The V.B.S.S. DIY subwoofer design thread - Page 28 - AVS Forum | Home Theater Discussions And Reviews
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post #811 of 1704 Old 05-05-2018, 07:09 PM
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Quote:
Originally Posted by Samps View Post
With a 31hz tune, the 460s will be hard to beat for the money with music. There are certainly better 18s available, but not for $90. So if your funds are tight, you can't go wrong. Stepping up to the B&C RBX18s would be an upgrade in either max spl or smaller cab, but they are of course more expensive. 31hz is near perfect for the 460s, but they will create more air velocity with that tune. I'm not sure if Matt ever did any chuffing tests at 31hz.
Pretty new to this, but, wouldn’t port chuffing be determined/ reduced by actual port area ? Isn’t that what controls chuffing/ port noise, then port length determines tuning frequency ?
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post #812 of 1704 Old 05-05-2018, 07:19 PM
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If you keep the port area the same, port velocity will go down the lower you tune the cab. I'm not sure of the physics, but you can see this in winisd models.
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post #813 of 1704 Old 05-05-2018, 07:32 PM
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Here's a quick model to illustrate the lower velocity at the lower tune:

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post #814 of 1704 Old 05-05-2018, 08:29 PM
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I see that. But, I was thinking about different port areas for the same tuning. I’m pretty sure, generally, a smaller port area would require a longer port for the same tune as a larger port area with a shorter port. Seems like, the larger port area sub would have less air velocity at the port, which would reduce port noise. Am I on the right track here or is it more complicated than that ?
Sorry about the newbie question, but I’m trying to learn here. John ( LTD02 ) has helped me understand quite a bit through his helping me with my enclosure design. But I still have a lot more to learn.
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post #815 of 1704 Old 05-05-2018, 09:26 PM
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Is there a way I can block this thread so I can stop wanting these so bad?????
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post #816 of 1704 Old 05-05-2018, 10:36 PM - Thread Starter
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Powered with the inuke 3000 port chuffing isn't a problem with the dual 4" precision ports with either the 20hz or 31hz tuning.

In the standard design the 31hz tune is achieved by removing the center tube section on the two ports effectively placing the external and internal flares end to end.
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post #817 of 1704 Old 05-06-2018, 12:09 AM
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Quote:
Originally Posted by mtg90 View Post
Powered with the inuke 3000 port chuffing isn't a problem with the dual 4" precision ports
Interesting. I thought these were happy as can be on a 1000? Mine sure is. Gonna add another. Are you implying there's a problem with less power?
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post #818 of 1704 Old 05-06-2018, 06:13 AM
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Quote:
Originally Posted by tk123 View Post
I see that. But, I was thinking about different port areas for the same tuning. I’m pretty sure, generally, a smaller port area would require a longer port for the same tune as a larger port area with a shorter port. Seems like, the larger port area sub would have less air velocity at the port, which would reduce port noise. Am I on the right track here or is it more complicated than that ?
Sorry about the newbie question, but I’m trying to learn here. John ( LTD02 ) has helped me understand quite a bit through his helping me with my enclosure design. But I still have a lot more to learn.
You are correct. There is a big difference between port area and port volume. I thought you were planning to keep the 4 inch tube ports, which would keep the same port area regardless of tune. With a slot port you can adjust accordingly.

The 1000dsp is fine for a pair of 460s bridged. The 3000dsp can squeeze a little more out of them, but not much.
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post #819 of 1704 Old 05-06-2018, 07:17 AM
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I have a spare Adcom GFA 555. When bridged at 4 ohm it's 850RMS. Could two of these handle that OK? My 15s do great with the rumble, but I want more tactical chest thumping punch.
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post #820 of 1704 Old 05-06-2018, 08:05 AM
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If it really does 850 or anywhere near that, then that should work well.
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post #821 of 1704 Old 05-06-2018, 08:27 AM
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I assure you, they do. And it's a conservative rating. https://kenrockwell.com/audio/adcom/gfa-555-ii.htm
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post #822 of 1704 Old 05-08-2018, 08:42 PM
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Quote:
Originally Posted by LTD02 View Post
31Hz Version
For the 31Hz mode version, everything is the same except the bottom port board is 10.50" long. There is no vertical port board in the 31hz version. Stuffing one port in the 31Hz version tunes the cab to about 22Hz.

sometimes, things just work out. it just barely fits on one sheet of 48x96 ply (mdf tends to give an extra inch to allow for banged up corners in transport, so at 49x97 there is plenty of room on that too).




