Max SPL 32' stops

[mashaffer]

Maybe one of you can help me answer a question for which I have not found any real information. In a typical pipe organ installation having 32' pedal stops what typically would be the max SPL produced by the low C in the center of the listening area? I need to have a pretty good idea of typical values so that I can provide for adequate reproduction of the 16Hz frequency with a little bit of headroom. My gut tells me to shoot for 120dB but I have no real reason to pick that number. Empirical evidence would be splendid. :)

mike

[davidecasteel]

I found a document that might answer that question, but it's not free: http://www.jstor.org/discover/10.230...47699054513107.

Here's a document that might serve your needs: http://www.pykett.org.uk/NoiseBitDepthVPO.htm.

David

[michaelhoddy]

SPL is a devilishly complex thing to calculate. There are several different weightings used (A and C weightings are most common) that are frequency-affected. SPL is completely affected by distance, at which point the inverse-square-law comes into play, but only in free space. In an enclosed space, which is where we find most pipe organs, all the boundaries, distance to them, and construction methods have a rather complex effect on SPL calculations, and all those calculations change as frequency changes. I work in the pro audio design and installation field, and we use some rather powerful software to predict these things in a way that's just scratching the surface. So, in short, it's not an easy question to answer without a lot more information.

The other part of this is that SPL in audio is essentially a modified measurement of amplitude, with a given source, at a given distance, at a given frequency (or band of frequencies- weighted or unweighted). This corresponds to volume.

The thing that makes the pipe organ unique when it produces sound is that it essentially moves a lot of air at fairly low amplitude, rather than producing a single high-amplitude source (except for high-pressure reeds and such). This is because any pipe, or all of them together, produce large quantities of resonance- the air column excited in the pipe, the surface areas of the pipes, etc. When combined, much more so than a typical speaker, which might be much louder, but which creates an entirely different effect. You can think of this as the difference between filling a large room with 100 10-watt light bulbs as opposed to placing a single 1000-watt light bulb. This concept is what bedevils many makers of electronic organs. Obviously, this is an oversimplification, but hopefully you get the idea.

It is entirely unlikely you will ever encounter 120 dB from a single pipe, even when measured at its mouth, with the exception of a high-pressure reed pipe, and definitely not at any reasonable distance in the listening area. 120 dB is closer to the SPL of a jet engine at fairly close range. Flue 32's are WAY below that level, but they move and resonate an incredible amount of air. That's what makes them effective. A reed 32 will be louder and obviously harmonically richer, but the net effect is still not about absolute volume.

Speakers which reproduce 32's effectively have to mimic these effects, and it usually involves a combination of lots of cone or vent surface area, a very low-tuned box design, and the excursive ability of the driver to move a LOT at very low frequencies. This is something that most PA-style speakers were not designed for, and why they often perform poorly in this application despite the ability to handle much higher overall power levels.

[toodles]

The threshold of pain is typically 120-130 dB (varies by individual)--mine is a little lower than average (around, say, 110 dB). So designing a system to produce more than than 120-130 dB is a waste.

10 to 20 dB lower, is probably sufficient. The low C on a Contra Bourdon 32 pushes your stomach more than your ear drum--it's more felt than heard.

Toodles

[Hamman]

Late getting in on this thread.....anywho, for my 32' pedal bass stops I send them through a subwoofer.This threshold of pain conversation has me bewildered as what that has to do with feq. below 40Hz?? If you are able to break the 120 db barrier with a 32' stop then the USGS should be able to pick it up on seismic sensors! I'm finding out (the hard way) that classical organs are not suppose to be bass heavy but "blended"

The threshold of pain is typically 120-130 dB (varies by individual)--mine is a little lower than average (around, say, 110 dB). So designing a system to produce more than than 120-130 dB is a waste.

10 to 20 dB lower, is probably sufficient. The low C on a Contra Bourdon 32 pushes your stomach more than your ear drum--it's more felt than heard.

Toodles

[myorgan]

I'm finding out (the hard way) that classical organs are not suppose to be bass heavy but "blended"

Then why do so many classical pipe organs sound so "tubby" when played? I find that some have very little upper frequency development that carries beyond the pipe mouth. It is the upper frequencies that provide clarity to the music, yet so many organs (& sometimes organists) don't appear to understand that.

I've been listening to a recording of Marcel Dupré's organ & orchestra works on my way to work and back (long drive!), and have found some nice sections of the pieces, yet most are rather non-descript, and even musically boring. Could it be due to the recording instead of the organ or organist?

BTW, don't underestimate the power of low frequencies when talking about the threshold of pain. Many times, those frequencies cause damage we neither hear nor understand. Food for thought.

