I hope this helps...
GLOSSARY
ATCR tube area to cone area ratio (range .5 .. 1, best .5)
Distance-between-tube-openings to total tube length ratio (range .125 .. 1, best .5)
Driver Hz to low frequency Hz tuning ratio (range 2 .. 1, best 2)
Driver Qts (range .3 .. .6, best .3)
High frequency Hz tuning (low frequency tuning times 3, best 60hz)
Low frequency Hz tuning (range 20hz .. 60hz, best 20hz)
Tube Hz to length in Inches ( 13500 / <Hz> / 4 )
Tube length in inches to Hz (13500 / <length> / 4 )
EXAMPLE
Dimensions: 72” x 21” x 9”
Inner tube area: 4.5" x 8.25"
Drivers: (equivalent to 11.3” driver) Adire AV8 ( two )
ATCR: .50
Distance-between-tube-openings to total tube length ratio: .25
Driver Hz to low frequency Hz tuning ratio: 36hz / 20hz = 1.8
Driver Qts: .39
High frequency Hz tuning: 60hz
Low frequency Hz tuning: 20hz
Tube Hz to length in inches (short): 56”
Tube Hz to length in inches (long): 168”
Number of tube folds: 12
Stuffing: None
Taper: None
GLOSSARY
ATCR tube area to cone area ratio (range .5 .. 1, best .5)
Distance-between-tube-openings to total tube length ratio (range .125 .. 1, best .5)
Driver Hz to low frequency Hz tuning ratio (range 2 .. 1, best 2)
Driver Qts (range .3 .. .6, best .3)
High frequency Hz tuning (low frequency tuning times 3, best 60hz)
Low frequency Hz tuning (range 20hz .. 60hz, best 20hz)
Tube Hz to length in Inches ( 13500 / <Hz> / 4 )
Tube length in inches to Hz (13500 / <length> / 4 )
EXAMPLE
Dimensions: 72” x 21” x 9”
Inner tube area: 4.5" x 8.25"
Drivers: (equivalent to 11.3” driver) Adire AV8 ( two )
ATCR: .50
Distance-between-tube-openings to total tube length ratio: .25
Driver Hz to low frequency Hz tuning ratio: 36hz / 20hz = 1.8
Driver Qts: .39
High frequency Hz tuning: 60hz
Low frequency Hz tuning: 20hz
Tube Hz to length in inches (short): 56”
Tube Hz to length in inches (long): 168”
Number of tube folds: 12
Stuffing: None
Taper: None
BAM:
"Design a tube that is 1/2 the wavelength of the Fs of the driver. This will be the longer tube."
yes
"Then design a tube that is 1/4 the wavelength of the driver Fs. This will be the shorter of the two tubes."
Actually I think it comes out to 3/4W -- it is 1/3 the length and
3 times the Hz of the long tube.
"The direction of the driver does not matter. "
If it is folded it is a lot easier to have the rear of the driver in the short tube (for maintenance, removal, wiring, etc).
"The ratio of cone cross-sectional area to driver Sd is 0.5<x<1.0 with a ratio of 0.5 generating the flattest response and the ratio of 1.0 generating the greatest peaks in output at either end of the frequency band. (much like a 6th-order bandpass, hmm?)"
Yes -- .5 is ideal.
"The terminus of each line should be spaced on the exterior of the enclosure at least 1/8-wavelength of driver Fs to prevent booming and exaggerated output phasing problems."
DJK's interpretation is that the ideal spacing be 1/2 the total tube length. I question this for two reasons:
1. The total tube length has nothing to do with the actual Hz tuning of the system, and is therefore misleading. I propose we use the mid-point in Hz of the cannon -- which turns out to be 1/2 the long tube length.
2. The best I have been able to do, real-world design-wise, is 1/3 total length (or more appropriately 1/2 the long tube length -- what we should really be referencing).
"...a Qts in a band between 0.5 and 0.3 is more preferable"
Yes
One more thing...
