Psuedo Bose 901's

[dynaco_dan]

Hi there;

I was wondering, what if, again.

What if KLH had experimented with the 4" - KLH model 12.5 full-range/mid-range driver in a Bose 901 speaker array? MMMM

This driver was used in a number of KLH radios, small portable systems, and as well as mid-range drivers for the KLH Five and Twelve.

Might be an interesting experiment.

Just need 18 drivers now.

[Andy]

Hi there;

I was wondering, what if, again.

What if KLH had experimented with the 4" - KLH model 12.5 full-range/mid-range driver in a Bose 901 speaker array? MMMM

This driver was used in a number of KLH radios, small portable systems, and as well as mid-range drivers for the KLH Five and Twelve.

Might be an interesting experiment.

Just need 18 drivers now.

Yes, these little drivers could make for some interesting projects. It's too bad the prices of the models 14,15,19 which have the 4" driver have gone up in recent years, pairs used to go for $10. - $20. and today it's $30. to $ 50. sometimes even more !

I want to restore a 1952 Baruch-Lang corner speaker made by Kloss Industries by using four of the 4" drivers (they're a perfect fit and would be staying true to Kloss)

Andy

[dynaco_dan]

Yes, these little drivers could make for some interesting projects. It's too bad the prices of the models 14,15,19 which have the 4" driver have gone up in recent years, pairs used to go for $10. - $20. and today it's $30. to $ 50. sometimes even more !

I want to restore a 1952 Baruch-Lang corner speaker made by Kloss Industries by using four of the 4" drivers (they're a perfect fit and would be staying true to Kloss)

Andy

Hi Andy;

Would it be possible to post some photos of those special Henry Kloss speakers, please?

[JKent]

Andy,

Sounds like an interesting project. I read somewhere (maybe you wrote it) that H Kloss was sort of doing "piece work" for Baruch-Lang when he was a college student, cobbling together the speaker enclosures, so he was not part of the design team. Looking forward to pics and a write-up!

Vern,

I remember seeing a web page devoted to buiding speaker systems based on multiple full-range drivers. Some were extremely ambitious towers with dozens of drivers! Can't seem to locate it now. Should have bookmarked it.

cheers

Kent

[soundminded]

Hi there;

I was wondering, what if, again.

What if KLH had experimented with the 4" - KLH model 12.5 full-range/mid-range driver in a Bose 901 speaker array? MMMM

This driver was used in a number of KLH radios, small portable systems, and as well as mid-range drivers for the KLH Five and Twelve.

Might be an interesting experiment.

Just need 18 drivers now.

I am very familiar with the original Bose 901 design using CTS drivers. I'm not that familiar with the 4" (or was it 5") KLH driver. IMO, the results would not likely have been any better, at best it would have been a tradeoff making a slight improvement in one area (possibly treble) with a corresponding loss elsewhere (probably in bass) but not that much difference overall. In all likelihood though, the results would just have been poorer.

The Bose 901 was a unique concept, very innovative in many ways and to this day unparalleled in certain aspects. Unfortunately overall, it is a failed design. I've written extensively about it elsewhere on this site and others and here are my thoughts. The original 901 was an acoustic suspension design incorporating 9 4" drivers, four each on two angled back panels and one facing forward in a pentagonal cabinet around 1 cubic foot. It's integral equalizer is a high precision device and the speaker makes no sense without it. The drivers are full range 30 watts and there is no crossover network. The speaker is one of the only ones, maybe the only one to be intentionally designed to be carefully integrated in the listening rooms acoustics deliberately taking advantage of the room's reflective surfaces. (AR9's woofers are another.) However, because it has no means to effectively compensate for them, at best successful integration into the room is hit or miss. The speaker has at least three fatal flaws. First it has a bass peak of around 7 db at around 250 hz. The small cabinet deliberately moved the system resonance frequency up because Dr. Bose contended that the phase shift associated with resonance is inaudible above 180 hz but he did not damp out the FR peak. This was reported in ee magazine's review and I have experienced it myself. Contrary to what ee said, it is very audible. Also, the 6db per octave boost to the bass is not adequate to flatten the bass response to compensate for its 12 db per octave falloff unless additional equalization is provided. This makes power requirements enormous, in the 600 to 1000 wpc range to equal the 1 watt output at 1 khz but the system can only handle 270 so multiple units are required even for relatively small rooms. Because the original and Series II are widely available at under $200 and the cloth surrounds did not deteriorate, this is feasible as are very high powered amplifiers at reasonable prices today. This was not true in the mid to late 1960s when the speaker was marketed. It is not likely that the KLH 4" driver can match the output of the 901 drivers. When properly equalized, the speaker can respond to 23 hz with 10% THD so it gives the AR1 a run for its money, one of the few speakers until recently ever to do so. But the 901s real failing and likely the same failing of the 4" KLH driver is that its inertial mass is too great to make it an effective tweeter, its output in the top octave is very low no matter how much power you pump into it. Today it would be called a midwoofer. For those who still have hearing above 10 khz, this makes the 901 and all other single driver full range speakers inadequate. But even if it could respond above 10 khz, its dispersion due to its large diameter would be nil, all its output being mainly on axis. Since the front driver is used to create the first arrival directional aspects of music and because high frequencies play a major role in hearing directionality, this is a fatal flaw. In correcting this problem, it was practical to turn the speaker into a two way bi-amplified design with the ability to not only adjust the level of the tweeters but the ratio of direct to reflected sound and the relative FR of the front and rear tweeters. When properly adjusted for the room acoustics and then further adjusted for variations in program source, the result is a very high accuracy full range system with all of the advantages the direct reflecting principle offers. (After figuring out what was wrong with it, it took me about 2 1/2 years to fix it to my satisfaction.)

