Without knowing anything about the space (the interior of the church) or the current spl level at 16 hz (he has to stand right in front of it in a quiet empty church and put his hand on it to even perceive 16 hz) how do you know how many more speakers are required? I think it's going to be a lot more than 3.
The Thigpen Rotary Woofer hardly can be described as a mass-producted subwoofer.
Yes, not exactly a dimmer switch.
As far as I know, holder of the patent can sue everyone who illegally use the patented idea, even when it is used for personal pleasure. But do not fear for that, Mr. Thigpen is genuinely nice guy (knowledgeable, too), as I can personally confirm - I had a pleasure to meet him and talk to him, and to see and hear (feel) the Rotary Subwoofer.
Embrace the fact that Mr. Thigpen invented very cool subwoofer. Inventor has all the rights to earn some money from his patented idea. 20 years after the patent date, it is all yours and you can sell the same subwoofer, but I deeply suspect that you can sell it for 1500 and have a profit.
The enclosure of the TRW I saw was about the size of two conventional subs with double 18" woofers.
1/3 hp motor is only 250W. Four 18" woofers need a 4000W amplifier to be anywhere near to TRW.
Direct contact with fane blades is impossible, as I saw.
I was simulating some dual chamber vented designs with the parameters of your Dayton woofer. A decent 6th order bandpass design should be possible, with response of 15Hz-68Hz, and you may be able to use your original 12 cubic foot box for one of the chambers. You will sacrifice about 3dB of sensitivity to get this response.
Front chamber: 2.1 cubic ft. tuned to 40 Hz
Rear chamber: 12 cubic ft. tuned to 15 Hz
You can check this out for yourself if you have WinISD or other box simulation software which can calculate a 6th order bandpass response.
Maximum SPL will be limited by cone excursion excursion in the 20Hz region, about 104dB. A 16Hz tone will not reach the excursion limit until 107dB.
Front chamber: 2.1 cubic ft. tuned to 40 Hz
Rear chamber: 12 cubic ft. tuned to 15 Hz
You can check this out for yourself if you have WinISD or other box simulation software which can calculate a 6th order bandpass response.
Maximum SPL will be limited by cone excursion excursion in the 20Hz region, about 104dB. A 16Hz tone will not reach the excursion limit until 107dB.
I know that, but why not? Raise production, sell more at a lower price. That's how the rest of the world works.
No I'm almost 100 percent certain anyone can use any patented idea for personal use and experimentation. That's the whole idea of the patent system, to get ideas out for people to use and improve on while providing a limited amount of intellectual property protection if you are lucky enough to be rich enough to enforce it yourself legally.
You have a $100 electric motor, a $50 speaker motor and a few custom parts that are essentially a heli rotor / swashplate assembly and a few blades. If you can't make a profit selling those parts for $1500 you shouldn't be in any kind of business.
All the ones I've seen are bigger. Still, 2 conventional dual 18 subs are pretty big and I can make manifolds for twenty 18 inch drivers a lot smaller.
250 watts CONSTANTLY. That fan is ALWAYS spinning at full speed regardless of whether there's bass content in the signal or not. Conventional woofers/amps only put out significant power when there's bass in the signal. This is a math problem where you have to factor in duty cycle, it's not a simple comparison of how many watts each system can output.
A 14000 watt amp is $1000 delivered to your door these day, no tax. So what if 4 conventional woofers need a 4000w amp?
Don't forget that the fan sub need a WHOLE OTHER sub system to cover from 30 hz up to the mains crossover point. That's more conventional woofers and amps that you need, extra crossovers, extra boxes, more money. So the fun doesn't stop at $26000, that's only the start. AND a single fan sub really isn't that loud or impressive. 115 db in room isn't really anything to brag about.
There's nothing you can say that can justify the cost, danger and size of this fan sub compared to conventional subs. Cost is the big issue though, if it were a reasonable cost everything else could be forgiven. How do you even begin to justify consulting engineer fees, employee plane ticket fees to your house when they don't do anything but call a contractor to install the system, which you also pay for? This is ultimate stupidity and waste.
