If Mr Thigpen wants to defend his design he is more than welcome to, this is open forum. No need t9 fight that battle for him, esp if you have no real world experience with the dEvice. All just a guy did was list Thigpen self stated specs... which are not astounding if we consider 16hz to be the lowest note of importance (to the OP).
Hi Bach On,
As I'm the guilty party suggesting 2ea. 6"I.D. ducts I went back, and checked the simulation in Hornresp, and 1ea. 6"I.D. duct @ 17-3/4" (45cm) would be sufficient. That is for 1ea. ST385-8 in your box. Much easier. So much for just a quick guess.
I'm attaching a number of the Hornresp screens including the input I used. Please, check everything to make sure I didn't fumble finger the data.
I'm also the one w/ the rule of thumb for passives area / driver Sd. It's an old rule, so many people may not have heard of it. Anyway, I also pointed to Jeff Bagby's software which I believe is quite nice for designing PR boxes. For all other boxes I recommend Hornresp and AkAbak.
Best of luck with your project.
Regards,
P.S.: At the bottom of the reply page you'll find a Manage Attachments button. This will pop up a window to allow you to find files on your computer to use as attachments.
As I'm the guilty party suggesting 2ea. 6"I.D. ducts I went back, and checked the simulation in Hornresp, and 1ea. 6"I.D. duct @ 17-3/4" (45cm) would be sufficient. That is for 1ea. ST385-8 in your box. Much easier. So much for just a quick guess.
I'm attaching a number of the Hornresp screens including the input I used. Please, check everything to make sure I didn't fumble finger the data.
I'm also the one w/ the rule of thumb for passives area / driver Sd. It's an old rule, so many people may not have heard of it. Anyway, I also pointed to Jeff Bagby's software which I believe is quite nice for designing PR boxes. For all other boxes I recommend Hornresp and AkAbak.
Best of luck with your project.
Regards,
P.S.: At the bottom of the reply page you'll find a Manage Attachments button. This will pop up a window to allow you to find files on your computer to use as attachments.
Attachments
I addressed all these things previously. Ports are super easy to add to a box. Easier than adding a driver or a passive radiator. You don't need an internal support system to hold the port, if you install it properly it isn't going anywhere and it won't make any noise. I already told you what port velocity was in my last sim and I'll tell you what it is in this sim. I showed ALL the sims in my previous post at 17 mm excursion, which I'm guessing is you driver's Xlim (destruction point). The ported box takes LESS excursion to make MORE noise.
If you don't understand these graphs ASK about what they mean. I'm showing you as clearly as I can that you are getting some horrifically bad advice here from some people.
Pic 1 - Hornresp inputs.
Pic 2 - Schematic. This shows the layout and size, this box is a bit larger than yours because the port is assumed to be external to the box. I can fix this up later, and I can also do a more accurate sim if you tell me exactly where the driver is located on the box.
Pic 3 - Response at xmax. THIS TIME I showed response at xmax, not at xlim so it's not quite as loud. This time box resonances are NOT masked. Those squiggles up past 120 hz are the resonances people seem to like complaining about. They won't measure as bad in real life as the sim shows, and if they bother you at all (they won't) a small amount of stuffing in the right location in the box will make that response curve smooth as a baby's butt.
Pic 4 - Port velocity peaks at 16 m/s with this 200 sq cm 60.5 inch long port. This is acceptable, there won't be any port noise. If you don't mind a larger, longer port that would be even better.
Pic 5 - This is the excursion graph, this shows that the cone excursion at the power level these graphs are shown at is 8 mm. You can use a high pass filter to protect the driver below 14 hz if you like.
An externally hosted image should be here but it was not working when we last tested it.
So you can see that port and/or enclosure resonances are NOT a problem. Port noise is NOT a problem. Adding a port to a box is free and only slightly more difficult than tripping on your own shoelaces. The ported box outperforms the sealed box AND the dual driver sealed box by no small margin. Passive radiators are expensive and you will need probably 4 of them PER driver.
