SVS AS-EQ1 subwoofer EQ

SVS AS-EQ1 subwoofer EQ – from £649

Available from: Kent Home CinemaSubsonic Sounds
Manufacturer: SV Sound
Tested with: Onkyo TX-SR876, Cinepro 2K6, XTZ 99.36 & 99.26, M&K CS22, M&K LCR36 & SVS PB13Ultra

Introduction – What is Room Correction and why do I need it?

Room Correction technology such as Audyssey MultEQ XT has become almost a standard feature on mid range AV-Receivers and Processors, so why does SVS think we need a standalone unit to perform a similar task focusing only on the subwoofers in your system?

Anyone who has spent serious time integrating a subwoofer into a problematic room can probably answer that for you. Whilst most ‘on-board’ room correction applications can tame a lot of the problems inherent in most rooms, sub bass frequencies remain the most noticeable and difficult of all to correct and the limited power and resolution of on-board solutions are sometimes not enough.

The reasons why sub bass is so problematic is due to how these low frequencies interact with your room, creating nulls and peaks in the frequency range that produce either exaggerated or reduced output levels at different frequencies. These phenomena also occur in the time domain where these exaggerated frequencies continue to ‘ring’ before eventually dying away long after they should, muddying the sound. The result of these effects is difficult to predict in any given room but can be heard as ‘boomy’ uncontrolled bass, ‘unsubstantial’ or ‘missing’ bass and also as a lack of timing, detail and ‘musicality’. The goal of Room Correction or Room Equalisation (EQ) is to compensate for the worst of these effects by altering the input signal sent to the speakers (or in the case of the AS-EQ1, the subwoofer) and essentially remove the room and its problems from the equation.

Other EQ Tools to consider

There are many software applications and devices available for Room Equalisation, Room EQ wizard takes advantage of existing pro audio hardware such as the Parametric Equaliser functionality of the Behringer Feedback Destroyer, others have been specifically designed for the task, such as Velodyne’s SMS-1, XTZ’s Room Analyzer, Audionet’s Carma and of course Audyssey’s high end £2500 Sound Equaliser.

All have their pros and cons and having used or owned most of these over the past few years (the exception being the Audyssey Sound Equaliser; see Phil Hinton’s AVForums Review) I can honestly say they vary from complicated and time consuming to extremely complicated and relationship testing! Even the most user friendly EQ device (the SMS-1) has always required some knowledge of the science behind what is happening in your room, as its ‘Auto’ setup routine is next to useless and manual setup is really a necessity.

If you have no interest in what Room EQ does or how it works and just want the best possible sound from your subwoofer, these products are probably not for you.

So it is fair to say there is a gap in the market for a ‘plug and play’ Subwoofer EQ device that doesn’t cost the earth and this is niche SVS are hoping to fill with the AS-EQ1 Subwoofer EQ.

SVS & Audyssey

The SVS AS-EQ1 Subwoofer EQ is born of the collaboration of two companies, SVSound and Audyssey Labs.

SVS are well known online but much less so on the high street, in fact there is only one Street in the UK you are likely to come across the SVS brand and that is at their UK distributors, Kent Home Cinema. SVS has traditionally sold direct to the public cutting out retailers and passing the savings on to the consumer. Global expansion has meant the development of relationships with local distributors but SVS still delivers excellent performance for the money, making them a firm AVForum favourite.

Audyssey is probably a more widely recognised company thanks to the inclusion of their Room Correction technology on so many AV Receivers over the past few years, including the likes of Denon, Onkyo and Marantz.

The AS-EQ1 is designed to EQ up to two subwoofers by calculating the effects caused by your room and compensating for them by altering the subwoofer(s) input signal. Unlike the Audyssey MultEQ XT implementation found on many Receivers and Processors, it focuses solely on the subwoofer channel, it also has double the filter resolution and a maximum of 32 rather than 8 possible sweep positions.

The SVS AS-EQ1 appears to be aimed squarely at those people who have invested in a mid to high end audio system with one or more subwoofer(s) and either do not have an EQ device built into their Receiver / Processor (Audiolab 8000AP and Rotel RSP 1570 owners I am looking at you), or want to improve on the onboard Room Correction they already have.

