Vintage German 12" Alnico Driver - diyAudio
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Old 11th April 2006, 12:40 PM   #1
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Default Vintage German 12" Alnico Driver

Does anyone have experience on mounting a thin metaldome to a vintage driver of this kind, in order to extend hf output?

The driver has fine resolution up to 5Khz.

Detailed photos of the driver here: http://homepage.mac.com/tgroendahl/PhotoAlbum1.html

Also I seek information about the C37 laquer treatment, would it in- or decrease the performance of such a driver with itīs light papercone, large alnico motor and phonolic spider?

For a while a had them mounted in 3 x 4 feet open baffles. Not much bass, but a fantastic intimate and pure midrange. Consider to try 5 x 6 feet baffles, and would be happy to hear about experiences with this matter also.

Thanks in advance!

Regards,
Thomas
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Old 11th April 2006, 07:14 PM   #2
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Nice drivers. While I can't answer your questions, I would tend to pass on the Damar. Looking at the surround, these don't look like they were intended to make bass. If you like them as they are, I'd leave them and add a bass driver.

You know, you could try a phase plug as well, being that they don't appear to have a dust cap. The aluminum cap sounds interesting as well.

One other thought, on an old pair of Isophons I have, they do have a coating down near the center of the cone. I'd imagine this was to stiffen the cone a bit to help with the treble, but that's just a guess. If it were me, I wouldn't coat the cone, expecially on this nice of a driver.
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Old 12th April 2006, 02:56 PM   #3
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These bigger FR drivers roll off quite early, so as mentioned you can try a phase plug or even the metaldome tweak... there should be some improvements but I still would expect the highs to be insufficient. One other option you can try is to get a cheap high efficiency tweeter with a simple capacitor as a crossover...and using wires/bars to suspend the tweeter in the center ie turn it into a Coaxial driver. IMO this will be a better option.
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Old 12th April 2006, 04:55 PM   #4
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Thanks for the replies!

Unfortunately the driver can never become full range, therefore I considered to tweak it to become somewhat more wide range than now, where it rolls off gently after 5Khz, but still has audible output at 12Khz, but still with the addition of a supertweeter.

For a while I have been using vintage Fostex T-825A hf-horns, with a 5uF (PIO/phenolic-paper encased) capasitor as a simple filter + a few carbon resistors in series/parallel to adjust level and impedance.

Have an opportunity to get a set of JBL LE-5 aludomes that fits exactly. But a phase plug could be interesting to try as well. Guess that some sort of wood would be the optimum material to have them turned out from.

At the moment I have placed a set Altec Duplex 605Bīs on top of the large backloaded horns that currently houses the 12" drivers, but only using the horn of the Duplex as tweeter. This combination plays really sweet together.. (The Duplex drivers is my other speaker project).

BTW, the coax arrangement that you suggest, I have seen on the site mentioned below, done on a Siemens 15" speaker.
It looks really interesting! One pair they made is even for sale.

Best regards,
Thomas

P.S. May I recommend a great new site for vintage speakers:

http://www.german-vintage-loudspeakers.com/
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Old 12th April 2006, 06:59 PM   #5
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http://www.partsexpress.com/pe/showd...number=275-035

I would cut the flange off of that tweeter and affix it to the pole piece in the middle.
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Old 13th April 2006, 10:43 AM   #6
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Thanks Tade,

But the Dayton tweeter is 93db/m/W and the 12" Philips is 98db, so efficency will not match. The frenchmade coaxial driver Phy-Hp KM-30 has a nice looking tweeter mounted, which is also sold seperately, but itīs unfortunately to large in diameter:
<http://phy-hp.com/English/Products/TW37_E.html> It would though match in effciency.

Yesterday on http://www.german-vintage-loudspeakers.com/ I found a link to another vintage audio website: http://www.bmw2002.nl/philips.html where my speaker (model#2278) is listed as a component in Philips cinema installations.
So finally I found documentation.

Best regards,
Thomas



http://homepage.mac.com/tgroendahl/PhotoAlbum1.html
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Old 13th April 2006, 05:14 PM   #7
tade is offline tade  United States
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aha, i have an answer for you then. The piezo element in that tweeter looks EXACTLY like the on from this tweeter:
http://www.partsexpress.com/pe/showd...number=270-011

The piezo element itself has a very high impedance as stated and also iis mechanically limited to high frequencies. What that means is that you can simply attach the tweeter in paralell with the woofer and maybe use a cap to adjust the crossover frequency.

I have dissasembled this tweeter and inside there is a piezo disk with a paper cone glued to its center. the tinsel leads shoudl be used to support the disk and cone to allow them both to vibrate. Give them a try, they are cheap.

Good luck
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Old 13th April 2006, 08:28 PM   #8
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quote;

I would tend to pass on the Damar.

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C37 and damar are not quite the same thing-

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this driver may lose significant value, as a historic piece,

and monetary, should it be modified in any way!

Something to consider.
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Old 14th April 2006, 09:59 AM   #9
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Hello Tomtt.

Thanks a lot for your wise comment!

The photos are now published at the http://www.german-vintage-loudspeakers.com/.
Just after that I got in contact with a gentleman that has a site dedicated to vintage Philips gear: http://www.bmw2002.nl/home.html. Finally after two years of research, I found information on this rare driver. Maybe I should just stick to a two-way set-up, eventually adding a large woofer to compensate for the quite low lf-output...

Best regards,
Thomas
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