I can show you a pile of pics and videos that show it's VERY possible to achieve direct contact with the blades. In the video I just linked to you could easily stick your head right in it like an oversized blender or a wood chipper. And the unit does not look very stable either, it's entirely possible the whole thing could fly apart. The guys in the video even commented on this possibility because it looks and sounds so incredibly unsafe.
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That JBL is likely NOT very good at reproducing 16Hz, no matter what the enclosure type. The Fs is about an octave higher, so output from the driver at 16Hz is very limited.
A driver with a lower Fs is needed here.
Is is not that simple, especially for a small company.
You are wrong, see this
ESP - Patents
section
But What About Me? I'm just a DIY End-user. They won't sue me, will they?
Article is written by Ian Millar, Registered Patent Attorney.
Try it, after the patent elapsed. I wish you a big success, honestly.
At no audio signal, fans are not pushing air, so there is no load - motor speed is maximum with much less than 250W.
Buying in bulk and producing parts in bulk is something even a small company can do. It's something I can do. When I buy passive crossover components I buy 100 at a time. If I was selling something that needed custom parts I would make (or have made) at least 100 at a time. It really is that simple, even for a small company.
A quick search reveals that technically you are correct. There is no formal fair use policy. But it happens all the time and there's a wealth or articles and justifications and defenses available like this one - Experimental Use Or Fair Use As A Defense Against Patent Infringement -
http://ipmall.info/hosted_resources/IDEA/p243.Grossman.pdf
You definitely are allowed to improve on patents and submit your own patent application for the new product, how can you do that without infringing on the previous patent? You can't, but it's allowed.
Also it's very clear that no one sues for diy patent infringement and very rarely for experimental use. If they did everyone that has ever posted a tapped horn simulation is guilty of “secondarily liable” for patent infringement and you can be liable for inducing someone else to infringe, and anyone that builds your sim is guilty of patent violation.
Do you see Danley suing? No, and they are very interested in suing people. They have publicly stated that they are going to go after anyone profiting on their patented concepts, including people renting out their speakers.
It just doesn't happen. DIY'ers don't get sued.
I have no interest in producing or selling this product. Isn't that clear? It's a huge liability issue, basically a huge open blender in a domestic situation. I've attempted to diy one and would run one in my home if it was a reasonable price but there's no way I would want any of the liability concerns that would come from selling them.
Even under no load a 1/3 hp motor spinning at full tilt still draws a LOT more power than an amp at idle. Do the math if you want but the conventional system is always going to draw less power on average (less electricity bill) unless you like playing steady sine waves at or below 30 hz.
Seriously though, is electricity bill really an issue here? How much does even a huge system cost to run? Really not that much.
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Hi CharlieLaub,
Post #46: "...That JBL is likely NOT very good at reproducing 16Hz, no matter what the enclosure type..."
Petter Persson's Kraken 2x12"TH: http://www.diyaudio.com/forums/subwoofers/160879-build-your-own-2x12-th-kraken-212-th.html
Even without modifications this dual driver TH will get you there. It does not take a lot of imagination to see what needs to be done to get a bit lower. Naturally, its Vnet is already 577L, and even modified it will not be easy to get it below 450L (or so).
In the spirit of blue skying I was just pointing out a good buy. I just noticed, that the 15" version is also for sale @ ~ $150.-- for a pair. They would even work as is in the OP's box. TC Sounds VMP 15" passive radiators cost $165.-- ea.
Regards,
Post #46: "...That JBL is likely NOT very good at reproducing 16Hz, no matter what the enclosure type..."
Petter Persson's Kraken 2x12"TH: http://www.diyaudio.com/forums/subwoofers/160879-build-your-own-2x12-th-kraken-212-th.html
Even without modifications this dual driver TH will get you there. It does not take a lot of imagination to see what needs to be done to get a bit lower. Naturally, its Vnet is already 577L, and even modified it will not be easy to get it below 450L (or so).
In the spirit of blue skying I was just pointing out a good buy. I just noticed, that the 15" version is also for sale @ ~ $150.-- for a pair. They would even work as is in the OP's box. TC Sounds VMP 15" passive radiators cost $165.-- ea.
Regards,
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very poor advice. I am ashamed . It does not help you to advice about ports or passive radiators if you are not told how to design such . It can make matters worse .
