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Affordable Accuracy Monitor Review

amirm

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#1
This is a detailed measurements of a modified Pioneer SP-BS22-LR speaker by @Dennis Murphy called Affordable Accuracy Monitor (AAM). He was kind enough to send me a sample. I let him explain the mods but basically the tweeter was replace with a higher quality one and a new modified crossover was put in place. Some padding was also added to the cabinet. He sold the modified pair for US $168 plus shipping. He no longer does this and has put his modifications in public domain.

The Pioneer BS22 was obviously designed to fit a ridiculously low manufacturing cost point of view especially considering the nice touches such as the curved cabinets and such. I liked the sample I tested in near-field. In this review I will be testing Dennis' speaker in far field.

Visually the speaker doesn't look much different:

Dennis Murphy Affordable Accuracy Monitor Speaker Pioneer Review.jpg


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.

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

Dennis Murphy Affordable Accuracy Monitor Speaker Pioneer CEA-2034 Spinorma Frequency Response...png


The modification is hard to see on this graph until we overlay the original on-axis response of the Pioneer on it:

Dennis Murphy Affordable Accuracy Monitor Speaker Pioneer CEA-2034 Spinorma Compared to SP-BS2...png


We see that the response is much closer to the target flat on-axis response we look for good performing speakers.

While I don't usually put a lot of emphasis on vertical dispersion, I was surprised to see good bit of improvement there:

Dennis Murphy Affordable Accuracy Monitor Speaker Pioneer CEA-2034 Spinorma Vertical Directivi...png


Early reflections are well behaved and smooth:

Dennis Murphy Affordable Accuracy Monitor Speaker Pioneer CEA-2034 Spinorma early Window Frequ...png


This results in very nice predicted in-room response:
Dennis Murphy Affordable Accuracy Monitor Speaker Pioneer CEA-2034 Spinorma Predicted In-room ...png


Here is the before and after of the same:

Dennis Murphy Affordable Accuracy Monitor Speaker Pioneer CEA-2034 Spinorma Predicted In-room ...png


I think the bigger deal here is the reduction of distortion in the tweeter so let's compare the two:

Dennis Murphy Affordable Accuracy Monitor Speaker Pioneer distortion relative to frequency Mea...png


The crossover frequency (I think) is around 3 kHz. Notice how the distortion is basically brought to nothing on the modified version on the left above that. Whereas the original produces good bit of distortion especially around 5 kHz.

Comparing 86 and 96 dB SPL @ 1 meter on Dennis' speaker we see this tweeter is clean almost regardless of power:

Dennis Murphy Affordable Accuracy Monitor Speaker Pioneer Distortion frequency Measurements.png


It is the woofer that is going nuts as indicated before. There is so much this cheap little 4 inch woofer can produce.

Here are our directivity and waterfall measurements:

Dennis Murphy Affordable Accuracy Monitor Speaker Pioneer Horizontal Directivity Measurements.png


In mid-frequencies the dispersion is as wide as +- 100 degrees. Even at 20 kHz you have good bit of width to not having to lock your head a vice to listen.

Even vertical dispersion allows some room to be above or below the tweeter:
Dennis Murphy Affordable Accuracy Monitor Speaker Pioneer Vertical Directivity Measurements.png


I did not try to optimize the waterfall. It is looking too good to be right!

Dennis Murphy Affordable Accuracy Monitor Speaker Pioneer CSD waterfall Measurements.png


Finally, here is the impedance graph:

Dennis Murphy Affordable Accuracy Monitor Speaker Pioneer  Impedance and Phase relative to fre...png


Speaker Listening Tests
Regular readers of ASR know that per research, I listen to speaker in mono, placed to the left. Mono listening let's one judge the tonality of the speaker and its distortions much easier (a lot less perceptual masking). The performance of Affordable Accuracy Monitor in a word of superb! I could not believe how well it played through track after track in my reference list. Anyone who thinks mono listening can't sound good, should try listening to a well designed speaker. Alternatively, I suggest turning off one of the channels in your system and see how much you like the sound!

Sure, the bass driver craps out all of a sudden when you play loud with low frequency content. I adjusted the volume so that it was high enough in my huge space while avoiding its limit. I was then greeted with some of the best mid to high frequency presentation I had heard. Female vocals were to die for. Anything with a high frequency transients was produced with a clarity and beauty that was uncanny. They stood out not be cause they were over emphasized but because they were so clean and for a lack of a better word, "hi-fi."

I was surprised that even male vocals sounded wonderful. Play some Muddy Waters and you would have a smile on your face.

You could easily sense the dual personality of this speaker. Play something with just low notes and the sound was ordinary. Some piano tracks left me empty this way. But anything with modicum of full spectrum would bring ear to ear smile to my face.

I sat there for at least an hour going through my long playlist. I did not want to stop but stop I had to as it was past midnight and I was keeping my wife awake. :)

Note that my playlist was generated from listening to my library on my Revel Salon 2 speakers (around $23,000 a pair). This little speaker shows that if you follow the science with flat on-axis response and low distortion, you can emulate a lot of that experience with just $168. If the while industry did this, then we would have many good speakers that do justice to our content regardless of who designed them.

Conclusions
I am saddened that this little jewel is not produced anymore. I fully understand as I can't imagine buying these speakers and spending another $86 in parts and selling them for just $168. It would be definition of slavery in my opinion. :) I wish you all could sit here and listen to this speaker providing excellent enjoyment to well recorded music with just some limitations on bass and low-frequency loudness.

