Vintage 10" Sub build - TAKE 2!!

[unclejunebug]

The slot port I need is 23.75"x8"x1.25" which will have a 90 degree transition in order to fit. Would there be much benefit in trying to build the port so the 90 degree turn is curved rather than a straight, perpendicular turn?

[Chris Roemer]

Not much, but if you can hit the inside (sq.) corner w/a roundover bit, it wouldn't hurt.

[unclejunebug]

Not much, but if you can hit the inside (sq.) corner w/a roundover bit, it wouldn't hurt.

Thanks, Chris. I will at least do that much. If I can't find a quick/easy solution for the other corner then I will attempt to skip it. The engineer in me will make that tough so I'll see if I can let it go :D

[Chris Roemer]

You could stick some cove molding in the corners, but I THINK (in theory) it shouldn't matter.
Remember, you're not really blowing air THROUGH the vent; that mass of air is just resonating back-and-forth.
That makes ME feel a whole lot better. ;-)

[unclejunebug]

You could stick some cove molding in the corners, but I THINK (in theory) it shouldn't matter.
Remember, you're not really blowing air THROUGH the vent; that mass of air is just resonating back-and-forth.
That makes ME feel a whole lot better. ;-)

Haha, that's a good explanation. I've always sort of considered ports to be an "exhaust" but what you're describing sounds quite different than that. I have considered some cove molding but all the ones I've found have a some amount of lip on either side of the curve. Probably not the end of the world but it also sounds like it wouldn't really be necessary in the first place.

[unclejunebug]

I have a 20mil paper backed Walnut veneer that will be going on ALL sides of the cabinet, meaning I plan to veneer the face of the baffle where the sub will mount (marked red in the image below) as well as the inside edge of the outer baffle recess (marked in blue below). Right now I'm mulling over the best way to approach this. What I have currently come up with are the steps below...

1. Veneer the inside edge of the outer baffle (marked in blue) using rubber cement and them trim the veneer flush with the outer and inner faces of the panel. This will be done BEFORE gluing in any additional inner baffle panels.
2. Attach veneer to a MDF panel using PVA glue (either Titebond II/III or Titebond Cold Compress glue) and then cut the panel to size including the appropriate sub hole cutout, centered on the panel (this would make up the surface marked in red below).
3. Glue in this first inner baffle panel using standard wood glue (so veneer surface mated to MDF and adhered with Titebond glue)
4. Cut an additional inner baffle panel to achieve required thickness
5. Glue it in with wood glue

I'm thinking I don't want to use rubber cement to attach the veneer to the panel that makes up the surface marked in red. If I did then the majority of the inner baffle would be glued to the outer baffle with rubber cement instead of wood glue that didn't seem to me like rubber cement would be a strong enough bond here.

I'm curious to know if anyone has any ideas or feedback on what's outlined above?

I had originally considered trying to veneer both surfaces AFTER gluing in the remaining panels but that seems like it would be a headache given that there would be minimal tolerance in cutting out the required pieces of veneer as well as with the rubber cement. If what I cut out is the wrong size there could be gaps and if I don't line up everything exactly perfect then there could also be gaps OR the veneer may "spill" over onto an adjoining surface.

EDIT: Images are working now...

[unclejunebug]

I cut some oversized 3/4" and 1/2" pieces to laminate together for the inner baffle. I got those pieces glued up and let them dry for a few hours. I then cut a piece of the walnut veneer and now have 330lbs of floor tile gluing that to the what will be the visible side of the inner baffle. I'll let this dry overnight and then trim down the whole thing to fit inside the cabinet...

[unclejunebug]

I got the inner baffle piece trimmed and did a dry fit...



Then I traced the hole onto the veneer, found as close to dead center as I could, cut out the hole for the sub, then checked another dry fit...



I fit the RSS265HF into the hole to check tolerance and I'm discovering that the sub has a very narrow mounting lip. I marked one hole with a pencil and it's very close to the sub cutout. I was originally planning to mount the sub with some inserts but now I'm concerned there won't be enough MDF material to drill a hole big enough for the inserts without blowing into the cutout. I will have to do a little more investigation.

Next thing I need to do is veneer the bare lip of the outer baffle. Once that's done I can glue in the inner baffle.

EDIT: In regards to the inserts. The inner baffle that the sub mounts to is 1 1/4" thick so I think if I drill the insert holes on a slight angle I should be ok.

[unclejunebug]

One thing I'm also realizing with the T-nuts along with the reduced box size is that the window bracing I was planning on will overlap with the location of the T-nuts which won't work as originally planned. This has me rethinking how to implement the bracing along with potentially the slot port.

