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Old 21st November 2011, 09:23 PM   #11
duch3n is offline duch3n  Denmark
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I still don't understand why the setup with the 4*6" speakers wouldn't work? what if the cabinet were redesigned so they would support the low frequencies better?
what if i found some drivers that could play lower frequencies? the drivers i chose first was chosen because of the high spl and the low price.
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Old 21st November 2011, 11:40 PM   #12
GloBug is offline GloBug  Canada
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Here's how I would approach it.

Basically I would be building an enclosure for the subwoofer, and adding the stereo part to it. Any 10" or 12" subwoofer will give much much better low end then any 6", no comparison there.

Compare some 10" or 12" subwoofer specs, what your looking for is one that uses a small enclosure. I've had a 10" sub that specified a 1.1 to 1.5 cubic foot box. (depending on the port used and how low you wanted it to play) The second thing to consider would be efficiency, higher the better.

You could even try a 12" woofer out of and old tube console, these are very efficient compared to most modern subwoofers. Now these are only 15w- 25w max speakers and might not compare to the bass your used to out of a modern automotive subwoofer.

So now you would have a box Volume to build your boombox around. You can point the woofer out back. Then add a couple 6" midrange and tweeters. etc to the front. These should have their own little boxes, isolating them from the main woofer chamber. Don't forget to compensate for anything going in the main woofer box by making it bigger.

Get yourself some chipamps or whatever your using and run them from a battery supply that ideally be Lipo, because it's light and powerfull, but expensive. The poor mans route would likely use car type batteries.Heavy and cheap.

That's how I would do it. get your sub and batteries, or at least their specs and sizes and sketchup a new one. based mainly around those two items.

I don't know how portable you want it but for occasional use I would build in around one big or two small car batteries, then find a 12v-24v chip(s) to power everything. You could play around with that after, see whats loudest/last the longest. etc.

I don't know how good a wood worker you are but it would have to be solid if using lead acid batteries. You might want to consider using some half decent 3/4" plywood rather then MDF, it will take the humidity better then MDF. Glue and screw.

Get 2 or 3 cans of boxliner spray and coat the outside, it's a nice textured durable black finish. Might not hurt to paint the inside with something, anything just to seal both sides of the wood to keep it straight.

It's a very doable project. You should be able to build something that last around 2 to 12 hours, depending on performance level you chose.
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Old 22nd November 2011, 08:21 PM   #13
duch3n is offline duch3n  Denmark
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Okay, i have now looked at some different drivers, i have found a 6" (Disconetto.dk tilbyder IMG STAGE LINE 6 1/2'' højttaler - SP-6/100PA til den rigtige pris.)
i found a new speaker enclosure with reflex calculator online, and i said that i should build a 8.91L enclosure with a 5.3cm basreflex.
I dont understand why you want bigger woofers in these kinds of setups?
is it because of the bigger cone, so i can move more air?
the smaller speaker can play low enough in frequencies. the spl can also be high on small sized speakers.
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Old 22nd November 2011, 08:29 PM   #14
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Quote:
Originally Posted by duch3n View Post
i found a new speaker enclosure with reflex calculator online, and i said that i should build a 8.91L enclosure with a 5.3cm basreflex.
8.9l per driver Means it will be bigger than the boominator
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Old 22nd November 2011, 08:33 PM   #15
duch3n is offline duch3n  Denmark
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i cant combine some of that space?
the box was also tuned for +3db at 82Hz, so maybe there should be made some re-calculations.
do you have an easy way(calculator, equations ect.) to figure out how big the box should be for two magnet to magnet speakers?
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Old 22nd November 2011, 08:35 PM   #16
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Quote:
Originally Posted by duch3n View Post
i cant combine some of that space?
Nope

Quote:
Originally Posted by duch3n View Post
do you have an easy way(calculator, equations ect.) to figure out how big the box should be for two magnet to magnet speakers?
Yes. It's in the Boominator thread.

Well, easy and easy. Basically you cannot make anything smaller than 10" drivers work back to back in any reasonable sized and dimensioned box. It's not like I haven't tried.

Last edited by Saturnus; 22nd November 2011 at 08:51 PM.
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Old 22nd November 2011, 09:00 PM   #17
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It's not that I'm unwilling to help but it would be a good starting point when designing a loudspeaker to learn the most basic principals that makes it work. Then you'll see why it's amazing why the Boominator works, and works so well.

You see, I have worked both professionally and privately designing loudspeakers for 12 years before I decided to build what I consider the ultimate boombox. And even then it took me 6 years (naturally not constant work but a slow process of trial and error, and recalculations) before I got it completely right.

I even had to throw out most of the commonly know speaker theory because it's not suited for this use, and develop my own formulas in the process.
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Old 22nd November 2011, 09:30 PM   #18
duch3n is offline duch3n  Denmark
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i have read most of your boominator thread, and i am very impressed. i am not aiming at anything in that class.
you've got me hooked on tuning the box correctly, and i have been googeling and reading since you posted that it was described in the boominator thread.
i havent found anything useful though, can you give me a hint again?
i am also considering not doing the magnet to magnet setup, just because it would be to much trouble(might work on that when i get a hang of it). two subs with 94db spl and tweeters with an spl over 90 with a 2*20w T-amp, would also be able to play music for a small camp on Roskilde festival.
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Old 23rd November 2011, 12:17 PM   #19
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One thing you might do is to take a look at some existing speaker designs that are about the size you are thinking about. There are plenty of plans out there. Zaph|Audio is a good place to start for small speakers, and search if you can find a small "Onken" design, as those are well-liked. As I recall, Parts Express had a boombox design maybe a year ago. And I do remember someone on this forum build a very beautiful one similar to your design a year or two ago, so search here as well.

If you find a speaker that has the specs you can live with (remember, the specs of high efficiency, low bass and small size we all would like are unobtainable), then you can redesign them, keeping the same volume in size, but making them taller, thinner and so on (within reason) to suit your designs. Also, a proven design already has the crossovers designed and tweaked. You just have to put it together.

You should be aware that there are modern speakers at 4" or 5" that have very good, wide range performance. Small speakers don't makes as much sound as big ones, but they work in much smaller boxes.

I would recommend a TriPath 2020 or similar amp. It's the most power you can get out of 12v. Going with a 24 v system really complicates things, and for a small box shouldn't be needed. I think your plan for LiPo batteries is fine. If they're easily to change, then you can have several, and plug in a new one when the first one runs out of energy, then hook it to a solar charger.

The tubes you mention are called "bass-reflex ports." FYI, a sealed box will give you more bass in a smaller box, but with less efficiency. Doesn't physics suck? The best designs are the ones that manage the compromises in the best way.

--Buckapound
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Old 23rd November 2011, 01:53 PM   #20
duch3n is offline duch3n  Denmark
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Thank you Buckapound! very usefull!
i have now found some new measurements, and i am almost ready to make new drawings of my compromised boombox.
there is just 1 thing i couldn't find online; how does the bas reflex affect the enclosure?
lets say we have a enclosure(without reflex) tuned to 0db at 82Hz, and you put in a bass reflex port, does it affect the tuning of the box?
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