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Discussion Starter · #1 · (Edited)
I’ve got a relatively small 1,700 cubic foot (12’ x 16’ x 9’ H) home theater currently served by a pair of SVS PB-13U subs. They are well balanced in the room, have a relatively flat response at the MLP through 90 Hz and achieve peaks of around 116 dB on bass scenes in movies (I can’t push it any further). I’m typically running the mains and surrounds at -12dB with the subs set to run at +15 dB (3 dB hotter than reference for the sub).

I don’t think anyone could argue with the quality of sound from the PB-13Us, what I feel is a lack of impact of slam which might be related to needing more dB of headroom or greater displacement from the drivers. While I have rubber isolators between the concrete floor and my theater chairs and use tactile transducers, I want to “feel” the sub during action scenes in movies or feel the explosions in Battlefield 4 or Call of Duty. I only listen to music 5% of the time at most.

I considered a wide variety of subs but these are the only options that seemed to work for the physical space I have to put the subwoofers in and for the goal I want to accomplish.

SVS PB-13U – Have two, need one more – approximate used cost $3,600 total ($1,200 out of pocket)

Power Sounds Audio (PSA) S3600i – would need two new ones - $3,300 total (Sell 2 PB-13U for $2,400, $900 out of pocket.)

DIY Othorn – For amp, cabinet, speaker, labor – guess $3,000 total (Sell 2 PB-13U for $2,400, $600 out of pocket)

JTR Captivator S1 - Need two new ones - $4,000 total (Sell 2 PB-13Us for $2,400, $1,600 out of pocket)

The contenders:

Three SVS PB-13U
Will adding a 3rd PB-13U add enough dB and displacement for the “punch” I’m looking for? Theoretically, there should be a 6 dB gain but in practice I’m guessing 2 to 4 dB gain across most of the frequency range and there’s no way to know if I’ll get the gain I need between 60 to 80 Hz in particular. If you think I’m not gaining much punch, it’s not worth it to me to add another PB-13U to simply improve the in-room response.

Dual PSA S3600i
With duals, that 4 – 18” drivers – that’s a lot of displacement! Has a lot more power 60 Hz and higher. The only current review is at: http://hometheaterreview.com/power-sound-audio-s3600i-subwoofer-reviewed/ Everything specs out very nicely. Based on specs it would seem that this would be a great fit for me. I’d certainly prefer this to be made of Baltic Birch rather than MDF so that is a concern of mine. If I make changes down the road, I don’t think these will hold nearly the resale value that the SVS subs do. The other thing is that I wasn’t even aware of this company until recently though it seems they have a good following.

Single Othorn with 21” driver
A fire breathing beast! Obviously, the raw output of this thing is unbeatable. The JTR Orbit Shifter would be better for me, as I wouldn’t have to build it, but it doesn’t fit. What scares me is that I can only fit one of these Othorns in the room, and worse, there is only one spot that it can fit and there is no room for movement. I’m really concerned about potential localization of sound and the consistency of the frequency response across the listening area. As you might guess, my wife will hate the looks of this. I’m also a bit reluctant to tackle building this. Nevertheless, it would be a mistake to not at least consider this.

Dual JTR Captivator S1
Somehow I missed seeing that this sub would fit my space. Need to learn more to compare to the rest . . .

I really want to move the bar higher if I do make a change. A somewhat marginal change isn’t really worth it to me and I would in that case just stick with what I have until I have a larger home theater space to work with. What are your recommendations?
 

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Discussion Starter · #2 ·
Frequency and Waterfall from REW. Note dip from roughly 80 to 100 Hz
 

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What are your recommendations?
That you call SVS and see what they have to say. A single PB13U is more than enough in a room that size, but a pair should be able to beat you mercilessly. I'm wondering if perhaps you have a configuration issue. I honestly can't envision a scenario where those two subs wouldn't have tons of excess capacity, unless that 1700 ft^3 area is just a section of a much larger room.
 

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Discussion Starter · #4 ·
I talked with Ed last year and he thought it might be a polarity issue. "Running the subs 12 dB hot (I'm now at +15 dB) 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." Everything tested fine. I guess I'll go back and re-check this on more time.

