Sonotube/Pipe Speakers

[Keys]

Hello,

I'm working on an organ project that uses modern computer technology for sound generation, but vintage speaker pipes from the 70s for some of the speakers.

There are 40 pipes of various lengths, each with a speaker in the top. Eighteen are 8" pipes with 8" speakers, 18 are 4" pipes with 4" speakers, and four are 6" pipes with 5" speakers in them. The speakers, being in the tops of the pipes high on the wall, disperse the sound by reflecting off a plaster ceiling. (This wouldn't work if the ceiling were non-reflective like 'acoustical' tile.) All 36 of the eight- and four-inch speakers are being replaced and sealed into the pipes. They were merely sitting on top of the pipes before.

The patent calls the opening at 13 a bass reflex port. It is shaped to resemble the mouth of a wind-blown organ pipe. I have to admit I've never seen a bass reflex port like that before, but just because I've never seen one doesn't prove anything. (See figure 2.)




Each pipe has what appears to be fiberglass rings at 19. According to the patent they are to prevent standing waves in the pipes. At 17, below the port or mouth at 13, there is what appears to be rock wool, which according to the patent is to dampen lower frequencies.

My question is this: Should the pipes be left as they are? Should they have a sound-reflective material inserted at 13 to direct the sound out of the pipe? Or should the pipes be sealed? That last one wouldn't be easily done, but that wouldn't stop me. It would be a shame to put 36 new speakers in these things and have the sound be less than it could have been because of a design flaw that could have been fixed.

Thank you for your time and advice.

Sincerely,


Keys aka John

[fpitas]

Bass reflex ports often used to look like that on vintage speakers. No duct was used. If you add anything to it (like a duct etc) you will affect the tuning.

[Keys]

Thank you for responding, sir.
.
I'm not considering adding a duct, but I am wondering about directing the sound out the port at 13 rather than into sound deadening material at 17.

At the moment, most sound is going into the deadening material, except for what goes out the speaker at the top. I would merely add wood or similar material to reflect material out the port at 13.

Keys aka John

[fpitas]

Hi John, I'm Francis. Sound will radiate outwards from that port, just like from a normal reflex port. It's not clear what improvement you hope to make.

[ericanderson]

Sir, I'm no expert but this looks like a tapered wave quarter pipe. TWQP. I think you need to reach out to Paul K. Or Wolf. The speakers or (drivers)were designed for that particular installation.
Eric

[ericanderson]

More to the point. Designed for a particular installation.

[Keys]

Mr. Francis,

What I'm trying to get at is that the port is on the side of a straight pipe and the sound is directed to a bed of sound absorbent material. If it's not a problem I'll leave it. I just wondered if it would be better to direct sound out the port. Apparently it isn't.

Mr. Anderson,

Nothing is said in the patent about a tapered wave quarter pipe, though it does refer to resonating at the lowest frequency to go through the pipe. There are several references to emulating the look of organ pipes.

One problem is that many of the speakers no longer function because of bad surrounds, etc. The only markings give impedance and serial numbers -- I think -- but no manufacturer.
Thank you for your insights. It seems I have more reading to do.


Keys

[fpitas]

I'm guessing that sound absorbent is in reality to absorb high frequencies, similar to its function in a TL speaker. Perhaps some of the high frequencies were not on the desired chord relationship to the fundamental etc. Only a guess...

[DeZZar]

What I'm trying to get at is that the port is on the side of a straight pipe and the sound is directed to a bed of sound absorbent material. If it's not a problem I'll leave it. I just wondered if it would be better to direct sound out the port. Apparently it isn't.

Not quite how it works. Ports tune the air mass of the enclosure to a given resonant frequency that re-enforces the low frequency performance of the driver. Air ultimately oscillates within the port - it doesn't 'come out' as such.

[billfitzmaurice]

I'm working on an organ project that uses modern computer technology for sound generation, but vintage speaker pipes from the 70s for some of the speakers.

