# Why no “slam” from my dual PB13 Ultras?



## zorax2 (Apr 7, 2014)

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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## Talley (Dec 8, 2010)

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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## tonyvdb (Sep 5, 2007)

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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## zorax2 (Apr 7, 2014)

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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## tonyvdb (Sep 5, 2007)

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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## zorax2 (Apr 7, 2014)

tonyvdb said:


> 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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## Steeve-O (Dec 3, 2010)

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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## zorax2 (Apr 7, 2014)

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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## chashint (Jan 12, 2011)

To test your theory turn off one of your subs.


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## chashint (Jan 12, 2011)

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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## willis7469 (Jan 31, 2014)

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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## snowmanick (Oct 16, 2007)

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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## theJman (Mar 3, 2012)

zorax2 said:


> 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.




snowmanick said:


> 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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## asere (Dec 7, 2011)

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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## Picture_Shooter (Dec 23, 2007)

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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## tonyvdb (Sep 5, 2007)

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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## Peter Loeser (Aug 11, 2012)

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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## willis7469 (Jan 31, 2014)

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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## Peter Loeser (Aug 11, 2012)

willis7469 said:


> Btw...if the water is hot, why does it need a heater....


I ask this question all the time!


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## eyecatcher127 (May 9, 2006)

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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## willis7469 (Jan 31, 2014)

Peter Loeser said:


> I ask this question all the time!


 lol. I can't help it!


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## zorax2 (Apr 7, 2014)

Thank you all so much for your continuing suggestions. I've run everything again along with doing the sub "crawl" and I'll post step by step what I did. The end result was lousy but I'll explain and hope for help at the end of this reply.


To correct my earlier post my room is approximately 1,722 cubic feet and approximately 198 square feet.

On to the subs:

I made all measurements at 85 dB based on my UMIK-1, using ASIO drivers for HDMI and using the SPL meter within REW5. My sub mode is set to LFE not LFE + Mains. LFC is off. LPF for LFE is at 120 Hz. My Left and Right mains are toed in and 10' from my MLP. My center is 8.6' from MLP.

I did the full Audyssey calibration for the MLP only. For the subwoofer level matching, I adjusted the gain on each sub to show 75 dB on the setup screen. This resulted in sub 1 (front left) trim of -9 dB and sub 2 (right rear) of -9.5 dB. The strangest thing out of the completed calibration that I noticed was that my Kef 203 mains crossover was set to 150 Hz while my smaller Kef 202c and Kef 201s were set to a crossover of 40 dB. I turned Audyssey to on and turned off the Dynamic EQ and Dynamic Volume features. To measure the Left Main + Sub and Right Main + Sub using ASIO, I select Output 1 for left (#2 for right) and Output 4 subwoofer for the timing reference output within REW. 


Scale on all graphs are 45 dB to 105 dB vertically and from 15 Hz to 200 Hz horizontally.

These are my dual PB-13 Ultras combined with my front left main speaker:









This is the waterfall (300 ms window) of the dual PB13 Ultras and the Left Front Main - very good from a flatness standpoint to about 120 Hz.









I'm really thrown off by the waterfall as it is substantially different than what I had previously. I used the default settings with 350 ms and kept the volume at 85 dB. Perhaps the change from 75 dB to 85 dB may have impacted this.


Here's a link to the full REW measurements:
 REW Measurements

*Time to listen and evaluate*
I put in U-571 as the depth charges are one of my favorite scenes for good bass. I set the volume to -10 dB and left the subs alone at their Audyssey defined trims of -9.0 and -9.5 dB. It was like there were no subwoofers at all. I then changed the subwoofer trims on both to 0 dB. While there was some perceptible bass - it was minimal and I know have had much, much better before where the room felt reasonably pressurized. I held my old school Radio Shack meter in hand and it was registering uncalibrated peaks of roughly 105 dB at the time. How can it possibly be that I have this sound level with what in this instance was now very little heard bass and virtually no room pressurization.


Something is seriously wrong and I just don't know what it is. While the waterfall now appears bloated, there still should be a feeling of some deep base in the room. In moving around in the room, I couldn't find a single good listening spot.


* There is a silver lining* - I ran a log sweep using the tone generator from 10 Hz to 100 Hz with a 20 second duration at 115 dB. Wow - there was some serious excursion at 10 dB. I really felt and heard the bass from 25 to 40 Hz and from 60 to 80 Hz. This leads me to believe the subs are working great and there is some other weird thing going on. Hopefully I can figure it out with your help.

Thank you for your continued help in resolving this problem!


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## fschris (Oct 31, 2009)

i suggest i spend some of your money ....  go to http://www.foambymail.com/bass-and-broadband-absorbers.html

and buy some of the corner bass traps and also by some 12x12 3" wedge foam.

get enough to get some good coverage on your back wall and maybe some on the sides. I spent about 200 bucks and got a large amount of product. i think these are some of the best prices as well. unless someone else chimes in. 

this is the probaby the cheapest option vs buy those expensive pre made bass traps etc... i bet this will help you out.

i know you moved your subs around etc...

