Ochocinco build thread: Building 3 MTM's - Completed -

[Faralon]

Did the research, saw how affordable they were, ordered the parts, printed out the cut sheet, and started cutting MDF...so I guess its official.

Total cost for all the drivers and x-over components: $230 (as of 1/20/2014)

The plan is to use these 3 Ochocincos as L/C/R for an HT setup. The surrounds will be some Neo Nano's that currently work as office speakers. They're a bit larger then your typical surrounds, but my intention was to be very frugal with cost, an original goal for the Ochocincos designers. I will be using the 4ohm drivers as thats whats in the Neo Nano's, and my receiver is able to select between 8 and 4ohm.

The reason I chose the Ochocincos is due to the fact that they're using a larger version of the same speaker that are in my Neo Nano's.

Neo Nano: 4" Dayton ND105-4
Ochocincos: 5.25" Dayton ND140-4

The tweeters are different, but my hope is that they will match just fine.
I plan on adding a sub eventually. My guess is these will do just fine. The Neo Nano little 4" driver can put out some decent low end in its ported enclosure...time will tell how this 5.25" driver in a sealed cabinet will do...but with 6 of them...my guess is I'll be happy to wait on the sub for now.

More to come as the build progresses. Speakers and components arrive in two days! I cut what MDF I could, but its 7'f outside, and my bandsaw is out in the garage!

[cjd]

The NN's I heard had... some upper midrange issues. I think that's not uncommon - a divergence from simulation and reality, perhaps. Or, as we found with the Ocho, a change in driver response from published data, and the sims being based on published data...

At any rate, they're likely to do great as surrounds anyway. I think the Ocho will work well in the mix. The set is all 8ohm (those 4's are wired in series) so very comfortably stable - a good intro to what you can get in an HT DIY at a great price, easy to build boxes or buy from PE.

C

[---k---]

Cool. I think these are some of the best value speakers and don't get the love they deserve. $230 for the parts for 3 is amazing for what you're getting. imho. I'm looking forward to seeing your progress.

BTW, I built a pair of NatNeo's. I think I used the original crossover and built the box slightly differently. I found them somewhat harsh. I made some minor changes by ear to the crossover using parts I had on hand that I thought made them better. I currently am using them as front high channels with my Khans. For height channels, I don't see an issue. I'm sure they will be good enough for surrounds, but maybe try and find my thread. The extra parts will be real cheep to try out. I'll do some searching.

[---k---]

Here is the Neo-Khan design that may match better for you:

https://www.htguide.com/forum/showthread.php?37990-The-Neo-Khans-ND105-4-ND20FA-TM

BTW, have you considered building the Ocho's ported instead of sealed? This would give you some more bass extension. I see you've already cut the wood, so probably too late, but.... I think you'll like them sealed regardless.



CJD: Next time you have your measurement gear out, if you want to let me know I can bring these over. Get a ND 105 design to round it out the series.

[Faralon]

Glad you two jumped in here, and thanks for the input.

I have to admit, I'm curious as to how well they'll perform sealed, and I like the space savings of a sealed design and have never had a sealed speaker. I believe I read that these have an F3 in the upper 50's right? That should be plenty for now. I am curious about perhaps using passive radiators like Definitive Technology and others are doing to keep enclosure size small but add a little more bass.

I did read where you said to use the AviaTrix dimensions to port them but decided against it for now.

The Neo-Khan's have me thinking. I could just build the Neo-Khan box, and stuff Chris' x-overs and speakers in it and call it a day. That or the Seiscero TM box. Thoughts?

[cjd]

I think everyone was really surprised by the bass (quality and quantity) of the sealed Ocho at the Chicago DIY event they made it to - if you have plans for a sub, that's an ideal build.

