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Simply Sound Audio Rumba 12 Subwoofer Review

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Simply Sound Audio Rumba 12 Subwoofer Review​

The subject of this review is the Simply Sound Audio Rumba 12. The Rumba 12 is an acoustic suspension subwoofer with a 12", front-firing driver. It measures exactly 16" cubed -- 16"x16"x16" -- and weighs a staggering 75 pounds.

The amp is rated at 500 watts, but there's no indication if that's RMS or peak. There is no quoted frequency response on the website or in the manual. Simply Sound Audio offers a 2 year warranty on the amp and driver, as well as a 30 day in home trial. The Rumba 12 is designed and manufactured entirely in the USA.

The review unit was supplied to me by the manufacturer, so I didn't go through the normal ordering process. Simply Sound Audio is a typical ID (Internet Direct) company though, meaning the only place to purchase them is directly from the manufacturer.

The unit came single boxed, but it was thicker cardboard then most I've seen. The sub was enclosed in a cloth bag, and suspended by a thick block of dense foam at each corner. Accessories include high quality carpet spikes with discs for hardwood floors, as well as a CD that contains the documentation. There is no printed copy of the manual included. The CD is somewhat unique, because it seems few companies supply those anymore.

Initial Impressions
The documentation could use a bit of attention. The owners manual seems to cover a lot, at first, but realistically doesn't give enough information about the Rumba 12 itself, especially some of the controls and options on the amp. For example, there's a toggle switch for Slope with settings for 12dB or 24dB, yet nowhere in the manual is it listed. I know what it's for, but I'll bet others don't. That's a nice feature to have, but it should be documented.

There's also a 2nd manual strictly for the PEQ (Parametric EQualizer). That one does a pretty good job of explaining what a PEQ is and how to use it, but there's really no need for that to be an entirely separate document. Both should probably be combined into a single PDF file.

One of the first things you notice about the Rumba 12 is just how heavy the thing is. When I saw it listed as 75 pounds on their website I figured that had to be a generous assessment, but it turns out to be spot on; I weighed the review unit and it is indeed 75 pounds. The thing is built like a tank, with 1" MDF for the front and back panels, and .75" for the rest. It passes the 'knuckle rap test' with ease.

The build quality is excellent. The finish is a satin black lacquer, which is applied in multiple coats. Except for a tiny chip the size of a pen point in the bottom right corner the paint was smooth and even. The thing feels rock solid. Most of the screws were properly tightened, with only two on the driver and two on the amp needing maybe 1/4 turn.

Strangely, the Rumba 12 looks better in person then the pictures would lead you to believe. I say strangely because the photo's posted on-line were taken by a professional photographer. What they fail to adequately reveal is the detail in the cabinet design. For example, the side panels have this very slight angle cut along the entire edge which gives it a refined look, yet that's somehow not fully captured by the pictures. Another unique design feature is that the side panels are taller then the front and rear panels (.5" total, .25" each on the top and bottom). This gives a singular impression unlike any other sub I've seen. I consider that a good thing personally, because it's certainly not your typical black square box sub. It's apparent Simply Sound Audio wanted to differentiate the Rumba 12 from the rest of the pack, and I think they succeeded.

One thing I'm still up in the air about is the fact there's no grill. I happen to prefer a grill - to me it gives the overall appearance of a more finished look. With the Rumba 12 it's not even an option. However, I have to admit that I derived an unexpected amount of enjoyment seeing the driver do it's work. This thing is an absolute beast, and watching it pound away was quite interesting.

The amp has somewhat of an industrial appearance, and could perhaps benefit from a bit more refinement. The markings for the various dials and switches silkscreened on the back plate are small and not terribly distinctive. The dials only show the extremes too -- the highest and lowest setting -- which makes minor adjustments challenging at times. Each dial does have a blue insert which enables you to clearly see what direction it's pointing in at least. The RCA input connector didn't feel as solid as the line level in connectors, but it wasn't flimsy either.

