TL Sub using Dayton 6.5

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I measure to the mid-point of the surround. In your case this would be 5.375 inches for the diameter.

Sd = 3.14159 x (5.375 / 2)^2

The important parameter is the front cone area since it is used to calculate the SPL for 1 m / 1 w in the worksheet calculations. Keep it simple, don't make things too complicated. The transmission line cross-sectional area is typically expressed as a multiple of this front cone area.
 
Sd = what parts of driver

So... the little hemisphere that covers the voice coil is included in the driver Sd. I guess if it moves, add it in.

I see the beauty of including half the surround as that approximates the part the moves and the part that doesn't.

I'll make some recalculations and changes to the plan this weekend, when I get my PC back from the fixit (XP2100 burnt up! No reason, not clocked).

:)ensen.
 
Solen vs Parts Express vs ?

I saw a post on another thread re: Solen and checked out their website. Not very well organized so some searching to find a driver that could be used instead of Dayton. I chose the Dayton because of the Fs and low price was the bonus. A competing unit will have to be reasonably priced with similar Fs.

Any other suppliers in Canada or USA that I should check? Does anyone know if that Speaker City in Vancouver sells drivers off-the-shelf?

:)ensen.
 
Okay, everyone,

Here is the latest design based on MJK Alignment Sheets. I haven't started on a design using dual driver yet since I intend to use a left and right pair and already have a pair of drivers. I've shown driver Sd comparisons which put the pair of 6.5" drivers at greater area than 8" driver so more air moving with the same amount of excursion.

I've also shown the physical dimensions of the proposed TL.

My next step is to to figure out how to make it shorter in stature so it can also be used as a stand for the mains. I'm thinking at most 32" - 36" tall so it's going to have to grown deeper somehow.

:)ensen.

Two 6.5" drivers:

A = 2 driver * pi * (5.375 / 2) ^2
= 45.38 sq.in.

vs. 8" driver

A = pi * (6.875 / 2 ) ^ 2
= 37.12 sq.in.

vs. 10" driver

A = pi * (8.875 / 2 ) ^ 2
= 61.96 sq.in.

All figures based on driver cone smaller than driver overall size by constant sized metal frame. In reality, frame also gets bigger so larger drivers have even smaller cone areas.

Box OD = 11" x 17" x 44.5" (WxDxH)
Line width = 9"
Taper from 15" to 3"
L = 67.8" measured by CAD
So= 135 sq.in.
Sl = 27 sq.in.
 

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Oops!

Poo! I was just looking at the calculations again and the TL dimensions are based on Sd = Driver size area - voice coil area. The new driver size is about 5.375 based on the surround and including the voice coil. So now I have to re-work including the enclosure.

:)ensen


PS: Dave, the modeler is Rhinoceros 3D from McNeel software. I'm also using the Flamingo 3D plugin for photo-realistic rendering and the Penguin 3D plugin for non-photorealistic rendering, which is what the posted pic is done with.

www.rhino3d.com

Rhino is a great modeler. It isn't cheap, but it isn't expensive compared to the typical softs. It has the best GUI I've ever seen in a drawing program. So good that I find myself trying to use the zoom and pan functions in other programs like Corel, Photoshop, Word, Excel... And it is easy to learn. I never used a modeler before Rhino, but with it, I was modeling inside of a day. And proficiency for about 90% of work was had in about 3 weeks. And... the best part... it is accurate to as many decimal places as you can set your prefs to, so (at work) we export for prototypes all the time. It has import/export filters for just about everything so you never worry what someone else is using.

I know this sounds like a plug, but it isn't. This is easily one of the best softwares I've ever used and that's since and including the AppleII+. You couldn't pay me to give it up. I'm getting the office to buy the Penguin this month. Actually, I am. It helps to be the purchaser.
 
I've got a couple of comments, so take them for what they are worth.

1. I think that some of the impact of low bass comes really, from the ability to generate high spls. This requires swept volume-period. I currently have two ML TQWT's in my house, and working on a third. One has a 5.25" driver and an f3 around 40hz. The other is based on an 8" and has an f3 around 30hz. The difference is quite astounding. It is not explained by the 10hz difference.

2. Two 6.5"s should be better than an 8" as there is 30% more cone area, but your internal Sd will have to be 30% more, give or take, depending on your model. So if size is important, two 6.5's is more problematic for you.

3. Consider a short, squat ML TQWT. The line length in my 3 ways is only 40" and the base is a 12x12 square. I guess it depends on your definition of large.

