May. 12, 2016

Conn Speaker Pipes

Conn electronic speaker pipes, first developed and patented around 1959 by Conn Keyboards, the piano/organ division of C.G. Conn Ltd., were rather heavily marketed through the next decade during the heyday of the home organ.  This invention was just one of a number of attempts to improve the early analog electronic instruments of the time by spreading and diffusing the sound for increased realism.  Other solutions that worked in different ways included a) Donald Leslie's two-speed (fast/slow) Leslie-Rotosonic speaker first created for the Hammond organ, b) the Allen Company's rotating variable speed Gyrophonic projector speakers, and d) the Compton Company's one-speed (slow) Rotofon speaker system used with its Electrone organs.  Kimball International acquired Conn Keyboards in 1980 after the bottom fell out of the home organ market and sales through the 1970's were stuck in a downward swing -- a business move which, in the end, turned out to be non-profitable.

The Conn pipe units were external add-on faux pipe SPEAKERS which were well-received technology back in the day and a rather hot item at the time for Conn organ dealers to keep in stock.  During the 1960's they were almost always on back order, and it was challenging for stores to even keep any display models on the floor.  Many thousand sets were manufactured during those years and shipped all across North America and the English-speaking world.  Thanks to that, enough of them still survive in original working condition for determined hobbyists to systematically hunt down over time, clean and repair where needed, reassemble, and treasure.
This invention was in principle an acoustic system which amplified sound waves whose frequencies matched one of its own frequencies of vibration, thus producing resonance related to the size and positioning of the pipes.  The degree to which the bottom of each pipe occluded the surface of the driver generating its excitation had much to do with determining its length and diameter for tuning purposes.  Since any cylinder resonates at multiple frequencies, producing multiple musical pitches, the tuned pipe tubes, being open on both ends, picked out overtones [harmonics] as well as their own fundamental resonance frequencies from the wideband sound excitation generated by the speakers inside the pipe box, which acted like motors.

Conn engineers designed these units as a vertical array of cylindrical anodized aluminum tubes of differing lengths and scaled diameters finished in either silver or gold and tuned to resonate with the frequencies of the 12-tone equal-tempered musical scale adopted in western countries.  These were mounted vertically in single or double rows on a wooden baffle sitting atop a rectangular wooden chest made of walnut inside of which either one or two pair of 6" x 9" Cletron midrange oval speakers made by Cleveland were lined up and wired together.  Each elliptical-shaped speaker was positioned under a plurality of pipes, screwed tightly to the underside of the baffle, and projected sound waves upward against it.  The baffle in turn cushioned the sound as individual frequencies from held notes found their own pipes and caused them to resonate.  The speakers were mounted end to end, and when 4 speakers were used in models 145 and 146 these were divided into pairs and series parallel wired.

NOTE:  Wiring two of the speakers in series has the (-) side of speaker A connected to the (+) side of speaker B, and the same thing with speakers C and D, respectively.  These two pair [AB & CD] were then wired in parallel by connecting the (+) side of speaker A to the (+) side of speaker C, and the (-) side of speaker B to the (-) side of speaker D.  Series parallel wiring is how the Conn engineers maintained a consistent 8 Ohm load using four 8-Ohm speakers in the same box.

These units had no woofers, no tweeters, no crossovers, no additional circuitry.  Individual frequencies coming from the speakers simply found their own pipes.  Any acoustically resonant object will "pick out" its resonance frequency from a complex excitation and, in effect, it will filter out all frequencies other than its resonance.  The pipes therefore did all of the frequency selection.  The sound escaping vertically from the top of each pipe created a three-dimensional sourcing and enhancement of overtones which added a certain something to the Conn organ pulse channel voices [diapasons, strings, reeds] coming from the amplifier.  A very rapid but measurable delay in the buildup and decay of sounds tending to soften their attack and release also was noted by Conn engineers.

CAUTION NO. 1:  THESE ARE STRICTLY TREBLE UNITS THAT CANNOT BE PUSHED AT DANGEROUSLY LOW FREQUENCIES.  For this invention to operate safely in any application it needs to be shielded from ALL sub-bass and bass frequencies arriving at the pipe boxes from about the middle of the 8-foot tenor octave, corresponding to the tenor F# note [185Hz], on down.  The signal may be stripped of unwanted bass in two ways:  1) by connecting a powered subwoofer equipped with built-in 200Hz crossover between the console's output jacks and pipe boxes ... or 2) by reducing bass amplitude generally by turning down the amplifier's bass control.  If the sub comes equipped with a variable crossover knob it should be set at maximum [200Hz where possible, no lower than 180Hz], no exceptions.