Best of the rest

Before the AS-EQ1 arrived on the scene, Velodyne’s SMS-1 was in my opinion the best, affordable Subwoofer EQ tool available. It allows manual tweaking of the frequency response, crossover and a host of other parameters giving plenty of flexibility and is relatively straightforward to use once you understand the way sound waves interact with your room. It is still an enthusiasts’ or ‘tweaker’s’ tool rather than a plug and play system and it does have a few problems. The visual plots it produces and indeed the filters it applies, only work in 2 dimensions, meaning problems in the time domain such as ringing cannot be visualised or addressed. Although it does support multiple subwoofers they are all fed the same signal so are in effect treated as a single subwoofer. This is not a very efficient use of the limited filters on the SMS-1 as different subs in different locations in the room will have very different output characteristics. If you use multiple subs with the SMS-1 at the very least you would need to utilise the individual phase controls on each sub to again aid integration.

In fact for those who haven’t tried integrating multiple subs it is a lot more complex than a single sub and even with very useful tools like the SMS-1 it is not easy to get the optimum results. The AS-EQ1 promises a lot for dual sub owners in that it is designed to EQ each sub separately and then together to theoretically get the best possible performance and integration from dual sub setups. The biggest advantage of the AS-EQ1’s approach is that it will be almost as quick and easy to setup two subs as one which is an extremely attractive proposition for those who value their personal relationships!

The big question is, how does the AS-EQ1 compare to other products on the market in practice and of course, is it worth the £649 SVS are asking?

What’s in the box?

The AS-EQ1 arrived well packed with the main white cardboard packaging fitting snugly inside a standard brown cardboard shipping box. Opening up the box reveals the various components, while the AS-EQ1 itself is bagged and well protected at either end by dense packing foam, some of the other components such as the cables and DVD case are left to ‘rattle’ around in the box. I can’t see this leading to any damage to the components during transit but it would have been nice if the entire contents were more secure.

The image above shows the full contents: Manual/Software DVD, Measurement Microphone, 3 metre USB cable, power supply, pass-through cable, including rubber feet for shelf mounting and ‘ears’ for rack mounting, plus the optional SVS branded RCA interconnect. Below you can see a closer view of the interconnects on a pre-production model without the relevant warning and certification labels.

The AS-EQ1 subwoofer EQ with the magnetic front panel attached, removed to reveal the front connections and the rear shot of the final production model.


The unit is well constructed and feels solid and substantial although it is not particularly heavy. All the connectors are sturdy and even the power switch has a quality feel. The choice of a magnetic front panel to keep things tidy is an idea shared with the much more expensive Audyssey Sound Equalizer Balanced and although a less elaborate design, it gives an attractive and austere finish to the product.

The only thing I would have liked is an EQ on/off button on the front. Ok, I know, this is only likely to be used to ‘show-off’ to your friends how good room EQ is but I still want one! Currently the only way to switch the EQ on or off is to connect the USB cable to a computer and control it through the software.

The included cables and interconnects are all perfectly adequate for the job in hand.

Those with rack mounts or ‘AV Cupboards’ may be pleased to hear the unit runs quite cool.

System Configuration

The AS-EQ 1 can be used in a number of system scenarios:

  1. You can use the AS-EQ1 in conjunction with your Receiver or Processor’s onboard Room Correction system, be it Audyssey or something else.
  2. You can use the AS-EQ1 without any onboard Room Correction
  3. You can use the AS-EQ1 to integrate one or two subwoofers and unlike most alternative solutions, each subwoofer will be Equalised separately rather than as a complete unit. If your Receiver or Processor has dual separate subwoofer outputs, these signals can also be equalised separately.
  4. If you have onboard Room Correction and you setup your Receiver or Processor using it in conjunction with the AS-EQ1, you can then turn off the onboard Room Correction if you should so choose, without causing any problems or having to re-do the AS-EQ1 setup.
  5. If you have onboard Room Correction and you setup your Receiver or Processor without using it, you cannot then turn it on without starting the whole process from scratch, or you will be effectively cascading the two Room Correction systems and produce poor results.


Anyone familiar with Audyssey’s onboard products will recognise the basic premise of the AS-EQ1 setup procedure. Place the supplied mic at various positions in and around your listening areas and let Audyssey run it’s sweeps and calculate the best filters for your room. You don’t need a PHD to get the most out of onboard Audyssey implementations.

The AS-EQ1 however is more elaborate in its setup procedure and you really need to read the manual thoroughly before and whilst performing the setup, as getting a step wrong could result in poor performance. Anyone interested in the full setup procedure can view the manual here:…1_1_lowres.pdf

The manual is provided on a disc in PDF format, it is well laid out and easy to follow. It is certainly one of the best presented manuals I have had the pleasure of using in some time and anyone following it precisely should not have any problems. Some might prefer a printed copy but this would have added to the cost and I am happy enough a few trees have been saved.

