Bose 901 Series VI ver 2 Active Equalizer (Final Edition)
Measurements and Review
Part 1: The Bose 901 Series VI:
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Part 2: The Bose Model 901 '68 Edition:
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In the very last article of this Bose 901 trilogy, I'll be looking at the Bose 901 Series VI ver 2. It was never clear why Bose chose not to call it a Series VII since it had a dramatic change in the drivers. Some hoped that there would be an 50th anniversary edition in 2018, but instead the Bose 901 was discontinued. Still, the Series VI ver 2 has a newer generation surround for the drivers as well as a new equalizer.
Series VI
Series VI ver 2
The Series VI equalizer has a well-dampened slider. The Series VI ver 2 has less resistance, physically, but there is a center "detent" or click. I used this position for the measurements. I ran it in the default Bass 1 mode which is the slightly boosted Bose house curve (which honestly is similar to Harman's house curve). The other difference is that my Series VI ver 2 equalizer has a green power LED whereas my original Series VI had a red power LED.
Electrical Measurement
80.6 dB
1 kHz SINAD
Same SINAD, but it's an improvement in both noise and THD. It's the 60 Hz AC mains noise that is worse in this unit. It may be variability, or the "electrical weather" at my home for the day. I was able to measure 81.0 dB SINAD once, but I just copy-pasted the image and the forum software lost my draft.
The Active Equalizer is also a slightly different slope with a seemingly greater treble boost relative to the bass. In the previous Series VI model, the peak bass and treble boosts matched.
Electrical Distortion (Equalizer)
Distortion is reasonable for the equalizer (shown here as %)
When comparing the Series VI vs Series VI ver 2, it looks generally similar, explaining why Bose chose not to call it a Series VII.
You can see the differences more clearly with more smoothing.
The ver 2 is slightly flatter in the midrange, but the bass is better in ver 1.
You can also look at distortion at Bose's 30 to 15 kHz and can see that the distortion on the Series VI ver 2 is slightly lower overall. In ver 2, most of the distortion is under 0.5% whereas the ver 1 seems to average 0.5%
Speaker-level Distortion
Subjective Impressions
The midrange/vocals do seem to be a bit cleaner with ver 2, but the reduced bass is noticeable. I didn't measure IMD, but my impression is that the Series VI ver 2 has improved IMD in that vocals are similarly good between both speakers when it's someone singing with minimal background music whereas the ver 2 has greater clarity of the vocals when there is a complex band playing as well. This difference in clarity is relatively subtle, but difference in bass extension is not subtle at all!
Running the JBL 708P in roughly the same position as the Bose 901's shows that the Series VI ver 2 more closely matches the the 708P's bass. You can also see how an un-corrected JBL 708P has a big dip in the bass (from the room) whereas the reverberations of the 901 help to fill that out (with the trade-off of comb filtering).
Swapping the equalizer units didn't change the sound beyond the different frequency response curve. No matter which equalizer unit I used, the drums were more convincing on the original Made-in-Canada Series VI while in complex passages, the vocals were slightly cleaner with the Made-in-Mexico Series VI ver 2.
Conclusion
Measurements help bust audiophile myths.
First, these measurements suggest that the phrase: "No highs, No lows, must be Bose" does not apply to the Bose 901 when used with the Active Equalizer. Maybe people assumed the equalizer offered a simple smiley face EQ boost and assumed that the speaker without the equalizer was the truest response. Maybe people assumed the Acoustimass 5 cubes reflected the sound of the Bose 901.
Second, there is misinformation about the original, sealed Bose 901's (Series I and II) offering better bass provided that you had enough amplification power and it was simply that the 901 came to market when tubes were still common. That's not true at all. The newer models provide deeper bass whether you use a tube or solid state amplifier. Advances in the full-range speaker driver also provide a cleaner frequency response, so the "sealed" original design is not inherently better. I did really enjoy the original when using advanced software EQ, and there's a possibility that I just need to restore my '68 Edition equalizer.
Third, there's a lot of misinformation on the 'net about there being no difference in sound quality beyond the Series V other than cosmetics. There are even reports that Bose themselves reported that there was no difference between VI and VII ver 2, although the internet discussion does talk about subtle differences. The forum posts I saw also fail to distinguish between Bose engineers and Bose retail store salespersons as the source for the claim that the VI and VII ver 2 were the same. With these measurements, we see that there is a clear difference in the equalization curve from "Series VI" versus "Series VI ver 2."
Fourth, in my previous Bose 901 threads, there have been comments "I heard these speakers in 1970 and hated them." By looking at these generations, it becomes clearer that this would be similar to saying that you drove a Mercedes S-class in 1972 and didn't like it, so you don't understand the point of an S-class today. While the Bose 901 kept the overall dimensions, the 11%/89% percent direct/reflecting ratio, and use of full-range speaker drivers, it's pretty clear that each generation was a bit different with measured electrical performance of the equalizer getting better between launch and final version as well.
I've had fun exploring these different Bose 901's and I'm done with the measurements. Now it's time to just sit back and enjoy the music.
That is, unless someone has the Bose 901P's which has a different driver complement as it appears to be 16 ohm impedance rather than 8 ohms, and utilized yet another variant of the equalizer. To my knowledge, this is the true "final flagship" of the Bose 901 concept.
