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  #1  
Old June 27th, 2014, 9:46 PM
Outlaw1070 Outlaw1070 is offline
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Moving to the basement, Advise for 2 sub locations

I have (2) subs:
VTF-3 MK3 Sub
VTF-3 MK4 Sub
I'm moving to my basement with my home theater and would like some recommended locations for both of my subs. I will be using a Denon AVR-X4000 with Audyssey MultEQ XT32 and Sub-EQ HT. I also have a Omnimic V2 and REW. So basically just looking for your thoughts on locations for good smooth balanced bass. I can put the subs anyplace. The finished room is about 1200 sq. ft. but I'm only interested in good sound from the four theater seats. I hope these two subs are enough to pressurize this room. In my drawing you can see the seating (4) seats and 135" screen about 18' forward. I'm thinking one in the right front corner next to the screen and one behind the seats next to the wall. I'm just starting to build this room in my unfinished basement so I have many options to change things right now. It will have 8' suspended acoustic ceiling, walls are drywall and floor is carpet. What do you think?
Thanks
__________________
Regards,
Tom
-------------------------
Denon AVR-X4000
Audyssey Multeq xt32 with Sub EQ HT
miniDSP Balanced 2x4
VTF-3 MK3 Sub
VTF-3 MK4 Sub
MBM-12
Sony VPL-HW40ES projector
Carada BW 134" Criterion Screen
OPPO BDP-103 Blu-Ray
Darblet DVP 5000
Buttkicker system
AH! Njoe Tjoeb 4000 Redbook CD
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  #2  
Old June 30th, 2014, 10:40 PM
SME SME is offline
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I have a few comments.

Are you willing to devote some time with the mic and REW to get the best results? If so, I can give you some guidance. To start with, I would measure the response of a single sub at each listening location when placed in each candidate location. Ideally, I would measure from 10-20000 Hz with bass management enabled and a high crossover (250 Hz?). REW cannot measure absolute time with the Omnimic, so the high frequency measurement gives you an acoustic marker to time align the signals with.

Your seats are fairly close to one of the center-lines of the room. Can you move your seats forward a bit? For the same reason, placing a sub right behind the listening area may not be for the best. I would lean toward placing both subs as in or close to the front right corner and bringing the seats forward as much as other considerations allow.
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Old July 1st, 2014, 3:11 AM
Outlaw1070 Outlaw1070 is offline
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Quote:
Originally Posted by SME View Post
I have a few comments.

Are you willing to devote some time with the mic and REW to get the best results? If so, I can give you some guidance. To start with, I would measure the response of a single sub at each listening location when placed in each candidate location. Ideally, I would measure from 10-20000 Hz with bass management enabled and a high crossover (250 Hz?). REW cannot measure absolute time with the Omnimic, so the high frequency measurement gives you an acoustic marker to time align the signals with.

Your seats are fairly close to one of the center-lines of the room. Can you move your seats forward a bit? For the same reason, placing a sub right behind the listening area may not be for the best. I would lean toward placing both subs as in or close to the front right corner and bringing the seats forward as much as other considerations allow.
Thanks for your comments and suggestions.
Yes, I will take your suggestion and measure the subs at each location and with the settings as you suggest.
Is the issue with REW and absolute time because of any USB mic or just an Omnimic?
I can move the seats forward a bit, but I would like to understand the center-line of the room situation? Is anywhere near the center-lines not recommended?
__________________
Regards,
Tom
-------------------------
Denon AVR-X4000
Audyssey Multeq xt32 with Sub EQ HT
miniDSP Balanced 2x4
VTF-3 MK3 Sub
VTF-3 MK4 Sub
MBM-12
Sony VPL-HW40ES projector
Carada BW 134" Criterion Screen
OPPO BDP-103 Blu-Ray
Darblet DVP 5000
Buttkicker system
AH! Njoe Tjoeb 4000 Redbook CD
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  #4  
Old July 1st, 2014, 7:50 PM
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JerryMeeker JerryMeeker is offline
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Here are the modes associated with your room dimensions:



If your seating is placed at the midpoint of the room length (37'), then you will be sitting in a null associated with 15Hz, meaning you won't hear this frequency. This is a pretty low frequency, so it may not make a difference. If you wan to avoid this null, move the seats several feet forward or backward.

You want to use sub placement to correct the other nulls you have in the room. You do this by placing a sub in the null so that it excites that frequency. So, you have a null at 30 Hz, so to correct that null, you would locate a sub at the 1/4 or 3/4 point along the side wall, i.e. 6.25 ft from the back wall or the front wall. For the room width, you have a null at 35 Hz, so try placing a sub at 1/4 of the room width (7.75 ft) away from the side wall, assuming your front screen allows for a sub placement along the front wall.

Once you have these two starting points, run a REW sweep measurement 15-300Hz with only the subs. look at the response curve, and try and see if there is a correlation between peaks and dips, and the room modes shown in the standing wave calculator above. If you have dips associated with one of the known modes, try moving a sub into the center of the dip and re-measure.

This is an iterative process that will involve a lot of moving of subs and re-measuring, but you will eventually find positions that achieve the best response. It may not be perfect, but what you are looking for is the best you can do before running Audyssey. Finally, run Audyssey and see if it provides even further improvement.

Once you think you are done, you should check bass resonance, which is done using the REW Waterfall. Good bass is not just a reasonably flat response curve, it is controlled resonance as well, which is accomplished by adding room treatments.

Good luck!

Here are a couple of links you may find useful:

http://www.avsforum.com/forum/91-aud...l#post22823228

http://www.avsforum.com/forum/15-gen...l#post23859810
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  #5  
Old July 2nd, 2014, 2:42 AM
Outlaw1070 Outlaw1070 is offline
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Location: Michigan
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Thank you very much Jerry. This is helping me to understand the basics and what I need to do. Much appreciated! I'm looking forward to experimenting and running the tests.
__________________
Regards,
Tom
-------------------------
Denon AVR-X4000
Audyssey Multeq xt32 with Sub EQ HT
miniDSP Balanced 2x4
VTF-3 MK3 Sub
VTF-3 MK4 Sub
MBM-12
Sony VPL-HW40ES projector
Carada BW 134" Criterion Screen
OPPO BDP-103 Blu-Ray
Darblet DVP 5000
Buttkicker system
AH! Njoe Tjoeb 4000 Redbook CD
Reply With Quote
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