TL Enclosure Design

schmeet

Member
2008-03-06 4:28 pm
Hi,

I want to build a transmission line enclosure for a Volt B2500.1
http://www.voltloudspeakers.co.uk/Loudspeakers/Studio_Range/B2500_1/body_b2500_1.html

Fs is 25Hz but has low Qts so i'm guessing a tuning freq of around 30Hz would be better.

A Tapered TL would need to be around 8 - 9ft long. I havn't looked at ML TLs at all. What kinda size would one of them need to be?

I would like to use a pair of these drivers to get even more power handling, although i realise that this would need a doubling of line area, and i think this would result in an enclosure being way too big.

any ways around this? Would a MLTL be smaller?



Has anyone already got any enclosure designs for this driver?


Thanks alot
Pete

P.S.
I know it would help if i got MJKs worksheets, but i'm on my rents laptop and they wont let me install any software on it.. Grrr...
 
Greets!

A TL will ~mirror a driver's IB response, so about the only difference between 25-30 Hz will be size.

Hmm, a 10:1 25 Hz TQWT only needs to be ~70" long/~1.2851 ft^3 net.........

Due to the driver's low Fs, Vas and Qts, it's not as suitable for a low Fb as the TQWT and no smaller once you factor in the long vent required.

L = 70"
SO = ~67.2"^2
SL = ~6.72"^2
zdriver = 5"
stuffing density = 0.25 lbs/ft^3 of polyfil shown

GM
 

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schmeet

Member
2008-03-06 4:28 pm
Ok, well that is fairly small indeed!

Quite pleasing really. So if i were to use two drivers i would simply double the cross sectional area?

So i would have:

L = 70"
So = 134"^2
SL = 13.4"^2

What is zdriver.


If i were using two drivers, i wouldn't be able to make the baffle wide enough to position the drivers in the same place along the line.

We have had this discussion before i believe , but can i place two different drivers along the same line at different places? Can the worksheets model this?

Thanks
Pete
 
Well, my conclusion is you can and the proof is the TH, but look at the various plots on that thread to see the potential for failure to achieve as good a response as a single driver due to bjorno's example, then factor in what it takes to get a smooth response beyond a two octave pass-band and the 'safe' conclusion for most folks in IMO and AFAIK Bjorno's, is to avoid it like the plague.

That said, if you want to pursue it, then use MJK's software to design each layout and manually sum the two response plots to see what positions work best. Hint, one will be at one end, so this just leaves the rest of the length to try. ;)

GM
 

schmeet

Member
2008-03-06 4:28 pm
GM,

I have taken into account what you said about two drivers. Where if you put them very close together, you can take the center point as being where the "actual driver is".

Well in the design you gave me zdriver was 5" (12.7cm). Well it is 14cm to the center of the first speaker, so the closest i could get it would be 28cm (11").


How would this effect the response? Is there anywhere better to place the driver which is a bit further down the line?

Many Thanks
Pete
 
You're welcome!

Well, what can I say, I was in a hurry as usual and I'd already done a design ages ago for this driver, so just posted it without really reading your post in detail ergo didn't notice you were planning to use two drivers.

Bottom line, make the pipe twice as large at each end and 'connect the dots' with the drivers at the top.

MJK recommends putting the driver at 0.336*L = 23.52" down and while its marginally smoother to ~200 Hz, this is a sub, so end loading yields the most gain up to ~110 Hz.

GM
 

schmeet

Member
2008-03-06 4:28 pm
Thanks again,

I've have already done the design for two subs, (i.e. doubled the CSA) it was just putting the driver at the zdriver location i couldn't do.


I may use MJK's recommendation for zdriver as it allows me to place it more easily and also while it is a sub, its going to be playing up to about 500Hz...