DIY Ghetto soundsystem!

[awgrant]

Hi folks,

Im in need of a little help with an interesting project that should make some of you laugh and some of you cry….

I am attempting to put together a whole bunch of very cheap speakers i find from Craigslist to create a suicide rig for Burning Man. Something in the vein of

The purpose is so i can DJ a techno set at my own camp in the middle of the desert.

The Equipment will take a beating with high daytime temperatures (100’s) and low evening temperatures possibly approaching freezing and also very dusty conditions!!!

So far the rig consists of

2x Kenwood KL-A900 Speakers with after market DHD NTX-6615 (800W Max @ 8ohm) installed.

2x JVC SP-MXKC45 (200W Max @ 6ohm)

Philips FWB-R7 (100W @6ohm)

Philips SW3900/17S Subwoofer (unknown watts @ 4ohm)

($37 Craigslist )

I plan to make it a 2 way stereo stack, split into Low and Mid/Top.

I plan to use the Subs in the Kenwoods only, I will remove the rather nice horn loaded tweeters (Trio-Kenwood T14-079-05) to use as tops, and have the other drivers installed but not wired and the hole blocked up.

The Philips/JVC speakers and Philips SW will be used as stereo mid/tops and the Horn loaded tweeters removed from the Kenwood’s and sat on top.

The Low will be powered by a Behringer A500 amp bridged into 600watt @ 8ohm Mono
The Mid/tops will be powered by a Behringer A500 amp 2 x 300watt @ 4ohm stereo
($150 approx ebay each)

I am considering using a stereo 2-way Behringer Super X Pro CX2310 active crossover, and as yet an unknown EQ.
($100 approx)

I am hoping you guys can point out anything i may have missed before i go and buy the amps etc.

Im am looking to achieve

a. the best sound,
b. the cheapest price,
c. the lowest power consumption. (running from a 2000w max Honda generator)

Also, I am no electrician so my understanding of ohms is limited, maybe someone could highlight the pitfalls of using differently rated speakers together on the same amp? Does the resistance balance out over all the drivers, i.e. does 2 x 6ohm and 2 x 8ohm create a 7 ohm resistance? And if so would the above amp kicking out 2 x300watt @ 4ohm be sufficient to power them?

I would love to hear what you all think of this slightly mad endeavor? Just remember i have to take it to BM with the intention that nothing will be in a fit condition to use again, hence a suicide rig! Thanks for your time.

Ali

 

[conanski]

Im am looking to achieve
a. the best sound,

LOL.. Good one.

b. the cheapest price,

Probably nailed it.

c. the lowest power consumption. (running from a 2000w max Honda generator)

Probably failed miserably on that one though, a single proper PA speaker would produce more sound with a fraction of the amplifier power than all this stuff.

Also, I am no electrician so my understanding of ohms is limited, maybe someone could highlight the pitfalls of using differently rated speakers together on the same amp? Does the resistance balance out over all the drivers, i.e. does 2 x 6ohm and 2 x 8ohm create a 7 ohm resistance?

Have a look at this link and plug in the impedances of the speakers you have. Note that putting a jumper from 1 speaker to the next is considered a parallel wiring. http://www.speakerimpedance.co.uk/?act=two_parallel&page=calculator

 

[awgrant]

Thanks Conanski, i suppose you fall into the cry category then is it?

Hey I understand that a super nice powered Mackie or an all out Void Incubus rig would sh*t all over what i got of course it would, but its supposed to be burnt at the end of the festival..... there is no way im burning a nice set of speakers! The amps will most lickly be fried either from the heat or after from the akaline dust!

SOOO the alternative is to get the 'best sound' for as little money as possible, any help would be much appreciated...... its a fun project not ment to be taken seriously.

And you would be surprised at how good a bunch of cheap band pass speakers can sound when given a clean signal.

Thanks for the reply anyways.

