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Post by geebo on Aug 8, 2013 8:52:15 GMT -5
Geebo wrote: "But I think the pressures generated by a subwoofer would act along the diameter of the cylinder. Much like you would expect by connecting an air hose at one end and pumping air into it. It would bulge outward. Now to what you said, yes, it's very strong along the length of the cylinder to the point even a big guy like me can stand on one end and not phase it. "" Geebo, think about what you just wrote. Go ahead and pump air into a cylinder and see how much flexing you get. Same thing with standing on it, you can put massive weight on it with no deformation. You guys are stressing over a non-issue... -RW- Lay the bucket on it's side and stand on it. It will flex like crazy. |
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Post by mgbpuff on Aug 8, 2013 8:54:42 GMT -5
'Garbage in, garbage out' comes to mind!!  |
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Post by saarg on Aug 8, 2013 8:56:29 GMT -5
@rlw
Could you please explain why the pressure is not making the walls of the bucket flex? If all the pressure is on the top of the bucket, I understand, but I do not see how air pressure inside the bucket is the same as putting weight on top of the bucket.
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bootman
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Post by bootman on Aug 8, 2013 8:57:37 GMT -5
Geebo wrote: "But I think the pressures generated by a subwoofer would act along the diameter of the cylinder. Much like you would expect by connecting an air hose at one end and pumping air into it. It would bulge outward. Now to what you said, yes, it's very strong along the length of the cylinder to the point even a big guy like me can stand on one end and not phase it. "" Geebo, think about what you just wrote. Go ahead and pump air into a cylinder and see how much flexing you get. Same thing with standing on it, you can put massive weight on it with no deformation. You guys are stressing over a non-issue... -RW- Lay the bucket on it's side and stand on it. It will flex like crazy. What sub and amp combo can exert that much pressure? Not really a fair comparison, no? |
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Post by pedrocols on Aug 8, 2013 9:01:42 GMT -5
Pedro, remember that the $500 includes 2 hi-powered amps. And the build is a doddle, two subs could easily be done in 4-5 hours. Stop with the negative waves, Moriarty...<g> -RW- Yes. My name is Pedro nice to meet you  |
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bootman
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Post by bootman on Aug 8, 2013 9:07:53 GMT -5
Think about it this way.
How much pressure do you think it takes to raise 1 inch circular column of mercury of 1 inch in height?
Is that enough "force" to flex a bucket?
The answer is about .5 lbs per square inch. (1/2 not 5!)
I doubt the bucket would care.
Now why is this important?
It takes about 165dB of sound pressure to do this.
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Post by geebo on Aug 8, 2013 9:13:15 GMT -5
Lay the bucket on it's side and stand on it. It will flex like crazy. What sub and amp combo can exert that much pressure? Not really a fair comparison, no? Yes, I can see how it wouldn't take much to make the bucket vibrate. Maybe not visibly so but enough that it could be felt and create it's own sound. Do you think a cylinder made of flexible plastic would be ideal for a woofer? |
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bootman
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Post by bootman on Aug 8, 2013 9:16:03 GMT -5
What sub and amp combo can exert that much pressure? Not really a fair comparison, no? Yes, I can see how it wouldn't take much to make the bucket vibrate. Maybe not visibly so but enough that it could be felt and create it's own sound. Do you think a cylinder made of flexible plastic would be ideal for a woofer? Different question! I don't know what the resonant freq of a plastic bucket would be. If it is outside of the sub range then I don't see why it would not work. |
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Post by siggie on Aug 8, 2013 9:19:17 GMT -5
I'm no expert on physics or speakers, but I'm pretty familiar with 5 gallon buckets. They are strong, thick plastic. If the pressure is coming from the inside, it seems to me that it would be pushing outward on all points in the cylinder at the same time so that, unless the plastic stretches, there would be no movement.
I'm wondering whether it would work to run an RCA from the sub out on my receiver to a full range amp and then hook a bucket sub or two to the speaker outputs without the need for a crossover.
