Opening a can of worms but...how do you calculate the slope inside a TL enclosure - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 21st August 2002, 04:18 PM   #1
diyAudio Member
 
Join Date: Aug 2002
Location: Toronto, Canada
Default Opening a can of worms but...how do you calculate the slope inside a TL enclosure

Sorry about this thread but...calling all TL experts!!!

Trying to find some good material to which I can understand Transmition Line enclosures. Got lots of very helpfull info on planet10's site...but still a little confused in how to calculate the "slope" inside a TL. What I meen is the "Line" or "Channel" that is made to produce the inside of the encloser.

I know that this is a large question but very willing to learn. If any of you can give me some laymence (need spell checker) termed formulas, or some good sites that explain...that would be most helpfull.

Thanks,

Rino Odorico
  Reply With Quote
Old 21st August 2002, 07:14 PM   #2
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Default Re: Opening a can of worms but...how do you calculate the slope inside a TL enclosure

Rino,

Are you trying to figure out how long the line is? Or where to place the internal baffles so that you get an even taper?

Do you have a driver in mind?

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 21st August 2002, 08:41 PM   #3
diyAudio Member
 
Join Date: Aug 2002
Location: Toronto, Canada
Basically, just wondering were to put the baffels to get the proper taper etc.

No driver in mind...yet. What it looks like, I will "play" with different drivers over time. I understand the length of baffle is dependant upon the Fs of the driver (1/4 wave).

I also understand, keep away from any 90 degree angles etc. Just, were do you start in placement of the "Line"...or does it matter as long as it works out to the proper volume displacement?
  Reply With Quote
Old 22nd August 2002, 12:14 AM   #4
diyAudio Moderator
 
pinkmouse's Avatar
 
Join Date: Apr 2002
Location: Chatham, England
Hi Rino

Yup. a big can of worms...

QWTLs are great speakers, if you get them right, but most of what you get on the web is hearsay, random experimentation or just plain wrong.

The few people who have tried to construct real models of TL design, esp. Augsperger and Martin J. King disagree on the effect of line taper on box response.

I have had good results with both tapered and non- tapered lines, but this was before I started measuring my boxes properly, previously I was just using my ears.

Quote:
No driver in mind...yet. What it looks like, I will "play" with different drivers over time. I understand the length of baffle is dependant upon the Fs of the driver (1/4 wave).
You can't expect any driver to work in a generic TL enclosure, just like any other style of box it has to be designed to work effectively with the driver.

Rather than trying different drivers in the same box, I would get a good quality driver, and build several different enclosures to find one that sounds good to you, or you could download Martin's software and try it all out in a virtual world ( not an option open to me as I run a Mac, and no one in England seems to have second hand copies of Mathcad!).

So, pick a driver first, then we can help
__________________
Rick: Oh Cliff / Sometimes it must be difficult not to feel as if / You really are a cliff / when fascists keep trying to push you over it! / Are they the lemmings / Or are you, Cliff? / Or are you Cliff?
  Reply With Quote
Old 22nd August 2002, 12:41 AM   #5
diyAudio Member
 
Bill Fitzpatrick's Avatar
 
Join Date: Jun 2001
Location: Eugene, OR
Perhaps while this thread is drawing attention, maybe someone can tell me why the line needs to be tapered.
  Reply With Quote
Old 22nd August 2002, 01:02 AM   #6
diyAudio Moderator
 
pinkmouse's Avatar
 
Join Date: Apr 2002
Location: Chatham, England
Hi Bill

According to a study carried out by Tyrland ( I think that's the correct spelling!) , tapering the line means that you can get away with a slightly shorter line and decreases the resonances at unwanted higher frequencies, but these are minor in effect compared to just folding the line rather than just having a linear pipe.
__________________
Rick: Oh Cliff / Sometimes it must be difficult not to feel as if / You really are a cliff / when fascists keep trying to push you over it! / Are they the lemmings / Or are you, Cliff? / Or are you Cliff?
  Reply With Quote
Old 22nd August 2002, 02:58 AM   #7
diyAudio Member
 
Bill Fitzpatrick's Avatar
 
Join Date: Jun 2001
Location: Eugene, OR
OK. Thanks pinkmouse.