NOTE:  The bass sound spectrum begins around the 8-foot middle C note at 250Hz and extends downward.  The original drivers in the 146s were designed to play only down to around 200Hz, which roughly corresponds to the 8-foot tenor G# note [208Hz].  On one reference thread, an owner reported putting 300W from an amp into a pair of left and right model 146 pipes using the original drivers with a 150Hz high pass filter engaged and getting away with it to where they were "working great."  This crossover [150Hz] however is too low to recommend itself generally, as it subjects the original drivers to bass frequencies all the way down to the tenor D note [147Hz] half an octave away from the lowest tuned pipe of the 146s.

Conn speaker pipes came in 3 models

and 7 different types or styles:

1. Model 144 "mini-pipes", type 2, Right elevation [determined by tallest pipe in back row], one pair of 6" X 9" oval 8 Ohm speakers wired in series, 16 Ohm load, 28 pipes in 2 rows of 14 each.
Model 144, type 3, same, with Left elevation [determined by tallest pipe in back row].
DImensions: 21.5" Wide, 8.25" Deep, 29-7/8" High, Wt. 17.5 lbs.

2. Model 145 type 1, Center elevation, two pair of 6" X 9" oval 8 Ohm speakers wired in series parallel, 8 Ohm load, 49 pipes in 2 rows, 28 front, 21 behind.
Model 145, type 2, same but with 48 pipes in 2 rows, with Right elevation.
Model 145, type 3, same with 48 pipes in 2 rows, with Left elevation.
Diimensions: 42.5" Wide, 8.25" Deep, 34" High, Wt. 18 lbs.

3. Model 146 type 2 , Right elevation, two pair of 6" X 9" oval 8 Ohm speakers wired in series parallel, 8 Ohm load, 12 pipes in single row.
Model 146, type 3, same, with Left elevation.
Dimensions: 42.5" Wide, 8.25" Deep, 63.5" High, Wt. 40 lbs.

The 6" x 9" oval speakers Conn used in these units each had an impedance of 8 Ohms, thus they were series parallel wired in order to produce a combined load on the amp of 8 Ohms for the entire box.

NOTE:  The 144s were brought out by the Conn factory as a space and cost savings result for pipe customers.  They had just 2 speakers inside wired in series for a combined load of 16 Ohms for each box.  The frequency range of this model however was narrow due to having only 28 pipes.  One set of 145s would outperform them.
Since the 8-foot tenor G# note vibrates at a frequency of 208Hz, this note was the practical downward limit of the 146s.  The upward limit of the 146s was the note 11 semitones higher at middle G [392Hz].  The 145s were tuned to everything above that and carried all the way to the top of the manual compass.
NOTE:  Both types (right and left elevation) of the 146s were constructed with cosmetic notches about a quarter of the way up the length of each pipe, all on the same side, merely to enhance the visual perspective by simulating the appearance of the labial mouths of cylindrical open metal organ pipes.  We all know what happens to an open cylindrical metal organ pipe when a hole is made in its side -- it raises the resonant frequency of the pipe depending upon where the hole is placed.  Some owners therefore have elected to cover these notches with tape thinking that the Conn pipes behave just like real pneumatic-driven organ pipes when such is not the case.
In terms of volume output these units are naturally a bit inefficient compared with the power needed to run them, but volume is not what they were built to do.  The only place in the 145s from which the sound from the speakers emerges is from the top of the pipes, their frequency range is limited, and by turning up treble and volume controls for any other external amps and speakers used with them the subtle effects they produce end up being swamped.

When Conn engineers tested this invention the pipe tubes, as expected for cylinders open on both ends, resonated not only at the fundamental primes to which they were tuned but also at multiple overtones.  They conducted a demonstration of this where a small microphone was dropped inside given pipes.  This microphone was connected to a regular guitar amp, and they used a set of 145s labeled as to their tuned pitch.  While first holding down middle "C" on the organ the microphone would be lowered into ANY shorter "C" pipe, and a "C" was heard coming from the guitar amp.  Then, while still holding middle "C", the microphone would be lowered into a "G" pipe, and one would hear a "G" coming from the amp.  Likewise when lowered into an "E" pipe, an "E" would be heard coming from the amp.  They also discovered a very tiny but measurable bit of reverb vibration within the walls of the pipes after notes were released.  
Conn engineers also found that when the speakers were energized by held notes from the organ, the column of air in each pipe had to be put in motion before the sound could escape, resulting in the volume building up before the tone blossomed out the top of the pipes in all directions.  Besides discovering overtones of fundamentals resonating within the pipes they also found that when keys were released the column of air within the pipes would not come to rest immediately but would permit the tone to linger for a very minute split of a second before dying away completely -- something which can be heard along with all the other sonic effects but not counted.