There's a large toroidal transformer bolted to the bottom of the cabinet. That's a nice feature, and uncommon for a sub in this price range. The amp generates little heat; no matter how hard I pushed the Rumba 12 neither the back plate nor transformer ever got more than warm. The Parametric Equalizer is also not something many subs costing what the Rumba 12 does include. It's an excellent way to tailor the sub to your exact room needs. The range of adjustment is phenomenal too, providing a full 24dB total of boost or cut (from -12 to +12). That's far more generous then most PEQ's provide. Finally, there's a toggle switch that allows you to select either a 12dB or 24dB slope for the cutoff. Generally speaking, acoustic suspension designs -- like the Rumba 12 -- tend to have a gradual decline in their output when they start to reach their limits. Bass reflex, on the other hand, tend to drop off far more rapidly. This switch allows you to tailor that behavior to your specific liking or need, which is a seldom seen option.

I had mixed results with the standby feature. Often times it simply would not go into standby mode, staying on no matter how long the receiver had been shut off. There was never an issue with it coming out of standby; as soon as I turned on the receiver the Rumba 12 would instantly wake up, without any hesitation. It also seemed particularly sensitive to a ground loop issue with my cable system. The standby timer is 40 minutes too, which seems rather long to me.

The driver is truly something to behold. It's the living embodiment of the word "over-built"; it weighs a staggering 32 pounds. There's a massive butyl rubber surround that feels very stiff, which is not only glued to the cone -- like every other driver -- it's stitched to it as well. The motor is enormous, with huge double stacked magnets and a bump-out to allow extended voice coil travel. It's attached to a cast aluminum frame that appears to be powdercoated. The voice coil itself is vented at the rear, with an outsized 1.25" vent, along with multiple vent holes between the base of the frame and magnet. It's hard to imagine anyone overheating this driver. The tinsel leads are woven into the spider, and there's what resembles some type of glass fibers impregnated into the very stiff pulp-based cone material. There's no question it's been engineered for the long haul.

I do have a few concerns about the driver though. The more excursion it's capable of the more potential there is for distortion. I didn't really hear anything untoward, which I suspect was partially due to the fact that the cabinet and driver are top notch, but it's something to consider. Another thing is the driver is secured to the cabinet using wood screws. For a driver this heavy and powerful t-nuts or inserts would probably be more appropriate. None of the screws came loose during the evaluation, so my concern may be unwarranted, but for a driver this heavy I would rather not have wood screws securing it.

The cabinet is stuffed with 10 ounces of polyfill, which has a story behind it (more on that later). Attention to detail is everywhere. For example, the plate amp fits perfectly into the cabinet cutout; I don't think there's even a 64th of an inch gap between it and the cabinet at any spot. There's an internal shelf brace that has a hole drilled in it for the speaker wires to pass through, so they're secured. The brace also has chamfered edges, similar to what the side panels have. Who does that? Who takes the time to design and build finishing details like that in a spot where 99% of the population will never even see them? To me that says good things about a company if they're willing to go to that length.

Hooking up the Rumba 12 is straightforward; plug in the RCA cable from your receiver to the LFE input and plug in the power. There are the ubiquitous left and right line level inputs but there's no summing function if you use them both, so the LFE input is the preferred method. That input also bypasses the Rumba 12's own crossover.

Next you set the gain, or volume, for the amp itself. I found the Rumba 12 had to be set on the "hot" side in order to match my other speakers properly. To get everything fully integrated I added +2dB to the subwoofer setting on my receiver, as well as drop my other channels by -2dB. Doing that will often limit the subwoofers headroom -- meaning it can't ultimately play as loud -- but I didn't notice a limitation during the evaluation. I found even with that the Rumba 12 was able to play pretty loud without struggling.

The phase is of the variable kind -- not just 0 or 180 degrees -- so you have complete flexibility on how you want to set it. Next you have to decide on how to set the slope, either 12dB or 24dB. There's probably no need to set it to anything other then 12dB though, since this is an acoustic suspension sub. Then comes the PEQ.

