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Author Topic: noobie questio  (Read 3728 times)

daniele violi

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Re: noobie questio
« Reply #10 on: December 30, 2006, 07:32:28 AM »

i hope everyone had a merry christmans  Smile
i just got back and read the replies... thanks for all the great help, this is an really good community.

so i read the ohm theory response, and to tell you the truth i understood very little... so i decided to study up a bit on some more detailed theory and and now i understand what you were telling me and thank you very much for the response. so now i know how to wire my speakers...

by the way awesome website explains it all....
http://colomar.com/Shavano/construction.html

ill upload an image i drew to show my plans...
ill also upload images of the actual drivers to clarify any other insecurities...

if my drawing is a little sketchy, ill explain it...
there are 2 2way speakers... each speaker has 2 devices wired up in series to double the ohms, passive crossover included. now i have 2 2way 8 ohm speakers, which are connected in parallel to reduce the impedance to 4... so my system all together has a 4 ohm impedance.

now i have a couple more questions.
for the crossovers... i dont know if i actually want to buy premade crossovers since i found them locally priced around $20 each, and considering these are pretty crappy speakers and i just want to experiment a bit... i would like to manufacture the crossovers myself. what crossover frequency should i aim for, and what are some simple plans to execute that frequency? (keeping in mind i would use them for dj monitoring and so am not too worried about linearity but efficiency.)

my next question is about amplification. i dont want to buy a stereo amp just for these two crappy speakers and all my other amps are taken up. so i searched around the internet and found something very interesting:
http://www.national.com/pf/LM/LM1875.html
how are these used? are they as simple as they sound? are these actually amplifiers or power amps? do they require a preamp*mixer? could i use these to power my speakers?

any comments are appreciated... am i neglecting something? should i be more worried about some other aspect? are my plans leggit?
how can i push these 4 little devices as much as possible?

thanks in advance




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daniele violi

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Re: noobie questio
« Reply #11 on: December 30, 2006, 07:40:13 AM »

sorry forgot the attachment
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daniele violi

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Re: noobie questio
« Reply #12 on: December 30, 2006, 08:17:46 AM »

i think i made some mistakes in my plans... lets clear some things up... if i have a passive crossover for every 2 4ohm devices then the 2way speaker is at 4 ohms, not 8... right? so if i were to hook  up both 2ways in parallel then i would have a 2ohm system... and i dont want that. i also made a mistake in the crossover drawing, dont mind that. so basicly how should i wire them up... i could just wire the 2 2ways into two different channels to keep a 4 ohm output with the amp.
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Peter Møller

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Re: noobie questio
« Reply #13 on: December 30, 2006, 08:44:48 AM »

daniele violi wrote on Sat, 30 December 2006 12:32

i hope everyone had a merry christmans  Smile
i just got back and read the replies... thanks for all the great help, this is an really good community.

so i read the ohm theory response, and to tell you the truth i understood very little... so i decided to study up a bit on some more detailed theory and and now i understand what you were telling me and thank you very much for the response. so now i know how to wire my speakers...

by the way awesome website explains it all....
http://colomar.com/Shavano/construction.html

ill upload an image i drew to show my plans...
ill also upload images of the actual drivers to clarify any other insecurities...

if my drawing is a little sketchy, ill explain it...
there are 2 2way speakers... each speaker has 2 devices wired up in series to double the ohms, passive crossover included. now i have 2 2way 8 ohm speakers, which are connected in parallel to reduce the impedance to 4... so my system all together has a 4 ohm impedance.

now i have a couple more questions.
for the crossovers... i dont know if i actually want to buy premade crossovers since i found them locally priced around $20 each, and considering these are pretty crappy speakers and i just want to experiment a bit... i would like to manufacture the crossovers myself. what crossover frequency should i aim for, and what are some simple plans to execute that frequency? (keeping in mind i would use them for dj monitoring and so am not too worried about linearity but efficiency.)

my next question is about amplification. i dont want to buy a stereo amp just for these two crappy speakers and all my other amps are taken up. so i searched around the internet and found something very interesting:
http://www.national.com/pf/LM/LM1875.html
how are these used? are they as simple as they sound? are these actually amplifiers or power amps? do they require a preamp*mixer? could i use these to power my speakers?

any comments are appreciated... am i neglecting something? should i be more worried about some other aspect? are my plans leggit?
how can i push these 4 little devices as much as possible?

thanks in advance







Re: the schematic you posted: If the 2 speakers connected to each crossover are the ones you show along with the schematic, you will end up with a 4 ohm load from each cabinet - if you connect 2 of these cabinets in parallel like shown in the schematic, you will end up with a 2 ohm load.

Re: Crossover: These drivers are probably close to fullrange anyways, so I'd skip the crossover and just wire the 2 drivers in series to make an 8 ohm load..

Re: Poweramps:  Look at the LM3875 instead - about 50W into an 8 ohm load: http://www.shine7.com/audio/gainclonev1.htm

EDIT: Re: Poweramps: The amp in my link will do a line level ( CD player etc. ) signal.. If you want to plug a mic directly into it, you need to build a preamp or change R8 and R10 accordingly - google for some opamp theory to figure out how )

/peter
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Andy Peters

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Re: noobie questio
« Reply #14 on: December 30, 2006, 03:30:05 PM »

daniele violi wrote on Sat, 30 December 2006 05:32

my next question is about amplification. i dont want to buy a stereo amp just for these two crappy speakers and all my other amps are taken up. so i searched around the internet and found something very interesting:
http://www.national.com/pf/LM/LM1875.html
how are these used? are they as simple as they sound? are these actually amplifiers or power amps? do they require a preamp*mixer? could i use these to power my speakers?


Some things to realize when building an amp based on this chip (and its brothers):

a) you need serious heatsinking for that chip; otherwise, it'll shut down.
b) you need to have a serious power supply to get any reasonable amount of power.  Sure, you could buy a pair Accopian or Power-One 24V supplies, but by the time you make a chassis for them, and wire it to whatever board you build for the LM1875 device, you've spend enough money to buy a couple of Crown D75s.

So just buy an amp.

-a
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"This isn't some upside down inverted Socratic method where you throw out your best guess answers and I correct your work." -- JR


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Ivan Beaver

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Re: noobie questio
« Reply #15 on: December 31, 2006, 12:18:18 PM »

You do not have a crossover in your drawing.  You have either a band pass or a band cut, depending on particular values used.

Are you trying to use one speaker as a high and one as a low or something else?

You cannot parallel a 2 ohm load and end up with 4 ohms.

I also do not see any loudspeakers in series.

You might want to rethink your drawing.
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For every complicated question-there is a simple- easy to understand WRONG answer.

Can I have some more talent in the monitors--PLEASE?

Ivan Beaver
dB Audio & Video Inc.
Danley Sound Labs
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