The original slot port is 1.25"x8"x24" to get a 22Hz tune with a rear air port velocity of about 20 m/s. I am now mulling over a 3" round port instead and WinISD gives me a length of about 16.5" for the same tuning but the port velocity increases to about 28 m/s. If I ended up going with the 3" round port I would either add a round over on both ends or go with a 3" Precision Port with the flanged ends on both sides.

What I'm curious of is if there's any way to quantify the effects of flanged or rounded port ends on either air port velocity OR the potential for chuffing. When selecting "two flanged ends" within WinISD for port correction the port velocity doesn't change so I imagine that there is zero effect there. I have seen lots of comments in other threads saying that rounded/flanged ends reduces chuffing but is there any way to know how much? Or is there a good rule of thumb for the size of a round over needed for a certain air port velocity? i.e. 28 m/s port velocity would require a 3/4" round over or something similar?

[Chris Roemer]

The (large) roundovers (esp. of a Precision Port) don't really change the velocity of the air in the tube. What they DO do is minimize the turbulence at the port exit(s), which is where most chuffing comes from.

[unclejunebug]

The (large) roundovers (esp. of a Precision Port) don't really change the velocity of the air in the tube. What they DO do is minimize the turbulence at the port exit(s), which is where most chuffing comes from.

Is there some turbulence to port velocity relationship? Something that would determine whether or not the roundovers would cancel out any potential chuffing at a certain velocity? 28 m/s seems to be a bit high but maybe I'm wrong about that?

[unclejunebug]

This seems like a better question...

Would a port velocity of 27 m/s be considered too high if the port was a 3" Precision port with flared ends on both sides?

---

The question above is no longer valid but there is no text strike-through option. I decided to just move ahead with the slot port as originally designed. Need to stick with what was intended rather than try and find something "easier."

[unclejunebug]

Starting working on the port. I was originally planning on using two of the inner cabinet walls as port walls but decided to build the port as a standalone unit that will get glued into place so I could add a round-over to both the internal and external ends of the port. It also made it easier to build a curve into the slot port at the bend...



Some pre-painting of the other side of the port...

[unclejunebug]

No major progress but got the port assembled and clamped. Used some 1.25" spacers to keep the correct opening size and some parchment paper so they wouldn't mar the paint too much when removing them. Once it's all dry I'll flush trim sides and then trim the ends to the proper length on my slider saw.

[unclejunebug]

Did some work on the port today. With my port dimensions, WinISD says I need a 25.11" port. The port will exhaust out the bottom of the cabinet and the bottom is 1" thick so I measured a piece of string at 24" to trim the port down (trying not to stretch it too much). I first flush trimmed the sides and then got the long end of the port cut flush to where it will butt-up against the bottom. I then laid the string along the side of the port, marked the end, and then cut it to size...



Added a bit of a round-over on the exposed edges of the port as well as the opening that will be inside the cabinet...




Dry fit in the cabinet...



As I was building the port I was able to add caulking along both seams on the backside. I couldn't do that to the other two seams the same way due to access. I wanted to add some caulking on these other two seams so I bought some black caulking and some fuel line tubing, heated up one end of the tubing with a heat gun, and then worked it over the tip of the caulk tube. I cut a length of tubing, taped it to a coat hanger, and then trimmed the end of the tubing at an angle. Similar to what you would do with the tip of the caulk tube itself. I also fed a little bit over another piece of coat hanger cut at an angle to use to wipe off the excess.



This seemed like a brilliant idea in concept, however in practice, it failed tremendously. At first the caulking started feeding through the tube just fine and I was feeling pretty darn smart. The farther along it got the more difficult it became. Eventually the caulking stopped traveling through the tube and the tubing popped off the tip, spraying black caulking all over my workbench. When I bought the tubing I picked up two different diameters. The one pictured here is the smaller of the two as I didn't want huge globs of caulk in the seems of my port.

Since the smaller diameter didn't work I tried the larger. I was able to get the caulk down to the end of the tube this time but the tube just had to be too long. By the time the caulk was at the end of the tube I couldn't really squeeze the trigger hard enough to get any kind of bead to come out the end of the tube. It was mostly due to the fact that the caulk coming out of the tip of the gun just couldn't push the caulk with enough force through the tube so what ended up happening was the caulk started seeping out around the backplate of the tube, getting all over the push rod of the gun. If you've ever tried using a tube of caulk that's already all dried up you'll know what I mean. It was bad enough to where I didn't want to clean it up so I ended up throwing away the tube and the gun (it was past its prime anyways).

So, hopefully the glued butt joints on the front side of the port will be sealed enough to where I won't have any leaks in there.