I would take your couch out of the room and put the sub in its place and then also move around the room. start with one sub etc... ( also what kind of couch do you have?)

and buy the corner bass traps :yes:


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## willis7469 (Jan 31, 2014)

Zorax2, this is quite interesting. Where are you in the state? (Generally north or south etc) Promise I won't stalk you lol! Just wondering if you're by me, or someone I know. A visit perhaps.


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

I can’t tell if you have your graph scaled right (45-105 dB vertical) because the font is too tiny to read, and I have a 26” monitor. There’s a setting in REW that can fix that.




zorax2 said:


> 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.


 I only scanned the thread and maybe this was addressed, but IMO the problem is that your sub response is too flat. You could probably benefit from a house curve shelved at something like 25-30 Hz. Read all about it in the article you can find linked in my signature.

Regards, 
Wayne


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## zorax2 (Apr 7, 2014)

Wayne A. Pflughaupt said:


> I can’t tell if you have your graph scaled right (45-105 dB vertical) because the font is too tiny to read, and I have a 26” monitor. There’s a setting in REW that can fix that.


When I click the capture button, there is an option to set the image width to the default of 2274. I set the images up according to the "sticky" using an 800 pixel width.

What is the best way to post them with higher resolution? I couldn't find any other way to make an adjustment.


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## Axiomite (Dec 18, 2013)

Room treatment will help a tremendous amount. From my personal recent experience with corner bass traps specifically, it almost sounded as if I had different/additional speakers in my room after installing them. I also had a nagging sense of insufficient bass from my two subs and that changed a bit after some sound treatment.


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## Serenity Now (Mar 28, 2014)

2 PB13s and no slam? In that sized room?! Bonkers.

You are in a crazy null for sure. Move your listening position. Put both subs on the front wall and have them fire into the room. This creates a strong pressure wave that is responsible for tactile effect. Then try 0.2, 0.32, 0.45, 0.55, 0.68, 0.8 times the length of the room and sit there.

My 2 Baby SB 2000s would open the 36" x 80" furnace doors held in place by magnetic catches.... No joke. The small shelf resting LCD TV in the bedroom 2 floors up would visibly move during pacific rim. You should be getting nosebleeds if you want them. :R


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

zorax2 said:


> Wayne A. Pflughaupt said:
> 
> 
> > I can’t tell if you have your graph scaled right (45-105 dB vertical) because the font is too tiny to read, and I have a 26” monitor. There’s a setting in REW that can fix that.
> ...


The graph resolution is fine. I’m at work and don’t have access to REW, but I’m pretty sure that the font size for the graph indications can be changed in the Preferences window. There’s a tab, maybe the last one to the right, where you change the colors of the response traces and other things like that. It should be in there.

Regards,
Wayne


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## zorax2 (Apr 7, 2014)

Well, I had a chance to do more testing today. I really wanted to isolate what was going on so I grabbed my old Pioneer VSX-49TXi receiver and DV-47Ai DVD player (very nice equipment at the time but old school with no HDMI). I ran the Pioneer MCACC (old style equivalent to Audyssey) without touching the gains on the subs as they were level matched earlier via Audyssey at 75 dB. The result after MCACC was a sub trim of -1.

For comparison purposes, I used the DVD U-571 "Depth Charge" scene using DTS Surround and put on my hearing protection headset figuring this might take a while. My method was to use the DV-47Ai DVD player with both to eliminate any possibility that my regular Blu-Ray player had some sort of audio quirk going on that I didn't know about. The Pioneer has two sub out connectors so no Y connector was needed.

For the Pioneer, I played the scene at -10 dB from reference. The bass was what I was expecting at that volume level. The volume was registering around 102 dB for much of the bass scenes with some peaks around 110 dB via my calibrated UMIC-1 while running the Real Time Analyzer on REW. Finally, I could actually feel the bass with my clothes seeming to tingle, my chair was vibrating and just a nice feel to it. I was very happy with how things sounded and felt and believe that I'd have no trouble pushing things much further if desired.

I then hooked up the Pioneer DVD player to my Denon AVR-X4000 using component and optical inputs. I configured the Denon for standard DTS Surround and left on Audyssey but turned of the Dynamic EQ and Dynamic Volume. I left my previous settings for Audyssey alone with my sub trims at -9 dB for both subs, my main speakers crossovered at 120 Hz, distances the same, etc. As far as I could possibly tell from going through every on screen menu, there were no special features turned on.