The Rumba 12's PEQ has three things that need to configured; the frequency you want to boost or cut, the level (amount of boost or cut to apply) and the "width". The latter setting is used to determine how much of the surrounding frequencies are affected by the first two settings. To disable the PEQ entirely just set the level to 0dB, which essentially negates the other two setting in the process. Without using a meter these adjustments will have to be set by ear, so you may be tempted to ignore them entirely, but that wouldn't necessarily be the best choice. A PEQ allows you to tailor the Rumba 12 for your specific home theater, which can provide a lot of benefits if done properly.

My living room is 13x17x8 (1768 CF), so it's not terribly large. The main seating position is approximately 11 feet from the subwoofer. Normally I do all my testing after the unit has been broken in for at least 15 hours, but in this case I waited for about 25 instead. That seemed prudent, given the stiffness of the drivers surround. It turned out to be a wise choice, because it did take longer then average for the Rumba 12 to fully break in.

When you look at the size of this sub, and couple that with the fact it's acoustic suspension, you initially think it might have some shortcomings in output and/or extension. Then you glance over at that imposing driver and think maybe it won't be too bad. Don't let the size deceive you; as it turns out, the Rumba 12 is one very powerful little subwoofer.

I found it to have a flat, neutral sound, without much, if anything, in the way of embellishment. To me this is the perfect way for a subwoofer -- or any speaker, for that matter -- to function. All I want to hear is what's on the soundtrack, and nothing else. Acoustic suspension designs seem more prone to behaving in this manner, which I suppose is partially why I've gravitated towards them for as long as I can remember. When the bass track was not a prominent part of the source material the Rumba 12 stayed in the background. When something more demanding was called for it came to life and pumped out deep bass.

The Rumba 12 has good dynamics, and sufficient headroom to allow all but the most demanding scenes to be played at an elevated volume level. Could I get it to bottom out? Yes, I was able to exhaust the drivers prodigious amount of travel; playing something like WOTW's, or select tracks off the Bass Mekanik CD at high volume, could induce slight mechanical noise. However, the Rumba 12 behaved perfectly when used under normal circumstances. Essentially, I didn't bump into it's limits unless I was trying to find them. Up until that point the sound was clear and powerful. Using the frequency sweeps on the Bass Mekanik CD I was able to get strong output down to 25Hz. By the time I got to 20Hz it had pretty much run out of steam, which is not at all unexpected given the price/size/configuration of the Rumba 12 (the PEQ was disabled during the frequency sweeps).

Attack and decay seemed particularly quick, making music hit fast and hard. Some of my reference CD's were played at a higher volume then I normally use for testing because the sound was so rich and powerful I just couldn't help myself. There was enough detail and articulation that I would classify the Rumba 12 as a musical subwoofer, not a designation I bestow lightly (I tend to be a bit picky in that regard). It doesn't quite have the accuracy to handle the more nuanced music, and lacks a slight bit of definition in general, but for the genres I listen to it did very well. I used 80Hz and 100Hz as a crossover point at various times and found it handled both with equal aplomb.

The owners manual states the preferable installation method is to forgo the carpet spikes and place the sub directly on the floor. This is so "The Rumba 12 will take advantage of physics and room acoustics together to provide deep pressurization as well as that tactile and tuneful response we love in our bass systems". The manual goes on to say "Generally speaking, do not use the supplied spikes. RUMBA 12’s work on the principle of the driver in a high-pressure sealed zone that directly couples it to the floor. Spiking the RUMBA 12 will decouple the woofer from the floor, which will lean out the bass response. If the floor is an older, very springy floor, spikes can be useful in reducing the influence of the RUMBA 12 on the floor".

I tried it myself -- placing the sub directly on the carpet, without the spikes -- but chose not to leave it that way. I must have one of those "springy" floors they referred to because there was too much resonance for my liking. I got a bit of additional tactile feel, but the droning was more then I wanted. Anyone buying the Rumba 12 should probably try it themselves though, in case their environment provides different results.

