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Bose 901 Series VI Active Equalizer Measurements

Spkrdctr

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I tested way, way back in the day 35 years ago or more the 201,301,501 and 901. IMHO the 901 was a fairly good speaker the would take some abuse and play loud. All of the others were volume limited. The 201 were junkyard specials. The 301s were on the curb specials and the 501 was perfect for someone who really is not into high quality music but wants sound. Way back then we knew you had to have the Bose EQ box or you were just getting garbage sound. Bose tried a lot of interesting stuff back then but clearly, they put about 90% of the company money into the 901s and the others got under funded by a large margin. It really helped ruin the Bose name. If the cheaper speakers had been better, I think Bose would have been a much more respected name. But, it seemed to everyone that they cheaped out on the non-901 speakers in an attempt to just make a bunch of money and it helped kill the company. The Acoustimass systems were the final nail in the coffin. The cubes actually did a pretty good to great job, but that left all the heavy lifting to the acoustimass modules and they were very, very weak. People over drove those until failure all the time. They would burn out the resistor light protection device from cooking it to death. I fixed a boat load of them. OK, TWO boat loads.......... They actually killed the company with management decisions that were terrible for the marketplace. I saw the train wreck coming and couldn't stop it. They did have fantastic commercial Bass bins that worked very well and I don't think they were all that expensive. I hurt my ears on one of those, young and dumb I was.......
 

sarumbear

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They actually killed the company with management decisions that were terrible for the marketplace. I saw the train wreck coming and couldn't stop it.
I love these “authoritative” posts. Here is some information about the company that was killed by the management.

As of 2019, Bose generated revenue of US$4 billion and employed more than 9,000 people around the world, making it one of the top 10 speaker companies in the world.
 
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GXAlan

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@DualTriode
I re-ran the measurements this morning. Noise is better this morning, but mains noise is higher (The cables did move).

-80.7 dB SINAD

1683817075004.png


With that said, with the Topping D90 at 2.118V:
1683817158801.png

1683817205213.png


It does fine with the IMD at lower frequencies. It becomes a problem in the high frequencies, which may not be a real problem since the 901 cannot reproduce these frequencies and real music doesn't have 19 or 20 kHz at 0 dBFS.
1683817250839.png


Reducing input helps
1683817332258.png


Looking at multitone, we see the same thing. Too much input voltage in the high frequencies causes distortion. Here is at 0 dBFS
1683817749420.png


versus -20 dBFS
1683817443549.png
 

Spkrdctr

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I love these “authoritative” posts. Here is some information about the company that was killed by the management.


Well, I thought they had moved out of the home audio space. But I can be wrong. Are they still making speakers for the home stereo/AVR? OK, upon checking they are big into soundbars and very small and speakers. Nothing I'd really call home audio other than background music. I meant that the killed the company in traditional speakers for home audio. I'm sure they sell a lot of soundbars on their name alone. Plus they make headphones and a lot of other stuff, so yes they are a big company. Just pivoted away from traditional home audio. I have never hear one of their soundbars, but I would never buy anything Bose due to their history, well except noise canceling headphones for airplanes.
 
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sarumbear

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Well, I thought they had moved out of the home audio space. But I can be wrong. Are they still making speakers for the home stereo/AVR?
You declared a company dead on a 300 word post but haven’t even bothered to check their website?
 

Spkrdctr

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You declared a company dead on a 300 word post but haven’t even bothered to check their website?
To be honest I haven't thought about Bose in decades. So I was a wee bit out of date.....OK, I was WAY out of date. Thank you for reminding me that I'm older than dirt! Hey, at least when I say something fairly stupid, I don't double down. I admit when I am WAY out of date and what I said does not pertain to today. But, that still doesn't mean I'm not old. Being old is a lot of work!
 

Slayer

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My experience with the Bose 901's.
About 20 years ago my wife (currently ex-wife) came home, along with her stepfather, with a pair of 901's for my birthday.
This was on a Friday. Without getting into a long story and folks feeling like i'm trying to bash Bose. I will just say, they were returned on the following Monday. I really wanted to like them, heck they were a gift. However, I just couldn't find the enjoyment from them that I was hoping for.
 

Martin

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The only place I have ever seen or heard Bose 901’s was at a - *ahem* - gentlemen’s club in San Diego’s Midway neighborhood in the 1980’s. I remember them being very “shouty” blaring 70’s and 80’s rock at ungodly volumes.

Martin
 

Aperiodic

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Has anyone considered sending a pair to GR for some mods, maybe a tweeter?
There's no crossover (all the speakers are run full range) so I don't know what there would be for them to do.
 

Aperiodic

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I love these “authoritative” posts. Here is some information about the company that was killed by the management.


They're not dead... they could get better...

Bose is a closely held company so they have no sideline-quarterback shareholders to answer to or get their officers ousted by, so they can pretty much do whatever they want as long as they are turning a profit (which they apparently are).
 

Howie Dern

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Thanks for the review!

