UMAX 15" Sub Build

[5th element]

RE the noises that the UM 10 was making, apparently there were problems with the glue used on the earlier production models. This would cause the spiders to come loose around the basket and the voice coil. This has since (apparently) been fixed.

[JonMarsh]

Well, that's a reasonable explanation, and may account for some.... I disassembled the driver myself, and the spider gluing was quite solid, but it was the front surround that came apart from the frame, pretty much on it's own all around. seemed to be some kind of contact cement, that didn't set up properly. So, maybe there was more than one issue.

The 15" looks fine, works fine so far, so when July rolls around I'll consider buying another driver and rebuilding the mall sub.

[5th element]

That was another issue I believe. If you look on youtube you will see some videos of people tearing down busted UM drivers.

[elessar]

just 2 questions,
did you ever get another UM10?
and did you ever have any more issues with the UMAX subs?

[JonMarsh]

I didn't get another UM10. They're available since August some time,but I've been so busy with many other things, that rebuilding the 10" system has fallen off my radar. Plus, I re-cycled the Hypex amp for that into the 15" system, in a separate box. Works qutie well, as the 15 is more efficient.

The 15" has been flawless. I did some research online, and it seems there was a large sized batch of the 10s back when I got mine, that were probematic, but I haven't read about issues with any of the other models. Unless you really need a small box, I'd suggest going with the 12" or larger anyway. Better radiation resistance and sensitivity and output level. GF hasn't had any problem living with the size of the enclosure I chose for the 15"*

[kevinm]

I got a UM10 a month or so back. No issues with mine

[TEK]

This isn't a design project, more of a project build report in progress-

Putting together a bigger sub for GF's HT setup- had some issues using a 10" UMAX sub in a standard PE sub cabinet (interference with brace, I think) and this is to address this, plus put something together with a cherry veneer that may at least resemble if not exactly match the equipment cabinet I talked her into buying from Magnolia HiF... you may see a pattern here, in that I am digging myself a deeper hole all the time. Hmmm.l


While looking at knock down cabinets for another project, I came across the one PE offers specifically for the UMAX 15" sub. Seemed like a pretty good deal, if the build design and quality were similar to the smaller ones I'd already been experimenting with, so I decided to go that direction, with some tweaks.



Basic assembly is straight forward, though of course, aided and abetted if you have an assortment of clamps. More clamps is always a good thing...




I put together a base made of a few layers of MDF, and of course, epoxy coated the whole cabinet with a couple of layers in preparation for the veneering.






Sanding it smooth is a bit of a time consuming process- the epoxy coat is both for the PSA backed veneer to adhere to, and is a good surface for the paint for the front panel and base.


The weather was nice and warm outside yesterday, though raw cherry shouldn't be in the sun very long, so I finished those steps after moving into the shade.




I could tell I was on a lucky streak yesterday because I even found my veneering scraping tool, and quickly, though I was prepared to make a home made one from an oak board.







The planned finishing process is to start next Saturday, doing the final sanding, then a coat or two of de-waxed shellac, a very light finish sanding, then wipe on poly. Until then, it's sitting in darkness, to hopefully prevent any uneven darkening of the cherry. I hear that's kind of touchy, and this is my first project attempting anything with cherry. The target piece of furniture is fairly light, so I aim to keep this one that way.

More reporting to come, including acoustical tests. This may get used with a Hypex sub amp I have, or it just may be driven with an Aragon Palladium mono block. Depends on whether the Hypex has the guts or not- it's got a nice EQ section, but that may not be needed in room. We'll have to see...

How do you apply the epoxy?

[JonMarsh]

With a foam roller, such as one uses for some types of paint. I use a small roller, typically 100mm wide, and a small disposable paint tray for that size which one can readily buy around here in the hardware or big box stores. I mix up the two part epoxy in the paint tray.

Note that I changed my finishing process from what was proposed in the section you quoted, and used General Finishes water baed poly, sprayed on, with sanding between some of the coats and a final rub out- described later in the thread.

[TEK]

Thanks Jon.
I'm planning on using epoxy on my livingroom speakers. There will be a lot of open pored mdf.
It will be clear why when I have got a bit longer in the build process...