I've been looking for an excuse to take advantage of the Sherbourn clearance sale. What do you guys think of using the 4Z-75 2-Channel, 4-Zone Amplifier to run a couple of bucket subs? Also, any opinions on whether it would be better to run 2 or 4 bucket subs with that amp. (If this works, and you were lucky enough to get the monster 7 channel Sherbourn, you could run 7 bucket subs, and you could play them as loud as you want because your wife would divorce you!)
Here are the specs on the Sherbourn 4Z-75:
Speaker outputs:
8 pairs of full-sized five-way binding posts (one pair for each channel in each zone; Channel 1, zones 1-4 and Channel 2, zones 1-4).
Minimum recommended load impedance:
ANY combination that totals 2 ohms or higher per channel.
Power output:
95 watts RMS per channel (x2); into 8 ohms. 150 watts RMS per channel (x2); into 4 ohms. 270 watts RMS per channel (x2); into 2 ohms.
Thanks,
Siggie
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Post by geebo on Aug 8, 2013 9:26:36 GMT -5
Yes, I can see how it wouldn't take much to make the bucket vibrate. Maybe not visibly so but enough that it could be felt and create it's own sound. Do you think a cylinder made of flexible plastic would be ideal for a woofer? Different question! I don't know what the resonant freq of a plastic bucket would be. If it is outside of the sub range then I don't see why it would not work. I'm not an engineer, but I don't think you'd necessarily have to reach a resonant frequency. That would be the point of the greatest amount of deformation. But rapidly compressing and decompressing the air inside a plastic cylinder would make it flex a bit at whatever frequency the compression and decompression is occurring. I think the goal for a subwoofer would be no flex or vibration of any kind. |
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DYohn
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Post by DYohn on Aug 8, 2013 9:29:27 GMT -5
While Keith is absolutely correct that plastic can be a terrible material for a subwoofer enclosure because it can stretch (thus rendering the mechanical strength of the cylindrical shape moot) the reason this works is because it's made from one of these:  not one of these:  So the material has plenty of longitudinal stiffness. |
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Post by mgbpuff on Aug 8, 2013 9:39:13 GMT -5
Ever seen a silent drum?
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bootman
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Post by bootman on Aug 8, 2013 9:55:12 GMT -5
The drum head here is the speaker driver no? Roughly 80% of the sound. (in this case maybe a bit more) |
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Post by mgbpuff on Aug 8, 2013 9:59:18 GMT -5
How about a snare drum - the sides vibrate - no?
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Post by bootman on Aug 8, 2013 10:11:37 GMT -5
How about a snare drum - the sides vibrate - no? But that is a double headed design. Nothing like this. and the vast majority of any drum is still the heads, not the body. (for the most part unless designed that way) While I haven't done any measurements, I think this design should work. Ugly as hell but that is another topic.  |
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Post by mgbpuff on Aug 8, 2013 10:14:52 GMT -5
Stick your head in a bucket and yell - your voice will not sound natural! |
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Post by mgbpuff on Aug 8, 2013 10:16:12 GMT -5
Hey, I'm just having fun with the idea, I hope it works out for you guys!
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bootman
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Post by bootman on Aug 8, 2013 10:17:31 GMT -5
Stick your head in a bucket and yell - your voice will not sound natural! But it won't flex the bucket! and all drivers sound different in free air vs in an enclosure anyway. |
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Post by bootman on Aug 8, 2013 10:18:20 GMT -5
Hey, I'm just having fun with the idea, I hope it works out for you guys! This IS fun. |
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Post by geebo on Aug 8, 2013 10:29:01 GMT -5
How about a snare drum - the sides vibrate - no? But that is a double headed design. Nothing like this. and the vast majority of any drum is still the heads, not the body. (for the most part unless designed that way) While I haven't done any measurements, I think this design should work. Ugly as hell but that is another topic. I don't think many quality drums are made of flexible plastic. |
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