12v system please confirm it'll work

I've already bought the amp, it'ss a TA2020 based one (20w RMS) , i'm seriously considering one or two of these:
http://www.djkit.com/gemini/gemini-rs-308.html

I want to run for a good few hours. What are your thoughts?

 

BrightonJake wrote: And your amp is 20 W..... buy 2 and I recon you might get 1.8 mins playtime...:@/

What are you talking about? A TA2020 amp on a 7Ah battery will lasts over 30 hours with a set of 8 ohms speaker.

The problem with those speaker is that they don't list sensitivity which is most important spec at all for a 12V system.

Edited by Saturnus - 15 May 2011 at 8:57pm

BrightonJake wrote: I would say the clue is in the description: Gemini RS-308 480W Passive Speaker DJK05865 Gemini RS-308 8" Passive Loudspeaker - 2-way high power passive speaker system - 480W peak, 120W RMS - 8" woofer with 1.5" voice coil  - Compression driver with 1" coil - Linear frequenc...[ http://www.djkit.com/gemini/gemini-rs-308.#readmore - read more ] And your amp is 20 W..... buy 2 and I recon you might get 1.8 mins playtime...:@/

Not entirely sure what maths you're using mate! 

Rellizate, the battery you linked to will give a clear 10 hours + by my reckoning. The average power output will be roughly 1/6 the RMS output. As combined RMS output is 40wrms, the average power is 7w. This is with running pink noise however - music signals use around half the power - so thats down to around 4w.  Add onto this a worst case scenario of 1w idle power and you have 5w usage.

The battery you linked to has 6Ah usable power, which gives 72Wh (12*6). At 5w power then this translates to 14.4 hours. In reality this can easily be double this though 

if you want more noise, an easy solution is to run a tk2050 based amplifier off two 7Ah batteries in series. This will give you 6db more noise, with around half the runtime

Edited by infrasound - 15 May 2011 at 9:13pm

 

infrasound wrote: if you want more noise, an easy solution is to run a tk2050 based amplifier off two 7Ah batteries in series. This will give you 6db more noise, with around half the runtime

Far less actually. 6dB is 4 times the power so it should be a quarter of the running time but a TK2050 also has far more quiscent current so at least 5 times less battery time.

The strange thing is that a TK2050 amp on 24V actually uses more power in idle than a TA2020 amp does at full power.

rich_gale wrote: BrightonJake wrote: I agree mostly with Blaize110, except for the bit about car batteries. I am not sure what you mean by being careful how you discharge them?!! The whole point is that you are dictating the discharge by what you connect to them. 1) a car (mega big harsh gulps of juice) or 2) Audio amplification (moderate, continuous, lengthy discharge). That is why I suggest you certainly dont waste good money on the wrong battery (a car battery)!.....am I missing something? echoed.  cyclic 12v sla.  not a car battery

If you're going to go out and _buy_ one - then yes, definitley get a cyclic type rather than car battery.

But I've used a 45Ah car battery (which I got given for nothing by a flatmate who was leaving the country) to run a cheapy 350W inverter with a bit of mains-powered gear - and it worked perfectly well for run-times of 5-6 hours. Although a cyclic type will get you better run-times, and will most likely last longer (long-term).

The thing about "leisure" batteries (which are the optimal _type_ .... is that they start at 85Ah or so - weighing in at well over 20Kg .... a bit overkill for a smallish system - unless you want to play for the whole weekend etc.

I still say the Lithium packs are a btter choice if you care about the weight though .....

If - OTOH - you want to run a Tripath 2050 amplifier (higher power) - needing 24V or so - then go the SLA route.

BrightonJake wrote: I would be supprised to get 6 AH out of a 7 AH battery.....