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SVS PB13-Ultra Subwoofer Design Overview

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The PB13-Ultra utilizes a very robust and well engineered custom 13.5” driver capable of handling the excursions and power needed to produce serious high output low bass.  The woofer has an open but strong cast aluminum frame and a very large underhung magnet and motor assembly (tipping the scale at 55lbs) with a vented pole piece, large dual spiders and a large parabolic “high roll” surround comprising the suspension.  Underhung motors are very costly to make and the THD levels are generally far lower than conventional overhung designs. Incidentally the surround is physically stitched to the cone which is an expensive measure but goes to show you how serious the effort that went into developing this driver really is. In addition The SVS driver is said to incorporate a copper inductance demodulating circuit in the motor which is a good sign with a motor containing this much steel in it. Otherwise a driver such as this might suffer from large inductance variations during high excursions or might exhibit a peaky response with a rolled off top end, such as a 6db octave roll off after 50Hz for example. That sort of response characteristic is sometimes seen with big high power subwoofer drivers having high inductance and limits their output and efficiency in the top of the bass range. The cone is also a strong and yet light piece that I felt was rather attractive with the weird, reflective and almost holographic surface at times.  It is a serious piece of equipment that gives the impression that it means business. Very few manufacturers spare such expense on a quality driver like this, but as you will see in the measurement portion of our review, it pays off in droves.   

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SVS PB13-Ultra: Anatomy of a Subwoofer at CES 2016

The STA-1000-D Sledge amplifier is rated at 1000w RMS and is class D. SVS claims that the amplifier is both more powerful and more efficient than the older 750w BASH amplifier and in addition to the extra power, that fine tuning of the DSP compressor and limiting circuits have enabled them to safely squeeze an extra bit of output from the PB13 as compared to the older BASH model than what would be expected just from the power increase alone. Extra headroom is always great, but that is not even the big story with this amplifier platform. That would be the on board DSP. This platform has an interface utilizing an LCD screen and a single knob / push button to control the settings of everything from parametric EQ to high and low pass filters and volume. SVS calls this interface I.F.C., short for integrated function controller. There is a generous array of adjustments available as we will get to later in the review.

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SVS PB13-Ultra Sledge Amplifier

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SVS PB13-Ultra Backpanel 

The drive unit and amplifier are mounted in a heavily built MDF cabinet that is comprised of 1” material with 2” thick material used for the driver baffle.  It is also extensively braced with the addition of a nice support brace for the heavy driver motor that it fits into like a glove. Make no mistake this cabinet is very inert which is quite obvious because a quick knuckle rap test results in no more than a deadened “thunk” sound. There is also extensive damping material inside the cabinet. The three, 3.5” inner diameter ports have enough length that they needed to take a 90 degree turn inside the cabinet to fit them and achieve the low tuning desired.  This is an extremely well built cabinet and should be an envy of its peers.

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SVS PB13-Ultra Internal Cabinet 

The PB13-Ultra is designed as a bass-reflex alignment primarily, with variable extension achieved by the plugging of a port and switching the amplifier DSP settings to the appropriate mode. But, the PB13-Ultra can also operate as a sealed subwoofer through the use of the supplied foam port plugs to plug all three of the ports and switching the amplifier DSP to the “sealed” mode. With all three ports open the subwoofer has a 20Hz tuning. By plugging one port the tuning is dropped to 16Hz for added extension. If all three plugs are inserted into the ports and the DSP switched to the “sealed” setting the sub is put into sealed mode, which offers the 12dB/octave roll off of a sealed alignment and may work better in smaller spaces or those having large amounts of low frequency gain. The original PB13-Ultra also had a fourth, 10Hz mode where two ports were plugged, but they have since dropped this mode from the line-up. Perhaps they did so due to it being too compromised on port area, too close to the sealed alignment in response shape and performance, or simply as taking up unneeded processing power in the DSP unit. Whatever the reasons, SVS no longer recommends this on the current PB13-Ultra’s.

The finish of the review unit sent was American cherry veneer which had a very nice grain and color to it. If I was to be picking one of their finish options for myself, this is the one I would’ve picked. The large radius metal grill was sent with the unit and was a very heavy gauge and probably an expensive piece to manufacture. I like the fact that the SVS uses magnets to secure it and does not have any tabs to snap off or scratch the finish. It’s a nice touch and has a little bit of a “cool” factor to it as well. Both the driver and amplifier are flush mounted. The enclosure sports a very large round over on the top and bottom panels which gives it a nice rounded look. The PB13 is rather large as far as most commercial powered subs go and is also quite heavy at 155lbs, so it may not fit into some domestic settings, but that is the price of powerful deep bass. The overall parts and build quality is definitely first rate in any case. The substantial price tag appears to be at least partly going towards some serious components.