I have two cannons firing in opposite directions (similar to a dipole). This really helps tame ROOM GAIN.
"Design a tube that is 1/2 the wavelength of the Fs of the driver. This will be the longer tube."
yes
"Then design a tube that is 1/4 the wavelength of the driver Fs. This will be the shorter of the two tubes."
Actually I think it comes out to 3/4W -- it is 1/3 the length and
3 times the Hz of the long tube.
"The direction of the driver does not matter. "
If it is folded it is a lot easier to have the rear of the driver in the short tube (for maintenance, removal, wiring, etc).
"The ratio of cone cross-sectional area to driver Sd is 0.5<x<1.0 with a ratio of 0.5 generating the flattest response and the ratio of 1.0 generating the greatest peaks in output at either end of the frequency band. (much like a 6th-order bandpass, hmm?)"
Yes -- .5 is ideal.
"The terminus of each line should be spaced on the exterior of the enclosure at least 1/8-wavelength of driver Fs to prevent booming and exaggerated output phasing problems."
DJK's interpretation is that the ideal spacing be 1/2 the total tube length. I question this for two reasons:
1. The total tube length has nothing to do with the actual Hz tuning of the system, and is therefore misleading. I propose we use the mid-point in Hz of the cannon -- which turns out to be 1/2 the long tube length.
2. The best I have been able to do, real-world design-wise, is 1/3 total length (or more appropriately 1/2 the long tube length -- what we should really be referencing).
"...a Qts in a band between 0.5 and 0.3 is more preferable"
Yes
One more thing...
I have two cannons firing in opposite directions (similar to a dipole). This really helps tame ROOM GAIN.
DJK:
"This is simply being expedient on their part in making the claim as broad as possible. It covers the Acoustic Wave at 1/8 exit spacing and the Sound Cannon at 1W exit spacing.
The optimum spacing for the smoothest fequency response and the highest broadband gain is 1/2W exit spacing."
Say's who? Where are you coming up with this stuff?
"This is simply being expedient on their part in making the claim as broad as possible. It covers the Acoustic Wave at 1/8 exit spacing and the Sound Cannon at 1W exit spacing.
The optimum spacing for the smoothest fequency response and the highest broadband gain is 1/2W exit spacing."
Say's who? Where are you coming up with this stuff?
Re: Theory for Kelticwizard
Drew and all the other knowledgable people here,
I am currenntly designed my home theatre / listening room and am new to this DIY speaker stuff. I am intrigued by the work you have done and am thinking of building a "cannon" for the really low end (10 to 30 Hz) and a separate sub for the normal low end (30 to 80 Hz) The driver I am doing the first calculations for is a North Creek Poseidon Front Firing woofer.
http://www.northcreekmusic.com/Drivers/Poseidon1.htm
Fs = 17 Hz
Qts = .242
My calculations yield :
Short Pipe Length = 11.1 feet or 3.3 meters
Long Pipe Length = 33.3 feet or 10.1 meters
Pipe Diameter = 8"
F3 = 6 Hz
So far so good (if I didn't make any mistakes).
Now I'd like to calculate the theorectical output values from 5 Hz to 50 Hz following your example. The problem is that I don't understand when to add the 90 and 180 degrees in the calculation. Any clarification would be greatly appreciated. My apologies if this question is not appropriate.
Ulli
DrewP said:
Drew and all the other knowledgable people here,
I am currenntly designed my home theatre / listening room and am new to this DIY speaker stuff. I am intrigued by the work you have done and am thinking of building a "cannon" for the really low end (10 to 30 Hz) and a separate sub for the normal low end (30 to 80 Hz) The driver I am doing the first calculations for is a North Creek Poseidon Front Firing woofer.
http://www.northcreekmusic.com/Drivers/Poseidon1.htm
Fs = 17 Hz
Qts = .242
My calculations yield :
Short Pipe Length = 11.1 feet or 3.3 meters
Long Pipe Length = 33.3 feet or 10.1 meters
Pipe Diameter = 8"
F3 = 6 Hz
So far so good (if I didn't make any mistakes).
