Who has done this ?........ ( Older ALTEC Woofers )

Quote:

---

Originally Posted by 604man

I lived in a hot enviroment with my 604-8G's and never had this problem ......A sloppy job

applying dope to the surround. Must be A non Altec / DIY re-cone job....Fortunately,

Easily repaired.

Jeff, how much of the dope did you remove ? Is the surround still shiny ?????

Do you have pictures ????.....GC

---

Hello 604man !!

You asked some very good questions :

"Jeff, how much of the dope did you remove ? Is the surround still shiny ?????

Do you have pictures ????.....GC "

------------------------------------------------------------------

(1) I would say, in the accordion area, I have removed about 90 percent of the goop, but it remains between the frame and the outermost surround.

(2) YES, in the treated area, it remains surprisingly STILL SHINY, evenly shiny, like I can't see the cloth weave beneath it easily, and it "looks" to my untrained eyes to be adequately sealed, like no air would get through, unlike Per Hasling's photos. Its an EVEN shine, and it appears to lay thin on the cloth.

(3) No photos, my digital camera broke three weeks ago, not yet replaced. See my description above in number (2) please.

Just GUESSING 604man, I would intuitively say from eyeballing the surround that the chance of it not leaking air, and being aperiodic, is 80 % out of 100. Its much improved sonically over the other stock sloppy gooped 515B.

Without further input from Forum Members, here is what I would like to do ( at this point. )

MEASURE things !! Free air resonant frequency of the cleaned and "stock" drivers. It will be a couple months until I get A7 enclosures and brace them, so I will continue using the driver, in mono, and remeasure its resonant frequency in a few months. Then decide IF I should clean the other untouched 515B in a similar manner.

IF I was worried in Q2 2014 about the surround leaking, I could apply very dilute amount of SuperZRC56 glue ( reduced in water, it dries flexible and shiny ) and seal the surround more. Then, I will remeasure the resonant frequency again, just to document that.

My old laptop went kaput. I will have to buy a new laptop, and put the software on it for frequency sine wave generation, sweep-frequency generation, etc etc, so I can measure the drivers in free air.

With a microphone I will also apply this new software to setting-up the A7 enclosures, getting the port size and dual resonant bumps correct. Why did I throw away all my analogue test equipment ten years ago ??

Comments, critique, tips welcomed. Thank you very much ! I am enjoying this 515B and 802-8D /511B in free air a whole lot, very precise drivers !!


Jeff Medwin

I'm no chemist, but I'm pretty sure that no water based goop will stick to oil based goop. :confused:

I wonder if the amount of goop is important for the function of the surround as in controlling the cone and such. I thought that I read something to that effect reading the thread and patent filing for the bioflex woofer.

I think that you should at least build a baffle board for your components. Both of them.

Hi Jeff.
Check this site if you're still looking for an appropriate solvent:

Chemical Resistance Chart | Custom Advanced

The goop is a butyl product I believe so anything with a C or D under the butyl column would be a functional solvent. You can do some extra research from there to find one that won't cause mutations in humans or melt the cones and frames on the drivers.
Toluene is sold as Toluol in hardware stores is a likely candidate and it's about $5 a pint.

Quote:

---

Originally Posted by zelgall

Hi Jeff.
Check this site if you're still looking for an appropriate solvent:

Chemical Resistance Chart | Custom Advanced

The goop is a butyl product I believe so anything with a C or D under the butyl column would be a functional solvent. You can do some extra research from there to find one that won't cause mutations in humans or melt the cones and frames on the drivers.
Toluene is sold as Toluol in hardware stores is a likely candidate and it's about $5 a pint.

---

Hi Zelgall,

Yes. Thank you, thank you...good reference there.

I bought a gallon of Toluene - as a result mostly of 604man's suggestion. Found it at ACE Hardware a week or so ago. Have done ( or is it "done -in" ) one of the two 515Bs, and am enjoying it thus far - quite a lot.

I spent all-day yesterday optimizing the Rk on my SE DC amp's driver stage. It took a combination of SIX different uF values of film, paper in oil, and teflon caps to optimally bypass the input / driver tube's cathode resistor ( Rk - 6SL7WGT ).

A high quality film cap can measure linearly on the bench, but when you apply said capacitor in an amp in a cathode bypass position, the best of them only plays a surprisingly small frequency band under dynamic conditions. Hearing and knowing this, I experimented between paper and oil, teflon, and silver mica types yesterday all day until I got BOTH the values and types I liked the most. A mind-boggling exercise when this is heard.

These (new to me ) ALTEC drivers are wonderful to use. The 802d is very transparent sounding, and it easily allows me to hear different caps, and determine what sounds most linear and most honest, at least to my ear.

By the end of the day, I was able to get the triangle at stage-right in Gilbert and Sullivan's " Three Little Maids " to play tonally and harmonically correct and with full resolution and full decay at the end of a note, whereas, previously, the triangle was totally MIA ( missing in action ) on the 802d/ 511B.

It wasn't a speaker problem, it was a tube amplifier optimization problem !! Amps, not speakers, are the weakest link IMHO. A "FUN" and exciting audio day. Sorry to go off topic, but I am excited over what I heard.

Jeff Medwin

So which caps ended up the winner?

Quote:

---

Originally Posted by zelgall

So which caps ended up the winner?

---

Multiple values of the Russian teflons ( K72 and FT-2 ) edged out the Russian Silver Micas and the P.I.O.s ( K-40y) in this Rk bypass application Zelgall. I did use one PIO in the bunch.

I have a box of .1uF k72's. They're nice as a coupling cap as well in some applications.