Overnight Sensation MTM build

[Kristian_AUS]

Re: Overnight Sensation MTM build

Finally "finished" my OS's. Thanks for publicizing your designs Paul C., I really like them. While I didn't demo a lot of in store speakers, to me the OS embarrasses many speakers that were an order of magnitude more expensive. The only retail speaker I listened to that I still like is the Martin Logan Summit X. I'm looking forward to seeing if that changes after I build the Sunflowers.



Before I finished my stands I just had them sitting on top of a couple of cardboard boxes 18" off the floor. After putting them on stands I was surprised at how different they sounded. The stands are ~3' high as they'll eventually go behind my sofa, so they may not really be suitable to use for mains. At first I thought that I'd mixed up the polarity but I used the JL Audio app and found they were fine. I find that the bass is somewhat subdued and I need to turn up the volume much more to get the same sound level. It may just be because of my "missing" wall. I might play around with stuffing and try them in a different room.

[Kristian_AUS]

Re: Overnight Sensation MTM build

Finally finished the cabinets, put the speakers in and wired up the crossovers. After a few technical glitches of my own fault with the receiver I have them up and running. At first I thought that I'd wired them incorrectly but I just didn't have the volume turned up enough :rolleyes:. The SC-75 seems to need to be turned up quite a bit before I hear anything (this is my first modern receiver, the last amplifier I had was 25+ years old). Then I thought that I'd wired the mids out of phase as the bass was non-existent. Or possible because I had no stuffing in the cabinets, but I later discovered that the default setting on the receiver was small for the fronts. I set them to large and told the receiver it didn't have a subwoofer as well as setting the crossover point as low as it would go (50Hz) to make sure they were getting a full signal. That seemed to fix my problem, but due to those issues and the late hour I still feel that they may not be going as low as they should be. May just be in my head, I'll have to have a listen in the morning and go over the wiring again. I think one wire in the cabinet is touching one of the cones. If I remember correctly, none of the components in the crossover are directional, correct me if I'm wrong, so that shouldn't be the issue.

Here are a couple of less than stellar pictures. Next on the to do list is finishing up the stands. One thing I've learned is that although I'm happy with my first attempt at veneering and painting, I need to do more prep work.

[fastbike1]

Re: Overnight Sensation MTM build

http://www.parts-express.com/magnetic-grill-guides-0395-dia-x-02-h-8-pcs--329-045

Thanks, that's a good point! What size magnets would you recommend if drilling to within 1/4" of the front? I was concerned about placing magnets close to the drivers (I don't know if it's actually an issue) - especially with the limited real estate on the OS MTM baffle - and picked the smallest ones I thought would work and put them about 1/32" from the surface. It would have been nice to spare myself the extra step of filling the recesses with bondo.

[Kristian_AUS]

Re: Overnight Sensation MTM build

Thanks, that's a good point! What size magnets would you recommend if drilling to within 1/4" of the front? I was concerned about placing magnets close to the drivers (I don't know if it's actually an issue) - especially with the limited real estate on the OS MTM baffle - and picked the smallest ones I thought would work and put them about 1/32" from the surface. It would have been nice to spare myself the extra step of filling the recesses with bondo.

[fastbike1]

Re: Overnight Sensation MTM build

Next time drill the holes for the magnets from the back side. Drill to within 1/4" of the front. Invisible, but still works. No tendency to pull out of the glue.

Used a 1/2" flush trim bit to make recesses for 3/8" x 1/10" rare earth magnets in case I add grills. A drop of gorilla glue, some bondo and voila!

[ATTACH=CONFIG]46448[/ATTACH] [ATTACH=CONFIG]46449[/ATTACH]

[Kristian_AUS]

Re: Overnight Sensation MTM build

Used a 1/2" flush trim bit to make recesses for 3/8" x 1/10" rare earth magnets in case I add grills. A drop of gorilla glue, some bondo and voila!

[Kristian_AUS]

Re: Overnight Sensation MTM build

Progress continues... I chose the Kona as I thought it'd blend in with future decor better than the other colors. I tested poly on black lacquer which seemed fine as well as clear lacquer on stain which also worked. Lacquer over poly didn't work - it lifted the coat. I preferred the look of lacquer on the black over the poly, having said that the samples weren't buffed/polished - I'm not sure how much this will change the results, the poly had more of a satin look to it where the lacquer had higher gloss.

I put a few coats of clear on the cabinets (before the baffle went on) which went on well, applying a tack coat each time first then a heavier coat a few minutes later. I got a little heavy handed on the last coat and put runs on both boxes . Oh well, I'll sand them out. Another couple of coats will be going on over the entire cabinet now that the baffle is on anyway. My reasoning for gluing the baffle on after stain/clear was that I didn't trust tape to keep the primer/black from seeping into the veneer and thought the clear would stop it happening.

I still have some grain showing through the clear but hope to get a smooth finish after a bit of sanding and a couple more coats of clear.

The edges have been sealed with a 50/50 mix of water/glue and area ready for primer.

[Kristian_AUS]

Re: Overnight Sensation MTM build

A little more progress this evening. Finished off the base and tops for the stands.



A few coats of poly on the Cognac, Kona and bare Walnut really changed their look. And unfortunately I like them all :o. The Kona doesn't hide as much as it originally appeared to so I think it's going to be my choice. I still have to test the compatibility of the poly on black lacquer and clear lacquer on stain as I'd like to just have one type of clear coat on the boxes.

