Allen TC-4 Project

[Larrytow]

The tweeters were likely removed from those cabinets by a home stereo enthusiast. I forgot the brand that Allen used, and the model number of them, but they are very desirable to people that are into vintage stereo stuff. When I sold my TC-4, the buyer did not want the big model 100 gyro cabinets, as they were going to use some other amplification for it. So I needed to sell the gyros apart from the organ, and a guy that runs a vintage stereo shop bought them from me. He wanted the tweeters, and of course the big tube amps. In fact he wanted just those components, but I told him he needed to take the cabinets too, and he did. I sure wish I could remember the details of those tweeters, but I'm having a senior moment about them.

My cabinets did not have any horns in them, so I have no idea what they were used for on yours.

Here is a link to my TC-4 being played. You will need to download it to hear it, as I don't think G Drive lets you just listen to stuff. I forgot exactly how I recorded this, but I think it was to a home stereo CD recorder, and then I ripped the CD to the computer. I made the file so I could send it to the potential buyer who was many states away. Quick and sloppy playing, but it does give some idea of what one sounds like with the Nanoverbs and everything.

https://drive.google.com/file/d/1lDx...ew?usp=sharing

I'm still looking though my photos on CDs and Flash drives to see if I have some of my TC-4. But I had that one a long time ago, so any photos I have might not be digital even ! And all those are packed away mostly.

I just searched vintage tweeters, and found the answer. They were Jensen RP-302 16 ohm tweeters. One is on the bay right now for 400.00 !

[Silken Path]

Good grief. We should be buying up Allen speakers... I'm listening to it now - Google drive just plays the file. (I suspect that you need to have signed up for drive, but signing up for anything, including gmail or the play store, should suffice).

16 ohm. I see that I'm going to have to get an education about impedance and the significance of all the crossed wires in the speakers. I suspect that I will need to uncross some of them. Probably not rocket science, but outside my experience so far. I take it that modern tweeters are not going to be 16 ohm... but, hmm, maybe I can wire two 8 ohms as if they were. Then the transformer used in the cross-over on that speaker with the horns would not need to be changed.

Larry, that's a NICE clear sound from the organ. I'm only going to be able to get the speakers about three to five feet away from the organ. So these amps are pretty quiet?

On edit: I see several Jensen HORNS on eBay that are tweeters, so that's not looking terrible. They're plastic and when I get to that, I'll ask somebody to measure the base.

More edit: The Jensen RP108 C7316 is a plastic horn with a 10" x 4.5" that fits the cutuout. It's described as a mid/tweeter. One seller says they are 12 ohms.

Now to find some tweeters. I need a bunch of them, but not $400 ones! :)

[toodles]

You might find that you would be much happier with used Allen HC-12 speakers than the old ones you have. The HC-12's will be smaller and have better performance for the 32 ft stop. These speakers were introduced with the digital organs of the late 1970's, early 1980's, when Allen found out that the speaker approach they had used for the Allen organs wasn't really ideal and put some real design work into their speaker systems.

An evolution in loudspeaker design occurred in the 1970's both in terms of matching cabinet size to drivers and making drivers that gave better performance. While the details are interesting, it is off-topic here, but the end result is that 1980's and later speakers will give better performance in a significantly smaller size than those of the 1950's and 1960's.

Those woofers in your cabinets will have a higher resonance than modern woofers/subwoofers, and the huge size of the cabinets was used to get useful bass performance from such drivers. That's why when you tap the cone it doesn't "thump."

Dispersion in any driver is excellent up to the point where the wavelength of the frequency is about equal to the driver diameter. For a 12 inch speaker, that means about up to 1,000 Hz. Above that frequency, the driver will "beam"--i.e., have a very narrow projection angle. In addition to limited dispersion, the woofers will have a fairly limited treble response. The tweeters will extend the frequency response to the mid-teens (in kHz) and provide dispersion so the sound is more even across the listening area. All the channels will need some form of tweeter as they all need decent response in the treble.

It is unlikely the original installation included what we now call a "subwoofer". Very low bass response was handled by multiple large diameter woofers in huge cabinets, which is what you have.

[Silken Path]

Toodles, you are wonderful at dispensing knowledge. I'd not be getting very far with this without you, Michael, Larry and others pitching in. Thank you, and thank you all.

