The boombox project

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Ok so this should be an ongoing project that may take all summer but I don't really know.

I want to build a boombox to kill all the 1200Watt Super BASS ULTIMATE! boomboxes out there. I am thinking of using the elf's as speakers or some 2-way joby, and I think the gainclone amp would do well. The main diffucultly will be the tuner and the cd player. Currently I think that it would be hard to run this whole system off batteries and still be able to cary it around, Unless I use cordless drill batteries maybe. So for now it can be AC powered. Mostly it will be integration and chassis design so I would love to hear suggestions from people to start me off, specifically in the CD tuner category. Thanks for the help.

Milo

PS I dont plan to make the cdplayer or the tuner but rather mod them from other things, like a computer cdplayer or something.
 
You could look at the old NEC SCSI CD-ROM drives. Most of the external SCSI ones have a display and control buttons, but require a caddy to load the disc. I saw a site where someone had modded a caddy based drive to be a "top loader". Most people who use these in audio are using them as a transport with an outboard DAC. There are audio and TTL digital outs on the back of the drive.

I think the model numbers are the CDR-601/602 for the external 4x/6x speed drives. There's also a top loader, the Multispin 3XP (CDR-400) that may be of use.

Figure on providing the drive with +12V @ 1amp and +5 @ 1amp .. Though I haven't measured what mine draw, that's what the switching power supply on the enclosed external version provides.

They're pretty cheap on Ebay ($10ish + shipping), or if you have a computer recycling/used computer store in your area, you might be able to find one there.
 
I'd of thought the obvious choice would be a car head unit.

Should run off a 14V source (13.8) perhaps a touch more.

If its a 4 channel unit with bridged outputs should manage
~ 25W per channel into 4 ohms and theorectically 50W per
channel into 2 ohms if the the unit can handle the current.

Speaker design is presumably is about compact efficiency.

I'd suggest a combination of a small sixth or 4th order
bandpass and a sealed high efficiency unit for mid treble,
with possibly a extra tweeter driver for treble fill, like the
one found here :

http://www.speakercity.com/clearance/clearance_drivers.shtml


:) sreten.
 
If you deliberately tune a box too high you will end up with less LF extension but increased SPL for a narrow frequency range. That's one of the tricks some of the boomboxes use. I have two prototype boxes with Dynaudio 17W75LQ drivers. The tubes used for the ports can easily be removed. If this is done then there is a remarkable increase in bass-SPL at the cost of precision. Just play around with a box-simulation tool a little and you will see what I mean.

You should of course only do this if you want to have "boom". You should also use a highpass filter in this case.

If you want to go for quality you better leave it of course.

Regards

Charles
 
This is a good project!

My Sony head does not require much current at all....there is a 10A fuse in the panel for it and it has NEVER blown, no matter how hard I push it (but it sounds crappy anyway at high volume when it starts to clip), I have 6-ohm speakers in the doors, so power RMS could not be more than 20W or so per channel. You will definatly need to use lower-impedance speakers to get any power out of them because of their small rail voltages.



-Matt
 
A3rd.Zero said:
I was thinking about a car head unit. Do you know what is typical current draw from a car head unit?

Phase_accurate: What?, Please explain.

Thank you

Milo

Hi Milo,

I'd expect static current to be quite low < 1 amp.

With typical efficiencies of class aB output stages and output
25W per channel clipping (x4) you can expect around 5 amps
average current drain, peak current ~ 10 amps.

:) sreten.
 
I would assume that using lower impeadence speakers would cause more current draw than the 6 ohm speakers you're currently using.

My personal opinion is that if you're looking to make a "hi-fi" boombox, I would probably stay away from the integrated amps in a car stereo headunit. However, it would probably be a great idea for the cd/radio portion of the boom box. Heck, you could even look for one of the double-din units that has a tape deck so you could really get that boombox effect :D

Maybe a decent headunit off of ebay + gainclones would equal something pretty dang tasty. Another option on the speakers is you could always have a foam bung or something to stuff the port to give you the "boom", with the option of removing it when you actually want it to sound decent
 
I like the idea of using the preouts and then using a gainclone or some such. It would be nice to use a head unit, which has the option of upgrading. I could even use one from the car and just plug it in when Im ready to go!

Ok now about the speakers, Im thinking something simple like the GR AV-1. I also like the idea of using a bg neo8 just for fun, but I dont know if I need a tweeter (not sure about its top end). Then the speaker boxes will in essence just be a woofer box, that might help get the low end.

Thanks for your help guys.

With ~2amps draw I guess i'm not going to try this with batteries, just AC on this one.

Milo
 
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