Lets do it all again: TL Sub.

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Qi, do you have pictures of your project? I did not see any in the thread, but have yet to go through it.

Sorry for the abysmal quality. That's all I had at the time...

http://www.diyaudio.com/forums/showthread.php?postid=256243#post256243


Your drawing has a box on the end of a very long port. The excess area of that box needs to be filled or it may not be a TL and just end up a BR with a very long port.

The chamber will acoustically filter upper frequencies. For a subwoofer design like this, it should not be an issue. Worst case, just stuff to taste...
 
Another concern I have with both layouts is that you will need to fill some of the void in those chambers. You don't want to end up with a BR with a very long large port.

Bose (who allegedly "spent millions and took years" researching tlines) actually recommends a rear chamber / tline ratio of 2:1 in their acoustic wave patent

http://www.diyaudio.com/forums/showthread.php?postid=667090#post667090

My rendering / proposal is based on a 2:1 ratio acoustic wave tower I posted about a year ago...

http://www.diyaudio.com/forums/showthread.php?postid=690341#post690341
 
This isn't an acoustic wave cannon, which has two separate pipes that are both end loaded. Now you're starting to bring back memories of why I didn't try the cannon back when that thread was alive, and it was concern over SQ. I think I'll stick with Danley and something claimed to outperform even his own contra bass with "single digit distortion and incomparably low group delay".

Qi, in the email you've referenced regarding tapering of the Danley sub, was it a positive (increasing CSA) or reverse taper?
 
johninCR said:
Qi, in the email you've referenced regarding tapering of the Danley sub, was it a positive (increasing CSA) or reverse taper?

Only that it was tapered, and how that contributed to its outstanding performance.

But clearly this pic shows an expanding taper, doesn't it?

It sure looks like it to me...
 

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Qi,

2 things still leave me uncertain. First, your pick is not the terminus of the production model for the upright version. Second, if you look closely in the literature for the production model, the DTS20, the response graphs don't match the extension claims and on those graphs the name is PB12, not DTS20. This leads me to wonder about the possibility of 2 different prototypes, one tapered and one straight, and that the production model is straight. Further support is that using MJK's spreadsheets, tapering shows an earlier roll-off like pictured in the graph, and straight results in deeper extension more like what is claimed with a small sacrifice in efficiency.

Still, Danley is a horn guy, he calls it a tapped horn. and I've never heard of a straight horn.

It's important to me because extension is what I'm after, not 120+db. Modelling longer lines doesn't result in a corresponding increase in LF extension without massive changes in overall cab volume. I hope it's not something like air density that causing almost a brick wall around 18hz, because I'll really get screwed since I live at about 5000ft.
 
johninCR said:
Qi,

2 things still leave me uncertain. First, your pick is not the terminus of the production model for the upright version. Second, if you look closely in the literature for the production model, the DTS20, the response graphs don't match the extension claims and on those graphs the name is PB12, not DTS20. This leads me to wonder about the possibility of 2 different prototypes, one tapered and one straight, and that the production model is straight. Further support is that using MJK's spreadsheets, tapering shows an earlier roll-off like pictured in the graph, and straight results in deeper extension more like what is claimed with a small sacrifice in efficiency.

Still, Danley is a horn guy, he calls it a tapped horn. and I've never heard of a straight horn.

It's important to me because extension is what I'm after, not 120+db. Modelling longer lines doesn't result in a corresponding increase in LF extension without massive changes in overall cab volume. I hope it's not something like air density that causing almost a brick wall around 18hz, because I'll really get screwed since I live at about 5000ft.


Re - altitude / temp -- Well, I am no expert -- but take a look here...

http://www.digitaldutch.com/atmoscalc/index.htm

It looks like the speed of sound is about 2 1/2% faster for you.

Just adjust your calcs accordingly?

It seems like at this point a "leap of faith" is in order for you since we 'll never REALLY know :D
 
Well, I don't know how I can communicate what I am thinking to you guys, but I am absolutely positive my current designs will allow me to test end of line loading, 50-50 like the transflex, or 25-75 like the TOP nwith slight changes. So lets move on to the real problem now.