 

[awgrant]

Have a look at this link and plug in the impedances of the speakers you have. Note that putting a jumper from 1 speaker to the next is considered a parallel wiring. Speaker Impedance

Great link, thanks

So some quick calculations for one top/mid channel would be as follows;

JVC = 200W Max @ 6ohm
Philips = 100W @ 6ohm
Kenwood horn = Unknown watts @ 8ohm

with a 300 watt amplification this gives the following results;

Parallel connection,

Total Impedance = 2.18181818182 Ω
Speaker A Power = 109.090909091 Watts
Speaker B Power = 109.090909091 Watts
Speaker C Power = 81.8181818182 Watts

Series connection,

Total Impedance = 20 Ω
Speaker A Power = 90 Watts
Speaker B Power = 90 Watts
Speaker C Power = 120 Watts

Looks like the total impedance of the 'in series' connection method would be too high for the 300 W 8ohm amp, am i wrong??

And the parallel connection calculations show suitable watts but the impedance is 2ohm's, who would this effect the speakers/amp?

 

[picowallspeaker]

I don't understand the "Why ? "
Simply, why you would want to go somewhere-and that's a load !-and use it and incinerate it ?!
Meaning that the transportation will burn gasoline and produce TONS of Co2



Ok, you are a villain living at the desert border and you take a walk and deposit your junk, No ! You live abroad and make plans to go to a certain place playing certain music with...whaaat ? Lol
That makes sense.

So a little sense of history: Give ghettoblasters a life ! I've never heard of a ghetto-blaster powered with a generator.
But...I see that low voltage goes with low Z loudspeakers
And the headroom is defined by ...deciBels

 

[MisterTwister]

you can wire two speakers in parallel and third one in series with them.

 

[awgrant]

I don't understand the "Why ? "
Simply, why you would want to go somewhere-and that's a load !-and use it and incinerate it ?!

Haha, yeah i get what your saying, why.... why the hell not? Go to a festival party, celebrate and express oneself. I'm an artist and i intend to use everything at my limited disposal to express the music i love to the people i love.

Meaning that the transportation will burn gasoline and produce TONS of Co2

Burning man is all about burning visit this link for more info, Burning Man :: Welcome Home

You live abroad and make plans to go to a certain place playing certain music with...whaaat ? Lol
That makes sense.

I thinkit makes sense too, thanks!

So a little sense of history: Give ghettoblasters a life ! I've never heard of a ghetto-blaster powered with a generator.
But...I see that low voltage goes with low Z loudspeakers
And the headroom is defined by ...deciBels

No Ghetto blasters here my friend, these are the finest 90's Jap imports money cant buy, LOL! Heck its in the desert, there is no power apart from what you create yourself, hence the generator.

 

[awgrant]

you can wire two speakers in parallel and third one in series with them.

OH your good!

Ok now i got to figure the maths out...

Speaker A 6ohm
Speaker B 6ohm
Amplifier 300 watts

Speakers is Parallel
Total Impedance = 3 Ω
Speaker A Power = 150 Watts
Speaker B Power = 150 Watts

So to calculate speaker C, im a little confused?
Do i use the combined watts to calculate ie. 300w or is it halved, ie 150watts?

Result A using 300w;
Total Impedance = 11 Ω
Speaker A/B (parallel) Power = 81.8181818182 Watts
Speaker C (in series with the parallel circuit above) Power = 218.181818182 Watts

Speaker C gets a heck of a lot of watts

Result B using 150w
Total Impedance = 11 Ω
Speaker A/B (parallel) Power = 40.9090909091 Watts
Speaker C (in series with the parallel circuit above) Power = 109.090909091 Watts

Speakers A/B dont get many watts

Hum... have i done this correctly, help?

 

[picowallspeaker]

I was saying Lol from a technical POV
Now some hints
The two big aluminum woofers & enclosures ( leave the back opened so you can insert the mid-tw unity for ease of transportation ) are the sub units.
I guess they could work ( give appreciable sound in their pass-band range ) till 500 Hz...but who knows, and it depends upon the choice of the associated mid-woofer driver, which might not be one of your list.
This unknown driver ( yes : you have to dismantle all your speakers with hammers and screwdrivers and bring the drivers naked ) should tame the beast of the sub, so no 20 watters allowed.

the mono-bi-multiamplifying of the whole rig and the Low Tension supply is
another practical "mountain to climb".

 

[awgrant]

Thanks Pico, not 100% sure if i understand you but; here goes. The aluminium 17inch woofers from some bad car install (i bought them like that) will run in mono together in parallel, all the other drivers in those speaker boxes will be disconnected.

So the amp which runs at 600watt @ 8ohm output, doing the maths now looks like it will be slightly under powered.

