Thanks, I'll probably go with this one and get 12 cells instead of 10 that way I can make it 7.2v since you need at least 7v, which I think also increases the capacity when its stepped down for the charger?
http://www.parts-express.com/pam8610-2x10w-class-d-audio-amplifier-board--320-604
The benefit of 1.5 V NiMH batteries is that they can deliver constant relatively high current. The voltage can be stepped up and regulated, but for that, you also need current, because stepping up the voltage eats current. At least with NiMH, you don't have to worry about a thing, with Li-Ion, you would need constant battery monitoring and you would even have to have venting holes in your enclosure to keep the speaker from exploding when the battery vents, and there are a lot more things to look out for in Li-Ion batteries, like for instance if it uses only safe chemicals or not, because when a battery vents, you want to be sure a house fire is the worst that can happen (as in, you don't want to find yourself poisoned in a house fire).
So in order to calculate the optimal battery arrangement, you have to look at the current requirement of your amp, and then calculate back to what current output you need before your step-up converter. More volts means less current, so longer battery life and more flexibility, so I would go for more stacked cells if the capacity of those cells is lower. In the end, the volume they're going to take, will be about the same (because obviously it's the volume of chemicals in the batteries that counts), it's purely a question of practicality. That being said, the larger the cells, the more volume they will have for the surface area, so the less cooling they'll have and the less efficient the occupied volume will be. It's a practical balancing act depending on your design.
Can't you find a tripath module (also called Class D Tripath or Class T)? Those are ridiculously efficient and not more expensive, and the audio quality is stunning.
which would you recommend
http://www.parts-express.com/2x8w-at-4-ohm-tpa3110-class-d-audio-amplifier-board--320-329
http://www.parts-express.com/parts-express-2x15w-at-4-ohm-ta2024-class-d-audio-amplifier-board-only--320-330
http://www.parts-express.com/dayton-audio-dta-2-class-t-digital-audio-amplifier-module--300-385
and I'd like 70mm speakers I don't know how to discern POS ones from decent ones and does it matter if they are rectanglar or square?
The original Tripath modules are well known and they are the 100% true implementation, but I kind like the Texas Instruments implementation, it's more efficient, uses less power, and doesn't get hot at all, on a smaller form factor, and it's more than enough power for small efficient speakers.
As far as the speakers are concerned, a lot of the performance depends on the cabinet. There is an open source cabinet design software made by a Finnish bloke that is easy to use if you want to get the most performance, but there are also several excel-templates on the web to calculate your cabinet for a fast and easy fix. What kind of cabinet were you thinking to make, something really easy and simple, or something with more acoustical performance? The choice of driver depends on what cabinet you had envisioned really. I normally use Visaton drivers for almost all audio projects I make, because they're really good quality for a fair price, but to be honest, if you're not going to calculate your cabinet, they're overkill. A trick for when you don't feel like calculating or building a tuned cabinet, is to use car speakers. Car speakers are often tuned for free air operation, also called "infinite baffle", and that's the easiest implementation possible. Infinite baffle means that you don't need to even make a closed cabinet, these drivers will attain a high SPL even without enclosure (which doesn't mean that they will get full spectrum, that depends mainly on the size of the baffle board). Another popular quick fix is to use tubes, like PVC or acrylic pipes or alu pipes, which can be cut to length for an instant tuned enclosure for use with bass reflex optimized drivers. Pretty new to the scene are resonance drivers, which are very small and efficient, and are placed on a table or glass sheet or box to use the resonance of the substrate to provide better performance. What kind of design would you prefer?
well its janky as hell, but for the prototype I was thinking about using rubbermaid food storage containers (paint it because I don't think the genneral public would react kindly to a container with wires, nobs and dozens of "cells" inside)
Eventually a 3D Printed plastic box, so I guess either way plastic, I have access to a ton of cardboard so I can line the inside of it with that if that would help, I also have a lot of hard foam they ship with GPUs neither would make suitable cabinet but if lining the inside would help then I have it
I've never done this kind of thing short of wiring up D batteries to my GBA or charging my car battery with a PC power supply (it was an emergency) so I don't want to invest in a cabinet just yet until I've got everything working in top form
ok, so a closed simple cabinet, which means air suspension. Smaller car speakers would do, so would classical radio speakers. I'll take a look at some drivers and will post a few links. If you're going with LD-PE (food container) or ABS (3D printed), you're going to have a lot of internal resonance from the material, so it's important to have a driver that's as isolated as possible and yet efficient.
i also have some soft foam that looks like the sound insulating foam, also ccame from gpus, or would cotton swabs work better
the most important function of foam is to dampen, it dampens unwanted internal reflections and keeps the cabinet from acting as an acoustic amplifier for unwanted frequencies, but it also reduces the efficiency. glass wool works better than foam. What you do need, is some kind of sealing under the driver flange, so that no air bleeds around the driver. Since the cabinet is going to be 3D printed, it's probably going to be hermetically sealed as it is.
this stuff?
http://www.ebay.com/itm/15g-Glass-Wool-Quartz-Wool-High-Temperature-Glass-Fiber-Filter-Cotton-B2B-/171430240535?pt=LH_DefaultDomain_0&hash=item27ea09e117
Speakers are like headphones everyone has their opinions. My advice would be to select a size that is common so you can experiment with different options. If you are going with a 12v 2a option my pick would be these
http://www.parts-express.com/hivi-b2s-2-shielded-aluminum-driver--297-432
its shielded which is a plus
http://www.parts-express.com/tang-band-w2-1803s-2-neodymium-poly-full-range-driver--264-885
http://www.parts-express.com/grs-3fr-4-full-range-3-speaker-driver-4-ohm--292-436
this one is a nice wattage and price
http://www.parts-express.com/cat/cabinet-damping-material/311
you can also just use pillow packing from a sewing or craft store it will be cheaper just make sure you separate the powered components for fire safety.
Some designs require no dampening or very little like folded horn cabinet designs
https://www.madisoundspeakerstore.com/full-range-speaker-kits/fostex-bk-12m-folded-horn-cabinet-each/
I think one of those only went up to 16,000hz is it okay they don't go all the way up to 20K?
There's very, very, very little happening above the 16kHz range. Many people can't here much above 15kHz anyways, so I doubt that last little bit of range would matter much.
http://www.noiseaddicts.com/2009/03/can-you-hear-this-hearing-test/
so what happends when it DOES try to play something above 16,000hz?
yeah or something borrowed from a building site lolz...
Literally nothing, it can't play it, but that's not a big deal at all for this kind of application. I'll look around for a set of speakers that would be suitable later on today and will post what I would use.
well I was just concerned it would buzz, like these shitty HP speakers I'm using atm for my PC, but I guess its just because they're shitty
You can always add a tweeter and a crossover if your looking for more range
http://www.parts-express.com/tang-band-13-1761s-1-2-silk-dome-tweeter-pair--264-841
and
http://www.parts-express.com/cat/crossover-components/21
are these legit 10Ah NiMH C cells?
http://www.ebay.com/itm/10-x-C-size-1-2V-10000mAh-Ni-MH-Red-Color-Rechargeable-Battery-USA-/121220180405?pt=US_Rechargeable_Batteries&hash=item1c394929b5