ACI Maestro Subwoofer Review by Craig Chase

October 2004

The audiophile world has changed a lot in the past 25 years. In 1979, a high-end system consisted of a pre-amp, power amp, a pair of speakers, a turntable, perhaps a reel to reel tape deck and/or a cassette deck. My early involvement in audio centered on selling equipment part time to pay for college tuition. If someone bought a really nice system, we would install it free. This usually meant spending a couple of hours doing the actual installation, followed by several more hours of serious listening. One of my favorite jobs was selling a gentleman a pair of Dahlquist DQ-10’s. He was the most knowledgeable audiophile I had yet met.

I brought the DQ-10’s to his house, and watched as he did the actual installation. He had the most amazing system, with not only the usual pre-amp, power amp set up, but a crossover set to 50 Hz with RCA plugs leading to a Marantz 510 amp, which was plugged into two large boxes. These large boxes each contained a Hartley 24 inch driver. This was my first experience with a subwoofer for home use, and it was something I never forgot. This nice gentleman then fired up his reference LP (remember those?) – Pink Floyd’s "Dark Side of the Moon". I had never experienced bass like that in a house, and became hooked on the idea that the subwoofer could literally change the face of audio. The idea of removing the last two octaves from the main speakers and having these huge subwoofers handle that deep bass made a good system into a great one.

At the time, the subwoofer was a fringe item in the audio world, and very few people even knew what one was. Today, you can find subwoofers not only in every Home Theater store, (we no longer call them stereo stores) you can even buy one at Sears and Walmart. The subwoofer is no longer that rare item only an audiophile would own. It is a necessary component in every Home Theater.

Subwoofers come in many shapes, sizes, and prices. You can find them for $30 to $30,000, though the typical price range is $200 to $5000. Personally, I have listened and tested over 50 subwoofers in the past 20 + years, including models from SVS, Velodyne, Hsu and several others. My most recent review is from a company that was actually around in 1979 and has seen the shift from two channel audio to full home theater, and has adapted accordingly. This company is ACI, and the subwoofer is the Maestro. The Maestro is a fairly large subwoofer and stands at the top of ACI’s subwoofer line. It sells for $2100 to $2400 (depending on the finish) directly from ACI, and is intended to compete in the high end subwoofer arena. Mike Dzurko, ACI’s founder and CEO, is quite confident that the Maestro is competitive with any subwoofer under $5000. We will put that to the test. 

The Maestro Arrives:

We are on the "drop it and go" program with Fed-Ex, UPS, Yellow Freight, etc. The Maestro was in our garage on a Monday night when I arrived at home. The box is pretty big, but after unpacking subwoofers like the SVS B4+, it was not too intimidating.

The packing was excellent, and unpacking was easy. All that was required was opening the outside box, sliding the inside box out, and repeating the process. The Maestro was sitting there in its Honey Oak dressed glory, ready to take on our theater room. (Pictured to the right in Mahogany). It weighs about 105 pounds, so carrying it in was a snap, as was placing it in the system. The Maestro itself is one beautiful subwoofer. The Oak finish matched our oak trimmed décor perfectly, and the box is the right size to make an attractive end table. It definitely passes the WAF rating test.

The Amplifier, which is a separate unit, allows for a direct input from your receiver or pre-amp’s subwoofer output, which will deliver a signal after the highs are filtered out. It will also accept a full range signal and has dual 12 dB per octave low pass filters. Normally, one would set both low pass filters to the identical frequency, giving a 24 dB per octave filter. They are two separate controls, and can be run independently should the need arise.

Another bonus feature ACI includes is an adaptor which accepts a high level signal and converts it to a low level signal for those who have a two channel system and want to augment the bass response of existing loudspeakers.

For connectivity, the Maestro has as many features as I have encountered with a subwoofer. The separate amp also allows for more placement flexibility. Anyone who has tried to adjust controls on the back of a 100 plus pound subwoofer will appreciate having this amp with easy to use controls on the front.

