Will The Real Bose 901 Please Stand Up !??...A Guide To Buying Bose 901 Speakers

Mar 13, 2006 (Updated Jun 6, 2012)

Popular Products in Home Theater Speakers and Subwoofers
The Bottom Line When shopping for your dreamy used Bose 901 speaker system...know what you are getting yourself into! If something doesn't look right...question the seller big-time or stay away!

Original Review Date:8/6/2004:

Let me start off this essay by stating that my purpose here is not to open up a can of worms by inviting a discussion on the various pros and cons of the Bose 901 Speaker System but rather to clarify some rather serious misconceptions and confusion both sellers and buyers of the systems all too often encounter.

Indeed not all sellers are intentionally trying to fool the buyer but in many cases are ignorant because of various situations. In other words...the seller may not be aware of proper combinations of speakers and equalizers because perhaps the seller is not the original owner and may have received a given series of 901's without an e.q. and had to buy one separately. Believe me...I've seen it!

This may be true because the seller made his or her purchase at an estate sale or inherited the speakers from dead relatives. Maybe the seller received home made imposters and did not realize it! Also , Bose offered the speakers without the E.Q. to those only needing a second/"surround pair" or for those intending to purchase one of their stereo receivers with the 901 E.Q. built in. Also, the seller may have had the speakers reconditioned and possibly replaced a driver with an improper replacement.

Anybody who knows me knows how I feel about the Bose 901 Speaker System. With its fantastic and powerful reproduction let alone its uniquely spacious sound this transducer embraces! Nuff said. I'm not here today to talk about that but rather to address a situation of growing concern involving the buying and selling of used 901 speakers either over the internet or at that local garage sale.

As I have followed this model closely almost since its inception in 1968 to its present day status and have personally owned Series I, V and VI models...and am extremely familiar with Series II and IV...and have some familiarity with Series III...suffice it to say that I have some knowledge of the product that might be of some help to someone who "needs to know".

Although the basic design of the 901 speakers has remained the same down through the years and from series to series, there have been significant changes in various facets of the system that need to be addressed as you will see.

These changes are both cosmetic and internal in nature and aren't always readily perceived by the first time Bose 901 buyer...especially if he or she is making a "used" speaker purchase. There simply are some things to beware of when buying used 901's.

First of all...please humor me a bit and let's all take a ride on over to Ebay.com. Let's enter a search for "Bose 901 Speakers."

Wow!...There's at least a dozen pairs of 901's for sale and some of the auction bidding is quite hot! Oh oh!...Look at this! That's not right...this guy's selling a used Series V 901 with a Series IV Equalizer! And look! This person is claiming to be selling a Series III speaker when it actually is a Series II. And yet there is something not right with another 901 system as it does not appear to have the cutaway with the Bose name on the bottom of the speaker! What's going on here?

When purchasing used 901's, it is extremely important to know what series you are looking at! You may ask..."Why is this so?" Let me explain.

When Bose introduced Series I in 1968, it was not referred to as such but only after Series II was introduced in 1973 it was so tagged. If you see a used Series I speaker labeled as such, you've got a phony...and yes there are copycats out there!

The most important thing to remember when purchasing used Bose 901 speakers is that each series has its own equalizer at the heart and soul of the system. The reason Dr. Amar Bose gave for this is that typical speakers with woofers, tweeters and crossovers introduce distortion...coloration if you will that keeps the sound from being perfect.

His method of combating this problem was to use small full range drivers that did not need crossovers. The small drivers would be large enough to reproduce bass and small enough for treble frequencies. The problem was that they couldn't do it "all" by themselves and required a separate active equalizer to ensure that the concept worked.

The Active E.Q. also gave Bose the advantage of being able to smooth out any bumps or irregularities in the small drivers' response curve. This gave the Bose Corp. quite an advantage over others that had to carefully match their woofers, midranges and tweeters to the best crossovers for an ideally balanced natural sounding system.

In "Audio" there is an old expression that "more is less and less is more" when referring to tone controls and equalization. The more equalization or tonal correction required to make a speaker sound balanced the more coloration is likely to be introduced to the listener. But Bose had an advantage of making for ruler flat frequency response with the basic curve of the E.Q.

Bose 901 Equalizer Compatibility:

Undoubtedly as you read this review, someone is selling a Series IV 901 with a Series VI eq or a Series II eq with a Series III speaker and will result in total dissatisfaction with the product on the buyer's end.