Now I'd like to calculate the theorectical output values from 5 Hz to 50 Hz following your example. The problem is that I don't understand when to add the 90 and 180 degrees in the calculation. Any clarification would be greatly appreciated. My apologies if this question is not appropriate.
Ulli
Fear not, all questions are appropriate.
What you need to do is draw a sine wave on a piece of paper.
It work like this:
Normally when drawing an electrical sinewave you draw starting at the zero crossing point. What we want to draw is a sinewave that represents 100% of the drivers peak so start the wave at the top of the vertical axis. after 90 degrees you'll be at zero cross, after 180 degrees you're at negative peak, at 270 you're at zero cross, at 360 you're back at positive peak where you started.
Now, what you need to do is figure out what proportion of a 5hz wave fits into an 10.1 metre long pipe. 1 Hz has a wavelength (full cycle as you've just drawn) of 340m (give or take SFA) (sweet F all). 10 hz has a wavelenth of 34m so 5 hz has a wavelength of 68m. Your long pipe is about 53 degrees of the 5 hz sinewave. I'm guessing it'll be aroung 75% of forward output.
your short pipe is about 17 degrees of length but as it corresponds to the rear output of the driver you need to begin with a negative peak so start forn the 180 degree point. My guess is that it's around 90% of negative output.
add the two together and you get 90% - 75% or about 15% output residual. In other words, if you're pumping 100w in, youre probably getting less than 15 dBwatts of sound and as 10 W is only around twice as loud as 1 w that's not very much gain. To be fair, youre talking aboput a 5hz tone that you can't hear anyhow, that will be resulting in massive driver excursions and likely causing some major flappage of your floorboards, wall sheeting etc. (when we cranked up a 150w plate amp on my pipe at 15w you could hear the wall sheets flapping off the wall studding, good thing my SO wasn't home!)
(The above was done on a scrap bit of paper without a ruler or calculator after a couple of glasses of red wine so any errors ar e both likely and apologised for)
Hope this has answered any questions.
Drew
What you need to do is draw a sine wave on a piece of paper.
It work like this:
Normally when drawing an electrical sinewave you draw starting at the zero crossing point. What we want to draw is a sinewave that represents 100% of the drivers peak so start the wave at the top of the vertical axis. after 90 degrees you'll be at zero cross, after 180 degrees you're at negative peak, at 270 you're at zero cross, at 360 you're back at positive peak where you started.
Now, what you need to do is figure out what proportion of a 5hz wave fits into an 10.1 metre long pipe. 1 Hz has a wavelength (full cycle as you've just drawn) of 340m (give or take SFA) (sweet F all). 10 hz has a wavelenth of 34m so 5 hz has a wavelength of 68m. Your long pipe is about 53 degrees of the 5 hz sinewave. I'm guessing it'll be aroung 75% of forward output.
your short pipe is about 17 degrees of length but as it corresponds to the rear output of the driver you need to begin with a negative peak so start forn the 180 degree point. My guess is that it's around 90% of negative output.
add the two together and you get 90% - 75% or about 15% output residual. In other words, if you're pumping 100w in, youre probably getting less than 15 dBwatts of sound and as 10 W is only around twice as loud as 1 w that's not very much gain. To be fair, youre talking aboput a 5hz tone that you can't hear anyhow, that will be resulting in massive driver excursions and likely causing some major flappage of your floorboards, wall sheeting etc. (when we cranked up a 150w plate amp on my pipe at 15w you could hear the wall sheets flapping off the wall studding, good thing my SO wasn't home!)
(The above was done on a scrap bit of paper without a ruler or calculator after a couple of glasses of red wine so any errors ar e both likely and apologised for)
Hope this has answered any questions.
