Modding Ghetto^2 blaster 2, OMG it's done! Update 6.2.

Ok first of all I'm not too sure if this is the right area. Might also fall into general discussion or project logs, moderators are welcomed to move this where ever they wish.

The story behind this mod is that a friend of mine wanted a ghetto blaster and had all the parts, but not the time to put it all together. He also had an extra case of cranberry long drinks. Me, on the other hand had all the time in the world, most of the tools and lacked the case of beverages. See where this is going?

In short: I got the materials and electronic parts and the drinks and the task of designing and building the case.


Actually the only plans I had when I started building it were a couple of lines and measurements on a piece of paper. I just did this model when waiting for the glue to set.



The speaker components for this blaster come from a Thomann T-Box PA-speaker. For travel use there's a Sure-electronics board amplifier (not sure of wattage, but definitely high enough) the batteries are some RC-bars and there's also a voltage meter.



Based on those, rather vague, plans, I first built a cardboard model to see if all the parts would fit.



Anyway also this cardboard model went out the window after I took a look at the plywood sheets I had. In the end I re-designed the whole thing as I went, mainly focusing on minimizing the amount of sawing. Why so?



Well, take a guess. The thicknesses of the plywood sheets used are 4, 6 and 8 mm, with the front and rear panel being 8 mm, top and bottom 6 and sides 4 mm. The materials used are way thicker than required, but those were the ones I had.



After cutting all the required pieces, it was time to see if they actually fit together and if the parts still fit inside.



After making sure it can be done, it was time to start gluing. On the corners I used 15*15 mm rods for support. I might have been able to just glue and screw the plywood sheets together, but was pretty certain there would be crack somewhere.



One of the requirements set by the friend was easy access to the internals. That's why I made the rear panel/roof easily removable. There's a strip of window seal that should keep things air tight.



And just to shock you awake after all the boring nonsense, here's me in the middle of our chaotic modding shack. Dremel shirt and track suit pants are the fashion style of this autumn.

And as always, if you looked, you've got to comment or I'll come into your dreams.

 

What if I want you in my dreams?



Oh, snap!

 

What?! I have to comment or you will come in my dream? Wait...

Modding on the floor is handy but after a while your legs and shoulders start to ache.

 

Smilodon: yea no worries, I'll be careful to be as annoying as possible.

Javerh: the floor modding comes handy when all the desks are in better use. Also atleast the floor is pretty much level, so you can espect it to serve as a 90 degree angle..

 

Nice little box

You know, if you post it on a forum of audiophiles, then you will definitely haunt thier dreams

 

Wow, nothing for years and then two projects at once!
Of course I'm only commenting to keep my dreams Jipa free.

 

Here's yer comment:

Stay out of my dreams. Please.

 

The darkest hour struck this morning. The glue had set, the pieces were in exactly the right places, the clamps hadn't twisted them off mark and I was a proud owner of two left side panels! Damnation. After that I went ahead to make a hole for the bass driver. Made a too small one at first, spent lots of time making it large enough.

Oh well, pics maybe later on.

 

Neat little setup. Are you going to remove the fan and add a larger heatsink?

-You don't want in my dreams. In last night's dream I forgot to mow the yard, and it started eating people.

 

Meh my own dreams were bad enough last night, too busy seeing nightmares to give others any

The amp is a 2*100 W unit (http://www.sureelectronics.net/goods.php?id=1133) I haven't tried it myself, but I'm pretty sure it will not be pushed to the max so heat isn't going to be a huge problem. It might even survive with the stock heat sink without the fan.

 

It's a class T, so it's not especially energy efficient. But it should be okay I guess Anyways, you won't be able to hear the fan.

 

I'm sorry to dump on your amp Jipa, but that amp is nowhere near 100w x 2

It's just like pc power supplies, where some companies will quote an actual maximum continuous reliable & safe power capability, where others will go so far as to state the maximum as how much power can be output momentarily before failure. Barstads

At 100w, the THD is <10%, and they haven't even stated the frequency range for this
So in other words, this power figure is absolutely meaningless, A$$holes

If you scroll down the specs, there is another maximum figure of 70w @4 ohm @.005 THD... now that is a clear HIFI amount of THD, but again, no frequency range stated, so the figure is still quite meaningless

Scroll down some more, and you find this:

THD+N<0.01% RL=4Ω, f=1000Hz 50W

Well we aren't looking at HIFI levels of clarity anymore, but .01 is still ok, and we finally have a frequency range.... but it's supposed to be 20hz - 20khz, not just @1khz

Generating power at 20hz is many, many times harder than at 1khz... so it's actuall power ouput would be roughly 5w x 2, but seeing that most car decks you see quoting 50x4 are actually 5x4, well 5x2 might be loud enough for him? I do only see a single channel however... so aswe can see, you'd have about 5wx1 Enough to blast a quiet ghetto I guess.

When I first saw that heatsink, I thought to myself that it couldn't be much more than 5w x 2, and I definitely wouldn't be removing the fan unless I was going to be putting on a bigger heatsink - which would be a nice idea btw, to save some battery life.

