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Boston Acoustics A 25 Speaker Review

amirm

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#1
This is a review and detailed measurements of the Boston Acoustics A 25 bookshelf speaker. I purchased these a while back at a discount. Seems that they were originally released back in 2011 for US $300 a pair. At the time I purchased them the price had dropped to US $180 a pair. There were taxes and shipping costs added to the price. After discount, my net cost was $155.

The fit and finish of the speaker belies its very low price:

Boston Acoustics A 25 Review Bookshelf speaker.jpg


As you see there is some kind of faux leather surrounding the front baffle. Same is used underneath which is useful in keeping the speaker planted. Sides are gloss which gives the speaker fair bit of class. The cabinet feels dense, solid and heavy for its size.

Back panel shows nice provisions for hanging the unit and same leatherette finish:

Boston Acoustics A 25 Review Bookshelf speaker Binding posts.jpg


Hard to imagine this speaker is being sold for so little. Externally anyways....

Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise. Both of these factors enable testing in ordinary rooms yet results that can be more accurate than an anechoic chamber. In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room.

I performed over 1000 measurement which resulted in error rate of more or less 1%.

Temperature was 58 degrees F. Measurement location is at sea level so you compute the pressure.

Measurements are compliant with latest speaker research into what can predict the speaker preference and is standardized in CEA/CTA-2034 ANSI specifications. Likewise listening tests are performed per research that shows mono listening is much more revealing of differences between speakers than stereo or multichannel.

Reference axis was the tweeter center.

Boston A 25 Measurements
Acoustic measurements can be grouped in a way that can be perceptually analyzed to determine how good a speaker is and how it can be used in a room. This so called spinorama shows us just about everything we need to know about the speaker with respect to tonality and some flaws:

Boston Acoustics A 25 Review Bookshelf speaker CEA-2034 Spinorama frequency response measureme...png


I must say at first I thought this was rather chewed up. But if we ignore the upper frequencies above 10 kHz, the rest is not too bad. We have a bit of peaking around 900 Hz. And a dip around 3 kHz.

Directivity is actually decent which means we can a) EQ the response and b) response will not be too room dependent.

The issue at 900 Hz becomes obvious when we look at the nearfield measurements of each sound radiating element:

Boston Acoustics A 25 measurement driver port woofer tweeter nearfield frequency response.png


The port becomes a bit crazy above its intended response and generates a couple of peaks. In addition, we see the tweeter having rather non-flat response.

The tweeter seems to have a steeper roll off than the woofer causing the dip in the crossover region.

Back to our spinorama, here is our early window reflections:

Boston Acoustics A 25 Measurements speaker CEA-2034 Spinorama frequency response.png


Like most speakers, floor reflections have a large dip and is best avoided with a thick carpet (which my listening room has).

Predicted in-room response is:

Boston Acoustics A 25 Measurements speaker CEA-2034 Spinorama Predicted In-room frequency resp...png


Impedance curve shows the resonances we have discussed:

Boston Acoustics A 25 measurement impedance and phase.png


Horizontal beam width is actually quite decent:

Boston Acoustics A 25 measurement Horizontal Beamwidth.png


As is contour of the same:
Boston Acoustics A 25 measurement Horizontal contour.png


They have made an attempt to narrow the gap between the woofer and tweeter and it shows in better vertical response:
Boston Acoustics A 25 measurement Vertical contour.png


Edit: forgot the distortion graphs:
Boston Acoustics A 25 measurement relative thd distortion.png


Boston Acoustics A 25 measurement thd distortion.png



Boston A25 Listening Tests
I placed the A25 in my usual far-field setting. First impression was positive. Certainly better than casual glance of the spin data. Some touch up EQ nicely lifted the response:
Boston Acoustics A 25 eq filter.png


I tried to lift the dip but it subjectively made the speaker sound bright on some tracks so I took it off. As I noted earlier, I have a thick carpet so the predicted in-room response for me is better than what I showed.

The first filter is to get rid of distortion. It took away a bit of bass so you may want to play with it. The dip to get rid of the resonance was effective of making the sound lighter and vocals to stand out a bit more which I liked. The final shelving was to get rid of occasional brightness depending on track. I hate the fact that we have no production standards so sometimes seems impossible to actually tailor the overall "target curve."

