TL subwoofer enclosuer questions (newbie)

Chucksrt

Member
2016-01-27 3:30 pm
I am learning as much as i can about TL enclosures but i am not sure i am keeping up with the math. I am heading to a friends to put a design and hopefully have some solid numbers together for him to put in autocad.
I am trying to build a subwoofer enclosure for a stereo integrity HT-18 4ohm dvc sub. for HT. I found a calculator online but i played with different widths for the enclosure the specs it produced were identical except for enclosure volume, it changed. I used mh-audio.nl - Home .my woofer specs are
Fs 17hz
Qes 0.41
Qms 5.8
Qts 0.38
Le. 3.2mH
Sd 117841mm^2
Vas 411.9L
Bl 19.7
Mms 416g
Cms 208.8
Sensitivity 88.7db
Xmas 22.5mm

I first entered the Sd and a width of 22.5 inches which game me specs for the enclosure but when i changed the width of the enclosure to 28.5 inch all of the specs were the same except for enclosure volume, that went from 740.63 litre to 935.54 litre. Am i missing something? I was hoping that if i changed the width that the transmission line length would shorten. The calc says the height of my enclosure should be about 7ft. I was hoping to shave something off of that. If anyone can just let me know if i am looking in the right direction or if i am just totally missing something that would be awesome! Thanks chuck
 
Just changing the width will not change the length of a transmission line. Leonard audio has an excellent free software for transmission line design. If the line is tapered changing width will have an effect on line length.line length is usually a result of the quarter wavelength frequency. The width is only related to cross sectional area which is based on size of the driver SD. This is only a rough explanation and there are many different factors that can influence a lines design.
Mark
 

Chucksrt

Member
2016-01-27 3:30 pm
I do not have a windows based computer to run any of the available programs. I just got back from my friends and we based are measurements off of a video we found on youtube. We came up with the t line length being roughly 13ft long and the cross section of the duct being just over 5 inches tall based on a 24 inch wide enclosure. I will try to get a windows based labtop soon to load all of the different programs on. For now if anyone can tell if we are at least getting warmer that would be great. I don't need a link to another worthless calculator.
 

Chucksrt

Member
2016-01-27 3:30 pm
Hmm, it's my understanding that many here don't have Windoze, but run the programs in some sort of emulator program. Anyway, I imagine there's a forum here where you can post about it.

GM

I am new to the forum. I looked for threads that may be able to help me but i was having an issue using the search feature from my phone. I am not sure what emulator you are referring to, i do know that all of the programs that could help me are based off of ghe Microsoft windows platform and the 3 apple computers and labtops i have will not operate any of the programs. I am just looking for a little guidance, i am not looking for hollow input that does not help. If you know of a specific forum that can help then i am all ears.
 
We came up with the t line length being roughly 13ft long and the cross section of the duct being just over 5 inches tall based on a 24 inch wide enclosure.

Last time, design using this doc [did you even look at it?] to see just how incredibly far off you are, which only requires a modicum of reading comprehension and math skill and a hand held calculator: http://www.quarter-wave.com/TLs/Alignment_Tables.pdf

An 18" 17 Hz, 411 L Vas driver tuned to Fs with a TL will be incredibly large. I don't have any of my software or the various programs loaded on this new computer yet, so don't know just how large, but the cross sectional area [CSA] is typically 3-5x Sd, so could be upwards to as much as nearly 3000 L!

A good rule-of-thumb then to decide if a TL is a viable option size wise is from ~ 4x-10x Vas depending on the desired tuning [Fp] and the driver's effective Qts, i.e. Qts + any series resistance due to wire/whatever losses, VC heating = Qts'

GM
 
I am new to the forum. I looked for threads that may be able to help me but i was having an issue using the search feature from my phone.

I noticed. ;)

Other folks have noted the phone/search issue, so use your computer. ;)

I don't pay any attention when folks post about it, but seems like BOOT CAMP? or some-such was one quite awhile back.