Total Impedance = 4 Ω
Speaker A Power = 300 Watts
Speaker B Power = 300 Watts

The mid tops all have their own passive crossovers, so all im doing with the active cross over is removing the lowest frequencies allowing (hopefully) lower distortion/higher db's.

What did you mean about leaving the back open on the speakers, that doesn't make much sense to me, they have twin ports already?! Can you explain, thanks?

Also i think you may misunderstand about the voltages, 120v is standard US mains voltage which will be the same output of the generator/transformer so it will run in the same way as a home HIFI system.

Thanks for the comments, really appreciate hashing this out with you guys

 

[picowallspeaker]

Hi,
you should refer to what a standard PA is made of:
for techno music so big punch when required..as for any music :

Self powered or passive subwoofer - 12 or 15" or higher Sd
The sub may have an insert on the top to hold the
Satellite - Again -self powered and filtered, Eq'ed or passive. 6 1/2 " to 10"
or array ( for better power distribution, I guess ) of smaller 4-5" ( that's what the 16Ω versions are made for )
Equalization will depend on the particular setting in ambient.
The tweeter is to match with the request of power and directivity.
Usually the horn+driver combo requires a filter with dual-slope to find the correct emission

 

[awgrant]

These are the speakers i used to mess around with;

Strangewayz/Daylite Robbery link UK UKtek 2007

My old basement Manchester

And my good friends Neuron Pro Audio

An externally hosted image should be here but it was not working when we last tested it.

The issue isn't knowing how PA systems work, its how i need to get MY PA system to work!

What im trying to ask the community here is, what is the best way to get a big sound in a middle of a desert with as little money as possible, any suggestions would be really appreciated

 

[picowallspeaker]

Yes, you should remake your old Manchester rig.
( given the fact that the units will be powered rightly) With the new woofers
the scoop style cab might be...well, I told you you could leave the back off:
Why ?
And what: what about changing woofers in a given enclosure ?
What enclosure ?
Which woofer ? Usually, DVC are a bad start just because of the DVC !
Thay might be useful for repurposing X4channel amp units- which are capable of driving 4 Ω loads.
BTL needs a double safety load

So, your old configuration with a twist.
What about considering the tweeter units in the Kenwood cab ?
As for now, IF connected with the crossover they should work all together.
So, make a treble unit with the tweeters and crossover in a box ( open ! )-
That would make @50 W unit.
I know it's hard to decipher a crossover schematic...
The (plastic !) drivers might be placed one at the top...oh well, You should define the "sound balance" of the thing, that's why a minimum knowledge
of electrical and electro-acoustic devices is beneficial

Ps. the "rave system" is horrorly nice !

 

[awgrant]

Ok so maybe we are getting somewhere...

Im going to keep the existing enclosures for the Kenwoods... i like the aesthetic and being in the US and not back home i don't have the resources to make other enclosures.

Im still unsure why you suggest an open design, would this be similar to guitar bass cabs pre 1970? From what i understand they arn't so good at producing bass??? Could you explain?

I understand that Dual Voice Coils have some disadvantages but its what i got so im going to try and use them.

But i think i will need to find a better suited amp for bass than first specified, what do you think to a 1000w at 4 ohm amp? If so any suggestions on the cheapest (haha)

What about considering the tweeter units in the Kenwood cab ?

Yeah your right this is what i first thought and have them in free space on top, should be fine only problem is the passive crossover from the Kenwoods is large with a limiter circuit included, will have to look into a solution for this!?

But yes the aim was to create something similar to my Manchester rig, but this time out of dodgy HiFi gear!

Still the problem to be solved is how to wire up the different mid/top speakers and to confirm what would be a safe amperage? Any suggestions?

Ps. the "rave system" is horrorly nice !

Why thankyou .... had great fun with this!

 

[conanski]

Ok now i got to figure the maths out...

Speaker A 6ohm
Speaker B 6ohm
Amplifier 300 watts

Speakers is Parallel
Total Impedance = 3 Ω
Speaker A Power = 150 Watts
Speaker B Power = 150 Watts

So to calculate speaker C, im a little confused?
Do i use the combined watts to calculate ie. 300w or is it halved, ie 150watts?