Drew
DrewP said:
Drew,
Thanks for the quick and detailed response. Was the wine perhaps one of the great Australian Shiraz's? They are definitely one of my favorites. Maybe I'll get some on the way home and work on my design.
I hope can impose with another quick question about the analysis of the results. I calculated the output values for frequencies between 2 and 50 Hz (see below, sorry about the formatting).
Am I correct with my interpretation that :
1) output will be out of phase below 9 Hz and above 42 Hz?
2) output is almost perfectly in phase around 25 Hz?
How does the phase behaviour of the output affect the dB values and the clarity (not that you could actually hear it)?
Long Tube (LT) Pipe Length (in) = 400.00
Short Tube (ST) Pipe Length (in) = 133.33
LT Output = sin(90+(400/wavelength)*360)
ST Output = sin(270+(133.33/wavelength)*360)
Freq Wavelength Output
(Hz) (in) LT ST Sum
2 6750.0 0.93 -0.99 -0.06
3 4500.0 0.85 -0.98 -0.13
4 3375.0 0.74 -0.97 -0.23
5 2700.0 0.60 -0.95 -0.36
6 2250.0 0.44 -0.93 -0.49
7 1928.6 0.26 -0.91 -0.64
8 1687.5 0.08 -0.88 -0.80
9 1500.0 -0.10 -0.85 -0.95
10 1350.0 -0.29 -0.81 -1.10
11 1227.3 -0.46 -0.78 -1.24
12 1125.0 -0.62 -0.74 -1.35
13 1038.5 -0.75 -0.69 -1.44
14 964.3 -0.86 -0.65 -1.51
15 900.0 -0.94 -0.60 -1.54
16 843.8 -0.99 -0.55 -1.53
17 794.1 -1.00 -0.49 -1.49
18 750.0 -0.98 -0.44 -1.42
19 710.5 -0.92 -0.38 -1.30
20 675.0 -0.84 -0.32 -1.16
21 642.9 -0.72 -0.26 -0.98
22 613.6 -0.58 -0.20 -0.78
23 587.0 -0.42 -0.14 -0.56
24 562.5 -0.24 -0.08 -0.32
25 540.0 -0.06 -0.02 -0.08
26 519.2 0.13 0.04 0.17
27 500.0 0.31 0.10 0.41
28 482.1 0.48 0.17 0.65
29 465.5 0.63 0.23 0.86
30 450.0 0.77 0.29 1.05
31 435.5 0.87 0.35 1.22
32 421.9 0.95 0.40 1.35
33 409.1 0.99 0.46 1.45
34 397.1 1.00 0.51 1.51
35 385.7 0.97 0.57 1.54
36 375.0 0.91 0.62 1.53
37 364.9 0.82 0.66 1.49
38 355.3 0.70 0.71 1.41
39 346.2 0.56 0.75 1.31
40 337.5 0.40 0.79 1.19
41 329.3 0.22 0.83 1.05
42 321.4 0.03 0.86 0.90
43 314.0 -0.15 0.89 0.74
44 306.8 -0.33 0.92 0.59
45 300.0 -0.50 0.94 0.44
46 293.5 -0.65 0.96 0.31
47 287.2 -0.78 0.97 0.19
48 281.3 -0.88 0.99 0.10
49 275.5 -0.95 0.99 0.04
50 270.0 -0.99 1.00 0.01
I'll take your word for it that the maths is ok. I could never get the formula to work out and always just cludged it graphically to get a ballpark result.
From the numbers you've supplied you're getting around 75% of the driver output in a fairly flat bandpass response from 7.5Hz to 22Hz.
Yes, you get output again further up but you have to go past the 100% null in output at 25 Hz. I'd put a 2nd order filter around there so it didn't bleed into your upper freq system
Exactly how much output the driver will be producing at that frequency is a whole nother question.
Phase behaviour seems to have very little effect on the clarity at these frequencies. you'll get more problems from rattling windows, noises produced by the sides of the tube flexing.
