Festival Music-Wagon. Much Needed Answers!

[SimonZ]

Dear DIY-Enthusiasts.

Please bear over with me as i'm a Danish Wiking only used to Rape and Plunder .

Every Year i Attented different Music Festivals. Last year i build my own music-pushwagon but this year i want to go bigger and better.

2010 setup:


Specs
- Cheap 4 x 100Wrms drivers @ 4 Ohm
- Cheap 4 x 45W headunit (guess it delivers 10Wrms)
- 2 x 12V Deep Cycle Batteries @ 75 Ah each.

This was a great system because of it's low power usage at 40-60W @90% volume.
This was no Quality-system but it sounded OK when kept at >90% volume.
Also I had soldered 50 Blue LED Diodes to make it look fancy .


This Year.
I have spend obscene amount of time surfing the forums trying to figure out how to build the perfect setup. But i have some serious questions.

Questions.

Remember: This Setup is ment to be used in open fields filled with Tents and drunk people.
I dont want to recharge at any point over a timeframe of 6 days and therefore this setup is build to get the most attention for the least amount of powerusage and buildprice.

Q1 - The travel-distance of soundwaves
Where should my focus be when I want the system to be heard over great distances?

Last year the system played loud enough when standing right next to the system but you almost could'nt hear the system when outside the camp-area.

I know that low Freq. wavelengths travel further than high Freq. wavelengths but SubWoofers also consume more Watt, so...

Q1A What gives me the greatest travel-distance for the most Watts? Midtone vs Bass?

Q1B Does higher DB equal longer travel-distance for sound?

Q1C If Speaker A uses 20Wrms to produce 100 DB and Speaker B uses 40Wrms to produce 100 DB, would the two speakers be heard over the same distance?

Q1D Should i focus on Directional Speakers as the soundwaves going upwards would be a waste of energy as there is no Roof in the field?

Q2 Watt and Wrms?

I know that 1W=1W but if an Amp produces 2 x 25 Wrms @4 Ohm - 12V with 80%Efficiency that would require at least 60W of Input to the Amp, but why does this TA2020 Based Amp Power suply output 11-14 volts ADJ @ 3.5 Amps which only gives us between 38,5W and 49W ?

Example from ArjanHelders Board which btw looks nice!

Q3 Loudest Speakers for the Money
At first i used a lot of time searching for the perfect amplifier that delivers the most Wrms for the money but then i realised that i need to play loud music and since a Speaker consume the double energy just to play 3Db louder i thought.. Why waste Watt on doubling Speaker Output when i can Double the amount of Speakers?

Price put aside.. What would play the loudest?

2 x Speaker with Sensitivity of 90Db @ 1W Versus 1 x Speaker with Sensitivity of 90Db @ 2W ?

Q4 - 4ohm Vs 8 Ohm

Lets say i have an Amplifier that runs smooth in both 4Ohm and 8Ohm.
In this case the Logic solution is to choose 4Ohm as i would get more Watt Output.

Q4A but i have read about some Amplifiers that have higher Effeciency at 8 Ohm?

Q4B I have also read about some Speakers that have Different Sensitivity (SPL?) when running in 4 or 8 Ohm?.

Off course i dont always know the SPL lvls of a speaker in both 4 and 8 Ohm..

Q4C But i would rather run in 8 Ohm if the SPL is 4 Db higher than running in 4 Ohm which would give me 1 Db more than running in 4 Ohm with double Watt..right?

My plan for 2011.

This year i want to fix some of the problems we had last year but mosf of all i want to build a setup that offers the most attention for the least W usage and buildprice. I hope you will help me out :-)

Last year Budget: 500 USD

This years Budget: 1.700 USD.
- 1.000 USD for Solar Panels & Batteries
- 200 USD for Lights, Wagon and Head Unit(Dj-Mixer).
- 500 USD for Amp+Speakers.

So far i am going to Buy the 4*100 watt @ 4ohm, TK2050 Tripath Chip D-class from Sure Electronics.

I plan to set 2 Mid-range Speakers on two Channels and then two or One Bass unit on one Channel - leaving one channel left unused.

Would this be fine, or should i try to use all channels?

I have never tried using Filters.. Would a two-way filter have any performance improvement at all in this setup?

But most of all.. Where do i find the cheapest speakers with the highest Sensitivity?

Btw it would be great to focus on dealers in Europe since we have some extreme Taxes when buying from outside Europe.

I hope i didnt scare you all off with all the Questions - i tried to set it up logically but there is just so much to ask you guys about

Kind Regards Simon.

[Pano]

Hi Simon, I will try to answer your questions - in no particular order.
That's a nice looking rig.

Power: Running on 12 volts will only get you so much power, not much - even if you use 2 ohm speakers. It Ohm's law. To get more audio power out of a 12V battery, you have to use a DC-DC up converter. That's what the big car amps do, it's built in. So you either have to do that, or use higher voltage batteries.

100dB will be heard the same as any other 100dB at a given point in space. Does not matter how much power it took to get there. But some speakers are more directional than others, so they can concentrate the same energy over a smaller area.

