Ok folks, here's a strange one for you. Sorry for the long post, I
have thought about this a lot and so I figured I should just write
down what I've thought about and solicit comments from you experts!
The story: I'm trying to build a sound system for my bicycle. Yes, I'm
crazy, and it's a long story. Basically it needs to be 1) loud enough
to dance to, 2) somewhat durable, 3) portable, and 4) cheap enough so
i won't care that much if it gets broken or stolen. (I'm not planning
on keeping it on my bike all the time, just for special occasions.)
Being audiophile etc is not as important as being able to produce good
volume especially at the low end. (This is going to be my soul-train
bicycle...)
The amplifier is a T-amp, built from the AMP6-BASIC kit from
www.41hz.com, which is totally awesome. The output power is around
2x25W RMS maximum, into 4 ohms at 10% THD+N. Up to about 2X15W, the
THD+N is below 0.1%. It's super efficient, I power this sucker with
8-10AA batteries and it lasts forever, and it's tiny, audiophile sound
quality, etc.
I've gone through many ideas as far as speaker design (TQWTs out of
ABS pipe, etc.) As an experiment I even got a pair of Fostex FE166E's
and built a 288 cu in cabinet out of double-ply cardboard fitting
perfectly inside the main triangle of the bicycle. These are
wonderfully efficient and loud but didn't have enough bottom end, even
in a bass-reflex (cardboard) cabinet. Also the exposed cones and cost
of the drivers made me a little afraid of using them.
So I've decided to go with a sub/sat system to get the bass I want.
For the satellites I'm going to use the Sonic Impact Soundpads
attached to cardboard triangles fitted into the main triangle of the
bicycle. (For those of you unfamiliar, these are $30 devices which
turn any relatively rigid surface into a speaker.) They actually
produce good volume in the mid / mid-high range, of course without
nearly the clarity of the FE166E's and even less bass. But they're
cheap, light and they can hide inside the cardboard triangle.
For the sub, I'm thinking about building a 4th order bandpass sub. The
candidate driver is the $21 Dayton SD215-88 8" shielded DVC subwoofer
http://www.partsexpress.com/pe/pshowdetl.cfm?&Partnumber=295-480
*Power Handling: 80 watts RMS/120 watts max *VCdia: 1.5" *Le: 1.2 mH
*Impedance: 8 ohms per coil *Re: 3.00 ohms *Frequency range: 30-2,000
Hz *Fs: 28 Hz *SPL: 89.0 dB 2.83V/1m *Vas: 1.40 cu. ft. *Qms: 3.40
*Qes: .47 *Qts: .41 *Xmax: 6 mm *Dimensions: Overall Diameter: 8-1/2",
Cutout Diameter: 7-1/8", Mounting Depth: 4-1/4".
The enclosure I'm thinking about is 8 in diameter (really 8.5 in
diameter) cardboard tubing I found at home depot (for pouring concrete
pillars, I think.) I tried some of those 4th order bandpass web
calculators and they gave me on the order of 5-12 inches of total
length for the tube (numbers below); this can easily be strapped to a
rear luggage / pannier rack. I think it should give me the bass I
want, and be relatively small, cheap, and without exposed parts.
Now for my questions:
1) Am I crazy? Is this a good design for what I want?
2) Should I be thinking subwoofer in bandpass + soundpads, or woofer
in bass reflex + soundpads? Or something else? Will I get killed on
the low-mids? Is that a problem?
3) Any ideas on how to design filters / a crossover for this setup?
I'm fairly happy soldering caps / inductors to things, but I have no
idea how to design a circuit.....
4) Any other comments, or than on my sanity?
Thanks in advance,
Ben
ps numbers from the bandpass calculator
http://www.carstereo.com/help/Articles.cfm?id=27
Vf = 0.235 to 0.461 cu ft, or 1.78909 to 3.5096679 inches of 8.5 in tube
Vr = 0.213 to 0.689 cu ft, or 1.6216 to 5.245469 inches of 8.5 in tube
so about 5-12 inches of tube combined, taking into account the volume
of the speaker itself. (conservatively guessing the speaker itself is
about .22 cu ft which adds about 1.675 inches of length.)
have thought about this a lot and so I figured I should just write
down what I've thought about and solicit comments from you experts!
