Magnetostat first try out

[Baldin]

Hi All

I'm new to this forum, but have been reading these pages for at while

Just wanted to post a picture of the new prototype magnetostat that I and a colleague have been building for the last many months (yep we are a bit slow).

You can read a great deal more on my homepage for more pictures, and more details of the construction

http://home20.inet.tele.dk/audio/Rib..._Prototype.htm

http://home20.inet.tele.dk/audio/Rib...diy_ribbon.htm


We're using 3M Scotch-Weld to glue the voice-coil to the membrane. Any experience with this spray glue?
Does it last over time?

Had some trouble stretching the membrane, and is thinking on using heat to shrink for the next prototype. Will the used glue take the necessary heat to shrink Mylar?

[stokessd]

Heat shrinking mylar can work very well. You will have to be careful to shrink evenly on both sides or your conductors will shift out of alignment. It takes a bit of practice with the heat gun to shrink but not burn through. Try some plain mylar sheet to get a feel for it. also you want a fairly large heat gun. A small weller designed for heat shrink tubing has too small and concentrated area of heat, and is a nightmare to try to shrink panels with.

I'm very interested in your measurements of your panel. I'm a big ESL and Planar fan. I was going to build some ribbon tweeters, but I like the idea of something that can play down to the midbass. Keep up the good work.


Sheldon

[Baldin]

Will try out the heat shrinking soon.

On Tuesday we'll try to do some measurements


Had a look at your holepage .... impressive

Liked you video of making a ESL ...... seems so easy

Super cool

[stokessd]

Thanks for the kind words. ESL's are surprisingly easy to build.

I am very interested in your planar magnetic experiments. My ESL's sound very good but are not exactly what I'm looking for. They are insanely directional (think laser beams of sound) in the treble. and the bass region has a different radiation pattern from the panel so room issues can be an issue. Aside from the radiation pattern being less than ideal, I love ESL's.

I've owned Magnapan and Eminent Technology speakers in the past, and I do like what they have to offer as well. I'm seriously considering building a narrow Planar/ribbon driver with a woofer under them. I'm thinking of a 48" long ribbon (1/2" wide aluminum foil strip), next to it, something very similar to what you are building, and a transmission line woofer under it. I'm planning to do active crossover, and amps for each driver.

I haven't actually built a ribbon before, but I do have a design in solidworks and from reading the ribbon threads here, I think it's certainly doable for me.

The results of your measurements and impressions will fill in the midrange for my theoretical speaker.

Onward McDuff.

Sheldon

[Baldin]

Here are measurements of frq response, measured at around 1,5 m distance.

The impedance was measured to 2,8 Ohm and the sensitivity 87 db @ 1W/m

Overall I think the measurements look realy good for a first prototype. Bandwidth and sensitivity is as good as we hoped for

The peak at 40 Hz is actually the lower resonance of the speaker. At the used input level the membrane actually hit the stators, making a lot of noise/distortion, which is the reason for the peak.

We also did a directivity measurement, which will be available at my homepage:
http://home20.inet.tele.dk/audio/Rib..._Prototype.htm

Overall a real success I think

Next will be distortion measurements.

[WrineX]

hi there , i started a new post about same subject, also looked at your site but do you ahve some more detailed information about how many magnets you use and also i thought i could see magnets in front and rear. magnepan only uses magnets at front back is only mylar.

so any info is welcome.

and nice measurements btw. only some peaks that need attention but pretty nice for proto type.

for the next version i should try to make the membrane smaller in width wont go as low but then you drive more directly, wich will be les distortion and the highs will be less like a laser beam.



for the stetching i woul try first stretch a little aply glue and then heat shrinkt and then apply the coil.

overal nice work i still looking for magnets without having to pay 100 euro.

nice work