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Old 28th March 2008, 07:42 PM   #1
schmeet is offline schmeet  United Kingdom
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Default TL Enclosure Design

Hi,

I want to build a transmission line enclosure for a Volt B2500.1
http://www.voltloudspeakers.co.uk/Lo...y_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...
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Old 29th March 2008, 05:06 AM   #2
GM is online now GM  United States
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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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File Type: gif volt b2500.1 10-1 25 hz tqwt.gif (6.7 KB, 431 views)
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Old 31st March 2008, 08:53 PM   #3
schmeet is offline schmeet  United Kingdom
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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
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Old 31st March 2008, 09:20 PM   #4
schmeet is offline schmeet  United Kingdom
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Also, WRT the port on a MLTL, would it not be possible to use a PR instead?

Cheers again,
Pete
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Old 31st March 2008, 11:13 PM   #5
bjorno is offline bjorno  Sweden
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Quote:
Would a MLTL be smaller?
Yes it can. See picture 1(1)

b

1(1)
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File Type: gif volt b2500.1_1cu-ft_-ml-tl.gif (57.9 KB, 374 views)
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Old 1st April 2008, 12:44 AM   #6
GM is online now GM  United States
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Quote:
Originally posted by schmeet

What is zdriver.

We have had this discussion before i believe.........
Distance down from the closed end.

Yeah, do a thread search on yourself..........

GM
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Old 1st April 2008, 11:13 AM   #7
schmeet is offline schmeet  United Kingdom
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lol,

But there was no conclusion.

Some people said it shouldn't be done, but others believe you can?

Might just build a box and see what it does.
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Old 1st April 2008, 03:03 PM   #8
GM is online now GM  United States
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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
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Old 1st April 2008, 06:25 PM   #9
schmeet is offline schmeet  United Kingdom
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Hmm.. ok.

So easiest way is to place the drivers at the same place then?

I might try and work my head around a way to do this without having the drivers side by side then...

Thanks for your help by the way..

Regards
Pete
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Old 2nd April 2008, 07:59 PM   #10
schmeet is offline schmeet  United Kingdom
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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
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