If your speakers already go to twenty Hz then just use an equalizer to go to 16 Hz
Forget all the advice about special drivers and ports. They need special design.
If you really want a special design then start a new thread about specific design .
If your speakers already go to twenty Hz then just use an equalizer to go to 16 Hz
Forget all the advice about special drivers and ports. They need special design.
If you really want a special design then start a new thread about specific design .
Your shame amuses me.
It's trivially easy to design a ported box tuned to 16 hz. OP has not decided on a course of action and so no specific designs have been presented.
Advising OP to use an eq'ed sealed box when that clearly is not working is very poor advice. Read his comments. In a quiet empty church he needs to stand right in front of it and put his hand on it to perceive 16 hz at all. Does that sound like it's working out well to you? You think a bit of eq is going to make him happy?
Ok let's take a step back and get our shameful emotions under control and look at this from a scientific perspective instead of throwing around useless opinions.
This forum is supposed to be about science and this subforum in particular has deep roots in pro sound so I have no idea what's going on here with the sealed box recommendations. Sealed boxes have no place in pro sound unless you are rich and this is most definitely a pro sound application.
First this is a sim of the OP's current sealed box. Not sure on dimensions so internal resonances are masked. Since budget seems to be a big concern I showed these at what I'm guessing is xlim, a bit more than double xmax. (Xlim is the point where the driver physically breaks, OP, not a good idea to push things this far but this is absolutely maximum potential.)
The ONLY thing that's important is spl and excursion at 16 hz. We're looking at about 100 db max. At 16 hz that is not perceptible, that matches OP's comments that he cannot perceive it unless he stands in front of it and touches the box.
That's 100 db max, you can't eq that up. You can eq the higher frequencies down but you can never have more than 100 db max from this thing and that's at the breaking point, not at xmax.
Since sound decays at 6 db per doubling of distance (which isn't exactly true inside a building but let's go with it) we're down to 76 db at 16 meters, which probably isn't even the far side of the church. 76 db at 16 hz is beyond inaudible, it's completely imperceptible, it's not even worth trying if that's the best you can do.
So now let's use the same box and double up the drivers.
Now we're up to 105 db at 16 hz and it cost $130 for the extra driver and we had to more than double the power. 5 extra db isn't much.
Now let's use the same box with only 1 driver and add a port. Still don't know box dimensions so box resonances are masked.
The port is 200 sq cm and 60.5 cm long. Velocity is around 26 m/s at 16 hz which is a bit high, but people complain about big ports so I showed a compromise. I'd like to see a bigger port (or collection of smaller ports with greater cross sectional area) to reduce velocity even more.
NOW we've got 112 db at 16 hz. That's 12 db more than the single driver sealed box and 7 db more than the dual driver sealed box. And it cost nothing but a simple mod. (I'm assuming everyone can access a few scraps of wood or abs pipe for no cost.)
12 db is more than a doubling of perceived volume.
At this point is anyone really going to argue that sealed is a better choice? It took me 36 seconds to sim that ported box, it doesn't cost anything to retrofit the port and it gains 12 db over the single driver sealed box, whereas adding another driver to the sealed box and more than doubling the power input only gained 5 db over the single driver and 7 db less than the single driver ported box.
Just add the port, and then add more ported boxes until 16 hz shakes your eyeballs at the back of the church.
I didn't show any of these sims with filters, assuming 16 hz is the lowest note that will ever be played a hpf is not mandatory but still a VERY good idea. Power is not a problem with any of these sims, the ported box consumed the most power to hit xmax and it's only 300 watts. No room gain is shown or assumed, a large building like this might be hard to pressurize so no room gain can be expected. If there is any it's a bonus.
Science people. Put away your opinions and your shame and show scientific results. When a new guest asks for advice think before you speak.
This forum is supposed to be about science and this subforum in particular has deep roots in pro sound so I have no idea what's going on here with the sealed box recommendations. Sealed boxes have no place in pro sound unless you are rich and this is most definitely a pro sound application.
