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mtg90 11-29-2015 04:16 PM

The V.B.S.S. DIY subwoofer design thread
 
10 Attachment(s)
Official Value Buster Subwoofer System design info thread.

As the title implies this design allows you to get lots of bass from an inexpensive driver an easy to build enclosure with flexible tuning and allow for multiples to be powered from a single iNuke amp (or NX series which has replaced the iNukes).

https://www.avsforum.com/forum/attac...1&d=1448853198

The driver for this design is the Dayton PA460-8, an odd choice for a subwoofer design you might say. True, but with the right balance of enclosure, power and proper EQ it does amazingly well. Similar to the Magnum-12 woofer in the Flex-12 the PA460 is very efficient in the mid bass leading to very little thermal compression and great dynamics in that range. While it is a bit limited in terms of coil overhang it does have a very soft suspension and decent mechanical clearances so there is no trouble pushing it a bit at lower frequencies. I have done thorough testing with the iNuke 3000 and the driver stays safe even when driven hard below tuning with the DSP settings limiting any bad noises from either the driver or the amp when being pushed hard into the limiter as was demonstrated at ENG-399's where a pair was run at reference with the sub trim about 16dB hot.

The enclosure is a fairly straightforward ported box, approximately 6.25 cubic feet net internal. Measures 23.5" wide, 31.5" tall x 20" deep or 20.5" deep if you add an additional 1/2" baffle layer to flush mount the driver. If going with a single baffle layer and surface mounting the enclosure can be cut from a single 4x8' 3/4" sheet of MDF or plywood. Add a 2x4' sheet of 1/2" if you want to flush mount the drivers and ports which is how I built mine.

https://www.avsforum.com/forum/attac...1&d=1448853198

Here is the cultist for the enclosure without the additional 1/2" front baffle to flush mount the driver and ports. To flush mount the driver all you need to do is cut the outer diameter out of the 1/2" baffle and that will put it flush. Theoretically you could add the second baffle layer at any time without making a new box or adjusting the cuts on the inner baffle.

https://www.avsforum.com/forum/attac...1&d=1448853198


Note 30" x 2" piece should be cut into smaller pieces to fit between the side to side and top to bottom bracing, I just forgot the exact dimensions which making the cultist. It should be measured during assembly anyway to determine exact length of parts needed.

https://www.avsforum.com/forum/attac...1&d=1448853198

Here is a look at the bracing I used, feel free to add more or beef it up if you wish, but I found that to be adequate:
https://www.avsforum.com/forum/attac...1&d=1448853198

Damping:
I used R-13 recycled denim/cotton insulation with a piece placed on top the port tubes below the driver that is held in by the brace and a couple pieces placed on the walls above and behind the driver leaving space above the ports for airflow. Fiberglass, polyfil or acoustic foam would also be suitable if similarly placed.

https://www.avsforum.com/forum/attac...1&d=1448853198

Ports
The design uses two of the 4" precision ports at full length (17") which makes things very easy. Using both at full length gives you a 20 Hz tuning, if one is plugged you get 15 Hz and if you remove the center extension tubes placing the flares end to end (5" length) you get a 31 Hz tune. If using 4" ports without large flares you would want them to be about 3.5-4" long to give you the 31Hz tune. You can use masking, duct or electrical tape to hold the precision ports together if you want to leave open the option of removing the port extension tube. The proximity of the internal port flare to the rear wall makes the effective port length longer then it would be otherwise which allows for the tuning to come in lower then what it looks like it should calculate out to. For this reason modification of the depth of the enclosure will change the port tuning, you can however change the height and width keeping if internal volume is kept the same or within 10%.

Slot Port Cabinet Options
If a slot port is desired you can build it with a full width slot port that is 1.5" high x 28" long to give you the 20Hz tune. If you add a brace down the middle it will also allow for both the 20hz tune with both halves of the port open or the 15hz tune if one of the halves was closed off.

If just the 15Hz tune is desired then the slot port can be 1" high, full width (22") and 32" long which reduces port velocity and compression compared to the 15Hz mode of the dual tune option. To visualize these adjustments to the below 3d model (showing the 20Hz option) you only need to change the internal slot port panels to 17.5" (from 17") and 14" (from 10") and the height to 1" (instead of 1.5").