I had a pair of the 901 VI plus the EQ box and used them on and off for years. The spatial quality of the sound was quite enjoyable but after awhile I would crave more specific soundstage placement and treble detail so I'd switch them out. I found placement in my room to be very particular but they sounded nice once you got it figured out. Never liked the tulip stands and I felt they put the speakers too low so I made a pair of sturdier stands in matching wood and with speaker wire management holes. BTW, the manual for mine rated them at unlimited power in a non-commercial application. I used an amp with 120 WPC and never had an issue with them wanting more.
 

StevenEleven

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Bose 901 Series VI Active Equalizer Measurements
View attachment 284620

View attachment 284619


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 audio. For all the harassment that Bose received from audiophiles, especially in the era of the Acoustimass 5, the actual in-room sound quality of the Bose 901 can best described with a simple "Wow." Maybe it was because my expectations were so low going into my listening tests, or I've simply lost my audiophile credibility card or suffer from early dementia, but I thoroughly enjoyed the in-room experience from the 901. When appropriately compared to a lifestyle speaker peer, I can confidently state that I prefer the 901's sound presentation over a Sonos speaker or Devialet Phantom. When compared to a traditional audiophile system, I would describe the Bose as a third spatial presentations beyond headphones or dynamic speakers. In a way, it sounds like a Magnepan without a true ribbon with less transparency and much more bass.

Science has shown us that listening in stereo can make it harder to hear differences between speakers (as compared to mono). It's likely that the Bose 901's spatial performance, in a well configured environment, is also enhancing the perceived sound quality despite the frequency response irregularities.
UvF7rx5.png

A REW sweep at my listening position playing stereo sweep through ASR's record holder for worst 5W SINAD was actually quite impressive given that this technology was fundamentally available in 1968. The original 901's apparently have even better bass response as they were sealed, but required more amplification power than was available at the time. The 901 Series III and newer are ported designs. The 901 Series VI is officially rated at 450W per channel or 250W IEC.

What immediately caught my attention was the overall low distortion at the speaker level. After all, this sweep was done with a 300B SET that will add its own distortion as well. The high frequency roll off can be the effect of comb filtering.

In-room BOSE 901 measurement (stereo)
Speaker System Performance


View attachment 284614


I decided to analyze my 901 Series VI Active Equalizer.

Manufacturer's Specifications:
View attachment 284612


Test Setup
Bose 901 Series VI Mid-Bass and Treble sliders, roughly centered
Topping D90 MQA as tone generator
@pkane MultiTone
@JohnPM REW

BOSE 901 Series VI Active Equalizer
Electrical Performance

80.5 dB

1 kHz SINAD


Bose advertised <0.09% THD, or 61 dB. Our THD+N is 80.5 dB or 0.009%, a full order of magnitude better. This is at 0 dB (2.118V from the Topping D90)
View attachment 284615

Decreasing the volume on the Topping to -6 dB (1.0608V) shows a big drop in the distortion products, although SINAD is worse due to the increase in noise.
Apologies for the change in X-axis scaling.
View attachment 284616


A REW sweep at -20 dB from the Topping D90 gives a very nice distortion profile. I have shown both the dBFS as well as % THD.
View attachment 284617
View attachment 284622

Running it at 0 dB (2.118V) shows clipping in the treble, where the EQ boost is particularly high.
View attachment 284618
View attachment 284625

Commentary
The Absolute Sound was founded after Harry Pearson was unhappy with the sound quality of the Bose 901's he purchased. Today, the Absolute Sound offers 6 recommended digital interconnects $1000 and higher.

Julian Hirsch, an objectivist audiophile, emphasized measured performance of audio gear from the earliest days of this hobby, and loved the Bose 901

He had this to say about the Bose equalizer: "The active equalizer introduces no perceptible distortion. We measured its distortion at less than 0.13 percent for any output under 3 volts, which is greater than would be required with any amplifier we know of. The output signal is of approximately the same level as the input signal."

and this to say about the system as a whole:
"I am convinced that it ranks with a handful of the finest home speaker systems of all time. Because of its unconventional mode of operation, I rather doubted that any frequency-response measurements I could make would account for the remarkable realism of its sound... The Bose 901 had an utterly clean, transparent, and effortless sound. Its clarity and definition when reproducing complex orchestral passages were, in the writer’s opinion, unsurpassed by any other speaker he has heard. This impression was confirmed by its tone-burst response, which was uniformly excellent across the frequency spectrum. Its low-bass response was difficult to credit to such a compact system. It had all the room-filling potency of the best acoustic-suspension systems, combined with the tautness and clarity of a full-range electrostatic speaker. The spatial distribution, which brings an entire wall alive with sound, contributes greatly to the sense of realism.

There is, unfortunately, a serious obstacle to the universal acceptance of a speaker such as the Bose 901. The 12-inch gap necessary between the apex of the speaker and the wall places the front of the speaker about 30 inches from the wall. Bookshelf mounting is generally impractical, and it may be difficult to install the 901 in the correct location without disturbing room decor. Many potential users will be forced to decide between style and sound."