The story: I'm trying to build a sound system for my bicycle. Yes, I'm
crazy, and it's a long story. Basically it needs to be 1) loud enough
to dance to, 2) somewhat durable, 3) portable, and 4) cheap enough so
i won't care that much if it gets broken or stolen. (I'm not planning
on keeping it on my bike all the time, just for special occasions.)
Being audiophile etc is not as important as being able to produce good
volume especially at the low end. (This is going to be my soul-train
bicycle...)
The amplifier is a T-amp, built from the AMP6-BASIC kit from
www.41hz.com, which is totally awesome. The output power is around
2x25W RMS maximum, into 4 ohms at 10% THD+N. Up to about 2X15W, the
THD+N is below 0.1%. It's super efficient, I power this sucker with
8-10AA batteries and it lasts forever, and it's tiny, audiophile sound
quality, etc.
I've gone through many ideas as far as speaker design (TQWTs out of
ABS pipe, etc.) As an experiment I even got a pair of Fostex FE166E's
and built a 288 cu in cabinet out of double-ply cardboard fitting
perfectly inside the main triangle of the bicycle. These are
wonderfully efficient and loud but didn't have enough bottom end, even
in a bass-reflex (cardboard) cabinet. Also the exposed cones and cost
of the drivers made me a little afraid of using them.
So I've decided to go with a sub/sat system to get the bass I want.
For the satellites I'm going to use the Sonic Impact Soundpads
attached to cardboard triangles fitted into the main triangle of the
bicycle. (For those of you unfamiliar, these are $30 devices which
turn any relatively rigid surface into a speaker.) They actually
produce good volume in the mid / mid-high range, of course without
nearly the clarity of the FE166E's and even less bass. But they're
cheap, light and they can hide inside the cardboard triangle.
For the sub, I'm thinking about building a 4th order bandpass sub. The
candidate driver is the $21 Dayton SD215-88 8" shielded DVC subwoofer
http://www.partsexpress.com/pe/pshowdetl.cfm?&Partnumber=295-480
*Power Handling: 80 watts RMS/120 watts max *VCdia: 1.5" *Le: 1.2 mH
*Impedance: 8 ohms per coil *Re: 3.00 ohms *Frequency range: 30-2,000
Hz *Fs: 28 Hz *SPL: 89.0 dB 2.83V/1m *Vas: 1.40 cu. ft. *Qms: 3.40
*Qes: .47 *Qts: .41 *Xmax: 6 mm *Dimensions: Overall Diameter: 8-1/2",
Cutout Diameter: 7-1/8", Mounting Depth: 4-1/4".
The enclosure I'm thinking about is 8 in diameter (really 8.5 in
diameter) cardboard tubing I found at home depot (for pouring concrete
pillars, I think.) I tried some of those 4th order bandpass web
calculators and they gave me on the order of 5-12 inches of total
length for the tube (numbers below); this can easily be strapped to a
rear luggage / pannier rack. I think it should give me the bass I
want, and be relatively small, cheap, and without exposed parts.
Now for my questions:
1) Am I crazy? Is this a good design for what I want?
2) Should I be thinking subwoofer in bandpass + soundpads, or woofer
in bass reflex + soundpads? Or something else? Will I get killed on
the low-mids? Is that a problem?
3) Any ideas on how to design filters / a crossover for this setup?
I'm fairly happy soldering caps / inductors to things, but I have no
idea how to design a circuit.....
4) Any other comments, or than on my sanity?
Thanks in advance,
Ben
ps numbers from the bandpass calculator
http://www.carstereo.com/help/Articles.cfm?id=27
Vf = 0.235 to 0.461 cu ft, or 1.78909 to 3.5096679 inches of 8.5 in tube
Vr = 0.213 to 0.689 cu ft, or 1.6216 to 5.245469 inches of 8.5 in tube
so about 5-12 inches of tube combined, taking into account the volume
of the speaker itself. (conservatively guessing the speaker itself is
about .22 cu ft which adds about 1.675 inches of length.)
I think you should create a system that runs of pedal power.