I've checked bass management settings multiple times. As best as I can tell, the subs work perfectly fine given the frequency response and waterfall plus I don't think there's a chance they'd hit 116 dB if they weren't working right. When I run REW sine wave test tones, you can watch the drivers and they sure look like they're moving just fine. It's frustrating to me - I keep hearing my room should thrashed with a pair of those bad boys (it is a sealed room), yet the walls aren't shaking, my movie poster frames aren't moving, only light tactical feel during action scenes.
 

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Yeah, I'm with Jman on this one. I don't have any direct experience with SVS products, but I've come pretty close to doing structural damage with significantly lesser subs.

Just out of curiosity, with all the settings on each sub matched, do they actually move in the same direction when a signal is applied? Also, does the system sound significantly different with one sub turned OFF? If it does, the problem is one sub or the other. If it doesn't, the problem is either the signal or the room.

Noticed that you're using this as a video game setup... where are the subs in relation to the MLP and the main speakers? It may be that you're sitting in a null, and your neighbors are calling down curses on your future offspring... or that the subs and mains are stepping on each other and creating a phase issue that cancels out the punch you're craving.

Whatever the case, in a room that size with two of these monsters, you should already be dead.
 

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Are you on a slab? That would rob you in the way of requiring more output for a given tactile feel. Also, the PB13(s) are ported. In my experience, ported subs/speakers sound less tight than sealed versions. A ported model may still have good pitch-delineation and punch with the right program material, but I've experienced better punch in general using sealed models. That's in a smaller room than yours, though. Have you looked at smoothing your dip through the crossover region using phase adjustment on the subs?


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Discussion Starter · #7 ·
Yeah, I'm with Jman on this one. I don't have any direct experience with SVS products, but I've come pretty close to doing structural damage with significantly lesser subs.

Just out of curiosity, with all the settings on each sub matched, do they actually move in the same direction when a signal is applied? Also, does the system sound significantly different with one sub turned OFF? If it does, the problem is one sub or the other. If it doesn't, the problem is either the signal or the room.

Noticed that you're using this as a video game setup... where are the subs in relation to the MLP and the main speakers? It may be that you're sitting in a null, and your neighbors are calling down curses on your future offspring... or that the subs and mains are stepping on each other and creating a phase issue that cancels out the punch you're craving.

Whatever the case, in a room that size with two of these monsters, you should already be dead.
Settings on the sub are matched and I have checked phasing. A problem was discovered today that probably caused some of the problems I was having.

My son came home on the bus while I was testing my subs at 125+ dB - he says "Holy cow Dad - those are really loud outside! You're rocking it!" It sure brought a smile to my face as I knew I was definitely going in the right direction!

I almost fell off my chair laughing at your last statement. Hopefully, I'll get to the point where my subs can beat me into submission.
 

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Discussion Starter · #8 ·
Are you on a slab? That would rob you in the way of requiring more output for a given tactile feel. Also, the PB13(s) are ported. In my experience, ported subs/speakers sound less tight than sealed versions. A ported model may still have good pitch-delineation and punch with the right program material, but I've experienced better punch in general using sealed models. That's in a smaller room than yours, though. Have you looked at smoothing your dip through the crossover region using phase adjustment on the subs?
I'm using Buttkicker isolator feet (http://thebuttkicker.com/ri-4). They do an awesome job decoupling my theater seats from the concrete floor - they make it almost as good as the wood floor effect.

After experimenting, I was able to flatten the response more. The phase adjustment on the sub didn't seem to help anything in the long run. As I understand it, the Audyssey XT32 does phase management on its own as well.
 

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Discussion Starter · #9 ·
I broke out my UMIK-1 and REW again today for testing. Rather than turning off my 3 Buttkicker amps (for each person to separately control their seats via IR), I unplugged their power cords. In doing this, I accidentally found part of the problem with my bass response may have been in that the Buttkicker amps are after a “Y” that goes to one of the subs and then daisy chains between the Buttkicker amps – I think it was sucking up some of the LFE signal to the subs. I played some test movie material that had maxed out at 116.8 dB a couple days ago that now plays back at 127.5 dB. Huge difference!