On the earlier models Series I and II, a tremendous boost in the lower frequencies was required. To a lesser degree...the highs were also boosted. This placed quite a demand on one's amplifier! The fact that the basic principle of the design was Acoustic Suspension which required large movements of the drivers to produce enough air movement for bass didn't help either...but it was a great sounding system as long as you had a 200 watt/ch. or more amplifier! On later models...the boost was considerably milder as each series progressed. Later models used a form of vented design...Acoustic Marix that required much less equalization.

My point in telling you all this is that if you use a Series VI E.Q. with a Series I speaker, the sound will not be correct and sound limited. Conversely, a Series I E.Q. with a Series VI speaker will render a bright and bassy coloration. There is something to be said for using the correct E.Q. for each series 901 speaker!

Therefore...Series I & II {1968 to 1976} are compatible when it comes to mix and matching speakers and E.Q.'s.
Series III & IV {1976 to 1983} are compatible.
Series V & VI {1983 to Present Day} are compatible.

Notice that compatibility for Bose 901's are in Series pairs...I & II...III & IV...V & VI. DO NOT deviate from these guidelines as the sound will be most incorrect and you will be most frustrated!

You need a Bose 901 E.Q. with your Bose 901 speaker system otherwise forget it! You'll have sub par sound. Don't even try to substitute your top notch private E.Q. for the 901's E.Q. as it will cause the sound to be incorrect. You cannot equal the basic curve that Amar Bose has incorporated into the 901 E.Q.


All 901's have pentagonal tops and bottoms however there are differences here. Series I & II have sharp corners and do not sport the curved front panel beveled look of Series III through VI. The standard grill for these series speakers was an off white color although black and brown were optional. Also, Bose made a front walnut panel kit that the owner could install. Optional white pedestals were offered for more money!

The E.Q.'s sported a walnut enclosure with rocker and push button switches along with a high frequency round control knob.

Series III introduced the curved front panel look with plenty of walnut veneer and featured full wooden side panels. The new Acoustic Matrix Sub Enclosure could now be seen protruding the rear of the main wood enclosure's grill with three jet-like ports {the middle one being the smallest}. This type of design pushes air at amazing speeds up to 60 mph for fantastic bass response!

The popular grill was brown for both Series III & IV but black was optional along with black or creme pedestals. Series IV was pretty much the same. The E.Q.'s now introduced Bose's Room And Source Compensation Controls. These sliding controls for bass and treble had indented stops for smooth operation. The E.Q.'s walnut wood cover remained.

Series III & IV E.Q.'s are meant to replace the tone controls on your amplifier while all other series E.Q.'s are designed to work with your amp's tone controls. In other words...When using either Series III or IV...set your amp's bass and treble controls to their flat or twelve o'clock position. Then work the low and high frequency controls of the 901 E.Q.

Series IV speakers have a third terminal on the bottom for use with Bose's "Spatial Control Receiver" which offered the 901 Series IV owner complete control over the amount of reflected energy via a slider control on the receiver's panel. The Bose "Spatial Control Receiver" also boasted a solid 100 watts p/ch rms and a built-in 901 Series IV EQ.

Bose also offered a lower cost 40 watt p/ch model 550 receiver which also sported a built-in 901 Series IV EQ but was minus the "spatial control" feature of its larger more expensive brother.

Both receivers were modestly priced and were available from 1979 to 1982. Although the two receivers could be used with other non 901 speakers via a switch on the rear panel for "901/Other" ...their best performance was with the 901's. These receivers are of course compatible with Series III 901's also!

Series V sported brushed aluminum side panels and a new E.Q. with smaller slider controls housed in a two tone brushed aluminum cabinet. Black grills are the norm but optional brown grills are available. Series VI is similar but sports partial wooden side panels and a black E.Q. Light brown grills with light walnut cabinets are introduced but black cabinets and grills would later be offered.

Bose offered a "Classic" and "Signature" model during the early days of Series VI. Creme and black pedestals are now offered for all models.

On The Inside:

The nine 4 1/2" drivers differ between Series II and later models. The first two series have heavy magnets and a four bolt basket with h.d. voice coils. Series III and up offer a three bolt design with helical voice coils. Do not replace a Series I or II driver with a Series III through VI driver. Foam surrounds are used on Series III through VI while cloth surrounds are used on Series I & II.


