Help with TL design

Keriwena · 25th February 2010, 11:54 PM

First, a bit about myself. I got into speaker design long, long ago when a friend needed help with some math to make some bass reflex enclosures. Later, I worked for a hifi store. The T/S stuff was introduced, and I heard some really horrible speakers, convincing me that Novak was right all along. In the '80s an engineer friend introduced to me to those little FE-103 speakers Radio Shack sold, and I played around with some open baffle designs matched to sub woofers, satellite/sub systems being the DIY rage back then. Now we're wanting to add some real speakers to our home theatre, and I'm looking at transmission lines as a possibility. We move our furniture around too often for room dependent speakers, so OB designs are out.

I've spent the last week reading so many web pages I'm totally lost! While I think I have the gist of it, the one thing I can't remember being mentioned is the importance of the overall (internal) volume of the box. The length relates to the cutoff, and the cross-section... some say it should be no bigger than the speaker, yet in many plans it appears that it is. Can someone help me out here?

planet10 · 26th February 2010, 12:18 AM

Usually an optimal TL will have xSection much larger than driver Sd. Keep in mind that there is the old and out-of-date Classic school of design, and the modern, much more accurate design methods that use Martin King's software or tables (Augspurger's software works too, but is not near as well developed)

What driver(s), amp, expectations?

dave

mightym · 26th February 2010, 01:33 AM

Have you looked at MJK's TL tables?

Check out the Quarterwave site, his tables are pretty much right on AFAIK.

Transmission Line Theory

You should find everything you need there.

Keriwena · 26th February 2010, 04:41 AM

For drivers, I've been looking at the Eminence Beta 12LTA. My amps are Haflers, two MK IIIs, and a more modern stereo 120. I'm not looking for an extremely wide bandwidth, it seems to me dynamics are more important for realism. I figure if I can get down to 100 Hz then crossing over to a sub will be no problem. Does a 12"x12"x34" box qualify as a "transmission line"?

planet10 · 26th February 2010, 06:35 AM

A quick look at teh spec and given you are only trying to hit 100 Hz, aperiodic or sealed probably makes more sense.

dave

Keriwena · 26th February 2010, 12:48 PM

Thanks, Dave. I suspect you're right. Still, the idea of a transmission line is kinda sexy.

25th February 2010, 11:54 PM	#1
Keriwena diyAudio Member Join Date: Feb 2010 Location: in half space	Help with TL design First, a bit about myself. I got into speaker design long, long ago when a friend needed help with some math to make some bass reflex enclosures. Later, I worked for a hifi store. The T/S stuff was introduced, and I heard some really horrible speakers, convincing me that Novak was right all along. In the '80s an engineer friend introduced to me to those little FE-103 speakers Radio Shack sold, and I played around with some open baffle designs matched to sub woofers, satellite/sub systems being the DIY rage back then. Now we're wanting to add some real speakers to our home theatre, and I'm looking at transmission lines as a possibility. We move our furniture around too often for room dependent speakers, so OB designs are out. I've spent the last week reading so many web pages I'm totally lost! While I think I have the gist of it, the one thing I can't remember being mentioned is the importance of the overall (internal) volume of the box. The length relates to the cutoff, and the cross-section... some say it should be no bigger than the speaker, yet in many plans it appears that it is. Can someone help me out here?

26th February 2010, 12:18 AM	#2
planet10 frugal-phile(tm) diyAudio Moderator Join Date: Oct 2001 Location: Victoria, BC, NA, Sol III Blog Entries: 4	Usually an optimal TL will have xSection much larger than driver Sd. Keep in mind that there is the old and out-of-date Classic school of design, and the modern, much more accurate design methods that use Martin King's software or tables (Augspurger's software works too, but is not near as well developed) What driver(s), amp, expectations? dave __________________ community sites t-linespeakers.org, frugal-horn.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA

26th February 2010, 06:35 AM	#5
planet10 frugal-phile(tm) diyAudio Moderator Join Date: Oct 2001 Location: Victoria, BC, NA, Sol III Blog Entries: 4	A quick look at teh spec and given you are only trying to hit 100 Hz, aperiodic or sealed probably makes more sense. dave __________________ community sites t-linespeakers.org, frugal-horn.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA

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26th February 2010, 01:33 AM	#3
mightym diyAudio Member Join Date: Feb 2008 Location: Checotah, Okrahoma former home of the Okra Fest	Have you looked at MJK's TL tables? Check out the Quarterwave site, his tables are pretty much right on AFAIK. Transmission Line Theory You should find everything you need there.

26th February 2010, 04:41 AM	#4
Keriwena diyAudio Member Join Date: Feb 2010 Location: in half space	For drivers, I've been looking at the Eminence Beta 12LTA. My amps are Haflers, two MK IIIs, and a more modern stereo 120. I'm not looking for an extremely wide bandwidth, it seems to me dynamics are more important for realism. I figure if I can get down to 100 Hz then crossing over to a sub will be no problem. Does a 12"x12"x34" box qualify as a "transmission line"?

26th February 2010, 12:48 PM	#6
Keriwena diyAudio Member Join Date: Feb 2010 Location: in half space	Thanks, Dave. I suspect you're right. Still, the idea of a transmission line is kinda sexy.

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