If the 31Hz mode is desired build it can be 1.5" high x 8" long, so you only need a single 22" wide x 7.25" long panel to make the slot port.

https://lh3.googleusercontent.com/sB...=w1216-h836-no

Amplifiers
The VBSS was intended to be used in conjunction with the iNuke/NX 1000DSP or 3000DSP amps. A 1000 can power up to two of these in bridged mode while the 3000 can drive four per channel for a total of eight. This allows you can get a lot of bass without spending big bucks and a rack filled with subwoofer amplifiers. Other amplifiers could be used but there would be a need for external DSP (settings provided) and you would loose the precise tuning of the limiter designed for the Inuke/NX series amps to get the most from the driver/amp combo.

Here is a look at the outdoor 2pi frequency response for the 15hz, 20hz and 31hz modes (with DSP):
https://www.avsforum.com/forum/attac...1&d=1448853198

Rough idea of the 2pi max output from a single enclosure powered by an iNuke/NX 3000.
Note in reality the 15hz mode does suffer from some port compression which will eat up a few dB near port tune at high output levels:

https://www.avsforum.com/forum/attac...1&d=1448853198


A zip file with the DSP settings for the iNuke amps is also attached.

*If you have a Behringer NX series amplifer with DSP just change the .arp file extension to .nxp to get them to load in the new software*

Bburnett 11-29-2015 04:37 PM

At least for me, the images are not displaying.

Nate Hansen 11-29-2015 05:18 PM

Yeah, no pics here either.

eng-399 11-29-2015 05:23 PM

11 HZ. Hope the video link works

mtg90 11-29-2015 07:21 PM

When I hit preview post when creating the thread it deleted all my image attachments but I still saw the images so I thought everything was good.

I went ahead and added them back in with new links, are they fixed now?

383-s-10 11-29-2015 07:24 PM

Pics work now, thanks! What would the response look like without DSP?

Reckless95 11-29-2015 08:48 PM

I have 2 of these drivers in a very small dual opposed enclosure. This may be it. :eek:

jkkwaz 11-29-2015 09:59 PM

Are there iNuke settings that you can post at some point?

383-s-10 11-29-2015 11:43 PM

Quote:

Originally Posted by jkkwaz (Post 39341442)
Are there iNuke settings that you can post at some point?

They are in the attached zip file at the end of the original post.

Bburnett 11-30-2015 12:01 PM

mtg90 - Since the PA460 is very efficient in the mid bass, can you offer an opinion on an enclosure size that would maximize the benefits on the PA460 used in a mid bass application ranging from something like 60Hz to 400Hz?

nnoble83 12-01-2015 02:34 PM

How do feel this would perform downfiring?

kgveteran 12-01-2015 03:32 PM

1 Attachment(s)
You certainly cross your T's and dot your i's......Quite an offering !

LTD02 12-02-2015 01:27 AM

2 Attachment(s)
pretty cool.


one question about the dsp: why employ the dynamic eq and not just a combination of peq and the regular limiter?


with the dynamic eq, the response will change at each level of output, something very roughly like this:


https://www.avsforum.com/forum/attach...1&d=1449047800


where as with just eq'ing the sub flat and running it until it hits the voltage limit would give something that looks kind of like this (very roughly for illustration of the point only):


https://www.avsforum.com/forum/attach...1&d=1449048246

chrapladm 12-02-2015 02:11 AM

What are the mechanical limits on the Dayton?

I ask because I saw Xmax was about 6mm but saw the 11hz video.

eng-399 12-02-2015 07:01 AM

Another 11 HZ video clip the 3 voices are me Saying 11 HZ shadyj laughing and Matt talking about the sub hope the video link works.
They did play loud in my room. I would love to see someone with 8 of these.

LTD02 12-02-2015 08:47 AM

1 Attachment(s)
Quote:

Originally Posted by chrapladm (Post 39402538)
What are the mechanical limits on the Dayton?

I ask because I saw Xmax was about 6mm but saw the 11hz video.


good question. I inquired about that at p.e. the tech indicated 6mm is overhang only. he said he would refer my question to 'dayton' for confirmation and/or more info, but I never heard back.

edit:

mtg90 indicates the top plate is about 7.6mm.

xmax should include roughly a third of the gap, which is about 2.53mm, so 6+2.53 = 8.53mm.

