Voxel - a mini-sub+

[Wolf]

Otherwise, I am a bit confused on the port itself... I found this build thread that used a totally different port, with supposedly good results:
http://techtalk.parts-express.com/fo...234#post975234

I don't understand how this guy used a 3' I.D. x 4.5" long port and got the right tuning out of the box. Am I missing something?

You're not missing anything. That project builder mistakenly thought port tuning was a function of volume in the port, and made the port larger diameter and shorter to get the same volume of port spec. Larger port diameter = longer vent, so you are thinking correctly.

Later,
Wolf

[Kevin K.]

One other question about down firing the port... if my internal box height is 8.5 inches, and I'm using 3/4 MDF... that 9 inch port will only have 1/4" of breathing room near the top of the box... Is that enough? I'm under the impression I need at least an inch or two of flow space to avoid some odd wall effects in the port behavior. Please educate me!

No, 1/4" of breathing room for that port would not be enough. I believe the general rule of thumb is at least the internal port diameter away from the wall. It could be a down firing port and still use an elbow. You could also look at using standard PVC and possibly even using two or more elbows. Good luck!

[KEtheredge87]

Nice work. I'm with Tom, do away with the sub-divider, it's just adding unnecessary additional length. It looks like you have enough room to shift the woofer a little off center (diagonally) and down fire the port also if you wanted to look at that option. Do you have a port in hand to confirm what you will use for the elbow?

One other question about down firing the port... if my internal box height is 8.5 inches, and I'm using 3/4 MDF... that 9 inch port will only have 1/4" of breathing room near the top of the box... Is that enough? I'm under the impression I need at least an inch or two of flow space to avoid some odd wall effects in the port behavior. Please educate me!

[KEtheredge87]

Nice work. I'm with Tom, do away with the sub-divider, it's just adding unnecessary additional length. It looks like you have enough room to shift the woofer a little off center (diagonally) and down fire the port also if you wanted to look at that option. Do you have a port in hand to confirm what you will use for the elbow?

Thanks Kevin and Tom Z! I have already iterated the design and have gotten rid of the extra divider... sometimes I don't do my best design work at 12 midnight (go figure).

Kevin, to answer your question I don't have ports in-hand to make sure I can do what I've designed. I'm about to order some parts to build five Heliums to go with this sub, so I'll get the SA70, driver, and ports while I'm at it. From there I'm hoping some creativity with PVC elbows at Lowes will do the trick.

Otherwise, I am a bit confused on the port itself... I found this build thread that used a totally different port, with supposedly good results:
http://techtalk.parts-express.com/fo...234#post975234

I don't understand how this guy used a 3' I.D. x 4.5" long port and got the right tuning out of the box. Am I missing something?

Edit: The picture comment was too long. I was talking about how I had to angle the port downward a bit after shortening the box and removing the cabinet divider. The shorter length was cramming the internal port opening against the front wall of the box.

[Kevin K.]

Nice work. I'm with Tom, do away with the sub-divider, it's just adding unnecessary additional length. It looks like you have enough room to shift the woofer a little off center (diagonally) and down fire the port also if you wanted to look at that option. Do you have a port in hand to confirm what you will use for the elbow?

[tomzarbo]

Looks great. Since the amp has a built-in air tight chamber, you could make it even more compact by eliminating the sub enclosure in your cabinet if you wanted to. That amp will handle that just fine. Cool looking design!

TomZ

[KEtheredge87]

Hi Everyone,

As promised, I put together a Voxel design that's geared toward down firing the woofer and including the Dayton SA70 amp in the rear of the setup. The plate amp is contained in its own little subcavity, while the main cavity is holding the Tang Band W5-1138SMF subwoofer. The internal dimensions of the ported cavity are 7 7/8" x 7 x 8.5 (LxWxH), giving me a volume of 468.56 in^3, or ~0.271 ft^3. Paul's original design used 0.2705 ft^3, so I'd wager I'm close enough.