The aluminum pipes used in the 145s are of 10 different diameters, and the largest pipes used in the 146s are of 5 diameters.  With speakers removed a near perfect scale is heard when the pipe sets are laid on their side and the bottom opening of the pipes is tapped lightly with a hammer from the longest to the shortest.  A little "ping" tone is heard as each pipe resonates.  The pipe boxes do play a few dBs more softly than ordinary speaker cabinets driven by the same amp with the same output level, but the reason why the pipe boxes are somewhat inefficient as speakers go is mainly due to the constriction of the tone by the relatively small outlet for the tone each box provides.   

Theoretically these pipe units can be connected to play through ANY make or model of electronic organ -- analog, solid state, or digital -- and they can sit either upright or be placed horizontally, if desired, like real horizontal trumpet organ pipes, the weight of the speaker boxes and their frame bracing making them stable enough to make this possible.  Each unit receives a single mono channel of audio and is designed to connect with the amp driving them using standard 16-gauge speaker wire right off the spool.  These bare wire connections are made more secure by stripping the speaker wire at its ends, attaching 1/8" spade connectors using a crimping tool, and tightening the screw terminals under each pipe box to the spade connectors.

CAUTION NO. 2:  The walnut speaker box is fairly sturdy but not waterproof or indestructible.  NEVER expose these units to water, excessive dampness, or give them rough treatment.

CAUTION NO. 3:  NEVER EVER, REPEAT NEVER ATTEMPT TO ALTER THESE UNITS IRREVERSIBLY FROM FACTORY DESIGN, such as by trying to shift wire connections from the bottom of the speaker box to the side, which would involve cutting wires loose from the screw terminals, drilling a new hole somewhere in the side, rerouting the internal parallel speaker wiring to the outside through that hole, and then resoldering and/or making a wire splice to reestablish connections ... all guaranteed to create a potential weak link in the incoming signal stream, render the external wiring more difficult to protect and hide, and allowing some of the escaping sound to muffle the effects of the pipes, not to mention defacing the unit's esthetic appearance and destroying its resale value.

ONE MORE THING:  On all models and types of Conn pipes the pair of screw terminals where the speaker wires connect are UNDERNEATH the box out of sight and project about 1/8 inch below the bottom surface.  To protect from damage and to keep the unit stable when it sits on a wood floor or other hard surface the bottom four corners of each box are supplied with a rubber foot 1/4-inch tall set about 8 inches in from each end.  If the box happens to sit upon a carpeted surface the entire weight of the unit gets compressed on these four small feet causing the unit to sink completely into the carpet with its bottom, screw terminals and all, missing any freeway space.  If the unit is to be moved it should be picked straight up bodily and set straight down.  NEVER EVER, REPEAT NEVER, when moving these units around the room, slide them on a carpeted surface, as this can bend the spade connectors and likely break one or both wire connections.  When it appears that the unit doesn't appear to be working, a loose connection on these bare wire terminals arising from sliding the unit on the carpet is often the cause.
Hooking up these pipe units to any electronic organ presents a consideration of critical importance called impedance, which is the resistance offered by the circuit to the transmission of an electrical current.  Every amplifier connected to a speaker system is rated for a minimum impedance load (in Ohms).  In Conn organs one or two sets of these pipes typically were hooked up only to the main pulse channel [diapasons/strings/reeds] and were powered by the console's internal amplifier.
NOTE:  When 2 resistances (impedances) are connected in series, they total.  For example, a pair of 4 Ohm speakers wired in series results in an 8 Ohm load to the amp (4 + 4 = 8 Ohms).  When 2 resistances are paralleled however, a formula comes into play for calculating the impedance.  The total impedance in parallel is the multiplication of the two loads divided by the sum of the two loads.  For example, a pair of 8 Ohm speakers wired in parallel results in a 4 Ohm load to the amp (8 x 8 = 64, divided by 8 + 8 = 16, which is 64/16 = 4 Ohms).  It's the same result as totaling the loads in reciprocal, whereby 1/8 + 1/8 = 2/8 = 1/4, in reciprocal = 4 Ohms.