"usable" should be somewhere around 1/2 to 2/3 into the gap, or about 6+5.06= 11.06mm.

the coil would leave the gap at around 6+7.6= 13.6mm.

as matt (mtg90) noted, xmech (the damage point) is around 20mm.

~50 volts pushes the driver to about 11mm in 20hz tuning winisd model, so with a little less excursion in reality than in model because of non-linear effects, that appears to be just about enough to push the coil toward the edge of the gap.


https://www.avsforum.com/forum/attach...1&d=1449076701



http://www.daytonaudio.com/specs/spe...p?prod=295-036

chrapladm 12-02-2015 01:27 PM

Thanks LTD. I do believe the video has one port plugged for a 15hz tune but that doesnt change much.

383-s-10 12-02-2015 03:33 PM

1 Attachment(s)
Busy weekend ahead! Got the parts to build one for my father's garage/bar/basement.

Still interested in what the expected response would be without DSP... Will be powering with a plate amp from an infinity sub he has for now and determine if he wants to buy an iNuke...

LTD02 12-02-2015 08:15 PM

Quote:

Originally Posted by 383-s-10 (Post 39422650)
Busy weekend ahead! Got the parts to build one for my father's garage/bar/basement.

Still interested in what the expected response would be without DSP... Will be powering with a plate amp from an infinity sub he has for now and determine if he wants to buy an iNuke...


cool.


it will be a rising response, sort of like the top red line in post 13.

mtg90 12-03-2015 10:04 PM

Quote:

Originally Posted by LTD02 (Post 39402354)
pretty cool.


one question about the dsp: why employ the dynamic eq and not just a combination of peq and the regular limiter?


with the dynamic eq, the response will change at each level of output, something very roughly like this:


https://www.avsforum.com/forum/attach...1&d=1449047800


where as with just eq'ing the sub flat and running it until it hits the voltage limit would give something that looks kind of like this (very roughly for illustration of the point only):


https://www.avsforum.com/forum/attach...1&d=1449048246

Sorry I have been busy, did not get a chance to respond earlier in the week.

The dynamic EQ is not quite that severe. It starts to engage slowly when the level at about -8dB (from limiter) and by the time it hits the limiter overall reduction in the filter value is about 6dB. Basically it allows to top end to expand further before the limiter activates and clamps down out output. It also gives the perception of having more gas in the tank being able to increase the volume that 6db before seeing the limiter lights activate.

The -36dB threshold value is not indicative of max output but I believe it has to do with the capability of the DSP and max output voltage of the DAC. Amp clipping on the 3000 occurs somewhere in the -30 to -20dB range on that scale. Turning the threshold down below -20dB results in no change from the DEQ up to clipping so setting it at say 0dB would be the same as using a regular PEQ filter.

The other filter is at -60dB and because it is negative gain it stays on the whole time (like a PEQ filter). I am using the DEQ block because I figure most will not play with the DEQ settings and I wanted to leave as many of the regular PEQ filters free as I could manage. It could be moved to one of the PEQ slots if someone wanted to use another DEQ for something.

LTD02 12-04-2015 10:29 AM

Quote:

Originally Posted by mtg90 (Post 39461010)


...

The -36dB threshold value is not indicative of max output but I believe it has to do with the capability of the DSP and max output voltage of the DAC. Amp clipping on the 3000 occurs somewhere in the -30 to -20dB range on that scale. Turning the threshold down below -20dB results in no change from the DEQ up to clipping so setting it at say 0dB would be the same as using a regular PEQ filter.


ahhh. thanks for the clarification. i was under the impression that 0db was with respect to full voltage. lol. behringer!?

Quote:

Originally Posted by mtg90 (Post 39461010)
The other filter is at -60dB and because it is negative gain it stays on the whole time (like a PEQ filter). I am using the DEQ block because I figure most will not play with the DEQ settings and I wanted to leave as many of the regular PEQ filters free as I could manage. It could be moved to one of the PEQ slots if someone wanted to use another DEQ for something.


:-) that makes sense.

chadamir 12-04-2015 11:19 AM

How is the thd?

mtg90 12-05-2015 07:58 PM

I did not get a chance to test distortion when the weather was good.