First this is a sim of the OP's current sealed box. Not sure on dimensions so internal resonances are masked. Since budget seems to be a big concern I showed these at what I'm guessing is xlim, a bit more than double xmax. (Xlim is the point where the driver physically breaks, OP, not a good idea to push things this far but this is absolutely maximum potential.)
An externally hosted image should be here but it was not working when we last tested it.
The ONLY thing that's important is spl and excursion at 16 hz. We're looking at about 100 db max. At 16 hz that is not perceptible, that matches OP's comments that he cannot perceive it unless he stands in front of it and touches the box.
That's 100 db max, you can't eq that up. You can eq the higher frequencies down but you can never have more than 100 db max from this thing and that's at the breaking point, not at xmax.
Since sound decays at 6 db per doubling of distance (which isn't exactly true inside a building but let's go with it) we're down to 76 db at 16 meters, which probably isn't even the far side of the church. 76 db at 16 hz is beyond inaudible, it's completely imperceptible, it's not even worth trying if that's the best you can do.
So now let's use the same box and double up the drivers.
An externally hosted image should be here but it was not working when we last tested it.
Now we're up to 105 db at 16 hz and it cost $130 for the extra driver and we had to more than double the power. 5 extra db isn't much.
Now let's use the same box with only 1 driver and add a port. Still don't know box dimensions so box resonances are masked.
An externally hosted image should be here but it was not working when we last tested it.
The port is 200 sq cm and 60.5 cm long. Velocity is around 26 m/s at 16 hz which is a bit high, but people complain about big ports so I showed a compromise. I'd like to see a bigger port (or collection of smaller ports with greater cross sectional area) to reduce velocity even more.
NOW we've got 112 db at 16 hz. That's 12 db more than the single driver sealed box and 7 db more than the dual driver sealed box. And it cost nothing but a simple mod. (I'm assuming everyone can access a few scraps of wood or abs pipe for no cost.)
12 db is more than a doubling of perceived volume.
At this point is anyone really going to argue that sealed is a better choice? It took me 36 seconds to sim that ported box, it doesn't cost anything to retrofit the port and it gains 12 db over the single driver sealed box, whereas adding another driver to the sealed box and more than doubling the power input only gained 5 db over the single driver and 7 db less than the single driver ported box.
Just add the port, and then add more ported boxes until 16 hz shakes your eyeballs at the back of the church.
I didn't show any of these sims with filters, assuming 16 hz is the lowest note that will ever be played a hpf is not mandatory but still a VERY good idea. Power is not a problem with any of these sims, the ported box consumed the most power to hit xmax and it's only 300 watts. No room gain is shown or assumed, a large building like this might be hard to pressurize so no room gain can be expected. If there is any it's a bonus.
Science people. Put away your opinions and your shame and show scientific results. When a new guest asks for advice think before you speak.
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One of your recommendations - and that of some others - is adding two 6" ports 35" long. But you warn that "there will be a strong delay peak around the vented tuning frequency, AND there will be strong pipe resonances from the tuning ducts".
Another suggestion - again made by several - is to add another driver. It provides more cone area to create more sound and it lowers the ohms and increases watts to the box from the amp.
Another warns that this will work against getting low sounds from the box.
You also warn that a high pass will be needed to limit over excursion with either method.
I'd previously read that passive radiators need to be larger than the active speaker - but that it is OK to use more than one PR to achieve that. I'd previously read 20-25%. But one poster said the PR must be TWICE the area of the speaker. I've never read that rule of thumb anywhere else.
So, here is a proposed plan:
1. Install another identical 15" speaker below the first one.
2. Wire it in parallel with the first one.
3. Install two Dayton 12 inch resonators on the left wall.
4. Install two more Dayton 12 inch radiators on the right wall.
5. I add more damping material.
6. Run calculations to determine weight to be attached to the passive radiators.
This increases cone area and increases watts going to the box.
It eliminates one of the problems you warned me that would result due to the ports.
The passive radiators - if weighted properly -will serve to restrain cone excursion.
Some EQ and other processing might need to be considered. But I'm focused on a single cabinet now.
