- This topic has 28 replies, 4 voices, and was last updated June 8, 2011 at 8:23 am by Anonymous.
May 14, 2011 at 7:05 pm #1050872Anonymous
So i’m looking build a little soundsystem, i’m talking a few hi-fi speakers here enough volume for a small stomp for a few people but nothing for a big party. looking to power it off maybe a car battery or similar. i know literally nothing about how to do this though, how can i get the best volume with least amount of power? if i have say two 100w speakers does my amp need to be 200w or only 100w? where does impedance come into it? how would i power the amp off the battery? e.t.c
thanks a lot for any help
raaaMay 14, 2011 at 7:25 pm #1239065May 14, 2011 at 7:50 pm #1239068Anonymous
Yeah thanks i’ve taken a look at them. What sort of characterists shoudl i look for in an amp? TA2020 Class Hi-Fi Stereo Car Amplifier Mini T Amp | eBay UK How’s lthis for example?May 15, 2011 at 11:50 am #1239066spangleParticipant
I don’t know much about the technical details but cheap Chinese products like that are notoriously unreliable and it doesn’t look like that one could power very much. Try asking on speakerplans they’re quite helpful, it all depends on your budget but tried and tested brands are probably a safer betMay 15, 2011 at 12:41 pm #1239056
You really need someone who knows their stuff with electronics, and to buy decent kit and wire it up properly. Especially with the batteries as if those go pear shaped you could end up setting a big fire! If you don’t want to get involved with the techie stuff (though from other posts on here you come across as intelligent enough to do do) there should be at least one person in your crew who can.
To get the loudest sound from the least power, you need the most sensitive speakers. Speakers are rated in decibels per watt, this number should be as big as possible.
what is the reason for doing this? I ask this because if the idea is that it will be easier to buck licensing requirements with a smaller system that won’t work – however I can see how if done correctly (particulary if you use renewable energy to power the batteries) it would make it easier for you to get permission to use land/buildings – if you do it right your image will change from the stereotype of a rave crew as “a bunch of young unemployed kids with thousands worth of sound equipment bought from drug dealing” to “some smart and eco-aware youngsters learning and using valuable skills”. And this isn’t exactly a bad thing!
(this link might help you)May 15, 2011 at 6:26 pm #1239069Anonymous
So i’ve done a lot more research over the last day or so. This has played a large part in helping me work out what everything is; Off-Grid Party Sound Systems
I haven’t bought an amp yet but plan to buy this one instead:
Indeed Tripath TA2020 Mini Cute Class T Amplifier 20WX2 | eBay UK
it runs off the same chip (TA2020 I believe), apparently (according to that instructable) it’s better built and it has a 20w RMS which is much better.
Thanks for the lead acid link, I am now thinking of using one (could wire a couple in parallel but then would have to charge in parallel to stop a massive waste of energy also I think). The purpose is to have small bbqs with a bit of a stomp but not really for image as I wasn’t really planning for it to be large enough for squatting or similar.
That instructable recommended these speakers:
B-Stock Gemini RS308 Passive DJ Speakers Pair RS 308 | eBay UK
Which are a pretty good price for the size. However the instructable is running only one off a stereo amp (but not just leaving one channel empty because this looses all the energy for that channel I think?) in mono. Not sure how they’ve done it. Also, the amp I’ve selected only outputs I think 12w RMS at 8 ohm which is what these speakers are. How much of the speaker capabilities will this be using? How would it change this if I only ran the one speaker instead of the pair?
Thanks for the help and the link 🙂May 15, 2011 at 6:44 pm #1239057
What he has done is used one channel for the woofer and another for the tweeter, having used a crossover after the mixer.
It may be worth getting the amps first and then borrowing a couple of speakers to try them out and see how loud you get…
Remember that you don’t have to use car batteries – they are heavy bulky things. taking a 12V feed from yours or your mates car / van isn’t a good idea either as if someone “helpfully” starts the engine to charge it, it will send dirty power to the amps and blow the chips in them (not very eco-friendly either!)
The sealed lead acid kind of battery found in golf buggies, cheaper e-bikes and other such items are also a possibility (but you need the right charger). Also give some thought as to how you will power the mixer and decks / CDJ’s / MP3 player (unless you are instead using a laptop).
You can also charge the laptops battery from the 12V one with the right convertor, but it does use a fair bit of current.
Don’t forget to put fuses in all the right places and use good thick cable for the amp power feeds…May 15, 2011 at 6:51 pm #1239070Anonymous
Powering the mixer is a whole different story, I want to get the amp and speaker(s) up and running first. Something like this has been recommended for the amp, what’re your thoughts?
PowerStar PS12-70 12V 70AH Sealed Lead Acid Battery 2 Year Warranty
I’m thinking to start with only one of those TA2020 amps see what that can produce.
PA speakers like those gemini use speakon connectors, what’s the deal with connecting that to the amp i’m using, is there a simple converter available?
Thanks!May 15, 2011 at 7:13 pm #1239058
That battery is mislabelled.
its 7AH rather than 70AH, this is a big difference. The amp uses about 2A when running at full power, the 7AH battery would only last 2 hours. You do not want to run these things down too much over half the AH capacity as the batteries will get knackered quickly if you do.
if you have a actual 70AH battery and use 36AH (I deliberately use the extra AH for this figure to make the maths easier) then you should get 18 hours. But a 70AH SLA is expensive and heavy. I’d go for about 20AH if you can afford it, maybe even two in parallell (this doubles the AH)
If you have friends who work in IT you might be lucky and be able to pick up old UPS batteries as companies replace them after 3-5 years – or if they work on burglar or fire alarms (which also contain them).