As with a bandpass box with the driver sealed inside, you can't easily hear sounds of drive unit distress, you'll need to be very careful abput how much power you feed in. you're talking about really huge driver excursions once you get to these kind of frequencies.
Will be awesome in action!
Drew
A good Barossa Valley Shiraz is hard to beat.
Peter Lehman, Grant Burge, St Hallet are all very nice. They go in price from fairly affordable to very pricey and from "drink now" to "hide this for 20 years".
From the numbers you've supplied you're getting around 75% of the driver output in a fairly flat bandpass response from 7.5Hz to 22Hz.
Yes, you get output again further up but you have to go past the 100% null in output at 25 Hz. I'd put a 2nd order filter around there so it didn't bleed into your upper freq system
Exactly how much output the driver will be producing at that frequency is a whole nother question.
Phase behaviour seems to have very little effect on the clarity at these frequencies. you'll get more problems from rattling windows, noises produced by the sides of the tube flexing.
As with a bandpass box with the driver sealed inside, you can't easily hear sounds of drive unit distress, you'll need to be very careful abput how much power you feed in. you're talking about really huge driver excursions once you get to these kind of frequencies.
Will be awesome in action!
Drew
A good Barossa Valley Shiraz is hard to beat.
Peter Lehman, Grant Burge, St Hallet are all very nice. They go in price from fairly affordable to very pricey and from "drink now" to "hide this for 20 years".
Will be awesome in action!
DrewP:
Hi Drew! Hope you are well (wasn't that wine rated #1?).
Ulli:
Good luck with it!
1. I know this goes without saying, but be sure your amp also goes that low (some don't).
2. As Drew mentioned, there's going to be lots of excursion going on. You might want to consider twice the number of drivers that are in your upper (30-80hz) sub -- to help out with the additional distortion down at those sub-harmonic levels.
3. I am not sure just how low special effects really go, but it sure looks like you're going to have it covered!
4. Definitely consider a steep active crossover between this unit and the 30-80hz sub. My real-world experience is that this technology, while offreing a fantiastic "bang-for-buck", has a propensity to introduce upper harmonics (above its 30hz tuning).
5. If your budget allows, go for EAS or PAM for the upper sub, for more accuracy and less group-delay.
Hope this helps!
Joe
DrewP:
Hi Drew! Hope you are well (wasn't that wine rated #1?).
Ulli:
Good luck with it!
1. I know this goes without saying, but be sure your amp also goes that low (some don't).
2. As Drew mentioned, there's going to be lots of excursion going on. You might want to consider twice the number of drivers that are in your upper (30-80hz) sub -- to help out with the additional distortion down at those sub-harmonic levels.
3. I am not sure just how low special effects really go, but it sure looks like you're going to have it covered!
4. Definitely consider a steep active crossover between this unit and the 30-80hz sub. My real-world experience is that this technology, while offreing a fantiastic "bang-for-buck", has a propensity to introduce upper harmonics (above its 30hz tuning).
5. If your budget allows, go for EAS or PAM for the upper sub, for more accuracy and less group-delay.
Hope this helps!
Joe
Re: Will be awesome in action!
Joe,
Thanks for the advice. I am planning a custom amp and crossover for this setup. Actually my electronics guru friend will be designing and building the amp and crossover. My first test unit will have a little window in the box to monitor driver excursion while feeding test frequencies.
One question. What do the abbreviations EAS and PAM stand for?
Ulli
qi said:
Joe,
Thanks for the advice. I am planning a custom amp and crossover for this setup. Actually my electronics guru friend will be designing and building the amp and crossover. My first test unit will have a little window in the box to monitor driver excursion while feeding test frequencies.
One question. What do the abbreviations EAS and PAM stand for?
Ulli
Hi Ulli...
EAS is popular with the TOP GUNS on this forum...
