New DIY MTM Towers designed by Dennis Murphy and Paul Kittinger

[crossedover]

Hello everyone,

I am new to speaker building and I need a little guidance on the cross-over. I purchase the shopping list provided on this first page of this thread and it had a .10mH air core that needs to be unwound to read .06. I do not have a way to unwind and measure it. Does anyone know about how many winds would need to be removed to get it within the 10% specification of .06mH?

In the notes below it says "XX coils" but I am not sure what that is suggesting.

Any help on this is appreciated.

Shawn

http://www.diyaudioandvideo.com/Calculator/AirCoreInductorDesigner/

 

[TLS Guy]

Hello everyone,

I am new to speaker building and I need a little guidance on the cross-over. I purchase the shopping list provided on this first page of this thread and it had a .10mH air core that needs to be unwound to read .06. I do not have a way to unwind and measure it. Does anyone know about how many winds would need to be removed to get it within the 10% specification of .06mH?

In the notes below it says "XX coils" but I am not sure what that is suggesting.

Any help on this is appreciated.

Shawn

To do what you want you need an inductance bridge. There are formulas to calculate turns, However the calculations turn out to be far from precise in the actual world. You always have to measure.

The real point is that a 0.06 air core choke is not expensive. Just order a couple and be done with it.

 

[spaeny10]

Thank you for the quick responses.

The real point is that a 0.06 air core choke is not expensive. Just order a couple and be done with it.

I am fine with this. Does .05 make a difference as I am not finding .06, just
a Jantzen Audio 0.05mH 18 AWG Air Core Inductor Crossover Coil from PE.

Also on the Madisound one it has a plastic core. Is this supposed to be removed before installation?

Thanks again.

 

[TLS Guy]

Thank you for the quick responses.



I am fine with this. Does .05 make a difference as I am not finding .06, just
a Jantzen Audio 0.05mH 18 AWG Air Core Inductor Crossover Coil from PE.

Also on the Madisound one it has a plastic core. Is this supposed to be removed before installation?

Thanks again.

No a plastic core will make no difference, since you can not magnetize plastic or induce currents in it.

 

[slipperybidness]

Thank you for the quick responses.



I am fine with this. Does .05 make a difference as I am not finding .06, just
a Jantzen Audio 0.05mH 18 AWG Air Core Inductor Crossover Coil from PE.

Also on the Madisound one it has a plastic core. Is this supposed to be removed before installation?

Thanks again.

http://www.mouser.com/Passive-Components/Inductors/_/N-5gb4?P=1z0wrerZ1z0wren&Keyword=.06+mH&FS=True

 

[Swerd]

I am new to speaker building and I need a little guidance on the cross-over. I purchase the shopping list provided on this first page of this thread and it had a .10mH air core that needs to be unwound to read .06. I do not have a way to unwind and measure it. Does anyone know about how many winds would need to be removed to get it within the 10% specification of .06mH?

In the notes below it says "XX coils" but I am not sure what that is suggesting.

Shawn

I've always meant to fix that, but since writing it, I've never had my hands on a 0.10 mH inductor coil.

I have an inexpensive LC meter, similar to this one. First, touch the meter's leads to each end of inductor to make sure it is 0.10 mH.

Unwind some wire and measure again. Keep count of how many coils you unwind. As long as the wire is not coiled, it doesn't contribute to the coil's inductance. Don't cut anything until you have unwound enough wire to read 0.06 mH on your meter.

Then cut off most of the excess (leave about 6-8") and scrape away about half an inch of the lacquer coating from the new end so you can solder on bare copper.

Edit: I just read what the others said about this. TLS Guy has given you good info. If you don't have an LC meter, just order two custom wound 0.06 mH coils. Two 0.05 mH coils would be acceptable substitutes.

And yes, an inductor wound on a plastic or wooden bobbin is considered an 'air coil' inductor. There is no need to remove the wire coil from the bobbin.

 

[spaeny10]

Thank you guys very much. I have ordered the .05s as well as an LC meter. This gives me an excuse to buy another tool.

I hope to have these speakers built and working by the end of the weekend.

 

[David LR]

Hello-

I purchased the parts for the dome tweeter version of this speaker some three years ago & am
finally (FINALLY !) on the home stretch after long periods of neglect. Life happens I guess.

Would someone, perhaps Swerd, please review the attached crossover pictures to see
if I've got it right ? I've assembled maybe 5 crossovers all together with years in between
so a little review would be helpful.

They aren't the neatest looking crossovers but I've seen far worse. Amazing how the
assembled crossover doesn't look like the neat little schematics, at least how I do it anyway !

As I said, these are dome tweeter version. As far as I know, I seem to be the only one building
with the dome tweeter.

Thanks for looking !

David

 

[Swerd]

Both woofer & tweeter boards look fine to me. I can read a value on only two of the three inductors, and the large 25 µF cap on the tweeter board. But I'll assume the rest of the parts are right. Did Meniscus supply the parts in their kit? If so, it looks good.

Let us know how they sound .

 

[David LR]

Thanks for the review, Swerd. Yes, ordered the kit from Meniscus, they got everything right. Hope to be
listening this weekend, I will certainly post my thoughts.


Thanks again.

 

[Researcher]

Thanks for the review, Swerd. Yes, ordered the kit from Meniscus, they got everything right. Hope to be
listening this weekend, I will certainly post my thoughts.


Thanks again.