Since the minimum impedance rating of most amps is 4 Ohms, it's plain to see that connecting several of these 8 Ohm speaker pipe units in parallel can make the amp work harder, and, if the circuit's impedance is below the amp's minimum Ohm rating, the amp and its internal wiring will heat up quickly and could end up fried.  How the speakers are wired therefore makes all the difference in whether or not the amp driving them will continue to operate.
According to Ohm's Law, in an electrical circuit the voltage (V) in watts is the product of the current (I) in amps and the impedance, or resistance (R) in Ohms.  Thus V = IR, and, since the incoming voltage at the wall receptacle is constant, whenever speaker units are wired parallel with a reduction in impedance the current in the circuit increases.  This, as stated, makes the amp run hotter than it's supposed to.
Original Conn vacuum tube amplifiers, being out of production for a great many years now, are impossible to replace these days [unless cannibalized from another old Conn organ].  The solid state amps which came later were not quite as particular about impedance as tube amps were, but they were all rated for a minimum 4 Ohm load.  As speakers are daisy-chained in parallel to one another the Ohm load always drops, so, it's never a good idea to try to run a load below that.  Again, with an unchanging voltage arriving from the electrical wall socket, low Ohms in the circuit translates into more current, thus, the lower the Ohm load, the hotter the amp will run.  If the equipment has protection circuitry and heat becomes a problem, the amp may shut off at heavy volumes, but the result is still the same:  no sound.     
Over long periods of time house dust, pet hair, and even dead insects and other debris falling into the tops of these pipes tends to accumulate on the upward facing speaker cones.  It's advisable whenever these pre-owned units are first obtained to take them apart, clean and vacuum the speaker faces, and check them prior to hook-up.  The original pipe finish may be restored using a tube of metallic gold leaf or metallic silver leaf Rub 'n Buff available from craft retailers and applied with a cotton ball.  Unwanted finish that happens to get on the speaker box is easily removed using mineral spirits and paper towels.
The usual choice for replacement of the original Cletron speakers, if needed, is new 6" x 9" oval car audio speakers.  If 8 Ohm replacements are used, which are easily available, then the original Conn series-parallel wiring can and should be retained ... BUT, if replacement speakers rated below 8 Ohms are substituted with no change in wiring, the resistance the whole pipe box presents to the amp drops drastically.  For example, if 4 Ohm replacements are parallel wired [4 x 4 = 16, divided by 4 + 4 = 8, which is 16/8 = 2 Ohms], it would have the amp operating well below its minimum impedance rating and heating up, which, as stated, will fry the amp unless the wiring is also changed.  All that new rewiring work can be avoided simply by using replacements rated at 8 Ohms.

NOTE:  Hobbyists who love exploring new sonic realms have sometimes constructed their own one-of-a-kind speaker pipe units which mimic the Conn design and employ the same acoustical principles.  These creations work best when they're on their own separate amp, but the cost of aluminum tubing is expensive these days, and trying to build replications would be difficult at best because not only do the tubes graduate in length but also in diameter.  The length and diameter of such pipes would need to be in happy agreement to resonate at frequencies related to the A-440 tuned, equal tempered scale in order to integrate with any Conn pipes used with them.  One hobbyist constructed with satisfactory results a sturdy, square-shaped wooden box inside of which was mounted a single upward-firing 12" Radio Shack woofer which projected sound through a large, circular opening and wire screen baffle to the entire plurality of pipes mounted above it.  Above this baffle was positioned on-end 12 thin-walled polyvinyl chloride [PVC] pipes each of 3-1/4" diameter cut to varying lengths to resonate with the 12 chromatic semitones between 8-foot bass Bb and tenor A.  The pipes were grouped on end over the baffle into a tight round bundle, remained open on both ends, and were painted a metallic gold color to match.  When all such pipes are of the same diameter their positions over the speaker cone has much to do with their lengths because the air inside them vibrates at different velocities depending upon how much sound each of them receives.  Those clustered over the center of the woofer receive the most sound while those situated at its perimeter occlude only a portion of it -- which explains why two different pipes of identical diameter in such a unit tuned to resonate at neighboring chromatic semitone pitches could be very close in length.  Custom built, one-of-a-kind units like this usually stand something over 7 feet high and are made to slightly overlap the tuning of the bottom two semitones [tenor A and G#] of the 146 Conn pipes in order to continue the chromatic scale downward 12 more semitones from 8-foot tenor A [220Hz] down to bass Bb [117 Hz] with no audible break.  What's important to understand about how this invention disperses sound within the room, the gradual buildup and gradual decay of sound associated with it, and its efficiency compared with the power needed to run it, is that its effects are most noticeable up close.  Strings, reeds, and mixtures take on a noticeable sparkle, and the sound gets dispersed in non-directional ways throughout the room to where it seems to come from every corner, adding to the quality and ambience of what the listener gets to hear.
The general attitude of those with only a cursory knowledge of or experience with these units is that they're merely aesthetic visual enhancements, a reference only to the sight perspective, not their measurable audio effects.  This bias largely accounts for the wide sway of opinion the public has of them.  Pricing of these pipe sets today also seems to be all over the place.  Because of their scarcity they tend to be overvalued by sellers (a single set of 145s center elevation, for example, was sold finally on Reverb for $975 + $150 shipping, total cost $1,125 dollars).  Much depends on their condition.  Presuming they're undamaged, unaltered from factory design, and in immaculate working condition, most buyers would probably be willing to pay up to $125 a set.