That leads us to:

Throw: A box like yours is big for a portable, but small for an outdoor PA. The bass and some of the mids will wrap right around the box giving you near 360 degrees of coverage. That's good if you want to blast in all directions, bad if you want it to go far. So what you do is contain the angle of radiation. Horns are great for this, you can get a lot of efficiency and a narrow throw. But horns are big, especially bass.

You need to determine how big you can stand this thing to be. The bigger it is, the more efficient it's gong to be (unlike a car). The trade off is size vs power. Outside, you need lots of efficiency and lots of power to make it loud. As the sound spreads out in all directions and gets lost because there are no walls to contain it and bounce it back to you. You found this last summer.

I would say to start, determine the largest size you can live with or can transport. The design will go from there. You may even be able to build some sort of folding bass bin that you can assemble on site.

I think pro audio drivers are going to be your friend so that you can get as many dB as possible per watt. Eminence and Selenium are great value for money, at least here in North America.

I hope that helped. Many others here will have good ideas, too.
..

[SimonZ]

Thanks for the Reply Pano!
I really thought i had posted earlier - but it have been a great help.

Update:
Power: I am planning on running 2 x 12V batteries in series so i have around 24V - I am going to buy a 80W solar Panel (guess it delivers 60w @ Full sunlight)

Amp: I have received the 4x100W amplifier - it uses 10W idle @ 25V and is very effective.

Drivers: I have searched far and wide for High SPL drivers in Europe (because of Tax laws) that is cost-effective for this project and i have Fell in love with the Brand Visaton in Germany!

Subwoofer: 1 x Visaton - W 300 S 4 OHM
Mid-high range: 4 x Visaton BG 20 8 OHM

I first thought of buying 2 x BG 20 for midrange and then buy the Visaton Tweeter - HTH 8.7 8 OHM because of the High SPL @ 106dB/1W but i was unsure if i need it and how to cope with the Difference in SPL i think i am going with the BG 20 as they also have a tweeter dome.

I have the sub in my possession, but wanted to ask you guys first:
Q: Should i go with 2/4 BG20 and/or the Tweeter Horn?

Sure electronics said i cant bridge the amplifier, so i have to live with that, but as i only have 1 subwoofer i wanted it to play both left and right so i hooked it up as seen in FIG 1, but sure electronics said i shouldnt hook it up like that, Is this bridging? i thought that fig 2. was bridging and fig 1. just got both signals?


Also i tried to make a quick model in 3D. But as said i dot know wether to buy the 4 bg20 drivers yet.

[picowallspeaker]

<yeah>
make it foldable

[SimonZ]

Good idea, making it foldable but isnt it a problem if the enclosure isnt 100% airtight?

[kipman725]

If the amplifier is already bridged internaly (quite probable) then you are giving the sub 0.5*CH1+0.5CH2. IF the amplifier isn't already bridged then you give the speaker just the channel 2 output as the channel1 and channel2 - are at both the same fixed potential.

The visaton WS series are very good drivers for the money I have been impresed with the WS20

[Saturnus]

To comment on your cabling.

It doesn't matter if you connect it like FIG 1 or FIG 2 you will destroy the amp immediately if you try either.

In any case you should probably have a look in the Boominator thread. Like Pano said below, sound wraps around the speaker no matter what you do depending on frequency, so to get the most out of you speakers you just exploit that and built a bipolar speaker like the Boominator instead.

Your setup isn't much different anyways, just much more inefficient which means you waste a ton of cash on too large solar panels and batteries.

A Boominator can be built for about USD600-800 including everything, also solar panels.

[SimonZ]

Hey Kipman! Thanks for the reply, yeah it makes sense, but still, fig1 and fig2 is bad for the amplifier but surely it wont kill the amplifier emediatly by running in fig1 (as i have tested without any loss whatsoever) .

@Saturnus Thx for reply! i have read almost your whole thread (it's good!) and your Boominator is really a nice boombox, but we have different approaches to pre-festival music as i would like to have a Party-starter with a dj-mixer, lightning and other gadgets like 230V power(+usb) outtake to charge cellphones.

Off course the sound will wrap around our speaker, but there is a significant difference between bipolar and monopolar, and for directing most sound for the leastest power in one direction we are sticking to a monopolar setup - if we were to drive around with the wagon all day we would go with bipolar but we are too lazy and just want some great parties at our camp

Well regarding the efficiency, your speakers are more efficient than ours, but you must not forget we have the possibility of building a much larger enclosure to increase SPL dramaticly - but when that's said, i am still unsure wether to build a tapped horn ~/ LAB horn or just a ported enclosure for the sub but the 4x BG20 is going to get seperate 30-50L Sealed enclosures.

Well anyway, we knew from the beginning our focus isn't the Most dB/W but the most fun/W so we were on the lookout for efficient speakers for a reasonable price but still with a large X-max so we can waste some power on watching this thing move some air , and Visaton is perfect for this setup, and we know we need more power by doing this and so be it 100W solar panel on the way.

[Saturnus]

Try simulating a horn design in 4pi (outdoor use) and you'll see that you need a horn that is at least twice the length and with at least 4 times the horn mouth than you would indoors. Horns, and in particular tapped horns are very impractical for ourdoors use unless you have so large a stack of them so they effectively make a wall of their own.