[BobEllis]

TEK, my experience with epoxy on MDF is that it really soaks up a lot. I used TotalBoat brand which is roughly the equivalent of W.E.S.T. System epoxy. The same amount that covered the entire Baltic Birch and bamboo wavecor Ardent barely covered a side and the back of my MDF Poor Man's build and it will need another coat before paint. You will probably be better off sealing with the body filler Renron suggested elsewhere. You can sill use epoxy over that if you want to veneer with it.

I've been using a combination of 4" foam roller and wide body filler spreader.

[TEK]

TEK, my experience with epoxy on MDF is that it really soaks up a lot. I used TotalBoat brand which is roughly the equivalent of W.E.S.T. System epoxy. The same amount that covered the entire Baltic Birch and bamboo wavecor Ardent barely covered a side and the back of my MDF Poor Man's build and it will need another coat before paint. You will probably be better off sealing with the body filler Renron suggested elsewhere. You can sill use epoxy over that if you want to veneer with it.

I've been using a combination of 4" foam roller and wide body filler spreader.

Hmm...
I will probably not have access to the body filler Renron suggested here in Norway. However, the point with the Epoxy - as I think about it - is to create a "hard shell" over the MDF so that the paint will have a hard surface where joints between the edges will not shine trough over time.
I could first add a base coat to stop the MDF from sucking up all the epoxy, and then cover everything with epoxy.

[Steve Manning]

TEK ...... I don't know if it's better than going with the epoxy ( I suspect not), but talking with the local lumber yard they make custom signs out of mdf that they paint. They have been using two coats of de-waxed shellac, sprayed on, sanded between coats, then paint sprayed on top of that. I looked at one of their signs and it looked nice. Could be another option?

[TEK]

Shellac does not go very well with the final paint I'm using.
Maybe before the Epoxy? I have used shellac before, and my impression is that is does make a seal - but not a shell like surface like I expect from epoxy.
If this for example was a table top I'm quite sure shellac would do, I'm not as sure when it comes to the joints between for example the sides and the top.

[fbov]

...the point with the Epoxy - as I think about it - is to create a "hard shell" over the MDF so that the paint will have a hard surface where joints between the edges will not shine trough over time.....

You may be disappointed if you expect epoxy to prevent joint lines.
Early work: http://techtalk.parts-express.com/sh...highlight=seam
A solution:http://techtalk.parts-express.com/sh...ghlight=trough

Shellac does not go very well with the final paint I'm using.
Maybe before the Epoxy? I have used shellac before, and my impression is that is does make a seal - but not a shell like surface like I expect from epoxy....

And the same gentleman sealing with shellac: http://techtalk.parts-express.com/sh...highlight=seam

From personal experience, if shellac didn't make a shell, you stopped too soon. Shellac takes time.

Have fun,
Frank

[Steve Manning]

Shellac does not go very well with the final paint I'm using.
Maybe before the Epoxy? I have used shellac before, and my impression is that is does make a seal - but not a shell like surface like I expect from epoxy.
If this for example was a table top I'm quite sure shellac would do, I'm not as sure when it comes to the joints between for example the sides and the top.

They are using a water based lacquer for paint and a clear coat on top of that, also water based.

[TEK]

You may be disappointed if you expect epoxy to prevent joint lines.
Early work: http://techtalk.parts-express.com/sh...highlight=seam
A solution:http://techtalk.parts-express.com/sh...ghlight=trough


And the same gentleman sealing with shellac: http://techtalk.parts-express.com/sh...highlight=seam

From personal experience, if shellac didn't make a shell, you stopped too soon. Shellac takes time.

Have fun,
Frank

Thanks for the input and links. But, a 10 pages long thread 8O. The highlights next time, please...
I have to say that I'm not sure if I got your point. From what I read out of that first 10 pages thread, the best solution was ... epoxy... But expensive, and he had become sensitive to it.
He sums up the result in post 181: http://techtalk.parts-express.com/sh...54#post1709254

My understanding from what he writes (and have done a lot of testing to verify) is:
1) West system epoxy is the best choice (but expensive)
2) The only method he has got to work is the trench method filled with putty
3) You should let the MDF dry before applying finish

I expect 2) to be when not using 1). I might have misunderstood.

I also find that it seems that different people have very different experience. Some has no problems after several years. Other have a lot of issues.
I wonder if that might be due to local environment or differences in quality of MDF. Probably it's both as well as the craftsmanship.