We won't have room for a wall of bass speakers. It's going to be a challenge to get the 8 speakers we have in our speaker chamber. We also won't be buying a Thigpen Rotary Subwoofer. Whether we can save money by installing it ourselves doesn't matter. We can't afford it and we don't have room for it. 🙄
We can get the 12" passive radiators for about $35 each - that's as cheap as I've seen. Moving to a 15" will cost $155 each. An 18" is over $265 each.
I'll open the floor for opposing thoughts or refinements.
Bach On
Group delay and port resonances are NOT a problem. You want a design? I can make you a design. It's really so simple.
Look at the graphs I just posted. If your amp can put out 300 watts into 5.8 ohms you don't need to increase watts or lower ohms.
Another driver is NOT as effective as adding a port. You would have to add 3 more drivers and more than 3x more power to be as effective as adding 1 port.
Look at the graphs I just posted. You can gain 5 db if you add another driver and supply them more than double the power. You can gain 12 db if you add just a single port.
If you can absolutely guarantee that the cab will never see anything under 16 hz, and there will never be any mistakes like someone tripping on the cable and pulling it out of the box and sending a wild signal to the drivers, then you don't really need a high pass filter. But it is a very good idea. I wouldn't run without one. But I presume you don't have one right now, and since your box is still operational, clearly it isn't an absolute necessity.
There is no size requirement for passive radiators. It's a volume displacement requirement. You could use a single 24 inch passive radiator with little excursion capability, or you could use a couple dozen 6 inch passive radiators or a single passive with very high displacement capability. The only requirement is that your chosen passive radiator(s) can handle the amount of weight it takes to tune them to 16 hz.
BUT a passive radiator does the same thing as a port. Ports are free. Passive radiators are very expensive. So you choose.
IMO this is a terrible plan. Just add a port to your existing box. It's free and gains you 12 db. Your plan is EXTREMELY expensive and will gain you roughly 12 db. 4 Dayton 12 inch passive radiators are not nearly enough, you'd need probably 8 of them or more (that's just a guess but 4 is not even close to enough) if you put dual drivers in that box. But with 8 passives (or more) AND another driver AND 600 - 700 watts you could probably gain 18 db or so.
So compare that. A simple port in your existing box gains 12 db. An extra driver and 8 (or possibly more) passive radiators and feeding the box 600 or 700 watts gains about 18 db, maybe a bit less because dual drivers in the box will make the low end droop a bit.
Ports are free. The only reason to use passives is when you need a small box size. Your box is already really big.
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I know it's hard to figure out who knows what they are talking about and who doesn't. But it's pretty easy to ignore everything except the science and the numbers. That's what I suggest you do. Nobody here is ever going to agree for some reason, even though this is just a simple numbers game.
First, I had not seen your post with the charts when I posted my last post.
Second, let me give you more data on the box. I have a pic, but this site doesn't allow direct uploads from my computer.
The front face is 24 inches wide and 48 inches high,. The the rear panel is identical. The side panels are 22 1/2" wide by 48" high. The top and bottom are 24 x 24 inch squares. The box is glued and screwed together Every joint is reenforced (glued and screwed) and sealed with silicone caulk to eliminate leaks. The only way to gain access the interior is to remove the speaker and use the resulting hole.Currently, there are no noises coming from the box.
What I saw one person suggest was two 6" ports 35" long. I can cut two 6" holes in the face - or the rear - if I avoid the interior wooden structural members. I'm guessing that the port can be positioned on any of the 48' high pieces,
I would have to work out some sort of interior support system for those two ducts so they did not become sources of noise. Too, I worry about port noise.
Finally, what about excessive cone excursion? I suspect it would be more likely in a ported box.
The truth is that I don't know you or anyone else here. But I know enough about carpentry that adding two ports - though it will be cheap - is not a walk in the park.😕
Bach On
f.
Ports may be inexpensive, but when you have very low tuning that requires very long ports (many times the port diameter) then you WILL have audible resonances at higher frequencies. Since the 16Hz tone will be difficult to detect anyway, even low SPL "noises" are readily apparent. This is where a PR is superior. No noises. But expensive. Luckily the box can be similar with both, meaning that you could try it with a vent and if the noises are objectionable but the performance is satisfactory otherwise you can "upgrade" the box with PRs with the mass that is needed to equal the tuning of the port and remove the port alltogether.