Conclusion
I grew up with the belief "no highs, no lows, must be Bose." The only Bose 901's I ever listened to were the ones in Bose retail stores where the 901's were spaced 2 or 3 feet apart. Today, after hearing the 901 in my own home, I realize that my belief that the 901 were a horrible speaker was based upon the same kind of experts who hyped up green markers for CDs. Was it simply that in 1968, the active equalizer was considered a gimmick or too hard to set-up? Today we don't think twice about the JBL M2 or any number of speakers which are dependent on active crossovers. But back then? Did the company's infomercials and aggressive legal threats to reviewers negatively bias the impression of the speakers? Was there too much attempt to market "halo" or "trickle down" technologies where the true gem of the Bose product line never had a chance to shine?

Estimated In-Room Response from Spinorama.org
Revel F328Be = ASR-v1-20201110 (lower bass measurement, no EQ)
901 Series V = EAC with software EQ (best case)
View attachment 284630

1. The Bose 901 is better than you'd expect given its reputation among audiophiles. Given how affordable the 901 can be in the present day, it's actually a very competitive product given its in-room bass response and attractive mid-century modern appearance with the tulip stands. The Series I and II products do not have deteriorating foam while the Series VI uses a modern foam which does not appear to be as fragile.

2. The Bose Series VI active equalizer works best with lower input voltages as long as you don't run into the noise floor. When using a Bose 901 in a modern setup, consider attenuating your source. If this is not an option, Deer Creek Audio offers MiniDSP based replacement 901 equalizer solutions with their custom EQs.

3. With perfect EQ, that a Bose 901 Series V is closer to an un-EQ'd Revel F328 Be according to Spinorama.org than anyone would have imagined in the absence of measurements. Now that all of the patents behind the 901 have expired, what happens if you put together a similar speaker leveraging all of the advances in full-range transducers, contemporary DSP technology, and the benefit of oodles of clean Class D amplifier power on demand?
Fricking awesome work. Fascinating. Thanks!!! :)
 
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GXAlan

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Just a quick comparison

NEARFIELD measurement of front driver (with Bose EQ in use).

Green = as is; purple = equalized from 200 Hz to 10 kHz
1683825201339.png


Then at listening position
1683825233636.png


This does suggest that if I can equalize the driver at the nearfield level, I get improved in room response.

It's also interesting to see how the treble really carries through the whole room with 18 drivers as opposed to just one. Not sure if it’s just a measurement error or the effect of the amplifier/higher load. The amp I happen to be using is the 300B SET and I did raise the volume for the in room measurements.

@amirm
 

gnarly

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It's also interesting to see how the treble really carries through the whole room with 18 drivers as opposed to just one. Not sure if it’s just a measurement error or the effect of the amplifier/higher load. The amp I happen to be using is the 300B SET and I did raise the volume for the in room measurements.

@amirm
Like I mentioned in another thread discussing 901s, the treble (HF&VHF) is the summation of the one forward driver's direct sound,
and the 8 rearward drivers' reflections off walls.
So multiple locations producing the same frequency content, arriving at the listening position or mic.
This will show the amplitude of the response...and can be quite flat with EQ.
It won't show that the magnitude is the sum of multiple arrivals. A coherence measurement, available with dual channel FFTs, will show low coherence, meaning the measurement doesn't correlate highly with the stimulus.
This multiple arrivals aspect is what makes a frequency response that looks fine measurement wise,..... sound less sharp, less detailed, less airy, etc,
......than a single point source producing the same magnitude.
 
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GXAlan

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A coherence measurement, available with dual channel FFTs, will show low coherence, meaning the measurement doesn't correlate highly with the stimulus.
This multiple arrivals aspect is what makes a frequency response that looks fine measurement wise,..... sound less sharp, less detailed, less airy, etc,
......than a single point source producing the same magnitude.

Ah. Makes a lot of sense.

The 901’s are very much like listening to vinyl. Not accurate or detailed but enjoyable anytime you want music that sounds respectable in multiple listening positions. This is probably why it sounds good for classical music too. At the MLP, it’s also enjoyable for its spatial presentation.
 

SpaceMonkey

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It's unfortunately hard to access the original report about it, but circa 2010 there was a blind shoot out between Linkwitz Orions, Behringer monitors, and a home-made Bose 901-inspired (but better) speaker by hobbyist Gary Eickmeier that he called the "IMP"...and the Bose-inspired speakers won.

Here's a secondary reference to it, in the first post of a diyaudio thread:


Addendum: found a more detailed source of info, featuring Eickmeier himself.
Dig out the report using Wayback Machine. Didn't read the whole thread to see if it was posted here.
 

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Multicore

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My first experience with Bose was the 800 portable PA, which also required its own equalizer. It was well respected by anyone that had used it. The only criticism I remember was that it could be louder. Very likely a speaker of the same size optimized for efficiency and SPL was noticeably louder. But various musicians and sound techs remarked on its superior SQ. That was late 70s and early 80s. I came to ASR first in the late twenty-teens and that was the first time I heard of a widespread bias against the brand, as though it was some kind of inside joke. Baffling.
 

Hipster Doofus

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Thank you, always has been a curiosity. Had a pair for a short time but I did not know what I was doing…this clears up some the hype and detractors all at the same time…gosh isn’t data fun.
 

sarumbear

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