Ghettoblaster - crossovers, drivers, enclosure?

[hospadar]

I want to design myself a nice little ghettoblaster for music, computer sound, etc when I'm out of the house or working somewhere away from my nice stereo. The basic idea being a decent sounding loudspeaker/amp/power supply combo all rolled into one box. Maximum audio purity is not particularly important, although I'd of course like it to sound as good as possible (price being an important consideration). I'll be using relatively cheap drivers and a home-made chipamp. I currently plan on a stuffed acoustic suspension enclosure for minimum total size.

My questions are:
1) I have 2 fullrange drivers (~3"), should I run them in stereo, parallel, or with a crossover? I've always been under the impression that part of the problem with fullrange drivers is that one cone has trouble reproducing many disparate frequencies at once.

Would I actually see a real advantage by splitting the frequencies between two identical fullrange drivers?

Stereo seems like the most straightforward option, but since the drivers will be very close to each other, perhaps a parallel configuration for more volume, or the crossed-over configuration makes more sense.

2)I know the manufacturer recommended enclosure sizes (unstuffed) for these drivers, what's the best way to figure out how small the enclosure can be after stuffing?

Thanks

[picowallspeaker]

Hi . HI !!!! What about a single channel ,or mono ,device ?
Since you are concerned about simple things ( two channels ,the left and the right , must be maintained divided till the end ,you cannot sum the two currents or do whatever ...indeed they can be summed at line level ,i.e. mixed into one channel ,then they can be powered by a chip amp ,like a TDA 1562 )
For the speakers ,the more (and big) ,the merrier .. <not true
Generally ,for mid-fidelity or mobile applications , a fullrange speaker is the best in terms of costs ,portability ...but going higher with power , to make behave a speaker like a linear piston ,it has to be specialized in its range of frequency ,so depending in membrane area ,or cone , which brings with itself also beaming by raising the frequency ... Also a fullrange speaker is an easy load for the amplifier ,being just a coil ; when using different specialized speakers ,woofers ,tweeters ,etc . and the necessary crossover network to split frequencies to the different drivers, the resulting load seen by the amplifier won't be as easy as a single coil ...

)I know the manufacturer recommended enclosure sizes (unstuffed) for these drivers, what's the best way to figure out how small the enclosure can be after stuffing?

Trial and error

[hospadar]

Thanks!

The more I think about it, the more I think a single channel device would be best (for simplicity and since there will be little physical separation of the drivers). But this still leaves the question of crossover or no.

I've seen some inexpensive (<$20) ~4" subs that claim to have a decent frequency response down to about 40hz, would that, coupled with an inexpensive fullrange for the mid and high frequencies (with a simple passive crossover) give me significantly better sound than just one or two decent fullrange drivers?

- And what about efficiency? I know the crossover network would eat some power, does anyone know roughly much efficiency (power in vs SPL out) I loose by adding a dead-simple crossover network?

[Buckapound]

I would just leave them as a stereo pair, with the amp running two channel, and leave them full range. You may need a "crossover" (filter, really) to tame some of the brightness of the small speakers. Search to see if someone's already worked this out for your model driver.

FYI, chip Amps aren't all that efficient. Most of us with boomboxes use Tripath/Class D amps, which last a lot longer on battery power. Check out the Boominator thread, as there's a lot of good information on general aspects of boomboxes, not just that specific build. There are a few other boombox threads on this site worth checking out, so do.

Also check out Zaphaudio.com, as he's got lots of nice small speaker designs that you can adapt into your blaster. On the trial and error thing, I'm a big fan of making trial boxes out of scrap wood, and then you can really tinker with the size and shape and build the real thing more carefully.

--Buckapound

[sreten]

Hi,

Take a look at : Parts Express DIY Project

rgds, sreten.

Small inefficient drivers are not the best choice for battery / low power.