Dual subs on mid walls (pic included)

post #1 of 9

7/14/12 at 4:38pm

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Dual subs on mid walls (pic included)

Wanted some opinions on this, I lost all the notes I had on this subject so need a bit of advice. I have my dual subs place one on the front wall at around 60% ( cant do 50% due to TV) and one at 50% on the rear wall. The bass sounds good but with sub being so large I am getting a reflections from my CC and RF so I want a dual sub side wall/midwall placement. In the pic below you will notice I can not place the sub at the 50% mark do to the stairs but can place it at the 60% mark where the computer desk used to be (Not there anymore). On the left wall I can place it anywhere.

I have been told to place one sub at the 25% mark and one at the 50% mark, do you guys agree with this? I was thinking of putting the subs either both at 55-60% directly across from eachother or I could put one sub at 50% and one at 60%.

My seating is at 40% and right behind the seats in the pic before the hard floor is the 50% mark. So if I do the 50%-60% placement both subs will be behind MLP.

I rather keep the subs out of the front soundstage if possible, but not if it is going to hurt bass. Room is fully treated with GIK acoustics tri-traps, 242 panels and 8" bass traps on the rear wall.

pic:

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post #2 of 9

7/15/12 at 1:41am

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Have put the 1st sub at about the 50% mark and the other st 60%....sounds pretty good but will have to hear more content....still up for suggestions. I am just wondering If a staggered set-up would yield better results by putting one sub at 25% on the right wall and one sub at 50-60% on the other.

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post #3 of 9

7/15/12 at 7:05am

craig john
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Hi Rob,

While it would certainly be nice if we could look at your pictures and easily determine the best placements for your subs, the fact of the matter is that no one can predict this with any degree of certainty. The key to optimizing multi-subwoofer systems is having the ability to measure the response, and using those measurements to guide placement and EQ, as well as timing optimization. Do you have any way to measure your response? Something that can measure in both the frequency and time domains is most beneficial, but short of that, basic frequency response measurements are a good place to start.

Having said that, there are a couple of models one can use to guide placement. The first is Welti/Toole's recommendation: http://www.harman.com/EN-US/OurCompany/Technologyleadership/Documents/White%20Papers/multsubs.pdf For dual subs, the most optimal placements were found to be midwall, front and rear, with opposite corners being nearly as good. However, the Welti simulations, measurements and guidelines are based on a rectangular, sealed room. If the room does not meet those requirements, the recommendations are less applicable.

There is also the philosophy of Earl Geddes, who recommends random placement of multiple subs around the room: http://mehlau.net/audio/multisub_geddes/ However, his guidelines are based on statistics, and may not be applicable to your particular room and placement options. Also, they require more than 2 subs, with one being an LF sub and the other 2 being "filler" subs. Also, Geddes eschews Bass Management, (all speakers run as "Large" or Full Range), and his technique virtually requires measurements for optimization and level setting, (the 2 "filler" subs are set at lower levels than the LF sub, and the levels are optimized by measuring the response and setting them to the lowest level that impacts the response.

I, myself, use a hybrid of Earl Gedde technique. I have placed my subs randomly around my room. However, I use 3 identical subs, I use gain-matching for setting the levels, and I use Bass Management for bass redirection to the subwoofers. I use XTZ Room Analyzer to measure and optimize my subs. http://www.acousticfrontiers.com/XTZ-Room-Analyzer-II-Pro.html I have posted my results here: http://www.avsforum.com/t/759877/seaton-sound-submersive1/4500#post_19446901

Bottom line, you can spend hours and hours moving your subs around your room. However, until you can measure and "see" your response, you are pretty much just guessing and hoping. And so is anyone else who makes recommendations of placements for your subs in your room.

One last thought... the listening position has as big an impact on what you hear as does the placement of the sub(s). From your pictures, it looks like your LIP may be very close to the middle of the room. The middle of the room is usually a broad null for bass. 1/3 or 2/3 of the long dimension would be much better than the middle. IOW, if your room is 24' long, placing your LP at 8' or 16' will be much better than 12'.