Is there any chance you work up a cut list for TWO, 31hz tuned cabinets from (4) pieces of MDF that were pre-cut to 48"x48"? Would it fit?

Thanks
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post #823 of 1704 Old 05-09-2018, 08:24 AM
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Quote:
Originally Posted by Craig S King View Post
Is there any chance you work up a cut list for TWO, 31hz tuned cabinets from (4) pieces of MDF that were pre-cut to 48"x48"? Would it fit?

Thanks
check out this site: http://workshop-buddy.com/cut-optimi...alculator.html
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post #824 of 1704 Old 05-09-2018, 09:30 AM
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Quote:
Originally Posted by Craig S King View Post
Is there any chance you work up a cut list for TWO, 31hz tuned cabinets from (4) pieces of MDF that were pre-cut to 48"x48"? Would it fit?

Thanks
It will take 5 sheets 48x48 to build two sub boxes.
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post #825 of 1704 Old 05-09-2018, 09:04 PM
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Originally Posted by BCRSS View Post
It will take 5 sheets 48x48 to build two sub boxes.
Ok, thanks for checking. I didn't know if maybe when building two boxes, you could weasel some different pieces out of a 48"x48" section and still have enough. It's OK though, I just normally have Lowes cut my 4'x8' MDF sheets to 48"x48" for ease of getting it through my table saw. It looks like I'll just have the two sheets cut unequally in half.

And the good news is, I still have a 24"x48" section of MDF leftover from my mini-marty build for extra too.
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post #826 of 1704 Old 05-10-2018, 09:34 PM
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Quote:
Originally Posted by Craig S King View Post
Is there any chance you work up a cut list for TWO, 31hz tuned cabinets from (4) pieces of MDF that were pre-cut to 48"x48"? Would it fit?

Thanks
sometimes you get a question in your head and it won't go away. :-)


with this arrangement of 49 x 97 MDF (with MDF they typically give you an extra inch in each dimension), there are two 2" borders running through the board. This would allow the guy at the store plenty of room to miss his target +/- (if he doesn't make a precise cut) and still not mess up the build.


first cut from left is at 32.50" (the panels are 31.50" wide in the image).


second cut is 23.00" (the baffle is 22" wide).


that leaves a middle piece that is 41.50" (the panels in the middle need about 38.00" and change, so there is over 3" of excess there too).


so even better than 48x48. :-)


32.50" x 49"
23.00" x 49"
41.50" x 49"

















that seems much easier to work with for sure.
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post #827 of 1704 Old 05-11-2018, 04:18 AM
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Hey John. This is exactly how I’ll be doing mine that you helped me with. I just had to figure out how the pieces would best fit on a full sheet. Then decide what lengths to have the store cut Easy as cake.
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post #828 of 1704 Old 05-11-2018, 11:02 AM
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Thanks LTD02 for the revised cut list. I guess I should've specified - since I'm doing the 31hz version, I will only need one piece for the port, 10.5x22. And I still have leftover pieces from my mini-marty build 2 months ago, so the pieces for braces are already set aside.

My thought is, since I'm only going to have one panel for the port, I could possibly fit both port panels on one sheet, then with the leftover extra space on the second sheet of MDF, I could squeeze double baffle pieces. And although 1.5" thickness is probably overkill for the PA460, I wanted to see if it would fit.
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post #829 of 1704 Old 05-14-2018, 06:12 AM
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Okay quick questions I want to rebuild my VBSS because i love them so much but when i had them built last summer the builder used Plywood & i really don't like the finish. So I'm going to build them myself four boxes which look straight forward but i have a few questions.

1. Do i need to double baffle if I'm going to flush mount the speaker & ports ?

2. How do you cut the flush mount for the subs & ports.

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post #830 of 1704 Old 05-14-2018, 01:32 PM
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Quote:
Originally Posted by Nexgen76 View Post
Okay quick questions I want to rebuild my VBSS because i love them so much but when i had them built last summer the builder used Plywood & i really don't like the finish. So I'm going to build them myself four boxes which look straight forward but i have a few questions.

1. Do i need to double baffle if I'm going to flush mount the speaker & ports ?

2. How do you cut the flush mount for the subs & ports.
A double baffle is not required to flush mount the sub but I would definitely use 3/4in material and probably glue some plywood pieces behind where the screws will go so you have extra material to bite into. I've flush mounted speakers 2 ways. First way was I cut the hole and used a rabetting bit on the router to create the flush mount depth. Second way was to take a 3/4 straight router bit to set my flush cut depth, then a 1/4 bit to cut my hole. Hope that helps.