I would caution you against just putting more drivers in a given box. This means there is half as much "volume" per driver (going from 1 to 2 drivers) and this influences the frequency response by making Q and Fb higher. I would definitely model it before adding drivers. You may find that the SPL at some low frequencies is not increased because of the change in the overall frequency response.
I would caution you against just putting more drivers in a given box. This means there is half as much "volume" per driver (going from 1 to 2 drivers) and this influences the frequency response by making Q and Fb higher. I would definitely model it before adding drivers. You may find that the SPL at some low frequencies is not increased because of the change in the overall frequency response.
So, many views have been aired including good sense from the OP. I'd like to suggest a practical course of action which - oddly enough - resembles a system I run sometimes.
First of all, that nice woofer in your nice box (esp after adding stuffing and a leak) will be pretty good at providing a resonant sound in the bottom octave.... where resonance isn't a bad sonic quality but only a mechanically risky issue. I can't say if this will be loud enough, but it sure is as close as you will come as easily.
Next - easy to do - you just make a system that work from maybe 30 or so Hz and up. I'm lucky to have a Klipschorn and nothing could possibly make more sense for a church-scale setting or a movie theatre. I used to say there's just no other way to create that much sonic air motion "breeze" when the low freq of CDs showed up in our houses. But lots of other ways to generate lots of bass if you needn't go super low.
Now you'll need a digital crossover with many tricks and for $150, you can buy a Behringer (everybody should).
Amps are cheap second hand, and power requirements are greatly lessened when you cut up the freq compass they have to handle. Go to the Salvation Army. Opting for high-end amps and crossovers and cutting corners on speakers make no sense to me when the aural incremental advantages in expensive amps is hard to demonstrate.
Below are two pictures. First a giant open baffle with a 60 year old woofer with a 20 Hz resonance, like yours. Next is that speaker mixed with my Klipschorn in my little quirky room. For sure, purist won't know what to make of this.... but it sure sounds nice on organ music and side drums on the rare occasions the OB is called on to speak (as indicated - exactly - by the LEDs on the OB Behringer channel). (If anybody wants to chime in here, I hope they'll post MEASUREMENTS made in their listening room instead of theoretical sim curves.)
Ben
First of all, that nice woofer in your nice box (esp after adding stuffing and a leak) will be pretty good at providing a resonant sound in the bottom octave.... where resonance isn't a bad sonic quality but only a mechanically risky issue. I can't say if this will be loud enough, but it sure is as close as you will come as easily.
Next - easy to do - you just make a system that work from maybe 30 or so Hz and up. I'm lucky to have a Klipschorn and nothing could possibly make more sense for a church-scale setting or a movie theatre. I used to say there's just no other way to create that much sonic air motion "breeze" when the low freq of CDs showed up in our houses. But lots of other ways to generate lots of bass if you needn't go super low.
Now you'll need a digital crossover with many tricks and for $150, you can buy a Behringer (everybody should).
Amps are cheap second hand, and power requirements are greatly lessened when you cut up the freq compass they have to handle. Go to the Salvation Army. Opting for high-end amps and crossovers and cutting corners on speakers make no sense to me when the aural incremental advantages in expensive amps is hard to demonstrate.
Below are two pictures. First a giant open baffle with a 60 year old woofer with a 20 Hz resonance, like yours. Next is that speaker mixed with my Klipschorn in my little quirky room. For sure, purist won't know what to make of this.... but it sure sounds nice on organ music and side drums on the rare occasions the OB is called on to speak (as indicated - exactly - by the LEDs on the OB Behringer channel). (If anybody wants to chime in here, I hope they'll post MEASUREMENTS made in their listening room instead of theoretical sim curves.)
Ben
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No, I am not proposing buying the Thigpen Rotary Woofer, I was just upset by a harsh tone of the member just a guy (i.e. bashing Mr. Thigpen).
My recommendation: install two tube ports in the box and check if it resonates at 16 Hz (driver cone excursion is at minimum). If it is OK, but not loud enough, than add a second 15" Dayton. But I am afraid it will not be loud enough with two drivers either. Do not put more than two 15" in that box.
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