Introduction

Acoustic Visions is a small business specializing in home theater consulting, installation, and calibration. Owned and operated by Kyle Richardson, Acoustic Visions offers a variety of subwoofers (both kits and pre-finished), speakers, accessories, and complete HT systems.

The MRS-10 is the first subwoofer from the Acoustic Visions “Music Rendition Series”. The MRS subwoofers are sealed mid-Q (about 0.7) units that are designed to provide musical accuracy while still retaining good output and performance for HT applications. (For those readers wanting an explanation of the Thiele-Small Parameters - of which Q is one of the units - here is a good article, in PDF form. The article also explains other things about how speaker enclosures affect the response.) See also this post in our Forum.

The MRS-10 was specifically designed for smaller size rooms, the concept being that the shallow roll-off of the sealed subwoofer will combine with room gain, thereby yielding usable extension into the mid 20 Hz region.

The Design

The MRS-10 cabinet is a down-firing cube measuring 13.75” square, handsomely finished in black piano gloss, with no visible seams or edges. A nice Acoustic Visions metal nameplate graces the front panel. The rear mounted amplifier contains a second MRS-10 metal nameplate. The overall visual impression of the MRS-10 is diminutive and classy.

I removed the driver to get a closer look inside the cabinet. The woofer is secured with wood screws, and the cabinet is stuffed with Polyfill. The MDF wall panels are ¾” thick and the enclosure is unbraced, but appears to be solidly built.

The MRS-10 is supported by four 2" wooden feet, and the face of the woofer is about 1.25” above the floor. This should work fine on most carpeted surfaces, but deep pile carpet might interfere with the long-throw driver. On my laminate floor, the wooden feet buzzed loudly, and the sub wandered (moved around the floor) at high playback volumes, prompting me to use rubber furniture feet, which worked fine. I discussed this with Kyle, and he will now include some optional stick-on rubber bumper feet to keep the MRS-10 quiet and secure on hard floor surfaces.

The MRS-10 driver is manufactured by Destijl, and features a high-density foam surround, impregnated pulp cone, a deep cast-aluminum basket, quality push-button binding posts, and a beefy looking magnet structure. A few of the Thiele-Small (T/S) parameters are: fs 27 Hz, Qts 0.43, Xmax 18 mm, Vd 1.25 liter, Pmax: 300 watts.

The driver also features Adire Audio XBL^{2 TM} technology. In essence the XBL² topology provides a linear motor strength over the entire excursion range of the woofer, which gives certain performance benefits. For more information on XBL² technology, visit http://www.adireaudio.com/Files/XBL2DetailsPaper.pdf.

Amplifier Description

The Class AB plate amplifier is rated at 250 watts continuous, and has the following features:

- Auto-On/On/Off Slide Switch
- Low Level L/R RCA Inputs (gold plated)
- High Level L/R Inputs
- High Level L/R Outputs (1st order high pass filter at 125 Hz)
- Low Pass Filter (40-160 Hz continuously variable)
- Gain/Volume
- Phase Control (0-180 degrees continuously variable)
- Thermal, Overload, and Fuse Protection
- Detachable Power Cord

To help flatten and extend the frequency response, the amp features progressive EQ with about 1 dB of boost at 60 Hz, rising to approximately 5 dB at 31 Hz. Below 31 Hz, a high pass filter is employed to help protect the woofer from over-excursion. A graph showing the EQ curve and the effect of the HPF is shown on the right.

The variable phase control offers a wider range of adjustment than a 0/180 phase switch, allowing the user to dial in the phase response of the subwoofer with that of the main speakers. Variable phase is also very useful for integrating dual subwoofers that will be located in different areas of the room.

The amp layout is logical, and the rotary controls move smoothly with a slightly heavy feel, which is nice for making fine adjustments. There is a large heat sink which worked well to keep the amp temperature under control during extended periods of high volume running. The auto-on circuit worked fine and always stayed on during movies and music, even during quiet passages.

There is no low-pass filter disable switch, so if the user operates the MRS-10 with a Dolby Digital A/V receiver or “Pre/Pro” and digital bass management, the low-pass filter control should be set to 160 Hz.

On the Bench

In order to determine the quasi-anechoic frequency response, the MRS-10 was placed outside, away from any reflective structures, and measured using ground plane techniques. Measurements were conducted with the microphone facing the woofer, at 2 meters from the depth centerline of the subwoofer enclosure, with the low pass filter set to 160 Hz, and the phase control set to 0 degrees.

The TrueRTA Quick Sweep uses a short duration (about 1.5 seconds) digitally synthesized logarithmic sine sweep. The short duration of the sweep also makes it ideal for evaluating the dynamic output capability of the subwoofer. FR sweeps were conducted at progressively increasing sound pressure levels (2 dB increments) until dynamic compression was noted. Dynamic compression is caused by exceeding the short-term linear operating limits of the subwoofer, and is indicated when the frequency response starts to compress and exhibit anomalies.

