Building the RS150 MTM designed by cjd, some questions

[Xander]

Hi,

I'm pretty new to this forum, but have been very much into DIY audio for a couple years. I am also into car audio and pro audio, as I setup concerts and run sound once or twice a week at my campus. A lot of the advanced stuff is still new to me (like crossover and advanced box design), but I love to learn anything I can, and appreciate all your help.

I'm planning on building the RS150 MTM designed by cjd

http://www.eldamar.net/audio/rs150mtm/

I have half a sheet of 3/4 MDF left from a sub enclosure build and will be ordering everything else in the next few days, hopefully with some help from you guys.

I am trying to decide between the different tweeter designs. I don't have a lot of experience listening to different tweeters, but I have installed Seas neo aluminums in my car, and love the sound of them. Very light, crisp, full, and not sibilant at all (with a good source...) Any suggestions on which tweeter? Shielding is not a factor, as I have a projector screen. (Or possibly an LCD after moving into a new place next year with some friends)

I will be going sealed, as I would rather have more power handling than bass response. I'll be crossing over around 80hz to my sub (12" SAE1240 sealed off 300 watts with a modified amp for extended LF response, my dad and I built it)

Also, what is suggested for the caps? I am on a budget, as I am still in college and trying to save some money. But I want to make this a good investment, so I guess I'm looking for the middle ground.

Thanks for any help/advice, I can't wait to build this thing.

EDIT: oh yeah, and if it matters, I am using a Marantz SR4001 receiver and Crown XLS202D amps to power the fronts and center. This is the best setup I have had so far and I love it. My current mains are KLH 3-ways...I replaced the tweeters and sealed back mids with some Goldwood replacements and the crossover with the Dayton 3-way (crossover points are compatible) after they got damaged. I know, ghetto :roll:

[cjd]

I'd snag the Seas TBFC/G and build the generic crossover option.

They're responsive to box stuffing/wall treatment.

[technimac]

...what is suggested for the caps? I am on a budget, as I am still in college and trying to save some money. But I want to make this a good investment, so I guess I'm looking for the middle ground....

This would work:

Mad has these 5 mfd GE caps @$.75 ea:

http://www.madisound.com/catalog/product_info.php?cPath=404_5_9&products_id=312

and these 10 mfd Tyee caps @$.90 ea:

http://www.madisound.com/catalog/product_info.php?cPath=404_5_12&products_id=1463

...that you can combine for CT1(two GE 5 mfd), CM1 (three Tyee 10 mfd & one GE 5 mfd).

For CMZ, combine one Tyee 10 mfd with three of these GE .68 mfd @ $.30 ea:

http://www.madisound.com/catalog/product_info.php?cPath=404_5_9&products_id=308

for a total of ~12 mfd.

For a grand total of $6.75, this is about as "value priced" as it gets, using polypropylene caps.

~Bruce

[cjd]

Those're good caps too. Definitely good caps.

C

[---k---]

Hi,
I'm planning on building the RS150 MTM designed by cjd

http://www.eldamar.net/audio/rs150mtm/

I've heard these a couple of times at my place and CJD's. You're going to enjoy these. I don't think they get as much attention as they deserve.

CJD has Madisound surplus GE caps in his big 3-ways, and they sound fantastic to me. I have all Dayton in my Khanspires, and I think they sound great. Better caps may sound just slightly better, but there is nothing wrong with the Daytons. I believe that the Daytons are the same as the Benics from Madisound.

[Sefferdog]

I've heard these a couple of times at my place and CJD's. You're going to enjoy these. I don't think they get as much attention as they deserve.

I agree. I built these and they are a serious bang for the buck design. Sound great, easy to build, and inexpensive. What's not to like? :T

[Xander]

Thanks everyone, I appreciate it. That's a great deal on all those caps, I'm buying enough parts to build 3 crossovers now so I have them when I want to build the fronts.

I'm not 100% sure where these speakers will be placed permanently since I'll be moving, but I'm guessing on top of a wide short TV stand a foot or two from the wall. Will I be good with 18 gauge all around in the inductors?

