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bentl 29th August 2010 08:08 PM

Planar speaker - first try
 
1 Attachment(s)
Hi,

I have decided to built a magnetic driven planar speaker.

Got most of the parts, and the design is illustrated below. A perforated steel plate as I have used in my ESL projects, with 10x10x40mm neo magnets. A alu frame in 1/2" x 1/2" square alu tube provides stiffness and spacing between diaphragm and magnets (distance will be 2,7mm + 1mm vhb tape.

Attachment 185838

Diaphragm will be 6micron mylar, with 9mm wide CPC alarm tape as conductor (0,6 ohms/meter resulting in a 5,4 ohm dc resistance I should imagine.

Horisontal spacing between magnets will be 15mm, and 10mm vertical spacing.

Outer dimensions of the frame will be 190mm wide and 1000mm high.
There will be 8X18 = 144 magnets pr speaker.

As the back plate is bigger than the diaphragm, it will be easy to mount baffles, and easy to add a ribbon tweeter if I should decide to do so later.

I am very exited by this project, it should be easy to build and hopefully give more satisfying results than my ESL attempts has given so far.

Any comment to my idea? Should i make it wider, bigger/smaller distance between magnets, distance between magnets and diaphragm?

Theese magnets cost a fortune, so I am reluctant to increase the number of magnets in the first test (I have 205 in stock)

All that remains now, is to unite theory with practice and see how it turns out!

Regards,

Bent

WrineX 31st August 2010 07:24 PM

THat looks promising, with alll those powerfull magnets. by the way how did you get the tape and what is the width of the tape and most of all where did you get it. i looked like everywhere to get aluminium tape in small width also in the security branche but it looks like they dont use it anymore or something. i still got 4 perf plates with all the magnets of a Magnepan wich i would like to use for something after all the searching


sorry you metnion the width of the tape :) but with 0,6 ohm a meter this is nice thing foil

bentl 31st August 2010 07:45 PM

Hi,

I got the tape from cpc.co.uk by recommendation from mr JAMESBOS
They ship internationally but have a rigid ordering system with prepayment.
5 rolls costed me 5 GBP and 18GBP including freight

The tape is 0,006 thick, 9mm wide. I haven´t opened the tape yet, so I am unsure if it comes with a liner or not. If it has a liner it can be rolled out and splitted in half.

I have decided to order some more magnets and make the speaker a bit bigger, and have a few magnets in spare for some ribbon tweeters.

Regards,
Bent

WrineX 31st August 2010 08:53 PM

splitted in half ? what do you mean, so the tap is 4.5 mm ? or. dont know what a liner is :) i amfraid explain :)

chinsettawong 1st September 2010 02:33 AM

Hi Bentl,

It looks like a fun project. Please keep us updated.

Wachara C.

bentl 1st September 2010 07:09 AM

Quote:

Originally Posted by WrineX (Post 2289592)
splitted in half ? what do you mean, so the tap is 4.5 mm ? or. dont know what a liner is :) i amfraid explain :)

Hi,

tape is 9mm wide, but if it has a peelable backing/protection one can lay it out on the table and split it in half with a knife to get 4,5mm...and then run 2 lengths.

Bent

WrineX 1st September 2010 10:05 AM

Thx for the explanation. wel the knife thing is a horror i used it on normal aluminium tape to cut it in small tapes. did not really liked the work and the result. but 0.6 ohm a meter for a 9 mm width tape is also really nice so im gone get a look at the site Many THx. and keep us updated im really curious

bentl 1st September 2010 07:14 PM

1 Attachment(s)
Hi,

uploading a new illustration on how it is going to be built. I guess I will make the trim out of pine, and wax and polish it in a dark wood colour.

Planning on making a inner frame that holds the speaker grill cloth, and fit it with magnets so it snaps to the perforated plate.

I am planning on casting the base in concrete, the type used on bathrooms. It's on sale this week ;-)

Attachment 186172

I might have to reduce the widt of the speaker element in order to fit a ribbon tweeter.

Regards
Bent

bolserst 1st September 2010 07:25 PM

1 Attachment(s)
Quote:

Originally Posted by WrineX (Post 2290112)
Thx for the explanation. wel the knife thing is a horror i used it on normal aluminium tape to cut it in small tapes. did not really liked the work and the result. but 0.6 ohm a meter for a 9 mm width tape is also really nice so im gone get a look at the site Many THx. and keep us updated im really curious

For cutting aluminum tape and thin diaphragm material I have found rotary razor blade cutters to work well, cutting smoothly in straight lines without snagging, wrinkling or tearing.

bentl 1st September 2010 08:24 PM

Yes, I got some of those. search for "olfa rotary" on the ebay. Quite cheap and very useful.

And VERY sharp, mind the fingers when replacing the blade!


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