One thing for users to be aware of who already enjoy the benefits of their onboard Audyssey implementation, is that you will be required to re-run your entire set of sweeps as part of the AS-EQ1 setup, so expect to be using the best part of an hour the first time you set this up. The AS-EQ1 is connected to your Receiver or Processor via the included cable and your Receiver’s mic is plugged into the AS-EQ1. When your Receiver’s Room Correction system pings the subwoofer, the AS-EQ1 loops that signal back to the Receiver mic input, so during the second stage of the setup routine the AS-EQ1 can perform its job without cascading the effect of the Receiver’s Room Correction system, clever stuff.

Finally the AS-EQ1 is disconnected from the Receiver’s EQ mic socket and you can start the Subwoofer setup with up to 32 sweep positions, depending on the size of your room or listening position.

The final process is to balance the levels of the speakers and subwoofer(s) after this is completed you can view your before and after room response and choose to re-run the AS-EQ1 setup or save and upload the results to the device. You are then presented with a set of pretty graphs showing the average response in your ‘listening bubble’. While I can see how having a 3D waterfall graph might only confuse people, it is a shame this is not an option for those that are interested in what is going on in the time domain. I have included some of my own waterfall graphs in the appendix for those who are interested.

To really test the AS-EQ1 I placed the subwoofer in a known trouble spot as well as the ‘best’ position within, my room.

Position 1 – To right of main listening area, note the 20hz dip

Position 2 – Right of right hand speaker, much less to trouble the AS-EQ1

Note: A single subwoofer was used for this review owing to the limited time available with the AS-EQ1, hopefully I will be able to take a second look in a few weeks time.


During one stage of the setup procedure you are required to balance the levels of the different speakers in your setup using an RCA output from the AS-EQ1 and the Multi-Channel inputs on your Receiver or Processor (for processors without multichannel inputs, any full range analogue input is ok). The AS-EQ1 software then outputs pink noise which you use to set the levels correctly.

One thing that was immediately apparent was that the level the software measured as 75db, was in fact much quieter than the level shown by my Radio Shack SPL meter, by about 6db in fact. Whilst this isn’t a problem particularly, as the goal is making sure all the levels are matched, it does mean that once the process is completed those wishing to set the reference level of +/-0 dB on their Receiver or Processor display, will need to manually set the levels again being careful that each channel is raised by the same amount.

It seems Audyssey could make life a little easier for us if the differences between the standard Audyssey MultEQ mic and the AS-EQ1 mics was accounted for within the software or perhaps more usefully, the levels were calibrated closer to such a common tool as the Radio Shack SPL meter.
This is however a minor gripe but it could catch out some users assuming Audyssey is setting up their system at reference level when the volume dial says +/-0 dB, which it is not.

So, how does it sound?

I see little value in comparing the AS-EQ1’s performance to that with no EQ present as I think the graphs shown above give a clear indication it will sound a lot better than with no EQ at all. My observations below compare it’s performance with the best I was able to achieve with onboard MultEQ XT, the SMS-1 and various combinations of the two.

Flight of the Phoenix (2004) – Blu-Ray

The first test piece is probably one of the best for tripping up subwoofers because there is just so much going on down low that an uneven frequency response can easily mask the detail within the soundtrack.

The infamous crash scene is a monstrous bass-fest but there is detail buried within the soundtrack that in my room can be completely swamped by an uneven response. I know this piece like the back of my hand and have heard it on several subs in my room, including the much more expensive Aerial Acoustics SW12 and Velodyne’s DD15. All I can say is that my first instinct was that the subwoofer channel must be set way to high and I immediately reached for my SPL meter and checked the levels on the Receiver. The levels were all matched so I switched back to the scene. After a few seconds I understood my initial reaction, the bass wasn’t louder, it was clearer, I could hear so much more going on, little nuances that are so often lost.

A couple of examples include the moment when the engine finally gives up. On some setups/configurations almost nothing happens here but this is finally revealed as a big bass moment that brought a big smile to my face, as I have chased this little scene with various subs determined to hear it at its best. A little later on there is another moment when an oxyacetylene canister or some other combustible object hits the ground, I have never heard the sound I felt should have gone with this moment and wondered if it was just not added to the mix but my new best friend the AS-EQ1 pealed back the noise to reveal it, subtle but definitely there.

Iron Man (2008) – Blu-Ray

Again I couldn’t get over the amount of bass that seemed to be present here, it was like my subwoofer had been given a new lease of life, the energy was incredible and it had me giggling away as my sofa wobbled across the room. The effect was intense but it didn’t feel exaggerated or dominating (this is a bass heavy mix) it just sounded much more energetic and clear.

