Troy's Modula MTM Build Thread

[Troy R]

I sent Jon a PM about this but failed to realize he hasn't logged in for a month or so. So I might not get a response for a while... So could someone help me out on getting started on my Modula MTM build.

I’m trying to put together a budget BOM for the Modula MTM. I came across the one posted in this thread (post #13). But it seems to me that it is missing some resistors for R2 and/or R3. Since I’ve never built an xover I thought I better find out before I start ordering stuff.

So could someone please verify the attached BOM’s for me? (one is for extra BSC the other is not)

Your thoughts would be greatly appreciated!

Thanks!
Troy

Extra BSC BOM

No Extra BSC BOM

[cjd]

Quick request: can you not use copyrighted material as an avatar?

[ThomasW]

The choice of which BOM you use is dependent on the distance the loudspeakers will be placed from the walls....closer to the walls means less BSC is needed

There are 2 BOMs in the first post of the Modula MTM thread. These always up to date.

Post #13 is just a text copy of what was put in the spreadsheet in the previous post (#12). If it contains errors that's a function there being errors in the original poster's spreadsheet.

It's physically impossible for us to check everyone's posts for errors.

So.....

Alway cross reference any independently created BOM against the original contained in the first post in the thread. If there are differences use the BOM in Jon's initial post.

[Troy R]

The front baffle of my speakers will be 2 to 2.5 feet from the wall behind them and 6-8 feet from any side walls. Should I use more BSC or not?

I know that Jon has posted a BOM in his build thread (that is where I started), but his list is with more expensive parts than I want to spend. Since I am a noob, I have no idea what parts can be swapped for what (other than just matching values) I was hoping someone could verify that what I've selected is ok and matches what Jon has intended.

Thanks.

[ThomasW]

Use the version with more BSC.

[Troy R]

Thank you, Thomas!

I see you edited your post (I saw the original and was confused). So my selected values for the resistors in R2 and R3 are correct?

[ThomasW]

If you want to lower the cost even more subsitute the surplus GE poly caps from Madisound where ever possible. The making of C5/C6 with the GE 5mfd poly is a good place to save

http://www.madisound.com/catalog/index.php?cPath=356_5_9

R2= 4 ohm and R3= 6 ohm

[Troy R]

If you want to lower the cost even more subsitute the surplus GE poly caps from Madisound where ever possible. The making of C5/C6 with the GE 5mfd poly is a good place to save

http://www.madisound.com/catalog/index.php?cPath=356_5_9

R2= 4 ohm and R3= 6 ohm

I saw those, I went with the Solen since the rest of the caps were either Dayton or Solen. That and I can't quite get myself to go that cheap. :W

Thanks a LOT for the help. Time to make my Christmas list. :T

[ThomasW]

I saw those, I went with the Solen since the rest of the caps were either Dayton or Solen. That and I can't quite get myself to go that cheap.

It's not being 'cheap' about using the surplus GE poly caps. I use them and they're certainly as good as either the regular Solen or Dayton caps.

[Troy R]

I guess I will get my audiophile nose out of the sky and take a look at them again...

Thanks again!

[Dennis H]

The only catch with the GEs is you have to solder a bunch of little ones together to make a big one.

[Troy R]

So I'm still looking at various crossover BOM's and I was wondering if the Jantzen 15 AWG Air Core Inductors would be sufficient replacements for all of the 14 AWG Perfect Layer Inductors that Jon calls for? Would they be a better choice than the 16 AWG sidewinders from Madisound?

Also, since I am not using the Audiocap Theta's is it ok to just buy the Dayton DMPC-15 15uF 250V Polypropylene Capacitor and Dayton DMPC-18 18uF 250V Polypropylene Capacitor instead of grouping caps together to make the values?

Sorry again for the noob questions...

[---k---]

Jon is pretty fussy with his component choices. He agonizes over very small differences. The parts he has chosen is for a reason.

The Jantzen 15ga aircore inductors have a higher DCR value. Changing these will definitely have an impact on the frequency response. I wouldn't recommend this change, unless you can model the difference and are willing to accept the lesser results.

Changing the cap types is okay as long as you come up with the same values. There is a lot of debate over whether different caps have different sounds. Jon is obviously believes that they do. I used all Dayton's in my project and am happy.

If you're tight on money, you might want to consider Jon's NatP design instead. It uses the same drivers, but was designed to be a simpler and more inexpensive crossover design. It has been very well received. See Jon's Mission Accomplished thread for a BOM.

[Troy R]

Thanks for the response, Ryan.

I have chosen the Modula MTM because I had already purchased the Seas 27TDFC tweeter for a modula MT project that never happend. I wasn't aware of a Nat P design using the Seas tweeter...

So if I were to alter the xover it would be fine to use different caps but I should probably stick with the perfect lay inductors?