In interests of space and still being able to ride the thing, how about a couple of planars in a dipole arangement on a baffle that fills the main triangle? I suppose you could put the tweeters there too, but you may want to look into some sort of suspension (gel enclosure?) for them to deal with some of the vibration they'll be subjected to.
While I'm at it, it would be kind of cool to mount the tweeter on your helmet, like a light - flush mount it and you'll be minimizing diffraction effects. (just use long wires for this) Then when you stop to talk to people you can kind of beam the treble at them.
For the sub, unless you put a small enclosure in a backpack and wear that too, perhaps you could just stick a sub inclosure in a basket on the front or rear, (in elegant, I know, but simple).
You could make the pipe longer if you mount it along the top tube - use a pvc bend and double it up so the port is also front firing. It would just be a matter of stabilizing 16" of stacked tube, but it shouldn't be too hard.
In interests of space and still being able to ride the thing, how about a couple of planars in a dipole arangement on a baffle that fills the main triangle? I suppose you could put the tweeters there too, but you may want to look into some sort of suspension (gel enclosure?) for them to deal with some of the vibration they'll be subjected to.
While I'm at it, it would be kind of cool to mount the tweeter on your helmet, like a light - flush mount it and you'll be minimizing diffraction effects. (just use long wires for this) Then when you stop to talk to people you can kind of beam the treble at them.
For the sub, unless you put a small enclosure in a backpack and wear that too, perhaps you could just stick a sub inclosure in a basket on the front or rear, (in elegant, I know, but simple).
You could make the pipe longer if you mount it along the top tube - use a pvc bend and double it up so the port is also front firing. It would just be a matter of stabilizing 16" of stacked tube, but it shouldn't be too hard.
Burning man was my first thought... 
I'd biamp the whole setup...
Go with a piece of 12" sonotube (the home depot concrete stuff) cut about 24" long. Cap both ends with plywood. In one end, install a 10" driver (can be cheap). This end will face to the rear of the bike (think rocket engine).
Inside the tube, I'd house a lawnmower starting battery for power with another switching amp. This wouldn't be too heavy for a bike rack.
From the other end of the cap, I'd run two 2" or 3" rubber flex tubes (or abs plastic pipe) under the seat, along the top bar and drop them into a resonance chamber at the front up near the steering head. The chamber would encompass the entire triangle area beneath the top bar. Paint them silver so they look high-tech. In the resonance chamber, you could mount a couple of small passive radiators if you wanted...
I'm thinking that it'd actually get fairly loud, would run for a while, and you'd actually have some bass response...
You could install a circuit in the resonance chamber with a bunch of led's for a moving light show that was sync'd to the music...
I'm like'n this... LOL!
I'd biamp the whole setup...
Go with a piece of 12" sonotube (the home depot concrete stuff) cut about 24" long. Cap both ends with plywood. In one end, install a 10" driver (can be cheap). This end will face to the rear of the bike (think rocket engine).
Inside the tube, I'd house a lawnmower starting battery for power with another switching amp. This wouldn't be too heavy for a bike rack.
From the other end of the cap, I'd run two 2" or 3" rubber flex tubes (or abs plastic pipe) under the seat, along the top bar and drop them into a resonance chamber at the front up near the steering head. The chamber would encompass the entire triangle area beneath the top bar. Paint them silver so they look high-tech. In the resonance chamber, you could mount a couple of small passive radiators if you wanted...
I'm thinking that it'd actually get fairly loud, would run for a while, and you'd actually have some bass response...
You could install a circuit in the resonance chamber with a bunch of led's for a moving light show that was sync'd to the music...
I'm like'n this... LOL!
I would guess it could be 3 or 4 inches wide without much problem.
He could use 1/4" hardboard with 1x2 edges and bracing. This way he'd maximize the internal volume.
I'd buy flat passive radiators and mount them to the outside.
Something like a pair of 6" or 8" would be perfect. A quick search on ebay led to these:
http://cgi.ebay.com/1-Pair-Sony-Pas...em-Speakers_W0QQitemZ9702372179QQcmdZViewItem
It'd also be great if he could find a long excursion 10" for the main woofer but that might blow the budget.