I'm not prone to watching at "reference level", so my assessments should be considered in that regard. I run each test scene twice; once while seated in my normal listening position, and then a second time while sitting on the floor a few feet from the subwoofer. This allows me to hear it as I normally would, yet still affords me the opportunity to determine if it's straining even the slightest bit. Both tests are run at the same volume level.

Like most people I have specific DVD's I use when testing subwoofers. A few of my favorites are Lord of the Rings: Fellowship of the Ring, Collateral and Avatar. Recently added to my repertoire are scenes from 10,000 BC, and the quintessential ULF (ultra low frequency) torture test; War of the Worlds. Each individual test is listed in the format of Movie: Scene.

Lord of the Rings: Bridge of Khazad Doom - There is an ultra low frequency rumble in portions of this scene, as well as significant amounts of impact generated by numerous structures crumbling. For a subwoofer to handle all of that properly it needs to be precise and capable of reaching very deep, otherwise a lot of it comes across as nothing more than annoying resonance. The Rumba 12 handled it all in stride.

With a subwoofer that lacks precision the aforementioned rumble merely bombinates, but that was not the case here; it was reproduced clearly and accurately. There was a little loss of definition if the volume was turned up high, but it only started to occur when it was far louder then I would listen under normal circumstances.

As some of the structures start to collapse you have a blending of sounds, some pretty low some not so much. The Rumba 12 had no problem reproducing anything that was occurring, and portrayed all the effects with the correct amount of emphasis.

My favorite part of this scene to play around with is the Balrog's roar. There's an instance when you see it for the first time that I just love to crank way up. He jumps out of a cavern and lands right behind the Fellowship with a thud, and then lets out a fire-breathing roar. I enjoy seeing how loud I can play that part, because when the volume goes up it just sounds cool. The Rumba 12 did a great job, and handled the volume with relative ease. The huge reverberations created when the Balrog's feet hit the ground as he chases after the Fellowship came through with a pronounced impact.

Collateral: Club Fever - This disc has the option of using DTS or DD for audio, but I only test with DTS. In general I've found DTS encoding has a bit of additional low bass and an overall greater depth to the soundtrack, so I've decided to use that exclusively for testing.

Although this scene doesn't contain a tremendous amount of LFE information it does have a driving musical soundtrack and over-emphasized gun sounds. The music portion I've found can cause trouble for a subwoofer because it does tend to drown out the voice track in certain spots, especially if it lacks clarity and speed. Because of that articulation is crucial. The Rumba 12 didn't even break a sweat with this one.

The club music was about as clear as I've ever heard, even with the crossover set at 100Hz (actually, it sounded better at 100Hz then 80Hz). Voices were not drowned out in the slightest, and the magniloquent gunfire was rendered to perfection.

Avatar: Assault on Home Tree - For those familiar with the movie this scene has low frequencies, ultra low frequencies, explosions, gunfire, voices and enough other things going on to provide a good test of virtually every component in your system. The Rumba 12 had no problems with this scene either.

As the gunships approach Home Tree you can almost feel the underlying intensity. The roar of their engines, the sound of the rockets being launched, the impact of each explosion, the crackling of the massive roots as the tree begins to list, and all the way to the point where it's toppled and crashes into the ground the low frequency reproduction was spot on.

The Rumba 12 handled this scene so effortlessly that I tried a few others, namely Battle for Pandora, Fall of the Heroes and Eywa. All of these additional scenes were delivered with the same ease and grace.

War of the Worlds: The Machine Emerges - The archetype... perhaps the most recognized subwoofer test scene of all time comes from a movie that's about 7 years old. The depth and volume of bass that occurs during a several minute span is simply amazing. If you want to see what your sub is capable of this scene can certainly be used as a barometer. With subterranean vibrations, exploding pavement and collapsing buildings you have ultra low, low and mid-bass frequencies pouring out of your subwoofer. One of the most punishing combinations there is, and an excellent way to really push something to the brink. As in the case of Collateral, the DTS audio track is used for this scene. For the most part the Rumba 12 did exceedingly well, only straining as the volume rose to substantial levels.