I have plans to revisit the Pecorino since I built that with the shielded RS100 (NLA) and there's the new paper version and all - a ND105 based setup has also been in the thinking but stepping on toes, etc. always leaves me wary. I might switch to using the new Dayton tweeters that are very similar to the ones used in the Ochos. I sorta wonder if it'd be worth my time to toss a cheap box together for the two Ocho variants and try these tweeters - might give a 3-way a whirl while I'm in there.

Measurement gear is pretty easy for me to get running any more - as long as the laptop doesn't completely give up. I should try to get the new laptop configured and usable. Finding time right now... There's a reason the finishing on the Nebbiolo is taking soooo long. A lot going on and very low energy levels.

Maybe I should spec super fancy box shapes and make some of this my InDIYana project. hah. I wonder if I could get a 5 speaker setup for less than the driver budget cap - that could be interesting! I could add that to the 4 or 5 other projects I have parts for...

Thread derailed sufficiently. Back to speaker building - or at least dreaming (on my part..)

[---k---]

The Neo-Khan's have me thinking. I could just build the Neo-Khan box, and stuff Chris' x-overs and speakers in it and call it a day. That or the Seiscero TM box. Thoughts?

I don't think it would be a huge problem using my sealed box with Chris Romer's crossover.
As far as the crossovers, iirc, I originally built his first crossover version which has sense been revised. I'm not sure which version you have. Likely you have the improved version, so maybe you're better off already. If you like them in your office, maybe no reason to change other than to try something different.

I seem to remember that my inductor was very slightly different because it is what I already had on hand from and old project. I would suggest leave the inductor alone since it is the most expensive part, and close enough in spec. The biggest improvement to my ear came from just flipping two of the original crossover resistors around. So, this is a no cost change.

I think I heard big differences between the crossover I started with and what I ended up with. So, I think you should experiment. The parts costs of the different caps and resistors is probably less than $10. If I were you, I would buy a handful of extra resistors of various values and a handful of 1.0uf caps that can be added in series to the existing cap, and then play with the crossover yourself and see what you personally like as opposed to either me or Chris Romer.

You may even want to have a few resistors on hand anyway to season the Ocho's to taste. I will warn you though, and I think I told this story in the design thread. I first heard them and thought the top end needed to be brought up. CJD swapped a few resistors and we listened. At first I was like Yeah! I like that. More sparkle, but it wore on me. We tried a few other things and after a bunch of listening ended back at the original design. ... It is like shopping for a TV. In the showroom they crank the brightness WAAAAAY up to make the TV look eye popping - I think many TV's even have a showroom demo color mode!. But, you get that home and it blinds you and just looks artificial. You end up turning everything way back. Speakers are much the same. What sounds good when you first walk in the room doesn't sound so good when you really listen.

So, if you haven't ordered parts yet... it is a no brainer. If not, check around on the shipping between the three different vendors, etc. I actually bought a lot of my season to taste resistors at my local Fry's. They got a real good selection. You might have some other local electronics place with resistors.

[Faralon]

Typical "Box being glued together" picture...

[---k---]

Not enough clamps.

[Faralon]

Haha, just enough. Hey, its square. Do you guys have any recommended size/location for bracing? If so, I'm just gonna wing it. Do I really need to round over the internal bracing...I'm guessing its not just for looks when people do it, but I've never asked.

[Faralon]

Did some scribbling...

[---k---]

I don't remember if I braced mine or not. I think it would be helpful. The more the better in some people's mind. I would put at least one across the middle. But dividing it up into thirds would be even better. Some would argue that one vertically in the middle would be best, and I would agree as long as there is something added to brace the baffle.

You definitely do NOT need to round over the edges of the bracing. I've done it, but it was more because the router was sitting there and I could.

Make sure you have the drivers in hand before you go cutting the baffle. Always double and triple check my measurements. I'm not always the most precise in the workshop. I'm a good rough carpenter, not a finish carpenter. Don't glue the baffle on until you've test fitted the drivers and are happy.

[BeerParty]

Haha, just enough. Hey, its square.

It doesn't look square to me. More like a rectangle.