I'd also go with an amp that has more power the bottom end. You can find small used car audio switching amps everywhere - try craigslist. Just don't buy a high wattage one or you'll pull the battery down too fast.
I would just do a simple crossover between the source and the amps.
Lastly, I'd mount the passives as far from the chamber "inlets" as you can...
He could use 1/4" hardboard with 1x2 edges and bracing. This way he'd maximize the internal volume.
I'd buy flat passive radiators and mount them to the outside.
Something like a pair of 6" or 8" would be perfect. A quick search on ebay led to these:
http://cgi.ebay.com/1-Pair-Sony-Pas...em-Speakers_W0QQitemZ9702372179QQcmdZViewItem
It'd also be great if he could find a long excursion 10" for the main woofer but that might blow the budget.
I'd also go with an amp that has more power the bottom end. You can find small used car audio switching amps everywhere - try craigslist. Just don't buy a high wattage one or you'll pull the battery down too fast.
I would just do a simple crossover between the source and the amps.
Lastly, I'd mount the passives as far from the chamber "inlets" as you can...
Running with this a bit further...
Just make sure that whatever you buy isn't too deep.
A quick search of ebay also turned up these:
http://cgi.ebay.com/2-Infinity-RS-5...ryZ47095QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
Or as an alternate, you could just cut the holes and glue these on the outside. I'd try to find smaller ones if possible though.
http://cgi.ebay.com/10-Passive-Radi...ryZ14993QQrdZ1QQssPageNameZWD1VQQcmdZViewItem
Also, wouldn't be a bad idea to roll-off the bottom end so you are not drawing lots of juice pushing air that nobody will feel. I would think it would be better to have it sound good and run for longer rather than attempting to push very low bass. Low bass takes lots of power, especially outside, and that would shorten your runtime considerably
Have fun!
Just make sure that whatever you buy isn't too deep.
A quick search of ebay also turned up these:
http://cgi.ebay.com/2-Infinity-RS-5...ryZ47095QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
Or as an alternate, you could just cut the holes and glue these on the outside. I'd try to find smaller ones if possible though.
http://cgi.ebay.com/10-Passive-Radi...ryZ14993QQrdZ1QQssPageNameZWD1VQQcmdZViewItem
Also, wouldn't be a bad idea to roll-off the bottom end so you are not drawing lots of juice pushing air that nobody will feel. I would think it would be better to have it sound good and run for longer rather than attempting to push very low bass. Low bass takes lots of power, especially outside, and that would shorten your runtime considerably
Have fun!
Thanks for all the replies!
0) Actually this is not for Burning Man, though I might lend it to someone who is going. This is for membership to a bicycle dance gang. (Don't ask...)
1) While I like the idea of adding another amp to the system, I think for simplicity I'd like to try to keep it a one amp setup -- maybe later I'll try another amp. Plus there's something aesthetically attractive about powering this whole thing with 8 AA batteries. I think I'll take your advice and skip on the really low frequencies, if it takes too much power. Dance music is the important thing here.
2) AFAICT, passive radiators are an alternative to porting? The advantage for me being size of box reasons?
3) I can't find inexpensive planar speakers with decent bass. Am I not looking in the right places?
4) I got one "yes" for the Dayton SD215-88 8". They seem to have incredible Xmax (6mm) for the price ($21), and it's a dual voice coil which is great for me (size reasons.) Any other opinions? Or other driver recommendations?
5) A 4th order bandpass will have a pass band top end of around 80-120Hz. Is that going to fill up enough of the low mids or should I go for a standard bass reflex with a port or passive radiator (possibly loosing some low end volume?)
6) You can fit about 3.5-4 inches between your pedal crank arms. I made a box that was about 288 cu in (that takes into account the speaker volume of the fe166e's.) Right now I'm really liking the idea of using the soundpads and cardboard in the triangle (since I already own the soundpads!) and using sonotube for a sub / woofer on the rear rack.
7) I've NEVER designed a crossover. Given the simplicity / cost issues, I'm thinking of what I find on the internet as called "1st order crossover." Given that the 4th order enclosure will roll off around 80-120 Hz already, should I pick that same level as my crossover point? I can't seem to find caps / inductors big enough...what about using the partsexpress "bass stoppers" and letting the sub play full range?
