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karellen 12th January 2012 09:59 AM

Mini planar magnetic using neos
 
4 Attachment(s)
Hi everybody
I will try to make a mini planars for computer use.
the idea is to make a prototype for evaluation, an then a workable pair.
For now I have the frame and the foil, the magnets will arrive within a week.
however there are some problems to be solved, the first one is the low resistance of the foil; the first measure is 0,6 Ohms, bad thing.
The posible solutions are using a foil of 0,3 mm wide instead the actual 0,5 mm. this probably rise the impedance to 1 Ohm.
Another solution is doubling the length by replicating the pattern on the other side of the membrane, i.e. making a doble layer membrane, with a expected total resistance of 2 Ohms. This will be fine for the amplifier, with the addition of a series resistance of say 2 Ohms.
the active surface of the membrane is 10x18 Cm
What do you think?
Any help is welcome

Pedro

JAMESBOS 12th January 2012 01:14 PM

I would use the epsilon layout which increases the length of the foil it also increases the sensitivity significantly. I wouldn't do a push pull design, I have tried several but there is no significant increase in sensitivity compared to the epsilon layout!!

oshifis 12th January 2012 01:31 PM

You can use an impedance matching transformer.
BTW I have seen a planar PC loudspeaker, same size as a normal PC speaker (except it is flat).

JAMESBOS 12th January 2012 01:47 PM

Or you can use a resistor!

karellen 12th January 2012 04:31 PM

Quote:

Originally Posted by karellen (Post 2858059)
Hi everybody
I will try to make a mini planars for computer use.
the idea is to make a prototype for evaluation, an then a workable pair.
For now I have the frame and the foil, the magnets will arrive within a week.
however there are some problems to be solved, the first one is the low resistance of the foil; the first measure is 0,6 Ohms, bad thing.
The posible solutions are using a foil of 0,3 mm wide instead the actual 0,5 mm. this probably rise the impedance to 1 Ohm.
Another solution is doubling the length by replicating the pattern on the other side of the membrane, i.e. making a doble layer membrane, with a expected total resistance of 2 Ohms. This will be fine for the amplifier, with the addition of a series resistance of say 2 Ohms.
the active surface of the membrane is 10x18 Cm
What do you think?
Any help is welcome

Pedro

Hi Henry
I'm not thinking on a push pull arrangement, but on puting aluminium foil on both sides of the membrane.
Does anybody have tried this?

And about the resistor... Which value?
An 3 Ohm resistor will eat almost all the voltage, I suposse...

karellen 12th January 2012 04:40 PM

Hi Oshifis
 
Quote:

Originally Posted by oshifis (Post 2858309)
You can use an impedance matching transformer.
BTW I have seen a planar PC loudspeaker, same size as a normal PC speaker (except it is flat).

Where can I find a matching trafo?

karellen 12th January 2012 04:45 PM

Quote:

Originally Posted by JAMESBOS (Post 2858293)
I would use the epsilon layout which increases the length of the foil it also increases the sensitivity significantly. I wouldn't do a push pull design, I have tried several but there is no significant increase in sensitivity compared to the epsilon layout!!

The epsilon layout seems very interesting.
The magnets are too slim, thought, so lets see

Thanks for the help

JAMESBOS 12th January 2012 09:39 PM

Quote:

Originally Posted by karellen (Post 2858587)
Hi Henry
I'm not thinking on a push pull arrangement, but on puting aluminium foil on both sides of the membrane.
Does anybody have tried this?

And about the resistor... Which value?
An 3 Ohm resistor will eat almost all the voltage, I suposse...

I wouldn't put foil on both sides of the membrane, this will double the weight and make it less sensitive! The resistor depends on the resistance of the foil and whether you want a 4 ohm,8 ohm or 16 ohm to go with your amplifier. The resistor hardly has a effect on the sensitivity.

JAMESBOS 12th January 2012 09:46 PM

Quote:

Originally Posted by karellen (Post 2858619)
The epsilon layout seems very interesting.
The magnets are too slim, thought, so lets see

Thanks for the help

The epsilon layout is the best I speak from experience as I have been building planars for over 20 years.The magnets can be the size you require you lay out the foil to fit the magnet sizes.

JAMESBOS 12th January 2012 09:48 PM

Quote:

Originally Posted by karellen (Post 2858059)
Hi everybody
I will try to make a mini planars for computer use.
the idea is to make a prototype for evaluation, an then a workable pair.
For now I have the frame and the foil, the magnets will arrive within a week.
however there are some problems to be solved, the first one is the low resistance of the foil; the first measure is 0,6 Ohms, bad thing.
The posible solutions are using a foil of 0,3 mm wide instead the actual 0,5 mm. this probably rise the impedance to 1 Ohm.
Another solution is doubling the length by replicating the pattern on the other side of the membrane, i.e. making a doble layer membrane, with a expected total resistance of 2 Ohms. This will be fine for the amplifier, with the addition of a series resistance of say 2 Ohms.
the active surface of the membrane is 10x18 Cm
What do you think?
Any help is welcome

Pedro

using this layout you won't get much sound.THE EPSILON LAYOUT IS A MUST.


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