Michael

[Hamman]

Well my comments were essentially derived from being a Hammond player and one with the genre of that hunts for that deep loud bass. But since taking a interest in "classical" organ I'm finding that you don't use the bass pedals for your rhythm section like a lead bass guitarist over there slapping the bass. Yes its suppose to be present but not the driving force...I still say "blended"....but heck what do I know i'm just starting out in this classical field. :-P Most of the recordings I have been listening to don't have overpowering bass yet a grand fullness from top to bottom.

Then why do so many classical pipe organs sound so "tubby" when played? I find that some have very little upper frequency development that carries beyond the pipe mouth. It is the upper frequencies that provide clarity to the music, yet so many organs (& sometimes organists) don't appear to understand that.

I've been listening to a recording of Marcel Dupré's organ & orchestra works on my way to work and back (long drive!), and have found some nice sections of the pieces, yet most are rather non-descript, and even musically boring. Could it be due to the recording instead of the organ or organist?

BTW, don't underestimate the power of low frequencies when talking about the threshold of pain. Many times, those frequencies cause damage we neither hear nor understand. Food for thought.

Michael

And with that I'll gracefully bow out of this topic since I'm noticing it is "pipe" and not electronic

[indianajo]

I've been listening to a recording of Marcel Dupré's organ & orchestra works on my way to work and back (long drive!), and have found some nice sections of the pieces, yet most are rather non-descript, and even musically boring. Could it be due to the recording instead of the organ or organist?
l

There are a lot of really undistinguished recording engineers, and pipe organ requires a good one. I'm very happy I received a copy of Marcel Dupre's 1955? performance at St Thomas NYC recorded by C. R. Fine, one of the legends of the fifties. Strictly monophonic, however.
Furthermore, the richer buyers who would buy pipe organ records in the sixties, tended to own fine wood Magnavox or RCA consoles that the needle would jump out of the groove if there was too much 32'. Those consoles were "top of the line" pricewise but were not state of the art for cartridge compliance or tracking force or dynamics. Techy engineers and students were pushing those boundaries with their component hifi-s, but these people were not doctors lawyers or important. The console owners also tended to be the careful types who would take the record back to the department store and ask for their money back because it was "defective" if the needle jumped out of the groove, IMHO. I have a couple of used 1954-55 Colombia recordings of E. Power Biggs that have significant bass, whatever the other failings of the microphones were ( and Colombia weren't using Neumans then, I suspect). By 1964 when Colombia's Bach Organ Favorites by EPB came out, the bass had been backed off quite a bit by the sound engineers. The trebles were much clearer on that recording than the 1954-5 ones though.
I don't think I would try to listen to a pipe organ recording in a car. Those buzz box cars that infect the roads prove that bass can be produced in and around a car, but flat frequency response? The whole car audio movement ruined hifi in my market, nobody even tries to sell flat frequency reponse here. They are trying to get the loudest buzzz.
As far as the 120 db thing, must be an East Coast phenomenon of pipe organs. I'd never even heard a pipe organ that would move my belly until last year at St Bartholemew's in Louisville. And that one produces no where near the amount of bass that I hear at an Amy Grant (Tretorn tour 1990?) or Jeff Beck (2011) concert. Yes, the St Bart' pipe organ is deeper in tone, but not as loud.
Of the 100+ organ LP's I received 3rd hand from the estate of Dr E. Fuchs, a couple of recordings by Lionel Rogg organist on Peerless Record Co Ltd have the best engineering. These were recorded by Technical Service of Radio Zurich on the Grossmunster Zurich organ.

[pictureroll]

What is SPL ?

Jerry F Bacon-Dallas,Tx

[davidecasteel]

Sound Pressure Level

David

[mashaffer]

Thanks guys. This is a really good discussion. RE: threshold of pain in my limited experience I have found the SPL that cause me pain in the midrange start to become much less problematic in the low bass regions. I am working toward a significant VPO project and I suspect I will just have to experiment a little bit and see what sounds natural. I know folks have gotten acceptable results in a home situation with a single 18" IB subwoofer but in a 50,000+ ft^3 auditorium I doubt that we will get any room gain. :D I will have to play around a bit with what I have on hand and see what I get.

mike

[myorgan]

I know folks have gotten acceptable results in a home situation with a single 18" IB subwoofer but in a 50,000+ ft^3 auditorium I doubt that we will get any room gain. :D I will have to play around a bit with what I have on hand and see what I get.

Mike,

Don't underestimate the power of the bass. I didn't think the Symphony's organ had much bass at all, but coming out of a 15" HC-12 speaker, it managed to rattle the floor of the stage a couple of months ago, and for the Organ Symphonie, my students "felt" it in the back of the balcony. I've noticed that when I move my organs from place to place, for some reason the bass can be rather non-descript in a smaller setting, but in a larger venue, it takes on a life of its own--it's the upper frequencies that need reinforcement.

Hope this helps.

The other Michael.