This beneficial quality is accomplished by having a deep, flat bass response that, as per usual, the laws of physics do their best to get in the way of achieving. The dimensions of the rooms which we inhabit unhappily coincide with the wavelengths of deep bass which, as a result of the way bass energy reflects around a room, can create large peaks and dips in the response. Swings of +/-15dB(SPL) within the same octave are quite possible and the result is that one bass note can sound very weak, whilst a slightly different note can lift you clean out of your seat. Such an effect is possible with loudspeakers, but is more of a problem with subwoofers and the bigger and deeper the subwoofer, the greater the number of problem frequencies likely to be reached. It is, as with speakers, possible to ameliorate issues through careful positioning of the sub(s) and the listening position, but unless you have a dedicated listening room (and even then), it's not always possible to achieve the optimum solution.
To complete the job, electronic equalisation can be the finishing touch or an absolute necessity depending on the room, but either way, all but the luckiest people will benefit from it. Up to now, EQ devices have resided very much at the enthusiasts end of the market with their power and flexibility (and often the price) putting off many people from investigating further. The simple plug and play solutions at the other end of the spectrum have been lacking in both number and effectiveness, but the exponential rise of the subwoofer has created a sufficiently large market that solutions are starting to abound. The DSpeaker Anti-mode 8033 under review here is both at the bottom end of the price scale (£240) and of the plug and play variety, which means that it could answer the hopes and prayers of the vast majority of sub users out there, but even manages to include some interesting technology all of it's own.
I suppose it's a measure of my age that I'm still surprised how small some thing are. Sometimes small is good; In my youth portable audio came from a Sony Walkman WM-DC6 Pro (ask your dad) that was a real brick in the pocket, which is why I'm still perfectly happy with my Wolfson DAC equipped 4th generation iPod even though it has long since been surpassed in the skinny stakes. Sometimes small is bad; I like an item I've bought to be the largest thing in the box, or at least outweigh the instruction manual. Further more, anything that it is too small for my sausage fingers to operate is simply being small for the sake of it and as such is definitely bad. My personal piques aside, there is no technical reason why a small box of electronics which consigns it's power supply to a wall-wart plug should, or needs to be big and because the 8033 is entirely made of metal, it is very solid if a touch uninspiring to look at. The only issue of any note is that good subwoofer cables are dual screened and therefore heavy and stiff. As a result, unless you Blu-tac the Anti-mode down or wedge it under something larger, it is prone to not remaining where you left it.
Just to complete the picture, other items in the box include the aforementioned plug mounted power supply, the instruction manual and the measurement microphone. Internally, analogue to digital conversion and back is 16 bit resolution at a 10Khz sampling frequency, which is ample for the sub-bass frequencies the device operates over. The DSP brains of the 8033 is provided by VLSi's (the manufacturer of the 8033) own chip designed specifically for such purposes. The equalization is performed by up to 24 infinite impulse response (IIR) parametric filters, each able to target a frequency to an accuracy of less than 0.5Hz. The principle aim of these filters is not just to flatten the frequency response, but (and this is the clever bit) it also listens to how long a frequency will resonate within the room and compensate for it too. If it works, this is impressive stuff.
Does it Work?
Set up could not be simpler, because as long as you remembered to order an additional subwoofer cable (you now need two), you plug it in between the amp and the sub, plug the microphone into the socket on the front and plug the 8033 into the power supply and that's it. Top tip: Switch the 8033 on before the sub to avoid a truly mighty switch on thump.
Users inputting a stereo signal, such as from a stereo amplifiers preamp output will have to source a specific two-into-one RCA phono adaptor as the 8033 is a mono device. There is a specific cable, or instructions on how to make one on the DSpeaker website, so take note*. The only other connection option is a second subwoofer output that is phase inverted. This allows you to send a signal to and equalize two subwoofers at the same time. Just remember to set the phase/polarity on the second sub to 180deg or negative to compensate for the 180deg out of phase second output on the 8033. The reason for the provision of an inverted output is to enable a stereo amplifier as a bridged mono amp which is good for the DIY boys. There are no auto On/Offs, 12v triggers, remote controls or any other features that would aid a custom install or the like. This is EQ designed to do exactly that and no more.