I am going to try to buy this sample from Dennis and hopefully one day use it for blind listening tests with our audiophile group.

Naturally, I highly recommended the Affordable Accuracy Monitor (AAM) if you can get your hands on it.

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

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MZKM

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#7
Comparison with the Pioneer it's modded from:
New Project.gif

Don't even ask me how long it took me to figure out how to create GIFs and have them displayed in-sync (this site doesn't play them in-sync, so I had to combine them)
  • Sensitivity is decreased by 2dB (Claimed the same 85dB, for shame Dennis :p)
  • The tweeter's horizontal dispersion is much more linear; it uses the Peerless BC25TG15 (~$30/pair), which I have been at awe of in terms of measurements, hard to beat <$400/pair as a whole package (linearity, sensitivity, smooth directivity, and distortion) if only going by the other tweeters measured on that site.
  • The vertical dispersion is much more tight-knit, so better at near-field usage.
  • Dennis, any reason why you kept the 3kHz crossover point and didn't lower it? The directivity would have been better matched. Too much distortion, dispersion issues, etc??
Here is detailed info on the mod (slightly altered).
 
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Matthew J Poes

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#8
Dennis is a really talented crossover designer. Not just because he can make expensive speakers that perform well, but because he can do the same cheaply.

I’m also glad Amir measured these. Now I can complaint to Dennis that i was in fact correct that the Pioneers have a distortion issue in the treble. I did comprehensive measurements on these a few years back and noted that the distortion rose dramatically near the crossover point when played back at levels that are modest in a room. He didn’t measure distortion but strongly disagreed with me that there was ant such problem in the original design. Yet clearly his upgrade and replacement of that problematic tweeter dramatically lowered the distortion.
 

napilopez

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#9
P.S. @amirm and anyone looking at the graphs, the scaling is different from your usual(~40dB rather than 50), so the speaker doesn't look as flat as one would expect at a glance. Dunno if you want to redo the images but might be worth noting. The DI curves are also cut off.
 

Webninja

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#11
I am saddened that I didn’t pull the trigger on any of the Dennis Murphy speakers when he was still making them. I wonder how the BMR and my favorite, Philharmonic 3s measure.

I think the BMR can be bought as a kit. What about the 3’s @Dennis Murphy, are those available as a kit?
 
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#12
Amir, thank you for doing this evaluation/review! I’ve been waiting for it for a while and have been procrastinating on doing the Murphy mods to my pair (I have all of the parts but no time at the moment). The tweeters in the modded speakers are well regarded in the DIY universe but are very inexpensive. I think I paid less than $20 when I bought mine from PE.

If you liked the inexpensive Pioneers, I suspect you would have loved Dennis’ BMRs. Voicing is similar but much better parts and more sophisticated design. Dennis has been so generous with his time and advice to the DIY speaker building crowd over the years. I’m glad to see his most penny pinching design perform so well in your testing.

Dennis stopped offering the Pioneers (before he retired) and sold a modded version of a Partsexpress kit speaker for a while. I believe it had a much better bass performance (better woofer than the Pioneer) with similar high frequency performance.
 
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#13

napilopez

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#14
One thing I've noticed from Dennis' designs is how smooth they seem to be around the upper mids/presence region that I often feel speakers mess up. I regret more than ever never buying the BMRs at their original price :D. If I didn't have new speakers coming in to test every few weeks, those seem to check all the boxes for me...
 

VintageFlanker

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#15
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MZKM

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#16
can't seem to find it on their website... there's a new version of it though...
http://www.philharmonicaudio.com/pa_archive/aa.html
Here is a cache of the AAM listing:
http://web.archive.org/web/20140624210748/http://philharmonicaudio.com/folio-me/html/Phil Pages/AALS.html

@Dennis Murphy, since you excluded shipping from the price, and to have it be somewhat accurate with price comparisons, I put the speaker as $190 in my spreadsheet, is that somewhat accurate?
He also had a Slim tower that isn’t listed on his legacy offerings.
 

MZKM

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#17
Comparing 86 and 96 dB SPL @ 1 meter on Dennis' speaker we see this tweeter is clean almost regardless of power:

It is a 93dB sensitive tweeter, so you are just feeding it an 8ohm equivalent of 2W!

Do you have the impedance/phase chart?


_______
I was surprised that even male vocals sounded wonderful. Play some Muddy Waters and you would have a smile on your face.
I am pretty sure you mean the singer, but there is a song Muddy Waters from the somewhat androgynous female singer LP, a song you even posted about.
 
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jasonq997

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#18
I would be curious about how my updated version of the "Affordable Accuracy" measure. These were based on a widely available Dayton kit from Parts Express. I had an email exchange with Dennis a few months ago, where he informed me that he is no longer making speakers, and that he offered the crossover for the Dayton Affordable Accuracy version to Parts Express and that they turned him down. That is a real shame, since I prefer these to multiple budget speakers that got good reviews here.
 

mrmoizy

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#19
Wow - exceptional. Does anyone know where to find info on this mod "in the public domain"? I did some Googling and came up empty, kept finding information on the new version which is based on a Dayton Audio/Parts-Express DIY kit.

Edit: only could find info on the kit jasonq997 mentions above
 

mrmoizy

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#20
Wow - exceptional. Does anyone know where to find info on this mod "in the public domain"? I did some Googling and came up empty, kept finding information on the new version which is based on a Dayton Audio/Parts-Express DIY kit.

Edit: only could find info on the kit jasonq997 mentions above
Took a different tact, found this: https://www.audiocircle.com/index.php?topic=128301.0
 
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