As the owner’s manual suggests, there are several ways to calibrate the Maestro. The first is literally to hook it up, connect a cable from your receiver or processor, and set the levels by ear. There are quite a few audiophiles who do not understand how to use extra equipment to set up a subwoofer, so I tried the "ears only" method first.

I was quite surprised at how easy the Maestro was to set up in this manner. I put on the Steely Dan DVD-Audio Disc "Two Against Nature" and started playing with the gain control. It took about 5 minutes, and I was hearing deep, tight, tuneful bass. I will get into more specifics about performance of the Maestro later, but it passed this test easily. One does not have to be a seasoned audiophile to easily integrate this subwoofer into a high-end system in a few minutes with the use of a good deep bass disc and careful turning of a single knob.

Before we did any serious listening, though, I placed the Maestro into a corner, and proceeded to completely calibrate it using my Earthworks M30 microphone and TrueRTA software. After this calibration we were getting strong bass into the 14 Hz range. This is where the real review begins, with this question: Is the Maestro a boutique subwoofer with decent bass, or is it a contender in the $4000 to $5000 subwoofer class?

Associated Equipment and Software:

System 1 (7.1 home theater): Denon 3805 seven channel receiver, Onix Rocket 750 Signature as front speakers, RSC-200 center channel, and 250 Mark II as side and rear speakers. The Pioneer DV-47iA served as a universal player.

System 2 (Two channel): McIntosh MA-6900 Integrated Amp, Onix Reference 3 speakers and a modified Denon 2900 Universal Player.

Software (music and movie discs):

Music:

1. Steely Dan - "Two against Nature" DVD-A
2. Tony Bennett - "Unplugged" SACD
3. Sarah Mclachlan - "Solace"
4. AC-DC – "Back in Black"
5. 1954 Mercury Release of Tchaichovsky’s 1812 Overture
6. Stanley Clarke – "Greatest Hits"
7. FourPlay – "Between the Sheets"

Movies on DVD:

1. Terminator 3
2. Open Range
3. The Empire Strikes Back (part of the Trilogy release)
4. Armageddon
5. The Day After Tomorrow
6. Lord of the Rings : ROTK
7. Star Wars: Attack of the Clones

The first listening tests were strictly in two channel music using system #2. I am not normally surprised to hear really good bass from a subwoofer. As mentioned above, we have had a lot of excellent designs through our listening rooms. The Maestro, however, was immediately a step above anything we have ever had. The first disc was Steely Dan, and the Maestro did more than just deliver good bass. It grabbed everything coming from the disc, and delivered performance I did not think was attainable for under $5,000, let alone $2100. When the DEEP kick drum starts in "Jamie Runaway", you feel it in your chest. Everything was not only deep, but the Maestro showed a transient response that matched, for example, the excellent response of the Rocket UFW-10.

On AC-DC, the whole house was rocking, and Stanley Clarke was powerful when called on, and agile in the upper registers. The Sarah McLachlan disc has a track (Back Door Man) with some sub-20 Hz synthesized bass that has sent many subwoofers into complete failure. The Maestro literally shook our concrete floored room, and you could feel waves emanating from the system. This is something that should be experienced at least once by every bass lover.

The real star, though, was the 1812 Overture’s cannons. The two channel system is in our basement, with room dimensions of 43x14 feet. The Maestro was corner loaded, and all walls and floor behind and under it are concrete. We were getting 110 dB blasts that literally could be felt like a punch in the chest. I have tried the same test in this room with a Velodyne FSR-18, Paradigm Servo 15, SVS PB2-+, and a larger VMPS subwoofer. All of them were quite good, but none even approached the visceral HIT that the Maestro delivered.

For music, the Maestro did everything it was asked to do, and did it better than any subwoofer we have EVER had in our system.

After a week of using the Maestro in the two channel system, it was time to carry it upstairs and place it in our seven channel theater room. This room is 25 feet long, 24 feet wide, and has 9.5 foot high ceilings. Our current subwoofer is the excellent SVS B4+. I disconnected the SVS and placed the Maestro in the same location. Compared to the huge SVS, the Maestro actually looked small. My wife was in disagreement with me, she thought the Maestro looked normal.

