# Subwoofer crawl positions - advice requested



## Spazdoc (Jan 14, 2015)

So I intended to put my subwoofer in MLP today and move the mic, but it actually was easy enough to move the 100 lb HSU sub after my tailbone healed. I have 6 main positions around the front stage, since I do not want to sacrifice rear space with a primary sub (it is a kids play and yoga area). Let me know if there is anything I need to change with my graphs, as I think that I followed the sticky notes.

Layout of my home theater:








Position A at Right front








Between A and B at Right front








Position B at Right front








Position C at Left front








Between C and D at Left front








Position D at Left front








Position E Left of Center








Position F Right of Center (Sub Volume know turned up by 10% by mistake)








So, some issues I ran into:
- Both Left and Right of center are right in front of a projector screen and had some recurrent dips, even after correcting subwoofer level (concrete floor is not completely level). I have no idea what this was, but I could hear some type of 'resonance' during the measurements
- While moving the sub to Right Center, the volume turned up by 10% (9 o'clock to 10 o'clock) and not recognized until after moving the sub.

Questions:
1. Am I correct in assuming that my best sub positions for MLP is Between C-D (left front), followed by between A-B?
2. My original listening position position is A. In theory, would bass traps be able to remove some of the peak at 40 Hz?
3. Are my curves from A-B and C-D good, or would bass traps help with the sound? Do I need to run a waterfall to determine need for bass traps?

Any advice is greatly appreciated.


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## AudiocRaver (Jun 6, 2012)

Thank you for being brave and moving your sub around. There are many adherents to the "sub crawl," but I have a hard time believing it can provide other than the most gross, general results. Our ears are just not that good at those frequencies. I'll bet you would have eliminated the F position using the sub crawl and nothing more.



Spazdoc said:


> Questions:
> 1. Am I correct in assuming that my best sub positions for MLP is Between C-D (left front), followed by between A-B?


Yes, those look like the best alternatives to me.



> 2. My original listening position position is A. In theory, would bass traps be able to remove some of the peak at 40 Hz?


Maybe.



> 3. Are my curves from A-B and C-D good, or would bass traps help with the sound? Do I need to run a waterfall to determine need for bass traps?
> 
> Any advice is greatly appreciated.


Again, maybe on the bass traps. A little EQ might do it, too. Yes the waterfall would help. The 40 Hz and 20 Hz peaks correspond to the 14 ft width of the room (wavelength and 1/2 wavelength of 40 Hz and 20 Hz). It takes big traps to do much at those frequencies, though. the main thing they might accomplish is deaden the ringing the goes along with the resonance, then EQ could flatten the peak.


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## Talley (Dec 8, 2010)

what HSU sub? and your MLP is not really ideal being more centered in room.

Also... My uncle had a major resonance and peak spike at 63hz... he built a 14' long 12" diameter sonotube or somewhere along that size whatever it was was designed to resonate at that same 63hz and he filled the entire inside with with fiberglass and it only removed 5db from the peak. he also has a few helmholtz for some other frequencies but him being a subless 2 channel setup without EQ he has his room dialed in pretty good with acoustical treatments alone.

I was just sharing that it does indeed take alot of treatment to fix peaks like that. EQ helps alot but I was also told on this site you don't really want to do any boosting to prevent clipping.


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## Spazdoc (Jan 14, 2015)

AudiocRaver said:


> Again, maybe on the bass traps. A little EQ might do it, too. Yes the waterfall would help. The 40 Hz and 20 Hz peaks correspond to the 14 ft width of the room (wavelength and 1/2 wavelength of 40 Hz and 20 Hz). It takes big traps to do much at those frequencies, though. the main thing they might accomplish is deaden the ringing the goes along with the resonance, then EQ could flatten the peak.


Thanks for the advice. I suspect that the ringing or resonance at the higher frequency in the center of the room (E and F) could be interaction with the projector screen. I have to have the sub a few inches in front of the screen to allow clearance for the front row.

I will do a waterfall now that I know which position to concentrate on (between C and D). Second sub will likely go in between A and B.


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## Spazdoc (Jan 14, 2015)

Bmxer241 said:


> what HSU sub? and your MLP is not really ideal being more centered in room.
> 
> Also... My uncle had a major resonance and peak spike at 63hz... he built a 14' long 12" diameter sonotube or somewhere along that size whatever it was was designed to resonate at that same 63hz and he filled the entire inside with with fiberglass and it only removed 5db from the peak. he also has a few helmholtz for some other frequencies but him being a subless 2 channel setup without EQ he has his room dialed in pretty good with acoustical treatments alone.
> 
> I was just sharing that it does indeed take alot of treatment to fix peaks like that. EQ helps alot but I was also told on this site you don't really want to do any boosting to prevent clipping.


Thank you.

HSU VTF-15H, got it when it first came out. Now I am eyeing the VTF-15H MK2 (either add a MK2 to the current, or sell the current and buy 2 MK2).

I had a consult from GIK when my complaint was boomy bass (1 port open on the HSU, EQ1, Q control 0.6) and they recommended monster traps in front corners, and bass traps along rear wall. I suspect that the alcove with radiator is not helping and I am thinking of putting bass trap in there above the radiator.

I totallly agree with my MLP position being less than ideal. I usually sit in the love seat in the second row on a riser. I do not want to push the seating back further because we still use the rear space for working out and Yoga (kids, too). And I cannot push the seating forward because of the proximity of the front row to the screen. We are stuck with two rows because we have 3 kids. When we do drain tile, there is a consideration to dig out the basement in this area and we would close off the room. Larger screen, seats move back, etc.