Which Is with this chamber. Should I stuff it or make it as small as possible. Since it is supposed to be endloading the line, my intuition would say to make it as small as possible and fill the voids with a solid. Hearing QI's comment about filterin Higher frequencies makes me wonder though. I know from experience that in the WO from decware, the compression chamber does this.

However, that is a different animal and not a TL. Perhaps I will have to try thes two changes also.

That gives me what, 6 different box designs to test? lol
 
Relax said:
Well, I don't know how I can communicate what I am thinking to you guys, but I am absolutely positive my current designs will allow me to test end of line loading, 50-50 like the transflex, or 25-75 like the TOP nwith slight changes.


Nope. You're at 0% from the end. 25% for the end is at the other end of the cab, unless you're thinking of flipping the cross bracing around too, which won't work, though theoretically possible. 0/100 for the transflex is possible with a different driver orientation and opening up 2 of the triangles.


Which Is with this chamber. Should I stuff it or make it as small as possible. Since it is supposed to be endloading the line, my intuition would say to make it as small as possible and fill the voids with a solid. Hearing QI's comment about filterin Higher frequencies makes me wonder though. I know from experience that in the WO from decware, the compression chamber does this.

However, that is a different animal and not a TL. Perhaps I will have to try thes two changes also.

That gives me what, 6 different box designs to test? lol

Stuffing won't do it. Stuffing increases the apparent size of the chamber as far as the driver is concerned.
 
johninCR said:


Nope. You're at 0% from the end. 25% for the end is at the other end of the cab, unless you're thinking of flipping the cross bracing around too, which won't work, though theoretically possible. 0/100 for the transflex is possible with a different driver orientation and opening up 2 of the triangles.




Stuffing won't do it. Stuffing increases the apparent size of the chamber as far as the driver is concerned.


So no stuffing for sure? Ok.

Why would flipping the internal cross bracing not work? That is indeed my plan for testing. Once I settle on the final design I will then seal everything up permanantly.
 
Relax said:
Why would flipping the internal cross bracing not work? That is indeed my plan for testing. Once I settle on the final design I will then seal everything up permanantly.

Because it won't seal well enough. Once those are in, they're in, so seal them up. Make your end box detachable instead, which is probably easier and you can make some kind of gasket to seal it well and remain changeable.
 
Alright then, perhaps the sub mounting position will be removable and swapable.

QI, what do you think of John's recommendation? John seems to have his head on his shoulders, but you did recommend a box that could be changed easily from different alignments first. So I should wish to hear what you think about stuffing the chamber with solid wood.

One more question, this is for anybody: (lol)

Can I expect to listen to movies and whatnot with LF tracks the way they are meant to be with these subs? Or would I be better off aiming for low extension with a large ported or linkwitz sealed box?

Thanks for everyone's help so far, these babies will be built and running no later than a week after Independence day!
 
Sorry guys.

THE BOSS (wife) pulled me away onto another project (pressure wash / stain 750 sq ft 3-tier deck).

Relax

My two cents...

Stick to your original plan and end-load it for maximum bottom-end.

Use GM's recommended calcs and be done with it.

Do not stuff.
 
QI, what do you think of John's recommendation? John seems to have his head on his shoulders, but you did recommend a box that could be changed easily from different alignments first. So I should wish to hear what you think about stuffing the chamber with solid wood.

As long as the chamber is not overly large, but comfortably large enough to house the driver, it should not be an issue.

Hey, don't take my word for it. Here it is from THE MASTER himself...

http://www.diyaudio.com/forums/showthread.php?postid=911621#post911621

Also -- pre-chambered tlines (aka Dalines) are not uncommon. See here...

http://homepage.mac.com/tlinespeakers/TLS/design/foldings/images/daline.gif

...and here

http://homepage.mac.com/tlinespeakers/TLS/design/foldings/images/RS6_Xparent.JPG
 
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