Quote:

Originally Posted by LTD02 (Post 39409378)
good question. I inquired about that at p.e. the tech indicated 6mm is overhang only. he said he would refer my question to 'dayton' for confirmation and/or more info, but I never heard back.


edit:


looks like the top plate is about 4mm.


xmax should include roughly a third of the gap, which is about 1.33mm, so 6+1.33 = 7.33mm.


"usable" should be somewhere around 1/2 to 2/3 into the gap, or about 6+2.66 = 8.66mm.


the coil would leave the gap at around 6+4= 10mm.


~50 volts pushes the driver to about 11mm in 20hz tuning winisd model, so with a little less excursion in reality than in model because of non-linear effects, that appears to be just about enough to push the coil to the edge of the gap.


https://www.avsforum.com/forum/attach...1&d=1449076701




http://www.daytonaudio.com/specs/spe...p?prod=295-036

I was able to grab a few measurements for you.

Top plate is 0.3 inches or 7.62mm.

I also measured inward xmech (bottom) at 20mm so it has some wiggle room.


Since I had my jig setup I also took some measurements of HT18 D2 I have just for kicks. This is one of the last few blowout HT-18 D2 drivers that were sold. Since it has an opening above the top plate I can get a look at a few more things.

Inward xmech was ~30mm, at first I thought it was former on back plate but upon further investigation it was found to be a glue joint under the spider hitting the top plate.

The VC length is about 43mm. Top plate is 7/16" which gives roughly 16mm overhang. Interestingly my driver has a 4mm outward offset of the coil, ~20mm above the gap, ~12mm below!

eng-399 12-05-2015 10:17 PM

@cuzed2 I'm open for helping building boxes for these if you need any help Let me know it would be fun.

chrapladm 12-05-2015 10:32 PM

Well 20mm is more than I thought it would be. I was looking at doing something like this with a BC PS100 but I believe the Xmech was only 11mm which is a bit scary. 20mm is much easier to work with in case of accidents. Will have to do some more simulating now.

cuzed2 12-06-2015 07:45 AM

Quote:

Originally Posted by eng-399 (Post 39512730)
@cuzed2 I'm open for helping building boxes for these if you need any help Let me know it would be fun.

Mike,
Thanks - appreciate the offer. I just might take you up on it. If I go down this road it will be after the holidays

LTD02 12-06-2015 09:59 AM

Quote:

Originally Posted by mtg90 (Post 39510714)
I was able to grab a few measurements for you.

Top plate is 0.3 inches or 7.62mm.

I also measured inward xmech (bottom) at 20mm so it has some wiggle room.


fantastic! that's quite a bit of driver for $90.


does it appear that the 6mm spec is voice coil overhang?

LTD02 12-06-2015 10:10 AM

Quote:

Originally Posted by chrapladm (Post 39512906)
Well 20mm is more than I thought it would be. I was looking at doing something like this with a BC PS100 but I believe the Xmech was only 11mm which is a bit scary.
...


sounds pretty low for that driver. do you recall the source? the coil is 21 and the gap is 11. it has a pretty good rep and if the damage point was with the coil still half in the gap, it wouldn't seem like it would be holding up all that well.

chrapladm 12-06-2015 01:00 PM

I asked the company that has a custom one made for them what the limits were and that is what they told me. I thought it didnt sound right but want too worried about it anyways. I was going to use the PS100 for a bass section of a 3 way. BUT the custom one I looked at using if thats all the room it has I will pass. SO I might have to look up this information again. The PS100 and their (Krix) custom driver should have the same Xmax and mechanical limits. They just had Qe/Qms and Fs tweaked a bit.

Everything I have ever bought from BC has always had plenty of room past Xmax. SO this kind of threw me when I heard 11mm also.

And these Daytons do seem like one awesome deal for only 90 dollars.Wow

mtg90 12-06-2015 01:28 PM

It was a bit harder to see the voice coil on the PA460 without any venting under the spider, though I found it is possible to look through the spider with a bright flashlight.

Looking at it more the top plate could be 7.5mm rather then 0.3 inches, which makes more sense for metric dimensions. Though we are literally splitting hairs at that point (<0.005").

The coil height looks to be roughly 19mm which gives an overhang of 5.75mm if using the 7.5mm gap height. Though I am sure there is some margin of error in my measurements because I can't get a super clear view looking through the spider. It could easily be 19.5mm which give 6mm of coil overhang.


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