Sir, I have sweat equity in these speakers now. I'm already planning and plotting to get them painted and put modern scrim cloth on them, as well as wheels on the bottom. I'm impressing MYSELF at these monsters, so I can't wait to pull them on unsuspecting visitors. However, I'll keep an eye out for newer speakers, too.

Here's some not-bad news. I snipped the tie-wraps and looked under the tape on the wire bundles and found some wire numbers and descriptions. They are like "1ST SHLF PWR" and "2ND SHLF L INP." So now I'm working on seeing how many I can find. The other ends of wires are labeled A to G, and I'm hopeful that if I very carefully dust the organ under there, I may find some markings to match.

This is exciting. I'm suddenly envisioning playing this organ in a month instead of in six months. We shall see!

Oh, and I have 550 sq. ft. in the room (garage) it's in now. I can add another 200 sq ft (adjacent office I'm sitting in now) by opening two doors and maybe cutting a window or two in the wall. I think these old monster speakers will be just fine for now, and a lot of bass just might make the joint fall in (on my head).

Haven't found any great 2 3/4" inch tweeters to try, but the speakers that I have 32 of are very common still and are used by guitarists in "cigar box" amplifiers. New ones can had for around $10.

[Larrytow]

If you are bound and determined to put tweeters in those cabinets (although Toodles gave you real good advice to get some HC Allen speakers, in my opinion), you should check out Parts Express for some. I just got a flyer from them stating that they recently bought out another company's inventory of drivers, and are having a sale. I have not looked though all of what they have, but there may be some suitable ones available.

[toodles]

Even though you have sweat equity in these old speakers, remember that the farther you travel on the wrong path, the farther you have to back track before finding the right path.

I'm not saying that these speakers will disappoint you but more modern speakers will likely do better, and even if they give the same performance, they will be smaller. The reason you don't find new behemoth speakers for sale these days is not just a matter of decor--a lot of research has gone into designing bass speaker systems and optimizing cabinet size and resulting performance. The old approach was just to make it big and, in many cases, hope for the best.

[myorgan]

Now to find some tweeters. I need a bunch of them, but not $400 ones! :)

Lamar,

I believe they were Peerless dome tweeters, or with (I think they call it) amphenol rings--they were an orangeish color around the dome. I found a pair of Peerless dome tweeters on *Bay a few years ago, and picked them up in case I needed to replace some that had been ruined by prying fingers.

I think I have to back up others, though. The HC-12 speakers will really rock the garage. You won't get the rotary effects, though, but it's a trade-off.

Michael

[crapwonk]

Don't be too fast about rewiring the big board with lots of speakers with the criss-cross wiring pattern. They are wired that way to maintain phasing (all pushing in and out together at the same time). Note that some speakers have terminals on the left and some on the right side. The cross wiring accommodates keeping all the + terminals tied together and all the - terminals tied together.

[Silken Path]

Hi, Toodles and Larry - Gotcha. I understand, gentlemen. I'm not AVERSE to having higher tech speakers, wonderful as they are. But these are what I got, and I want to HEAR them, even if they ARE unscientific and uncouth. I did have a suspicion that these speakers were more brute force than sophistication. :)

Do not see nary an HC-12 on eBay at the moment, but I'll keep watch. (I promise.)

Larry, thanks - I will check out Parts Express. (I was thinking I needed "Dayton" speakers. Right after I bought an expensive Crown amp, John (jBird) told me about a Dayton amp for about half the price.)

Cool, Michael. I think I DO want to go with modern tweeters. Fortunately, I only need a few of them here and there, and I may crank the system up before I get all of them. I also eventually want to have a headphone jack, but I read that the organ output is low signal + high impedance. Apparently it NEEDS these old amps.

And thanks for the note, Crapwonk. NO, I won't undo any of them. I do want to keep them original, but I have more to learn about this. For example, if the speakers end up being 8 ohm at their terminals, what circuit is needed to connect two of them to one amp? Do they just hook up in parallel?

Do I need to add crossovers to any of the speakers? (I see that some modern speakers have a cap on them to filter out low signal. Can these be used without a crossover?)

Toodles told me that the big drivers handled the bass, and I have three of them, counting the two in the gyro. I also have three channels. Let's see. I have three speakers that can handle higher tones: the two 16 (+ tweeters) and the one with Jensen horns. OK. That seems to answer that.