Once there, the sound was quite nice. I listened for good 30 minutes and track after track sounded beautiful. Here is an example from Gait Kelin Kromhof:

Gait Kelin Kromhof.jpg


Sorry, there is no youtube track for it. It is superb music that is very well recorded and it sounded great on the A25.

Dynamics were superb here and I could detect no sign of distortion at very high volumes. That said, if you listen to the port in the back, it sure sounded distorted and badly so. My back wall is from far from the speaker so I could not hear it from the front. If your situation is different, then the experience may not be as rewarding as it was for me.

Conclusions
The fit and finish of the Boston Acoustics A25 matches a speaker north of $800 a pair. It is hard to imagine how they pulled it off at such a low price. Objectively, the response is not ideal but somehow the mistakes are not that big with respect to audibility and easily corrected. While the speaker seems discontinued, searching for good prices as I did on clearance is an excellent idea. You will certainly get a speaker with far more power capability and better tonality than most budget speakers.

I am going to put the Boston A 25 on my recommended list.

------------
As always, questions, comments, recommendations, etc. are welcome.

Could no longer walk in our garage. So took out of main barbeque grill and smoker and put them on the deck. Now I have more space and ability to cook in winter just as well! Why do I say this? Because it sure would be good to have some money sent my way for meet to smoke! Have to eat good in winter or depression can set in with the gloomy days we have!

Appreciate any donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

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Last edited:

Beave

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#2
Did you do any distortion measurements?

Results look pretty decent, especially for the price. It does look like they cheaped out on the woofer crossover, but otherwise the measurements are fairly solid.
 
OP
amirm

amirm

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Thread Starter #4

Maiky76

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#8
This is a review and detailed measurements of the Boston Acoustics A 25 bookshelf speaker. I purchased these a while back at a discount. Seems that they were originally released back in 2011 for US $300 a pair. At the time I purchased them the price had dropped to US $180 a pair. There were taxes and shipping costs added to the price. After discount, my net cost was $155.

The fit and finish of the speaker belies its very low price:

View attachment 94213

As you see there is some kind of faux leather surrounding the front baffle. Same is used underneath which is useful in keeping the speaker planted. Sides are gloss which gives the speaker fair bit of class. The cabinet feels dense, solid and heavy for its size.

Back panel shows nice provisions for hanging the unit and same leatherette finish:

View attachment 94214

Hard to imagine this speaker is being sold for so little. Externally anyways....

Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise. Both of these factors enable testing in ordinary rooms yet results that can be more accurate than an anechoic chamber. In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room.

I performed over 100 measurement which resulted in error rate of more or less 1%.

Temperature was 58 degrees F. Measurement location is at sea level so you compute the pressure.

Measurements are compliant with latest speaker research into what can predict the speaker preference and is standardized in CEA/CTA-2034 ANSI specifications. Likewise listening tests are performed per research that shows mono listening is much more revealing of differences between speakers than stereo or multichannel.

Reference axis was the tweeter center.

Boston A 25 Measurements
Acoustic measurements can be grouped in a way that can be perceptually analyzed to determine how good a speaker is and how it can be used in a room. This so called spinorama shows us just about everything we need to know about the speaker with respect to tonality and some flaws:

View attachment 94215

I must say at first I thought this was rather chewed up. But if we ignore the upper frequencies above 10 kHz, the rest is not too bad. We have a bit of peaking around 900 Hz. And a dip around 3 kHz.

Directivity is actually decent which means we can a) EQ the response and b) response will not be too room dependent.

The issue at 900 Hz becomes obvious when we look at the nearfield measurements of each sound radiating element:

View attachment 94216

The port becomes a bit crazy above its intended response and generates a couple of peaks. In addition, we see the tweeter having rather non-flat response.

The tweeter seems to have a steeper roll off than the woofer causing the dip in the crossover region.

Back to our spinorama, here is our early window reflections:

View attachment 94217

Like most speakers, floor reflections have a large dip and is best avoided with a thick carpet (which my listening room has).

Predicted in-room response is:

View attachment 94218

Impedance curve shows the resonances we have discussed:

View attachment 94219

Horizontal beam width is actually quite decent:

View attachment 94221

As is contour of the same:
View attachment 94222

They have made an attempt to narrow the gap between the woofer and tweeter and it shows in better vertical response:
View attachment 94223

Edit: forgot the distortion graphs:
View attachment 94228

View attachment 94229


Boston A25 Listening Tests
I placed the A25 in my usual far-field setting. First impression was positive. Certainly better than casual glance of the spin data. Some touch up EQ nicely lifted the response:
View attachment 94224

I tried to lift the drip but it subjectively made the speaker sound bright on some tracks so I took it off. As I noted earlier, I have a thick carpet so the predicted in-room response for me is better than what I showed.

