# My Rockbox Build (boombox)



## hankbot (Jan 6, 2013)

So, I've been reading a lot about the Boominator and other boom boxes people have built and decided to make something of my own. So far everything is ordered and am waiting on the speakers to come off of backorder. Here's the equipment rundown:

Midbass woofers - Dayton Audio PA 255-8 1 per box

Full range drivers - Fountain FE85 2 per box

Amps - Lepai LP-2020A+ one per box

Crossovers - Audiopipe XV4BXP , run the Daytons up to 200hz, and the full ranges from 200hz and up. 

Battery - Power-sonic 18ah SLA

A simple voltmeter to watch the battery level.

Power switch

Cabinet feet

Some of these handles and a pair of casters to make lifting and rolling them easy. 

Panel mount power jacks to power the second amped box from the first and to charge the battery. 

3.5mm panel jack to provide the signal from the first box to the second. 

Some fuse holders for safety. 

A 12' 3.5mm cable for the audio signal to the box with just the amp inside. 

A DIY 12' power cord to connect power to the amp in the box with just the amp inside, some RCA jacks I'm robbing from some these cheap RCA wall plates, some wire, paint, and 1/2" birch plywood. 


The next post will describe the goals and design.


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## Old Skewl (May 30, 2011)

Good luck. Can't wait to see the finished product.


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## MinnesotaStateUniversity (Sep 12, 2012)

Just buy a logitech z2300 & swap drivers


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## hankbot (Jan 6, 2013)

This is what I get for not getting my second post up sooner thanks to yard work. 



MinnesotaStateUniversity said:


> Just buy a logitech z2300 & swap drivers


*So I started this with a few goals in mind.*

*1.* It needed to be a mobile system, able to run at least 5 hours at full volume, and it would be nice to have 2-3x that at normal listening levels.

*2.* It needed to be able to be heard over a large area, so high efficiency was a must to be able to keep amplifier and battery requirements reasonable in weight and price.

*3.* It needed to withstand an outdoor environment including occasionally getting a bit wet, muddy, dusty, or whatever. I don't plan to use it in the rain per say, but it needs to withstand a short watering if I get caught in the rain while packing up from camping or whatever. Ultimately I may sell this to a friend who would use it for Ultimate Frisbee tournaments, so it will also need to be able to withstand the potential hit with a frisbee, foot, or beer bottle.(you know how it is with those guys)

*4.* It needed to have good sound quality outdoors, and have the ability to double as home speakers that mate well with a sub.

*5.* It needed an easy way to be transported over medium distances through grass, dirt etc. As well as being set down in less than clean places, so feet would be needed to elevate the speakers when in use.

*6.* It needed to be idiot proof. I know that I had other ways to wire everything up, but with the known problems surrounding the removal of the speaker leads from the Lepai amps if they are on, and peoples ability to trip, miswire, and generally screw things up, I needed it to be impossible to mess anything up thanks to some numbnut hooking things up wrong out on a field.

I posted links to most of the parts in the first post, most of the links webpages include FR graphs, T/S parameters, etc for the equipment I'll be talking about below.

*So I'll start with the speaker selection.* The Dayton Pa255 speakers are one of the few strong 10" PA speakers in the 70-200hz region. I spent a lot of time looking at the alternatives and very few could match it's sensitivity in this range. The icing on the cake was that it in addition to having higher sensitivity in the range i needed, they were also cheaper than most of the alternatives, and MUCH cheaper than anything that could actually come close in performance. The downfall to these is that once you look above 200hz, the big bump in the 150hz combined with the following dip and then next peak at 480hz makes me think they would not necessarily be what I'm looking for for flat response if I crossed it too high, so that meant full range drivers that could dig from 200ish-20,000hz and were reasonably flat throughout, or a 3 way setup was needed to get the SQ I was looking for. With a reduced enclosure size and the right tuning I can boost the 80-130hz range to flatten the response out, and give it more presence outside, which should make it reasonably flat (slight downward slope after 150Hz)to 200Hz. Although this may have a tendency to overemphasize the low-end when paired to the other speakers, I'd rather have an abundance of power in reserve in this region and cut the mid-bass if it's too strong than hope I can boost it and still have it sound good. In box SPL @ 1watt @ 1m @ 100Hz should be about 99db, 99db at 150Hz, and right around 96db at 200Hz. The great part about these drivers is that I will still have an output around 96db @ 80Hz @ 1watt.

The Fountek FE85 (not fountain as auto-correct changed it too in my first post) ended up being the way I went for multiple reasons. It has a good FR, from about 150hz-20,000hz it is reasonably flat with it only getting really out of line above 10kHz, and even that should be tamable with the Lepai treble controls. They were also cheap, 4 of them from PE were only about $50. Worst case scenario would be modding the caps in the Lepais to change the frequencies they are effecting if they do not filter enough of the 18k peak out. Using these in a small sealed box to increase the Q will boost output around 250-500Hz, helping them blend into the woofer a little better. Using a pair and looking at the sensitivity, I should have an in box SPL of around 94db @ 200Hz at 2 watts(these would be 4ohms, the woofers only 8, so comparing them apples to apples for actual output). The response is +/-3db up until 10k where it peaks, and again as it rises from 12k-18k.

WINISD Plot of drivers in their enclosures.









So with the Lepai amps running a legitimate 4 watts at 8ohms and 8 watts at 4 ohms, each side will get a total of 12 watts RMS before clipping makes it sound like doo-doo. This means I should be able to rock out with a max output of around 110db at 1m. At 50m (or half of a ultimate frisbee course away) this would still be 75db, or about a normal conversation level.