Thanks again! I'll send pics when I make the thing.....
Ben
0) Actually this is not for Burning Man, though I might lend it to someone who is going. This is for membership to a bicycle dance gang. (Don't ask...)
1) While I like the idea of adding another amp to the system, I think for simplicity I'd like to try to keep it a one amp setup -- maybe later I'll try another amp. Plus there's something aesthetically attractive about powering this whole thing with 8 AA batteries. I think I'll take your advice and skip on the really low frequencies, if it takes too much power. Dance music is the important thing here.
2) AFAICT, passive radiators are an alternative to porting? The advantage for me being size of box reasons?
3) I can't find inexpensive planar speakers with decent bass. Am I not looking in the right places?
4) I got one "yes" for the Dayton SD215-88 8". They seem to have incredible Xmax (6mm) for the price ($21), and it's a dual voice coil which is great for me (size reasons.) Any other opinions? Or other driver recommendations?
5) A 4th order bandpass will have a pass band top end of around 80-120Hz. Is that going to fill up enough of the low mids or should I go for a standard bass reflex with a port or passive radiator (possibly loosing some low end volume?)
6) You can fit about 3.5-4 inches between your pedal crank arms. I made a box that was about 288 cu in (that takes into account the speaker volume of the fe166e's.) Right now I'm really liking the idea of using the soundpads and cardboard in the triangle (since I already own the soundpads!) and using sonotube for a sub / woofer on the rear rack.
7) I've NEVER designed a crossover. Given the simplicity / cost issues, I'm thinking of what I find on the internet as called "1st order crossover." Given that the 4th order enclosure will roll off around 80-120 Hz already, should I pick that same level as my crossover point? I can't seem to find caps / inductors big enough...what about using the partsexpress "bass stoppers" and letting the sub play full range?
Thanks again! I'll send pics when I make the thing.....
Ben
Freak them out with an ice cream bike. paint the ice cream box black and put a huge efficient woofer in there
plenty of space for solar panels or batteries or whatever.
OR you could build an inverted U shaped box that would go on a rear carrier where panniers would be . it could be quite large indeed.
plenty of space for solar panels or batteries or whatever.
OR you could build an inverted U shaped box that would go on a rear carrier where panniers would be . it could be quite large indeed.
Hi
Some really good and creative idea's on this thread. Using D amps you are way ahead of the game already. Not sure of the sound pads eff. but what ever they end up being, your bass driver should have at least 4-6 dB more sensitivity (open space eats bass)! If not they will sound weak whatever the frequency response, but you could always pad down the sound pads which IMO would be counter productive to the goal.
The 8 in DVC driver looks pretty good and should give good bass in a larger ported enclosure. The sensitivity is not all that good tho at 89 db into 4 ohms is comparable to 86dB at 8 ohms pretty poor IMO. What I would do is look for a smaller PA driver (2x8"?) and build a practice amp type of box (partially open back box) use 3/8 ply frnt baffle with 1/4 ply sides with a few extra braces/cleats.
Driver should >93 db sens wth fs around 50-60Hz Qts around 0.7 or so should be good. Maybe a pioneer or eminence with wizzer cone for almost full range.
Some really good and creative idea's on this thread. Using D amps you are way ahead of the game already. Not sure of the sound pads eff. but what ever they end up being, your bass driver should have at least 4-6 dB more sensitivity (open space eats bass)! If not they will sound weak whatever the frequency response, but you could always pad down the sound pads which IMO would be counter productive to the goal.
The 8 in DVC driver looks pretty good and should give good bass in a larger ported enclosure. The sensitivity is not all that good tho at 89 db into 4 ohms is comparable to 86dB at 8 ohms pretty poor IMO. What I would do is look for a smaller PA driver (2x8"?) and build a practice amp type of box (partially open back box) use 3/8 ply frnt baffle with 1/4 ply sides with a few extra braces/cleats.
Driver should >93 db sens wth fs around 50-60Hz Qts around 0.7 or so should be good. Maybe a pioneer or eminence with wizzer cone for almost full range.
