Otica h-frame MTM questions for Danny and Ebag4 plus other stuff

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flavo

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Hi all. I'm about to hit the go key on an Otica MTM and a double H-frame build.
The easy part of my questions will be about the build. I'm a little smitten with the way ebag4's build came out and plan on emulating (hopefully not too poorly)  to a certain extent his build.  I have seen specific dimensions for the H-frames but not the Otica MTM so I'm not sure how they fit together. Going off of random photos I can get off of the interwebs though. It appears they have different depths.
I plan on buying the flat pack for the MTM and building my own H-frame

The flat pack appears to be hanging off of the back of the H-frame.

Assuming this is the case, That would mean either the the MTM was cut down or the H-frame was added to in depth, and also height as the woofers are both facing forward.
Is adding to the depth an issue or should the mtm be cut down?

Also it appears that ebag4 added a 1/2" thickness to the h-frame for his speaker grills. Was this also accounted for and the h-frames are a total of 1" wider now?







Next big questions are about my room and system.
Luckily I am only 5'8". The ceiling height in this space is only 6'4" is in the highest spot. Am I going to have unwanted issues putting these speakers in here?

And the system. Keithh mentioned his passive being an issue in this chain.
I'm not very knowledgeable about what will and wont work. I'm putting together a better system then I had and I just want everything to work. I currently have a 3.5 watt 2a3 mono block amp.
http://www.triodelab.com/2a3-set-mono-b-locks/
and plan on adding a LDR  passive pre. Either a Tortuga or Truth. Do you foresee any issues with this? Maybe I should start a separate thread else where on building my components  other then the speakers?

I really appreciate the help and look forward to your feedback.
Mike










« Last Edit: 12 Jan 2018, 02:26 am by flavo »

2bigears

 :D nice build .   Those should sound unreal.  Would love to hear those indeed. 
       Your room looks good for sound. A few panels and corner treatments ,  whoa !!
     :D

Captainhemo

Hey Mike
If you  use a top  plate on the  H-frames  like our  overhanging  ones (17:" deep),  the  base we ship with the  MTM flat packs will be almost  flush,, it shouldn't overhang at all.   
LMK if you  are  going to want some MTm's  as I'm doing some  cutting  within the next  couple weeks., might still be able to get some of those inthe   "q"   

Danny can advise yo u better  on   the height of the room....  I think  you'd ideallly want   some additonal  height but not sure it  will be a  deal breaker. Adding  some diffusion on your  ceiling myay  be a big help....
How big is the room aside from the height ?  The other  thing is  that  3.5  watts  is not  a  ton of power witha  93 - 93.5 db speaker... at what  SPL's do you  tend to   listen  to  your  tunes at ?

jay

Danny Richie

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The good thing about an open baffle design is that the response will cancel at 90 degrees off axis and minimize some of the room interactions. This is also true in the upward plane. So they should work as well or better than a typical design in that regard.

flavo

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Hey Mike
If you  use a top  plate on the  H-frames  like our  overhanging  ones (17:" deep),  the  base we ship with the  MTM flat packs will be almost  flush,, it shouldn't overhang at all.   
LMK if you  are  going to want some MTm's  as I'm doing some  cutting  within the next  couple weeks., might still be able to get some of those inthe   "q"   

Danny can advise yo u better  on   the height of the room....  I think  you'd ideallly want   some additonal  height but not sure it  will be a  deal breaker. Adding  some diffusion on your  ceiling myay  be a big help....
How big is the room aside from the height ?  The other  thing is  that  3.5  watts  is not  a  ton of power witha  93 - 93.5 db speaker... at what  SPL's do you  tend to   listen  to  your  tunes at ?

jay

Pretty please get me an MTM cut for the Otica!

I can't speak on SPLs as I wouldn't know how to state it.  However, I don't typically listen all that loud but sometimes do. So I guess we'll see how they perform. I was about to order a chip amp board anyway that will have plenty of power. I can play with that and see what I think.

The room is 12x25 I think, with the other 1/2 of the room used as my office.  I've got to check again. Am very willing to play with room treatments.