At a normal listening level, or even slightly elevated, the sound effects were rich and powerful. This was the only test scene that made the door of my hallway closet rattle. The individual elements -- buckling pavement, collapsing buildings, etc. -- each have their own individual sound profile, and all were presented accurately. So engrossing was it that I tried another two scenes; Heat-Ray and At The Window. Both exhibited the same degree of clarity and impact, and only when I really cranked up the volume did I get the driver to protest. Even then it was only apparent when sitting within a few feet of the subwoofer. In my normal listening position it wasn't really evident.

10,000 BC: Mammoth Hunt - During this scene there's either ultra low bass or mid-bass, with very little in between it seems. However, I've found this to be a good way of determining how a sub performs with nuances while being pushed hard. If it's struggling to hit the very low notes then the mid-bass suffers, and will come across as a jumbled mess (lacking in detail). If it can hit the low notes, but isn't articulate, then it tends to sound "thick" or "heavy", losing most of it's distinction. When portrayed correctly though, the really deep bass is what makes this scene. The Rumba 12 did a wonderful job here.

In the prelude leading up to the stampede the mammoths are simply milling about, but each earth-rattling thud from their massive feet is supposed to be felt as much as heard. When the stampede begins you then have dozens of raging mammoths running to escape. In order for this scene to work properly your subwoofer must be able to produce a tangible sensation of the ground shaking all around you. I sat there enthralled as this little subwoofer made that all come to life. It seems implausible to me that something of this size could produce such a corporeal impression, but it did. I actually played this scene multiple times, because I couldn't believe what I was feeling coursing through my chair.

I use a combination of lossy and lossless material -- MP3's and CD's -- to see how musical a subwoofer is, and in both instances the Rumba 12 shocked me with how well it performed.

My first test is always Johnny Lang's CD Lie To Me. The mix is beautifully done, and the simplicity of the music means you can easily focus in on nuances. The detail from the Rumba 12 was impeccable, even as I started to crank the volume. And crank it I did, all the way up to "that's starting to hurt my ears" level. Yet the Rumba 12 kept pace, without ever once breaking stride. On virtually every type of music I sampled the results were the same; the precision and speed hardly ever faltered.

I don't have any pipe organ music to use for testing, but I did pick up a copy of Bass Mekanik. For those unfamiliar with this "music" (and I do use that term loosely)... it's essentially the source material people use to show off their car audio systems at those SPL (volume) contests. Consisting of nothing more than ridiculous electronic music, it has little value save for one; it contains some very deep bass. I hammered the Rumba 12 mercilessly with this CD and it kept it's composure on all but the deepest notes. Excessive volume could undo it's poise, as you would expect, but in order to unnerve this thing the volume had to be higher then any $550 subwoofer should be expected to play, especially when you consider the depth of bass in these songs.

After pounding the Rumba 12 for several hours -- with movies, music, test tracks, and various sound effects (rocket launches, fireworks displays, locomotives, etc.) -- the amp was nothing more then warm. Knowing that the toroidal transformer is attached to the bottom panel I felt around their as well, but even that wasn't hot. I have never punished a subwoofer like I have this one so I expected a lot more heat, but it just never materialized.

The support provided by Simply Sound Audio can be summed up in a single word; exemplary. The reality is this company is a one man operation, and the guy who does it all is named Murrel Gray. Almost everyone who owns an MFW 15 subwoofer is already familiar with Murrel, so it's not like he hasn't already proven himself. Building his own line of subwoofers seems to be a natural extension to what he already does. A perfect example of the support you get would be the polyfill situation I alluded to earlier.

While doing the critical listening portion of my evaluation I noticed what seemed like a little overhang, a slow response on occasion, which could make the sound a bit "thick". Users of ported subs will often hear something like this -- which is commonly referred to as 'group delay' in that case -- but sealed subs don't generally have such an issue. Part of my normal process is to take the subwoofer apart so I can see how it's built, and also to get some pictures of the driver, amp, cabinet internals, etc. When I did that with the Rumba 12 I noticed there was very little damping material being used (turns out it was 2 ounces). That seemed insufficient to me, so I contacted Murrel to discuss it with him.

