Boston Acoustics A225C Center Channel Review

Boston Acoustics A225C Introduction

A quality center speaker is essential to any home theater. Poorly designed center speakers can make dialogue hard to heard, leaving users to adjust the volume up and down throughout a movie in order to understand what actors are saying. And a center speaker that isn't timbre matched with the front left/right speakers can make pans across the soundstage seem disjointed. As such, it's best to review a center speaker on its own merit, and also as a part of a matching speaker system. During our review of the Boston Acoustics A360 floorstanding loudspeakers, we had a chance to review the matching center speaker as well, the A225C. This is a smooth sounding center channel with very good build quality and great looks, similar to the A360's.  Although there are a few limitations, this center channel delivers a great balance of form and function at a reasonable price point.  Read on to see what we liked, and what some of the limitations are.

A225C Design

Inline with the physical attractiveness of the rest of Boston Acoustics A-Series loudspeakers, the A225C compliments with a capable center channel occupying a rather shallow 8 7/8” depth with a 16” wide by 6 5/16” high façade.  A curved magnetic speaker cover hides the entire front of the center channel giving it that familiar center channel look.  The top is covered with the black leather textured hardboard material with piano black side panels. The center channel blends in and looks like it belongs without much strife. 

The rather small cabinet is constructed out of medium density fiberboard and has adequate material thickness on all panels for a solid feeling center channel at 15.4 pounds.  The material selection and drivers are a perfect compliment to Boston Acoustics’ other A-Series speakers such as the A360 floorstanding loudspeaker.  The cabinet is ported with a tuning frequency of approximately 65Hz.

A225C Driver Configuration

The A225C is the standard center channel configuration with a tweeter between two mid-woofer drivers (aka. MTM).  In this case, the tweeter is slightly offset favoring the top of the cabinet.  The 5 ¼“ woofers are made from a ceramic and glass fiber polymer.  The drivers feature deep channel design technology providing the drivers more travel space before bottoming out. The woofers have a black dust cap that looks like a phase-plug but are glued to the cone material.  The tweeter is the same 1” Kortec soft dome tweeter found in the A-series speakers.  The center channel crossover frequency is 2.6kHz.  The A225C features good quality 5-way binding posts in a standard terminal cup.  If you plan on using a banana plug, use a small flathead screwdriver to remove the black and red plug inserts in the 5-way binding posts.

Unboxing and Setup

The A225C arrived in perfect condition boxed and enveloped in thick Styrofoam.  Just to get a feel for how this center channel performs and to break it in a little, I set it up in my office atop an ATI AT1505 amplifier and connected it to the amplifier.  The amplifier is directly connected to my do-it-yourself Buffalo IIISE DAC connected to a Macbook Pro via Amanero Technology’s 32-bit 384kHz USB to I2S adapter.  I played the center channel monaural in the background while I was working on another project for almost a full workday.  I’m not sure how everyone else responds to extraordinarily extended listening sessions; there are not many systems I can listen to this long without reaching a point of wanting to pull my hair out.  I am not relating this quality to my perception of overall sound quality. However, as is the case with the Boston Acoustics A360 floorstanding speakers the A225C excels as a speaker with very low listening fatigue. A common denominator between the two loudspeakers is the 1” Kortec soft dome tweeter so I have to assume that this quality is based on the tweeter’s properties.

For the listening tests in this review, I moved the A225C into my main listening rig.  The Boston Acoustics A360 floorstanding loudspeakers were reviewed at the same time and used as the left and right channels.  A HSU VTF-3 MKII subwoofer and in-ceiling JBL surround speakers round out the multi-channel system.  The A225C was connected to an available channel of an ATI AT6012 amplifier.  The amplifier was connected directly to the venerable Oppo BDP-105 source using unbalanced connections.  The volume control in the BDP-105 was used for all listening tests.  Prior to listening tests, each channel except the sub was level matched to within 1dB A-weighted from the listening position using pink noise and a calibrated SPL meter.  For level matching the subwoofer, pink noise was compared between the A360s and subwoofer using 63Hz octave weighting on the SPL meter with the A360s run full range.  All listening tests were run full-range on all channels for music and with a 60Hz high-pass filter for movies.