[dynaco_dan]

Hi there;

I have only come across one homeowner that owned a pair of Bose 901's.

They were sitting on the carpeted floor at each end of a chesterfield.

Needless to say. the owner obviously did not read any installation material or worse even also had a tin ear. LOL

There was a pair suspended from a local, No. 5 Orange Street pub's ceiling, here in Vancouver, with the "V", facing towards the open area.

I mentioned to the manger that the V should face the wall.

There was no return visit to see whether they did or not.

I did hear the Bose 901's a few times at our old Kelly Deyong Sound Center here as well.

They were give the premier sitting position compared to other speaker systems.

Whatever music I heard, it sounded big, bigger than any other speaker system.

I wouldn't have minded a pair but the room need's for space was more than I had or was willing to share with.

With their metal stands they did look mighty fine in deed.

I am referring to version 1 only and the only version I would have even considerd with the later foam problems.

[soundminded]

Hi there;

I have only come across one homeowner that owned a pair of Bose 901's.

They were sitting on the carpeted floor at each end of a chesterfield.

Needless to say. the owner obviously did not read any installation material or worse even also had a tin ear. LOL

There was a pair suspended from a local, No. 5 Orange Street pub's ceiling, here in Vancouver, with the "V", facing towards the open area.

I mentioned to the manger that the V should face the wall.

There was no return visit to see whether they did or not.

I did hear the Bose 901's a few times at our old Kelly Deyong Sound Center here as well.

They were give the premier sitting position compared to other speaker systems.

Whatever music I heard, it sounded big, bigger than any other speaker system.

I wouldn't have minded a pair but the room need's for space was more than I had or was willing to share with.

With their metal stands they did look mighty fine in deed.

I am referring to version 1 only and the only version I would have even considerd with the later foam problems.

Many 901 systems were probably not properly installed. But even when they were, the system had a rolled off high end not all that different from many other speakers of that era, an upper bass peak, and the lowest frequencies could often have used some additional boost. Graphic equalizers were not available to the average consumer in those days and they were very expensive ($900 a channel for the 1/3 octave Altec Acoustavoice) and therefore reserved for recording studios. Often using the bass control to bring the lowest bass notes into proper proportion further exaggerated the upper bass peak. People therefore tended to play them very loud but when there was bass, it could overtax most amplifiers unless the "below 40 hz" cut switch was engaged. This dropped low bass by an additional 10 db. On loud deep organ pedal notes and other loud bass, the speaker clearly showed its capabilities when suitably installed and sufficient amplifier power was available. What is today called "imagaing" was unique, not only did musical instruments appear to be spread out across an entire wall of a room and there being far less tendency for a "hole in the middle, but the music did not appear to be coming from the boxes themselves but from a space behind them even beyond the wall. I think this one characteristic was what sold so many customers on them. They also had far less tendency to compression distortion because most of the time, the drivers were only operated at a very small fraction of their capacity. The major problems for audiophiles as I see it is that the combination of little high frequency capability and an upper bass peak creates a combination they will not accept, it's the antithesis of the timbral characteristic of many of todays thin shrill sounding speakers they like. Dr. Bose himself said in his whilte paper that he started out by buying loudspeakers on specification alone and found that the more he paid the more shrill they sounded.

BTW, the differences between the original and series II is that a computer was used in series II to sort the CTS drivers into three categories so that only those which matched most closely would be used in the same cabinet. (this was done either by hand or not at all in the original.) Also the equalizer's 10 equalization countours had more of them skewed to a treble boost than the original. A small metal Bose logo was attached to the grill cloth as well.

By series III, the execution changed radically even though the basic design concept remained the same. Bose made his own drivers and the system was designed as a ported system, Bose calling his ports "reactive air columns." This cost the system the ability to reproduce the lowest audible octave but gained efficiency. By series IV, he used and injection molded plastic enclosure instead of wood. Prices rose drastically too. In the overall cost of a sound system, this shifted the lions share of the profits away from the amplifier manufacturer to the speaker manufacturer, a clever commercial move. It also made it clear Bose was not targeting the high end sector of the speaker market anymore. Many audiophiles irrationally resent his remarkable commercial success. Bose 901 is still available today in a series VI but only on special order. Bose Corporation has over a billion dollars a year in sales volume and is still privately owned, a fact that should make even Sidney Harman jealous.

[Guest Jethro]

Great post Soundminded

I wonder why Consumer Reports selecter the Bose 901 Series IV as the best floor standing speaker for 2007??? Guess that EQ does quite a bit to compensate for the design. Still dont know how they get the high end out of the box. Wonder what the testing criteria was. Anybody have insight?