TARGAS - RS150 and Tangband 28-537 TM

[donradick]

After my last budget build, I had a bit more confidence, and wanted to tackle a slightly more expensive design with low distortion. I wanted about a .5 cube bookshelf system for bedroom use, and quickly settled on the RS150 for bass-mid duties. For some reason I chose the RS150-4, thinking it would have better efficiency - still learning about some of this stuff. I asked around for the best $25-30 tweeter, and guys kept responding with "well this one's a bit better". I talked myself into the Tangband 28-537SH tweeter. I spent $45 on it - but in retrospect, I probably should have gone with the venerable RS28 at that price. Still, the Tangband is a very nice dome tweeter - no regrets.

[donradick]

Re: TARGAS - RS150 and Tangband 28-537 TM

The box was 1/2 inch Lowes ply - "Accuply", if I remember correctly. Nice stuff, Layers all the same thickness, no voids, good density. Lots better than the birch or oak faced ply that I have used on previous builds. Edges cut very clean with my 60 tooth carbide tipped blade. Glued 1/2 inch by 1 inch runners on the inside front to attach the removable baffle. Baffles were just 2 layers of the 1/2 inch ply - perfect thickness for this build. I found the great program "Cutlist" and laid out a perfect pattern on one 2x4 foot plywood sheet. Too bad I didn't "quite" follow it, and needed extra. As usual, "live and learn".

[donradick]

Re: TARGAS - RS150 and Tangband 28-537 TM

In any case, the crossover came together pretty quickly in PCD - a standard 2nd order LR on the woofer, standard 3rd order on the tweeter. For a while I tried listening to that, and found that for rock and folk, it sounded fine, but massed vocals on Mozart's Requiem sounded a bit muddy, so I added a LCR trap for the woofer breakup. After listening a few weeks, ordered some mills resistors for the tweeter. Not sure at all it really made a difference, but they are great components. These are measured responses which were reimported into PCD, so the level is a bit low.

OCT 2012 update/
Um, that was a good try, but I messed up the BSC, the correct crossover is just below. Read more for the details...
Big change is that I went 3rd order on the woofer, and so did not need the trap for the breakup.

[[email protected]]

Re: TARGAS - RS150 and Tangband 28-537 TM

sweet build. are they ported?

[Wolf]

Re: TARGAS - RS150 and Tangband 28-537 TM

Normally out-of-bandwidth resonance notches are easier and better with an LCR or even LC shunt. Something like 0.025-0.1mH and 5-20uF is the ballpark range. So- it would be cheaper with those components too.

Just a thought,
Wolf

[donradick]

Re: TARGAS - RS150 and Tangband 28-537 TM

I spent quite a while tuning the trap, and now finally understand that LC sets the trap frequency, and the resistor sets the depth. Regardless, I did a number of measurements with various values to suppress the breakup as completely as possible. Not really any better than anyone else, but I enjoyed the effort, and I'm satisfied that I did the best I could with that topology.

[donradick]

Re: TARGAS - RS150 and Tangband 28-537 TM

I also took my first distortion measurements. the guys said that the bass distortion looked funny, but the tweeter distortion is very low.

[donradick]

Re: TARGAS - RS150 and Tangband 28-537 TM

I also wanted to up the quality of my crossover construction, and picked up some euro style terminal blocks from Rat Shack. Routed all the leads to the underside, and connected it all up. Not very "clean" underneath, but hey, maybe next time. I found that the crossover fit perfectly under the foam "ribs", so I added some press on felt pads on the bottom and called it done.

[donradick]

Re: TARGAS - RS150 and Tangband 28-537 TM

This was also my first attempt at veneering. I chose quarter-sawn maple - I just couldn't justify the price for curly maple. Thanks to "my man" LouC, I went with odorless TitanDX contact cement. Wow - great stuff. Trimming the veneer was really not that hard, but I did experience what "tear-out" means. Oh well, still looks great and I am very happy with the final product. Finished the sides and top with clear Deft lacquer, and the baffle with rattle-can oiled bronze. The back is plain black satin.

[Wolf]

Re: TARGAS - RS150 and Tangband 28-537 TM

Minus the screws on the baffle- I really like the look of these too!
Funny how you offset the port to accomodate your bracing. ;)
That is a great tweeter.
Later,
Wolf

[donradick]

Re: TARGAS - RS150 and Tangband 28-537 TM

Final measured response is +- 2dB from 50 to 20K, with a measured 27dB reverse null. They sound beautiful, with great bass, wonderful mid range clarity, and crystal clear highs. You can hear the background singers take a breath.

Here is the measured reverse null - about 30dB - woohoo!:


Here is the measured FR with close miked woofer and port output:

[donradick]

Re: TARGAS - RS150 and Tangband 28-537 TM

Once again, guys - thanks for all your support and technical assistance. Much appreciated - I am exceeding what I ever thought I could accomplish.

[donradick]

Re: TARGAS - RS150 and Tangband 28-537 TM

sweet build. are they ported?

Thanks Arlis - somehow I forgot to save the Unibox model. Here's the Response Modeler box part. Ported - 2 inch about 6 inches long. Predicted F3 of 46 Hz:

[LouC]

Re: TARGAS - RS150 and Tangband 28-537 TM

This was also my first attempt at veneering. I chose quarter-sawn maple - I just couldn't justify the price for curly maple. Thanks to "my man" LouC, I went with odorless TitanDX contact cement. Wow - great stuff. Trimming the veneer was really not that hard, but I did experience what "tear-out" means. Oh well, still looks great and I am very happy with the final product. Finished the sides and top with clear Deft lacquer, and the baffle with rattle-can oiled bronze. The back is plain black satin.

Well whatever you "tore out" must be on the sides you didn't show us!;)
I think you did the right finish, maple is very hard to stain consistently. The Deft is pretty bullet proof too. Now you won't be afraid of veneer no more!
(I think it's easier, quicker and competitive with painting.) Look nice from here.

[donradick]

Re: TARGAS - RS150 and Tangband 28-537 TM

Normally out-of-bandwidth resonance notches are easier and better with an LCR or even LC shunt. Something like 0.025-0.1mH and 5-20uF is the ballpark range. So- it would be cheaper with those components too.

Just a thought,
Wolf

Oh [email protected]! I did it wrong?
I think PCD calls that a parallel LCR, and it's what most guys use for the RS breakup. I value your experience highly - should I have used a series LCR trap?