I just now Googled 'running windows on a macintosh' and it returned loads of info: https://www.google.com/webhp?source...v=2&ie=UTF-8#q=running windows on a macintosh

I don't have a cell phone, much less a smart one, so don't know if you can Google with it, but you have a computer............

GM
 

Chucksrt

Member
2016-01-27 3:30 pm
Last time, design using this doc [did you even look at it?] to see just how incredibly far off you are, which only requires a modicum of reading comprehension and math skill and a hand held calculator: http://www.quarter-wave.com/TLs/Alignment_Tables.pdf

An 18" 17 Hz, 411 L Vas driver tuned to Fs with a TL will be incredibly large. I don't have any of my software or the various programs loaded on this new computer yet, so don't know just how large, but the cross sectional area [CSA] is typically 3-5x Sd, so could be upwards to as much as nearly 3000 L!

A good rule-of-thumb then to decide if a TL is a viable option size wise is from ~ 4x-10x Vas depending on the desired tuning [Fp] and the driver's effective Qts, i.e. Qts + any series resistance due to wire/whatever losses, VC heating = Qts'

GM

This is the first time i have seen this article. Thank you! Although i will absolutely need to share this with my friend who is a math head! Lol. I will read this over and see how much of it i can comprehend. I knew the enclosure would be massive and my thought process was to lay the enclosure on it's side and use it as a base for a audio/video console. I am sure i can't attach photos yet but i am basing that off of a design i found where they dressed the enclosure up to look like an entertainment center. Just an awesome way to package it for the wife happiness factor (trying to hide it in plain sight). The system will be going into a dedicated HT Room eventually so i am not overly concerned about the size.
 

Chucksrt

Member
2016-01-27 3:30 pm
I noticed. ;)

Other folks have noted the phone/search issue, so use your computer. ;)

I don't pay any attention when folks post about it, but seems like BOOT CAMP? or some-such was one quite awhile back.

I just now Googled 'running windows on a macintosh' and it returned loads of info: https://www.google.com/webhp?source...v=2&ie=UTF-8#q=running windows on a macintosh

I don't have a cell phone, much less a smart one, so don't know if you can Google with it, but you have a computer............

GM


I do have a old macbook That i can try this on. Awesome!!! I do all of my research via my smart phone. I couldn't even tell you the last time i used my pc. Lol . I will try to get windows and then return to my Friends house to crunch numbers. Thank you for the Info:)
 
13 ft is generally a good length for a straight non tapered line. For cross sectional area I use approx SD for a non tapered line . my tapered line starts with an area 5xSd. Also if you offset the driver approx 1/3 down the line you get rid of the first null. For an 18" driver cross sectional area should be 180 sqin give or take or 10"x18". These are just general guidelines for line.martin kings site is excellent so is the work of ausperger back in speaker builder magazine. Bjorno is our one of our best here on transmission line design and the variants
Mark
 

Chucksrt

Member
2016-01-27 3:30 pm
13 ft is generally a good length for a straight non tapered line. For cross sectional area I use approx SD for a non tapered line . my tapered line starts with an area 5xSd. Also if you offset the driver approx 1/3 down the line you get rid of the first null. For an 18" driver cross sectional area should be 180 sqin give or take or 10"x18". These are just general guidelines for line.martin kings site is excellent so is the work of ausperger back in speaker builder magazine. Bjorno is our one of our best here on transmission line design and the variants
Mark


Thanks for the input Mark! It is good to see that i am on the right path. I am horrible at math so having my best friend be an engineer and awesome at math is how i will be moving forward. The amount of time we will be spending together on this will definitely cost me in beverages! Lol.

the Macbook my wife was going to let me use to try to install windows on wouldn't even boot up so i bought a labtop used online that should just be ready to load and run anything i can throw at it.

What is the benefit of tapering the port (making it larger) prior to the cross sectional area that matches the sd of the woofer? I know that tapering it after that point can tighten the sound or faning It out after that point can increase spl or make it boomier. Sorry if this may be a silly question but when reading about it i couldn't find what it changes . I know the area where the woofer will sit will need to be larger just due to the size of the basket, but does making it a specific size larger change it?
 