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## Talley (Dec 8, 2010)

Gotcha, 

I have the MK2 and a room dimension similiar to yours and I'm pleased to see your response down to 15hz with a single.

How big does that opening in the rear go beyond the side wall? You said it's 128" wide the opening but the depth? 

For movies I find that exact same setting sound the best... about a .6 EQ1 and 1 port open. 

So your room is in the basement surrounded by concrete huh.


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## Wayne A. Pflughaupt (Apr 13, 2006)

I’m going to vote for the F position because it doesn’t have any nulls until up in the 70 Hz range, and those should be blown out once the main speakers are added. The peak north of 40 Hz would be easy to tame with a parametric EQ, along with some boost in the 30 Hz range.

That said, I notice you didn’t take any measurements at any of the front corners. That’s typically where you get the most “workable” response, meaning response with no nulls that can be equalized easily. Typically a corner with uninterrupted walls in both directions is best, so I’m going to hazard a guess that a measurement in the C corner would get you a better reading than any you’ve presented so far.

Regards,
Wayne


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## Spazdoc (Jan 14, 2015)

Wayne A. Pflughaupt said:


> I’m going to vote for the F position because it doesn’t have any nulls until up in the 70 Hz range, and those should be blown out once the main speakers are added. The peak north of 40 Hz would be easy to tame with a parametric EQ, along with some boost in the 30 Hz range.
> 
> That said, I notice you didn’t take any measurements at any of the front corners. That’s typically where you get the most “workable” response, meaning response with no nulls that can be equalized easily. Typically a corner with uninterrupted walls in both directions is best, so I’m going to hazard a guess that a measurement in the C corner would get you a better reading than any you’ve presented so far.
> 
> ...


Thanks for the input. I actually had a couple hours today and moved the sub around to a few positions and rechecked F. The odd thing with position F is that when I run a measurement, the volume seems to wax and wane regardless of where I am in the room. Almost like resonance.

Right Center (F) Waveform and Waterfall from today
















So regarding the corners, I am planning on putting triangular bass traps in the corners, and I think that the sides are 17 in, so that is why I started the sub at about 20 in from front wall. Just for completeness, I ran a waveform at the front right (Behind A, 10in from wall):








And also left front (behind C, 4 in from wall with different sub cable)








One of my main complaints was that I was having boomy bass, and so here are waterfalls of the two best positions as above:

Waveforms appears similar:








Waterfall between AB (40 in from right wall)








Waterfall between CD (20 in from left wall)








So ran the right sub waveform with Audyssey, and it almost looks like they raise the levels to negate the troughs, rather than lowering the peaks (which made me worry about using position F since Audyssey might increase the curve to match the peak, like with my baseline position:








So I ended up placing sub at position C-D (20 in from front wall) given the waveform and waterfall.


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## AudiocRaver (Jun 6, 2012)

Agree with your reasons and like the results.:T


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## Wayne A. Pflughaupt (Apr 13, 2006)

Something is badly out of whack with the AB and F waterfalls. Anytime you see no indication of signal decay, it means there’s a steady-state, continual noise source of some kind. Typically we see this in the 60Hz region as noise from air conditioning or refrigerator motors, but I’ve never seen anything broadband like yours. It’s as if the waterfall was generated with a pink noise signal rather than a sweep. Might want to try to get to the bottom of it, but I wouldn’t select a location based on those waterfalls.

Notice that your A and C graphs improved considerably when the sub was moved closer to the corner. Good chance they would improve more directly in the corner, or perhaps out a bit towards the TV screen. How big are the bass traps? Any chance they can simply sit on top of the sub?

Regards, 
Wayne


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## Spazdoc (Jan 14, 2015)

Wayne A. Pflughaupt said:


> Notice that your A and C graphs improved considerably when the sub was moved closer to the corner. Good chance they would improve more directly in the corner, or perhaps out a bit towards the TV screen. How big are the bass traps? Any chance they can simply sit on top of the sub?
> 
> Regards,
> Wayne


With my current wires, I can get the sub within 4 in of the front wall. I am picking up GIK bass traps, and they are 16.5" x 16.5" x 23.5", with a velvet curtain right in front of the bass trap. So stacking the bass trap on top of the sub is not an options.

I reran the weaveform with the sub in the front left position (Audyssey off) and also measured the baseline noise (blue) on the same graph to see if there is any realistic contribution. The only sources of noise were the Runco projector (noisy fans) and my laptop.










And here is the waterfall:










Is the persistent bass at 20 Hz something I need to deal with? I have tried different positions for the sub in the left front without appreciable difference. Right now I would like to deal with the persistent ringing in the 40s. Any advice?


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## JohnM (Apr 11, 2006)

There's nothing especially concerning in that plot really, might be nice to bring that decay at around 42 Hz down a little but even if you did nothing to it there shouldn't be much at all in the way of audible detriment.


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## Spazdoc (Jan 14, 2015)

So one thing that I did not think of - the seating riser was built by a general contractor and before I invested much thought into acoustic treatments. As a result, it is 10'x5', frame made of 2x6s, a 1 in thick top, and no filling. I am wondering if this is contributing to that ringing down low.

Lifting it to fill with R30 would be a bit of a task since it is wired, lighted, and carpeted.


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