# Subwoofer questions/PB-13 Ultra



## kjlewie (May 24, 2008)

Hello,

I'm a new member and I have some subwoofer questions that emerged as a result of discussions on a Home Audio speaker thread 

http://www.hometheatershack.com/for...2-inwall-onwall-inceiling-speaker-advice.html

As a preface, I don't know a great deal of technical stuff about bass, which I'm sure will be obvious with my questions. I posted this in the Subwoofer area as well due to the general nature of some of my questions.

1. What does it mean when a sub pressurizes a room :huh:?

2. Does a HT have to be enclosed to be pressurized or can it (in pratical terms) be accomplished with a HT area within a larger multipurpose room? My HT is a 12' x 18' area within a larger (~6500 cubic foot) basement with an open staircase to the first floor.

3. Currently, I'm planning to add two SVS PB-13 Ultras. Either to replace or combine with my Infinity CWS -10 (x2). Another poster mentioned that to achieve DD reference level bass in such an open space I would need multiple 18" subs :no:. What kind of bass can I expect in such an open space? During high bass segments of movies, will it concussive "hit in the chest" bass or something else?

I have more questions, but I wanted to start here and see where the discussion went. If there are threads already out there that answers these questions, please point them out and I will happily sit quietly and read without disturbing others :reading:.

Thanks for your thoughts.

kjl


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## drdoan (Aug 30, 2006)

*Re: Subwoofer questions*

Hi kjl. Here is my take on your questions:
1) pressurization = wife complaining it is too loud, you feel it in your chest and ear drums, and smile so your wife can't see you!
2) the larger and more open the room, the more bass you will need to pressurize it.
3) how much bass you will need is definitely related to both room size and openness. However, 2 Ultras are able to do quite a bit in that regard. I would call or email SVSound with the room size question as see what they say.

Have fun, and keep us posted! Dennis


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## tonyvdb (Sep 5, 2007)

I can assure you that even one PB13 Ultra will do what you ask in your room two is not a bad idea but even one would work. The PB13 Ultra has a far better response than most competition 18" subs as the box size and driver design play a huge part in how well they produce the lower frequencies. My room is 15' x 35' with an 8.5ft ceiling and I only have one PB13.
The so called pressurized room comments in my opinion is really not an issue more so simply placing the sub or subs in the right spot in the room will give you the best results. Very few people have perfect rooms and rather than worry about openings and fixing strange angles in the walls concentrate on finding a corner (usualy in the front of the room by your main speakers) to start with.

Have a look at this article here as I agree with most of what he says.


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## kjlewie (May 24, 2008)

Thanks for the article. Very interesting and different from most of what I've read. Do you have any pics to show your set up and room?

Thanks,

kjl


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## Alex at SVS (May 13, 2008)

There's a lot of guesswork in finding the right sub and positioning it properly. Even moving a sub 6 inches can cause or solve a hundred problems at once. In the article it says that corners excite all the room modes and is the worst location, which is very true in the theoretical sense. But in practical applications and measuring for a flat response with mic and proper software, the corner generally provides excellent placement for many rooms. It isn't the end all/be all location some believe it to be, but if you're not going to run tests and experiment with positioning it's generally a good spot.

To your questions...
1. Pressurize the room just means that bass can either escape the room through a large opening, or be reflected back by a wall. If it's reflected back in all parts of the room (i.e. enclosed room) then the bass sounds louder and especially so when the walls are close together. If there is a large opening to a big room then the bass can "escape". This is part of the reason subwoofer tests are always done outside as sounds can't bounce back off anything.

2. The room doesn't have to be enclosed at all. All it means is that since the bass isn't getting bounced back as often into the room as often you're going to need a more powerful sub. If your HT size room was completely enclosed you could get reference level (0dB) with a PC-Plus.

3. I think you'd need 2 Ultra subs for that level of bass in that large of a room. An Ultra in that room is enough for most people, but that's because very few people ever need to turn their systems up to reference volume. If you consider that a single PB13-Ultra is equal in SPL to a PB12-Plus/2 (dual 12" driver system when the Plus/2 is tuned to 20Hz) then I think you can appreciate this beast can overpower many subs even ones costing far more.


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## kjlewie (May 24, 2008)

Thanks for the thoughts and detailed responses. The information is very useful and educational. I now realize that it is very unlikely that I'd listen at DD reference level (0dB). Typically, we watch family movies at -45 to -40dB or so, maybe a little louder (-35) until my wife enthusiastically encourages me to turn it down :hissyfit:. I can't imagine going above -30dB. Sounds like one Ultra would be sufficient. Still, the headroom of two Ultras playing at our listening levels is very appealing :yes:.

Thanks again for the advice.

kjl


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## tonyvdb (Sep 5, 2007)

kjlewie said:


> Thanks for the article. Very interesting and different from most of what I've read. Do you have any pics to show your set up and room?
> 
> Thanks,
> 
> kjl


Yes I do, I haven't taken any pictures for some time so these are a bit dated and I have done more improvements to it. Have a look at this thread here and Here for my arrival of my new PB13 Ultra.


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## kjlewie (May 24, 2008)

Nice setup Tony:T. Nice build thread - thanks for the links. Your Ultra looks right at home. That really is a large room. What else have you done to the room since the pictures?

kjl


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## tonyvdb (Sep 5, 2007)

I cleaned up the spot around the projector and installed some more Quash (the black stuff on the ceiling) I painted the lower drywall on both sides of the room a reddish color and installed some different lighting.
My plans for the next month or so once I finish our kitchen tiles is to build a riser and have another row of seating.


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## weeZ (Sep 10, 2006)

kjl,

I have dual 13's and the sound is amazing! Have done comparisons between single versus double, single produce more peaks and valleys in the room response, duals give me a flatter response with no equalization needed. They are placed about 8.5ft from the nearest corner, and my room is huge. The duals easily pressurize the space and then some.

Tried stacked, but it produced a nasty null at 55Hz and was vetoed by my wife


They are kept end to end


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## kjlewie (May 24, 2008)

Keith,

Thanks for the response and pics. That looks like a huge room.

Are the Ultras sitting directly on the wood floor? Or, is there something between them and the floor?

Thanks for reading.

kjlewie


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## weeZ (Sep 10, 2006)

They sit directly on the floor(slab foundation) with the supplied rubber feet. Was worried they would vibrate/bounce like my previous down firing subs, with the front firing orientation they don't budge even under the most demanding scenes.


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