So, at this point, I believe the PB-13Us are working as they should be and the question becomes whether that is good enough. I tested the subs in 3 tunes – Sealed, 15 Hz and 20 Hz. The sealed tuning yielded unbelievable extension down low and all three tunings were close in terms of the peak max dB from the movie material. All three tunings had a very nice flat frequency response between roughly 20 and 90 Hz with a 4 – 8 dB drop to 100 Hz. For whatever reason, the sealed tuning did not seem to have has much tactile feedback for me. The 15 Hz tuning is the one I’ll use at it provides good extension down low and seems to have as much tactile feedback as the 20 Hz tuning.

I attached a diagram of my theater room to show the relationship of my subs to my listening position. With peaks of 120 dB, my left and center (MLP) seats vibrated like tactile transducers were on a low setting and I really couldn’t feel much in my chest. In my right seat, which is right next to a sub, there was relatively strong vibration in my chair and mild punch I could feel in my chest.

With peaks of 125 – 128 dB, my left and center seats had strong vibrations and I felt a light sensation in my chest. With my right seat next to a sub, there were strong chair vibrations and a definite, strong tactile feeling in the chest – this is exactly what I had been looking for.
How do I re-create the same sensation in my left and center seating positions that I felt in the right seat next to one of the subs? Is the goal to get something like dual PSA S3600i subs that should add at least 6 to 10 dB greater response than my PB-13Us through most of the bass spectrum throughout the entire room? Does the displacement difference between my current 13.5” driver and an 18” driver create greater tactile feel? Or, am I better off adding another PB-13U next to my left seat for a great near-field experience there? Could I also add a relatively small sub (not more than 16” wide by 22” high) placed behind the center (MLP) seat be able to create tactile feel in the chest in that seating position?
 

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From looking at the highly technical drawing and the description of your experience as related to seating position, I'm getting the impression that you're attempting to correct with amplification and equalization a problem created by phasing.

That is to say that in the RLP (Right Listening Position) you're near enough to a point in space where the signals from each individual sub interfere constructively. But in CLP and LLP, you are displaced from the point of constructive interference and closer to a point of destructive interference. You can confirm this suspicion of mine a few different ways.

1) Play some pink noise through the subs, and walk around the room. Observe and note points where there is a significant difference in apparent level.
2) Same as above, but take measurements with UMIK/REW in various locations away from MLP
3) Turn off either sub, and execute either of the above procedures
4) Move one sub or the other to some radically different position in the room and note changes.

The issue with attempting to fix a phase problem with power is that the problem isn't the system, but the air itself. Because of the limitations of air as a medium, and resonances (both geometric and volumetric) within the room, it is physically impossible to overcome these phenomena with brute force... unless you're willing to risk the lives of your components.
 

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"With peaks of 125 – 128 dB, my left and center seats had strong vibrations and I felt a light sensation in my chest."
At what Hz is it hitting 125dB?

Design a 3-5dB hump in the frequency response curve between 40Hz and 70Hz or 60Hz to 90Hz to give you that tactile chest thump.
A flat response curve even down to 10Hz isn't exciting, it's frightening, produces pants flapping, door rattling, floor modulating, and hard breathing.
 

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Discussion Starter · #12 ·
From looking at the highly technical drawing and the description of your experience as related to seating position, I'm getting the impression that you're attempting to correct with amplification and equalization a problem created by phasing.

That is to say that in the RLP (Right Listening Position) you're near enough to a point in space where the signals from each individual sub interfere constructively. But in CLP and LLP, you are displaced from the point of constructive interference and closer to a point of destructive interference. You can confirm this suspicion of mine a few different ways.

1) Play some pink noise through the subs, and walk around the room. Observe and note points where there is a significant difference in apparent level.
2) Same as above, but take measurements with UMIK/REW in various locations away from MLP
3) Turn off either sub, and execute either of the above procedures
4) Move one sub or the other to some radically different position in the room and note changes.

The issue with attempting to fix a phase problem with power is that the problem isn't the system, but the air itself. Because of the limitations of air as a medium, and resonances (both geometric and volumetric) within the room, it is physically impossible to overcome these phenomena with brute force... unless you're willing to risk the lives of your components.
I gave this a whirl. Given how small the room is with the furniture in it, I found it somewhat difficult to do. I didn't find it easy to hear the difference so I moved around with my Radio Shack meter checking the dB in various locations. I noticed some slight variations and will try to look further into it.
 