Her are some observations. If the prices don't scare you off, you could probably get sone serious noise and decent sound quality from the little amp..
You are making some sense so far. The bass should be in a sonotube and should be mounted on the back rack as you propose.
Places like Whitecap - a contractors supply store will cut pieces of cardboard sonotube I believe. I'm thinking 16" diameter by about 3' long!!!
The main point I think to make this work reasonably is you HAVE to use efficient speakers. If you find some that are say 96 dB efficient at one watt at one meter, they might be eight times as efficient as a standard speaker, ie 1/8 the power required..compared to the 8" you mentioned.. With that little amp it is crucial.
About the only bass speakers that will do this are pro (PA) drivers. Pro drivers in a reasonable size don't really go that low but that's OK 'case most music doesn'trealy go so low. A 10" or 12" pro driver could easily weigh 20 pounds, BUT get drivers with neodymium magnets and that same driver would weigh about 6-8 pounds.
BUt it will cost a couple of hundred dollars. Maybe $150 on sale...
Maybe 98 db efficient!
If that price is too high you could go with regular magnets and get a cheapo at about $40-60 Since it's a cheapo, the magnet will be small and not that heavy..
Then for your mids/ highs- how about a cheaper Fostex fullrange. at about $60? Also very efficient, and you could make an open baffle by just having a 1/2" piece of foamcore or wood inside the triangle, and mounting the driver reasonably on center - a little off is better...
You don't need a box, just a panel.. then sound goes out both sides ,,and the panel is big enough fo you to cover most of the midrange
I'd stick with just one of these drivers too, and run the whole thing mono by combining the channels. You could use one channel for the bass driver and the other for the mid/high driver...Then you use an active crossover to make it abiout twice MORE efficient. The active vcrossover splits the frequencies Before the amp, so is small light and no power is wasted being cut off....
Another brand to look at is Tangband (the TB someone mentioned.- they have small drivers for the mids, that have neodymium drivers also so they are light, and the magnets are small , which will allow sound to easily come out od bothe sides of the bike.. BUT aren't crazy efficient I don't think
If any of these ideas appeal we can fill inthe details....
You are making some sense so far. The bass should be in a sonotube and should be mounted on the back rack as you propose.
Places like Whitecap - a contractors supply store will cut pieces of cardboard sonotube I believe. I'm thinking 16" diameter by about 3' long!!!
The main point I think to make this work reasonably is you HAVE to use efficient speakers. If you find some that are say 96 dB efficient at one watt at one meter, they might be eight times as efficient as a standard speaker, ie 1/8 the power required..compared to the 8" you mentioned.. With that little amp it is crucial.
About the only bass speakers that will do this are pro (PA) drivers. Pro drivers in a reasonable size don't really go that low but that's OK 'case most music doesn'trealy go so low. A 10" or 12" pro driver could easily weigh 20 pounds, BUT get drivers with neodymium magnets and that same driver would weigh about 6-8 pounds.
BUt it will cost a couple of hundred dollars. Maybe $150 on sale...
Maybe 98 db efficient!
If that price is too high you could go with regular magnets and get a cheapo at about $40-60 Since it's a cheapo, the magnet will be small and not that heavy..
Then for your mids/ highs- how about a cheaper Fostex fullrange. at about $60? Also very efficient, and you could make an open baffle by just having a 1/2" piece of foamcore or wood inside the triangle, and mounting the driver reasonably on center - a little off is better...
You don't need a box, just a panel.. then sound goes out both sides ,,and the panel is big enough fo you to cover most of the midrange
I'd stick with just one of these drivers too, and run the whole thing mono by combining the channels. You could use one channel for the bass driver and the other for the mid/high driver...Then you use an active crossover to make it abiout twice MORE efficient. The active vcrossover splits the frequencies Before the amp, so is small light and no power is wasted being cut off....
Another brand to look at is Tangband (the TB someone mentioned.- they have small drivers for the mids, that have neodymium drivers also so they are light, and the magnets are small , which will allow sound to easily come out od bothe sides of the bike.. BUT aren't crazy efficient I don't think
If any of these ideas appeal we can fill inthe details....