There are 40 pipes of various lengths, each with a speaker in the top.

If you're using speakers there's no reason to have separate pipes or speakers for each note.

[Keys]

Mr. Fitzmaurice,

If you're using speakers there's no reason to have separate pipes or speakers for each note.

Quite correct, sir! With 'only' 40 pipes/speakers that's not possible. An organ typically (in the US) has 61 keys on each manual (keyboard) and 32 pedals. The instrument has a sounding range typically from an octave below (two octaves below in the pedals) to more than two octaves above. [Composers write which notes to play but indicate which stops to use. The stops take care of the extra octaves and whether particular overtones are reinforced.]

Electronic organs usually try to produce the sound of pipes. A reasonably sized pipe organ might have 2,500 pipes or more, sometimes much more. Multiply 61 keys times 50 stops (a modest size) and you get the idea. Trying to make that sound come from six, eight, or even a dozen speakers is ludicrous in my personal opinion. Please note that most digital organ companies disagree. While most digital organs have very good sounds for individual stops, they often lack something when stops are combined for the biggest sound. Much of my effort in this project is to have very good individual sounds that combine in the air rather than in a mixer that can make an organ sound like a recording instead of an instrument. I'm using these speaker pipes because they can be made to look nice, and even at their worst look better than a bunch of speaker boxes lined up on a shelf.

Please note that these are only my personal opinions that I'm trying to implement in my personal instrument. Yes, it's my personal instrument, but the church where I play lets me use it and experiment a bit. I will not be starting a new company or be competition with anyone. I'm retired and will stay that way. It is true that digital organ manufacturers have made good profits with their own approaches to things. I just have to keep my ears and my wife happy! :-)

Bless us all!

[billfitzmaurice]

I think you're missing the point. Pipe organs use tuned pipes to create each individual note because they don't use speakers, they use a pressurized air within each pipe, in the same fashion that woodwinds do. If they could have used amplifiers and speakers they would have, but those didn't exist when the pipe organ was invented some 2500 years ago. If they had an electronic means of creating sound they would have. If you want to use a separate speaker for each note that can be done, but since a loudspeaker doesn't require the use of a tuned pipe to realize a given pitch and timbre it's an unnecessary complication.

[Ron_E]

From the patent: https://patents.google.com/patent/US3718747

"In order to supplement tone radiation at lower frequencies, where an organ pipe mouth is most efficient, we have provided a bass reflex port in each electroacoustic pipe, the port being both a radiator and a resonating device, dimensioned to resonate acoustically with the enclosure at or slightly below the lowest frequencies required of the pipe. The port is located where the mouth of a conventional pipe would be, so that the combined tone radiation from the top of the pipe and the side of the enclosure via the port will be pipe-like."

The port sounds like it's nothing more than a standard rectangular port. At low frequencies wavelengths are so long it's placement isn't all that important and I don't think the claim about the radiation pattern being pipe-like is true for low frequencies. There's no need to worry about reflecting sound out of the port at low frequencies.

Ron

[billfitzmaurice]

It's describing a MLTL. more or less, within the constraints of what was known in 1927. That wasn't much, as 1927 was at the very beginning of major research into sound reproduction, the result of movies going from silent to 'talkies' and the golden age of radio.

[djg]

Maybe it's time for something new.

https://www.youtube.com/watch?v=C96lYzVpak0

[Keys]

Gentlemen,

Thank you all for your help and explanations. You stopped me from doing something foolish because I really didn't quite understand how these speaker pipes work. I am grateful. When the project is finished, I hope to have some pictures to post.


Keys aka John

[JRT]

Gentlemen,

Thank you all for your help and explanations. You stopped me from doing something foolish because I really didn't quite understand how these speaker pipes work. I am grateful. When the project is finished, I hope to have some pictures to post.


Keys aka John

John,

Check out Hauptwerk software and implementations.

Below is a lower budget example in use:

Below is a description of the above setup:

Something a little nicer:

And more extravagant: