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A3rd.Zero 11th May 2004 02:47 AM

The boombox project
 
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.

A3rd.Zero 11th May 2004 07:41 PM

Come on, I know that at least Peter built one.

More specific questions

1. Does anyone know of a cdp that can be moded for top loading?
or
2. does anyone know of a cdp that is slot loading and has a display?

Thanks.

Milo

motherone 11th May 2004 08:42 PM

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.

A3rd.Zero 12th May 2004 12:23 AM

Ahhh, quite interesting. I wasn't aware that the NEC had a display, that may work well if modified to accept a toploader.

Thanks

Milo

sreten 12th May 2004 08:25 AM

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..._drivers.shtml


:) sreten.

phase_accurate 12th May 2004 08:31 AM

If you want the "boom" of the boomboxes as well, you might possibly go for an intentional misalignment that allows a loud but not-so-deep bass reproduction.

Regards

Charles

A3rd.Zero 12th May 2004 01:29 PM

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

phase_accurate 12th May 2004 01:47 PM

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

zagisrule! 12th May 2004 01:48 PM

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 12th May 2004 02:32 PM

ahh, ok sounds good. Thanks for the explanation. Going for quality though.

Thanks
Milo


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