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12V.. how much is possible?

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nilspixel View Drop Down
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    Posted: 02 March 2021 at 12:15pm
hi all!

i came across this topic from 2019 and was wondering, what has happened to the project. i'd love to build something very similar... https://forum.speakerplans.com/12-v-simple-system-for-reggae_topic103222_page1.html

for now i don't really have any ideas on how to start. the only thing i know is that i want to build a mini stack on 12V and put it to use outdoors. it will be carried on a bicycle trailer with a maximum capacity of 1608 x 610 mm and 136kg. so plenty of space to fill...

i don't want to become an electrical engineer and keep things as simple as possible. Car Preamps might work for that?

A Tham15 and a Mid Top would be great... but i don't know too much about what is possible and what not... I need a kickstart from someone who has some experience :)

thanks and all the best
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studio45 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 02 March 2021 at 2:55pm
Much is possible! MUCH ;)

A Tham15 and a midtop is a pretty good place to start. But, you might want to look at something a little smaller if you're planning to tow it around a lot, and/or use car batteries (lead acid). A Tham15, 10" midtop, 75Ah battery and amps should *just about* be under 136kg. 

However, I know from experience that towing anything over 75kg is very difficult on hills, and pretty hairy in terms of stopping/ going round corners - good brakes and wide tyres are a MUST. So maybe a Tham12 and an 8" midtop might be more manageable - that was the first iteration of the Commotion rig and it worked very well. 

The current standard recommendation is to buy Pioneer GM-D series amps. They are powerful, efficient, light weight and very affordable. They have a built in crossover to separate the bass from the mid tops, and can run direct from a phone aux output or a Bluetooth adapter. The only minor downsides are - they can only run from 12v batteries not any higher voltage, and they have no fundamental highpass filter to cut off useless sub-20Hz frequencies that waste battery power. 

You might want some kind of mixer to go on the front end - again Pioneer have some nice pieces that run from a 5v power supply, which is easy to get from a 12v battery and car USB adapter. 

There are vastly lighter alternatives the lead-acid batteries of course - lithium being the main one. You have to think about voltages a bit carefully as lithium-ion cells are 3.7 volt nominal whereas lead-acid are 2.0 volt nominal. So if you have a Pioneer or other car amp that's expecting a max voltage input of 14.5v (with engine running) you can't really use Li-Ion cells to make a battery that can be drained fully while not going over-voltage for the amp at full charge - three in series is 11.1v, four in series is 14.8v so you can't hit that "12v" sweet spot. Lithium iron phosphate (LiFePO4) cells at 3.2v nominal are a better match - a set of 4 in series give a 12.8v battery that works well with car audio gear. 

Don't expect to save any physical space with lithium batteries, they normally end up being about the same size as lead-acid - but 1/3 the weight!
Studio45 - Box Builder Commotion Soundsystem -Mobile PA
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nilspixel Quote  Post ReplyReply Direct Link To This Post Posted: 02 March 2021 at 6:09pm
hey studio45, thanks for your opinion. i'm glad someone responded that quickly :)

i found this site with suiting plans for a THAM12.
http://https://www.martinsson.cc/blog/index.php?m=03&y=12&entry=entry120315-210219
A Beyma 12LX60 driver is fine for my project? what do i have to watch out for when buying drivers for 12V usage?

any recommendations for a 8" midtop? :)

New Plan:
  • THAM 12 with Beyma 12LX60
  • a 8" Midtop
  • Pioneer GM-D series amp (which one?)
  • additional mixer, have to look them up...
  • don't know about my power supplies yet... but got an idea ;)

cheers

EDIT: As I'm not planing to do any DJing outdoors a Mixer is not a necessity... AUX is entirely sufficient :)


Edited by nilspixel - 02 March 2021 at 6:38pm
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slaz View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote slaz Quote  Post ReplyReply Direct Link To This Post Posted: 03 March 2021 at 2:38pm
As usual, I'd endorse pretty much everything studio45 said.

Couple of things to add ...

Actually this should probably be a "sticky" for this section.

Pretty much all car amplifiers rate their output with a supply voltage of 14.4V or close to that.
When using them on a off-grid situation (i.e. standalone battery power, no charge from a car alternator) - and assume a median discharge voltage of - say 12.5V - the real world power o/p will be about 3/4 of their rating .... e.g. a 100W amp becomes actually about 75W. Near the end of discharge cycle - say 11.5V - that goes down to about 64W. Not an enormous difference in SPL (1 or 2 db), but the amp _will_ clip earlier/easier. Also (esp with lead-acid) the voltage will be more prone to sag under heavy load - which can cause clipping/distortion .... needs to be borne in mind when you set your levels.

If you want a baby mixer to just have single line in (e.g. laptop, tablet, phone etc.) and a decent mic input ..... take a look at the Behringer 302USB. It has good o/p level (can drive a proper amp if needed), has a good mic pre-amp with good overload margin (1/4" jack/XLR combo connector) and can be powered all day from a USB phone power bank thingy. Having its own power supply neatly side-steps any possible ground-loop hassles.

