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-   -   the boombox on steroids thread (http://www.diyaudio.com/forums/class-d/143818-boombox-steroids-thread.html)

ke4mcl 10th May 2009 02:39 AM

the boombox on steroids thread
 
2 Attachment(s)
i have an 80s era sanyo boombox thats not on its best electronics wise. its got busted sliders and doesnt sound very good anymore.

im pondering putting a sure electronics 100wpc digital amp in it, usb soundcard so folks can plug into it and blue tooth connectivity. theres enough space for a pair of SLA batteries where the current cassette mechanism lives.

there seems to be a revival going on with boomboxes. hopping up a classic 80s design might make for a wayy cool device to take to the beach. small 80s boombox with "OMG thats loud" sound is what im thinking.

i ordered the 2 chnl 100wpc model and its back ordered till next week. 100wpc will give me plenty of highend speaker choices. anybody else gone portable with the sure electronics 100wpc boards?

i have the 4 channel one and have used it with house speakers and car batteries. its been out in the open with plenty of airflow. i'm wondering how they handle closed environments where they may get hot.

ke4mcl 11th May 2009 05:47 AM

no love for boombox hacking i guess. well i fly solo on this and will post results later.

Buckapound 11th May 2009 12:26 PM

Well, some of us love the boombox hacking.

Your challenges will be battery life at that kind of wattage, and making the flimsy cabinet stiff enough so it doesn't just shake itself apart at high volume levels (and lose a lot of bass in the process). You may need to go in with epoxy wood filler plus some strategic stiffening boards or other means. FWIW, modelmaker's styrene/ABS glues up real nice with superglue and can help improve the plastic cabinet. You can find it any good hobby shop.

Keep us informed.

--Buckapound

vaughn 11th May 2009 02:07 PM

It is an interesting idea but might fall under the category of "polishing a turd".

I think you would be better off building your own from the ground up with a more rigid case and
better quality speakers. You might look at old Dewalt or Makita tool cases (the plastic ones) as a good example of a beach worthy box that can stand up well. These are found frequently at thrift stores without the tools in them for cheap. Throw in a couple of decent full rangers and you are on the way.

Buckapound 11th May 2009 02:32 PM

Yeah, but people restore old Triumphs, too. Sometimes the presentation is important.

But you're right vaughn, it's always more work than starting from scratch.

--Buckapound

vaughn 11th May 2009 05:20 PM

Yeah, it occurred to me after I posted that the look was a large part of the appeal. Some of those old boom boxes are bringing ridiculous sums on various auction sites.

ke4mcl 11th May 2009 05:31 PM

its definitely polishing a turd... i'm doing it just to pull it off. the only expectations i have is that its really loud and doesnt eat batteries as fast as a regular boombox.

no fully operational boomboxes will be harmed in this experiment

Buckapound 11th May 2009 05:50 PM

As far as the batteries go, you would definitely be better off with a 2020-based amp (15 wpc?) vs. the one you're talking about. As far as wattage goes, remember 100watts is only twice as loud as 10 watts. With efficient drivers, those small amps can make a pile of sound. Somebody, correct me here if I've got this wrong, but isn't a 3 dB increase in driver efficiency equivalent in doubling amp power as far as sound level goes?

I get about 8-10 hrs from a fist-sized 7AH 12v SLA with a pair of 8-ohm drivers at reasonable volume.

--Buckapound

ke4mcl 12th May 2009 04:20 PM

i picked the 100wpc amp because i noticed that at least with the sure electronics class d boards. they sound amazing at low volume but sound quality begins to decrease as volume goes up. the speakers wouldnt handle the 100 watts anyways. the amp would be running way below its claimed 100wpc.

i do have the 15wpc and 8 wpc sure boards on hand. i read the tripath FAQ and saw the mods that can be done to the 15wpc boards. i'll be doing those soon.

i also have a set of the 2wpc tiny boards on their way destined to go into an altoids tin to be used as a headphone amp with some AA batts.

this is more of a "lets see if i can pull it off" experiment than an attempt to end up with something showroom quality.

Buckapound 12th May 2009 05:01 PM

The Tripath chips sound goot at about 2/3 of their rated power, which is to say, at reasonably close to their full volume level.

Using the 12v units simplifies the battery thing. If you've got them on hand, then at least you can try them before deciding where/how to mount them. Also, if you end up with the 100w board, but you're using at a lower power, shouldn't be too much worry about overheating--at least if you keep it out of the direct sun on hot days.

The next trick will be to find the driver that fiits with the highest efficiency at the price point you're working with, and then sort out what you can do with the acoustics given the box size you have. One thing on that cabinet. You may get the best rigidity by building an inner shell (even if it's fairly thin) and then fill the space between inner and outer with urethane or other foam--think of it like honeycomb construction. Should be pretty rigid.

--Buckapound


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