You don't need to be awesome at math for this. If you actually read the paper GM linked to there's only one formula that needs to be solved. And IIRC there's a spreadsheet based on the paper that will do the calculations for you at the same place you download the paper. That wasn't available when I was trying to figure this out 10 years ago.

The paper also covers tapering in some detail with a chart and pictures. For a given tuning a 10:1 (negative) taper will make for a smaller cab with a shorter line and it will perform similarly to a ported box (although the terminus may end up too small to control port velocity issues), while a 1:10 (positive or horn shaped) taper will make for a very large box with a much longer line length and perform more similarly to a horn (although the resonances might be a bit wild).

All your questions are answered in detail in the paper, you need to read it. I wouldn't build a design based on the alignment tables alone (I'd simulate it first) but the paper gives you all the information you are looking for.
 

Chucksrt

Member
2016-01-27 3:30 pm
I installed the leonard audio tl calculator and ut is asking me to input the Lvc or voice coil inductance. My sub does not have that listed and i also have a dual voice coil sub, do i (once i figure out how) measure each voice coil separately or wired together . And when inputting the ohms , am i doing that for each voice coil or list the ohms how it will be run wired together
 
In post 1 you posted the specs, Le is included and that's what you are looking for. You also need Re which is missing in post 1, it's 3.5.

The given specs on the SI site are measured with the voice coils in parallel so you don't have to do anything, just input the specs as they are.

This is a large voice coil sub and it won't sim accurately, I would adjust Bl to compensate but I'm not going to explain all that now.
 

Chucksrt

Member
2016-01-27 3:30 pm
I am really trying to find a way to understand all of this, i tried reading and understanding what i have read and i just do not. i will be meeting with my friend to see if he can give me the formula we used to come up with what we did. i keep being told where to find a good formula but all i see is a hundred formulas for different things, none of which tell me what i need or if they do I don't understand it. I am so frustrated. i will post the formula i used i will also
Fs= 17 Hz
Vas= 14.546 ft^3 411.9 L
Height= 48 in
Width= 36 in
Depth= 23.2878184 in Assuming 4 chambers
Cone Area 1.26798865 ft^2 182.5903656in^2
x= 12.925ft
Opening (O)=5.0719546
y= 21.66344294
y= 21.66097806

this is what we used. i am willing to give up and pay someone to design this because it is proving to be beyond me. once i have a design i am good. i bought a windows based computer just so i could download programs that i could not on my mac only to find i do not understand what i see. i do not see a "formula" for designing an enclosure. i do not understand how to use leonard audios tl calc. i seriously want to cry! i really wanted to be able to understand especially when it seems so easy for so many others. sorry i just feel defeated.
 
You don't need any formulas at all, and what you got from the formula you used doesn't make any sense to me at all. What is depth assuming 4 chambers? TLs don't have 4 chambers. What is x and what is y and why are there 2 y's? If the opening is in sq inches why is it so small? Why are only fs and vas and Sdlisted? You can't design with only those 3 parameters.

Anyway, I think it's safe to assume that whatever you just posted is garbage. I'm busy today but if you can wait until tonight I'll throw a bunch of information your way.
 
Ok, first of all you have chosen a large driver, it's going to need a large box. Additionally, the large coil that provides the very high excursion and moderately high power handling means that this driver will not match sims, you can adjust Bl a bit to make the sims match measurements a bit better, but this means the box will need to be even larger.

If you don't want to (or are unable to) learn how to do this the best thing to do is look for existing designs for this driver. Most people use them in 3 - 6 or so cubic foot sealed boxes and get the results as measured by data-bass. i can't link directly to the driver page on data-bass but you can look it up.

If you don't want a sealed box there are ported box plans for this driver like this one - Cycl?ps 18 - AVS Forum | Home Theater Discussions And Reviews
At 12 cubic feet or 340 liters, you will see that a resonant design for this driver will need a big box. A tl will be even bigger.