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Discussion Starter · #13 ·
"With peaks of 125 – 128 dB, my left and center seats had strong vibrations and I felt a light sensation in my chest."
At what Hz is it hitting 125dB?

Design a 3-5dB hump in the frequency response curve between 40Hz and 70Hz or 60Hz to 90Hz to give you that tactile chest thump.
A flat response curve even down to 10Hz isn't exciting, it's frightening, produces pants flapping, door rattling, floor modulating, and hard breathing.
The 125 dB was from the scenes at the end of chapter 20 and beginning of chapter 21 in Batman - incredible bass. However, I have no idea what Hz it was and it would be the summation of sounds from a 5.2 system with 2 height speakers. I did run frequency sweeps (0 - 200 Hz) on my dual PB-13Us and they got to 108 or 109 dB before showing distress.

I caved in and ordered a pair of Power Sound Audio (PSA) S3600i sealed subwoofers - that's four 18" drivers. I should get them during the upcoming week. I know this will satisfy my curiosity as to whether I can do better or not. It will be a lot of fun testing them out and comparing them to my existing dual PB-13Us. Once I see how the S3600is do on their own, I'll put the PB-13Us in the room with them and see how all four work together - that should be interesting!

Thank you all for your help and ideas. I'll be sure to post back to let you all know how it all goes.
 

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I gave this a whirl. Given how small the room is with the furniture in it, I found it somewhat difficult to do. I didn't find it easy to hear the difference so I moved around with my Radio Shack meter checking the dB in various locations. I noticed some slight variations and will try to look further into it.
Ok... sound like you didn't experience anything as dramatic as I was hoping you would. What did your measurements tell you? How slight a variation are we talking about?
 

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Discussion Starter · #15 ·
Ok... sound like you didn't experience anything as dramatic as I was hoping you would. What did your measurements tell you? How slight a variation are we talking about?
It was a little challenging as I was holding the Radio Shack meter in my hand, but it looked as though the greatest drop was 2 to 3 dB. It seemed more apparent to me by the meter than it did by ear as I couldn't really hear the difference. It would have been more accurate to use REW and the UMIK on a microphone stand but I didn't have enough time. I'll see how the new subs do and will repeat this process with the UMIK if things don't seem right after installing the new subs.
 

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It was a little challenging as I was holding the Radio Shack meter in my hand, but it looked as though the greatest drop was 2 to 3 dB. It seemed more apparent to me by the meter than it did by ear as I couldn't really hear the difference. It would have been more accurate to use REW and the UMIK on a microphone stand but I didn't have enough time. I'll see how the new subs do and will repeat this process with the UMIK if things don't seem right after installing the new subs.
Mathematically, 3dB is pretty significant. That represents a factor of 2 in terms of power. I guess the bigger question is exactly where you measured those drops...

Did you attempt the same procedure with only one sub operating? And if so, did you see approximately the same fluctuations in level throughout the room?

FWIW, while the UMIK/REW combo might give you more accurate results than the Radio Shack SPL meter, the SPL meter will give you results that are far and away good enough for this purpose, so I wouldn't bother going to the trouble.*

*Others may disagree
EDIT: Considering the placement of your subs, the quick-and-dirty math says you should theoretically have a null in the center-ish of the room somewhere in the mid to high 70's Hz. I believe your REW graph shows that.
 

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Discussion Starter · #18 ·
The PSA S3600i subwoofers have arrived! I attached some photos of one next to one of my SVS PB-13 Ultras for comparison. One of the reasons for choosing the S3600i subs was the fact that they have a footprint nearly identical to the PB-13 Ultras. The S3600i is a bit taller and not quite as wide. The depth of both are nearly identical. I have the speaker grill removed in one of the photos to show the differences between the drivers. As can easily be seen, the S3600i is a sealed subwoofer whereas the PB-13U is ported but can also be configured in a sealed configuration.

I'll try to post next week feedback comparing the two subs as well as commenting on the difference in tactile feel and impact between the two subs.
 

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Discussion Starter · #19 ·

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Going from dual 13.5" drivers to quad 18's certainly should give you a boost, but it sounds like it was even better than anticipated. It nice when a plan comes together, isn't it? :D
 
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