Listening Environment

Sound Quality

The listening room is approximately 24’ by 20’ and consists of hardwood floors throughout.  There is a 12’ by 10’ area rug with thick carpet padding between the loudspeakers and the listening area.  The center channel was setup on top of the entertainment center as it would be in most homes.  The listening distance was approximately 12 feet directly on axis with the center channel.

SACD: Pink Floyd – Dark Side of The Moon

Using this to review might be trite, but until I recently got my hands on the BDP-105 I was not happy with the DA conversion for multichannel in my system.  With the exception of Dark Side of The Moon, I do not have much multichannel music of reasonable quality on-hand.  Considering this album has not been spun in quite some time, I thoroughly enjoyed my time with it.  What happened in the early 70’s in Abbey Road Studios lead to an album worthy of 741 weeks in Billboards top charts and 50 million records.  40 years have eclipsed and this album is still relevant.

The only complaint I have about this album is that it is hard to just pick a track and hit play.  The transitions between songs are such an important part of the recording that I find myself rewinding 30 seconds prior to the song I want to listen to.  For the purpose of this review, I used "The Great Gig In The Sky" because it has a pretty good mix including some female vocals.  In concert with the A360s, the A225C reproduced a believable soundstage across the front that made placing the vocals and instruments simple with no real sense of where the speakers were sitting in the room.  The combination of the A-series speakers worked well together and the tonal balance for this recording seemed very warm and smooth.  There were no hints of anything offensive at reasonable playback volume levels.

Blu-ray:  Dave Matthews and Tim Reynolds – Live at Radio City

This seemed an appropriate choice for a center channel review because it’s a Dolby TrueHD unplugged style mix of music and story telling.  The track Oh opens with a monologue exhibiting Dave Matthew’s quirky personality and humor.  The music consists of a pair of guitars and Dave’s vocals dead center.  The A225C sounded a little bright on vocals with the entire recording sounding like it needed some de-essing.  Fortunately, the BDP-105 has a decent headphone out and I plugged in a pair of AKG K701s to confirm the brightness of the recording.  I’m intimately familiar with the sonic signature of the K701s and found the recording itself leaning toward the bright side but it was not as offensive on headphones.  In contrast to Dark Side of The Moon, the A225C sounded a little too bright and may benefit from room correction or manual EQ to compensate. 

Blu-ray:  The Dark Knight

This disc has one of my favorite action scenes for testing an audio system.  While transporting Harvey Dent in a police escort, the Joker diverts the escort underground in an attempt to control the situation.  The chase scene involves plenty of high dynamic range components including a RPG, the Batmobile, a helicopter and an end-over-end flipped 18-wheeler.  The A225C made it a little difficult to understand dialogue from the outset.  Even though it was pretty loud, I had to add 3dB to the center channel to overcome what seemed to be an imbalance.  This was not necessary for multichannel music.  I also found that setting dynamic range compression to high on the BDP-105 solved this issue at the cost of dynamic range.  With 3dB added to the center channel, I enjoyed the sound reproduced by the A225C in combination with the A360 floorstanding loudspeakers.

Boston Acoustics A225C Measurements

The measurements were conducted in conformance with Audioholics Loudspeaker Measurements Standard

A225C On-Axis Frequency Response

The on-axis frequency response of the A225C was conducted with the measurement microphone at 1 meter with a 2.83V excitation signal. The manufacturer rates this loudspeaker’s sensitivity as 89dB at 1 meter with a 2.8V input.  Audioholics measures sensitivity as the average SPL from 300 to 3kHz.  The A225C Audioholics rated sensitivity is below the manufacturers rating at 85.4dB. The manufacturer may have rated the A225C’s sensitivity in room.  The measurement technique used above involves removing all of the effects of a room.  The A225C response looks relatively linear but has a -3dB point of 102Hz with a steep 18dB/octave roll off.  Due to the slight bump at 200Hz, the speaker still sounds warm.