The first filter is to get rid of distortion. It took away a bit of bass so you may want to play with it. The dip to get rid of the resonance was effective of making the sound lighter and vocals to stand out a bit more which I liked. The final shelving was to get rid of occasional brightness depending on track. I hate the fact that we have no production standards so sometimes seems impossible to actually tailor the overall "target curve."

Once there, the sound was quite nice. I listened for good 30 minutes and track after track sounded beautiful. Here is an example from Gait Kelin Kromhof:

View attachment 94225

Sorry, there is no youtube track for it. It is superb music that is very well recorded and it sounded great on the A25.

Dynamics were superb here and I could detect no sign of distortion at every high volumes. That said, if you listen to the port in the back, it sure sounded distorted and badly so. My back wall is from far from the speaker so I could not hear it from the front. If your situation is different, then the experience may not be as rewarding as it was for me.

Conclusions
The fit and finish of the Boston Acoustics A25 matches a speaker north of $800 a pair. It is hard to imagine how they pulled it off at such a low price. Objectively, the response is not ideal but somehow the mistakes are not that big with respect to audibility and easily corrected. While the speaker seems discontinued, searching for good prices as I did on clearance is an excellent idea. You will certainly get a speaker with far more power capability and better tonality than most budget speakers.

I am going to put the Boston A 25 on my recommended list.

------------
As always, questions, comments, recommendations, etc. are welcome.

Could no longer walk in our garage. So took out of main barbeque grill and smoker and put them on the deck. Now I have more space and ability to cook in winter just as well! Why do I say this? Because it sure would be good to have some money sent my way for meet to smoke! Have to eat good in winter or depression can set in with the gloomy days we have!

Appreciate any donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
Hi,

Here are some thoughts on the EQ.

Score no EQ: 3.27
With Sub: 5.89
  • Issue at 900Hz
  • Too much HF but the grille may help there
  • no significant 80-200Hz boost as often seen on bookshelves but not much LF output
  • 2-4kHz range recessed due to Xover design
  • Response not too bad but uneven hence the lower score than expected
  • Funny to see the same 300Hz issue that J. Atkinson measured
  • Does look OK when properly EQed
The raw data with corrected ER and PIR, Spinorama with no EQ:
Boston Acoustics A25 No EQ Spinorama.png

Directivity:
Better stay at tweeter height
Better +/-10 to 20deg off axis with the speaker line of sight crossing in front of the listening position.
This helps with the 5500 peak and the 10kHz+ range
Boston Acoustics A25 LW better data.png

Boston Acoustics A25 2D surface Directivity Contour Only Data.png

EQ design:
I have generated two EQs. The APO config files are attached.
  • The first one, labelled, LW is targeted at making the LW flat (no grille)
  • The second, labelled Score, starts with the first one and adds the score as an optimization variable.
  • The EQs are designed in the context of regular stereo use i.e. domestic environment, no warranty is provided for a near field use in a studio environment although the LW might be better suited for this purpose
Score EQ LW: 4.98
with sub: 7.5
Score EQ Score: 5.38
with sub: 7.9

Code:
Boston Acoustics A25 APO EQ LW 96000Hz
November182020-140703

Preamp: -2 dB

Filter 1: ON PK Fc 939 Hz Gain -3.45 dB Q 7.45
Filter 2: ON PK Fc 1075 Hz Gain -1.1 dB Q 7.09
Filter 3: ON PK Fc 1311 Hz Gain -1.7 dB Q 8.37
Filter 4: ON PK Fc 2826 Hz Gain 2.1 dB Q 3
Filter 5: ON PK Fc 5545 Hz Gain -1.54 dB Q 3.22
Filter 6: ON PK Fc 11291 Hz Gain -3.15 dB Q 3.45
Filter 7: ON PK Fc 15000 Hz Gain -2.28 dB Q 3