Ryan is right, you don't need to worry about round-over of the bracing. That is just an aesthetics thing.

For these boxes I would recommend one small brace side-to-side in the center of the cabinet. That is what I did in my AviaTrix MTM and it seems to be sufficient.

[Faralon]

Sweet, thank for the input guys. I'm going to brace them in 2 spots, and not worry about round overs. Tru...it is pretty rectangular

Goodies arrived today!









Ryan, your measurements are still good...on the tweeter too.



Back to the cabinets:













Test fit is good!



That's all for today!

[---k---]

Looking like some good progress. :T

[Faralon]

Sanded all the joints even...cause...um....my cuts weren't PERFECT.



Recessed the tweeters, rounded over the edges, and chamfered behind the speaker cutouts...trying to give these little drivers the best setup for success.











Next up, finish the bracing in the other 2 cabinets and get some polyfil/stuffing/whatever in these bad boys.

[cjd]

Nice work!

[BeerParty]

:T For both the work and the pictures.

[Faralon]

Thanks guys...more progress. Yesterday we built the 3 x-overs. PE shorted me 1 20ohm resistor, so you'll see a pair that I got from "the shack" just to test the circuitry in one or more of the pics. Today I lined the cabinets, wired up the inputs and tested out the covers and a test fit run on the baffles. Tomorrow, we'll be sealing up the baffles and getting them ready for paint!

Impressions: I love them already. Family and I just spent about an hour listening to one of the speakers with clamps holding the baffle on. Can't wait to get all 3 playing at once!

Initial setup of the x-overs before wiring the inputs/speakers to them.

[---k---]

Looking good. Be careful with listening to them before they are finished. You might not ever get them painted or veneered or whatever.

[MickRS]

Looking good. Be careful with listening to them before they are finished. You might not ever get them painted or veneered or whatever.

Hahaha, this! I once made speakers that stayed unfinished for years.... Then I finished them of and after two weeks they were sold...

But looking good there!

[BeerParty]

Be careful about putting foam over the crossovers - if you drive the speakers hard the crossover components will get hot. They need air around them for cooling. I don't know if your foam is flammable, but I have seen pictures of several scorched crossovers and would hate for that to happen to your speakers.

You could leave the foam out of that section, you did an excellent job on the rest of the enclosure so I think leaving that area uncovered should be fine. If you want foam between the driver and the crossover location, install the foam so there is air space between the components and the foam. A couple of pieces of scrap wood hot glued to the top of the crossover board should keep the foam away from the components.

[cjd]

Be careful about putting foam over the crossovers - if you drive the speakers hard the crossover components will get hot. They need air around them for cooling. I don't know if your foam is flammable, but I have seen pictures of several scorched crossovers and would hate for that to happen to your speakers.

You could leave the foam out of that section, you did an excellent job on the rest of the enclosure so I think leaving that area uncovered should be fine. If you want foam between the driver and the crossover location, install the foam so there is air space between the components and the foam. A couple of pieces of scrap wood hot glued to the top of the crossover board should keep the foam away from the components.

This is good advice. The resistors are the probably trouble spot, and while none of these are likely to get too hot, there is always that potential.

[Faralon]

Thanks for the tips guys. I had cut that piece long width wise, so when its tucked into that area there is a natural arc over the components. Adding a piece of wood to the front/back of the x-over board will make sure there remains some breathing room w/ pretty much zero extra effort, and I can still keep that area covered in foam. I'm currently filling little areas that need some work...sofar I've been able to just fill some small gaps with extra wood glue. I've been creating a lot of dust with sandpaper getting everything flush. I'll probably start priming the speakers tomorrow.

[BeerParty]

I've been creating a lot of dust with sandpaper getting everything flush.

Don't you just love MDF dust? :roll:

Good choice on the primer - a lot of people don't know to avoid the water based primers when working with MDF. Have you worked with MDF before?