Each channel gets one bass speaker and one higher tone speaker. My inclination is that the speaker with four big ones, as well as one of the 16 mid-highs would go to diapasons. The rotary and the other 16+ go to flute. That leaves the unit with two big black speakers and the unit with the horns for the reeds. This can change, but that currently sounds like a plan.

OK - I found out about the tone strip. That's actually what it is. The stack is all the common connection points for all the stops and, on some Allens, maybe other things -- some of them may have 14V present, since that's what the magnets run on. One clue about this was on my first TC-4. It had a tag on one that said "Stage Gyro" and it also had a stop labeled the same. (I will have to study this more when I eventually go to MIDIfy the organ.)

[AllenAnalog]

Lamar,

I've emailed pdf files of my marketing and pricing sheets for the TC-4 along with a two page Gyrophonic Projector speaker cabinet listing. They are 1963-64 vintage. The TC-4 was introduced in 1958 and was produced for many years so as you've noticed with your two instruments, changes occurred over their long life of production and ordering options were different on your instruments. I think the last analog Allen organs were made in 1971 - the year my analog 3-manual theater organ was built.

There were MANY variations of the speaker complement in the cabinets of that era and they came in utility cabinets and furniture-grade cabinets. There were many different heights. depending on what speakers were inside, but they all had the same width and depth. I counted 22 variations in the 1964 price list. Gyrophonic Projector rotating speaker disks came in two sizes, depending on the height of the cabinet.

I have seven matching furniture-grade Allen speaker cabinets from the late analog era in three different heights and every one of them is different inside. Three came with my 3-manual theater organ and I bought four more on the Internet. I'll just throw out some information here for your consideration and if I got any of this wrong I'll look for corrections from Toodles or others with more analog organ experience.

In the 1963-4 sales literature, the standard complement of speakers for the TC-4 was two Gyrophonic Projector cabinets and a pedal cabinet. So the two 3-position horizontal switches on the organ below the stop tabs controlled the two Gyro cabinets. Since those switches are to control a multi-speed motor, each associated Gyro cabinet would have a DC motor and a control chassis that has the DC power supplies for the motor and switching relays to change the voltage on the motor. That chassis went through several revisions. This is a separate chassis (with the selenium rectifiers) from any amplifier that would have been in the cabinet.

The standard tremulant for the reed channel was electronic (from the right hand section of the Whind chassis on your organ) and it did not go through the spinning disk in a Gyro cabinet but through stationary speakers. An option was a speaker cabinet that included two Jensen horns, two 12" speakers, two tweeters and a 3rd (50-Watt) amplifier to separate the reed channel and give a more exciting sound to the reed voices. Some cabinets had the horns firing upward but I think that was only on the furniture grade cabinets for residential use, not the utility cabinets for church use where you want the sound projecting forward. Clearly one of the cabinets you have was some variation on that configuration but I don't see an amplifier in the bottom of the cabinet in your photo. The choke and caps are still there for a rudimentary crossover, typical of Allen cabinets of that era.

The 1963-64 Allen TC-4 spec also shows separate general tabs for flute, diapason and reed tremolo - all of which would have originated in the common electronic tremolo generator chassis but separately switched to the generators. Your two instruments may be different in that setup.

Whind, percussions (harp, celesta, carillon, sustain, bells), chiff, celeste generator, and the adjustable combination action were all extra cost options.

Edited to add:

I found a supplemental sheet entitled "Preliminary Information on Whind for Standard Models" and it sheds some light on your "sweet sixteen" speaker arrays.

For the TC-4:

Standard model Allen organs can now have Whind, offering advantages previously only available on most expensive Allens.

Diapason Gyro is replaced with model 105 (18 stationary speakers); bass cabinet section is the same. Price is $800 higher than the current price of TC-4 with two Gyro cabinets.

[toodles]

The tweeter Michael was thinking of is probably a phenolic ring tweeter--Amphenol is a manufacturer of connectors. Parts Express offers a modern phenolic ring tweeter so you don't have to go looking for used ones: https://www.parts-express.com/grs-pr...8-ohm--270-252

Currently on sale for $14 apiece. These actually have a pretty smooth frequency response except for a little peak at resonance. They fall off after about 15 kHz, but so does our hearing. They make a decent general purpose replacement. Note that the impedance is 8 Ohms--I don't know what is needed in your system.