I started my test with the Denon at the same -10 dB reference level and the scene appeared to be playing about 5 dB quitter in general with little to no bass effect. I then increased the master volume to -5 dB. This resulted in nearly the same volume levels of 102 dB but peaking at only 106 dB by comparision and still felt really lacking in bass. Given things still didn't seem right, I decided to try to get to the same "feel" (I wasn't paying attention to sound quality as I had been keeping on my hearing protection). To get the same effect, I left the master volume at -5 dB and took the sub trims from -9 dB to +5 dB - a net change on the sub trims of +14 dB!!! Finally, the subs were running from 102 dB with peaks around 112 dB. I could absolutely feel the bass in my chest and pant legs and even noticed the pages of my notebook blowing around. I finally achieved where I think things should have been on the Denon right from the start.

Clearly, this isn't a sub issue at this point that I can tell based on A/B comparisons. I'm going to do a factory reset on the Denon and do some more testing to make sure there is nothing I missed. I'll post back later with the results.


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## zorax2 (Apr 7, 2014)

I received an email from Ed at SVS recommending one other test which I just ran. Ed said "Running the subs 12 dB hot should not be required to obtain the desired amount of slam/impact/pressure, and suggests the two subs may be opposite polarity. With the phase set to 0 on both subs, place the two subs side-by-side, individually level match each sub to 75 dB playing the AVR sub rumble tone with the UMIC placed on the ground 1 meter from the center of both subs, and then turn-on both subs with the rumble tone playing. The combined SPL should increase to 81 dB. If the combined SPL drops dramatically, the subs are opposite polarity."

I followed Ed's instructions and when both subs were turned on side-by-side, they reached 78 dB (+3 dB) rather than the expected gain of +6 dB to 81 dB. I changed the phase on one of the subs from 0 degrees to 90 on each of the subs which dropped the output to just 72.5 dB combined. I'll check back with Ed on Monday unless someone suggests something else based on Ed's suggestion.

I performed the full factory reset on the Denon and the results were essentially the same after calibration the MLP only. It took a master volume level of -5 dB and the subs trimmed from -9 dB to +5 dB to get the hoped for results.


I'm not sure where to go from here . . .


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## sub_crazy (Nov 17, 2007)

Turn off Audyssey when doing this test, audyssey SubEQ adjust the phase of both subs separately so you want to remove that from the equation to adjust the phase when running them side by side.


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## sub_crazy (Nov 17, 2007)

zorax2 said:


> I followed Ed's instructions and when both subs were turned on side-by-side, they reached 78 dB (+3 dB) rather than the expected gain of +6 dB to 81 dB. *I changed the phase on one of the subs from 0 degrees to 90 on each of the subs which dropped the output to just 72.5 dB combined*.


Did you change the polarity on one sub or both? In the paragraph I made bold you say one of the subs but then later you each of the subs. 

You should only be doing 1 sub and both subs need to be facing the same direction. Try 90 and 180 degrees phase only only 1 sub.


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## zorax2 (Apr 7, 2014)

sub_crazy said:


> Did you change the polarity on one sub or both? In the paragraph I made bold you say one of the subs but then later you each of the subs.
> 
> You should only be doing 1 sub and both subs need to be facing the same direction. Try 90 and 180 degrees phase only only 1 sub.


Oops - I had a typo. I did place both subs side-by-side in 1 direction. I then brought each to 75 dB one at a time (the other sub turned off each time). Finally, I turned them on together with the phase set to 0 on both when it registered 78 dB. I then changed the phase on 1 of the subs which resulted in the change.

I'll have to redo this test anyway as I can't remember if Audyssey was turned on which could have invalidated my test if Audyssey adjusts for polarity and/or phase.


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## zorax2 (Apr 7, 2014)

I brought home a Denon AVR-X4100W (the update to my AVR-X4000) to demo. Both the new Denon X4100W and my old Pioneer 49TXi play all of the same deep bass scenes at 5 - 7 dB higher on the subwoofer channel at the same master volume setting. I'm going to chalk this one up to problems with my AVR's subwoofer outputs and send it in for warranty service. The dual PB13 Ultras now rock my theater room when driven to 105 dB to 118 dB (I didn't try for more). Thank you all for your help and insight!


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## theJman (Mar 3, 2012)

zorax2 said:


> The dual PB13 Ultras now rock my theater room


That sounds more like it. You must have been :wits-end: for a while there. Glad it all worked out.


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## sub_crazy (Nov 17, 2007)

Huh, it was the Denon in the library with the candlestick 

Glad it worked out for you and your once again a true basshead!

Long Live the BASS!!!!!!!!!!!!!!!!!!!


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## Axiomite (Dec 18, 2013)

This makes me wonder if my X4000 isn't utilizing my two PSA subs fully. One of the selling points for the X4000at the time was the dual sub equalization software combined with XT32.


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## jreb14 (Feb 18, 2015)

I tried dual subs once with a Yamaha 477 and thought the same thing ended up taking one of the subs out of the scenario. I had no bass with both subs. I did get good bass if y plugged off one the sub leads. both leads worked just not both at same time. I ended up selling that receiver.


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