Mine has performed like a champ with a MC and also when someone gets up and wants to have a little sing-along :-)





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Post Options Post Options   Thanks (1) Thanks(1)   Quote slaz Quote  Post ReplyReply Direct Link To This Post Posted: 03 March 2021 at 2:51pm
Originally posted by nilspixel nilspixel wrote:


any recommendations for a 8" midtop? :)


By repute, a EV SX80 (8" mid/bass + comp driver) will do a good job. A good deal lighter than most 8+1 cabs made from plywood (its a plastic moulded enclosure ... but a good one).
Should play well down to 100Hz or so.


REMEMBER....POLITICIANS AND DIAPERS SHOULD BE CHANGED OFTEN AND FOR THE SAME REASON
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nilspixel Quote  Post ReplyReply Direct Link To This Post Posted: 03 March 2021 at 3:48pm
Originally posted by slaz slaz wrote:

Mine has performed like a champ with a MC and also when someone gets up and wants to have a little sing-along :-)


you got me with this one! will get one! :)

Originally posted by slaz slaz wrote:

Originally posted by nilspixel nilspixel wrote:

any recommendations for a 8" midtop? :)


By repute, a EV SX80 (8" mid/bass + comp driver) will do a good job. A good deal lighter than most 8+1 cabs made from plywood (its a plastic moulded enclosure ... but a good one).
Should play well down to 100Hz or so.



thanks for your recommendation :) but to match the look i'd want to make it from plywood just like the THAM12...


Edited by nilspixel - 03 March 2021 at 3:52pm
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Post Options Post Options   Thanks (1) Thanks(1)   Quote APW Quote  Post ReplyReply Direct Link To This Post Posted: 03 March 2021 at 4:10pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nilspixel Quote  Post ReplyReply Direct Link To This Post Posted: 03 March 2021 at 4:14pm
Alrigth, so things come together a little more. But still some stuff left i don't understand...

Say i want a Pioneer GM-D8604, Class D 4x 120W @ 4 Ohm. It has 4 channels which can be used to power 4 speakers?Confused

https://ibb.co/QCw3WBr -

When every channel has 120W.. do i have to look out for the drivers not to be above 120W? Am I restricted to 4 Ohm?

thanks again :)

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Post Options Post Options   Thanks (0) Thanks(0)   Quote nilspixel Quote  Post ReplyReply Direct Link To This Post Posted: 03 March 2021 at 6:27pm
Originally posted by nilspixel nilspixel wrote:


Say i want a Pioneer GM-D8604, Class D 4x 120W @ 4 Ohm. It has 4 channels which can be used to power 4 speakers?Confused




Ok i just answered this by myself.

The amp mentioned above is able to be bridged to use it as a 2 channel machine!! nice. got that now... the TwoWay speaker linked by APW has all the electronics inside and uses one input for both drivers...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nilspixel Quote  Post ReplyReply Direct Link To This Post Posted: 03 March 2021 at 7:50pm
As the data from the used drivers in the provided Two Way Cabinet seemed a bit too much i found this one:
https://celestion.com/blog/build-this-compact-10-two-way-pa-speaker-design/

What do you mean?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nilspixel Quote  Post ReplyReply Direct Link To This Post Posted: 03 March 2021 at 10:35pm
Okay guys, i just ordered the amplifier (Pioneer GM-D8704) to have a start on this project. Also some sheets of 15mm birch plywood is on its way to my workshop.
For now the project consists of the following:
  • Pioneer GM-D8704
  • Gives me 2*300W RMS with 4 Ohms
  • THAM12 with 'the box 12-280/8-W' https://www.thomann.de/de/the_box_speaker_12_280_8_w.htm
  • RMS 280W 8 Ω (http://im.static-thomann.de/pics//atg/atg//specs/283965_c_283965_sheet_v2_en_online.pdf)
  • A Celestion Two Way Spekerunit as seen here: https://celestion.com/blog/build-this-compact-10-two-way-pa-speaker-design/
  • Format: 2-way system Drivers: TF1020, CDX1-1445 (H1-7050) 
  • Sensitivity: 97.0dB (2.83V/1m)Input Impedance: 8ohms (nominal), 6.5 ohms (minimum) 
  • System Rated Power: 250W (EIA), 1000W (peak)
Any more suggestions so far? Happy to hear them 😊



Edited by nilspixel - 03 March 2021 at 10:40pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote APW Quote  Post ReplyReply Direct Link To This Post Posted: 04 March 2021 at 9:41am

When you say the drivers are too much what exactly do you mean... Cost?

If so you can use cheaper drivers, the Fane Sovereign 8-225 or Fane Sovereign Pro 8-225 both work in the 8" Eighteen Sound cab and the compression driver can be substituted by the Eighteen Sound XD125, the CDX1-1445 used in the Celestion cabinet or something like a Beyma CD10Fe… The Eighteen Sound horn used in that cabinet is fairly cheap!!



Edited by APW - 04 March 2021 at 9:42am
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