There's even a very low tuned front loaded horn for this driver but at 38 cubic feet (1075 liters) it's very large. SubMaximus -- A Large Front-Loaded Horn for UXL18 and Stereo Integrity HT 18" - AVS Forum | Home Theater Discussions And Reviews

Getting back to tl design, you were directed to MJK's alignment tables several times. I have a feeling you did not read the article or download the spreadsheet. The spreadsheet alone will give you a starting point (if you want to refine with simulation) or a final design (if you want to end there).

This spreadsheet could not be easier to use, it's braindead simple and no special functions so it should open with Open Office if your PC doesn't have Excel. There are only 6 inputs, 5 of those are t/s parameters and the last one is the line geometry. Since it sounds like you want a straight (non tapered) tl, leave SL/SO at 1. If you wanted to taper it you would change that.

I'm going to use the specs provided on the SI site for this example to help you figure this out but ordinarily I would use the data-bass measured specs.

And here's what we get. We'll ignore the fs warning for now, and also ignore the large coil issue and leave the specs exactly as stated by SI.

b93l2.png


The design details output are in yellow and that's the design.

A line length of 502 cm and a cross sectional area of 858 sq cm.

So let's enter that into the Leonard Audio software and into Hornresp and see what we get.

334ru4x.png


The first 3 images are the Leonard Audio software, the last 3 are Hornresp.

Image 1 - shows how to enter driver specs into Leonard Audio TL.app
Image 2 - shows the enclosure details - note that the ONLY things you need to put in are "start area" (858 sq cm), "end area" (858 sq cm) and "length" (502 cm).
Image 3 - Frequency response at 600 watts
Image 4 - Hornresp inputs for the same tl in Hornresp at 600 watts
Image 5 - Frequency response at 600 watts, note it's almost identical to the results from TL.app
Image 6 - Displacement at 600 watts (still well within SI's claimed xmax if you use a high pass filter), tuning is around 17 hz

Note that this enclosure is 431 liters and it's still smaller than ideal. Especially when you figure in the large coil issue, which will effectively lower the motor strength (you can simulate that effect by lowering Bl to about 16.3 and this will make the enclosure even less adequate in terms of size than shown here).

All inputs are shown in both TL.app and Hornresp, so if you can't figure out how to input and manipulate these programs you need to read the instructions or just find an existing design and build that.

If you want to play with these sims a bit, the first thing I would do is change the size and/or shape, this is done by adjusting "start area", "end area" and "length" in TL.app, and by adjusting S1, S2 and L12 in Hornresp. If you decide to make a reverse taper tl or do anything else to make the mouth size smaller make sure you check velocity to make sure it stays within reasonable limits.

Next thing I would try is adjusting driver location. In TL.app just grab the driver handle and move it down the line and drop it wherever you want. In Hornresp, change Nd to Od, create another segment and then use the Loudspeaker Wizard to adjust anything you want.

The third thing I would try is adding stuffing, any tl needs stuffing. Both these programs can simulate stuffing so read the instructions and figure it out. Ideally stuffing should be kept well away from the mouth so start by putting stuffing in the first half of the line.

These results may look a bit shocking with the ragged frequency response and huge peaks and dips but that's what tls do and you need to adjust size and shape of the tl, driver location and stuffing to get it as smooth as possible.

I assume you wanted to do a tl because of some kind of garbage online description that makes tls sound like magic, probably from the same place you found the garbage formulas, but tls are not magic. Reverse tapered tls with a 10:1 taper ratio and adequate stuffing perform very much like ported boxes and will be a similar size. Straight tls will perform maybe a bit better than a ported box but will be much larger and the frequency response is very hard to flatten. Positive taper (horn shaped) tls will be louder than a ported box but will be VERY much larger and the frequency response can be difficult to flatten.

Again, the best thing MIGHT be to build a proven design, either a sealed box as small as 3 cubic feet or something like the ported Cyclops I linked to, or the Submaximus front loaded horn.