A225C Listening Window

The listening window response of the A225C is pretty uniform except for at 30 degrees off axis.  The huge nulls in the frequency response are due to the midrange-tweeter-midrange (M-T-M) configuration lobing error. This is one of the reasons horizontal center channels with a MTM configuration present a compromise when listening far off-axis. To confirm something else was not happening, I measured this phenomenon at several distances at 30 degrees and had the same finding with the effect reduced slightly as a function of distance.  This problem is inherent to all loudspeakers with a tweeter between two mid-woofers.  If the speaker is laid horizontally, there will be lobing error at frequencies that are dependent on the driver spacing.

A225C Polar Response

The polar response graph shows how a loudspeaker performs at various angles.  The polar response graph above is generated by measuring a loudspeaker at 7.5 degree intervals around a circle on the tweeter axis from 1 meter.  This polar response graph is indicative of a M-T-M configuration.  The majority of the energy is in the 0 to 15 degrees of axis listening angles.  If listening at extreme angles the response of the center channel will have significant notches.  This configuration may be advantageous because the room interactions and interference pattern with left and right channels are reduced due to the reduced acoustic energy off-axis.

A225C Impedance

The impedance of the A225C dips slightly below 6.4 Ohms IEC minimum rating for 8 ohm speakers between 6300Hz and 9200Hz.  This should not pose any problem for most amplifiers on the market.  The impedance graph above indicates the port tuning frequency is at approximately 65Hz.

A225C Harmonic Distortion

The harmonic distortion graph is generated using a stepped sinusoidal sweep excitation signal calibrated to reach 90db at 2 meters.  This is a loud signal for a small center channel and the harmonic distortion graph shows that the A225C disagrees with playing much below 50Hz.  The sweep indicates distortion peaks at 800Hz and at approximately 300Hz.  These were not offensive or even detectable during listening tests.

A225C Cumulative Spectral Decay

The cumulative spectral decay shows how sound at various frequencies dies out as a function of time.  It is important to note that the left most ridge is not valid and is a product of the measurement technique.

A225C Group Delay

The group delay graph shows the rate of change of the slope of a loudspeaker’s phase.  As a rule of thumb, values below 1.6ms in the mid to high frequencies will likely not effect perception of sound quality.  Increasing group delay in the low frequencies is not as objectionable as it is in the mid to high frequency ranges.  The group delay of the A225C is perfectly acceptable.

Conclusion

The Boston Acoustics A225C center channel is built using high quality parts and provides substantial sound from a small package.  With proper setup the A225C does a great job reproducing dialogue and multi-channel music alike.  Due to the relatively compact cabinet, the bass rolls off at approximately 100Hz but works well when coupled with a subwoofer. In my setup, speech intelligibility required a 3dB bump for clear dialog when compared to all other speakers in a system.  For music reproduction, the A225C sounds very smooth except when presented with recordings that are on the bright side.  All in all, I think the A225C is a great center channel with a small footprint.  This center channel blends well with the other Boston Acoustics A-series offerings such as the A360 floorstanding loudspeaker.

The Score Card

The scoring below is based on each piece of equipment doing the duty it is designed for. The numbers are weighed heavily with respect to the individual cost of each unit, thus giving a rating roughly equal to:

Performance × Price Factor/Value = Rating

Audioholics.com note: The ratings indicated below are based on subjective listening and objective testing of the product in question. The rating scale is based on performance/value ratio. If you notice better performing products in future reviews that have lower numbers in certain areas, be aware that the value factor is most likely the culprit. Other Audioholics reviewers may rate products solely based on performance, and each reviewer has his/her own system for ratings.

Audioholics Rating Scale

• — Excellent
• — Very Good
• — Good
• — Fair
• — Poor

Metric	Rating
Build Quality
Appearance
Treble Extension
Treble Smoothness
Midrange Accuracy
Bass Extension
Bass Accuracy
Dynamic Range
Performance
Value