up three inches from the baffle from the pressure. I think most people mean somewhere between a half pound and a pound per cubic foot of fiberglass or poly batting, which will probably fill the box enough that you'll want a layer of foam behind the driver to keep it from migrating and touching the cone. You'll have to ask Curt what it means to him.

I like to see more by weight, but I use the higher density "rigid" rockwool, so even a couple pounds per cubic foot doesn't necessarily completely fill the box. I don't use foam at all, since fiberglass and rockwool are much more effective. And I don't "line" the box because air motion is greater, and thus the damping material more effective, away from the walls.

[Dennis H]

No, it is because it is long . . . a pipe . . . with a natural resonance related to the length.

No big. Lightly stuff the area behind the drivers and you will kill direct midrange reflections off the back wall and out through the drivers as well as top-bottom bass resonances. It's not like nobody ever built a good sounding tower before.

[Deward Hastings]

It's not like nobody ever built a good sounding tower before.

You do know the difference between the sound of an eight foot ceiling and the sound of an eight foot organ pipe . . . right? And why there's a difference?

[Dennis H]

Organ pipe schmorgan pipe. Read Zaph's blog for how to use stuffing in a ported tower enclosure to kill the vertical resonances. You're scaring poor lunchmoney over nothing. It's a non issue.