I'm about ordering the ribbon version from meniscus this week, never ordered from them so I've been a bit hesitant; maybe because they don't offer free shipping and I'm not in US

Man thanks for posting pictures, did you order the bare bones or the full kit?

I'm also waiting for your impressions on how they sound.

 

[spaeny10]

Quick question about port placement. I have a fairly small room that will only allow me to pull the speakers out about 6-10 inches from the wall. Would I be better served to move the port to the front or even the bottom? Or can this even be done without effecting the speaker harmonics?

 

[Swerd]

Quick question about port placement. I have a fairly small room that will only allow me to pull the speakers out about 6-10 inches from the wall. Would I be better served to move the port to the front or even the bottom? Or can this even be done without effecting the speaker harmonics?

Your question has come up before. See posts #49, #51, and #53 in this thread. My advice:

1. Keep the port on the rear. Even with as little as 2-3" between the back of these speakers and the wall behind them, you'll not have a problem. See post #51 for more about that.
   
   
2. If you must, mount the port on the front of the cabinet in the exact opposite position as it was diagrammed on the back. Keep it centered and 3" above the interior cabinet floor (3¾" above the cabinet's exterior bottom assuming you build it from ¾" sheet lumber). I doubt if you'll hear port noise, especially if you use a flared port.
   
   
3. Don't bother with a bottom mounted port. See post #53 for the reason why.

 

[David LR]

I'm about ordering the ribbon version from meniscus this week, never ordered from them so I've been a bit hesitant; maybe because they don't offer free shipping and I'm not in US

Man thanks for posting pictures, did you order the bare bones or the full kit?

I'm also waiting for your impressions on how they sound.

Researcher-

I will gladly post my listening impressions as soon as available. I thought I would have these done a month ago, however, I'm always overestimating my work capacity while underestimating the amount of work remaining. I am making steady progress and am shooting for this coming weekend for a first listen. (Although I've said THAT before)

Regarding my order with Meniscus, I did order the full kit. I don't know about shipping outside the US but
I can say Meniscus is a thoroughly professional and competent organization. As you may know, they're more than just a supply house, they do lots of custom design work in-house, they really know their stuff.
You can usually call them up & talk straight to one of the top guys. Good luck with your build.

Dave

 

[AuralFission]

Hi everyone. This is a very informative thread, but I have a few questions about construction.

I'd like to veneer the cabinet and paint the outer front baffle. What's the best way to achieve this? Is the outer front baffle painted while it's glued on or is it better to do this before its glued on?

 

[Swerd]

I'd like to veneer the cabinet and paint the outer front baffle. What's the best way to achieve this? Is the outer front baffle painted while it's glued on or is it better to do this before its glued on?

With DIY wood work, there always seems to be more than one way to do things. I would cut the outer baffles to size, clamp them in place onto the cabinets, trim and round-over the edges, and cut the holes for the drivers.

Then I would remove them for several coats of paint. After all that, glue them on to the cabinets.

I assume you're after cabinets that look like the photo below.

 

[Researcher]

Researcher-

I will gladly post my listening impressions as soon as available. I thought I would have these done a month ago, however, I'm always overestimating my work capacity while underestimating the amount of work remaining.

Thanks for replying, take your time, I'll still waiting for a lenghty review...haha . I already ordered and received the kit from meniscus, very satisfied with their service.

I still need to buy the 3/4 MDF to start making some dust.

I'd like to veneer the cabinet and paint the outer front baffle. What's the best way to achieve this?

That is the same finish I have in mind, (look post #152 in this thread), it's not that hard as it's mostly time consuming but that's part of fun!. The thing is as these are big enclosures and the largest veneer I can find only measures 24" x 96" I'm affraid it's going to be tricky to cover the pair and make them look decently. Any advice would be greatly appreciated!.

 

[AuralFission]

That is the same finish I have in mind, (look post #152 in this thread), it's not that hard as it's mostly time consuming but that's part of fun!. The thing is as these are big enclosures and the largest veneer I can find only measures 24" x 96" I'm affraid it's going to be tricky to cover the pair and make them look decently. Any advice would be greatly appreciated!.

If I were you I would really look into getting a 48" x 96" sheet of veneer. That's what I'm using and it's perfect for both the floorstanders and the center channel.

Have you looked online? You can try veneersupplies.com or oakwoodveneer.com. I haven't bought from any of these suppliers since shipping to Hawaii would be too expensive, but if you're located in the continental US, I'm sure their rates are more reasonable.

 

[David LR]

Thanks for replying, take your time, I'll still waiting for a lenghty review...haha . I already ordered and received the kit from meniscus, very satisfied with their service.

Researcher- Way back when I had started a build log on these, so, in the interests of finishing
what I had started, I found the old thread & posted my review there. Hope it helps, good luck
on your build. You will like these speakers !

Dave

 

[AuralFission]

With DIY wood work, there always seems to be more than one way to do things. I would cut the outer baffles to size, clamp them in place onto the cabinets, trim and round-over the edges, and cut the holes for the drivers.

Then I would remove them for several coats of paint. After all that, glue them on to the cabinets.

Thanks for the tip Swerd. Based on your suggestion, I'm planning to veneer the front of the cabinet and then glue (no screws) the a prefinished outer front baffle directly on the veneer. I'm using wood backed veneer and will apply using clamps and cauls. Is there any concern for the veneer pulling apart when it has to bear the load of the outer front baffle (including drivers)? I'm not concerned about glue failure, but I am concerned about whether the veneer will separate from its wood backer.