I plan on building the h-frame  with no overhang. Much like the way Ebag4 did.
I'm sure he or Danny will see this thread before long and can likely answer.  But I'm trying to find out if the h-frame should get stretched to meet these measurements. Depth wise to meet the 17" long mtm base and width wise as Ed appears to have made his sides and tops 1.5" plus an additional .5" for the speaker frame stops.

flavo

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I just sent an email to Keith to see if he could be of any help on the passive preamp problem.
I was hoping to go Passive with this set up as well.
What is the recommended hook up path for these?

Source>dac>pre>amp and then RCA splitter or run to the 370s with high level/speaker cable?
If it matters, I plan on putting together 3255 chip amp. It is configured for 8ohm.
http://www.audiocircle.com/index.php?topic=152869.0
Thanks everyone.

Danny Richie

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I just measured the whole length of the long wing on my NX-Otica and only get 15.5". That's not front to back length. That length would be a little shorter.

The depth of the standard H frame is 14". So increasing it a little over a half of an inch each direction is not a problem.

Captainhemo

I just measured the whole length of the long wing on my NX-Otica and only get 15.5". That's not front to back length. That length would be a little shorter.

The depth of the standard H frame is 14". So increasing it a little over a half of an inch each direction is not a problem.

Well, the Otica MTM base is  aprox  16.25" so  you'd need to  extend the  cabinet  just over an  inch  each way in terms of depth

If you  are veneering  the h-frmes  the flush nouints will be no issue... if you are planning on painting, prepare for   some serious work to deal wiith that  seam  down each side  and   around the front  / rear corners.  They are not fun to deal.  This  piano black pair took a ton of work and  numerous coats of epoxy/block sanding



Even if you veneer, do a  good job on those seams  and then seal them up  with something.
the seams   are primarily why  we  try and get  guys to  go with the overhainging tops, they turn that seam into a transition and  "you" never have to worry about them

jay

ebag4

Hi all. I'm about to hit the go key on an Otica MTM and a double H-frame build.
The easy part of my questions will be about the build. I'm a little smitten with the way ebag4's build came out and plan on emulating (hopefully not too poorly)  to a certain extent his build.  I have seen specific dimensions for the H-frames but not the Otica MTM so I'm not sure how they fit together. Going off of random photos I can get off of the interwebs though. It appears they have different depths.
I plan on buying the flat pack for the MTM and building my own H-frame

The flat pack appears to be hanging off of the back of the H-frame.

Assuming this is the case, That would mean either the the MTM was cut down or the H-frame was added to in depth, and also height as the woofers are both facing forward.
Is adding to the depth an issue or should the mtm be cut down?

Also it appears that ebag4 added a 1/2" thickness to the h-frame for his speaker grills. Was this also accounted for and the h-frames are a total of 1" wider now?

Hi Mike, here's what I did.  The kit I got from Jay was one of his beta layouts, it came with the wings and baffle, no base.  The large wing is 15", I built the base to reflect the footprint of the baffle and large wing so my top half is 15 3/4" deep.  I made the H frame a little deeper than normal, Danny told me that the deeper the front and rear sections, the lower the top frequency the sub can reproduce, this has not been an issue with the Otica.  The overall depth of my sub is 15 3/4" so I added about an inch in each direction.

With regard to the grills, they are actually built on a 3/4" frame, they are inset to the H frame 3/8" and protrude the front by 3/8".  This allowed me to rabbet out the top of the grill so it could overlap the middle section and match up to the 3/8" overlap of the MTM.

Hope that helps!

Best of luck with the build!
Ed

flavo

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If you  are veneering  the h-frmes  the flush nouints will be no issue... if you are planning on painting, prepare for   some serious work to deal wiith that  seam  down each side  and   around the front  / rear corners.  They are not fun to deal.  This  piano black pair took a ton of work and  numerous coats of epoxy/block sanding


I definitely have more experience with veneer then I do painting. I worked in a cabinet shop for quite a while so it all seems simple in my head. But the more I think of it, I realize I don't have a spray booth or the Catalyst system to go with it that the guys there were using.
If I did paint i'd be going with a matte finish which would help a bunch I'm sure. You've certainly got me a bit scared (educated) but not really deterred. haha. Worst case, I veneer. I like a wood too.

Hi Mike, here's what I did.  The kit I got from Jay was one of his beta layouts, it came with the wings and baffle, no base.  The large wing is 15", I built the base to reflect the footprint of the baffle and large wing so my top half is 15 3/4" deep.