[---k---]

Ooops. My mistake. The NatP uses the same RS180 drivers, but uses the RS28 tweeter. According to the first page there isn't a Seas version. I did a quick search and Thomas said in this post: http://htguide.com/forum/showpost.ph...&postcount=426

The sticky designs are 'frozen' = no changes. If you want to use a Seas tweeter build the Modula MTM.

So it looks like if you want to keep your Seas tweeter, you're going to want to stick with the ModulaMTM. Sorry about that.

So if I were to alter the xover it would be fine to use different caps but I should probably stick with the perfect lay inductors?

Fine with me! Fine with Jon? Likely fine, but not enthusiastic about it. Fine with You? ?? You'll have to be the judge of that. Take a look at the NatP thread. I noticed when I was checking on the tweeter that questions about Iron Core was addressed on the first page.

[---k---]

Thomas,
Just curious, what was the reasoning behind using the Seas in the ModulaMTM and the RS28 in the NatP? Was it just that the RS28 wasn't available at the time of the Modula build?

[ThomasW]

Thomas,
Just curious, what was the reasoning behind using the Seas in the ModulaMTM and the RS28 in the NatP? Was it just that the RS28 wasn't available at the time of the Modula build?

Correct, the Modula was the first design posted so it used the Seas. People wanted a cheaper MTM so the NatP was created. At that time the RS28 became available so Jon was curious about using it.

[Troy R]

Ooops. My mistake. The NatP uses the same RS180 drivers, but uses the RS28 tweeter. According to the first page there isn't a Seas version. I did a quick search and Thomas said in this post: http://htguide.com/forum/showpost.ph...&postcount=426

So it looks like if you want to keep your Seas tweeter, you're going to want to stick with the ModulaMTM. Sorry about that.

Fine with me! Fine with Jon? Likely fine, but not enthusiastic about it. Fine with You? ?? You'll have to be the judge of that. Take a look at the NatP thread. I noticed when I was checking on the tweeter that questions about Iron Core was addressed on the first page.

No problem, you didn't know I had the Seas tweeter. :W

As long as the changes aren't night and day (real night and day, not audiophile night and day :W ) then I don't care about using less expensive parts. I'm just looking to get the most bang for my buck. I just didn't want to sink a bunch of money into this project. The Modula MT project started out of curiosity to build my own speakers. I had no use for them at the time. Now that my stereo is being moved to a bigger room and I was forced to sell my old mains I figured I better just build the MTM. I also plan on using them for music without a sub so the bigger speaker is “needed”

I also don't know how long I will be using them... Could be 6 months to a year, could be 4 or 5 years, who knows... So keeping the price low was a concern considering the uncertainty…

Thanks for the help!

[Troy R]

I've been listening to the Modula MTM's for a few months now and I am very pleased. I went with a budget xover so I may not be getting the best results possible, but they still sound very nice for the price.

My only "complaint" is that the top end doesn't seem to be as detailed as what I'm used to. I had Dynaudio 1.3mkII speakers before building the MTM's and I would like to get a little more "sparkle" on the top end, similar to the Dyn's. Looking at Jon's design thread it seems that the MTM's are a lot flatter across the frequency range. (see the link to Stereophile's measurements of the Dynaudio's below)

http://www.stereophile.com/standloudspeakers/333/index4.html

So my question is can I alter the XO slightly to get a bit more sparkle at the top end of the MTM's? I have no way of measuring the response, I would just be listening to what I prefered. Any help would be greatly appreciated! Thanks!

[ThomasW]

You wouldn't be able to get the Dynaudio 10kHz centered peak by changing the output from the tweeter. Reason being changing the tweeters output level will impact everything above the crossover point which is 1.4kHz.

You best bet would be to use EQ to dial in a little treble boost.

[Troy R]

Thanks for the info. Makes sense.

Is there something that I could change that would raise the output of the entire tweeter spectrum by a little bit?

[ThomasW]

You'd need to change values of the resistors in the L-pad.

But instead I again suggest you simply boost the treble if you have EQ in your receiver or amp.

[Mazeroth]

Thomas,

Could he do the opposite of a BSC filter and use an in-line paralleled cap+resistor to increase the top end? Only problem would be figuring out the values to use.

Troy, I wouldn't mind hearing your Modulas and can bring over my chest of x-over parts if you want to experiment. Shoot me a PM if you want with your phone number.

[ThomasW]

Troy, I wouldn't mind hearing your Modulas and can bring over my chest of x-over parts if you want to experiment.

That's a great idea.... :T

[Troy R]

Troy, I wouldn't mind hearing your Modulas and can bring over my chest of x-over parts if you want to experiment. Shoot me a PM if you want with your phone number.

Thanks Maz, PM on the way.

[treytexag]

Troy, after you finish tweaking, please post your findings. I'm getting ready to build the Modula MTM's, so I'm very interested in your changes, if any, from playing with the xover.

Thanks