OK here are several point you need to know to understand how this works.
Most amplifiers have a minimum rated load impedance that you cannot go below, but it's OK to go above it.In your case that minimum is 4ohms.

When you wire multiple speakers together you will get a total impedance from whatever series/parallel configuration you use, and that is the number you are calculating with the link I gave you.

That number is the impedance you are presenting to the amplifier, if it's 4ohms the amp will produce it's 4ohm rated power, if it's 8ohms it will produce it's 8ohm rated power, if it's 6ohms it will produce something about 1/2 way between the 4 and 8 ohm ratings.

The higher the speaker impedance the less power the amp produces.

If all speakers have the same impedance and are wired in a balanced series parallel config( even numbers of drivers), then all speakers will share the amps output power evenly. That means all speakers must also be capable of handling that amount of power.

If you put a 6ohm speaker in parallel with an 8ohm speaker the 6ohm driver will get 2/3 of the amplifier power.

 

[awgrant]

Great work Conanski, thanks.

So what have we learnt so far then, erm......

1. I need a bass amp that is rated 1600W max @ 8ohm bridged to power the Kenwood/after market subs.

2. If i wire up the the 8ohm (200W max) JVC speaker in parallel with the 8ohm horn tweeter (unknown watts) and connect to this in series the Philips (100W max) @6ohm speaker with an amp that's rated at 300w per channel at 8ohm's then the power rating would be close to this;

Total Impedance = 9.42857142857 Ω
Speaker A (Philips) = 62.3376623377 Watts
Speaker B (horn tweeter) = 46.7532467532 Watts
Speaker C (JVC) = 190.909090909 Watts

At first glance the Watts are within usable tolerance to the specified max watts on each speaker, and the Impedance of the circuit is only slightly higher than the amp rating.

So an amp that produces say 400W per channel @ 8ohm would be sufficient to power this circuit? Is this correct can anyone confirm my calculations?


3. It looks like the 4ohm Philips SW will be a pain to hook up, a combination of low resistance and small power handling rules it out unless i find another amp solely for it, which is unlikely!!

Any thoughts any comments???

 

[awgrant]

Any recommendations on an 2 channel 400W RMS @8ohm amp? Either ebay second hand, or maybe someone here has one for sale?

 

[picowallspeaker]

Ok so maybe we are getting somewhere...

Nowhere...but
as we're in a desert

If...
I suggest you to look at the (ex) Kenwood's.
By now, you were using their existing crossover (s)
As you were confident that the load 4+4=8 Ω would substitute the old woofer.
And also that the cabinet...
But that's another matter and let's keep on with the electrical side, which at one point,at the transducer, it transforms into air pressure variations (sound)
Ok, the crossover: the new woofer asks for more power than the old one; what is the gauge of the inductor that performs the first lowpass ?
And looking at the midrange... what type is it ?
You could ( should) take all the drivers you have and examine them.
What about the horn tweeter ?
Are you the kind of man that knows that the tweeter needs at least a capacitor for filtering out the bass content ? Or you are the kind of elaborated mind that wants a correct slope, as the other ways should.

The JVC 200 W ? Pleeeeease! If so, I want to see the back! The magnet, I mean...

These things all together could hardly support 100 W non continuosly

So I want to know this crossover thing and test the big power woofers
As well as the treble and the mids

 

[picowallspeaker]

Usually you don't need to do any math, I mean, the numbers are useless.
You just need to get the right things that perform the way you want to do.
The only things that you need to know, is the deciBel scale !
Which is pure number, I mean, useless...!
But if you compare...

Also knowing of coherent emissions and know how the thing works in the special loudspeaker application...I mean, usually men use Pc to work out these redundant
computations .

In other words, you are making a system and each part is important.
Yes, the cables are important.

 

[awgrant]

I am planning on using an active crossover to split the audio into two channels, Bass and Mid/tops. Not the existing crossovers!

The JVC/Philips speakers will have all of their internal components left intact, ie the passive crossovers internally will still be functional.

The external active crossover will send a low pass filtered audio signal to the mid/top channel, The JVC/Philips will have that full low pass filtered signal playing through all of their transducers.

The Horn will have the same signal but have a capacitor to filter out the lower frequencies.

The JVC 200 W ? Pleeeeease! If so, I want to see the back! The magnet, I mean...

The JVC is 200W max combined rating for the three transducers in the speaker.