Passive radiators are not an upgrade. They are only desirable when you need small box size. As I just showed resonances are NOT a problem, that stuff is outside the passband and won't be audible. Even if it was a small amount of stuffing would clean that right up and give a ruler flat curve.
It isn't odd, this is basically almost exactly your own personal home system and it's exactly the same thing you always recommend, and while it's usually a bad recommendation it's extremely bad in this case.
A leaky sealed box won't provide a resonant sound. (For that matter a resonant box won't provide a resonant sound either, if it's well designed it will produce and accurate reproduction of whatever it is presented.) Resonances are not mechanically risky. I can say for sure, it WILL NOT be loud enough.
Adding a bit of stuffing and a small leak to the box is only very slightly different than what he already has, and what he already has is woefully inadequate.
Are you seriously recommending a dual sub system with a leaky sealed sub playing low bass and a K-horn playing high bass? This is getting beyond ridiculous now. Adding a port to his existing box costs NOTHING and is a much better solution. The problem is that 16 hz is not loud enough, your solution does nothing at all to address that but adds a truckload of gear for no apparent reason.
Really? A cheap plate amp has a built in high and low pass filter and a crossover. And it's not much more than $150. So far your recommendation costs the price of a K-horn AND a new dsp, and doesn't address the original problem, which is that 16 hz is not loud enough. Adding stuffing and a leak to the box isn't going to make it any louder.
Now we're shopping for amps? He has an amp, and if that isn't good enough a cheap plate amp will do everything he needs INCLUDING dsp duties.
I cannot even imagine why you are showing a picture of your home system frequency response. For a subwoofer you've got an antique woofer with 2 mm xmax on OB, which is absolutely the worst choice of sub you could possibly dream up. On top of that for the higher bass you have a K-horn which wasn't even a particularly good design when it was introduced 50 or so years ago. Besides being a badly engineered system, neither of these are in any way applicable to this thread.
I imagine you included these graphs just to allow you to take an offhand swipe at simulators and simulations again. Sim curves are not theoretical, they are very accurate predictions and if OP builds something that was simulated properly and he measures it outside, the sim will match the measurement. That's as good as you can get, unless you can predict the acoustics of the church. Good luck with that. The acoustics of your room are not even vaguely similar to the acoustics of any church, I will guarantee that, so in room measurements of your home system IN your home don't serve any purpose at all.
Suggesting that people should include their own in room measurements of their own gear is ridiculous. To what end? No one here owns the OP's driver, no one has a similar box, and no one lives in his church. Why on earth would anyone post in room measurements of anything?
Simulations have been proven to be very accurate on thousands of occasions. My sims are accurate. If my sims are built the measurement will match the sim.
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Of course you can play play a piece if you don't have a 32 ft stop. Most organs don't have those stops (though I wish they did) because of space and cost limits.
Now the obvious question. If you can't hear it with your ears, why do the pipes need to be tuned? I ASSURE you you would know when they aren't tuned. I most certainly can hear 16 Hz and it's a wonderful sound.
G²
Can you hear 16 hz sine wave (and if so, in what setting?) , or can you hear an organ pipe with a 16Hz fundamentaL, as they are not the same thing
If that question is open to everyone, my personal answer is yes to both. The organ pipe is perhaps a little easier to pick out due to overtones, but I can easily hear 16 cycles coming out of a tone generator, even at pretty low volumes, where the signal present indicators on my subwoofer amplifier aren't even flickering.
Couldn't be an open baffle-like arrangement used, where the baffle were the ceiling, and the rear volume be the attic? Perhaps with a different driver (or rather 4 of them), having Qts around 0.7 and much higher Xmax.
Why? A real organ has wind noise . . . it's masked by "the rest of the sound". A little wind noise in a port matters not at all.