Measurements and Review
Part 1: The Bose 901 Series VI:
Bose 901 Series VI Active Equalizer Measurements
Bose 901 Series VI Active Equalizer Measurements The Bose 901 Series V has been measured on the Klippel NFS. In Erin's measurements, he noted that the equalizer added an extreme level of distortion. I recently tried a Series VI in my own home and came around incredibly impressed with the...
www.audiosciencereview.com
Part 2: The Bose Model 901 '68 Edition:
Bose Model 901 Active Equalizer ('68 Edition) Measurements
Bose Model 901 Active Equalizer ('68 Edition) Measurements I was able to source an original Bose Model 901 Active Equalizer (Series One). While there is no serial number on the equalizer, it was part of a set that had one Bose Model 901 speaker with a serial number BELOW #800. The matching...
www.audiosciencereview.com
In the very last article of this Bose 901 trilogy, I'll be looking at the Bose 901 Series VI ver 2. It was never clear why Bose chose not to call it a Series VII since it had a dramatic change in the drivers. Some hoped that there would be an 50th anniversary edition in 2018, but instead the Bose 901 was discontinued. Still, the Series VI ver 2 has a newer generation surround for the drivers as well as a new equalizer.
Series VI
Series VI ver 2
The Series VI equalizer has a well-dampened slider. The Series VI ver 2 has less resistance, physically, but there is a center "detent" or click. I used this position for the measurements. I ran it in the default Bass 1 mode which is the slightly boosted Bose house curve (which honestly is similar to Harman's house curve). The other difference is that my Series VI ver 2 equalizer has a green power LED whereas my original Series VI had a red power LED.
Electrical Measurement
80.6 dB
1 kHz SINAD
Same SINAD, but it's an improvement in both noise and THD. It's the 60 Hz AC mains noise that is worse in this unit. It may be variability, or the "electrical weather" at my home for the day. I was able to measure 81.0 dB SINAD once, but I just copy-pasted the image and the forum software lost my draft.
The Active Equalizer is also a slightly different slope with a seemingly greater treble boost relative to the bass. In the previous Series VI model, the peak bass and treble boosts matched.
Electrical Distortion (Equalizer)
Distortion is reasonable for the equalizer (shown here as %)
When comparing the Series VI vs Series VI ver 2, it looks generally similar, explaining why Bose chose not to call it a Series VII.
You can see the differences more clearly with more smoothing.
The ver 2 is slightly flatter in the midrange, but the bass is better in ver 1.
You can also look at distortion at Bose's 30 to 15 kHz and can see that the distortion on the Series VI ver 2 is slightly lower overall. In ver 2, most of the distortion is under 0.5% whereas the ver 1 seems to average 0.5%
Speaker-level Distortion
Subjective Impressions
The midrange/vocals do seem to be a bit cleaner with ver 2, but the reduced bass is noticeable. I didn't measure IMD, but my impression is that the Series VI ver 2 has improved IMD in that vocals are similarly good between both speakers when it's someone singing with minimal background music whereas the ver 2 has greater clarity of the vocals when there is a complex band playing as well. This difference in clarity is relatively subtle, but difference in bass extension is not subtle at all!
Running the JBL 708P in roughly the same position as the Bose 901's shows that the Series VI ver 2 more closely matches the the 708P's bass. You can also see how an un-corrected JBL 708P has a big dip in the bass (from the room) whereas the reverberations of the 901 help to fill that out (with the trade-off of comb filtering).
Swapping the equalizer units didn't change the sound beyond the different frequency response curve. No matter which equalizer unit I used, the drums were more convincing on the original Made-in-Canada Series VI while in complex passages, the vocals were slightly cleaner with the Made-in-Mexico Series VI ver 2.
Conclusion
Measurements help bust audiophile myths.
First, these measurements suggest that the phrase: "No highs, No lows, must be Bose" does not apply to the Bose 901 when used with the Active Equalizer. Maybe people assumed the equalizer offered a simple smiley face EQ boost and assumed that the speaker without the equalizer was the truest response. Maybe people assumed the Acoustimass 5 cubes reflected the sound of the Bose 901.
Second, there is misinformation about the original, sealed Bose 901's (Series I and II) offering better bass provided that you had enough amplification power and it was simply that the 901 came to market when tubes were still common. That's not true at all. The newer models provide deeper bass whether you use a tube or solid state amplifier. Advances in the full-range speaker driver also provide a cleaner frequency response, so the "sealed" original design is not inherently better. I did really enjoy the original when using advanced software EQ, and there's a possibility that I just need to restore my '68 Edition equalizer.
Third, there's a lot of misinformation on the 'net about there being no difference in sound quality beyond the Series V other than cosmetics. There are even reports that Bose themselves reported that there was no difference between VI and VII ver 2, although the internet discussion does talk about subtle differences. The forum posts I saw also fail to distinguish between Bose engineers and Bose retail store salespersons as the source for the claim that the VI and VII ver 2 were the same. With these measurements, we see that there is a clear difference in the equalization curve from "Series VI" versus "Series VI ver 2."
Fourth, in my previous Bose 901 threads, there have been comments "I heard these speakers in 1970 and hated them." By looking at these generations, it becomes clearer that this would be similar to saying that you drove a Mercedes S-class in 1972 and didn't like it, so you don't understand the point of an S-class today. While the Bose 901 kept the overall dimensions, the 11%/89% percent direct/reflecting ratio, and use of full-range speaker drivers, it's pretty clear that each generation was a bit different with measured electrical performance of the equalizer getting better between launch and final version as well.
I've had fun exploring these different Bose 901's and I'm done with the measurements. Now it's time to just sit back and enjoy the music.
That is, unless someone has the Bose 901P's which has a different driver complement as it appears to be 16 ohm impedance rather than 8 ohms, and utilized yet another variant of the equalizer. To my knowledge, this is the true "final flagship" of the Bose 901 concept.