4. Not to poo-poo TL's, as I'm very found of them, but I think for a sub only application, I'll assert (without supporting arguement-too lazy right now) that a sealed box is better and smaller to boot. If you're really only going to run it under 100hz, well...
But, for a 2 way or 3 way with an 8" LF driver, it's hard to beat the sound of a TL.

You can see a picture of my three way on Martin's site. Sooner or later I'll get to veneering it. I'm still working out the bugs of my 3rd crossover.

Mark K
 
planet10: McNeel has no plans to re-write for Mac. My guess is that since the market for Macs has more computer funds than PC, they expect fairly slow sales for the Rhino. My only wish list is the same as everyone else's - parametrics.

Kneadle: Dragon? Huh?

ucla88: I am also trying to extend my music down to the last octave and most sealed and ported subs roll-off too quickly at the bottom. To prevent this roll-off, I figure to need a large driver and box the same or larger in size. As for air volume being moved, I'd guess that there is twice the air in a TL for any given driver, since the terminus wave is supposed to be in phase. Hence my forward pointed opening. A sealed system can only move the air in front of the driver and a ported box can only add the air out of the vent.

Bose(o): Thanks for the leads.


:)ensen.
 
ucla88: I am also trying to extend my music down to the last octave and most sealed and ported subs roll-off too quickly at the bottom. To prevent this roll-off, I figure to need a large driver and box the same or larger in size. As for air volume being moved, I'd guess that there is twice the air in a TL for any given driver, since the terminus wave is supposed to be in phase. Hence my forward pointed opening. A sealed system can only move the air in front of the driver and a ported box can only add the air out of the vent.

A couple of things. The phase relationship at the terminus is not a constant-it varies with frequency. It happens to be 90 degrees at the quarter wavelength frequency. I don't want to get into the debate on how fast TL's roll off (again;) ) but ultimately they roll off at 24db/oct. A sealed box rolls off at twelve.

A sealed LT transformed box will give you the lowest extension possible, assuming you've got the swept volume and amp power.
 
ucla88 said:


A couple of things. The phase relationship at the terminus is not a constant-it varies with frequency. It happens to be 90 degrees at the quarter wavelength frequency. I don't want to get into the debate on how fast TL's roll off (again;) ) but ultimately they roll off at 24db/oct. A sealed box rolls off at twelve.

A sealed LT transformed box will give you the lowest extension possible, assuming you've got the swept volume and amp power.


I agree. In fact, they all exhibit phase variances.

Yes, I also don't want to debate the various enclosures. They all have their merits or we wouldn't see them in the premier studio monitors from Genelec (ported), Mackie (radiator) and PMC (T-line). Post #16 will partly explain my choice of a TL.

What do you mean by "LT transformed" and is it really 24db/oct?

My understanding of rolloff is that it starts at Fr of the box, in which case the extension of the TL means that the 24b/oct starts lower than for a sealed box at 12db/oct. My analogy is that I have a choice between a gently sloping downhill or a plateau with a cliff. Since I (probably) cannot hear below 20Hz, then I would prefer a cliff that dropped off at 20Hz rather than a slope that started at 40Hz. Just don't go near the cliff...

:)ensen.
 
Many thanks again to Martin for his theory. The calculations worked out to So = 56 sq in and Sl = 12 sq in with L = 73" and offset just under 24" so I end up with something that looks like a Voigt pipe with the point sawed off and bent around a couple of corners.

I couldn't do this shape without the 3D modeller. I'm pretty good at sketching, but the software let's me keep an eye on the cross sections, which taper smoothly from one end to the other. It's still a box and so is fairly easy to build, although I still haven't figured out how to fabricate the large radius bends. I definitely don't want to be forming plywood and will work something out in MDF before I start.

The 2 axis tapers are in reverse initially as the width expands and the depth decreases. Then, after the bend, I run almost parallel and let the decreasing width take care of the changing section. Finally, the last bend is almost constant width so the depth changes.

The radii for the bends are not complex curves. I still haven't figured out the best snap points for my splines, so for this, I'm running an averaged radius. In the case of the big bend, there are two arcs of R=3.25" each and there is a small 1/4" section of flat at the bottom to make up the overall depth at that point.

This one will not be final design as the cabinet is top heavy and the driver is too far from the terminus. I'd like to get them both fairly close to the top of the unit so that I can take advantage of any directionality in the output and have them both near any mains that might rest on top. Besides, a driver that close to the ground is a little too near all the footwork, pets and 2-year old nephews.

:)ensen
 
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