Dual Rotary Subs Used At Trinity Church - AVS Forum
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post #1 of 29 Old 06-16-2008, 11:40 AM - Thread Starter
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I happened to be browsing the web-site of Cameron Carpenter who is an incredibly talented virtuoso organist. He recently recorded a new album on the digital organ at Trinity Wall Street and on Cameron's website, there was a picture of Bruce Thigpen (inventor of the Thigpen Rotary Woofer) sitting in on the recording session.


Above L to R: Bob Woods (President of Telarc and producer of the album); Bruce Thigpen (inventor of the Thigpen Rotary Woofer), Susan Slaymaker, Richard Torrence.

This immediately peaked my interest and made me wonder what he was doing there. As passionate as I am about organ music, organs, home theater and electronics and knowing the history of the trinity organ which is the most advanced state of the art digital organ ever built, I shot an email off to Bruce asking him about his picture on Cameron's website. I had no idea why he was there and I asked if by chance if he was going to be using his rotary sub technology to extend the frequency response of the organ to include 64' stops.

Bruce got right back to me, was very friendly and told me that he was at the recording session because 2 of his rotary subs were temporarily installed on the Trinity organ just for the recording session. Not only that but the organ was programed with digital 64' and 128' stops just for the recording session

Larger organs use 32' stops which produce 16hz. 64' stops go down to 8hz and 128' foot stops (which i never heard of, I think they only exist in the digital organ world) go down to 4hz

There are only 2 organs in the world which use true 64' pipes. Some larger organs use "resultant" 64' pipes which is a trick of using 2 smaller pipes tuned to the 1st and 2nd harmonic of the fundamental to give the effect of a 64' when it's not practical or cost effective to use real 64' pipes.

The trinity organ uses samples of real pipes recorded "pipe by pipe" stored and controlled by an array of 9 Unix computers which is the brain of the organ.

Bruce told me that 2 of his rotary subs were able to extend the response of the organ at the center of the church to 6hz @ 110db and this is a pretty big church which is located on Wall Street in Manhattan.

I thought all this was fascinating and asked Bruce if he would mind me posting about this and he said that he did not mind and that he would even post some more technical data.

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post #2 of 29 Old 06-16-2008, 01:05 PM
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I wonder what the Thigpen skeptics are going to pull out of their hats about this one. Organ music is not the only source material that benefits from the Thigpen Rotary.

FYI, I remember that about 5 years ago Bruce Thigpen said that he could build an even more powerful version of the Rotary sub. He said that he could build a version that would do 120 db rather than the existing version that maxes out at 110 db.

It's just too bad that I don't have $20,000 laying around for a Thigpen.

Talk about an attic fan
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post #3 of 29 Old 06-16-2008, 01:06 PM
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OTK,

We were asked by Robert Woods of Telarc and the Richard Torrence, a co-producer of the recording to participate and assist in getting more low frequencies out of the Marshall and Ogletree virtual organ at the Trinity Wall street church where Cameron Carpenters debut recording with Telarc took place.
We temporarily installed two TRW-17 rotary woofers in the church and were able to get down to about 6Hz at up to 110dB. The original woofer system would go to about 27Hz in the middle of the church at about 90dB, not quite a true 32 foot stop. We added 64 and 128 foot stops to the organ and Cameron used them in the recording.
Although this was a temporary installation we are planning on
installing a permanent TRW-17 woofer at Middle Collegiate church in New
York where Cameron is the artist in residence. It was a fun project
and Cameron is an amazing performer with a long and I believe very
successful career ahead of him.
A view of the church from wall street:



I will try to add more about the installation soon.

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post #4 of 29 Old 06-16-2008, 01:25 PM
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So where did the samples for the 128' stops come from? Or were they digitally created?
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post #5 of 29 Old 06-16-2008, 02:17 PM - Thread Starter
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Quote:
Originally Posted by brucet View Post


I will try to add more about the installation soon.

brucet

Thanks Bruce, look forward to it.

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post #6 of 29 Old 06-16-2008, 03:35 PM
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tkdee,

The Marshall and Ogletree organ uses samples recorded from a number of different pipe organs around the world. They have at least two different 32' samples, but no 64' samples. They attempted to obtain permission to sample the Atlantic City convention hall 64' diaphone for this recording however the request was denied. M&O divided the existing 32"stops by two, and I requested that they create some sine wave stops at 64' and 128'. The M&O organ can adjust any note in any stop in frequency and amplitude. By adding the new sine wave stops to the existing stops we were able to create very convincing 64' and 128' stops.