Mounting? Not an issue at all. The port tube does not have to be interior to the box (let it stick out like . . . an organ pipe), and does not require any special support. There isn't any mechanical loading from air moving back and forth in it.
6" and 8" sonotube (form tube) can be had cheap at any Home Depot. It's non-resonant, strong enough to hold concrete, and easy to mount on your existing box. Just cut it to whatever length gives the desired tuning with your existing box. For total flexibility you could put a plywood mounting flange on the end (it would then look like a top hat) and then screw it to (over) a hole in your box just like mounting a speaker or passive radiator.
For a few more dB you can add a second driver and adjust the (external) port tube length or number as necessary . . .
Stuffing in the box does nothing positive . . . just a waste of money.
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Hi lcsaszar,
That's called an infinite baffle: Home | "Cult of the Infinitely Baffled" Hear The Bass, Not The Box The definitive online resource for Infinite Baffle subwoofer design Established 1999
and, yes, that would work, but is not what the OP asked for.
Regards,
That's called an infinite baffle: Home | "Cult of the Infinitely Baffled" Hear The Bass, Not The Box The definitive online resource for Infinite Baffle subwoofer design Established 1999
and, yes, that would work, but is not what the OP asked for.
Regards,
Correct me if I'm wrong but...
That Crown XLS1500 has a high pass LR filter at 20Hz, not much point trying to get 16Hz with that non-defeatable filter pulling everything down.
Since the OP has that 15 anyway, might as well use it from 25 to 30Hz and up then make another sub with different drivers/amp tuned to 16Hz specifically. Can't use the existing amp or driver for 16Hz with any real output for a church so maybe a "one note" sub to get the output as high as possible is in order.
I'm thinking a FLH, tapped horn, tapped pipe or bandpass. A Sonotube tapped pipe design tuned to 16Hz might work if you have the space. How much SPL is required at 16Hz to fill the church? If it takes 85dB to just perceive the 16Hz note--to just notice it slightly....that would mean at a distance of say...20 meters in a large church, that is 121 dB at one meter just so a person might notice it 20 meters away (not counting for room gain etc.)
Since human hearing is not linear, we can hear 31Hz at 60dB but need 85dB to hear 16 Hz--this will get crazy quickly.
Still, a good exercise in making a sub that can do say... 16 to 25Hz at high output levels. Might be as big as a pipe organ but such is the way with LF.
That Crown XLS1500 has a high pass LR filter at 20Hz, not much point trying to get 16Hz with that non-defeatable filter pulling everything down.
Since the OP has that 15 anyway, might as well use it from 25 to 30Hz and up then make another sub with different drivers/amp tuned to 16Hz specifically. Can't use the existing amp or driver for 16Hz with any real output for a church so maybe a "one note" sub to get the output as high as possible is in order.
I'm thinking a FLH, tapped horn, tapped pipe or bandpass. A Sonotube tapped pipe design tuned to 16Hz might work if you have the space. How much SPL is required at 16Hz to fill the church? If it takes 85dB to just perceive the 16Hz note--to just notice it slightly....that would mean at a distance of say...20 meters in a large church, that is 121 dB at one meter just so a person might notice it 20 meters away (not counting for room gain etc.)
Since human hearing is not linear, we can hear 31Hz at 60dB but need 85dB to hear 16 Hz--this will get crazy quickly.
Still, a good exercise in making a sub that can do say... 16 to 25Hz at high output levels. Might be as big as a pipe organ but such is the way with LF.
Do you have a high quality recording of a 16hz organ tone? I'd like to check out the FFT
I seriously doubt that you are hearing the 16Hz (pure) tone. It's very, very likely that you are hearing the "distortion", e.g. the harmonics of the tone that are up in the hearing range.
Just a guy, First, relax. This isn't personal.🙂
I think I've followed you and I THINK I understand the graphs.
I get it. A port offers 12 db gain for almost no cost. We just don't quite agree on the ease or complexity of adding a port. That's probably just MY HANG-UP.
