Emotiva Airmotiv S15 Subwoofer Mini-Review

The Emotiva Airmotiv S15 Subwoofer is made by the internet-direct company, Emotiva, of Franklin, TN. They are known for their audiophile-quality and high-value products when compared to most other brands. The Emotiva Airmotiv S15 subwoofer definitely qualifies. Unfortunately, as this review is being written in January of 2020, the S15 is being discontinued by Emotiva, and their remaining stock is on clearance sale. When those are gone, new models will be offered instead

The Emotiva Airmotiv S15 sub seduced me with its clearance pricing. Most high-quality 15” subwoofers cost approximately twice the clearance price of the S15, so one can buy TWO S15s for the price of a single equivalent subwoofer from most any other brand. I’ve used Emotiva products for years now, and have been happy with their quality and value.

Some compromises are inherent in the design of subwoofers, including the Emotiva Airmotiv S15. You don’t get large cones in small boxes, nor do you get deep bass response without high power and/or a large cabinet. I won’t belabor the issues of subwoofer design, but Emotiva seems to have juggled their priorities pretty well with the Airmotiv S15 subwoofer.

Being picky (as I am), let’s get my complaints out of the way:

The sub rolls off at both ends of its bandpass. The low-end roll-off occurs at about 22Hz so I don’t much care about that one. But the high-end roll-off begins about 60Hz from the highest peak of the sub’s response (about 48Hz) and is down by about 5dB at 100Hz.

This is almost an 8dB per octave roll-off in the crossover region. I could boost the output to make the sub linear to 100Hz, but that is an active part of the spectrum, and the power output demands on the internal subwoofer amplifier would be great. The best solution I’ve found is to cut the peak off the frequency response with a broad and wide cut. After measurement, I used a cut of -3dB at a center frequency of 53Hz with a Q of 0.9.

But were you to run this sub with no DSP equalization, you’d likely have an audible dip in the frequency response at the most common THX crossover frequency of 80Hz. It would have been better if this sub had a flatter and wider frequency response.

1. The passive radiator on the sub causes a huge phase shift (as do all passive radiators, by design). Fortunately, it occurs primarily at the -3dB frequency of about 19Hz so who cares? Unfortunately, I think that phase shift may be muddying the bass far further up the frequency spectrum. In my room, against the speaker wall, the subs sound slow. I may be able to tighten them up by getting them away from the wall (I’ve already got them off the floor with 18″ tall stands). But I think it’s fair to say that I haven’t gotten the best of these subs yet. Is it the fault of the subs themselves, or have I just not yet got them positioned right? Hard to say, but these subs don’t quite work in the same locations that multiple other subs have in my room.



2. The subwoofer’s plate amplifier has a lowest-available crossover frequency of 60Hz. This means that with full-range speakers (like my Emotiva T2 towers, that go down to below 40Hz) there’s a huge hump in the frequency response curve where the main speakers and the sub overlap.

   Now if you’re using the sub(s) with an electronic crossover (such as with an AVR or an external crossover), this is academic. But if you want to run your satellite speakers without bass management, and you’re using anything but small monitor speakers, be prepared to do some in-room measurement and equalization.



3. The subs thump. I’m not talking about when playing, but rather when just sitting there on standby. Not only do they thump on turn-on and turn-off, but for the first 20 minutes of use, the capacitors in the plate amps are apparently still forming, and both of my two subs thump at random. Once warmed up, the thumping seems to stop. I’m hoping that I can just leave them on and avoid this



4. This is minor (to most people) but the subs are the ubiquitous ugly black color. I don’t like black components, and you just can’t get away from them these days. As you can see, my whole system is just monochrome, dreary, ugly black. Bleah!

So, I think it’s fair to say that if you want the best performance from Emotiva’s Airmotiv S15 subwoofers, you’re going to have to work at it. Of course, this is true of ALL subwoofers, but it’s more so than usual with the S15s.

I ran the usual suspects for evaluation of the Emotiva Airmotiv S15 subwoofer:

• Bach’s Toccata and Fugue in D Minor by Don Dorsey
• “Flight of the Cosmic Hippo” by Bela Fleck and the Flecktones
• “Celloopa” by The Piano Guys
• Liszt’s “Hungarian Rhapsody” by The Atlantic Brass Quintet
• “Sing, Sing, Sing” by the BBC Orchestra
• “Way Down Deep” by Jennifer Warnes

And many more…

And?

Well, it depends on the implementation. I first hooked up the two subs as a mono pair using a Yamaha Aventage RX-A670 AV Receiver. After running the YPAO room correction, the subs sounded very good, but with a slight bass muddiness.

I then ran the two subs with no crossover at all on the satellites, and with the plate amps of the subs rolled off at their minimum 60Hz. I tried this with both my Klipsch RP600M bookshelf speakers and with my Emotiva T2 tower speakers. In both cases, there was an audible peak where the satellites and the subs overlapped and the slight muddiness in the bass persisted. I could have reduced the peak with some DSP, but chose to go to an external crossover instead:

I then ran the two subs as a stereo pair using an NHT X1 electronic crossover. Since the crossover has some undefeatable frequency equalization intended for NHT subwoofers only, I measured with my Umik microphone and then used DSP to neutralize the crossover. In this mode, things perked up, but even now, the bass remains just slightly yet audibly muddy.

At their clearance price of $899, the EMOTIVA AIRMOTIV S15 SUBWOOFERS are a great deal. But don’t overlook their 12 or 10-inch models instead.

Power? Yes!

Price? Yes!

Construction quality? Yes!

Would I buy them again? Maybe – but I’m probably a LOT pickier than you. For home theater subs, these are world-class. They’ll rock your world on dinosaur steps and various explosions. For chamber music, I’m still working with them…