Speedster TMM

[Paul Carmody]

Gentlemen,
This is the writeup for the Speedster TMM. All the necessary info is there, however, it's still rough around the edges. There are a few missing graphs, and I don't know when I'll have the time to re-create them, but I figure rather than just make people wait some more, I'd post what I have.

https://sites.google.com/site/undefinition/speedster-tmm

Let's call it a "Beta" writeup. Any input or questions you have about the project and its writeup, feel free to post in this thread, and I'll be glad to answer them. (As I've mentioned on my site recently, life's gotten kinda busy for me lately, so my email turnaround time is excruciatingly slow. Posts on this site, however, I can easily stop by and answer.)

[isaeagle4031]

Re: Speedster TMM

very cool Paul. I liked these a lot at indiyana

[Exarch]

Re: Speedster TMM

Excellent. I can finally put those four woofers I got on sale a while back to use. Thank you Paul. I was originally going to make a set of Speedsters and a set of Picollata's and sell one to a friend, but I really don't feel like making two more sets let alone one, pretty burnt out. :p

I'm a bit confused on the write-up. You mention it's a transmission line. I don't know anything about those other than they usually have angled passageways in the box, but you just mention a single round port. Is this speaker a transmission line, and if so, what makes it one? How would I add bracing in the cabinet without interferring with the enclosure's properties?

EDIT: I noticed that you labeled two inductors 'L3' in your schematic. Also, would 18 guage air core be fine for all the inductors?

[Sidi]

Re: Speedster TMM

Nice to see you took this somewhere :D

[djg]

Re: Speedster TMM

Excellent. I can finally put those four woofers I got on sale a while back to use. Thank you Paul. I was originally going to make a set of Speedsters and a set of Picollata's and sell one to a friend, but I really don't feel like making two more sets let alone one, pretty burnt out. :p

I'm a bit confused on the write-up. You mention it's a transmission line. I don't know anything about those other than they usually have angled passageways in the box, but you just mention a single round port. Is this speaker a transmission line, and if so, what makes it one? How would I add bracing in the cabinet without interferring with the enclosure's properties?

EDIT: I noticed that you labeled two inductors 'L3' in your schematic. Also, would 18 guage air core be fine for all the inductors?

https://www.philharmonicaudio.com/ML-TL.html

[randyohoh]

Re: Speedster TMM

noob questions here. Is the L3 to the far right of the schematic really L4? Is the woofer to the far right the bottom woofer? Sorry, I am clueless when it comes to cross over topology.

[Paul K.]

Re: Speedster TMM

You can see in the link provided by "djg" a detailed description of what an ML-TL is. I authored that writeup BTW for Dennis Murphy on his Philharmonic Audio site to accompany the ML-TL designs I did for his speakers. What you are remembering is a tapered TL, but there are several different configurations that are all TLs in some form or another, one of which is the ML-TL.
Paul

Excellent. I can finally put those four woofers I got on sale a while back to use. Thank you Paul. I was originally going to make a set of Speedsters and a set of Picollata's and sell one to a friend, but I really don't feel like making two more sets let alone one, pretty burnt out. :p

I'm a bit confused on the write-up. You mention it's a transmission line. I don't know anything about those other than they usually have angled passageways in the box, but you just mention a single round port. Is this speaker a transmission line, and if so, what makes it one? How would I add bracing in the cabinet without interferring with the enclosure's properties?

EDIT: I noticed that you labeled two inductors 'L3' in your schematic. Also, would 18 guage air core be fine for all the inductors?

[Paul K.]

Re: Speedster TMM

"Mr. Carmody", I just re-sent the email with all of the graphs you mentioned in your writeup not getting. If the graphs get eaten again by gmail, I can probably come up with some other way of getting them to you. Hint: If my resent email does contain all of the graphs, I suggest you both print it out and save it in another file that's not in your email account.
Paul

Edit: I noticed an error in Mr. Carmody's writeup regarding the cabinet's dimensions depending on what thickness the side walls are. If the side walls are 1/2" thick, the required internal width is 5" and the internal depth is 9". If the side walls are 3/4" thick, the internal width needs to be 4.5" and the internal depth is 10". For either side wall thickness, the internal height is 38". It's also assumed that the top and bottom will be 1/2" thick regardless.
Paul

[dst]

Re: Speedster TMM

Very nice design. Many thanks for undertaking it and posting it. there will no doubt be many builders.

[fastbike1]

Re: Speedster TMM

As long as your bracing doesn't substantially change the cross sectional area of the line, you should be OK.

. . How would I add bracing in the cabinet without interferring with the enclosure's properties?
...

[Paul Carmody]

Re: Speedster TMM

EDIT: I noticed that you labeled two inductors 'L3' in your schematic.

Good catch. Fixed.

Also, would 18 guage air core be fine for all the inductors?

Yup, that'd be just fine.

[Paul Carmody]

Re: Speedster TMM

"Mr. Carmody", I just resent the email with all of the graphs you mentioned in your writeup not getting. If the graphs get eaten again by gmail, I can probably come up with some other way of getting them to you. Hint: If my resent email does contain all of the graphs, I suggest you both print it out and save it in another file that's not in your email account.
Paul

Edit: I noticed an error in Mr. Carmody's writeup regarding the cabinet's dimensions depending on what thickness the side walls are. If the side walls are 1/2" thick, the required internal width is 5" and the internal depth is 9". If the side walls are 3/4" thick, the internal width needs to be 4.5" and the internal depth is 10". For either side wall thickness, the internal height is 38". It's also assumed that the top and bottom will be 1/2" thick regardless.
Paul

Got the email. Thanks, Paul. I'll add those in soon.
I fixed the dimensions for the 3/4" stock version. I'm going to go ahead and bump up the height 1/2" for that version, so the builder can use 3/4" all-around.

[Paul Carmody]

Re: Speedster TMM

I'm a bit confused on the write-up. You mention it's a transmission line. I don't know anything about those other than they usually have angled passageways in the box, but you just mention a single round port. Is this speaker a transmission line, and if so, what makes it one? How would I add bracing in the cabinet without interferring with the enclosure's properties?

You raise a good point. Not all transmission lines involve folding or angling innards. In fact, a standard ported box is a type of transmission line.

In this case, Paul K has designed a "1 piece" transmission line (whose length is long enough that it doesn't need folds), where the placement and density of the stuffing emulates the effect of a tapered transmission line.

(Correct me if I'm wrong, Paul)

[Paul K.]

Re: Speedster TMM

What I've found from modeling a bunch of TLs is that as long as consumed volumes don't total more than 5% of the gross volume, their effects are virtually insignificant and can be ignored.
Paul

As long as your bracing doesn't substantially change the cross sectional area of the line, you should be OK.

[Paul K.]

Re: Speedster TMM

When you make the changes for using 3/4" material all around, don't forget that the locations for the midpoint between the two woofers and the center of the port are based on internal distances from the top and bottom, respectively, not external dimensions.
Paul

Got the email. Thanks, Paul. I'll add those in soon.
I fixed the dimensions for the 3/4" stock version. I'm going to go ahead and bump up the height 1/2" for that version, so the builder can use 3/4" all-around.