Let's say you have gobs of room and the line can be as long as needed. My question would then be, "is an unstuffed, untapered half wave length line the best choice?
  Reply With Quote
Old 22nd August 2002, 06:15 AM   #8
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Quote:
Originally posted by pinkmouse
The few people who have tried to construct real models of TL design, esp. Augsperger and Martin J. King disagree on the effect of line taper on box response.
At 1st Martin didn't think taper had any effect. But as he refined the model based on actual results, and compared results with lines that Rick Schultz (exolinear) was doing using Augspurger's software, he has come to agree with Augspurger (not surprising since Augspurgers electrical analog and Martin's mechanical analog generate essentially the same lines).

A strong taper 3 or 4:1 improves the low pass function of the line allowing the use of less stuffing for the same amount of ripple thereby improving efficiency. This is at least partly due to the shifting of the harmonics of the fundemental up in frequency where the stuffing is more effective. The primary fundemental stays in the same place -- if you are designing for maximum bass reinforcement the line should remain at 1/4 Fs.

Bill: no matter how long you make the line, if it is closed at one end and open at the other end it is a quarter-wave resonator.

Back to the original question: getting a smooth taper is simply a matter of geometry. no folds is trivial. With one fold, you set the cross-section of the box to the area of the closed end + the area of the open end. Start your divider such that it divides the total area into these sub-areas. Then at the other end the partition is exactly in the middle and away from the end by the same distance it is from the walls. More folds is a little tricker, but you use the same technique. Any more explanation will require some pictures.

It should also be noted that the taper does not have to be linear. One fellow has gotten good results with an exponential taper and one has to admire the shape of exolinear's Augspurger modeled RS 40-1354 EXL.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 22nd August 2002, 02:10 PM   #9
diyAudio Member
 
Join Date: Aug 2002
Location: Toronto, Canada
Default Pictures please :>)

Sorry Dave,

But could you send some pictures, or drawings?

I'm trying to picture this in my head so I can understand it fully. It's just like pinkmouse had said, there are a lot of myths revolving around the TL design. And unfortunatly, I fell right into some of these myths...

Once I get on a new project I like to learn everything about it...so sorry about the anal retentavness (need spell checker)

Thanks to all that responded

Rino Odorico
  Reply With Quote
Old 22nd August 2002, 08:37 PM   #10
diyAudio Member
 
Thatch_Ear's Avatar
 
Join Date: Nov 2001
Location: Dallas,Tx
Rino,
I have been going crazy trying to figure out a cheap and easy way to build TLs. No matter what kind of design you end up going with there seems to be at least one common thing that starts the whole confusing aspect of this.
It is easy to figure out the length of the pipe needed for QW. But since hollow pipes tend to sound like hollow pipes you stuff them to stop the resonance.
When you stuff them you are effectivly adding length to the pipe by slowing down the sound from the driver. So you can not use a pipe whose length is based on a QW even though it is a QW you want to produce.
Isn't this fun?
__________________
Thatch
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
How to calculate an enclosure with variovent ? TomatoBangBang Multi-Way 4 16th January 2009 05:35 PM
NAD power lamps inside the enclosure destroyer X Solid State 13 9th October 2008 05:27 PM
Help calculate enclosure volume Sillyboy Multi-Way 25 6th May 2006 12:22 AM
how do I calculate the sub box enclosure? Tony.ca Multi-Way 5 8th June 2003 01:05 AM
Can of worms anyone ??? BR vs. IB Simon Multi-Way 0 30th July 2001 08:12 PM


New To Site? Need Help?

All times are GMT. The time now is 01:45 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2