large advent crossover help needed

[kenhappen2u]

Hello all and thanks for your time reading this .... i have a pair of original large advent speakers in the walnut cabs . the speakers/drives are all working and sounding pretty good , the only problem i have found is that the switch for normal, decrease , increase seems to have no effect when changed . ( deoxit did not work either )

would this or could this be just a cap problem ? or could it be a resistor . coil,or choke , problem as well ?




ps , i am going to be doing a recap job on them this afternoon and plan on using some good pollypro's on both the tweeter side and also on the woofer , one concern i have is that i will need to wire a couple the caps i have in series on the woofer side only in order to get the 8 uf value i need .( will this work ?) i will be using 1 very large ( in size) 10uf and 1 - 4.7 uf in series to get a rough value of 7.3 - 7.4 uf of my needed 8 uf ,
my question is ...... is this value close enough to the 8 uf caps needed on the woofer side? , and if not would you recomend that i just use some cheaper n-p electrolytic's for a perfect 8uf match that i have in stock for the woofer side only and use what better pollypro's on the tweeters .
Both woofer and tweeter require a single 8 uf cap in the crossover ......hope this helps

parts avail .. non pol
2- 10 uf polly pros 370v @ 10 %
6- 4.7 uf polly pro's 400 v 10%
2 - 7 uf polly pro's 250 v @ 10 %
2- 2.2 uf polly pros 600 v % 10%
2- 1.0 uf polly pro's 400 v 10 %
4 - . 47 polly pro's 400v 10%
4 - . 22 polly pro's 400v 10%

non pol
electrolytic in stock

2 - 4.7 mfd 100v
2 - 3.3 mfd ,100v



thanks in advance ...ken

 

[dc270]

You might measure the rated resistance on each resisitor off the switch- they could be defective. Check your switch as well as I have had them go bad as well.
The 8uf for he tweeter- I would use a couple of the better 4.7 paralleled- the +/- 10% is plenty close enough. The electrolytics for the woofers.
Good luck- they do sound better after a good re-cap!
DC

 

[GordonW]

Here's how I'd do it-

7uf poly plus 1uf poly = 8uf on the TWEETER.

4.7uf poly plus 3.3uf electrolytic = 8uf on the WOOFER.

Should sound just fine! :thmbsp:

Regards,
Gordon.

 

[kenhappen2u]

Here's how I'd do it-

7uf poly plus 1uf poly = 8uf on the TWEETER.

4.7uf poly plus 3.3uf electrolytic = 8uf on the WOOFER.

Should sound just fine! :thmbsp:

Regards,
Gordon.

Gordon , thanks a bunch for your input . but i now have a new problem regarding the caps voltage value , i guess i missed read one of the 3.3 uf caps voltage and thought i had 2 of them at 100 v , it turns out one of them is a 3.3 uf at 50 v and one at 100 v . is 50v is to low ? i just called my local radio shack and would you believe they seem to be fresh out of 3.3uf @ 100 v . ...

 

[kenhappen2u]

Here's how I'd do it-

7uf poly plus 1uf poly = 8uf on the TWEETER.

4.7uf poly plus 3.3uf electrolytic = 8uf on the WOOFER.

Should sound just fine! :thmbsp:

Regards,
Gordon.

Gordon & DC, thanks a bunch for your input . but i now have a new problem regarding the caps voltage value , i guess i missed read one of the 3.3 uf caps voltage and thought i had 2 of them at 100 v , it turns out one of them is a 3.3 uf at 50 v and one at 100 v . is 50v to low to use ? i just called my local radio shack and would you believe they seem to be fresh out of 3.3uf @ 100 v . ...

 

[Zilch]

So, you don't want to use a 50V NPE (which would be fine, insofar as voltage rating is concerned,) and thus will go shopping for a 100V one?

Buy two MPP 3.3s to parallel with the 4.7s and forget the NPEs altogether. If you're buying caps, thats the better solution. :yes:

No way would I use NPE in ranges that MPP are available and reasonably priced....

 

[GordonW]

Since you don't have a matched pair of 3.3uf electrolytics- I'd go with Zilch's suggestion.

I don't like the idea of 50v caps in crossovers in this day and age (it's easier to blow up 50v caps with modern big amps, compared to the smaller amps of earlier years), and I also don't like the idea of mis-matched caps.

Regards,
Gordon.

 

[Doug G.]

Hold on a minute here!