"Electronically Assisted Subwoofer"
Take a look here:
sound.westhost.com/project48.htm
PAM:
"Parametric Acoustic Modeling"
This MAY be the next generation version of the Acoustic Cannon (only theorizing).
There is a white paper here...
http://www.whise.com.au/index3.htm
Have fun and CHEERIO
EAS is popular with the TOP GUNS on this forum...
"Electronically Assisted Subwoofer"
Take a look here:
sound.westhost.com/project48.htm
PAM:
"Parametric Acoustic Modeling"
This MAY be the next generation version of the Acoustic Cannon (only theorizing).
There is a white paper here...
http://www.whise.com.au/index3.htm
Have fun and CHEERIO
Hi Guys,
Great thread ..i like experiments that turn out to be successful
I have a question:
It has been stated that flattest response can be had by using 0.5 ATCR.
Getting this ratio isn`t so easy unless you have a bulge in the tube and then taper it into the smaller tubes.
Is it possible to use several smaller diameter tubes to make up the required area?
Assuming a 10" drivers cone area is 53 sq in, to acheive the 0.5 ratio you`d need a tube of about 6" diameter (28.27sq in)
If you were to use say 17 x tubes 1.5" outside diameter, perhaps arranged in 2 circles of 8 tubes and one tube dead center, you`d get the correct area (26.82 sq in) but with a larger overall dia, maybe 10" (you`d have to fill in the gaps though)
The tubes could be arranged with a curvature to match the contours of the driver but keeping the overall lengths constant.
ie: concave on one side, convex on the other side.
Would multiple small tubes add more friction than one large tube of the same area? or provide a more uniform pressure overall?
In appearance i guess it`d be closer to a "Gatlin Gun" than a "cannon"
Regards Myth
Great thread ..i like experiments that turn out to be successful
I have a question:
It has been stated that flattest response can be had by using 0.5 ATCR.
Getting this ratio isn`t so easy unless you have a bulge in the tube and then taper it into the smaller tubes.
Is it possible to use several smaller diameter tubes to make up the required area?
Assuming a 10" drivers cone area is 53 sq in, to acheive the 0.5 ratio you`d need a tube of about 6" diameter (28.27sq in)
If you were to use say 17 x tubes 1.5" outside diameter, perhaps arranged in 2 circles of 8 tubes and one tube dead center, you`d get the correct area (26.82 sq in) but with a larger overall dia, maybe 10" (you`d have to fill in the gaps though)
The tubes could be arranged with a curvature to match the contours of the driver but keeping the overall lengths constant.
ie: concave on one side, convex on the other side.
Would multiple small tubes add more friction than one large tube of the same area? or provide a more uniform pressure overall?
In appearance i guess it`d be closer to a "Gatlin Gun" than a "cannon"
Regards Myth
Gatlin Gun...
Hi Myth!
It has been stated that flattest response can be had by using 0.5 ATCR. Getting this ratio isn`t so easy unless you have a bulge in the tube and then taper it into the smaller tubes.
You are correct
Is it possible to use several smaller diameter tubes to make up the required area?
Sure, go for it. It would look COOL
Also, here are two excellent examples of tuned pipes (close cousins to the cannon) that have ATCRs that are much closer to 1. That is to say -- a fully stuffed, shorter, larger diameter pipe is also an option...
http://www.teresaudio.com/haven/subs/subs.html
http://www.passdiy.com/projects/el-pipe-o-9.htm
Regards
Joe
Hi Myth!
It has been stated that flattest response can be had by using 0.5 ATCR. Getting this ratio isn`t so easy unless you have a bulge in the tube and then taper it into the smaller tubes.
You are correct
Is it possible to use several smaller diameter tubes to make up the required area?
