Bose 901 equalizer, 1970's vintage. What is this thing?

[Guest vanillaed]

Hi All,

I found an old (like mid to late 70's) equalizer thing made by Bose, model # 901.

What is this thing?

Does it have any monetary value???

[soundminded]

It is hard to belive anyone here does not know what this is but here goes. This is a high precision frequency response contouring device with many one percent and five percent parts. It is an integral part of the 901 system which consists of two loudspeaker units and one two channel equalizer which is intended to be inserted in the low level signal path such as in a tape monitor loop or between a preamplifier and power amplifier. It is specific to the matching 901 loudspeaker system and is of no value with any other speaker or device. Even within that limited universe, the 901 system evolved into different "series." For the original which had no series designation and the series two which used the same loudspeakers systems the equalizers were interchangable, the only difference is that the series II offered more high frequency boost settings. With series III the design of the speaker changed radically and so each series must be used only with the equalizer designed specifically for it. The frequency response equalization curves are claimed to be an exact compliment to the speaker system response for which it is intended and none other. Warning!!!! Using this equalizer with any other speaker system may cause permanent damage to the speaker. For example, the huge 18 db boost at 30 hz in the original version will push many speakers or amplifiers to their limit with relatively little input signal. In good working order, it may be worth in the range of $50 to $100 but only to someone who needs one.

[dynaco_dan]

>It is hard to belive anyone here does not know what this is

>but here goes. This is a high precision frequency response

>contouring device with many one percent and five percent

>parts. It is an integral part of the 901 system which

>consists of two loudspeaker units and one two channel

>equalizer which is intended to be inserted in the low level

>signal path such as in a tape monitor loop or between a

>preamplifier and power amplifier. It is specific to the

>matching 901 loudspeaker system and is of no value with any

>other speaker or device. Even within that limited universe,

>the 901 system evolved into different "series." For the

>original which had no series designation and the series two

>which used the same loudspeakers systems the equalizers were

>interchangable, the only difference is that the series II

>offered more high frequency boost settings. With series III

>the design of the speaker changed radically and so each series

>must be used only with the equalizer designed specifically for

>it. The frequency response equalization curves are claimed to

>be an exact compliment to the speaker system response for

>which it is intended and none other. Warning!!!! Using this

>equalizer with any other speaker system may cause permanent

>damage to the speaker. For example, the huge 18 db boost at

>30 hz in the original version will push many speakers or

>amplifiers to their limit with relatively little input signal.

> In good working order, it may be worth in the range of $50 to

>$100 but only to someone who needs one.

Hi there soundmined

You certainly have a wonderful way of knowing and expressing information.

I find you have a lot of knowledge which you openinly share with us.

Thank you.

[soundminded]

By coincidence, I have had considerable experience experimenting with the original version of this model for the last 18 months. Although flawed in its execution in some important respects which have caused most audiophiles to severely and consistantly malign it, it introduced many interesting and unique concepts besides its direct/reflecting principle such as arranging the cabinet design in a way so as to prevent internal standing waves. Its two main shortcomings were its inability to reproduce the top octave of sound which made it increasingly unacceptable to serious audiphiles as competing models improved over the years in that regard, and its overall irregular in room frequency response. It also was difficult to position in may rooms optimally and expensive to power up satisfactorily at least in its original version. However, it could have been further developed and refined IMO into a much better performing product. For example, the original design which was at the very top of all low frequency performers on the market 35 years ago could have been further improved keeping it up with or even well ahead of the best the competition could offer even today. Instead, its development took it in an entirely different direction to appeal to a mass market which was unconcerned with its limitations and it became an icon of success both financially and as a marketing symbol, much to the chagrin of its detractors. It was the first step in establishing a one billion dollar a year privately owned business. Not bad for a professor of electrical engineering and acoustics from MIT.