This reminds me when I was at uni and had a bike with a 55w headlight! I had a lead acid battery the weighed ~4kg and could power the light for about 50 minutes.
It's an interesting challenge. Getting bass outdoors is the hard part. The room adds a lot to the bass
For the bass - definately bandpass - 6th order. You want a dual VC driver so you can use each channel of one amp to power each VC. You can't really get much real bass, so instead you probably want to put a bit of a peak in at around 60 Hz. For the box, think cardboard cylinder, with hemisphere ends and for the driver baffle (internal) plywood. You could make the hemisphere ends out of paper mache with a layer of fibreglass for rigidity. The above will give you the maximum output and the lightest box. You might look at a driver with a neo magnet. Consider total driver weight.
For the satelite, I'd go with a driver rather than a soundpad. If you want no box, then you can use a driver without a box - open baffle. Give it a cardboard baffle and reinforce it with ribs and cardboard if you like. Fold wings, perhaps balsa wood reinforced with fibreglass.
I'd put the sub on the rack behind and put the sat above it, the closer it is to you, the better. Moving it from 1m to 0.5m means 1/4 the power.
For the sat, why not keep it simple? Look for an efficient fullranger, it will make xo easy. Add a tweeter where it rolls off, if the fullranger can get to 10k then just do a simple highpass first order on the tweeter at that point.
Use one channel of the 2nd amp for the tweeter, one for the fullranger. To save power, how about passive line level filters?
Look for a fullranger with a fairly high fs. What you want is efficiency above 120 Hz, say an 8" driver. Then you put it in a vented box where the vent is needed to get it down to the xo point, say 120 Hz. Ideally you want a driver that will actually need to be vented as it will be more efficient above that point. For the box I'd use materials like a cardboard cylinder, balsa wood, paper mache, ply and fibreglass reinforcement.
An alternative is ditch the tweeter and use two fullrangers that can get up high. They would probably be smaller, and having two brings the efficiency back up.
Now that I look at some sims, I see that with that 8" driver a bandpass doesn't easily gain an advantage over vented. You could just use it in a 12L vented box tuned to 50 Hz. You can get 100 db @ 40 Hz! Not bad, that's with 25 watts from one channel. Use the other channel for a fullranger like a tangband, or a few to get the right efficiency. Ideally you would use a passive line level to save power.
It's an interesting challenge. Getting bass outdoors is the hard part. The room adds a lot to the bass
For the bass - definately bandpass - 6th order. You want a dual VC driver so you can use each channel of one amp to power each VC. You can't really get much real bass, so instead you probably want to put a bit of a peak in at around 60 Hz. For the box, think cardboard cylinder, with hemisphere ends and for the driver baffle (internal) plywood. You could make the hemisphere ends out of paper mache with a layer of fibreglass for rigidity. The above will give you the maximum output and the lightest box. You might look at a driver with a neo magnet. Consider total driver weight.
For the satelite, I'd go with a driver rather than a soundpad. If you want no box, then you can use a driver without a box - open baffle. Give it a cardboard baffle and reinforce it with ribs and cardboard if you like. Fold wings, perhaps balsa wood reinforced with fibreglass.
I'd put the sub on the rack behind and put the sat above it, the closer it is to you, the better. Moving it from 1m to 0.5m means 1/4 the power.
For the sat, why not keep it simple? Look for an efficient fullranger, it will make xo easy. Add a tweeter where it rolls off, if the fullranger can get to 10k then just do a simple highpass first order on the tweeter at that point.
Use one channel of the 2nd amp for the tweeter, one for the fullranger. To save power, how about passive line level filters?
Look for a fullranger with a fairly high fs. What you want is efficiency above 120 Hz, say an 8" driver. Then you put it in a vented box where the vent is needed to get it down to the xo point, say 120 Hz. Ideally you want a driver that will actually need to be vented as it will be more efficient above that point. For the box I'd use materials like a cardboard cylinder, balsa wood, paper mache, ply and fibreglass reinforcement.
An alternative is ditch the tweeter and use two fullrangers that can get up high. They would probably be smaller, and having two brings the efficiency back up.