The MRS-10 frequency response measured ± 3 dB from 32 Hz - 142 Hz, and is characterized by a plateau in 50 Hz - 90 Hz region with a falling response above and below those points. The roll-off becomes steeper below 31 Hz, confirming the presence of the high pass filter.

The green curve represents the maximum uncompressed dynamic output, with 104 dB in the 70 Hz - 90 Hz bandwidth, and 97 dB at 30 Hz. The next curve (purple) stayed mostly linear, exhibiting some minor compression below 30 Hz. The next higher curve (yellow) exhibited more obvious compression.

Harmonic distortion occurs when harmonics (multiples) of the fundamental signal are produced due to non-linear behavior of the electrical, magnetic, or mechanical mechanism of the driver. A subwoofer with low THD will sound clean and distinct, especially at the deepest frequencies where distortion harmonics are easiest to detect.

Measurements were conducted with the microphone facing the woofer, at 2 meters from the depth centerline of the subwoofer enclosure, with the low-pass filter set to 160 Hz, and the phase control set to 0 degrees. To calculate the 1 meter test values, add 6 dB to the 2 meter reading. THD was limited to 10% unless otherwise noted. With the exception of 22 Hz, the test frequency spacing was 1/3 octave.

MRS-10 10% THD Test Results (Ground Plane 2 Meters):

Frequency	SPL
20 Hz	78.7 dB
22 Hz	81.3 dB
25 Hz	84.5 dB
32 Hz	92.2 dB
40 Hz	97.9 dB
50 Hz	104.0 dB
63 Hz	105.7 dB
80 Hz	108.6 dB

Audio equipment reviewer Tom Nousaine calculates bandwidth linearity by dividing the average SPL by the maximum SPL and expressing the results as a percentage. A score of 100% means the subwoofer exhibits perfect output linearity across the given bandwidth.

MRS-10 Bandwidth Linearity Calculations:

Bandwidth	Average SPL	Bandwidth Linearity
20 Hz - 80 Hz	94.1 dB	87%
22 Hz - 80 Hz	96.3 dB	89%
25 Hz - 80 Hz	98.8 dB	91%

At 40 Hz and 98 dB, THD was 10%. The spectrum is shown below.

To simulate a typical user set-up, the MRS-10 was placed in the front left corner of my 2,000 ft³ home theater room. For bass management, all speakers were set to small with a crossover of 80 Hz. The in-room FR sweeps were processed through the Pre/Pro with only the main speakers and the MRS-10 operating. Setting the phase to 0 degrees provided the best results in my room. The MRS-10 gain was adjusted to obtain a good transition from the main speakers, and to provide an optimally flat FR across the majority of the operating bandwidth.

The in-room FR was measured at three popular listening positions, all about 12 feet from the MRS-10. The three curves were then combined to create an average response curve. The three curve average measured a very good ± 5 dB from 22 Hz - 83 Hz, graph shown below. As advertised, the MRS-10 exhibits useable extension into the mid 20 Hz region by taking advantage of room gain in a small to mid-size room. In a much larger room, the response would roll-off sooner, more like the quasi-anechoic ground plane curve.

To provide a real world indication of how loud the MRS-10 can play in my mid-size HT room, I measured some sound pressure peaks from a few action-oriented DVDs. I used a B&K Model 2205 SPL meter (set to C-weighted Fast) at the listening position. The sound pressures listed are straight meter readings, with no correction factor applied.

As a guide for setting the maximum playback level, I increased the master volume until minor distortion and compression artifacts were noted on the deepest and most challenging scenes, and then backed off on the master volume 2 dB to ensure a dynamic and low distortion presentation. My HT system is calibrated to Dolby Reference Level at master volume 0.0 with the Avia Guide to Home Theater DVD. Master volume settings are listed for reference purposes only.

Listening

With Movies

a) Lord Of The Rings – Fellowship Of The Ring (DTS-ES 6.1), Master Volume -13

I was quite surprised by how loud the MRS-10 played on certain mid-bass passages. With source material above 30 Hz region, it displayed great dynamics. While the MRS-10 remained well behaved on the ring drop and the cave troll scenes, it definitely rounded off the bottom end, not providing much infrasonic room decay.

Scene	Time Stamp	Peak SPL
Sauron Ring Drop	0:03:58	106 dB
Sauron Death Sweep	0:04:14	110 dB
Sauron Helmet Falls	0:04:19	109 dB
Wraiths On Horseback	0:32:43	103 dB
Mount Doom Thunder	0:32:53	106 dB
Cave Troll Falls Dead	0:33:28	107 dB

b) The Haunting (DTS-ES 6.1), Master Volume –14

The MRS-10 really pounded the room on the door knocks, which are primarily centered in the 40 Hz - 50 Hz region. In comparison, “the cold” scene (which is centered at 22 Hz) was almost inaudible, except for some doubling in the 40 Hz region.

