An Interloper?

[jonny1note]

Hello everyone,
I am atypical of other members here, I think.
I am not an audio specialist, ... Rather, my background is ground avionics and pipe organs.
I have built a Williamson amplifier with 807's (just a bit of age-dating benchmark here!)
I am not a gigger, backline design specialist, mixmaster or roadie, but have an interest in sampled pipe organ voices for which I need to compile suitable audio packages for Virtual Pipe Organs in fixed installations.
I have only ever built reflex boxes (in the olden days)
My special interest at this time is 32' voices at 110dBA (16Hz lo-note)... big challenges.
I hope to learn much here.

Bill, I have before me your first publication (I think)...Loudspeakers for Musicians, first printing 1999.
Clearly, what is happening on your site now is miles away from the Snails, SnailsII, Mini, and Siamese Snails of yesteryear.
I was contemplating a Snail project (until I came across this site) but now wonder if the Snail designs are now irrelevant in modern thinking?

I trust that this antiquarian subject is not mutually embarrassing! ...or (worse) that I don't have the wrong Bill Fitzmaurice!

I hope there's a Billbox out there for me somewhere.....


Best wishes,

John, Sydney

[Bill Fitzmaurice]

I was contemplating a Snail project (until I came across this site) but now wonder if the Snail designs are now irrelevant in modern thinking?

They are, all at least three generations removed from the current lineup.

[jonny1note]

Thanks Bill.
I will frame a suitable entry level post for insertion elswhere in the forum
John

[Charles Jenkinson]

Hello and welcome!

The frequency content of your 16Hz note is i imagine something people might be interested in, i.e. how much fundamental is there.

[Grant Bunter]

Hi John,
Welcome to the forum

Sydney, as in NSW, Australia?

You're quite fortunate if so, as there a number of forum members from there.
Specifically "Titanium hand" who has built and runs Tuba 60, which, as far as I can see, offers the lowest (in frequency) "pro sound" cab, so you could get to test out response, perhaps, if you have a chat to him.
Hopefully Bill will chime in again, to see if one of his home thetre offerings may go lower again, but you would have to tell us a few things, like, do you want to fill a church with rich deep pipe organ music, how big a room and so on...

[jonny1note]

Bill: The redundant literature is now dumped, though it did in retrospect give some insights into your thinking.

Charles: There are two voices of interest in the pitch range.. the Violone has much colour... fundamental plus at least 7 partials of roughly equal amplitude. I am not concerned with this voice as about 95dB will be good.
The major voice is roughly sinusoidal and is required at 110dB. This is the challenging voice of course.

Grant: Thank you.... Yes, I am a Colonial boy.
This is an augmentation where sampled voices will be used alongside real pipes in a concert room environment. Seating is for around 1000 and it is a 2.2 sec. room.. (no good for youse headbangers but perfect for my needs).
Thanks for the Tuba 60 pointer... I had looked at this when I found this site and not having seen plans yet, am unsure whether I can sqeek some more at the bottom (below resonance) using some judicious bottom end equalisation. I realise that this is a risky manoeuver especially if there is little choke at the speaker.
But (bad grammar), I am here to learn and to find solutions that work well.
Thanks for the point to TitaniumHand.
There are more audio aspects to this particular project but I will save that for another day.

Oh, the only speakers I have to hand are a few JBL GT5-15's
Cheers

[Grant Bunter]

Great! Another Aussie on board. Don't be surprised if you are lumped in with the rest of us Antipodeans, and that is not put up as a derogatory term.

I should apologise, offering up Titaniumhand without asking him, he's a good Aussie bloke and keen BFM devotee so I'm hoping that wouldn't be a problem.

Perhaps you have picked this up reading Bill's book; horn loaded designs get greater sensitivity and hence response from the drivers upon which those designs are based, with less amp power and "cleaner" (as in less harmonics) sound when compared to direct radiator cabs.
This invariably leads to drivers requiring limiting (electronically, there's a number of methods of achieving this) for a certain lowest frequency setting for any given cab. This is in order to prevent blown drivers.

Limiting in this sense is setting a maximum voltage level a cab can receive, and not something that is at the other end of the scale to compression.
Why voltage rather than watts?
Because voltage is easily measured and wattage is a product worked out by calculation.

There was some limited discussion in one thread a while back about getting cabs to play lower than "usual".
The premise is, in order to play lower, the cabs "normal" limit has to be reduced, significantly.
There is a possibility that this may fall into a situation that could help you in your quest, the caveat being that in order to get the required SPL you mention, may involve a significantly larger number of cabs.

You would have to have Bill's help to determine an appropriate cab, and voltage limit...