In the original Advents, there is no capacitor in series with the woofer. Only a 1.5mH inductor.

There is a series capacitor in the tweeter circuit which is 16uF and another one which gets switched in in the increase position to bypass the 3 or 4 ohm resistor.

Early models (up to about 1975) have a 16uF cap. here and later ones have an 8uF cap.

The effect of replacing the 16uF with an 8uF is to reduce the lower frequency load on the tweeter (lets less lower frequencies through).

This may have been a change to lessen the frequencies of tweeter failure in the field (for those of you in Rio Linda - how often they break :^).

Doug

 

[VPFLYER]

I'm confused also. I have a pair of original large advents I'm working on. Let me be clear, these are the masonite ring woofers. Below is a pic of the Crossover in mine prior to any work by me. Two 16uF electrolytic caps, one for tweeter and one for woofer, I thought?

I've read that later ones changed the tweeter cap to 8 or 8.2uF and those who do updates do this also. But that the woofer remains 16uF.

Mike

 

[VPFLYER]

Here's a better picture.

Mike

 

[kenhappen2u]

i have not opened them up yet tonight as planned to see for sure if they have 2 - 8uf or 16 uf caps, i thought i saw/read a post earlyer in the week with pictures of original advent with 2- 8uf caps ... thats what i was going on , i trust you guys know what your talking about ....cuz i dont . thanks for all the help .
Ken

 

[powerman]

Stop by

Ken come on by this weekend and I can rebuild them for you. I have a large
selection of caps. You replace what you need for yours. Various brands of
caps

 

[kenhappen2u]

Dave , HEY THANKS FOR THE OFFER ....i may just take you up on that. do you have any polly pro caps in your collection? looks like i will need 2 - 16 uf or 1 - 16uf and one 8 uf in each speaker . i have a couple of caps but not sure if i have all the one's that i would need . i can give you a call tonight or tomorrow morning and we can go fom there , thanks again for all your guys help. this is what makes this forum/ site so special .... and all for the love of music !

Ken

 

[powerman]

Do you want to use bypass caps too. Have some Theta and Daytons

 

[chambcra]

I have a couple 1971 large advents with the original two 16's, I'm 56 years old, and listening to orchestral music off the radio, I can just barely detect any difference in the switch positions. If I listen to the white noise generator that the tuner uses for adjusting the speaker levels I can hear the difference plain as day.

 

[currituckco]

I just got a pair of large advents - mismatched unfortunately - one very early with the 16uf/16uf and one slightly later production with 8uf/16uf. Both with masonite rings and original drivers. I refoamed and recapped both with 8uf/16uf daytons. they sound great.

Here's where I got my information:

http://www.audioasylum.com/forums/vintage/messages/87637.html

This tells you which of the caps to make 8uf, if you have the original 16/16 configuration. I found that after breaking them in for a bit the extended position sounds best.

 

[VPFLYER]

I just got a pair of large advents - mismatched unfortunately - one very early with the 16uf/16uf and one slightly later production with 8uf/16uf. Both with masonite rings and original drivers. I refoamed and recapped both with 8uf/16uf daytons. they sound great.

Here's where I got my information:

http://www.audioasylum.com/forums/vintage/messages/87637.html

This tells you which of the caps to make 8uf, if you have the original 16/16 configuration. I found that after breaking them in for a bit the extended position sounds best.

Ditto all above. I also used the AA post by Bold Eagle for reference. Just hooked mine up last night. My first Original Large Advents. I think they live up to their legend. I'm going for a second set soon.

Mike

 

[kenhappen2u]

ok , well i just opened them up to find that they do indeed have 2- 16 uf caps . ... burried under 4 blocks of yellow foam padding . (first time iv'e seen that ) looks pretty str8 forward.
So from what i can tell...it would be an upgrade to change the 16uf going to the tweeter to a 8 uf ?

(Quote from Bold Eagle )
Later production had a 16 uF high pass filter cap, and an 8 uF bypass cap. I highly recommend this later configuration. If your Advents have 2 of the 16 uF caps, it's the earlier production. OK, so which of the two 16 uF caps do you change to 8? It's the one placed above the switch. It runs from the center terminal of the switch on the upper side, to a terminal on the Masonite board, and from there to the tweeter. The one that has to stay at 16 uF runs from the input terminal to the far end of the switch on the lower row of connections. I hope that's clear.

