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Discussion Starter #1
I’ve always read posts referring to people’s subwoofers literally shaking the house, knocking pictures off the walls, etc. I wonder if it’s all hyperbole or whether there is some holy grail of subwoofers that can literally shake you to the core. I do have a mix of both Clark Synthesis Platinum and Buttkicker Advance transducers for each of my theater chairs but I really want more impact from my subs instead.

My theater room is roughly 1,700 square feet (about 16’ W x 12’ L x 8.5’ H). I have a Denon AVR-X4000 receiver with Audyssey XT32. I’ve checked everything with REW for optimum sub location and end up with a reasonably flat response with the PB-13 Ultra’s 16 Hz tuning out to 100 Hz with the dual subs positioned catty corner from each other. The waterfall looks pretty good considering my room is not acoustically treated. The room has one door and when closed the room is sealed.

I typically watch movies at -10 dB with the subs trimmed to run +10 to +12 dB “hot” (I start with a -12 dB trim from the Audyssey calibration so I’m still giving a clean signal to the subs even at +12 dB). I’ve got a calibrated Umik-1 and measured the peaks at 115 to 120 dB utilizing some of my usual demo material: Lord of the Rings (several of scenes from various movies), U-571, Black Hawk Down, etc. The dual subs seem to reach these high peaks effortlessly and they sound great. At these high sound levels, I can lightly feel the bass and simply hope for more of a visceral punch if that is at all possible.

What is the actual realistic expectation for these subs in a room of this size?
Can I run the subs even hotter?
Will a custom sub or something with a 15” or 18” driver give more thump while remaining as clean as the great sound from my PB13 Ultras?
Is something else going to be exorbitantly more expensive for almost imperceptible gains?
Other thoughts or suggestions?
 

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Not sure, I'm sure the more knowledgeable people can respond. I think you may need the subs very close to you to get that affect.

I can feel the punch with my single HSU really easy. and not even that loud.
 

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Having subs at opposite corners may not be the best placement particularly if your seating is near the center of them.
Have you tried moving them or at least one to along a side wall?
 

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Discussion Starter #4
I do sit in the center of the room against the back wall of the theater with one sub to my right in the rear corner and the other sub in the left front corner. I tried the 9 possible combinations of sub locations my room would allow but other placements, including one in the middle of a side wall, resulted in large nulls at various frequencies that I wouldn't be able to correct in any way.
 

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With two subs it would be very unlikely that you would have a null if you have the phase set correctly. Something is not right here. I'm going to assume that you are running Audyessey correctly with the mic on a tripod at ear level pointing up? Also how are you measuring different positions?

Also if your seating in against the rear wall that is not ideal, you should pull it forward at lest 3ft
 

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Discussion Starter #6
With two subs it would be very unlikely that you would have a null if you have the phase set correctly. Something is not right here. I'm going to assume that you are running Audyessey correctly with the mic on a tripod at ear level pointing up? Also how are you measuring different positions?

Also if your seating in against the rear wall that is not ideal, you should pull it forward at lest 3ft
I run the REW sweeps on a microphone stand with the UMIK-1 pointed straight up and using the 0 degree narrow band response calibration. For running Audyssey with the Denon, I use a carbon fiber camera tripod with the Denon microphone pointed straight up. I run the Audyssey calibration from all 8 positions that it allows. C, L & R seats at center of where ears would be, 1 foot in front of C, L & R seats and 2 final measurements near the center of the arm rests (the center seat main listening position).

In playing around with various sub configurations, I was able to manually correct some of the nulls with the phase knob on the subs. Once I found the best combined locations for the subs, I set the phase of both to zero to let Audyssey make phase corrections.

Unfortunately, my seats are about 6" from the rear wall. Given the configuration of the room, projection screen size, etc., there is no way I can move the seats any more forward than they already are.
 

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I would also say that subwoofer will provide some "rumble" mostly (I would say 60hz and lower maybe?) and the punch you feel is usually more related to 80~240hz region. So having good speaker and crossing them correctly will provide the punch.

You will mostly feel pressure and vibration from the subwoofer.

My brother in law has Samson 12" Dj speaker and even without a subwoofer you feel them hitting your chest better than my subwoofer and they are not playing much below 80hz for sure.
 

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Discussion Starter #8
Upon further reflection, is it possible that given the subs are too powerful for the room? Let’s say you took a room around twice the size at 3,400 square feet. A sub would now actually be working hard to achieve reference level in such a large space. The excursion for the sub might be 3” or more to reach reference. Now, take a smaller space like mine with two subs at +3 dB and corner loading +6 dB. The subs no longer have work so hard to reach reference perhaps moving the driver only an 1” to reach reference volumes. I would think the excursion difference 3” vs. 1” would make a big difference in terms of pressurizing a room. If this theory is true, I’d probably have to push my subs to 120 dB or higher just to get this greater excursion. Make sense? Could it be that I’d be better running 1 sub as hard as that could be to imagine?
 

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What speakers do you have?
Are they all set to small?
Is your crossover set to 80Hz or higher?
Do you have dynamic EQ and or dynamic volume turned on?