[Charles Jenkinson]

This is very interesting. The T60 with the lowest knee is lab15 at 25Hz. 16Hz is not on the chart but I'd reckon about 15dB down. I'm a bit doubtful about a straightforward T60 solution here. It sounds like a something else solution to me....? Though I still think a horn is the best approach. I'm no speaker designer but the size of what you may need might put it in the field of a civil engineered structure, or at least stud walling. Are there no bespoke horn designs that have been developed/designed for pipe organ reproduction?

Construct and fix it on a small trailer chassis and you're done, providing it'll fit through access doors.

[Bill Fitzmaurice]

This is very interesting. The T60 with the lowest knee is lab15 at 25Hz. 16Hz is not on the chart but I'd reckon about 15dB down..

The reality check is that you don't hear 16Hz from pipe organs, you hear the harmonics. Therefore a 32Hz response is adequate. It's the same reason why electric bass cabs for low B with 31Hz fundamental don't need to go to 31Hz.

[jonny1note]

Hmm.. OK, I concede of course that 16Hz is inaudible but it has a physical presence that is real and which underpins the harmonic series of the organs pedal chorus.
I want to feel the presence of it... and I therefore must find a way to achieve it.

There are a number of solutions out there but they are too unweildy and/or costly for me to consider; I wondered if there might be something here, or suggested changes to existing designs.

I cannot comment on requirements for guitars vs the steady tone requirement that I have.
The Tuba HT looks exciting for 16' (32Hz) stops.. and I will persue that along with others that you might suggest.
Cheers.

[Charles Jenkinson]

I want to feel the presence...

I like it!

Start with your 110dB and 16Hz: Where is that, at 1m or significantly further away?

I'm not familiar with the HT side of things, so others could advise better, but there's no free lunch; large and unwieldy it may be. I've wondered about a 'modular' design where various horn parts could be joined with a gasketed joint and butterfly clips or something more appropriate, to make something large to be less unwieldy / more portable.

[Bill Fitzmaurice]

Hmm.. OK, I concede of course that 16Hz is inaudible but it has a physical presence that is real and which underpins the harmonic series of the organs pedal chorus.
I want to feel the presence of it... and I therefore must find a way to achieve it.

Unless you have a listening room small enough to pressurize via cabin gain, which means a longest dimension no more than 20 odd feet long, and/or you have a massive system, it's not going to happen. If you think you've heard/felt 16Hz where that was not the case, think again. You didn't. You heard/felt harmonics.

[Charles Warwick]

I'm no speaker designer but the size of what you may need might put it in the field of a civil engineered structure...Construct and fix it on a small trailer chassis and you're done, providing it'll fit through access doors.

*ahem*


First off, I think we need to define a few parameters before deciding what's unfeasible.

-What size of room are you looking at using this in?
-What kind of room would it be? Treated home theater room or reverberant cathedral?
-110db@16hz at what distance from the speaker?

If this is just for home use (i.e. in your house) I would suggest looking into the THT. Of all the BFM subs it reaches the lowest. If you want lower extension than the THT at 110db you either need a custom designed horn or an infinite baffle design, which would would then require lots of speakers, power, and a spare room.

[bmf]

You will have to translate the page but IIRC even this monster horn only reached down to 25hz actual. As Bill said 16hz will only be reached with harmonics,

http://milano.repubblica.it/multimedia/home/7328307

[Charles Warwick]

Generally the only way to reach those levels are with a speaker the size of a room, e.g. infinite baffle or a trailer truck. Hoffman's Iron Law strongly applies to the practically of doing things like this. Here's an example that I stole from http://www.glasswolf.net/papers/hoffman.html

If you decrease the f3 of your speaker system by a factor of two while retaining the same efficiency, you would have to increase the enclosure volume by a factor of 8 (2^3=8). Let's say you have an enclosure with an efficiency of 90dB/w/m that is 2 cubic feet in size. Suppose the f3 of this system is 30hz. However, you've decided you want a heavy bottom end and wish to drop the f3 to 15hz. Without decreasing efficiency, this change would require an enclosure measuring 16 cubic feet in size!

It is for this reason that anyone who has a system capable of reaching single digit hz with any authority has a small room with a huge amount of space taken up by subs, both in total enclosure volume and in volume of air capable of being moved. This is why infinite baffle systems are ideal for things like that because you can mount 4 high excursion, high power, 18'' subs that utilize the attic or a basement as their enclosure, thus fulfilling Hoffman's Law by having a gigantic enclosure and lower efficiency (and thus needing tons of power too) in order to reach low and hit high SPL. A horn loaded system (with high efficiency, SPL, and low extension) is also bound by such requires and thus needing a gigantic horn to do so. The Matternhorn is a prime example of that compromise, in order to reach really low and loud, they had to make it huge with tons of volume displacement and power.

Pretty sure I'm but I enjoy talking about speaker theory and application.