 

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Recent Forum Posts:

dmusoke posts on February 15, 2014 02:36
fuzz092888, post: 1016877
Based on the CEA results, some of the other graphs, and my own personal preferences/experiences I would go with the 20hz tune, at least based on the raw numbers. The 20hz tune is going to have lower distortion overall, in room gain will boost the extension you get slightly and you'll get more output/have more headroom over the 15hz tune.

As to the distortion question, at moderate volumes with distortion far less than 5%, I doubt you'd notice a difference between either mode. At higher volumes, depending on the content you may notice that extra bit of extension, you may not. Distortion may begin to come into play, but I doubt it. Both tunes will, by my estimation still sound similar. At full on reference playback with a demanding soundtrack is where you'd probably notice the biggest difference. Since 20hz and below is more felt than heard, I'd still probably go for 20hz tune since I'm not really seeing enough meaningful output over the 20hz tune to risk rising distortion while also sacrificing output and increasing thermal compression. IMHO of course and I'll throw in the disclaimer that I've never actually heard this particular sub so my opinion might be different if I did get to audition it. Then again maybe not as well.

I agree… Thank you so much Fuzz for the help you've provided explaining to me the details i was confused about .
fuzz092888 posts on February 13, 2014 01:26
dmusoke, post: 1016873
I see what you are saying now with the graphs. You're observations are correct in this regard. Is distortion of 10% or greater at 20Hz or lower audible? If so, then I'm tempted to think that the 15Hz mode is best overall based on the graphs iwth THD less than 5% up to the tuning frequency?

Based on the CEA results, some of the other graphs, and my own personal preferences/experiences I would go with the 20hz tune, at least based on the raw numbers. The 20hz tune is going to have lower distortion overall, in room gain will boost the extension you get slightly and you'll get more output/have more headroom over the 15hz tune.

As to the distortion question, at moderate volumes with distortion far less than 5%, I doubt you'd notice a difference between either mode. At higher volumes, depending on the content you may notice that extra bit of extension, you may not. Distortion may begin to come into play, but I doubt it. Both tunes will, by my estimation still sound similar. At full on reference playback with a demanding soundtrack is where you'd probably notice the biggest difference. Since 20hz and below is more felt than heard, I'd still probably go for 20hz tune since I'm not really seeing enough meaningful output over the 20hz tune to risk rising distortion while also sacrificing output and increasing thermal compression. IMHO of course and I'll throw in the disclaimer that I've never actually heard this particular sub so my opinion might be different if I did get to audition it. Then again maybe not as well.
dmusoke posts on February 13, 2014 00:25
I hope the new SB13 gets reviewed soon…
dmusoke posts on February 13, 2014 00:24
fuzz092888, post: 1016655
Looking more closely at the graph, you'll see that the 15hz mode doesn't offer lower distortion than the 20hz mode, except below the tuning point. The swept tone graph isn't mislabeled.

This graph shows the same thing except with a 110db tone. The distortion of the 15hz mode starts to raise higher than the 20hz mode at around 55hz and continues to rise higher than the 20hz mode until the 20hz mode gets close to the tuning frequency. Below the tuning frequency, the 15hz mode has lower distortion, as it should, since it is tuned lower. The tradeoff for that extra extension is rising distortion starting at 50-60hz. The CEA results show the same thing.

Data-Bass

I see what you are saying now with the graphs. You're observations are correct in this regard. Is distortion of 10% or greater at 20Hz or lower audible? If so, then I'm tempted to think that the 15Hz mode is best overall based on the graphs iwth THD less than 5% up to the tuning frequency?
fuzz092888 posts on February 12, 2014 08:37
Looking more closely at the graph, you'll see that the 15hz mode doesn't offer lower distortion than the 20hz mode, except below the tuning point. The swept tone graph isn't mislabeled.

This graph shows the same thing except with a 110db tone. The distortion of the 15hz mode starts to raise higher than the 20hz mode at around 55hz and continues to rise higher than the 20hz mode until the 20hz mode gets close to the tuning frequency. Below the tuning frequency, the 15hz mode has lower distortion, as it should, since it is tuned lower. The tradeoff for that extra extension is rising distortion starting at 50-60hz. The CEA results show the same thing.

Data-Bass
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