 

[currituckco]

ok , well i just opened them up to find that they do indeed have 2- 16 uf caps . ... burried under 4 blocks of yellow foam padding . (first time iv'e seen that ) looks pretty str8 forward.
So from what i can tell...it would be an upgrade to change the 16uf going to the tweeter to a 8 uf ?

According to Bold Eagle, the 8uf is the better performer. Mine sound great with this configuration.

I was told right after I bought these speakers that they "hate tubes" - I did find that they seem to perform better with solid state. The sound was slightly muddy with a rebuilt dynaco sca-35, and considerably cleaner and more dynamic with a 90s yamaha AX-592 receiver. Exactly the opposite of my experience with my Ohm L speakers.

Now I want to find a nice vintage marantz or sansui late 70s receiver to try with the advents....

here is another interesting article, this one about refoaming the woofers. I used this method and it was great, barring one failed attempt at gluing the outer edge - i did a bad job of gluing (let the glue set for too long and it did not stick) and in regluing i was not careful enough not to disturb the centering of the woofer and the coil was rubbing. so i had to unseal the glue and try again, this time with great results. I recommend first applying glue to the inside of the masonite ring, then immediately to the foam, then immediately sealing, not letting the glue set. I had the best results this way.

the post:
http://db.audioasylum.com/cgi/m.mpl?forum=vintage&n=129012&highlight=advent+crossovers&session=

 

[VPFLYER]

From Currituckco above: "I recommend first applying glue to the inside of the masonite ring, then immediately to the foam, then immediately sealing, not letting the glue set. I had the best results this way."

I agree with Currituckco on this. The glue does not seem to soak into the masonite quickly if a relatively thick layer is laid. On the foam it seems to dry out quicker. So on my next pair I'll do masonite first and foam second.

There is a video in a post another AKer found which shows a whole re-foam operation. I've saved it for future ref on my PC. I'll try to find it. Here it is at the bottem of this site page.

http://www.wooferrepair.com/faq.html

Also another AKer (or same one?) explained how they manulated the cone and foam to glue easily and not smear glue all around. Maybe I can find it. Here it is from AKer GONZOTHEGREAT:

"Just some brain farts on specific driver refoam jobs...

Advent woofers with the masonite ring/DQ-10 woofers
I've only done three of these and one had to be redone before I figured out a good technique. Clean up the ring and cone with your favorite adhesive solvent. I prefer acetone dabbed on with qtips then scraped with a butterknife (the knife is quite effective at scraping the underside of the ring w/o removing it). If any adhesive remains, one last swab with qtips will usualy clean it down to the cone.

So much for the cleanup. Glue the appropriate foam with the arched side down to the top of the cone with the outer lip *below* the masonite ring. Yes it makes things a bit harder in the next step but that's how they did it at the factory and who am I to argue? Let the glue dry for 4-6 hours. Now for the big finish! Apply glue to the foam edge and wait 5 minutes for it to get tacky. Grab a 1.5v D cell (or an audio generator with adjustable DC offset) and hook it up so the cone pushes out toward the masonite WITH THE WOOFER POINTING DOWN. The woofer inversion helps counteract any spider sag. If you're using a generator, crank it up so the cone is roughly even with the ring. Now run your finger or other pointy bit along the glue seam a few times and repeat after a few minutes. Let it dry for 20-30 minutes with the woofer inverted and voltage applied. Then remove the voltage and set aside to finish drying (still inverted). Be sure to test the woofer horizontally and vertically. I've had drivers that didn't scrape until they were installed - d'oh!"

Back to my personal experience. I shimmed the voice coils when i did mine because I wanted to try it and since it was my first effort at re-foaming, I didn't trust myself to use the battery method. Several have used the battery method of centering the voice coil with no problems. I glued the surround to cone and let dry. This was easy since i had a pair of surrounds from Reedger which are designed for this woofer with the masonite (there are several discussions on these in the speakers section-using the search function in speakers takes some time but provides a wealth of pertinate info). I left the outer edge of the foam on top of the masonite. Then I turned over with face down and applied a liberal bead of glue to the masonite and spread with an art brush. Brush was helpful getting glue under the basket. Then turned over and put glue on outer edge of foam and spread lightly. Set for 4-5 minutes and then push surround under the masonite. Invert the woofer again and push down on cone ensuring the surround seats evenly. Gently press down with a smooth plastic handle (esp under the basket). Let set for drying. With the shim method I was not worried with a rubbing voice coil due to my turning over, etc. And it worked well.

For what it is worth and good luck.

Mike