And on the infra red image, you can see the two little surface mount diodes are cooking at 78.2... I assume that's celcius... so i'd stick some heatsinking on there or replace the diodes with a decent pair.

Notice that they haven't mentioned the power output in this photo... maybe that's how hot things get at 1w?

 

Thanks for the great wall of text, but I'm very much aware that a piss-cheap Chinese amp with an antique chipset cooler is NOT going to do what it says in the tin My friends have built a number of blasters (with the Drakmin's version also having its own project log here), and based on their experiences the wattage just isn't going to be a problem here. And sound quality? Well.. that is hardly even a factor. The part choices for this build are based on the sensitivity of the drivers and the sensibility of the price of the power/amp side of things. More money would buy Li-Po's for lower weight as well as more efficient, better quality amplifiers.

I'll try to get something done tomorrow, but it seems like as soon as I started to build things to keep myself busy, also all the manufacturers in the world decided to make me busy with the review stuff as well. Those two, and the new students arrived on monday, which means there's something to do every about night. But now it's time to hit the bed, Good night.

 

Got something done yesterday.



The high end is delivered via this guy. It's was cut from the original box by an axe murderer, which made fitting it particularly tricky.



So instead of even trying to fit it, I just free-handed a hole for the driver itself to see and hear how it would work out.



Not so bad. The future owner told me it's OK, and saved me about three eons of working time. There's going to be a mesh in front of the drivers, so the hole isn't going to be visible either.

Pretty hung over again, but later on today I'll try to soldier on with this.

 

Hey Jipa, there seems to be four little allen head screws securing that tweeter to the cut plastic! I dunno why the tweeter was removed by cutting it's previous box, instead of just being unscrewed
The way you've got it will reduce the tweeter's dispersion/you won't hear much treble unless the speaker is pointing towards you... but yeah, sound will still be heard as it is.
The other thing i'm wondering is, why didn't he just get a mono amp? A single channel 10w unit would have been cheaper and louder.

 

Oh it seems you aren't too familiar with cheap Chinese things after all The allen head "bolts" you see there are fake, they are just a part of the plastic. I rofled when I noticed that, it's such a lame trick. And we also figured that would happen with the treble without its whtchmacallit horn, but in use the difference just didn't seem to be worth all the effort.

And as for the amp, I'm not sure. He also had an AMP-6 kit from 41Hz audio but he decided to use this instead. I think it had to do with the battery voltages and whatnot, but I'm not 110% sure. Also we thought of an idea that the stock x-over could be replaced by a line-level crossover, which would be much smaller and lighter. This could be done by having one amp channel for the bass and one for the treble. The original crossover weights half a kilo!

 

Got a massive de ja FFFFFFUUUUUUUUUU effect when I noticed the blaster requires a couple of aluminum pieces. First of all the batteries are heavy and need to be properly mounted so they don't get loose and break stuff.



This is the idea. Missing from the pic are some sort of straps to keep the batteries in place. Gotta figure something for this. Velcro would work fine, but I don't have any.



To make the holders a bit more cozy I cut some felt stickers to go around the holders.



After that I made a plate for the input connectors, power switch, fuse holder and voltage display. Making the large holes was a nightmare as I don't have a large enough drill bit. Required some careful Dremel-action. Side note being that the Dremel 4000 soon became my rotary tool of choice.



And here's the connector plate in place. There is however a huge design flaw. You don't want to have such a pool on top of an electronic device! Especially not if you plan to carry it around in student happenings, where it will inevitably be used as a can holder, and where some beer is inevitably going to spill on it. I'm still thinking if I could make some sort of mud flap to cover these connectors

Oh and I think all wood pieces are now glued. Next job will be to mount the two half together so that they can also be opened and then it's time to sand and prime the thing. Not looking forward to that, as I'm pretty sure my lungs are already full of various grains of wood and aluminum dust, held together with a healthy dose of urethane glue fumes.

 

I've seen that once! It was a major OMGWTFUUUUUUUUUUUUUU?!?!?!?!? moment for me

You could get an active/line level xover, and use one channel for low end, one for high, but this won't make any significant difference.
Very little power is used by the tweeter, so having them both on the one channel or split doesn't really make a difference. They are two channels sharing the same psu on the one pcb, so there wouldn't be any improvements in clarity either.

You know, you can ditch the xover altogether with those speakers, just connect them directly!

The downside would be that the woofer is receiving high end sound, which it can't play as clearly as a tweeter, but I think this would help make up for the tweeter's reduced sound output due to the small hole it's behind.
The tweeter is a piezo, so it's not affected by bass, and you probably won't notice that it's recieving more midrange than it used to, not just because of the small hole, but it gets quieter as the frequency drops.

 

Yeah the passive line-level xover would only be made to reduce weight. I've just never seen it done as in normal use it's plain stupid, but here it would make sense.

 

I'm saying you can ditch those passive crossovers, just wire the output of the amp, directly to the tweeter and woofer in parallel, just like how they were wired to the crossover.