# svs B12-Plus/4 specs



## Guest (Feb 20, 2008)

hello all,
i have a project i am about to start on soon. my brother upgraded his two SVS subs this past year to the newer 12.3 drivers and now has 4 of the older 12.2 drivers left over from the upgrade. he is more the home theater buff than i..(im still into 2 channel!) but my dedicated hobby is furniture/cabinet building and he wants me to build him a single sub enclosure from 1" mdf veneered to house the 4 subs. i was looking at building a enclosure that duplicates the pb12+2's that he already has..only stacked.. but would rather have a lower height and fewer ports. i found some pictures online of the b12-plus/4 which i gather hasnt been produced in sometime.. and it looks to be exactly what he is looking for. does anyone own one of these things? i was hoping to acquire the general specs to go on such as Length,width,and height and also port size and length. any help greatly appreciated. pleae feel free to contact me at [email protected]


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## Sheep (Feb 16, 2008)

That design is not as straight forward as you think. There is a cutout with an opening that is covered by a grill.

But to answer your question, I would just ask SVS, I'm sure they would help.

SheepStar


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## Mike P. (Apr 6, 2007)

It's not too difficult. The PB12-Plus/2 uses three 4 inch flared ports. What is required is finding out the net volume of the box.


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## mike c (Apr 25, 2006)

Mike P. said:


> It's not too difficult. The PB12-Plus/2 uses three 4 inch flared ports. What is required is finding out the net volume of the box.


and the port length.

but you will need to increase port area to accomodate twice the number of drivers to prevent port chuffing. and twice the port area means an even longer port. (that's if you want to keep the tuning of the plus/2)

try to contact Ed Mullen or Tom V of SVS. i'm sure they'll help you design your subwoofer.


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## Mike P. (Apr 6, 2007)

mike c said:


> and the port length.
> 
> but you will need to increase port area to accomodate twice the number of drivers to prevent port chuffing. and twice the port area means an even longer port. (that's if you want to keep the tuning of the plus/2)


2 times the amount of drivers would require a cabinet twice as big. Using the same tuning frequency, if you double the port area the port length remains the same.


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## Guest (Feb 20, 2008)

thanks guys for the input. i will try to reach someone at svs and see if they can assist in the port specs. construction wise im not too concerned about how detailed it is. i have built 2 sets of klipschorns and a set of lascalas that i would gather would be more involved than constructing this sub.i really have only been able to find one pic of this sub though..im wondering if i can locate someone who actually owns one to see some better pics and maybe get some specs from.


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## mike c (Apr 25, 2006)

Mike P. said:


> 2 times the amount of drivers would require a cabinet twice as big. Using the same tuning frequency, if you double the port area the port length remains the same.


double the port area and the same port length would change the port tuning. (make the tuning higher than 25hz [default pb12+2 tuning])


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## Mike P. (Apr 6, 2007)

mike c said:


> double the port area and the same port length would change the port tuning. (make the tuning higher than 25hz [default pb12+2 tuning])


A PB12+2 has 2 woofers and 3 ports. He has 4 of these drivers and wants to build a single box. To use all 4 drivers he would double the volume of the a pb12+2 and double the amount of port surface area(to prevent chuffing). The port length would remain the same to have the same tuning frequency of the PB12+2.

Example:
5 cubic feet tuned to 25 hz requires 3-four inch ports to be 29.5 inches long.
10 cubic feet tuned to 25 hz requires 6-four inch ports to be 29.5 inches long. Double the volume, double the port area, port length remains the same.


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## mike c (Apr 25, 2006)

right. for some reason I was under the impression, more port area needs more port length.

perhaps I was thinking a bigger port will require a longer port? e.g. two 4"ers converted into one 6"er


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## SteveCallas (Apr 29, 2006)

Does the Plus/2 use an isobaric driver configuration or am I thinking of the Plus/4? That would play a big role if you are looking to simply double the volume for twice as many drivers.


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## atledreier (Mar 2, 2007)

+/2 is not isobarik.


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## Ilkka (Jun 8, 2006)

SteveCallas said:


> Does the Plus/2 use an isobaric driver configuration or am I thinking of the Plus/4? That would play a big role if you are looking to simply double the volume for twice as many drivers.


Neither of them uses an isobaric driver configuration. The Plus/2 is a basic dual driver push-push design, and the Plus/4 is (or actually was) a quad driver push-pull design.


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## Guest (Feb 21, 2008)

thanks for the input. i have been doing some research online and have been finding out some good info. it appears the b4+ isnt twice the size of the pb12+2..infact its actually pretty close in size suprisingly. Size: 26" H x 32" W x 25" D are the deminsons. i found some good pics online of the arrangement of subs as well. http://www.hometheaterhifi.com/volume_10_3/svs-b4-subwoofer-9-2003.html
if you scroll down it looks like they are in a push pull arangement and that small cavity that houses the two subs in the middle of the cabinet seems only large enough for 2 subs to fit in to. the top and side distance look to be 12x12 and then just enough space for the two magnets not to touch that are back to back of each other. this still leaves me wondering about the inside arrangement. i assume other than lots of bracing everything is simply open and the port lengths for all 4 of the 4" ports are the same length. thanks for all the input guys


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## simon10 (Feb 19, 2007)

Ok been ages since I've been here totally forgot about this site. Well I'm back and have a question. I curently own the SVS B12-Plus/4 formally known as the B4+ and I'm upgrading my Quest QA-3000A (old model) amp to a Behringer EP2500 Europower Amplifier. The reason for the change is I'm getting clipping lights on the Quest (not running sub hot measured approx 70db on SPL meter Radio Shack analogue) while watching Ironman and Incredible Hulk both on Blu-Ray and I have contacted SVS and gave them the amp model with links to it's power specs and they said that it's not suited to power the B4+ as it's minium output in bridge mode is 8ohms. Now the drivers in the sub are 4ohms so will the EP2500 be a good match? Going by it's specs it should be able to give me the power I need. What are peoples thoughts? Thanks in advance:clap:

Sorry for going slightly off topic


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