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Discussion Starter · #1 ·
Hey all,

I was playing around with REW to measure my sub performance in my finished basement. I'm running two old SVS CS 16-46 cylinders powered by a Samson S700 amp. I normally have them split with one up front and one to the side of the MLP. I"m pretty limited in positioning as this is a relatively open floor plan that serves as movie room, kids playroom/dumping ground, and exercise area. It's around 2500 - 3000 ft^3 in a loosely L shaped area.

overall bass response is decent and they dig really low but seems to sometimes be lacking that chest thump around 50hz but I get a lot of tactile feeling and room creaking at the low end. the results I got on REW seem to back this up where I get a pretty high rolloff from >40 hz. I tried moving to a single sub to confirm no strange cancellation and moving the two subs around to the few positions these behemoths can fit in my current layout but still seeing the dropoff. Checked several seating positions and they were all pretty similar response. In the green trace I did a close up measurment of one of the subs from around a foot away from the driver and didn't see this drop out, so I'm assuming this is a room mode interaction causing this.

Not sure if this is the best subforum for this but just looking to see if any suggestions on actions to help remediate this frequency mode response?

thanks in advance for any words of wisdom!
 

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Discussion Starter · #2 ·
looks like the key wasn't attached to the pic in my original post. the green trace is the close up mic response, while the others are a few trials of moving the sub behind the MLP by 5 ft, the original split front/back config and both subs up front flanking the mains L/R. These latter 3 all show the dropout to varying degrees.
 

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is that space opened up to other parts of the house?

Where is the listening location in that space? is it somewhat center of the room?
 

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What are phase and crossover settings? Not sure of the sampsons capabilities there. It's a pretty smooth drop, but those numbers are good to know.
 

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Discussion Starter · #6 ·
here is a pretty rough layout of the basement. the seating is at the top of the L and is adjacent to a partially enclosed stairwell going up to a door to the first floor. (it can get pretty "echoey" in the stairwell) the flooring of entire basement and stairwell is carpeted. the under the stairs area as well as all the mechanicals and some extra space is enclosed from rest of the room is a storage area. This ends at the 45 degree wall which has folding doors separating it from rest of the basement. Other than that it is all open to each other. the area where the "theater" is located is roughly 12 x 15 x 8 with a drop ceiling throughout the whole area.

For the question on the sampson amp it's a pretty basic model. There are just gain controls and no selectable phase or crossover functionality from what I see on the HW as well as in the user manual online. I have both subs currently fed from the single output of my Onkyo 609 into the sampson running in parallel mode where the single input is fed to both outputs. I normally have setup the audyssey as around a 60 hz crossover for the fronts and 80 for the rears and center. I tried just swapping the polarity on the sub closest to the MLP and leaving front sub as is to see if that would help with cancellations but got a pretty gnarly response that definitely sounded not very clean even using the basic swept tones so didn't go down that road much more than that.
 

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Discussion Starter · #7 ·
here is a hopefully clearer picture of what I was measuring:

green - close up measurement of the left sub (moved up from back) in the front stage positioning. both subs active but measured from 1 ft away from left sub (located just to left of LF speaker)

orange - front right sub was only one active measured from MLP

blue - both subs in front on outside of the L/R speakers, measured from MLP

pink - subs in locations in drawing one to front right and one to back right, measured from MLP. This is normal location i've been using

red - front sub in same location, moved back sub 5 ft back from the MLP, still against the wall, measured from MLP


I"ll try to get back down there soon and measure each sub individually but when measuring from the MLP (and other spots) looks to be a pretty consistent dropout from what I saw.
 

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Discussion Starter · #8 ·
was able to get back down and measure. attached are both subs together in same location as in the drawing with front right and rear back positions.

green - both together, MLP in center of couch facing TV

Red - front only sub, MLP in center of couch facing TV

Light Red - front only sub, measured about a foot away from the driver on the floor (down facing woofer)

Blue - rear only sub , MLP in center of couch facing TV

Light Blue - rear only sub, measured about a foot away from the driver on the floor (down facing woofer)
 

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