Go Back   Home > Forums > Loudspeakers > Subwoofers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 6th February 2007, 01:59 AM   #1
diyAudio Member
 
Join Date: Nov 2006
Default The craziest project

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/pshow...number=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.)
  Reply With Quote
Old 6th February 2007, 02:20 AM   #2
diyAudio Member
 
Join Date: Jan 2006
Location: Fairmount, GA
I can only attest to the sub speaker. It is quit a performer. You will be amazed.

And YES, you ARE crazy!

Have fun and send pics!
__________________
Poor stereo mix? Switch to mono! Perfect.
  Reply With Quote
Old 6th February 2007, 02:32 AM   #3
Variac is offline Variac  United States
diyAudio Editor
 
Variac's Avatar
 
Join Date: Dec 2001
Location: San Francisco, USA
going to Burning Man?
  Reply With Quote
Old 6th February 2007, 04:04 AM   #4
braden is offline braden  Canada
diyAudio Member
 
Join Date: Jan 2007
Location: Ontario
Quote:
Originally posted by Variac
going to Burning Man?
...exactly what i was thinking. or some type of "reclaim your public space" event.
  Reply With Quote
Old 6th February 2007, 04:28 AM   #5
Ang is offline Ang  United States
diyAudio Member
 
Join Date: Feb 2006
Location: Pittsburgh
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.
  Reply With Quote
Old 6th February 2007, 04:42 AM   #6
Apogee is offline Apogee  United States
diyAudio Member
 
Apogee's Avatar
 
Join Date: Feb 2002
Location: Tacoma, WA
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!

__________________
"If I had my life to live over again, I would have made a rule to read some poetry and listen to some music at least once a week." - Charles Darwin
  Reply With Quote
Old 6th February 2007, 04:46 AM   #7
Ang is offline Ang  United States
diyAudio Member
 
Join Date: Feb 2006
Location: Pittsburgh
I'm wondering how big of a "chamber" you can have in the triangle and still pedal comfortably
  Reply With Quote
Old 6th February 2007, 04:55 AM   #8
Apogee is offline Apogee  United States
diyAudio Member
 
Apogee's Avatar
 
Join Date: Feb 2002
Location: Tacoma, WA
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-Pass...QQcmdZViewItem

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...
__________________
"If I had my life to live over again, I would have made a rule to read some poetry and listen to some music at least once a week." - Charles Darwin
  Reply With Quote
Old 6th February 2007, 05:30 AM   #9
Apogee is offline Apogee  United States
diyAudio Member
 
Apogee's Avatar
 
Join Date: Feb 2002
Location: Tacoma, WA
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-53...QQcmdZViewItem

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-Radia...QQcmdZViewItem

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!
__________________
"If I had my life to live over again, I would have made a rule to read some poetry and listen to some music at least once a week." - Charles Darwin
  Reply With Quote
Old 6th February 2007, 06:12 AM   #10
poynton is offline poynton  United Kingdom
diyAudio Member
 
poynton's Avatar
 
Join Date: Mar 2005
Location: A life on the ocean waves when I'm not at home in N. Wales (but I'm not Welsh so no sheep jokes!)
How about redesigning and rebuilding the bike with wider diameter tubing so that the batteries and tweeter could be built in or a couple of TB 3" drivers???

Andy
__________________
If it ain't broke, break it !! Then fix it again. It's called DIY !
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
CDPRO2 Group Project (open source project) BrianGT Digital Source 147 8th August 2008 11:37 AM
My OLD Project....... cheap tube audio project!!! tube-lover Tubes / Valves 4 8th May 2008 09:26 PM
New OB project Geoff H Full Range 18 16th September 2007 11:14 AM
My first project, cool project. sorinsistem Solid State 3 19th January 2006 05:08 PM


New To Site? Need Help?

All times are GMT. The time now is 02:59 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2