Sure, go for it. It would look COOL
Also, here are two excellent examples of tuned pipes (close cousins to the cannon) that have ATCRs that are much closer to 1. That is to say -- a fully stuffed, shorter, larger diameter pipe is also an option...
http://www.teresaudio.com/haven/subs/subs.html
http://www.passdiy.com/projects/el-pipe-o-9.htm
Regards
Joe
From WAAAAAY back in the thread:
"The free air resonant frequency of the loudspeaker driver may be chosen to be that at which the length of the longer of the tubes is a half wavelength and thereby lessen response irregularities that might be produced by resonances between reactive components of the loudspeaker driver and the tube. Preferably, the loudspeaker driver is overdamped to avoid undesired resonances between the loudspeaker and the tube."
Straight from the R&D labs of the folks who hold the patents and designed it in the first place.
So, for my 6m long cannon with a 4.5m long, long pipe: the driver should have an Fs of around 37 Hz. Also, you want a driver with a low Qts (Driver designed for free air or ported cabinet use, not sealed box use. If it's great in a sealed box, it'll die in a cannon.)
So, low Qts, high power handling, robustly built with strong cast frame you can bolt things to sorts the driver. BUT, Fs doesn't need to be as lowas you might like
for the pipe, around 1/2 to 2/3 the cross sectional area of the driver diaphragm and build some sort of reducers in the 10 inches either side of the driver to get it to mount on the pipe.
Drew
"The free air resonant frequency of the loudspeaker driver may be chosen to be that at which the length of the longer of the tubes is a half wavelength and thereby lessen response irregularities that might be produced by resonances between reactive components of the loudspeaker driver and the tube. Preferably, the loudspeaker driver is overdamped to avoid undesired resonances between the loudspeaker and the tube."
Straight from the R&D labs of the folks who hold the patents and designed it in the first place.
So, for my 6m long cannon with a 4.5m long, long pipe: the driver should have an Fs of around 37 Hz. Also, you want a driver with a low Qts (Driver designed for free air or ported cabinet use, not sealed box use. If it's great in a sealed box, it'll die in a cannon.)
So, low Qts, high power handling, robustly built with strong cast frame you can bolt things to sorts the driver. BUT, Fs doesn't need to be as lowas you might like
for the pipe, around 1/2 to 2/3 the cross sectional area of the driver diaphragm and build some sort of reducers in the 10 inches either side of the driver to get it to mount on the pipe.
Drew
Hi all, sorry for dredging this thread from the murky deeps.
I was wondering how well the Acoustic cannon approach would work with a cheap driver and some big PVC tubing and knees, like qi suggested in this picture:
http://www.diyaudio.com/forums/attachment.php?s=&postid=269517&stamp=1069598608
What if I made that from 12" (or 10") pvc pipe and bends, and stuffed it under my bed? What could I expect?
What are the properties to look for in a woofer for these kind of setups? I know you should tune the longest tube for hald the driver fs. So if I want useable 20-50hz (pref -3b bandwidth) production, would I need a 12" woofer resonating at 40hz? Would this need a very very low QTS?
I have some 12" tonsil woofers lying around with these specs:
Fs: 25hz
Vas:290l
QMS: 1.87
Qes:0.27
Qts:0.23
Pmax: 150Wrms
Would these be suitable for a cannon?
Thanks in advance,
Tim
I was wondering how well the Acoustic cannon approach would work with a cheap driver and some big PVC tubing and knees, like qi suggested in this picture:
http://www.diyaudio.com/forums/attachment.php?s=&postid=269517&stamp=1069598608
What if I made that from 12" (or 10") pvc pipe and bends, and stuffed it under my bed? What could I expect?
What are the properties to look for in a woofer for these kind of setups? I know you should tune the longest tube for hald the driver fs. So if I want useable 20-50hz (pref -3b bandwidth) production, would I need a 12" woofer resonating at 40hz? Would this need a very very low QTS?
I have some 12" tonsil woofers lying around with these specs:
Fs: 25hz
Vas:290l
QMS: 1.87
Qes:0.27
Qts:0.23
Pmax: 150Wrms
Would these be suitable for a cannon?
Thanks in advance,
Tim
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.