*The Lepai amps have a reputation for great sound, low power consumption, and low price.* These made them an _almost_ easy choice as amplification. I kept wanting to go bigger on the amp but every time I looked at another idea, they just kept getting more expensive, heavier, more complex, and a bigger pain in the ass to fix if it ever broke. Most other cheap amps that are producing 25+ watts per channel have major flaws like higher price, lower sound quality, the need for 2 batteries or more to get 24v or higher power, and much reduced playing times. The Lepai amps will be set up so that each one drives a woofer/fullrange combination, one per box. The advantage to this is that I'm just running the signal and power wires to the Lepai in the second box, so if it gets accidentally unplugged it wont kill the amp. This also means that if I don't want to drag, or don't have space for both boxes in the car I can just take the base box which has the battery, crossover, and one Lepai in it and I have a smaller portable system that will be within 3db of the full setup and can play for almost 10 hours at full volume on a charge. I will use the same 2.1mm jack that hooks up the second Lepai as the charging input jack for the battery, and 3.5mm stereo jacks and cable to send the input signal from the first box to the second. If for some reason I decide these do not provide enough power for my needs, I'll be looking into small car audio amps around 4x40 watts RMS, and glad I kept the system at 12v.

*I spent a lot of time debating crossovers.* I finally decided on going with an electronic crossover when I found the Audiopipe XV4BXP. I'm still unsure of what to expect for the sound quality from it, but it gives me a lot of flexibility for the cost of a single decent passive crossover, so I decided to gamble. If it turns out that it is a piece of garbage I'll go back to the idea of passives, or a different electronic crossover. I'm planning to use RCA inputs on the face of the Rockbox for the input, which will run internally to the crossover. The crossover will split the signal, running the woofers from the subwoofer channels low-passed around 180-250Hz depending on what sounds the best, and the Fountek drivers will play from around 200-250Hz on up. One output from the sub channel and one from the front channel will go to each Lepai amp where I can use the output controls if I desire to shape the sound any more. I can use a combination of the crossover and volume controls on the Lepai amps to balance and level everything out.

Most of the rest of everything is just wiring and making dust and metal chips. Here's an early model of the box design. I have a lot more playing around to do to optimize space and ease of assembly, but it gives you a feel for the size.










Anyone have any recommendations for the most durable paint or covering they've ever used? I've used rattlecan epoxy paint before, but I'm expecting this thing may see a lot of abuse over the years and after I seal the box inside and out with actual real epoxy I want a paint that won't just peel, flake, or chip off with some abuse; or a tough vinyl or something along those lines.



More to come.............


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## Jachin99 (Dec 13, 2008)

Plastidip?


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## hankbot (Jan 6, 2013)

Jachin99 said:


> Plastidip?


That is a worthwhile idea. I'll check into what it would cost to cover them.


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## myhikingboots (Oct 28, 2010)

what about bedliner?


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## myhikingboots (Oct 28, 2010)

or even carpet.


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## Old Skewl (May 30, 2011)

Just curious how this project turned out. I've got the itch to do a DIY ipod dock or boombox project this winter.


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## hankbot (Jan 6, 2013)

Old Skewl said:


> Just curious how this project turned out. I've got the itch to do a DIY ipod dock or boombox project this winter.


I wish I could tell you. I have all of the parts purchased, but I had been spending a lot of time and energy for about 9 months learning audio theory and working on my active 3 way setup in my car, and I could tell that my wife's patience was wearing thin on audio stuff so I switched gears. I just need to finalize the box design and do the woodwork and wiring. I think it's going to be a late winter project. 


I've been working on knives for a few months now. I finished my first one, an all stainless construction automatic with a CPM-S90V blade. I've got materials and designs for 4 more in the works, 1 manual folder, and 3 different fixed blades. All I'm asking Santa for this year is the rest of my blade steels to get delivered before Christmas. 

Oddly enough, my wife seems open to the idea of me making knives for a living. I was shocked when the first thing she said about my finished knife was that it was "beautiful". Not what I expected from a lady who hated me buying an airsoft pistol. 










Yes, I know it's missing a screw, this was during initial tuning, and I was removing that handle side frequently. 











Manual folder, dxf of open and closed, no lines hidden to show inside clearances. CPM-S35VN blade, G10 handle sides. 











A fixed blade inspired by my cousins Christmas tree farming needs and named after his baby son. CPM-3V blade, G10, micarta, or Osage orange scales. 











Some slicers for EDC, or fine skinning/cutting work. CPM-S90V blades, same handle scales options as the other fixed blade.


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## Old Skewl (May 30, 2011)

Nice looking knives. It is amazing what DIY projects are are out there.

If you ever restart the rockbox keep us posted.


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## hankbot (Jan 6, 2013)

Old Skewl said:


> Nice looking knives. It is amazing what DIY projects are are out there.
> 
> If you ever restart the rockbox keep us posted.


Not a matter of if, but when. Sometimes it just takes someone showing interest in one of my projects, and all of a sudden I start finding time to make progress. 

Thanks for helping keep this high on my priority list!


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## Old Skewl (May 30, 2011)

No problem. Mind if I ask what kits your using for the knives. It would be neat to try one.


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## hankbot (Jan 6, 2013)

Old Skewl said:


> No problem. Mind if I ask what kits your using for the knives. It would be neat to try one.


No kits, I'm designing and making from scratch (well I'm not forging, I'm making from raw barstock not making my own steel, so almost from scratch). 

I happen to have some equipment in my garage like a manual lathe and mill, and a CNC mill. Helps keep me out of trouble and always learning.


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