Speedster TMM

[Paul Carmody]

Re: Speedster TMM

Hello

I have just finished my Speedster :
[ATTACH=CONFIG]41534[/ATTACH][ATTACH=CONFIG]41535[/ATTACH]

Those are lust-inducing.

[nrg74]

Re: Speedster TMM

Patjazz,

Glad to hear that your speedsters are sounding good and looking great also. I'm about to cut some plywood and make a set of Speester TMM's. I still have some work to do to get ready for winter before I can get to my project. I'm sure the Speedster TMM is worth building, if the Speedster sounds good I'm sure the TMM will sound even better.

[patjazz]

Re: Speedster TMM

Hello

I have just finished my Speedster :

and they sound very well !

Now, i'm interested by the TMM MLTL version....

Is there any one building them ? I need to have some pictures of building, graphs (Paul ?) to compare with speedster (to have an idea of benefit...) before buying elements ( W4-1720 is difficult to find in France....).



Thank you.

[nrg74]

Re: Speedster TMM

Exarch, would you mind sharing your dimensions with me?
If you are in SE Michigan I could cut some boards for you...

[Exarch]

Re: Speedster TMM

Am I going to be the first to build a 3/4 birch version?

I've had the parts and a sketchup done for 3/4 baltic birch ready for a couple months now, but chronic back pain has kept me from starting. I can't see myself finishing this project for at least 3-6 months.

[Taran]

Re: Speedster TMM

No way to know. First in the clique of posters here maybe.

[nrg74]

Re: Speedster TMM

Am I going to be the first to build a 3/4 birch version?

[nrg74]

Re: Speedster TMM

I love this design! Ribbon, 2.5way, perfect. Thanks Paul, Paul and others in this community.

[Paul Carmody]

Re: Speedster TMM

I was looking at the crossover to try to get an idea of the efficiency gain from using 2 woofers, and noted the TMM has 19 ohms in series with the tweeter and the TM has 18 ohms. That doesn't seem like an increase, could you comment on efficiency and how that works. I really like the relative loudness of your Tarkus speakers with my amp & would like to get close to that. (If I ever figure out your email address I'll send you a picture.)

Don

Don,
Lots of stuff to address in your post... it pretty much warrants its own thread. Would you mind posting it in the main forum so we can address everything?

[Paul K.]

Re: Speedster TMM

I agree with you but I didn't want to make that decision for you to increase the baffle width.
Paul

Paul,
I think what i'm going to do for the 3/4" cabinet is simply increase the outer dimensions by 1/2" all around. (I'lll still keep the drivers and port locations relative to the inside of the cabinet, though). A 6.5" wide baffle is not going to sound any different than a 6" wide baffle.

I'll redraw the cabinet and post that up here soon.

[Paul Carmody]

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

Paul,
I think what i'm going to do for the 3/4" cabinet is simply increase the outer dimensions by 1/2" all around. (I'lll still keep the drivers and port locations relative to the inside of the cabinet, though). A 6.5" wide baffle is not going to sound any different than a 6" wide baffle.

I'll redraw the cabinet and post that up here soon.

[Sidi]

Re: Speedster TMM

You're not going to hit Tarkus levels of loud with a pair of four inch midwoofs. IMHO

[Exarch]

Re: Speedster TMM

I've sketched up a preliminary model of the speaker in 3/4". I plan on using baltic birch.



I added 0.25" to the 11.5" depth to account for interior bracing volume. The interior volume after displacements, interior height, and baffle width match the original specification.

I plan on filling the speaker with 10z of polyfil in the top 25" of the interior volume (from the 2nd brace from the bottom upwards)

I didn't want to move the tweeter any distance from the top of the baffle, so instead I kept the 'middle-of-the-woofers' to port distance the same by moving the port upwards by 1/2" (To account for the extra 1/2" of material)

Does this sound correct?

Thanks.

EDIT: I read Paul K.'s post completely wrong; I need to rework things slightly. I think using a 1/2" top piece is the only way to retain both the middle-of-woofers to top of the speaker internals distance, as well as the tweeter to top of baffle distance.

[matchless79]

Re: Speedster TMM

I was looking at the crossover to try to get an idea of the efficiency gain from using 2 woofers, and noted the TMM has 19 ohms in series with the tweeter and the TM has 18 ohms. That doesn't seem like an increase, could you comment on efficiency and how that works. I really like the relative loudness of your Tarkus speakers with my amp & would like to get close to that. (If I ever figure out your email address I'll send you a picture.)

Don

[Paul K.]

Re: Speedster TMM

You're essentially correct, but it's all 'splained quite clearly in the link to the writeup I did for Dennis Murphy's site that "djg" provided. Basically all tall, 2-way vented boxes are ML-TLs but unless they were specifically designed that way by incorporating the effects of the 1/4-wave resonant frequency from the internal height as well as finding the optimum location for the port, the end result will likely not be as good it could be and may actually be fairly deficient in a sense.
Paul

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)