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Old 27th February 2012, 10:04 PM   #1
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Default Simple, portable, rechargeable, Hi-Fi speaker

I have an idea for a speaker project (similar to this one), but with many differences. In a nutshell:
  • Hi-fi 4-ohm, 20W speaker (Tang Band or Dayton?)
  • Internal amplifier (can be IC)
  • RCA and TRS stereo input jacks (female)
  • Power and volume control knob with indicator LED
  • 12v internal rechargeable battery (easily replaced)
  • Coaxial power plug
Sound
Audio should be 80db at 5 meters, if possible.

Battery
The internal battery charges while plugged into an external electrical source. The speaker can be used even while charging.

The battery should last at least 8 hours between charges. Ideally, the battery would have a 10,000+ cycle lifespan.

Power
20W?

Usage
The speaker is meant to be used outdoors (beaches, in the rain, etc.). So it needs to be durable and rugged.

It must play music from between the 1920s and 1950s (traditional jazz; Benny Goodman, Ella, Etta, Ellington, etc.) and have it sound good, with as much bass as possible.


Physical Specifications
The speaker should resemble something like this:

Click the image to open in full size.


Documentation
I have started a document for this project, but I hardly even know where to begin! I have posted the design document online: Simply Sound.pdf

Any advice, feedback, suggestions for equipment, or even links to existing speakers that fit the bill would be great.

Thank you!
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Old 27th February 2012, 10:44 PM   #2
gootee is offline gootee  United States
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First you should check to see whether or not the battery would be feasible.

Are there 20 Amp-hour 12-Volt batteries that would be within your size and weight constraints, that can be recharged 10000+ times?
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Old 28th February 2012, 02:03 AM   #3
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Quote:
Originally Posted by gootee View Post
First you should check to see whether or not the battery would be feasible.

Are there 20 Amp-hour 12-Volt batteries that would be within your size and weight constraints, that can be recharged 10000+ times?
I was told that the following battery would work:

HobbyKing R/C Hobby Store : ZIPPY Flightmax 6200mah 1S 30C Hardcase Car Lipoly
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Old 28th February 2012, 02:11 AM   #4
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Quote:
Originally Posted by gootee View Post
First you should check to see whether or not the battery would be feasible.

Are there 20 Amp-hour 12-Volt batteries that would be within your size and weight constraints, that can be recharged 10000+ times?
I'm running a TUUB (Haut-parleur multimédia portable Edifier MP300) off of a battery similar to the following (technically, a Discover D1272):

MK Battery ES7-12 12 Volt 7.2AH

Sounds like a tin can, though.
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Old 29th February 2012, 02:38 AM   #5
gootee is offline gootee  United States
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Quote:
Originally Posted by thangalin View Post
Well, that one is only 3.7 Volts. So maybe four of them in series would be good, for 14.8 Volts with 24.8 Amp-Hours.

You might be better off (price-wise) if you used a higher-voltage battery. Two of the "2S" ones that are 7.4 Volts each, in series, would give you 14.8 Volts. They have 5000maH (5 Amp-Hour) ones that are about $15 each. If you used four of them, you could have two for positive and two for negative and have +/- 14.8 Volts (a bipolar power supply), which might be a good thing.

They do also have higher voltages and larger capacities (i.e. more maH) available, at that site.

The "3S" ones are 3 x 3.7 Volts, or 11.1 Volts each. But then you can only get about 8000 maH (8 AH). It's probably better to use two or four of the lower-voltage (1S or 2S) ones in series, so you can sum the maH ratings, since you would need to use something close to 20000 maH, to guarantee your desired 8 hours of music at max power (with 12 Volts and a four ohm speaker).

I'm not sure about using those batteries in parallel. But if that's OK to do, then you could also get some that are already the voltage you need and parallel them, and sum the maH ratings. (Or, you could just swap them out, or have a switch to change over to another battery, or whatever, if they shouldn't be used in parallel.)

Maybe someone else will chime in with more information about any possible problems with running those LIPO batteries in series or parallel.

It looks like the lowest-priced ones are usually around $15 each, for about 5000 maH.

Last edited by gootee; 29th February 2012 at 02:45 AM.
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Old 29th February 2012, 02:59 AM   #6
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Location: Chicago, IL
I believe Lithium Iron Phosphate (LiFePo) batteries offer the longest useful life right now. The LiPoly type have higher energy per weight initially, but fall off faster. LiFePo can't be overcharged and burst into flames.

Check out the Boominator thread over in Class D. Different project as far as the case and speakers, but the lots of good info on the internals, which won't be all that different in your case. Can't beat a Tripath 2020 amp for the money/size/efficiency/quality.

--Buckapound
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Old 5th March 2012, 10:19 PM   #7
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Quote:
Originally Posted by Buckapound View Post
I believe Lithium Iron Phosphate (LiFePo) batteries offer the longest useful life right now.
Good to know, thank you.

Quote:
Can't beat a Tripath 2020 amp for the money/size/efficiency/quality.
I am looking to make the object shown in the image as closely as possible. Embedding an entire amplifier wouldn't fit the bill -- I'm looking for a high-quality chip that would work well with a Tang Band full-range woofer (or the like).

I appreciate your input and well check out the Boominator thread.
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Old 21st March 2012, 08:59 PM   #8
dangus is offline dangus  Canada
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Also the TA2024 Tripath. Search eBay and you can buy a board ready to use for under $10 including shipping.

Keep in mind that a 10 watt amp will be drawing a much lower average power since music does not consist of full-power sinewaves; average power may be more like 1 watt. A common 7AH 12V sealed-lead-acid battery is easier (and safer) to charge than any exotic lithium rechargeable, though rather heavier.

For speakers, OEM car stereo speakers do not enjoy a great reputation, but I think they're worth considering. A couple I found at a thrift store recently seemed nearly ideal for portable use: 4 ohm 20W rating, stiff but lightweight composite frame (glass-filled plastic probably), and what caught my eye first: a tiny neodymium magnet structure. I haven't listened to them, but the main drawback is that the frame is designed to mount under the rear deck of a sedan, so using it in a normal box may require spacers and a lot of sealant.

If you want to make the case look vintage, check out places that sell stuff to guitar amp builders and restorers.
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Old 21st March 2012, 09:09 PM   #9
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Quote:
Originally Posted by thangalin View Post

Embedding an entire amplifier wouldn't fit the bill
This amp circuit boards are quite tiny. No problem fitting them in a very small box like yours. And if a heatsink is needed at all, the type used for computer memory chips can be stuck on the Tripath chip.

--Buckapound
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