Here is an FFT of the Atlantic City 64' diaphone which formed the basis for the sound pressure levels used at Trinity.



Using this as a baseline I set the maximum levels in the center of the sanctuary at 105dB below 20Hz. The existing subs measured about 87dB at 27hz. We added a good bit of weight to the signal at very low frequencies. At 110 dB the large glass entry doors were moving, out of respect for the structure we stopped at 105dB and Bob Woods of Telarc was pleased with the result. Thanks for the question

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post #7 of 29 Old 06-17-2008, 07:47 AM
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Thanks for the response, that must have been something to hear.
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post #8 of 29 Old 06-17-2008, 07:57 AM
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Quote:


We temporarily installed two TRW-17 rotary woofers in the church and were able to get down to about 6Hz at up to 110dB.


So what did that "sound" like?

Sound at that level is all "Feel", correct?

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post #9 of 29 Old 06-17-2008, 03:10 PM
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Penngray

Perhaps the biggest misconception is that very low frequency sound is all "feel". If you get 6-10Hz up to over 120dB then yes, you begin to feel it. But you can actually hear it long before you feel it. In fact with mixed tones as is the case with a pipe organ the audible thresholds for very low frequencies are much lower, about 6 to 10dB less than the pure tone thresholds. In other words, well before you feel the sound you will hear it. In the middle of the sanctuary the 32' and 64' sine wave stops sounded really good. 105dB is the sound level it took to make these tones below 20Hz audible. This became the reference level for these stops.
In researching this project it is apparent that pipes in these organs are not really very loud, and definitely not very efficient. The pressure in the organ manifold determines how loud they play. The recordings show that they do not produce a really good pure tone because of the non linear compressibility of the air in the pipe. Also some stops are not supposed to produce a pure tone.

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post #10 of 29 Old 06-17-2008, 03:43 PM
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I need to say that the church was extremely helpful in allowing us to set up the woofers. They allowed us free run of the church for as long as we wanted to work. We explored the entire building in search of backspace volume. We crawled into but ruled out the crypts under the church.
We finally settled on a side entry enclosed porch with double doors leading to the sanctuary. The porch would enclose the back wave and the double doors gave us plenty of space for a temporary baffle.

this is an outside view of the enclosed porch:




This is what the inside of the porch looked like as the baffle was being constructed. The double doors on the other side of the baffle lead into the sanctuary.







This is the porch view of the finished temporary installation. We used 2 by 6" braces and 200 pounds of gravel to hold it in place.





This is a view of the finished baffle from the sanctuary side. If you enter the sanctuary through the main front doors these doors would be on your right and a gift shop is on the left.




I will post information about Telarc's temporary recording studio, the organ and performance measurements in an upcoming post. I was really impressed with how much effort and time Telarc put into this recording project.

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post #11 of 29 Old 06-17-2008, 05:33 PM - Thread Starter
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Thanks for the info Bruce, cool pics of the dual Rotarys.

Is the CD going to have a low frequency warning on the label?

At the Middle Collegiate church where you're doing your permanent Rotary Sub install, do they have the same Marshall and Ogletree virtual organ that Trinity has with the Ruffatti console and Def Tech bi-polars?

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post #12 of 29 Old 06-18-2008, 11:47 AM
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Bruce,

"...with mixed tones as is the case with a pipe organ the audible thresholds for very low frequencies are much lower, about 6 to 10dB less than the pure tone thresholds. In other words, well before you feel the sound you will hear it."

But is it just the higher freq that are audible, or is there some auditory phenomenon whereby the presence of (harmonically related?) higher freq makes the lower freq audible.

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post #13 of 29 Old 06-18-2008, 12:39 PM
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Quote:
Originally Posted by noah katz View Post

Bruce,

"...with mixed tones as is the case with a pipe organ the audible thresholds for very low frequencies are much lower, about 6 to 10dB less than the pure tone thresholds. In other words, well before you feel the sound you will hear it."

But is it just the higher freq that are audible, or is there some auditory phenomenon whereby the presence of (harmonically related?) higher freq makes the lower freq audible.

Stochastic resonance?

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post #14 of 29 Old 06-18-2008, 12:51 PM
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Quote:
Originally Posted by noah katz View Post

Bruce,

"...with mixed tones as is the case with a pipe organ the audible thresholds for very low frequencies are much lower, about 6 to 10dB less than the pure tone thresholds. In other words, well before you feel the sound you will hear it."