[5th element]

I am curious. How did you create the recess for the tweeters with the central piece removed? I always use a circle cutter on the router for that and with the centre removed that becomes a bit of a problem. I can always glue something in from behind to act as a pivot, but if I had another way to rebate when the centre had been already cut out that would be great.

[Faralon]

5th, good question. Obviously, as you've seen, I fly-cut the tweeter hole 1st. Afterward, the tweeter was inserted an then outlined for its radius. I then used the "puck" that was leftover from the fly-cut, inserted it back into the hole to use as an alignment tool for the fly-cutter. I then set the fly-cutter to the external radius of the tweeter and ONLY cut the down into the MDF the thickness of the tweeter itself. Once I had my perimeter, I use a 1/4" spiral cut bit in the router and hand routed it. Since the perimeter was already cut, I didn't have to worry about not being able to make a perfect circle.

However, IF I HAD A CIRCLE JIG, it would have been a lot easier.

This sort of thing is always hard to describe in writing, but I was simply trying to come up with a solution with the tools I had at the time.

Here is a picture of the "puck" left over for the 5.25" drivers. You can see, that if I didn't cut all the way thru, how there is a nice recessed edge on the outer part of the circle, and you would just hand route the internals to the depth you need for the tweeter.

[Faralon]

Ok, so we're all ready for Sealing/Priming. I spent the extra time to radius the top and bottom of the baffles on the Neo Nano's to match the Ochos.

Removing the drivers from the NN's



NN's before:



NN's after:



Group Shot:

[Faralon]

BP, I've worked with MDF before, making form blocks to shape aluminum airplane parts, and for use as workbench surfaces, but nothing like speakers. As for the BIN, I read that on the forums here after searching for good/proven ways to seal/prime MDF, especially the edges. The dust covers on my NIOSH mask are completely full of MDF dust and completely brown.

[5th element]

Thanks for the description, I thought it might have been something like that and the pictures help to illustrate what it was you were talking about. Do fly cutters work in standard drills if they are held in a drill stand or do you need something more substantial? I'm guessing this sort of thing would only work well with small rebates as a 6" rotating cutter would be rather dangerous! I do have some smaller forstner bits and they work fine. I think the biggest one I've got is 30mm, which is still probably less than half the diameter you cut for the tweeter.

[Faralon]

5th, the limiting factor with the fly cutter will be the wobble introduced with larger radius'. But if you have it in a solid drill stand, I can't imagine it'd be any more issue then a drill press like mine. These fly-cutter bits aren't counter balanced, so they get a bit sketchy. Keep the fingers AWAY!

As for the boxes, 1st coat of primer/sealer and sanding is DONE! This BIN stuff is MAGICAL!!!



Heading in for the 2nd coat now.

[---k---]

Looking good. What is the final color going to be?

[BeerParty]

I am curious. How did you create the recess for the tweeters with the central piece removed? I always use a circle cutter on the router for that and with the centre removed that becomes a bit of a problem. I can always glue something in from behind to act as a pivot, but if I had another way to rebate when the centre had been already cut out that would be great.

I also use a circle cutter on my router to make my driver recesses. I usually remember to cut the recess first, but I forgot when building my AviaTrix. I posted photos and a description of how I handled it in post Mission Possible DIY of my build thread. Take a look if you are interested in a router only solution.

[5th element]

I also use a circle cutter on my router to make my driver recesses. I usually remember to cut the recess first, but I forgot when building my AviaTrix. I posted photos and a description of how I handled it in post Mission Possible DIY of my build thread. Take a look if you are interested in a router only solution.

I have done exactly that myself in the past too, it's just a bit of a pain!

[JonMarsh]

5th, the limiting factor with the fly cutter will be the wobble introduced with larger radius'. But if you have it in a solid drill stand, I can't imagine it'd be any more issue then a drill press like mine. These fly-cutter bits aren't counter balanced, so they get a bit sketchy. Keep the fingers AWAY!