One thing to note: if the amplifiers are transistorized (solid-state), it is not critical to maintain the impedance of the speakers as long as it stays above 4 Ohms; if the amps are tube-type, then it becomes important to keep the impedance to the original. Since 16 Ohm tweeters are almost non-existant now, and certainly not available at low prices, an option is to use two 8 Ohm tweeters wired in series if you have to keep the impedance at 16 Ohms.

If you use an 8 Ohm tweeter in a system designed for 16 Ohms, you'll need to adjust the crossover values. There are easy to use on-line calculators if it gets to that point.

The performance of the speakers you have may surprise you--the use of large cabinet volume with a relatively low-tech speaker does work and can work very well.

[Silken Path]

One of the amps is 16 ohm output and the other two are 8 ohm. Hmm.

Toodles I think the cutouts are a little larger than 2". If so, it would be easier to go to 3" than fill in the holes. I'll look in the morning. And it may be a question of balance in the gyro, but I don't know if it's that critical. Thanks! What do you think about using the tweeters that already have the bass filter cap? Can they be used without the crossover?

Larry, that's a lot of information to digest. So the tremulant from the wind machine went to a stationary speaker... This organ does not have the horizontal slide switches like the '59 model, but it does have the whind light on the panel and gyro on-off tabs. My question here is why have a DC gyro if something is not going to vary the speed? I also haven't found a wire for the 14V plug on the gyro and don't know where it's supposed to come from. The gyro is marked "100" in magic marker.

So the tremulant side of the whind generator does not control the speed and volume of the gyro? (I found the two other connections - one 115 AC, one labeled "switch" four prong.)

[toodles]

Balance on the Gyro is extremely important on any diameter and on any circle concentric with the axle. What that means is that items are best place in pairs 180 degrees apart from each other, and on exactly the same distance from the center of the axle.

On your photos of the interior of the cabients, the lower right hand corner photo has two rectangular holes and two circular holes. The rectangular holes are for horn mid-range tweeters and the circular holes are for the tweeters. Obviously this cabient was intended to have those drivers to get the full frequency range.

I try to avoid speakers with attached crossover components because those components are not usually of the highest quality and that means the speaker itself is probably of poorer quality, too. Once in a while you run into some that are OK, so it depends upon the individual speaker. The attached bass filter cap is intended to be the crossover, so any additional components aren't needed. Just don't use those with the cap attached in series to get 16 Ohms impedance--if you have that type of speaker and want to use it in series, remove the crossover cap, wire the drivers in series, and calculate the crossover cap you need for 16 Ohms.

[Silken Path]

Another day.

First of all, I don't have confidence in the wiring markings inside the organ. They appear to be in some shorthand known only to the electricians in the company that took the organ out. (The guy I bought it from was not one of them in the church.) The writing does not match the wire labels exactly. I would like to find the documentation to be SURE about this.

The power supply is a model 95. I haven't found a diagram of it in the ASM yet, but it may be in the section for another organ. The main AC appears to go in there, and there are at least two other takeoffs at the same point. There are two terminal strips in the distribution area. I think the main AC is at the two terminals closest to the outside.

Pulling the bottom oscillator drawer out and tilting it up gives good access to the distribution area. One terminal is at 90 degrees to the other, and those appear to be the three output points to the amplifiers. THAT matches the wire markings.

So... where would one have gone to get a model-specific, serial-number specific listing of the terminal connections? (Why, oh, why with Allen labeling everything, they didn't label this?)

And correction to the above - two of the T-50 amps are 16 ohm and one is 8 ohm.

I'm not giving up on figuring out the connections from the wire markings...

On edit: Thanks, Sir Toodles. I had the editing window open during your post. Makes sense. Most of the ones with the caps attached looked more for the car crowd than utility. OK - I would have identical components 180 degrees on the gyro, as it was.

AllenAnalog Larry sent me brochures and ordering information for early 60s models. Wow. Allen said the TC-4 was a "fine organ for medium or large size churches." I can't imagine them saying it was a mediocre organ. When this was published, it came standard with two 3-speed gyros and one pedal cabinet. Celeste was $500!

On Edit: Ordered three of the $14 phenolic tweeters Parts-Express to test.

[rjsilva]