With regard to the grills, they are actually built on a 3/4" frame, they are inset to the H frame 3/8" and protrude the front by 3/8".  This allowed me to rabbet out the top of the grill so it could overlap the middle section and match up to the 3/8" overlap of the MTM.

Wonderful. It's a beautiful build you did and I'm still trying to figure out that bottom portion of the MTM you did by hand with multiple angles. Beautiful job.  Thank you Ed

mlundy57

Mike,

The best thing I've found for sealing and taming MDF seams is West System epoxy (105 Resin and hardener of choice). Two coats. Apply one, sand it back, apply the second then sand that one back also. Finally scuff sand with 100 grit before applying the veneer.

Mike

Captainhemo

Mike (flavo),    wasn't meant to scare you  !!  Just  wanted  to let you  know to be prepared to deal with  the seams involved with flush   tops.

jay

flavo

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Mike,

The best thing I've found for sealing and taming MDF seams is West System epoxy (105 Resin and hardener of choice). Two coats. Apply one, sand it back, apply the second then sand that one back also. Finally scuff sand with 100 grit before applying the veneer.

Mike

Excellent advice, thank you. I'll likely pick some up.
Would the process be different or more difficult if I was going to a low gloss or matte paint?

flavo

  • Jr. Member
  • Posts: 132
Mike (flavo),    wasn't meant to scare you  !!  Just  wanted  to let you  know to be prepared to deal with  the seams involved with flush   tops.

jay

Not at all Jay. I want to be educated going into this and appreciated the advice. The more I think about it, the more likely I am to go with veneer just for the look alone. And if paint is a PITB. That just makes the decision that much easier.

mlundy57

Excellent advice, thank you. I'll likely pick some up.
Would the process be different or more difficult if I was going to a low gloss or matte paint?

No different regardless of how you finish them. The idea is to seal and stabilize the seams so they don’t show throught the finish down the road

Mike

gregfisk

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No different regardless of how you finish them. The idea is to seal and stabilize the seams so they don’t show throught the finish down the road

Mike

Mike, do you use the fast hardener or the slow? And, what kind of shelf life does this have?

Thanks

mlundy57

Mike, do you use the fast hardener or the slow? And, what kind of shelf life does this have?

Thanks

Greg,

I have used the slow hardener but the fast would work also. I'll most likely use the fast on the Skinny 6s and Flat 5 I'm building because the slow pretty much has to sit overnight before sanding it back. Larry (lacro) has a lot more experience with the West epoxy than I do. Maybe he'll chime in.

Shelf life is basically indefinite as long as you keep the metering pumps on the cans. The metering pumps are calibrated to give the right ratio so one pump of hardener to one pump of resin. Couldn't be easier.

Mike

Captainhemo

IIIRC,  the fast  hardner is also  non-blushing.   If you are not using a non blushing hardner, you have to be sure to sand off the  hazy (blushed)  surface before applying anything else to   previous coats.
As Mike mentions,  Larry is a  wealth  of info on this subject  :thumb:

We've been using a penetrating epoxy here as well,   it soaks into the mdf more and  really toughens it up. Once  a layer or two are applied it will begin to build,  or you  could switch to  the reg  (thicker)  epoxy.  I believe Larry  told me you could also  just thin your reg epoxy with pure alcohol to  effectivly make it a penetrating epoxy. sure if he chimes in , he'll comment more on this

this  has ben working well for us
 
 Oh, and  pay attention to the ratio's, not every hardner uses the same 1:1 ratio, pay attention if you are buying  a pump or using a  measuring beaker  etc


jay

mlundy57

Oh, and  pay attention to the ratio's, not every hardner uses the same 1:1 ratio, pay attention if you are buying  a pump or using a  measuring beaker  etc

jay

Good point. The West uses a 2:1 ratio. The pumps are metered so that one pump each of resin and hardener provides the proper ratio. You don't have to buy the pumps ($25 at West Marine for a set) but they sure make life easier.

Mike

gregfisk

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Thanks guys, this is a problem I've had for years with MDF and not just on speakers. There's nothing worse than getting a really good paint job on something and the down the road a crack appears and ruins all of your hard work.

Every time I've had a seam in a project it cracks no matter what I've tried. Very frustrating indeed :duh:.

Greg