The only way I could make this work was including a 90 degree bend in the port. I am still planning to use the same vents that Paul suggested for a total center line length of 9 inches, but I'll have to cobble something special together with a PVC elbow. I think I am ok from a port design perspective with almost 1 3/4" between the internal port flare and the interior walls. If additional space is required there, I can always angle that section of the bend toward a 45 degree angle thorough the cabinet.

Additionally, the internal volume's height and width of 8.5" and 7" were dictated by the SA70 plate amp's outside dimensions... Any smaller and my fit would be way too tight for comfort, or I'd have mounting flange overhanging the cabinet (not a good look!)

Finally, I added some 2 inch standoffs to the bottom of the cabinet to keep the woofer high enough off the floor.

Please let me know what you all think! I've got a bit of time before I start building this guy, so I can make design improvements if I did something silly.

Thanks!
Keith

[Kevin K.]

Like this ... seems to only work when your account is set to "posts", not latest activity.

http://techtalk.parts-express.com/fo...33#post1303933

Your right, it doesn't show a post number when your are viewing "LATEST ACTIVITY", didn't realize that. Always have mine set to "POST" but that's just a personal preference, I'm sure there are others like yourself that use "LATEST ACTIVITY". It would be nice if PE offered a more detailed "HELP" section on the forum, seems they only cover the basics.

[Millstonemike]

Like this ... seems to only work when your account is set to "posts", not latest activity.

http://techtalk.parts-express.com/fo...33#post1303933

[Kevin K.]

Could you share ...

Sure Mike. Right click on the actual post number and "copy shortcut". This creates a link to the thread and specific post that you can then paste into the thread you are commenting in.

[Millstonemike]

Figured it out today Paul, sorry to bother you with something so trivial. Still trying to learn the "in's and out's" of the new forum software.

Could you share ...

[Kevin K.]

Paul, could you explain how you linked the specific post in the thread? All I know how to do is copy the link to the entire thread, but you have demonstrated another skill entirely. Looks useful and I would love to know how. Thanks

Figured it out today Paul, sorry to bother you with something so trivial. Still trying to learn the "in's and out's" of the new forum software.

[KEtheredge87]

OK guys, I have a question on the port arrangement for the Voxel. After getting inspired by Kevin's version of the Voxel, I spent some time CAD modeling a downfiring version with a second chamber to hold the dayton SA70 amp. Kevin's model is well made and very space efficient, but I like the idea of the amplifier knobs and connections coming from the rear instead of the side.

don't have a picture of the model in progress, but the ported chamber internal dimensions were 7" wide x either 8.5" or 8 3/4" tall x 10" deep. I assumed 3/4 MDF as the material. Unfortunately that internal volume is too big compared to Paul's original design. I need to trim that depth in to shrink the volume, but I run into the 9" long port that was prescribed. I also considered trimming the width and height dimensions, but either will stop me from mounting the SA70 amp on the back.

I'm wondering if fitting some kind of PVC pipe elbow into the ports to deal with my chamber depth issue would adversely affect performance? I'd have to lay it out and do some fairly accurate centerline length measurements to ensure the same overall port length is achieved, but if the internal port flare is somehow pointed at the back side of the driver, will that funnel the sound out of the cabinet more than intended?

This is my first attempt at a ported subwoofer cabinet, so if there are ground rules of porting that I'm missing, please let me know!

Also, once I have a completed sketchup model that actually works, I'm happy to share with the group for feedback and for anyone to use.

[Kevin K.]

http://techtalk.parts-express.com/fo...02#post1087402

Kevin pretty much nailed it there.

Paul, could you explain how you linked the specific post in the thread? All I know how to do is copy the link to the entire thread, but you have demonstrated another skill entirely. Looks useful and I would love to know how. Thanks

[Kevin K.]

Yikes, I forgot about that, I do remember seeing that awhile back. Nice!
TomZ

So, I'm not the only forgetful one huh?(inside joke fellas)

I was shocked after seeing the original post date, hard to believe over a year has gone by since then. My how time flies when your having fun!