Other Blu-Rays

I ran through several more of my favourite demo pieces, including Master and Commander, Cloverfield, Kung-Fu Panda and each time my smile got broader. It almost brought a tear to my eye, the AS-EQ1 has done for my room what nothing else I have tried could. I have finally felt the true performance of my subwoofer, something I have been chasing for years and have spent untold frustrated hours tinkering and measuring to that end. Then along comes this new fangled gadget which within an hour has made a mockery my best efforts!


Music is almost always more revealing of poor subwoofer setup than movie soundtracks but the AS-EQ1 doesn’t care what is thrown at it, timing is spot on, the presentation is clear and open and even with the sub sitting within a meter of my right ear, I couldn’t locate it at all.

Whether it was the guitar ‘slapping’ of Rodrigo Y Gabriela or the synthesised bass lines of Lady Gaga everything sounded more lively, with plenty of impact but not in the least bit overbearing.

The most compelling evidence was when I finally removed the AS-EQ1 from the setup and reconfigured for the SMS-1. Let’s just say I won’t be listening to any music until my memory of what I have been lucky enough to experience these last few days has worn off. Time to save those pennies I think…

The Good stuff

There is a lot to like about the AS-EQ1, most importantly it works incredibly well but the one thing that places it head and shoulders above anything else I have tried is ‘time’. I have probably spent hundreds of hours over the past few years, tweaking crossovers, running sweeps and dragging heavy subs all over the place. There have been a few weekends where I am sure if my wife heard another ‘whooooooeeeeeeep’ noise coming from the ‘out-of-bounds’ lounge, I would have been strung up by my tenders!

Sure the AS-EQ-1 takes a little while to setup but this product is literally set and forget. Nothing else out there I have tried even comes close after hours of tinkering, to what this can do in under an hour. Sure it could have more manual tweaking options but you know what, I have had it with tinkering, with straining to hear if the last hours effort sounded marginally better than the 4 before that. This thing just works and I am finally so happy to just listen and enjoy and not second guess everything I am hearing.

Value for money?

£650 may seem like quite a lot to ask for a box of tricks to EQ a single channel of your Audio system but when you compare it to the cost of what I regard as the best alternative, the Velodyne SMS-1 at around £550, it suddenly becomes much more palatable. For convenience as well as overall performance the AS-EQ1 is in my opinion, by far the superior product and that £100 difference could save your marriage, or mine at any rate.


Ok, so you probably gathered I quite like this diminutive box of tricks, so if I put my ‘nit-picking’ head on, what would I change? There is always the price, £650 puts the AS-EQ1 out of sensible reach for owners of subs that don’t cost at least that much. You could spend £650 to upgrade a £400 sub and I dare say you would love the results but could you really justify it when that extra money could buy you a far better subwoofer?
Other ‘would-be-nice’ features:

  • Improved level matching and/or calibrated mic
  • 12v Trigger
  • EQ on/off button on the front
  • Individual EQ of up to 4 subs
  • RS232 Control
  • Optional Curve Presets – despite liking the fact this product is set and forget, some people will like more control and I think preset curves would be a nice halfway house between full auto and a more complex ‘manual’ system.
    When I put this to Ed Mullen of SVS: ” I would argue here DEQ is by far a better solution than any static “house curve”, which is only effective at one playback level. As you heard, the AS-EQ1 provides the best sounding bass of any device, all with a flat FR and no house curve. “
  • Balanced Connections
  • Front power switch – not necessary but with my gear in a cupboard it would be convenient for me anyway.
  • Vista x64 and Mac OSX compatibility
  • Improved internal packaging

Admittedly most of the above would likely raise the price yet further and I think that SVS would miss out on a chunk of the market that this product will amply satisfy in its current guise.


If you have problematic bass issues in your room, are fed up with tweaking or just want to hear your sub(s) at their very best, I whole heartedly recommend the SVS AS-EQ1 Sound Equaliser, it is quite simply the simplest, quickest and best way to achieve bass nirvana. Set, forget, enjoy! Well done SVS!

Usability ****
Aesthetics ****
Performance *****
Value *****
Overall *****


Frequency Response Graphs

How good something sounds is the most important part of any home cinema audio or Hi-Fi setup but the fastest way to get their is to trust in a little science and measure the in-room frequency response. This involves playing frequency sweeps and recording and displaying how these sound in your seating position.

Curious as to what the AS-EQ1 is up to, I plotted several graphs with the subwoofer in two separate positions.

