Full range planar speaker using neo magnets

[JAMESBOS]

MORE NEO REBUILDS.

more!!

 

[JAMESBOS]

and more

I no longer use the epsilon layout too much work for little return.

 

[JAMESBOS]

and more

ditto

 

[EternaLightWith]

thickness of mylar

I was looking at regular mylar and the metalized mylar.

The thinnest is 0.9 - 1 mil which converts to 24 micrometers (microns).

Maybe I missed it, but how thick is the mylar itself?

Earlier in the thread Henry was talking about 12uM , which I assumed was referring to the thickness of the aluminum tape.

Anyone have ideas on mylar/aluminum coating thickness? I was thinking you'd have to take in account the thickness of both layers, if going the metalized mylar route.

Sincerely,

David P.

Edit: Was reading http://www.magnetostatic.com and he said the thickness of both aluminum and mylar was 12uM which together is 24uM which does equal 1 mil thickness. So I guess the assumption could be made that 1mil (24uM) thick metalized mylar is 12uM/12uM mylar/aluminum.

 

[JAMESBOS]

Upgrade of covers and repair caused by old age and senility

Replacement of ruined diaphragm and new covers for hanging full range planars.:-

 

[JAMESBOS]

THE NEW COVERS

The new cover ready to be hung after repair. 2 more to do but problem with the one over the door size wise. Not made my mind up yet what to do!!

 

[JAMESBOS]

The original covers of differing shades of blue, will make good dust covers!. The canvas pictures are more in line for married men! You could give her the choice of picture, this will help if you have problems with your better half. The pink dhalias look nice.!!

 

[JAMESBOS]

DE-CLUTTERING.

Will be removing large ferrite uncovered ones, less clutter so I can do more measuring, when I have sorted out software to do so! Any tips would be appreciated.

 

[JAMESBOS]

The actual canvas covered speakers sound better, not so harsh, which seem to be a trait of the neo magnets I have found. Or it may have something to do with the size, although I have built larger neo ones, which still sounded harsher than the larger ferrites. The ferrites do sound more mellow and not as strident!?

 

[SEdwards]

There is probably a rising response if the diaphragm is really lightweight.

I think that Room EQ Wizard has it covered for frequency response graphs, and is free and unrestricted. I use the demo of ARTA to check distortion.

Do you already have a mic?

 

[JAMESBOS]

I have got 4 microphones, but I don't know how good they are, one came with my ONKYO Receiver , which is used to set the speakers up! 2 are SONY ones I bought nearly 40 years ago. Just ruined another 2 diaphragms on my 4' x 2' ferrite planars, moving them into the garage, but I won't be rebuilding them yet. so delicate 12 um Mylar. I'm getting worse as I get older.

 

[SEdwards]

Maybe you can find a curve of the Onkyo somewhere online, where people have used it in REW.

The Panasonic capsules are about $2 or so and definitely good enough for measurements.

 

[JAMESBOS]

I have had a rethink on the epsilon layout, must do more experimentation, will get back when finished, more rebuilds, again,c'est la vie.!!?

 

[gootee]

Good. Enjoy! Some day I hope to have time to try similar things.

You can download free software, such as ARTA, that will let you use a mic in conjunction with a computer sound card, to perform speaker measurements. You might need a mic preamp. If you post the mics' makes and model numbers, someone might be able to say exactly how it might be able to be done, with one of your mics.

Cheers,

Tom

 

[JAMESBOS]

Have found out using the epsilon layout when you use 12.7 mm wide neo magnets is a waste of time. The one I rebuilt using the epsilon layout is 8 Db down on a ferrite magnet one using 18 mm wide ferrite magnets. You live and learn. Whereas the ferrite 18 mm wide magnets use 2 foils on the magnet body you can only get 1 foil on the 12.7 mm neo magnets this is the secret to the difference in the sensitivity.So the 60 x 40 using 18 mm wide magnets with the epsilon layout is 8 Db more sensitive than a 4' x 2' one using the epsilon layout and 12.7 mm wide Neo magnets. C'est La Vie.

 

[brian t]

Henry so are you saying there is no advantage using neo,s over ferrite magnets,thats good cost wise when i get around to reverse engineering my epsilons as i wish build a larger pair and the cost of the magnets is a big factor.

 

[geraldfryjr]

Are the thicknesses of the magnets the same?

The distance of the foil to the magnets will be a big contributing factor to the difference in sensitivity.

Also the total resistance of each foil will make a difference as well as this determines how much current is flowing through the Voice Coil as the current is directly related to the magnetic field.

If all else is the same then then doubling of the current in the foil by either doubling the voltage or adding a second foil then you should get an increase in sensitivity.

If you double the voltage with the two foils this will maintain the same current as a single foil providing that they are in series.
But as there are two foils contributing to the magnetic field this should increase the sensitivity by 6db.

Also the sensitivity will drop by 6db if the distance of the foil to the magnets is doubled and it will be increase by 6db if it is halved.
So therefore if you are talking about a distance of an 1/8" then as little as 1/32" to 1/16" can make a big difference in your end sensitivity.

Neo's are definitely more powerful when comparing them to a ferrite of exactly the same size.

Earlier (in another thread) I had shown how I made a simple magentometer to measure the field strength of the magents and I had found that by stacking them was just like connecting battery's in series and every time you doubled the number of magnets in the stack (thickness) the field strength was doubled as well.

http://www.diyaudio.com/forums/plan...transformer-ribbon-tweeter-2.html#post2504316

It was very simple to make using a an EMI core torn out of a dead PC supply.
I very useful tool indeed when working with magnets.

Cheers!!!

jer

 

[WrineX]

If you double the voltage with the two foils this will maintain the same current as a single foil providing that they are in series.
But as there are two foils contributing to the magnetic field this should increase the sensitivity by 6db.

did not notice this btw. i did a setup with 2 coils with foil on top of eachother(spaced by some tape), measured one coil then 2 in series, i ended up with an increase of only 1.5 dB, ofc there was extra weight of the foil + the tape that serperated them from eachother. so i can imagine a little bit more dB gain if the extra weight whas not there.

while in paralel it increased by 6 dB.

am i missing something ?

 

[geraldfryjr]

I may be wrong in my estimation as I was thinking originally it might only be a 3db increase.
I am not good with math when it comes to converting db's in my head.
So 1.5 db may very well be the correct factor.

jer

 

[JAMESBOS]

Henry so are you saying there is no advantage using neo,s over ferrite magnets,thats good cost wise when i get around to reverse engineering my epsilons as i wish build a larger pair and the cost of the magnets is a big factor.

Yes there is no advantage in using the epsilon layout with 12.7 mm wide neos against 18 mm ferrites.I am listening to a ferrite planar 60 x 40 mm on the left, against a 4' x 2' neo one on the right. I have to run the neo one 8 Db higher to get them equal in volume. The ferrites are 50 x 18 x 10 mm and the neos are 50 x 12.7 x 3 mm. When I used the normal layout of the tape they were equal in sensitivity on the neo one. Also the ferrite ones are a lot smaller and about the same weight.The resistance of both are 6.6 ohms exactly. I am in the process of working out the layout for some 25 mm wide ferrites I have.Not easy at my age. I'm glad I don't have to rebuild all my 60 x 40 planars, I have 11 in the living room hanging from the ceiling. Iwill only have to re-build about 10 ferrite ones,again.!! C'est la vie.