Now that I look at some sims, I see that with that 8" driver a bandpass doesn't easily gain an advantage over vented. You could just use it in a 12L vented box tuned to 50 Hz. You can get 100 db @ 40 Hz! Not bad, that's with 25 watts from one channel. Use the other channel for a fullranger like a tangband, or a few to get the right efficiency. Ideally you would use a passive line level to save power.
Forget the box, the weight isn't necessary. Mount one of these http://www.musicsupplycenter.com/ProductDetails.asp?ProductCode=100-186 on the end of a 20" sonotube open at the other end. Stuff the pipe with polyfill. Sure it will be directional, but so are your mids and tweet. If no more of the $15 units are availabe, you'll have to pay $35 for regular ones. Cheap, efficient, easy, lightweight and plenty of great sounding OB bass with an Fequal less than 60hz and an F3 of about 45hz.
That's what we needed - some practical advice. And the efficiency is probably more than the full range you should be getting for the mid/highs, which will prob work out about right!
If you mount the tube across the bike then it will be pointing the direction that the mid/high driver is also pointing. On the other hand the rocket look with the cone facing backwards would be totally tempting.
HOw about the rocket look, but the baffle in the frame is mounted so you could swing it out perpindicular to the bike ,ie the mid/hi driver faces same direction as the woofer faces, when you are stopped.
Looks like you'll need a small frame with a tall seatpost so you can step over the frame to get on!
If you mount the tube across the bike then it will be pointing the direction that the mid/high driver is also pointing. On the other hand the rocket look with the cone facing backwards would be totally tempting.
HOw about the rocket look, but the baffle in the frame is mounted so you could swing it out perpindicular to the bike ,ie the mid/hi driver faces same direction as the woofer faces, when you are stopped.
Looks like you'll need a small frame with a tall seatpost so you can step over the frame to get on!
Too bad this didn't come up last week. I would have recommended 2 of those woofers. They run up high enough to cross to a tweet, but in the U config it may get too resonant up in that range. Really stuffing it may handle the pipe resonances, but you'll end up with at least one strong null in the 300-400hz range with a straight ended pipe. Cut the pipe end at an angle making one side about 2-3" longer. ie Driver end square so the driver fits squarely in the end, and the driver baffle to other end ranging from 20" to 23" due to the angled cut at the other end.
Then at the shortest part, cut a K-slot shaped curved triangle that starts at about 5" wide and is 5" deep, so instead of 20" that short side tapers down to a point at 15-16" from the baffle. This shape with some stuffing will really smooth out the resonances enough that all you need to add is a tweeter, not audiphile sound but pretty darn good. A 1st order XO may cover you.
If you use one of those bullet tweeters like this http://www.partsexpress.com/pe/pshowdetl.cfm?Partnumber=272-115
and stuff 6 pencil eraser sized pieces of foam rubber down in the throat around the bullet plug to tame the harshness. Add an L-pad to balance the output of the tweeter, and since it already comes with a cap, the only thing else you might need is a choke on the woofer.
Last week, when there were plenty of woofs for $15 you could have done stereo, hanging 2 tubes off the sides of the bike rack like a pair of rocket engines. One or 2 doesn't matter, and you'll end up with a cheap, lightweight, high output system that will blow the socks off of something using the little panel speaker.
Then at the shortest part, cut a K-slot shaped curved triangle that starts at about 5" wide and is 5" deep, so instead of 20" that short side tapers down to a point at 15-16" from the baffle. This shape with some stuffing will really smooth out the resonances enough that all you need to add is a tweeter, not audiphile sound but pretty darn good. A 1st order XO may cover you.
If you use one of those bullet tweeters like this http://www.partsexpress.com/pe/pshowdetl.cfm?Partnumber=272-115
and stuff 6 pencil eraser sized pieces of foam rubber down in the throat around the bullet plug to tame the harshness. Add an L-pad to balance the output of the tweeter, and since it already comes with a cap, the only thing else you might need is a choke on the woofer.
Last week, when there were plenty of woofs for $15 you could have done stereo, hanging 2 tubes off the sides of the bike rack like a pair of rocket engines. One or 2 doesn't matter, and you'll end up with a cheap, lightweight, high output system that will blow the socks off of something using the little panel speaker.
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