But is it just the higher freq that are audible, or is there some auditory phenomenon whereby the presence of (harmonically related?) higher freq makes the lower freq audible.

I was wondering the same thing. The one thing I could come up with is that the harmonic signature of a sub-audible note would be different. For example a 10Hz musical note would have some harmonic content at 20Hz, 30Hz, 40Hz, etc where a 20Hz note would have harmonic content at 40Hz, 60Hz 80Hz, etc. Basically by having your fundamental at a lower frequency you'll get a tighter grouping of harmonic content so it should sound different. I'm not sure if you will actually hear the fundamental though.
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post #15 of 29 Old 06-18-2008, 12:59 PM - Thread Starter
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Do sine waves have "harmonic content"?

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post #16 of 29 Old 06-18-2008, 01:13 PM
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Quote:
Originally Posted by otk View Post

Do sine waves have "harmonic content"?

No, but an organ would as demonstrated by the Fourier plot that Bruce posted.
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post #17 of 29 Old 06-18-2008, 01:16 PM
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Quote:
Originally Posted by brucet View Post

Penngray

Perhaps the biggest misconception is that very low frequency sound is all "feel". If you get 6-10Hz up to over 120dB then yes, you begin to feel it. But you can actually hear it long before you feel it. In fact with mixed tones as is the case with a pipe organ the audible thresholds for very low frequencies are much lower, about 6 to 10dB less than the pure tone thresholds. In other words, well before you feel the sound you will hear it. In the middle of the sanctuary the 32' and 64' sine wave stops sounded really good. 105dB is the sound level it took to make these tones below 20Hz audible. This became the reference level for these stops.

In researching this project it is apparent that pipes in these organs are not really very loud, and definitely not very efficient. The pressure in the organ manifold determines how loud they play. The recordings show that they do not produce a really good pure tone because of the non linear compressibility of the air in the pipe. Also some stops are not supposed to produce a pure tone.






brucet




Yes, but do you actually hear anything below about 20 Hz? It appears to me that all you could be hearing are the harmonics in the audible range. In other words, how pure are the test sine waves reproduced on site?
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post #18 of 29 Old 06-18-2008, 01:20 PM
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So, this all begs the question, brucet:

Did you see God?

"All men are frauds. The only difference between them is that some admit it. I myself deny it."
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post #19 of 29 Old 06-18-2008, 01:23 PM - Thread Starter
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Quote:
Originally Posted by tkdee View Post

No, but an organ would as demonstrated by the Fourier plot that Bruce posted.

the plot Bruce posted was of an actual 64' pipe from the Atlantic City organ

the digital organ at Trinity, the 64' and 128' stops are made up of sine waves if i read his post correctly in post # 6

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post #20 of 29 Old 06-18-2008, 01:29 PM
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I read that he added a sine wave to a pitch shifted version of the 32' stop to try and recreate the effect of the actual organ stop.
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post #21 of 29 Old 06-18-2008, 01:43 PM - Thread Starter
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if anyone is interested, here is Cameron playing the Trinity organ

as someone who plays and loves organ music, this is just a mind blowing performance to me

http://www.youtube.com/watch?v=pQxyQktNFwc

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Quote:
Originally Posted by otk View Post

if anyone is interested, here is Cameron playing the Trinity organ

as someone who plays and loves organ music, this is just a mind blowing performance to me

http://www.youtube.com/watch?v=pQxyQktNFwc

I can do that with my hands tied behind my back.

Oh, wait.......................

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post #23 of 29 Old 06-18-2008, 01:56 PM - Thread Starter
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Quote:
Originally Posted by sivadselim View Post

I can do that with my hands tied behind my back.

Oh, wait.......................


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post #24 of 29 Old 06-18-2008, 02:22 PM
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He is certainly a talented and skilled organist, but I can't say I see eye-to-eye with his playing of more traditional pipe organ music, particularly those from French-Romantic era where he makes them sounds like etudes in pipe organ technique. Nevertheless, I will admit that his arrangements of other music for the pipe organ are quite mindblowing and are a staple to his talent and skillset. For the traditional music, I happen to like Paul Jacobs interpretations more. His performance at the Trinity Wall Street Church can be found here.
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post #25 of 29 Old 06-18-2008, 02:39 PM - Thread Starter
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Quote:
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He is certainly a talented and skilled organist, but I can't say I see eye-to-eye with his playing of more traditional pipe organ music, particularly those from French-Romantic era where he makes them sounds like etudes in pipe organ technique. Nevertheless, I will admit that his arrangements of other music for the pipe organ are quite mindblowing and are a staple to his talent and skillset. For the traditional music, I happen to like Paul Jacobs interpretations more. His performance at the Trinity Wall Street Church can be found here.