All Bose 901 speakers and e.q.'s are clearly marked with their series number on both the e.q. and speaker's bottom cutaway speaker terminals except for Series I which simply is marked as "Bose 901 Direct/Reflecting loudspeaker." Series I & II were sold as LEFT and RIGHT mirror imaged pairs and their E.Q.'s are very similar except Series II is marked as such while Series I simply states "Bose 901 Active Equalizer".

All Bose 901 speakers have the Bose logo on their grills except for Series I.

Also, certain Series I & II models may have handles and the Bose logo written in black right on the front grill. These were loaner pairs that Bose authorized its dealers to carry allowing for in home auditioning of the loudspeaker.

Keep in mind that Series I & II are considerably less efficient than Series III thru VI. Amplifier clipping should be avoided and one must choose an appropriate amp for each series.

Well...I've given you the details of each series of 901 loudspeaker so there should be nothing else to beware of...right? Wrong!!!!

Enter The Imposter!

In the early 1970's, a speaker company known as Linear Design Labs designed a speaker system that was identical to the 901. It was named The LDL 749 Direct/Reflecting speaker but offered no E.Q. One could buy a pair of these for less than half the Bose's price! But not having an appropriate E.Q. caused the speaker to have limited performance.

The drivers on the LDL 749 were laminated and each speaker had its front driver mounted in the center of the cabinet whereas Bose had the driver on the lefthand front of the Left speaker and toward the right on the righthand speaker. On later models Bose would eventually adapt the front and center approach of LDL.

All LDL 749's were sold with black grills and the cabinets had sharp corners. The fronts resembled the original 901 Series I & II models with the "straight" design. In other words...these speakers DID NOT sport the curved front look that later series 901 models have.

What If My Used 901's Have Rotted Surrounds?

First of all...It is a wonderful testimonial to the 901 speaker that these speakers are still around this long to even have this condition! If a seller is offering a pair of 901's with rotted surrounds and informs the potential buyer of the condition...then the seller is probably quite honest and this should not deter one from making the purchase.

As a matter of fact...for under $50 there is a great repair kit offered from an outfit known as Simply Speakers that easily and effectively brings the 901's up to snuff. Simply Speakers sells on Ebay.

"Kits include: 18 brand new-fresh stock surrounds (special m-roll Bose 901 design), special adhesive (not white glue), illustrated instructions, and technical support."

Although I do not consider myself to be the sharpest knife in the drawer, I have personally experienced great success with this kit and it is a wonderful opportunity for father and son to bond as they say! Just give yourself a good portion of a day to complete the project. You don't want to rush it and taking your time to do it right will render first rate results!

Remember that once you perform the surgery...regular "break-in" rules apply in order to properly seat the drivers. This kit goes a long way toward restoring your 901's to brand new condition.

There is one other point I would like to make while on the subject of foam surrounds. Folks with good intentions sometimes feel that by upgrading from foam to rubber or cloth that they will windup with a superior speaker to the original...and quite often end up disappointed with the results.

Series I and II used cloth surrounds...therefore...that is precisely what you should replace them with if need be. Series III through VI uses foam surrounds. Again...buy the foam kits for these speakers so as not to change the excursion characteristics of the original driver.


I hope I have cleared up some common confusion about the Bose 901 speaker system and its various forms that it has been presented in over the years.

Again, it is my wish only to aid those who are really thinking about making a "used" 901 purchase. With a bit of knowledge and an intelligent approach, one can truly end up with first rate performance...regardless of the model series! Here is one more item that may help your perspective 901 purchase...

Bose 901 Chronology:

Series I...1968 - 1973 Type = Acoustic Suspension...$476
Series II...1973 - 1976 Type = Acoustic Suspension...$525
Series III...1976 - 1978 Type = Acoustic Matrix...$625
Series IV...1978 - 1983 Type = Acoustic Matrix...$740-$900
Series V...1983 - 1988 Type = Acoustic Matrix...$900-$1100
Series VI...1988 - Present Day Type = Acoustic Matrix...$1100-$1398
All original prices are per pair including e.q.

Please read this alarming report on the Bose 901

Please checkout these other reviews on Bose 901's:

"My Reference Standard...For The Right Room!"
"The Art Of Bose Bashing"

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