[Kristian_AUS]

Re: Overnight Sensation MTM build

I might just give that a try this evening. I wanted to take the edge of the contrast between the black baffle and walnut veneer, but the stains made it a little too dark. I'll put some poly on the Cognac and Kona too and compare all 3. The Aurbacs are close to what I had in mind so just the poly might work out. I was actually eyeing the walnut burl before I bought the walnut, it's really nice.

Thanks Lee!

[Leroy R]

Re: Overnight Sensation MTM build

Try just putting a coat of poly on a scrap of your veneer with no stain. The poly will darken the wood a bit on it's own. I think that wood has nice color without stain and I'm thinking a couple coats of poly will make it even nicer.

Here is a before and after of my tritrix's, before and after poly, no stain.





You can also see it in the burl walnut Aurbacs I posted pictures of earlier in this thread.

The OS's that I built for my mom are the only enclosures I've used stain on so far. They needed to be a bit darker to match her other furniture.

[Kristian_AUS]

Re: Overnight Sensation MTM build

Finished veneering the cabinets today, the base has been left bare and I'll give it a quick coat of black paint. Just trying to decide which stain I'll use. I tried a couple of different types out - on the left is Kona, on the right is Cognac. I'm leaning towards the Cognac, the Kona turned out much darker than I expected. It's hard to tell in the picture, but I tried applying the Kona with a foam brush and a rag. I was surprised that the rag gave the most consistent staining.



I also started making my speaker stands, part of the base (3/4" MDF) can be seen at the bottom of the picture above. The top of the base (1/2" MDF) is currently being veneered and will be glued on to the bottom piece. Here's a picture of what I'm going for. I'm using 3" PVC pipe which I'll fill 1/3 - 1/2 way with sand. A 1" PVC pipe will run down the middle for the wiring. The binding posts exit the bottom of the cabinet, I wanted to be able to remove the speaker from the stand if I re-purpose them. I was hoping to find a more elegant solution, but I'll just have to move the binding posts to the rear of the cabinet if they become PC speakers one day.



The base of the cabinet will be about 3' high on the stands. I did this so that when I move them to surround duty that the base will be just above the edge of the sofa they'll be behind.

[Kristian_AUS]

Re: Overnight Sensation MTM build

Veneered the sides last night. I'm using Tightbond coldpress veneer glue. I applied the glue using a scraper on my test piece but it wasn't too consistent. I used this roller for the cabs and got a nice consistent coat. I found it best to work from the middle out to make sure I got a nice coat of glue all the way to the edge.



I also used a scraper to apply the veneer on my test piece but went to this J-Roller for the cabs, it was much easier to use. I worked from the center of the veneer along the grain and slightly outwards towards the edges making sure that I didn't have any 'dry' edges without glue being pressed out. You can tell when you've pressed the veneer down evenly when the 'popping' sound goes away and it quietens down.



One of the disadvantages I've found using cold press glue rather than contact cement is that cold press glue will ooze out which is why I masked the edges of the cabinet to protect the veneer. I haven't yet tried removing dry cold press glue from veneer so I'm not sure if it's an issue. What I like about cold press glue is that I can apply one coat and immediately put the veneer. When I made my router table I used contact cement and had to put a coat on the table and laminate, wait for it to dry, then put another coat on and wait for it to dry before gluing the pieces together.

I did both sides of each cabinet simultaneously, laid the cabinet down on top of a piece of MDF, put another piece of MDF on top and piled on the weight. I also put wax paper on top of the veneer so the boards wouldn't stick.

[Wolf]

Re: Overnight Sensation MTM build

Thanks for the tips. I bought a couple of rattle cans and plan do a few tests on scrap to see how they go on. I'm hoping that one type of clear will be compatible with both the stain and paint which might improve the finish and minimize seams.

Good tip Wolf, I didn't realize polyurethane gave a yellowish tinge. Do you mean that it's noticeable over paint (other than black) or also veneer?

Yep. Both are visible change.
Polycrylic does not yellow.
Later,
Wolf

[Kristian_AUS]

Re: Overnight Sensation MTM build

Slowly but surely making progress. Had to enlarge the opening in my router table insert, improvisation was the name of the game.



Cut 1/2" roundovers on the ports and chamfered the rear of the driver openings with a 45° bit. I forgot to reset the depth on my router when doing the recess for one of the drivers and cut a little deeper than I meant to . Thankfully I caught it right after plunging in - nothing some bondo won't fix.



I've almost finished my router table fence. Just have to add the dust port and split my subfence and I'll be done.



Next step is veneering the sides and top of the cabinets. I tried different methods of trimming veneer on a test piece. First using a veneer saw, then using a top bearing spiral flush trim bit. The veneer saw was ok with some very minor tear out, although the test piece was glued to a single piece of 1/2" MDF so there wasn't much surface to rest the saw against. I'll have to try it on a box. The router was better and improved when I masked over the cutting line.

[knowledgebass]

Re: Overnight Sensation MTM build

Polyurethane will yellow over time. Most will start out mostly clear, although the oil base ones may have a bit of a yellow hue. The water-base ones tend to start out clear and are more UV resistant (e.g. have more inhibitors). Hasn't happened to me yet, but it will still apparently yellow in time.

I'm unfamiliar with polycrylic. From the description and given the (R) mark Minwax includes after the word "Polycrylic," it sounds a lot like the water base polyurethane I've used from General Finishes. Don't take my word for it though, as I have no experience with it ;)