Boston Acoustics A25 APO EQ Score 96000Hz
November182020-135731

Preamp: -1.9 dB

Filter 1: ON PK Fc 926 Hz Gain -2.77 dB Q 5.72
Filter 2: ON PK Fc 1031 Hz Gain -0.94 dB Q 5.77
Filter 3: ON PK Fc 1287 Hz Gain -1.32 dB Q 6.46
Filter 4: ON PK Fc 2763 Hz Gain 2.1 dB Q 2.49
Filter 5: ON PK Fc 5780 Hz Gain -2.31 dB Q 2.15
Filter 6: ON PK Fc 10950 Hz Gain -3.54 dB Q 2.74
Filter 7: ON PK Fc 15150 Hz Gain -2.53 dB Q 2.86
Boston Acoustics A25 EQ Design.png

Spinorama EQ LW
Boston Acoustics A25 EQ LW Spinorama.png

Spinorama EQ Score
Boston Acoustics A25 EQ Score Spinorama.png

Zoom PIR-LW-ON
Boston Acoustics A25 Zoom PIR-LW-ON.png

Regression - Tonal
Boston Acoustics A25 Regression-Tonal.png

Radar no EQ vs EQ score
Large improvements
Boston Acoustics A25 EQ Score Radar.png

The rest of the plots are attached.
 

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napilopez

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#10
I actually think this is remarkably solid for an older model sold so cheap. Directivity is especially well controlled and on the whole it seems much less afflicted by major resonances and port issues than I would expect at the price. Even distortion looks decent to me for the cabinet size.

We see so many small cheap bookshelf speakers with major resonances in the lower miss or giant cancellations due to the port. They are a tad bright it seems, but that's mostly about 10kHz so listening 20 degrees off axis will probably do the trick for many listeners. Note that they are a wider directivity design and are therefore hurt by a less negative PIR than usual, in terms of the score. And fixing the speaker appears to require best basic EQ.
 
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#11
Thank you so much for this review, Amir. Impeccable timing, as these were my main speakers for the last 7 years but I just placed an order for the Focal Aria 906 yesterday.
Now I'm actually considering cancelling my order, if the Aria 906 is not a reasonable upgrade to what I already have. I have a room about 16ft2 room with somewhat low ceiling and intend to use them on my desk (elevated to about ear level). I am not playing at high volumes nor I intend to do that in the near future.

Am I making an unreasonable choice to try to change this speaker for the Focal (550€ delivered)?
 
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Blumlein 88

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#12
I use both the A25 and A26 in a secondary (5.2) system. Leaving the grill on makes them sound less bright.
Yes a relative had this on his flat screen TV. One of those models with about a 20 watt amp built in for external speakers. We put a thin layer of cotton cloth behind the grill which helped even more.

I thought they sounded okay. Not bad, nothing you'd notice about how good they were. But they did okay and didn't bring bad notice to themselves for movies and some music use. Pretty good for the price especially back several years ago.
 

infinitesymphony

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#15
Great to see something from Boston Acoustics reviewed. I'm not sure Boston exists as more than a brand name anymore, but here's the timeline as I remember it. You're likely to run into the original A series from the '80s, then the HD series, then a number of computer speakers in the mid- to late '90s during their partnership with Gateway 2000, low to high end car audio systems, the VR series, and finally the VR-M series. Then D&M Holdings acquired Boston Acoustics in 2005 and the brand quickly started to change into a budget outfit, eliminating flagships, focusing more on installation speakers, and targeting lower price points, and this coincided with a gradual change to the Boston logo you see on the speaker in this review. It's a shame because the VR and VR-M series were legitimately good, and the big-box-store oriented models that came after those paled in comparison.

A couple of flagship selections from their penultimate and final eras:

Boston Acoustics VR975, each with its own powered 10" subwoofer, F3 25Hz (!)

Boston Acoustics VR-M90, their final flagship
 

wwenze

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#16
Here are some pics of the internals (drivers, cabinet, stuffing, port, crossover) of their bigger brother, the A26 (with a larger woofer):

Boston A26 internals
I feel relief when I see photographers do this while taking a photo of the back of the woofer. It pains me to see people rest the woofer down on a flat surface and let the surround get squashed by the weight of the woofer, which is often not insignificant.

 

ROOSKIE

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#17
I owned this speaker and the more expensive model the M25.

I thought this speaker was decent, it did have a lot of port noise if running full range.

The M25 which was the step up and used SB Acoustics drivers. It sounded wonderful although it also had that same horrid port noise.

