# Single vs. Dual Rythmik Subs



## Snoop (Dec 29, 2011)

I have a 3,500 CF room (16x21x10+) with 6' & 2.5' openings to kitchen and 3' opening to dining room. For mostly music and some HT, I think I need one Rythmik F15HP (600W) or two F15's (370W) or two F-12's (370W). I prefer buying the F15HP but am concerned if I have nulls, I will then want to buy a second sub to remedy that problem. If I knew now I needed two subs, I would buy two F15's. I don't really want two F15HPs. Any ideas what the chances I will end up with null problems and wish I had bought an F15 so I could add another one? Aesthetically, I would prefer two F12's if the F15HP doesn't work well.


----------



## Dale Rasco (Apr 11, 2009)

With that large of a room and those type of openings I would say that there will most likely be some nulls. Is there any chance you could post a drawing of the layout with the seating, display, speaker placements, etc?


----------



## Jungle Jack (Jul 28, 2009)

Hello,
I agree with Dale. In the abstract, dual subwoofers is the way to go.
Cheers,
JJ


----------



## Snoop (Dec 29, 2011)

Dale, Here is a sketch of my room. Assuming one F15 or F15HP sub, Brian at Rythmik says "the advantage of option 1 is it is in the corner. The possible shortcoming of option 2 is the French doors may allow the energy to escape and be wasted." After his reply, I read on the forums where two subs can help reduce the possible nulls I may have with one sub in a fairly large room with several openings. Before I bug Brian again, thought I'd put it out here for comments. I know I won't get optimum sound at all listening positions because they are so varied. I just don't have an idea about how bad a null is and if I can live with it. 

I will run Audyssey in the middle of the room between the two chairs, 12 feet from the front speakers. I can move the chairs together at that position when my wife and I watch movies. But for sitting in the existing seats listening to CDs or watching music videos, just wondering how it will sound with one sub. If two subs, which of these placements are most likely the best?


----------



## Sonnie (Apr 11, 2006)

Keep in mind that you have several seating positions there. It may be that you are going to have peaks and nulls in one or more of those locations. Treating the room may be your only hope to cure it for all listeners, but that's always super difficult in living rooms where you just can't place bulky bass traps... not to mention it is difficult when you can. A second sub will likely help in leveling out the overall response, but you may have to do a LOT of moving it around in the various locations to see which is best.

Are you setup to measure frequency sweeps so that you can see your sub response?

We have Sierra-1's in our great room... excellent speakers. :T


----------



## lsiberian (Mar 24, 2009)

In my experience and from Dr. Floyd Toole's research symmetrical placement with mutiple subwoofers works best. Ideally mid-wall placement on opposing sides. That said I too am limited on where to stick a subwoofer. 

Trial different positions and see which ones you prefer. That really is the best way to determine optimal placement. I find corner loading my subs to be preferable.


----------



## Dale Rasco (Apr 11, 2009)

I would suggest that this option 1 might give you better extension than the one Brian at Rythmik suggested. I only suggest it because there is an opening by the original Option 1. I still think 2 subs is the way to go, but if you really want to try it with one, check out Option 1 below.


----------



## Snoop (Dec 29, 2011)

I am not yet set up to do frequency sweeps. I plan to buy an analog SPL meter. Do I need a test disk? Anything else? I've read very little about it. Am I looking for flat frequency response measured across various low frequencies?


----------



## Snoop (Dec 29, 2011)

Dale, Dave at Ascend recommended your setup also. I also thought the entryway next to the big sofa may be a problem since it is less than a foot in front of the sub and maybe two feet to the right of it. I will try those two options first and choose the better location unless one of the other three spots works better.


----------



## lsiberian (Mar 24, 2009)

Snoop said:


> Am I looking for flat frequency response measured across various low frequencies?


Yes, but you will want to take an average of the area. Why not load the subs in opposing corners? 
If you are going to that much trouble you might look at getting a minidsp for EQ.


----------



## gdstupak (Jul 13, 2010)

Multiple sub locations can overcome nulls created by a single sub, but multiple subs will probably have frequencies where the drivers are out of phase from each other, so those frequencies will be reduced or cancelled out. Simply using the phase adjustment on the subs usually will not correct this problem but just transfer the problem to other frequencies.
Corner placement usually boosts certain frequencies over others. I like a flat response so I've never liked corner placement in any of my setups.
I used to use 2 subs in different locations and had to spend hours adjusting them to get them to work together. Several months ago I switched to an infinite baffle type setup with 2 drivers in the same unit located near the center of my greatroom in the ceiling and couldn't be happier. Much easier and quicker setup to get a flat response and mostly equal coverage throughout my greatroom.
I highly recommend using some form of eq for the subs.

Do you know the sub crawl technique for finding the best sub location? I use a cd with test tones to listen for the best sound and also use a spl meter to determine the location with the flattest response.


----------