As for the speakon connectors, all you have to do is buy a roll of speaker cable, the connectors and then wire them up, you then connect the bare ends to the green connector.
These two places will sell you all the other bits you need like connectors, don’t buy them in Halfords or places like Maplins as you will get ripped off big time..
Rapid | Distributors of electronic components, electrical products and educational supplies
CPC | CPC – Over 100, 000 products from one of the worlds leading distributors of electronic and related products.May 15, 2011 at 8:49 pm #1239071Anonymous
I’m kind of confused, on speakerplans poeple are telling me I can get 10+ hours out of a 7Ah battery, yet you say only 2 hours?
12v system please confirm it’ll work – Speakerplans.com Forums – Page 2May 15, 2011 at 9:15 pm #1239059
it depends how much of the battery’s capacity you use. Using the full 6/7AH will knacker it quickly. Others on there are suggesting 70-80% of the capacity (to be fair I was thinking of e-bikes when I said 50% and these use way more current). but even that means you are getting only 5AH from the battery.
They also claim on speakerplans the amp uses much less current but that may be a different design without the other circuitry like protection relays, or just measuring the power draw of a chip on a breadboard circuit. 0.350A seems like way too little for 40W output!
The comments on the fleabay page claim that one chap used a power supply and got good volume at 1.5A power draw – the Chinese sell a 5A power supply to go with it (for running it from mains)
I’d be sceptical until I’d actually got the amp on a test bench with an ammeter on the power supply checking the exact current draw whilst playing your favourite tunes …May 15, 2011 at 9:32 pm #1239072Anonymous
Ok thanks 🙂 I’ve just bought the amp it’s coming from a long way though so will probably be in excess of a week before it arrives. Then I’ve got to purchase the battery/charger and speakers.. So it’s looking a few weeks off yet..May 15, 2011 at 10:13 pm #1239060
I’ll freely admit because of what I do for a living when it comes to batteries and power supplies (I’ve installed a fair few UPS units) I am very fussy about getting reliable power and thus tend to take a “worst case” approach to estimating how much power equipment draws specify a larger battery if at all possible – lives and safety depend on some of the stuff I work on, so if we spend £20 or £30 more on a bigger battery in the UPS its not a big deal. (its all installed out in the sticks where the mains can be flaky anyway!)
I do appreciate that for a group of younger folk wanting to listen to music cost may be more of an issue, but if you can afford a larger battery it won’t hurt (unless you get a short circuit, which you must be careful against!)
Some chap from up near March had a business selling batteries, UPSs and the older style e-bike (not the ones like mountain bikes but the ones the OAP’s ride) but his website is down so I’m not sure if he’s still in business. I’ll try and check next week at he had some decent ones for OK prices..May 16, 2011 at 7:10 am #1239067DaftFaderParticipant
Btw them speakers are 120W rms not 12W … the amp you said is 20W rms.
I’m not sure you’ll power them with thoes amps.
[EDIT]Alltho they are only 8 inch cones so it might work.May 16, 2011 at 1:00 pm #1239073Anonymous
Thanks a lot GL, I see where you’re coming from now. 🙂
I’ve seen people power the same speakers off a 10w rms amp so it definitely works. Whether it uses the full capactity of the speakers though is a different concern.. How do I wire the positve and negative SLA battery to a 12v connector is their a certain name for this?
Thanks 🙂May 16, 2011 at 9:36 pm #1239074Anonymous
If I only wire one speaker to one of the channels on the amp leavign the other free, will the battery last twice as long or still just the same?
Would two smaller speakers be louder than one larger one?May 16, 2011 at 10:10 pm #1239061
depending on the amps construction it probably won’t do the chip any good. you are better off using two small speakers.
BTW for the power what you need is a 2.5mm DC connector, decent quality cable good for about 2-5 amps current, a 5 amp inline fuse and spade connectors for the battery end.May 17, 2011 at 4:01 pm #1239075Anonymous
Thanks so much very useful and helpful! It’s the little things like this which makes the whole thing not work if you get them wrong! Thanks!May 17, 2011 at 4:49 pm #1239076Anonymous
What’s the difference between 4 and 2 pole speakon connectors?May 17, 2011 at 5:01 pm #1239062
4 pole are used to access two speakers in a cabinet separately for instance when using one amp channel for low range and the other for mid range/tops (having used a crossover downstream of the mixer)
a 2 pole connector is just like any standard speaker cable, but is safer to equipment and operators than other connectors (as high power audio has high voltages on it!)May 17, 2011 at 5:10 pm #1239077Anonymous
Ah got it thanks. 🙂 Is there any differences between the types of spade connectors? What’s the standard for an LSA?May 17, 2011 at 5:35 pm #1239063
the connector normally used on batteries is called a Faston. this is the company who owns the trademark but you can get these anywhere. they are very common in all sorts of electrical equipment, particularly in cars.May 21, 2011 at 7:47 pm #1239078Anonymous
Ok thanks a lot, i’ve soldered up the fuse and dc and spade connectors. Amp, Battery and Charger in the post.. Only speakers now.
So the specs for the TA2020 say a 23w RMS for 4ohm and 12w RMS for 8ohm per channel. Does this mean I can only run speakers with those impedances though? Or is it a range and 6ohm speakers would also work at around 16w RMS?May 21, 2011 at 7:49 pm #1239064
yep you will be OK provided whatever combination of speakers you use does not let impedance drop below 4 ohm.May 26, 2011 at 10:49 am #1239079Anonymous
Thanks for all the help. Here’s what they came out like. Going to be getting some different speakers at some stage though:
YouTube – 12v Sound System vibrates phone
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