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Old 6th May 2010, 07:45 PM   #1
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Default Newbie looking for help with a bottle build

Excuse the long (first) post, but I like to provide adequate detail for people to answer my questions.

I'm a cyclist and usually ride with headphones when I'm out by myself. Unfortunately, most organized rides don't let you do this. When doing the MS150 this past weekend, I noticed a few people with a bottle speaker as shown here: iH85: iPod portable speaker, iPod speaker systems, iPod audio system

They don't make a non-ipod model and I have no intention of buying an ipod just for 4-5 rides per year. It also seems rather expensive for what you get.

I'm a circuit newbie, and not a huge audiophile, but I do like quality. I've read plenty on these forums, so I think I've got a good starting point.

Here's my requirements:

1. I'm looking for the end product to fit in a bicycle water bottle cage. I'm thinking 2" or 3" PVC would be a good housing.
2. Run it off of standard AA or AAA NiMH batteries (already own, cheap, easy to recharge, and bike-friendly - IE no SLA!)
3. I'll handlebar mount my MP3 player or phone. I'd prefer to control the volume from the player.
4. Adequate volume, not enough to **** others off, but enough to hear going 20MPH.
5. Pretty clear sound, the linked speaker above seemed pretty muddled in a pack.
6. Keep it as a relatively cheap build (< $50 not including batteries which I already own))

Here are my two thoughts so far (but I'm open to other ideas).

Option 1:
3" PVC, about 6-8" long, grid-style drain plug, flat plug
Speaker: Tang Band W2-748SG 2" $16 10W/20W max, 8Ohms, 86dB 1w/1M
Amp: Arjen helder MKII TA2024 $14
Battery: (2) 2x2 AA holders, 8 Total, 9.6V
Various parts, jacks, battery holders, etc.

Option 2:
3" PVC, about 4" Long, maybe 2" PVC instead
Speaker: 2" Generic driver $2 5W RMS/10W Max, 8Ohms, 82.6dB 1w/1M
Amp: Arjen Helder 2x3 for battery application $10
Battery: (1) 2x2 AA holder, 4 total, 4.8V
Various parts, jacks, battery holders, etc.

Questions:
Which would be better for the application.
Is option 1 overkill?
Could the TA2024 handle the speaker's low sensitivity OK?
I'm not a big circuit guy, would option 2's 8Ohm speaker be OK for the 4 Ohm amp?

Things my newbie mind isn't about?
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Old 6th May 2010, 09:55 PM   #2
Pano is offline Pano  United States
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Hello, welcome to the forum.
There have been some similar projects on the forum in the past - bike and roller blade. It can be done.

I see 2 problems for you. Voltage and speaker efficiency. 4.8V is not going to do it. You'll need about 8V just to get the amp running and 12-13V is what you really need. 9.6V is just scraping by.

No matter the amp, there is only so much power you can get out of 12V. So you need efficient speakers. The TB is borderline, but 2 would help - it will be much louder. 6dB louder.

So I would say the plan and the amp are good, just be sure you are at or near 12 volts. And you might post the speaker part of your project over in the full-range loudspeaker forum. There should be some good advice there.
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Old 6th May 2010, 10:20 PM   #3
gooki is offline gooki  New Zealand
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There's also no reason why you couldn't buy the existing bottle speaker and just mod it to have a 3.5mm headphone socket so you can connect to any mp3 player. I suspect it'd be fairly easy to do.
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Old 6th May 2010, 11:16 PM   #4
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If you wanted two speakers, you could make the end of the "bottle" that doesn't have to fit into the cage rectangular and mount the speakers side by side on the side, rather than at the end of the bottle. A couple of possible arrangements are shown. At hobby stores they sell model makers' plywood in various thicknesses. 1/4" should be plenty thick for a small box.

Definitely go for as close to 12 volts if you can possibly manage. You might look at the rechargeable CR123 batteries on eBay. They're cheap and would have a lot more power for their size than regular AAs. Three of those should give 11.1v--close enough for a 2024, I think. You'll have to make a holder for them, but that should be pretty easy--maybe some more PVC tubing and simple contacts.

3" speakers will likely be louder and sound much better that 2", so if you can figure out a way, you'll be the boss guy of the ride.

--Buckapound
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Old 7th May 2010, 01:27 PM   #5
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I guess one of the bigger Q's I had was if the 2024 was a bit overkill and if the 2x3W would suffice. Although, the ability to take it off and use it at a beach/picnic/whatever has merit as well.
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Old 7th May 2010, 01:29 PM   #6
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I would not see the 2024 as "overkill" for any speaker!
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Old 7th May 2010, 03:03 PM   #7
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Quote:
Originally Posted by DallasSoxFan View Post
I guess one of the bigger Q's I had was if the 2024 was a bit overkill and if the 2x3W would suffice. Although, the ability to take it off and use it at a beach/picnic/whatever has merit as well.
I may be understanding this incorrectly, but if you are planning on clipping this thing to the bike and listening while riding sans headphones, then you will be in open air (no walls to raise the spl level from reflection), and you will be competing with wind noise, traffic noise, and all the other noises in the generally high noise outdoor environment.

I haven't built or heard how loud the 2024 boards are, but if you want to hear this thing while sitting atop it and riding, I would say the more power the better.
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Old 7th May 2010, 06:39 PM   #8
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Well, I went ahead and got the 2024. I also picked up a couple of different driver options. I'm going to take the advice and try to use two speakers rather than one. Figuring the space requirements, I really cant get over 2" for the drivers and it is tough to find great sensitivity without spending a bunch. I'll also try my best to get to the full 12V as suggested despite the space constraints. I know I can go to 18650 LiPos or the like, but I'm trying to avoid spending $40 on batteries and chargers when I already have a drawer full of NiMH AAs.

With a 4 year old and another on the way in July, its not likely I'll get much build time in, but it will be fun to play with nonetheless.
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