First up for movies was Open Range. The two key areas for bass in Open Range are the thunder storms and the gunfight scenes. The gunfights were quite similar to the effect we experienced in the 1812 Overture. Each shot could be felt as a hit in the chest. As good as the SVS B4+ was, the Maestro took this ability one step further. The thunderstorms were done so well that my wife went to close the windows in the other room to prevent rain from coming into the house, and it was a clear, starlit evening. I am still in trouble for laughing at her reaction.

Every movie we watched made even more clear just HOW good this subwoofer is. ROTK was nothing short of spectacular, with wave after wave of deep, infrasonic bass, yet, at no time did the Maestro ever become "boomy". The opening scenes in Armageddon are some of the finest percussive effects done in a movie. The meteor shower in New York is centered around very powerful, 30 Hz bass, and each individual crash of a meteor is clearly heard and felt.

Star Wars, Episode 2: Attack of the Clones was the sleeper of the bunch. I put it on just to do the obligatory quick listen, and was actually drawn into some of the finest deep bass I have ever heard. If you get the chance, check out AOTC with the Maestro handling bass duties. The scene where Ani, Senator Amadala, and Obi-Wan are chained in the arena is spectacular. When the Acklay (think giant crab-spider) strikes, hits with a 24 Hz signal that, for example, were there with the B4+, were VISCERAL with the Maestro.

As the Maestro review continued, it became apparent that it was going to be a keeper in my system. As our room is quite large, I decided to add a second Maestro into the theater room. I put this Maestro along a wall, and re-calibrated the system with the newly released "The Day After Tomorrow" Disc. I thought one subwoofer was great, but TWO Maestros was a revelation. This disc was rumored to be an excellent bass feast, and it was that and more. When the huge ocean swell is coming into New York City, the bass is so deep and powerful, one actually flinched away from the screen. The second unit is certainly not a *need* item, but it sure is something to want.

We ran several sets of measurements with the Maestro, and have included five graphs. The first graph is a non-equalized, in room, frequency response sweep, Three graphs are for the maximum output at under 10 % THD for 16 Hz, 20 Hz, and 25 Hz. The last graph is and a listening position maximum SPL graph of Star Wars: Phantom Menace.  An outdoor Ground Plane Frequency Response: (not shown) was +/- 3 dB from 18 to 100 Hz. This shows excellent coordination of the subwoofer driver, amp, and equalization. The Maestro is one of those rare components that exceeds the manufacturer’s specifications.

Indoor Frequency Response: +/- 5 dB from 13 to 100 Hz. This shows that careful placement combined with room gain can enhance the overall response of a subwoofer.

 Maximum output at 16 Hz: 100.4 dB < 10% THD

Maximum output at 20 Hz: 107.8 dB < 10% THD

Maximum output at 25 Hz: 111 dB < 10% THD

These measurements were taken outdoors (ground plane) at one meter. Recently, Ultimate A/V completed a test on 12 subwoofers, ranging from $2500 to $10,000. Based on strictly objective numbers, the Maestro would finish mid-pack while being the least expensive in the group, by far.

The graph of "Phantom Menace" was just for fun. It clearly shows the movie has a very large amount of bass in the 20 to 30 Hz range, as well as some fairly strong infrasonic bass. This is very impressive performance, and was a great ride, too

The Maestro has indeed proven that it belongs in an elite class of subwoofer. Its measured performance is commensurate with other internet direct subwoofers in its price range, and far superior to those sold in Brick and Mortar stores.

It was in subjective performance that the Maestro really showed it has the "right stuff". The highest praise I can bestow on any product is when the performance of that product makes me want to buy more music and movies. The Maestro does that in spades, and has also caused me to sell my previous favorite subwoofer. This Maestro pair is staying in our theater. Great job, ACI !

* Reviewer's Note 11/10/04:  For the entirety of this review, I used only one Maestro. All measurements were also taken with one Maestro. I decided to order a second Maestro after the review because I wanted one, not because I needed another Maestro to give sufficient bass output" ...

CC