[---k---]

Bill of Materials

* (2) RS150-S8
* (1) Seas 27TDFC, 27TDFC/TV, or 27TBFC/G
* (1) 10uF capacitor
* (1) 12uF capacitor
* (1) 35uF capacitor
* (1) 18ga .22mH inductor
* (1) 18ga .40mH inductor
* (1) 18ga 1.0mH inductor
* (1) 2ohm resistor (10W+)
* (1) 6ohm resistor (10W+)

yep.

[Xander]

Well, I was just wondering if there was an adjustment to be done with regards to BSC. I'm assuming these gauges of inductors are for a design with reduced BSC? 3 dB maybe?

Sorry to be a pain, I just haven't built a real speaker before, just subs. So I want to do this right the first time. You have no idea how excited I am to do it, I just have to keep myself in check and not rush it and screw something up.

[cjd]

It should be good anywhere near boundary. They'll go a little lean out in an open room. If you want a little more oomph on the bottom end go with lower DCR on the inductors to pick up half a dB to a dB.

C

[Xander]

This would work:

Mad has these 5 mfd GE caps @$.75 ea:

http://www.madisound.com/catalog/product_info.php?cPath=404_5_9&products_id=312

and these 10 mfd Tyee caps @$.90 ea:

http://www.madisound.com/catalog/product_info.php?cPath=404_5_12&products_id=1463

...that you can combine for CT1(two GE 5 mfd), CM1 (three Tyee 10 mfd & one GE 5 mfd).

For CMZ, combine one Tyee 10 mfd with three of these GE .68 mfd @ $.30 ea:

http://www.madisound.com/catalog/product_info.php?cPath=404_5_9&products_id=308

for a total of ~12 mfd.

For a grand total of $6.75, this is about as "value priced" as it gets, using polypropylene caps.

~Bruce

I am ready to checkout at Madisound and PE, and just noticed something. You are combining two 5uF caps to make the 10uF cap. Is this to increase the power handling? Because I did notice the voltage rating on the 10uF caps is only 100 volts. Otherwise I don't see why you wouldn't just use one of the 10uF caps there.

[technimac]

I am ready to checkout at Madisound and PE, and just noticed something. You are combining two 5uF caps to make the 10uF cap. Is this to increase the power handling? Because I did notice the voltage rating on the 10uF caps is only 100 volts. Otherwise I don't see why you wouldn't just use one of the 10uF caps there.

I don't think it matters, but because that 10uF value is "in-line" with the tweeter, I thought it might be a good place to parallel two 5uF GE caps.

~Bruce

[cjd]

Won't matter. The GE caps are high quality, better than the Bennics, and I think a step up from the Solens. Which is still being picky about the whole thing. Particularly when you consider this design is already "compromised" to be more flexible to placement differences, etc. such subtle cap changes are likely to be orders of magnitude smaller on the discernability scale than stepping into a more "no holds barred" crossover that's less flexible and forgiving.

C

[ThomasW]

Jon's compared the standard Solen caps against the GEs, he says they sound the same.

The advantage of making larger value caps using multiple smaller ones is the ESR (equivalent series resistance) is lower with the clusters. That's a good thing Martha.. :T

The downside to cluster caps is their size, and the labor involved making them.

[Brian Bunge]

The downside to cluster caps is their size, and the labor involved making them.

You ain't kiddin'!

[cjd]

my fingers still hurt...

[Xander]

Sweet, thanks again everyone. I have 3-4 weeks of nothing much to do over winter break between semesters, this is my only project. So I don't mind spending some time soldering. I don't have many friends to hang out with back home :P

Off I go to checkout at PE and Madisound!

........

Well, I got all my parts ordered. I ordered enough crossover parts to make 3 of them right off the bat, just in case some of the parts go out of stock. Hopefully they don't stop making those tweeters or the RS150s before I have the money to make my matching mains...

I also almost blew a bunch of money on banana plugs and spade connectors. But I resisted. Maybe next summer when I have more money...