Here is a link to another site that includes some pics of my homemade box. They're in a post about two posts down the page (post #213). This will address the placement of the speaker you said you needed to know.
Wanted Dead or Alive (Prefer Live) - Page 22
The organ is currently only pipes. We are adding some sounds using a digital sound module. The plan is to make the pipes and speakers blend equally.
The sound module we are adding to our organ has eight audio outputs (4 stereo pairs). Different organ stops (sampled sounds) can be routed to any of these 8 audio outs. Our current plan allows two of those outputs to be dedicated solely to the organ pedals. One Crown XLS1500 will feed this box (300 watts RMS per channel). It is being run in Lowpass mode. The crossover frequency is adjustable. This will handle one of the channels from the sound module. (The other channel on that amp won't be used - unless we see a need and room to do so.
The other channel from the sound module will be routed through a Crown XLS1000 to a refurbished Allen HC12. This speaker has a 15" Eminence woofer, two Peerless 4" mid-ranges (each tuned for different frequencies) and a dome tweeter (not sure who makes the tweeter).
The other speakers in this project are all this same HC12. I've put new surrounds on all of them. We bought 10 of these for a very good price. They are very solid and sound excellent to my 65 year old ears. They can do 32 hz., but I figured a slight amount of assistance would be helpful. And they just can't quite do 16 hz. That was the purpose of building the homemade speaker we're discussing.
The thinking was to set the crossover pretty low. The HC12 can provide for much of the pedal sounds. Since the crossover frequency can easily be adjusted, I've been experimenting. Right now it is set at 167 hz. I've also tried it at 100 hz. It can be set to 60, or even 32. This adjustment is integrated into the Crown XLS1500. It provides 300 watts RMS per channel. The other four amps in the system are Crown XLS1000s. Three of these power stereo pairs for various voices from the manuals. Each has a 225 watt per channel (RMS) output.
I don't know if this is important or not, but I feel I should mention it. All the pipes on a pipe organ play at full volume all the time. Some pipes are louder than others, but they all play wide open all the time. There is a device that separates them from the listeners call the shades. Think of venetian blinds running from top to bottom - instead of horizontally. Less sound gets out of the pipe chamber when the shades are closed. More comes out (proportionally) as the width of the gaps between the shades are increased.
Now, consider the speakers. We had the option of adjusting the sound level of the various speakers electronically. But the speakers are going into a room right behind the pipes and directly across from the shades. We are going to play the speakers at full volume to match the pipes. Voicing will balance the relative input from each source. Thus, the volume of the speakers AND the pipes when the instrument is played will be set by adjusting the shades. We'll voice them so they blend well. The sound module allows us to adjust the relative volume of individual sounds that are sent to the amps and speakers. Does that make sense?
I'll have a spare HC12. One idea was to put two HC12s set above the crossover point, then have the homemade box handle everything below 100 - or whatever crossover point is selected. .
I'll again point you to a post (#198) at the organ forum that shows before-after pictures of one of the HC12 speakers. I replaced the surrounds on the woofer and the two mid-ranges.
Wanted Dead or Alive (Prefer Live) - Page 20
Since I'm a bit hung-up on the port, let me request the details. 😕 I'm assuming a 90 degree elbow goes in the 6" hole I'll need to cut in the cabinet. It will be solidly glued in place and sealed. Then a length of straight ABS pipe will be inserted into the elbow on the inside of the cabinet. More glue (pipe adhesive) will hold it in place - that's why you say no support will be needed.
tb46 suggested 17 3/4 inches for the port. You suggested a different length. I assume the elbow has to be included in determining that length.
You even hinted that there MIGHT be some advantage to a different sized port.
I am very grateful for the effort you've put into this on my behalf. If you'll nail down the final details, I'll try to follow the Rx. 😱
Bach On
I have a Great Organ at Methuen recording, and the complete 16 cd Bach Organworks (Bernard Foccroulle) that I could look through, but the desire to pick them apart with adobe audition escapes me at the moment.
