Eminence Beta LTA12

opa1 · « **on:** 7 Jul 2015, 04:12 am »

I've searched here and cant find any good info on builds with this driver. I know some have used it in OB's. Does anyone know of box builds that have been done?

JohnR · « **Reply #1 on:** 7 Jul 2015, 04:32 pm »

I can't answer the question, but I would make a suggestion: do some simulations of the driver with a box modeling program and then you can learn for yourself if it's even in the target area for what you are thinking of building.

FullRangeMan · « **Reply #2 on:** 7 Jul 2015, 05:02 pm »

What is use intended for this driver? Pro-audio of HiFi?
If Pro-audio you can try the recommended BR box by Eminence around 115L.
Seems a good driver for 2 way stage monitor.

opa1 · « **Reply #3 on:** 7 Jul 2015, 06:18 pm »

I'll do some modeling. PE showing around a 7.72 for ported cab. Will be single driver w/phase plug. These would be used for my garage system with tubes.

JohnR · « **Reply #4 on:** 8 Jul 2015, 03:01 pm »

To me, that seems like a pretty big box, and the top end is awol...

FullRangeMan · « **Reply #5 on:** 8 Jul 2015, 07:33 pm »

Quote from: opa1 on 7 Jul 2015, 06:18 pm

I'll do some modeling. PE showing around a 7.72 for ported cab. Will be single driver w/phase plug. These would be used for my garage system with tubes.

I was referring to Eminence plans:
http://www.parts-express.com/pedocs/more-info/290-409-eminence-beta-12lta-more-info.pdf
But I also prefer the bigger PE project for more bass.
I suggest you use oneway direct, with good internal stuffing.
I could not recommend a tweeter and xover, even with the short treble to get the time/freq and full harmonic content.

Seems its around 217Lts and 39Hz bass, interesting performance w/97db sensitivity.

opa1 · « **Reply #6 on:** 8 Jul 2015, 08:51 pm »

That's what I'm thinking too. I have some 7.18 ft^3 cabs. Have to figure out port size. I have some hearing loss, so the upper end is not that important. Should work well with tubes.

FullRangeMan · « **Reply #7 on:** 8 Jul 2015, 08:59 pm »

You should ask PE before the purchase for the entire project.
Which include stuffing suggested and BR port or vented port.
This box will work if the baffle hole fit.
If not try these:
Small: 40 x 52 x 105cm = 218L
Tall: 40 x 40 136cm= 217L

FullRangeMan · « **Reply #8 on:** 8 Jul 2015, 09:02 pm »

There is a long thread here about this driver,
some remove the dust cap for less resonance:
http://www.diyaudio.com/forums/full-range/179161-beta-12lta-3cf-box-port-size-33.html

opa1 · « **Reply #9 on:** 8 Jul 2015, 09:21 pm »

Thanks for the link! I didn't find it when I searched there. I am planning on phase plugs.

FullRangeMan · « **Reply #10 on:** 8 Jul 2015, 09:50 pm »

Wood or aluminium phase plug?

opa1 · « **Reply #11 on:** 9 Jul 2015, 12:39 am »

I'll use wood for the plug. Just read all 41 pages of the link. A lot of good info too. Planet 10 has the dimensions for the plugs (44mmx62.5mm long). The LTA's should be here 7/13/15. If I can get the large live sound that I want, that will be great!

FullRangeMan · « **Reply #12 on:** 9 Jul 2015, 05:05 pm »

Good news.
PE has informed you the duct dimensions?
The box is vented or bass reflex?

srb · « **Reply #13 on:** 9 Jul 2015, 05:39 pm »

Quote from: FullRangeMan on 9 Jul 2015, 05:05 pm

The box is vented or bass reflex?

vented = bass reflex = ported, no?

FullRangeMan · « **Reply #14 on:** 9 Jul 2015, 05:51 pm »

BR boxes have a tuned duct, the know pipe:

=====
Vented boxes just have a opening, usually rectangular shape.
Not having the tuned pipe or duct:

srb · « **Reply #15 on:** 9 Jul 2015, 06:22 pm »

A ducted port and a rectangular slot port both fall under the design classification of Bass Reflex, as opposed to sealed or bandpass box designs.

opa1 · « **Reply #16 on:** 9 Jul 2015, 08:24 pm »

Quote from: FullRangeMan on 9 Jul 2015, 05:05 pm

Good news.
PE has informed you the duct dimensions?
The box is vented or bass reflex?

PE did reply. They said for my 7.18ft^3 cabs, I should use two 4" x 3.5"L ports. Also with this cab size the drivers should work very well. I really would like to make just one rectangular vent at the bottom of baffle. I need to do the math to convert the two round ports to the rectangular.

Scottmoose · « **Reply #17 on:** 10 Jul 2015, 09:31 am »

Not much math involved; assuming the aspect ratio isn't excessive (likewise that of the cabinet dimensions) then for practical purposes the vents will behave the same way irrespective of shape, so just ensure your rectangular vent has the same total CSA of the two existing vents, & is of the same length. Job done.

Re vented boxes, historically speaking a bass reflex is the classical type per Thuras; vented / ducted boxes followed on from the early 1960s, initially via Beranek & Novak, latterly via Thiele & finally by Small, who's filter-theory derived work still forms the foundations of what is widely used today, even if the methodology of implementing it has changed. These days we just lump them all into the 'bass reflex' category, assuming Helmholtz is the dominant resonant property of the enclosure.

opa1 · « **Reply #18 on:** 10 Jul 2015, 02:44 pm »

Did the CSA of the two ports. Looks like the combined CSA is around 50.27. So a rectangular vent 2.750 x 18 CSA is 49.5. Then the rectangular port would be 2.750 x 18, 4" in length?

Scottmoose · « **Reply #19 on:** 10 Jul 2015, 03:06 pm »

Assuming the original vents have a 4in internal diameter, then I make the CSA (pi*R^2) of a single vent as 12.566in^2, and that of two vents as 25.133in^2. It looks like you plugged the diameter of the circle into the formula rather than the radius.

If you keep the total CSA consistent then length is simply that of one of the original 4in ducts, providing you don't go to an excessive aspect ratio. A very small deviation in CSA or length is not likely to be audible & within driver tolerance levels, especially with a unit like the Eminence, which, while a worthy unit of its type, is not (and was not intended to be) the last word in high-fidelity.