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post #831 of 1704 Old 05-14-2018, 03:47 PM
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Quote:
Originally Posted by Nexgen76 View Post
Okay quick questions I want to rebuild my VBSS because i love them so much but when i had them built last summer the builder used Plywood & i really don't like the finish. So I'm going to build them myself four boxes which look straight forward but i have a few questions.

1. Do i need to double baffle if I'm going to flush mount the speaker & ports ?
I used 1/2" MDF for the second baffle on my build, which is just about exactly flush with the driver. So with that math, if you don't do a second baffle you'll only have 1/4" of material to screw the driver into.

Either do the second baffle or make sure you add scrap pieces on the inside of the single baffle as MW6006 mentioned.

Quote:
Originally Posted by Nexgen76
2. How do you cut the flush mount for the subs & ports.
Plunge router and a circle jig.

I didn't for the port and am now regretting it. I would have rigged up a circle jig for my laminate trimmer, cut the outer diameter to flush depth, adjust and then cut the 6.25" diameter all the way through.

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post #832 of 1704 Old 05-14-2018, 05:14 PM
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I assure you, they do. And it's a conservative rating. https://kenrockwell.com/audio/adcom/gfa-555-ii.htm
Don't use that link - my antivirus picked up ugly stuff from that link!
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post #833 of 1704 Old 05-15-2018, 12:01 PM
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OP says that having the ports so close to the rear of the cabinet increases bass response. Does that imply that NOT flush mounting the ports when using a double baffle decreases bass response? Doing so moves the ports away from the rear by 1/2".
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post #834 of 1704 Old 05-15-2018, 02:59 PM - Thread Starter
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1/2" won't make much difference there, at least not enough to really matter.
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post #835 of 1704 Old 05-15-2018, 08:39 PM
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Don't use that link - my antivirus picked up ugly stuff from that link!
Not sure why, it's been around for a very long time and a lot of Adcom guys have posted it on various sites.
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post #836 of 1704 Old 05-18-2018, 02:39 PM
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Would I need an Inuke with DSP if my receiver (NAD 758v3) has Dirac Live in it ?

I'm trying to figure out my budget at this point.

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post #837 of 1704 Old 05-18-2018, 08:57 PM
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Yes. The VBSS uses the DSP to optimize/protect the PA460's and also to get the different tuning options.
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post #838 of 1704 Old 05-19-2018, 11:23 AM
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[QUOTE=LTD02;56120796]I received a question about a slot ported version. I can't recall if one has already been drawn up or not. The OP mentions port dimensions, which seem about right.
The recessed driver option is gone because the panel wouldn't sit flush with the slot port. I resized several of the panels as well, so while this looks the same and will perform pretty much the same, it is a little different than the VBSS.

20Hz version
The 20Hz version has a port that goes across the bottom of the cabinet and then a little up the back of the cabinet. Tuning would be around 20hz with both ports open and about 15hz one port stuffed.

Baffle 27.75" x 22.00"
Rear 30.00" x 22.00"
Sides (2) 31.50" x 20.00"
Top 20.00" x 22.00"
Bottom 20.00" x 22.00"
Port boards:
horizontal 17.75" x 22.00"
vertical 8.00" x 22.00"
Port braces:
horizontal 19.25" x 1.50"
vertical 8.75" x 1.50"

Internal bracing required


31Hz Version
For the 31Hz mode version, everything is the same except the bottom port board is 10.50" long. There is no vertical port board in the 31hz version. Stuffing one port in the 31Hz version tunes the cab to about 22Hz.


Just so I understand correctly, the 31hz version is identical to the 20hz version, except the 8" vertical board in the rear is excluded, and the bottom 17 3/4" board is now only 10 1/2". Is this correct?

Also, I have a inuke 6000 dsp. I realize that it is overkill for two 460s, but as long as I limit the output the drivers should be safe, right?

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post #839 of 1704 Old 05-19-2018, 08:22 PM
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https://imgur.com/gallery/byXYSUz
My modified PA460 enclosure in the works. Big thanks to LTD02 for all his time and experience in helping me with the design.
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post #840 of 1704 Old 05-19-2018, 09:38 PM
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Quote:
Originally Posted by tk123 View Post
https://imgur.com/gallery/byXYSUz
My modified PA460 enclosure in the works. Big thanks to LTD02 for all his time and experience in helping me with the design.
Is that the design the one tuned for 31hz? It looks it. Is that top port voard 10 1/5?
And what is the hole in the side for?
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