Both speakers could play loudly well and actually the M25 when crossed at 65 hrz could take massive amounts of power and play very loud with ease. It was impressive for a very small speaker.
 

ROOSKIE

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#18
Great to see something from Boston Acoustics reviewed. I'm not sure Boston exists as more than a brand name anymore, but here's the timeline as I remember it. You're likely to run into the original A series from the '80s, then the HD series, then a number of computer speakers in the mid- to late '90s during their partnership with Gateway 2000, low to high end car audio systems, the VR series, and finally the VR-M series. Then D&M Holdings acquired Boston Acoustics in 2005 and the brand quickly started to change into a budget outfit, eliminating flagships, focusing more on installation speakers, and targeting lower price points, and this coincided with a gradual change to the Boston logo you see on the speaker in this review. It's a shame because the VR and VR-M series were legitimately good, and the big-box-store oriented models that came after those paled in comparison.

A couple of flagship selections from their penultimate and final eras:

Boston Acoustics VR975, each with its own powered 10" subwoofer, F3 25Hz (!)

Boston Acoustics VR-M90, their final flagship
You are missing the M series which was excellent and the VS series which was beyond excellent.
Seriously good speakers many of which used SB Acoustics drivers that at the time were quite a driver.

Here is the M350 the last Boston series ever, I had a pair for awhile. They went for around $2500 a pair then fire sold for $600-700 a pair. Seriously good, 5 starts in my book (but did have port noise so needed to be high passed.)

1605686029797.png

M25
1605686347315.png


Here is the VS260 monitor from the previous generation.
A very highly sought after unit. Still sells fast on eBay and Audiogon ect.
1605686225286.png
 

Beave

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#19
Great to see something from Boston Acoustics reviewed. I'm not sure Boston exists as more than a brand name anymore, but here's the timeline as I remember it. You're likely to run into the original A series from the '80s, then the HD series, then a number of computer speakers in the mid- to late '90s during their partnership with Gateway 2000, low to high end car audio systems, the VR series, and finally the VR-M series. Then D&M Holdings acquired Boston Acoustics in 2005 and the brand quickly started to change into a budget outfit, eliminating flagships, focusing more on installation speakers, and targeting lower price points, and this coincided with a gradual change to the Boston logo you see on the speaker in this review. It's a shame because the VR and VR-M series were legitimately good, and the big-box-store oriented models that came after those paled in comparison.

A couple of flagship selections from their penultimate and final eras:

Boston Acoustics VR975, each with its own powered 10" subwoofer, F3 25Hz (!)

Boston Acoustics VR-M90, their final flagship
After the HD series, they had several CR series speakers (CR6, CR8, CR9, and others), then another round of updated CR series (CR57, CR77, others). These would have been late 90s through the 2000s.

In the 2010s they had the RS series, which included the RS240 and RS260 bookshelf speakers and the RS326 towers.

Following the RS series was the M series in the mid 2010s, which included the M25 bookshelf, and the M340 and M350 towers, among others.

These were all mid-level speakers in their lineups.

The VS series of the early 2010s was their final flagship line and successor to their older VR and VR-M speakers. The VS series included VS240, VS260 bookshelf speakers, and VS336 towers. These used SB Acoustics woofers and SB Acoustics dimpled-dome tweeters.
 

Beave

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#20
You are missing the M series which was excellent and the VS series which was beyond excellent.
Seriously good speakers many of which used SB Acoustics drivers that at the time were quite a driver.

Here is the M350 the last Boston series ever, I had a pair for awhile. They went for around $2500 a pair then fire sold for $600-700 a pair. Seriously good, 5 starts in my book (but did have port noise so needed to be high passed.)

View attachment 94273
M25
View attachment 94275

Here is the VS260 monitor from the previous generation.
A very highly sought after unit. Still sells fast on eBay and Audiogon ect.
View attachment 94274
The VS series used more expensive drivers than the M series.

Also, there is a pair of VS260s right now on US Audio Mart. They've been on there for months. They used to be mine before I sold them to the person who is now selling them. I don't think they've ever been opened (I had two pairs - one opened and one never opened). Edit: Nope, these are the opened pair I guess.

The VS series was probably the best they ever did. The VS260s I had sounded quite nice, and they looked great - but that curved cabinet is very awkward on stands. That was my biggest problem with them, especially living in a multi-story building in an area prone to earthquakes!
 
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