Now, when I say "contacted Murrel" it usually means by phone. Why? It's his preferred method of doing support. That's not to say he doesn't respond to emails -- because he does -- it's just that he would much rather speak over the phone (to the extent that his home page actually contains his phone number). In this day and age that's exceedingly rare. After speaking with him for a while, and explaining what I found/felt, we hung up. I figured that was the end of it; I'd provide some feedback and he would take it under advisement. What happened next was anything but that...

The next night I get an email from Murrel that has all kinds of graphs in it. Each one showed the frequency response with a different amount of polyfill damping, from 0 ounces to 16 ounces in 2 ounce increments. That must have consumed several hours to gather that type of data. Based upon that we decided 10 ounces would be the ideal amount, so all future subs will come with that much in them. Very uncommon to get that level of response and commitment from any company, but that's not where this story ends.

The next day I get another email, this time from FedEx. Simply Sound Audio is sending me 10 ounces of polyfill so I can stuff the evaluation unit with the same amount that we deemed ideal. I considered that excellent customer service, but did you think Murrel was done yet? Think again. Two days after the FedEx email I get yet another message, this time with a link to a 450 meg HD video file. It's a 7 minute video he took of what the frequency response graph looks like in real time while watching a movie. But that's not all; along with the perpetual graphs being displayed on his laptop there's also an oscilloscope hooked up so I can directly compare the signal to the output! He wanted to show me just how clean and accurate the sound was now that the unit had 10 ounces of polyfill. Who on earth goes to that extent to support their products? Simply incredible...

The difference between 2 ounces and 10 ounces is actually palpable; the driver moves less frenetically when it's being pushed, it starts and stops faster and has a slightly more detailed sound overall. Because of the testing he did all future Rumba 12's will have 10 ounces of stuffing, so everyone will benefit from it.

This wasn't a one-shot deal either. Every single time I spoke with him on the phone he was the same way; courteous, polite and very helpful. To be honest, it was the rare call that was less then 20 minutes. He's just a very personable guy.

Sometimes the Conclusion section of the review is the easiest part to write, because some overriding thought or theme is constantly evident. That's what happened in the case of the Rumba 12. I kept finding myself thinking "is this guy making any money on these subwoofers?". He must work on some pretty slim margins, that's for sure. I have some experience in the DIY area, and have been integral with the design of subwoofers myself, so I have more then a passing familiarity with what goes on 'behind the scenes'.

Without question, the driver being used is high-end. It's hard to imagine the unit cost isn't somewhere in the vicinity of $200 each. And the amp, with 500 watts, a toroidal transformer and PEQ? It has to be around the same price as the driver. What about the enclosure? The materials being used, the level of detail in the panel cuts, the amount of craftsmanship to construct them, coupled with a multi-layer lacquer paint job means they have to be at least $100 each. Of course there's always the ancillaries, like wire, screws, damping material, spiked feet, and the like. What about packaging? Boxes, foam, cloth bags - they all cost money as well. And that's to say nothing of the value of Murrels time to build them. Even if you price things conservatively it adds up to be around $500. For a subwoofer that sells for $550? Like I said, how does this guy make any money?

The bottom line is the Rumba 12 represents an extraordinary value. For those looking at a small acoustic suspension subwoofer this one should be at the top of your list. The output is clear, articulate, deep and powerful. It's all wrapped up in a nicely designed and styled enclosure that feels as though it was hewn from a piece of granite. With support that's second to none -- along with an amazing price/performance ratio -- the few flaws it does have are pretty easy to overlook.

For those interested in my subjective assessment it's that the Simply Sound Audio Rumba 12 is highly recommended.

See the Simply Sound Audio Rumba 12 Subwoofer Review Discussion Thread for Questions and Comments


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