This invention DOES give a life to electronic organ sound that would not be as exciting or beautiful without it.  While their original Cletron drivers don't take any bass as stock, some hobbyists have replaced them with car audio 6" x 9" units that can handle more power and a wider frequency range, all with good results.

Part of the reason certain owners fail to be impressed with it is that they test it by swamping it in an avalanche of other loudspeaker sound with high treble boost.  The signal stream being sent to the pipes from the amp is best kept FLAT with the treble of all other speakers turned down a bit to allow the effects generated by the pipes to be heard.  It's easy to be fooled when the pipes are tested against ordinary speakers pushed to the limits like this and nothing more seems to be reaching the ear.  Informed musicians from all over would not be spending in some cases hundreds of hours, traveling hundreds of miles, and investing their hard-earned money plus a good deal of time, attention, and elbow grease searching to locate, obtain, hook up, and test these units if all they did was look pretty.

The fact that they actually produce and resonate sound can be easily tested.  If one takes a pencil and puts it in the keyboard to hold down just one note and then puts a hand over each individual Conn pipe, one finds that air DOES NOT pass through all of them.  Only one pipe will be found through which the air is moving [a little air also might be found coming out of a pipe half that length, as expected for the octave overtone, typically the strongest].  If one then places the hand over the top of that pipe to totally stop the air from coming out and slowly lifts it, one discovers that the pitch can be bent.  This sort of experiment proves that these pipes do more than just let sound waves pass through them or be decorative.   

NOTE:  From a technical point of view, Conn pipes are a bit "lo-fi" in the sense that they have considerable roll-off in the high frequency range.  This would account for the "sweeter" sound of mixtures and strings when heard through them.  In practice the sound of hi-fi speakers can be too bright and thus harsh, especially in a small or dry room where the speaker sound makes its way to the ears with less reflection than it does in a big, lively room.  The true genius of this invention lies in several characteristics however, all of which accrue:  1) as stated, the pipes direct the sound upward instead of straight out -- this characteristic alone is well worth the effort, as it makes the sound seem less "electronic" in the sense of coming from speakers, 2) the tones emanate from a great many sources, each one dispersing the tone in a slightly different way -- this adds immensely to the sense of spaciousness and completes the illusion of the sound coming from somewhere besides a speaker, 3) the constriction of the speaker output very likely results in a smoothing of the response curve of those otherwise unremarkable 6" x 9" oval speakers -- under normal conditions there would be a midrange peak, but forcing the tone out the pipes moves the resonance upward to a part of the frequency spectrum [probably several thousand Hz] otherwise not normally represented in ordinary speakers which gives all tones a subtle, signature sparkle making the sound more appealing, and 4) the pipes also damp and muffle the frequency response above a certain point, so the clicks, pops, harshness, and any other undesirable characteristics of electronic organ speaker tone are minimized.   

A few hobbyists these days who couldn't be more indifferent about the visual perspective or even the electronic organ in the first place have employed these units as a secret weapon in other audio applications including electric guitars and even home stereo systems -- bass and drums filtered out -- with impressive results [a set of Conn pipes can be run on a guitar or other amplifier as small as 20 watts, but it's generally best to use a larger amp to avoid having to turn up the volume knob on a smaller amp to maximum].  This once forgotten musical accessory seems to have become a modern musical treat with organists and non-organists alike ... and, provided the necessary amplification is available, there appears to be NO LIMIT to the number of sets that can be connected to a single controlling signal source. 

BOTTOM LINE:  This invention works wonders.

If the user knows how to hook them up, shield them from unwanted bass, test them, adjust the treble and volume of other speakers around them,

and give them a fair hearing,

the satisfaction they're certain to bring

is not fake by any means ...

It's reality.