# DIY PB12-ISD Subwoofer



## kaang (Apr 26, 2008)

rbartyczak said:


> Information for the DIY Subwoofer Database:
> Driver: SVS DB12 - 12"
> Enclosure type: Sonotube - 20" diameter/36" height
> Enclosure volume: 5.75 cu. ft/163 liters
> ...


 I've had the DIY subwoofer bug for awhile and have been looking at drivers. I have a modest 5.1 system, with an old 10" Fostex Subwoofer that I put a 300W BASH sub amp into. On a tight budget and want to improve on the Fostex. I found a 12-inch woofer from a SV Sound PB12-Plus subwoofer where the owner upgraded to the Gen 2 woofer and is now selling the original on Craigslist for $25. I looks nice - cast frame, paper cone (not aluminum), foam surround. I don't know if it is dB12.2 or dB12.1.

My questions revolve around knowing how to design the proper enclosure and port(s) if we don't know the TSP's. I done a little homework and it looks like the folks at SVS have been fairly generous in providing enclosure and port recommendations for the old drivers, in lieu of giving out the driver specs.

Once I look at / pickup the driver (why wouldn't I, SVS driver for $25?) perhaps I can supply more info. Also when I get past my 10 posts, I can post pics and links regarding this little project.

kaang


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## Mike P. (Apr 6, 2007)

Welcome kaang! It should be fairly easy to figure out the net volume needed by looking at the overall specs of the PB12-Plus. The PB12-Plus is 25" H x 18" W x 25" D and tuned to 20 hz with three 3 inch ports. Assuming the cabinet was built with 3/4 inch material, the internal dimensions would be 23.5 x 16.5 x 23.5 or 5.3 cubic feet. Subtract displacement for the ports, sub and bracing, the net volume would be around 4.8 cu.ft. Tuning could be accomplished with three 3 inch flared ports 27.5 inches long, or two 4 inch flared ports 32 inches long would also work.


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## kaang (Apr 26, 2008)

Thanks for the quick reply! I see that using a port size calculator does not require the driver parameters. The gentlman that I am buying the driver from replaced the driver with the newer model back in December 2006. He indicated that the enclosure dimensions are 20"L x 20"W x 18"D. Perhaps the enclosure volume is not as critical as is port tuning to enclosure size, understanding that the larger volumes provide better low bass performance.

I am actually thinking of copying the SVS 20-39 PC–Plus subwoofer using Sonotube. So as long as I properly calculate the internal volume and use a port calculation tool, you think this driver will perform properly?


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## Mike P. (Apr 6, 2007)

I got the dimensions from this link:

http://www.hometheaterhifi.com/volume_13_1/svs-pb12-plus-subwoofer-1-2006-part-1.html

You should verify from where you're buying this sub that it is indeed the PB12-Plus and find out if he made a mistake in the cabinet dimensions. Maybe there were two different PB12-Plus models and the cabinet sizes were different, I don't know. 



> Perhaps the enclosure volume is not as critical as is port tuning to enclosure size, understanding that the larger volumes provide better low bass performance


Enclosure volume is critical as this sub was meant to work in a specific size cabinet and it's important to find out what the original dimensions were. There can be a small variation in size without any ill effects as long as it's not too big of a difference.

Port tuning is dependant on cabinet volume only, the specific sub is dependant on the proper cabinet volume.


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## kaang (Apr 26, 2008)

I will likely meet the seller today. I have been trying to do some research on this driver. The link you provided shows the db12.2 driver. The driver looks like this:















So perhaps it is a db12.1? He indicated that it came out of a Model PB12-ISD purchased in 12/2005, so obviously the models have changed. This may all be mute. My seller offered to send an email to SVS asking for enclosure and port recommendations for this driver.


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## Mike P. (Apr 6, 2007)

Just goes to show proper identifcation is important. I can't find much info on the Model PB12-ISD. Hopefully someone will know something about it.


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## kaang (Apr 26, 2008)

Just picked this driver up for $20. What a deal! A little more research showed that it is the old 12" ISD driver that the 12" NSD driver replaced. If I can get the cylinder and port dimensions for the SVS 25-31PCi I think I'll be good. Anyone have that data? Thanks.


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## Robert_J (Aug 10, 2006)

The total height should be 38" based on the measurements from other SVS subs. The distance between the bottom of the sub and the floor plate is 2 or 3 inches. The port is a 4" diameter model from PSP-Inc. Use sonosub.exe from subwoofer-builder.com to figure out the rest.

If you want to try to design your own, you can use the T/S parameters from the Beyond Audio X-One 12". It's also the same T/S parameters used on the Blueprint 1202. Your driver and these 2 came from the same build house. TeamPSI (the seller in both links) is David Moore who worked at that build house and is now employed by Resonant Engineering. 

Disclaimer - The parameters are just a guess. Other than checking the parameters with Woofer Tester 3, this is as close as you will get. And I'm willing to run the tests if someone else pays shipping both ways.

-Robert


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## kaang (Apr 26, 2008)

Robert_J said:


> The total height should be 38" based on the measurements from other SVS subs. The distance between the bottom of the sub and the floor plate is 2 or 3 inches. The port is a 4" diameter model from PSP-Inc. Use sonosub.exe from subwoofer-builder to figure out the rest.


I did send an email to SVS and received some feedback from their renowned Support staff:

"We don't provide detailed/high level DIY support (we get about 20 questions/week on this subject), but we can point you in the right direction. :^) Use our 20-39 PCi as a model – it has a 16" diameter, has some fiberglass lining (but is not stuffed), is about 35" long, and the 4" port is about 15-16" long (including flares). That should get you in the ballpark for a 20 Hz tune with a critically damped response. Top it off with end-caps and you're off to the races." 



Robert_J said:


> If you want to try to design your own, you can use the T/S parameters from the Beyond Audio X-One 12". It's also the same T/S parameters used on the Blueprint 1202. Your driver and these 2 came from the same build house. TeamPSI (the seller in both links) is David Moore who worked at that build house and is now employed by Resonant Engineering.


The 12' Blueprint looks close. I also saw a 12" driver at Acoustic Elegance, the C12.2, but the specs are much different. In both cases they are dual VC and the SVS driver is a single VC.



Robert_J said:


> Disclaimer - The parameters are just a guess. Other than checking the parameters with Woofer Tester 3, this is as close as you will get. And I'm willing to run the tests if someone else pays shipping both ways.
> 
> -Robert


I appreciate the offer. I figure I would follow the SVS suggstions and calculated their suggested effective enclosure volume to be 3.956 cubic feet. I would use the 17" flared precision port and follow some the various Sonosub build threads here and elsewhere. Maybe soon I can have this thread moved to the project section.


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