What's the difference between a TL, a ML-TL and a TQWT?

[cangaceiro99]

MJK FE206E MLTL Port Size

I've built the Fostex FE206E BLH and now plan to try MJKs project 5 MLTL design for the FE206E.

I've built the cabs already and would like to know if anyone can advise the importance of the port size in relation to the design.

Basically his design recommends a 4inch (101mm) diameter port and length of 5 inches (127mm). The plastic ports they sell at the local audio parts shop are 110mm x 160mm.

This is a bit wider and longer than he recommends in his design, can anyone advise what effect positive or negative will this have on the response?

 

[GM]

Hmm, the pdf I have lists the vent length as 5 - 6" = 34 - 32 Hz, so it's probably well within spec. To check for sure though, Ron E periodically posts this vent scaling formula:

L2 = L1*(D2^2/D1^2)

where:

D1 = original diameter
D2 = new diameter
L1 = original length

L2 = 127*(110^2/101^2) = 150.64 mm

So, 160 mm being longer it will tune it fractionally lower, but the difference is too small to be audible, especially down low outside our acute hearing BW.

GM

 

[cangaceiro99]

Thanks for that formula GM, I was guessing I would have to shorten the length, but I wasn't sure to what degree.

i'll give that formula a try this weekend!

 

[ometbrnk]

I hope I´m in the right thread to ask this: How do I choose the cross section area for a MLTL? Shall I use MJK´s equation for TLs or is there another method?

 

[RockLeeEV]

I hope I´m in the right thread to ask this: How do I choose the cross section area for a MLTL? Shall I use MJK´s equation for TLs or is there another method?

At its core, an ML-TL is very similar to a bass-reflex alignment. In actuality, any bass-reflex that gets sufficiently long in a given dimension IS an ML-TL!

What I do is figure out a bass reflex internal volume for a given tuning frequency, figure out (roughly) how tall the speaker I'm designing will be, and then choose cross-section area based on what will give me that bass reflex internal volume. I input these numbers into MJK's worksheets, input the port dimensions as well (note: MJK's worksheets assume radius, many other box programs assume diameter!) and then tweak placement, cross-section area, and line length from there.

 

[ometbrnk]

I think I've found what I was asking/looking for in this thread written by Scottmoose.
http://www.diyaudio.com/forums/multi-way/70862-some-thor-models-mull-over-3.html#post804944

But thank you anyway.