yes, he's incredible also, this is the direct link to his streamed concert at trinity:

http://download.trinity-global.edges...d/c070809H.asx

speaking of French romantic, i got to see Felix Hell do a recital in February at the Basilica Cathedral in Newark where he played on a French romantic organ of 9,513 pipes

and getting back to Trinity, you can stream several full organ concerts from the 2006 and 2007 concert series

http://www.trinitywallstreet.org/music/?pipes

http://www.trinitywallstreet.org/welcome/?pipes

the 2008 concert series starts soon

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post #26 of 29 Old 06-18-2008, 04:20 PM
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Otk,

I honestly do not know how much low frequency information actually made it into the recording. With a little luck it will be good and have strong content down to 7Hz, but that remains to be seen. More about that later.

Noah/Kal/tkdee

The auditory phenomenon known as sum and difference frequencies or "beat frequencies" gives us the ability to perceive the difference between two tones down to a fraction of a Hz at very low sound levels. A good example is tuning a guitar. The difference frequency appears in our brain but not to a microphone. The tones can but do not need to be harmonically related. This is how a "resultant" stop works.
In our case the produced tones are real, in the resultant case they just appear in our brain. The audible threshold for the sine wave stops without mixing any other tone is higher in amplitude. Just using the pedals with the sine waves in Trinity gave audible notes down to about 9-10Hz with the sound pressure level limit we adhered to.
The posted plot above was of the low C pedal, a 64 foot pipe, from the Atlantic City organ. All of the notes in that particular stop had quite a bit of harmonic content.

J_Palmer_Cass.

Yes we can actually hear frequencies well below 20Hz. There is no brick wall at 20Hz for hearing. The sound needs to get progressively louder as you go lower in frequency. Age does not really affect our ability to hear low frequencies as it does high frequencies.

Sivadselim - God did not make an appearance, but we were told that there was a ghost in one of the crypts and the night guardsman refused to go in with us.

Here is a test of the 64" sine wave stop at Trinity. We added harmonics by putting other stops on top of the fundamental. M&O also created a 32" stop divided by two.

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post #27 of 29 Old 06-18-2008, 04:34 PM
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Quote:
Originally Posted by brucet View Post

The auditory phenomenon known as sum and difference frequencies or "beat frequencies" gives us the ability to perceive the difference between two tones down to a fraction of a Hz at very low sound levels. A good example is tuning a guitar. The difference frequency appears in our brain but not to a microphone. The tones can but do not need to be harmonically related. This is how a "resultant" stop works.
In our case the produced tones are real, in the resultant case they just appear in our brain. The audible threshold for the sine wave stops without mixing any other tone is higher in amplitude. Just using the pedals with the sine waves in Trinity gave audible notes down to about 9-10Hz with the sound pressure level limit we adhered to.

How does this differ from providing the harmonics of an unsensed tone which the listener then perceives from experience? (Cheap, tiny speakers depend on this trick.) Of course, such a perception might sum with a transduced but subthreshold input fundamental.

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post #28 of 29 Old 06-21-2008, 06:23 AM
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This is called heterodyning, or mixing. Add to different frequencies together (A+B) and you get A, B, A+B, A-B. i.e. You should be able to play 20Hz in one speaker, and 19Hz in another and you will hear the 1Hz difference (A-B) because once every second, the two sine waves are in phase and add in amplitude. Same goes for 39Hz (A+B). Filter out the one you want to use. This is how radios work (Superheterodyne). I never thought of using it in audio frequencies until Bruce's post. Learn something new all the time!

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post #29 of 29 Old 06-21-2008, 07:33 AM
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Quote:
Originally Posted by Vinculum View Post

This is called heterodyning, or mixing. Add to different frequencies together (A+B) and you get A, B, A+B, A-B. i.e. You should be able to play 20Hz in one speaker, and 19Hz in another and you will hear the 1Hz difference (A-B) because once every second, the two sine waves are in phase and add in amplitude. Same goes for 39Hz (A+B). Filter out the one you want to use. This is how radios work (Superheterodyne). I never thought of using it in audio frequencies until Bruce's post. Learn something new all the time!

Dr V

I am familiar with this, of course. What I am trying to get at is the distinction between lowering the threshold of perception to real signals by adding overtones and the subjective perception of a subharmonic that, in fact, is not transduced.

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