As for the boxes, 1st coat of primer/sealer and sanding is DONE! This BIN stuff is MAGICAL!!!



Heading in for the 2nd coat now.

Another way to do this if you have a really clean accurate through hole is a router with follow bit, one of the sets with multiple sizes of follower bearings.





Construction looks good, and even better, nearly done! :T

[cjd]

I use this one: http://www.amazon.com/gp/product/B000BJJY5M/

Using shellac beyond a base layer sealer (where it excels) is a bit of a learning process, but I like the results a lot. Not likely much use on MDF, but on cherry veneer...

[JonMarsh]

Probably exquisite on cherry veneer! :T

[Faralon]

Thanks guys. Final color is going to be white. I'm kinda a n00b at painting/sanding, so I'm just doing what feels right. I'm done with the 3rd layer of BIN (I went with a 3rd just to use up the can). I've sanded from 220, down to 800. Its super smooth. I should be applying the 1st coat of the final paint, BEHR Semi-Gloss white, tonight. Do you guys have a recommendation for a clearcoat/protectant? Something to keep those dirty fingerprints off the paint.

PS, I'm assuming I sanded and worked with the BIN a bit too much but...like I said...rookie.

[Faralon]

So, I used leftover acrylic paint from Behr that we had around the house for the topcoat. I used a small, smooth roller to apply. I'm not so sure that was a smart decision as its not laying down like I'd hoped. Is it alright that I used acrylic? We'll see how sanding goes once it cures. I used the same small/smooth rollers for the primer, but it was a much thinner paint mixture too. I might think about thinning down the acrylic a little bit to try and get it to lay down better.

[TEK]

If this is just after painting, that might flow out after a while.
But it might seem as if you are going to have visible edges between the baffel and the sides walls.
I had the same on the back of my sub. Tought I had done the ground work good enough, but no... Lesson learned.

Btw, a trick to make the paint flow better may be to heat it a bit before use. I tend to let it stand in front of the heater a while before usage. And of course, use a roller for extra fine flat surfaces.
And - be sure to let them dry and that you get them sanded down before applying the bext kayer - if your paint is anything like mine, the next layer will be twice as bumpy if you dont sand it down first (been there, done that ;-)

[---k---]

Ha! That is the exact finish look I have on my Khans. But, that is what I was going for.
I was looking to get a little texture hide imperfections. I used a heavy duty acrylic black paint from Sherwin Williams with a foam roller.

I'm not a paint expert, but I've seen to get perfectly smooth and high gloss, people typically either do the wet sanding thing (after lots of regular sanding. search piano black) or do spray paint. I've seen some pretty good paint jobs done with rattle cans. Not as crazy as it sounds.

Ask the guys at the paint stores. There are also paint extenders you can add to your paint to get it to roll and flow better. New paint and something like this might roll better. It all depends on how glossy and reflective you want.

[TEK]

On my sub (backside) , I first tried regular sanding. Vet sanding was 100 times more efficient!

[cjd]

Wet sanding is a must. On shellac that means mineral oil I have learned.

Acrylic may never finish to a smooth gloss but it can polish up well. It has a long cure time to get the necessary hardness for polishing. 800 and even 1200 grit 3M wet. Keep plenty of water, rinse the paper regularly to keep it clear.

[JoeAngelicchio]

These look great! :T

[Faralon]

Thanks Joe! So here is the current plan of attack for today. Sand down the acrylic with 220, to knock off a lot of the peaks in the finish. The acrylic will be thinned with water. I liked how the BIN flowed, but it easily produced run's that I had to stay on top of. The plan will be to try and get the acrylic a tad thicker then the BIN, and see what we get. Here is a quick pic of before and after sanding the two coats of acrylic.

Before is on the LEFT, sanded is on the RIGHT...not the best of pics, but I tried.



The temptation to just stick speakers in these things and enjoy them is KILLING ME!