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Old 3rd February 2005, 10:29 PM   #1
10K2HVN is offline 10K2HVN  United States
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Question Transmission Line / Seas Lotus...Help

Hello Everybody!

I currently own a Seas Lotus SW300 (12") subwoofer that I was originally planning to put in my car.

http://www.seaslotus.com/subwoofers.asp

http://www.seaslotus.com/specifications.asp (newer specs)

http://www.seas.no/Lotus/Lotus%20PDF/L0014.pdf (older specs)

However, Im temporarily using another subwoofer for ease of installation (Ascendant Audio Atlas's = Infinite Baffle .. vs Lotus SW300's = AP Enclosures--whered id have to build an enclosure and tune the membrane).

So in the mean time, Id like to build a box for one of my Seas Lotus SW300 woofers for home (sweet home )..

I'm interested in making a (folded) Trasnmission Line enclosure for this subwoofer, but im fairly new, and just barely grasping the concept behind TL enclosures (started researching yesterday).

Ive been searching and reading.. and have visited various websites.. and from what I read, it seems this subwoofer (spec-wise) would be suitable for a TL enclosure..(???)

There wasnt very many threads (on diyAudio, that I could find)
that truely cleared up everthing for me, but I did find this post, that seemed pretty simple..

Quote:
Originally posted by Skramstad
Formula for short transmission line:
Length = quarter wavelength of fs
Start area of line = 2*Sd
End area of line = Sd
If your crossover point is high, you should use some stuffing/insulation inside the line and make the line a little bit shorter.
From what I undestand, 1/4 wave of 20hz (fs of woofer) is about 14.09ft. So I would need a "pipe" about 14.09ft long with a closed-end of twice th SD of the woofer and an open-end of SD of the woofer..?

Thanks for your time and any help,
-1k

one more question..

Would there be another enclosure-type that would be better suited..?
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Old 3rd February 2005, 10:57 PM   #2
simon5 is offline simon5  Canada
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Better suited in which aspect?

Each enclosure have advantages and disadvantages...

If TL interests you, maybe you want to give a look at folded horns too.
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Old 3rd February 2005, 11:33 PM   #3
10K2HVN is offline 10K2HVN  United States
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i breifly looked into horns and snailshells..but those seem a bit more complicated then i planning right now..

plus you mentioned that each enclosure type has its advantages and disadvantages..

sealed - early roll off, but at a shallow slope.. -6db/oct

ported - boasted above tuned frequency (peaky), but steep roll off after tuned frequency.. -24db/oct

horns - im not sure at all..but i think ive read that theyre similar to ported in the roll off section....

TL - (from what ive read) gives a slight steady boast above the tuned frequency but a shallow roll off after/under it.. -6db/oct ..plus ive read that they virtually sound boxless...

^"..the best box is no box..." ..but i think when i read that they were referring to a Dipole setup...

i guess you can say im looking for something/anything "accurate" and "musical"...............?

im definitely not looking for some home theater boom...or car audio boom for that matter......
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Old 4th February 2005, 02:37 AM   #4
simon5 is offline simon5  Canada
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A ported box is not peaky by definition, it depends on how you tune it. It can be very musical and better deep bass than sealed if tuned low.

If TL interests you, did you look at this website?
http://www.quarter-wave.com

There's some knowledgable people on this forum about TL enclosures, they will probably reply soon.
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Old 4th February 2005, 05:19 AM   #5
10K2HVN is offline 10K2HVN  United States
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self correction:

sealed boxes exhibit at -12db roll off...

http://ldsg.snippets.org/boxes.php3

Quote:
Originally posted by simon5
A ported box is not peaky by definition, it depends on how you tune it. It can be very musical and better deep bass than sealed if tuned low.

If TL interests you, did you look at this website?
http://www.quarter-wave.com

There's some knowledgable people on this forum about TL enclosures, they will probably reply soon.
yeah..ive browsed through that website.. i need to start fresh if i actually try to read through that whole thing--or my head will explode..!

i like this website..

http://www.t-linespeakers.org/

^that spiral-TL on the front page looks awesome!

im actually thinking of making something like this..

Click the image to open in full size.


Ive read other threads that say for traditional ported boxes, it doesnt matter where the port is. My friend that builds SPL car's says the ports should be as far as from the subwoofer as possible.

^Does it really matter..?

^^Does it matter for TL enclosures??

because im also thinking of making something like this..

Click the image to open in full size.

but with the woofer closer to the bottom with the "open-end" right under it. (?)

btw, Thanks for your replys! :beer:
-10k
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Old 4th February 2005, 05:46 AM   #6
simon5 is offline simon5  Canada
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Well, mostly, port location is not important. But, I prefer it close to the driver. Some people prefer it behind so they hear less vent noise at high SPL if the port is a bit too small or something.
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Old 4th February 2005, 08:22 AM   #7
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Whatever you do, base it on modern TL modeling, not the cookbook approach (that is what you have pulled so far).

My site (where the pics came from), Martin's quarter-wave site, and Bob Brines site http://geocities.com/rbrines1/are required reading... my site has a lot of historical info on it -- many of those lines are not optimal. The 2nd pic you pulled shows the classic Bailey foldings but was just a concept for instance.

Start with Martin's tables at least -- your woofer is pretty well suited to a TL.

dave
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Old 4th February 2005, 09:27 AM   #8
Puggie is offline Puggie  United Kingdom
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Your comment for a port being as far away from the cone as possible generally holds well for building SPL cars where your aiming to make a silly high SPL at one point playing one frequency. it really doesn't work like that if your trying to make a sub for playing music though.
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Old 6th February 2005, 09:07 AM   #9
10K2HVN is offline 10K2HVN  United States
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Quote:
Originally posted by planet10
Bob Brines site http://geocities.com/rbrines1
you mean this site, right..? (in case it didnt work for anyone else)
Ill definitely read through those sites when i have time..

Thanks to everyone for their input!

-10k
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