The microphone is a tiny capsule heat-shrinked onto the end of it's own 5m signal cable and like all measurement microphones, it needs to be positioned at the point in space where the middle of your head would normally be. I use a cheap mic stand, but sticking it to a camera tripod would suffice. To start the automatic calibration process, you press and hold the two front panel buttons on the 8033 for 3 seconds and wait for the test tones to start. At this point I was greeted by the loudest bass test tones I've ever heard from a set-up device. The tones start very loud and very low, until the 8033 very quickly steps the volume down to a sensible level and then continues the sweeps upward in frequency. There are four sweeps each lasting about 30 seconds. I advise that, regardless of your subs normal gain settings, reduce them and let the 8033 turn itself up instead. This does not jeopardise the accuracy of the readings and because having the 8033 in circuit adds extra gain anyway, you gain settings are going to need adjusting once the equalisation is complete anyway.
Having run the sweep, the difference made to the response of the sub is not small. In part this is due to my room having a couple of very pronounced and aurally dominant peaks that need taming and also because the 8033 hit's them square on and tames them very effectively. As can be seen from the waterfall graphs above, the amplitude of two worst peaks have been tamed very effectively, but the impressive bit is how much the 'ringing' of individual frequencies has been curtailed. Take the example of the 35Hz peak; It's 10dB amplitude peak has been suppressed to about 3dB, which would be more than noticeable by itself and a difference worth paying for. However, looking at the top graph, at 0.3 of a second that same 35Hz is still registering 72dB. On the bottom graph, the same frequency has dropped way below that and into the noise floor by 0.2 of a second. Impressive. By the way, the dip in the response is a cancellation null and thus cannot be boosted and indeed the 8033 doesn't appear to have tried which is exactly as it should be.
The human ear is notoriously bad at differentiating ringing from a boost in SPL. In order for bass to sound tight and quick, you therefore have to reduce both, even though this may result in a response that looks less than flat. It isn't flat, but it will sound flat and that's more important. As can be seen above, the frequency response is far from flat, even though it's vastly improved, but in listening it sounds disproportionately improved. Kick drums now have a tight thud rather than a dull thump and all bass notes stop and start far more cleanly and the tonal difference between notes is far more explicit . Explosions on movies feel crisp and concussive, rather than simply booming away monotonously with flatulent rumblings and bass texture is much improved.
Better still, with the overly dominant frequencies reigned in, the sub can be played a bit louder to compensate giving greater presence and strength to the previously lacking lower frequencies. So, the sub sounds tighter, more tuneful and deeper in one fell swoop and that's exactly what EQ is supposed to deliver. The presentation of the rest of the frequency range benefits too. Voices sound less chesty and plummy, so gaining in intelligibility. Gandalf muttering his way round the mines of Moria is a fine example of this benefit. The scale of the music or movie soundtrack takes on a new spaciousness that is less anchored to the speakers and more about filling the gaps between them. These benefits are maximised by carefully level matching the sub to the speakers, as turning the sub up to taste, is effectively just creating one large modal boost across the entire sub-bass frequency range, which contradicts the reason for buying an EQ device in the first place.
And you could leave it there, but the 8033 offers the possibility of tuning a little further. Hold the right hand button down and another, single equalisation sweep runs, but this time it's results are averaged with those of the original sweeps. For the second sweep, the mic can either be placed in another listening position or moved toward the nearest corner of the room in order to emphasise the rooms modes, or anywhere else you see fit; The instruction manual has suggestions aplenty. You can run the second sweep as many times as you want until it achieves the blend you're looking for as the first sweeps remain locked in the memory, unless you press and hold both buttons in order to start from scratch. I tried the suggestions and made a few up myself, but maybe because the same modes are present across the commonly used listening positions (why EQ for somewhere you never sit?) the second sweep didn't make much of a difference in my room. The graph above shows minor improvements, but nothing that you could swear to hearing. A different room with a broader distribution of smaller peaks that differ from position to position significantly would undoubtedly benefit more, so don't rule this feature out on my findings.
DSPeaker Anti-mode 8033 Subwoofer EQ Review
So, to sum up; It's small enough to tuck out of the way, sturdy, simple enough for technophobes, effective enough for technophiles, as cheap as it currently gets and it works. That makes it an easy recommended buy.
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