For GM mostly

[Andrewbee]

HEllo GM,

I read of a design by you the "60" Jumbo JX design by GM" apparently its a TL sub for the Jordan JX driver.

Can you let me know some more?
I am thinking about trying a TL sub to mate with some OB speakers and wanted to give a TL a try.

Thanks

Andrew

 

[GM]

Greets!

Hmm, never seen any of my designs called this, but the JX150 is about 60" long, though it's a ML-TL:

T/S max flat:

L = 59.1"
CSA = 113.726"^2
driver down 21.33"
vent near/at the bottom
rp = 1.5"
Lp = 4.5"
density = ~0.2lbs/ft^3

All dims inside and you may need either a longer vent or damp it some if it's 'boomy' in-room.

GM

 

[Andrewbee]

Thanks GM. I read of it on the Audiocircle.


Andrew

 

[GM]

Greets!

Ok, another forum to add to my list. Anyway, is this what you're looking for, or a true TL?

GM

 

[Andrewbee]

Hi again,

I am looking for a true TL. I plan on doing some on open baffles and am looking at a bass solutuion. The Visatons will go down to ~70 hz before rolling off I figure.
I have never heard a TL but from what I read, when properly designed and working they are very hard to beat for bass quality.

I have in the back of my mind a pair of TL's using perhaps an 8" driver.
Power/crossover will be most likely be from a pair of plate amps.
I am open to suggestions.

I was going to ask Dave D. as well, TL's are his speciality but methinks he is busy right now with the new CSS drivers and his website.

Thanks

Andrew

 

[GM]

Greets!

Yeah, he's busier than a one armed paper hanger.

OK, a simple end loaded, stuffed 'classic' style 28 Hz Alpha TL for the JX150:

L = 117.375"
CSA = 84.964"^2
suggested density = 0.781 lbs/ft^3 of polyfil (~72 oz)

GM

 

[Andrewbee]

Thank you kind sir.


Andrew

 

[qi]

suggested density = 0.781 lbs/ft^3 of polyfil (~72 oz)

Hi Greg

WOW -- that's alot of stuffing!

Shouldn't it read .27 lbs/ft^3 of polyfil (not .78)?

Regards
Joe

 

[GM]

Greets!

It's correct for a 'classic' style TL, i.e. ~IB response with a highly damped Fs peak. Obviously, folks fine tune the stuffing to suit, but this is what he asked for and best for use with tube amps and/or integration with horns.

GM

 

[qi]

Hi Greg

The Alpha TL spreadsheet that you posted says .27 (not .78) for a Jordan JX150 -- hence my comment.

 

[GM]

Greets!

Hmm, I'm using the same one I posted to the forum and it's correct according to the MathCad sims I've done on various designs I've posted, so my SWAG is that you're quoting 'Z stuffing factor', which is used in the formula for the CSA (So/SL). 'Df'/'Dp' is the fiberglass/polyfil Vb stuffing factor, and since Imperial units are used, the amounts are in lbs/ft^3.

I really wasn't thinking when I blindly posted my little spreadsheet as is. I should have modded it so that the various design 'steps' were hidden and shown the calc'd ounces of stuffing required since they've caused way too much confusion. I have it on my rather extensive 'to do' list, but there's been so little interest in it after the initial posting that it's currently a very low priority.

Sorry for the confusion.

GM