Good luck.

Craig

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post #4 of 9

7/15/12 at 9:58am

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Quote:

Originally Posted by craig john

Hi Rob,
While it would certainly be nice if we could look at your pictures and easily determine the best placements for your subs, the fact of the matter is that no one can predict this with any degree of certainty. The key to optimizing multi-subwoofer systems is having the ability to measure the response, and using those measurements to guide placement and EQ, as well as timing optimization. Do you have any way to measure your response? Something that can measure in both the frequency and time domains is most beneficial, but short of that, basic frequency response measurements are a good place to start.
Having said that, there are a couple of models one can use to guide placement. The first is Welti/Toole's recommendation: http://www.harman.com/EN-US/OurCompany/Technologyleadership/Documents/White%20Papers/multsubs.pdf For dual subs, the most optimal placements were found to be midwall, front and rear, with opposite corners being nearly as good. However, the Welti simulations, measurements and guidelines are based on a rectangular, sealed room. If the room does not meet those requirements, the recommendations are less applicable.
There is also the philosophy of Earl Geddes, who recommends random placement of multiple subs around the room: http://mehlau.net/audio/multisub_geddes/ However, his guidelines are based on statistics, and may not be applicable to your particular room and placement options. Also, they require more than 2 subs, with one being an LF sub and the other 2 being "filler" subs. Also, Geddes eschews Bass Management, (all speakers run as "Large" or Full Range), and his technique virtually requires measurements for optimization and level setting, (the 2 "filler" subs are set at lower levels than the LF sub, and the levels are optimized by measuring the response and setting them to the lowest level that impacts the response.
I, myself, use a hybrid of Earl Gedde technique. I have placed my subs randomly around my room. However, I use 3 identical subs, I use gain-matching for setting the levels, and I use Bass Management for bass redirection to the subwoofers. I use XTZ Room Analyzer to measure and optimize my subs. http://www.acousticfrontiers.com/XTZ-Room-Analyzer-II-Pro.html I have posted my results here: http://www.avsforum.com/t/759877/seaton-sound-submersive1/4500#post_19446901
Bottom line, you can spend hours and hours moving your subs around your room. However, until you can measure and "see" your response, you are pretty much just guessing and hoping. And so is anyone else who makes recommendations of placements for your subs in your room.
One last thought... the listening position has as big an impact on what you hear as does the placement of the sub(s). From your pictures, it looks like your LIP may be very close to the middle of the room. The middle of the room is usually a broad null for bass. 1/3 or 2/3 of the long dimension would be much better than the middle. IOW, if your room is 24' long, placing your LP at 8' or 16' will be much better than 12'.
Good luck.
Craig

That is TON of info! My room 27' X 25' so it is a bit square lol!! I am getting measurement equipment very soon! My seats are a around 38-40% mark...the 50% mark is behind the seats where the carpet meets the hard floor. I may move it foward a bit like you suggested!

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post #5 of 9

7/15/12 at 11:01am

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I will say h new placement set the subs st -9.5 and -9.0 Vs the other spit I had them set at -6.5 and -6.0 wich indicates th new placement has more head room correct? Neither spot as ever gave me a good sub distance both spots where under measured as less than 1ft. Since I have not ordered measuring equipment yet I will be doing some sub crawling lol!!

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post #6 of 9

7/23/12 at 12:47pm

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Used the placement below, got a slight Hum/reverb and moved subs out a bit and used different mic placement....sounds great but still can not get a accurate sub distance...I have tried everything, I use a boom mic with auralex foot-pads ECT and my sub distance is set at I.E 1ft or 2 ft when it its actually 9.7 ft LOL!! I have mult32 on my 4311Ci.I have O-audio plate amps on both subs, maybe it is a phase thing....I have them both setr to "0"