Scene	Time Stamp	Peak SPL
Door Knocks	0:38:06	106-109 dB
“The Cold”	0:39:15	91 dB

c) Star Wars Episode II –Attack Of The Clones (DD-EX 5.1) Master Volume –13

The MRS-10 didn't falter during the demanding THX Calvalcade “exploding globe” scene, but did omit some infrasonics. The Coruscant ship passing and ship explosion scenes were played well, with good power and dynamics. In comparison, the MRS-10 lacked some authority on the extremely deep speeder crash.

Scene	Time Stamp	Peak SPL
THX Cavalcade	Globe Trailer	104 dB
Ship Passing	0:02:02	106 dB
Ship Explosion	0:03:23	108 dB
Speeder Crash	0:20:53	101 dB

With Music

On music, I found the MRS-10 to be sensitive to room placement. Corner loaded, it tended to add a bit of weight and body to certain music notes in the 35 Hz - 45 Hz region. Moving the MRS-10 away from the corner about 18” eliminated this effect, and provided a more natural presentation to the music. MRS-10 owners are encouraged to experiment with placement for the best results on music.

a) Giant Steps - John Coltrane, Atlantic Recording Corporation, 1960

Syeeda's Song Flute features an acoustic bass solo by Paul Chambers. The MRS-10 displayed good time coherence and kept pace perfectly with the main speakers.

b) Everything Must Go - Steely Dan, Reprise Records High Resolution DVD-A, 2003

“Godwhacker” opens with a well recorded bass kick drum, and the MRS-10 stayed tight and focused, with no slop or overhang.

c) Underworld soundtrack - Lakeshore Records, 2003

Renholder's Now I Know contains very strong synthesized bass in the 23 Hz region. The MRS-10 struggled with this track at higher volumes, rounding off the deepest notes and sounding a bit wooden. It performed much better on A Perfect Circle's "Judith" (which contains bass in the 30 Hz region), showing good authority and dynamics.

d) A Knight's Tale soundtrack – Sony Music Entertainment, 2001

Queen's "We Will Rock You" features that famous pounding bass line. The MRS-10 separated the double hits well, with good definition.

The MRS-10 showed realistic timbre and smooth blending with the mains on the funky electric bass guitar lines in War's "Low Rider".

I liked the way the MRS-10 easily separated the repeating kick drum and bass guitar rhythm lines in Eric Clapton's "Further On Up The Road".

"The Boys Are Back In Town" (Thin Lizzy) is just one of those classic rock songs that encourages you to crank it up. The MRS-10 rocked out well, with good dynamics and realistic tympanics on the kick drum and tom strikes at high volumes.

e) Monk's Dream The Thelonious Monk Quartet – Columbia Records/CBS, 1962 (Direct Digital Remaster)

Bassist John Ore anchors the title cut from this famous jazz recording. The MRS-10 displayed good cohesiveness and nuance on the acoustic bass, drawing the listener into the recording. Ditto for "Bright Mississippi", where the MRS-10 nicely preserved the delicate pitch and timbre of the soaring acoustic bass lines.

Conclusions

The Acoustic Visions MRS-10 definitely has a high Spousal Acceptance Factor. It is small enough to fit inconspicuously almost anywhere in a room, and yet it is handsome and elegant enough to match nearly any décor.

Being a sealed subwoofer, the MRS-10 has a shallow roll-off, and in smaller rooms will take advantage of room gain and exhibit useable extension into the mid 20 Hz region. I would not recommend this subwoofer for larger living spaces, as it would tend to roll-off at the 30 Hz - 35 Hz region in a big room.

After experimentation with placement, I found the MRS-10 very natural sounding on popular music, with a pleasant and non-fatiguing character. It blends well with the main speakers, has good detail, coherence, and pitch. The MRS-10 is a good start to the “Music Rendition Series” from Acoustic Visions.

In my mid-size room, the MRS-10 performed well on many DVDs, easily filling the room with punchy and dynamic bass that belied its small size. While the MRS-10 did capture the weight and body of most popular bass passages, it can't do justice to source material below 25 Hz, and also omitted the infrasonic decay on certain scenes. In fairness, playing extremely deep wasn't a design goal for the MRS-10, and Acoustic Visions offers other larger subwoofers that will easily play below 25 Hz with authority.

The MRS-10 was designed to be a versatile performer on most popular music and movies, while retaining small dimensions. I think Acoustic Visions has achieved that goal with the MRS-10. Consumers who place a premium on aesthetics and size while still demanding good overall performance will find that the MRS-10 definitely fits the bill.


 - Ed Mullen -