The ‘Waterfall’ graphs below show how my room sounds in my favourite seating position. The vertical axis depicts the frequency range from approximately 16hz up to just over 250hz, which safely covers the useful range of most subwoofers. The horizontal axis shows the time in milliseconds and the colour depicts the SPL or volume (pink being loudest and dark blue, the quietist) Because the ‘theoretical’ ideal output is a flat response with very little ‘ringing’, the perfect graph should be a consistent colour from top to bottom with very little ‘warm’ colour across the right hand side of the graph.

Caveats: I would add that these graphs were taken with domestic equipment in far from controlled conditions, they are provided for interest more than to prove scientifically one thing over another. Also bear in mind that these graphs were taken at one single fixed point in the hot-spot (my head) and Audyssey especially, aims to improve the frequency response over a much larger area so they are not telling the whole story.

No Room Correction – Subwoofer Position 1 (beside main listening position)

As you can see with no room correction this is a terrible spot with a massive room mode around 30-40hz and other smaller ones around 60hz and 90hz. The 40hz mode also rings with a lot of energy for a considerable amount of time. If you used an SPL meter and pink noise to balance your subwoofer and speakers in a room like this, the chances are you would be very disappointed, with almost no bass being delivered except around the 40hz area and even that would likely sound bloated and not very musical.

Velodyne SMS-1 Manual Room Correction – Subwoofer Position 1 (beside main listening position)

EDIT: I am not convinced this is not an eroneous reading as the ‘stretched’ looking reading for the first 50ms is not repeated in the later SMS-1 reading.

This position is very difficult to EQ with the SMS-1 due to the very large peaks which take a lot of cutting to bring anywhere near acceptable. This rather humped response was the best I could manage in the few minutes I had but you can see already that after 75ms or so the SMS-1 rapidly reduces the ringing effect of those nasty natural peaks. Trust me this may be far from perfect but it sounds much better than the natural response. What does seem to be occurring is the SMS-1 is adding its own ringing to the output before the 75ms drop off, although this is my supposition as I am far from qualified to explain exactly what is happening here.

Onkyo SR TX-876 onboard Audyssey MultEQ XT – Subwoofer Position 1 (beside main listening position)

This graph shows what onboard Audyssey can do on its own and delivers a much flatter response than my feeble efforts with the SMS-1 including a much deeper bottom end. The observant among you will notice that it does something I avoided when using the SMS-1, which is to boost the entire subwoofer signal by around 10db (to bring the bottom end back up) and then cut everything down to even things out. I make note of this because normally you would avoid this with most other EQ devices, as boosting a low signal asks the amplifier of the subwoofer to do a tremendous amount of work and can push subwoofers beyond their limits and cause damage. Ed Mullen from SVS has assured me that the AS-EQ1 can detect this and keep the signal within the safe limits of a given subwoofer, although I have read ‘claims’ of subwoofers without internal limiters being damaged by onboard MultEQ XT.

There does appear to be some ringing but it appears to tail off slightly quicker than the SMS-1 after 50ms.

SVS AS-EQ1 integrated with onboard Audyssey MultEQ XT – Subwoofer Position 1 (beside main listening position)

The AS-EQ1 plot does not look night and day better than the onboard Audyssey but it does still have a flatter response and in the majority of the frequency range, the ringing appears to be reduced earlier.

How does the AS-EQ1 perform in more favourable conditions?

Ok, let’s assume you have a more benign room, is it worth spending £650 and will it make a noticeable difference? To help answer this I tried my usual subwoofer position to the right of my right hand speaker at the front of the room. All the Room Correction methods I have tried have allowed me to produce an almost flat response here without too much effort. However anyone who has spent some time doing this will know there are many combinations of filters that will give you a response that looks pretty much the same on a 2D Frequency / SPL chart but they often sound quite different.

No EQ – Subwoofer Position 2 (Right of FR speaker)

As you can see this response still has a large peak at 40hz but doesn’t suffer from the null at 20hz making it a much simpler proposition to manually EQ.

Velodyne SMS-1 Manual Room Correction – Subwoofer Position 2 (Right of FR speaker)

Now the SMS-1 is in its element and an almost perfectly flat response is achievable with only a few minutes effort.

SVS AS-EQ1 integrated with onboard Audyssey MultEQ XT – Subwoofer Position 2 (Right of FR speaker)

The graph doesn’t look as smooth as the SMS-1 but as I stated in my caveat these can never be directly comparable because the Audyssey EQ is applied over a large area, what is apparent though is how much the ringing is reduced with the AS-EQ1 and listening bears this out. The overall difference between the two methods is not huge but it is still there and more noticeable with music which always tends to emphasis subwoofer integration issues.

Leave a Reply

Please prove you are human, thanks! *