A7S-450 System Setup

Setup began with opening the box and carefully rolling it over to lift it off the subwoofer. With a sub this size, don’t get some silly idea to try and lift it out of the box, the geometric reality is that the typical size of the human body does not provide the leverage to bend over a box this large and then lift a beast like this out. Oversized, chest beating contrarians may balk at my statements, but don’t complain to me of injured backs, broken bones, damaged subwoofers, or collapsed floors if my advice is not heeded.

I then rolled the sub upright onto furniture sliders, maneuvered it into place, and left it on the sliders. Carpet spikes be damned, this thing isn’t going to move significantly from the force generated by the reaction of mere acoustic emissions.

From this point on, everything is mostly subwoofer standard. Select an acoustically acceptable location: crawl for bass, take measurements, or play-it-by-ear, whatever suits your fancy, and then dial in the appropriate settings. With the A7S-450 used for an LFE channel, the correct signal input must be wired into the system for the crossover bypass and the crossover frequency is then set using preamp/receiver bass management functions. If the subwoofer is being used without bass management, dial in an appropriate frequency based on the roll off point for the accompanying main channels. Next, using a full range source signal, adjust the phase to the setting that produces the best integration with the main speakers which usually corresponds to the setting that yields the higher and steadier SPL output via a frequency sweep. Finally, manually adjust the volume level to balance the overall system frequency response and then use the processor functions for speaker setup to tweak the final output setting, either by ear or with an SPL meter or any other available measurement device.

The only difficulty that I found using the A7S-450 is that it kicked a 15 ampere circuit every time I turned it on. Untamed inrush current draw sucked all 15 amps out of the wall consistently without fail. The process of powering up the subwoofer typically involved at least one trip into the basement to reset the breaker as the capacitor took on power. The circuit kicked even when completely unloaded with every other electrical device on the circuit turned off, both from a fresh power up as well as when coming out of standby mode. As such, I am not sure that even a 20 amp circuit will slake the A7S-450 of its initial thirst.

For me, the current situation is temporary; my system will ultimately end up on a 20 amp circuit, but until then and for anyone who does not have a 20 amp circuit available, it will be a problem, especially for older fuse protected circuits. Considering I normally run the more powerful Fathoms from this circuit without issue, I consider the inrush current problem to be an oversight in the design of the amplifier. JL Audio makes a point of discussing current draw for home audio applications and specifically outlines their efforts to mitigate the problem as part of the amplifier design. It would appear that eD has some homework to do to correct this problem.

Equipment Used

I evaluated the A7S-450 subwoofer using my A/V setup with HD-DVD, DVD, and CD content reproduced using a Toshiba HD-A35 and a Sony PS3 for Blu-ray content. Audio processing and power amplification was provided for using a Rotel RSX-1067 driving a 7 channel Infinity Beta speaker array with bass management set at an 80 Hz crossover point. All source material used for the review was reproduced in its native format, multi-channel or stereo, with the Rotel set to two channel mode for stereo material and the Beta 40 towers engaged to reproduce the mid and upper frequencies.

Normally I prefer being provided two subwoofers for review as it is easier to minimize certain room acoustics issues directly, but for this review, I was sent a single unit. The advantage of multiple subwoofers is that they can be used to help limit modal coupling of bass frequencies to the room through judicious placement of the subs relative to the room, each other, and the listening position. I typically run dual subwoofers and shifting to a single sub presents an extra difficulty to sort out what is really coming from the sub and not from the room acoustics, which is best avoided if possible.

Editorial Note on Multiple Subwoofers

Multiple subwoofers are a good choice to smooth frequency response by minimizing room modal behavior through cancellation. Strategic placement of the subs at opposing nodal points for frequencies that trouble the listening area can be used to nullify the worst dips and peaks from the room modes. This is a distinct advantage over equalization, which can only trim peaks but not fill dips.

My own experience with running multiple subs has been a stark improvement with smoother frequency response, improved bass detail, and increased depth at the bottom end beyond what a single well placed sub can muster.

I am including several links where this topic is discussed in greater detail and also an Excel based spread sheet that calculates modes for a rectangular room:

Audioholics: Room Modes and Dealing with Them

Harman multiple subs

Getting the bass right

Harman Room Mode Calculator

As usual, I put my test specimen through a wide range of movie and musical content with some of the highlights detailed below. Overall, I found the A7S-450 to be a highly capable subwoofer, able to generate prodigious output. Despite its rather large size, it was a surprisingly subtle subwoofer. The brute didn’t stumble all over the musical details, bull in a china shop fashion, when reproducing more sublime bass content and it also kept enough composure to render musical subtleties even when more demanding LFE was also present. The subtle playback capabilities allowed the fairly large A7S-450 to disappear, sonically, into my system very effectively; it played deeply, loudly, and transparently, blending into my system extremely well.

Comparison of Subwoofers

I’ve recently had my hands on a number of subs in this price category, between $800-$900, that pushed a kilowatt or more output. Both the Sunfire HRS-12 and the Chrysalis Acoustics Photon-8 can be considered direct competitors at the price and comparable power specifications.

The A7S-450 bested both in terms of absolute performance as a subwoofer providing the greatest acoustic output capabilities and the least colored sonic signature. The tighter acoustic performance helped the A7S-450 to be the most sonically invisible of this group of subs and presenting the best sonic integration into my system. This is not to say that the other subwoofers are inferior in any way. The performance of these subs simply represents different engineering tradeoffs.

The A7S-450 is the least subtle design, sheer size gives it the upper hand against the HRS-12, and the extra 300 watts don’t hurt either, but it’s a close race and the considerably smaller sub still puts up some stiff competition for the much larger A7S. Appearance considerations will give the Sunfire sub the clear upper hand, as it will at least look decent with more upscale décor, having a much nicer pseudo-piano gloss finish.

The Photon-8 on the other hand represents the complete opposite design philosophy, and while the A7S can handily outdo the little guy in an absolute sense, the Photon-8 is an extremely impressive subwoofer after taking into account its very diminutive size. Some people may not want a sub as big as the A7S or simply do not have the room. The Phototn-8 is easily tucked away and it will still impress friends with a very convincing imitation of being a much larger sub than it is.

As for higher end competition, the A7S will not best subs of the caliber of the Fathoms, either in terms of output or in terms of musical accuracy. To my surprise, considering her relative apathy to my audio preoccupations, even my wife could tell the difference and preferred the Fathoms. But the difference should be tempered by considering the effect of diminishing returns for subs like the Fathoms: the $860 spent on the A7S will get one a disproportionate fraction of the Fathoms performance for the price.

The moral of the story is that every design has its pros and cons and there is a variety of competently designed subs available to satisfy different needs, preferences, and priorities. Everyone should temper the selection process with actual product auditions before making a purchase.

Overall, the A7S-450 is a good subwoofer, and excellent for the asking price, if the size is not an issue.