Do you have the movie 'Finding Nemo'? If yes go to the scene where the girl taps on the aquarium in the dentist office....my single Outlaw LFM1+ produces waves of palatable bass in this scene .... It is set 3dB hot, exposed to ~12k^ft in my open floor plan house.
One of your subs will destroy mine....two should be making your ears pop.
 

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Do you have a background in car audio? Maybe your expectations are tempered as such. With the posted graph,and db numbers you mentioned, I'd expect a great tactile response in the LP. Also, 12" dj speakers that don't go much below 80hz would go straight into the garbage. Kick drums and bass guitar have the most punch in the 35-55hz range. Many car subs are tuned around 30hz. That's so you can feel them.
 

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The three reasons I can think of off the top of my head are: 1) user expectations. People go to a nightclub where the fr is very uneven and want to replicate that punch in a balanced ht environment, which is very unlikely. 2) "punch" is normally higher up the bass spectrum than a lot of people think. As Steeve-o mentioned, it is typically above 60 hz. Depending on the size of the main speakers and their dynamic ability, it may be beneficial to raise the crossover point from the mains to the sub and/or run eq (not Audyssey but a PEQ that is user definable) to bump the 60- ~200 hz range. 3) Flooring material. People who have a raised floor for their home theater will get more tactile response than people with a concrete slab as concrete isn't going to transmit energy (pretty much as all) which leaves the air pressure. Some people get around this by placing their seats on a raised platform.
 

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Upon further reflection, is it possible that given the subs are too powerful for the room?
No, that's definitely not it. Those subs in that room should be pulverizing your kidneys, and doing so with ease. You're cranking them up and still not getting the results you desire, so they certainly aren't too powerful.


3) Flooring material. People who have a raised floor for their home theater will get more tactile response than people with a concrete slab as concrete isn't going to transmit energy (pretty much as all) which leaves the air pressure. Some people get around this by placing their seats on a raised platform.
+1

A concrete floor will suck the life out of your subs - from a tactile sensation standpoint anyway - but the 'punch' you refer to is generally in the 40Hz-60Hz range, so from that respect you should be more than fine.

I'm at a loss because it sounds like you've done quite a bit of work to rectify the situation. Have you spoken with SVS yet? Perhaps they can shed some light on the situation.
 

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I have one sub and I get the slam/punch most of the time in a 5300 cf room with in ceiling speakers. I know you should definitely be able to achieve that with dual PB13's especially with the size of your room and having better mains than mine. Since you have done everything possible to determine why you are not getting that response I would call SVS like theJMan suggested.
 

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I say if you already messed with the phase switch and it still not what you are expecting, then pull out one of the subs and switch the positive & negative wires on it and try again.
I read in the past some owners had this same problem from SvS on an older hot water heater sub of theirs.
 

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Just a long shot but when you took that REW measurement you had the mic in the listening position?
I have one PB13u in a 4000cuft space with cement floors and it sounds amazing
 

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I find it impossible to believe that two PB13 Ultras in a 1700cuft room can only be "lightly" felt. Could you provide a little more detail regarding the type of slam you are looking for? You mentioned some movie scenes - what specific elements from those scenes are lacking the punch you seek?

I used one of these for a while in a two-story living room that opens up into other living spaces on two sides and it just seemed to have an endless amount of power. I simply can't imagine two of these in a <2000cuft room at -10db running 12db hot.
 

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Exactly. At 12db in that space I would think he could experience pressure similar to diving! JK
I asked about car audio expectations because if you're used to that kind of hit, and looking for that in your HT, it's gonna be hard. It seems like he's taken a lot of steps the right way. I'd call SVS too. Fwiw, I'm also on concrete. 2 of my subs are "water heaters" and not including the foyer and hallway, I'm just under 7000cuft. My kids say to each other often. Did you feel that? (I laugh inside). I need more sub to properly pressurize but they are tactile.
Btw...if the water is hot, why does it need a heater....
 

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I had a similar problem. First make sure the LFE is set to 120hz on your AVR.

I found that I got much more mid bass from it when the room wasn't absorbing the frequencies. Could try the new isolation feet SVS has or an auralex. Also retest at 20hz tune or in sealed mode seems to have the more mid bass tactile impact.

Most importantly, even though I had a flat frequency response when doing bass management on the AVR with XT32 on the full frequency sweeps. I found it was best to actually engage the crossover on the PB13, with it turned all the way up to 120hz, since it has a lot high frequency bleed from the TC driver when it was turned off at high listening levels. It seemed to help the quality tremendously since audyssey was most likely applying more corrections than necessary, causing phase correction issues as well with the other speakers on your remaining channels.

You can see it if you have this issue if you just disable all the EQ's on the AVR and sub, run a quick REW pass sweep from 20hz to 5K with ONLY the subs engaged and no other channels. If you see a lot of energy above 120hz turn on low pass crossover on the Sub and run again. I found it made a big difference in my setup. I have a BASH so maybe it is just related to that amp. Obviously if find this change necessary, then you should re-run xt32 again.
 
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