That's why I was very careful to point out that it's at low volume. It's actually audible in my garage some 60 feet away if I play it downstairs as well. I know it's the fundamental I'm hearing, because when the volume is raised to levels where distortion starts creeping past the single digit range, the point at which overtones take over is audible as well.
I didn't tune my current subs to 15 hz just for bragging rights 😛
Sure, sure, I have built subs tuned in the teens before:
http://audio.claub.net/image/Pic8.png
http://audio.claub.net/image/Pic9.png
This was from 2 high excursion 12" subs and an 18" PR. The SPL level is not accurate and was probably only about 85dB but it's producing about 15Hz at 3% distortion. That's just not loud or clean enough to hear the fundamental.
I'll only believe that when you post a distortion measurement. Use whatever SPL you would like. Even better would be a spectrum that shows that amplitude (in SPL) of each harmonic. Then you need to apply the "hearing curve" which is the sensitivity of the ear to the spectrum to get the "perceived loudness" of each tone. Unless you have very, very low distortion - something that is very difficult to achieve when reproducing 16Hz at an SPL that could possibly be "heard" - you will primarily be "hearing" the overtones. The brain actually reconstructs these into a "phantom" lower tone sometimes. This fact has been used in at least one commercial product to "generate" bass sounds when the speaker can't reproduce them due to lack of low frequency output (this is usually applied to a very small speaker).
There are a number of misconceptions appearing in DrDyna's post which show up in various forms in posts in this thread.
First, unless DrDyna is using direct electric brain stimulation, he is listening to his tone generator (or organ recording) through some speakers. Given how steep the Fletcher-Munson curve is, even a little bit of harmonic distortion will far more audible than the fundamental. Speakers at low freq produce lots of distortion.
And the effect is far more insidious at low volumes, if you can picture the F-M curves.
Further, the brain re-creates the fundamental tone from the overtones and you "hear" it (or in more precise language that is less ambiguous than re-using the word "hear", you "perceive" it). I know that's a concept that doesn't feel right to persons of an engineering disposition but it is true anyway.
Same is true when you're listening to an organ although the harmonics wouldn't be considered distortion, of course. Anybody had a look at the speakers organ manufacturers use? You'd toss 'em out on garbage day. When the old Hammond is playing real low notes, do you actually think those pieces of junk are putting out anything much below 40 Hz?
When a very low pipe is being played from an organ (and it is rare for any single pipe to be speaking), you experience a whole range of sensations: body shakes, floor shakes, room buzzes, seeing the organist in funny narrow shoes pressing the pedals (or even shoeless), the compressor vibrating in the cellar (perhaps around 1560 RPM... got that?), and something which seems to be entering our brains by way of our ears. And it isn't clear what a mic would pick up since the sound is full of all kinds of tones.
So when you go to hear a big organ, OK to say, "I heard the 64 foot pipe..." but not OK to say I heard 16 Hz.
(I hope you've had a chance to see my thread about the annual organ Halloween bash in Toronto.)
Ben
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Here's where I run into an issue with this. I fully understand everything that you're saying, and agree with most of it, but at the same time, I do not believe that everyone's inner ear is biologically identical to the point where everyone's perception matches db for db to the point where we can apply a chart. It might apply in a general sense, but what I reject is the notion that we're 100% certain a person can't hear something because of a weighting chart that says they can't.
Maybe all I've heard is distortion all my life, or it's my brain filling stuff in, or whatever the logic might be, all I know is, if I fire up a tone generator in rew and tell it 16 cycles, with the volume at -45, I can hear it in the room, all the way down the hall, up the stairs, and out into the garage, and the tonality doesn't change much until I raise the volume to the point where windows and doors are violently clacking in their frames.
I guess I can do some measurements later, but it'll have to wait, I have a toddler to care for until around 5 pm.
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