• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

ADC 303a's have to be opened. How?

CUlater said:
I just noticed in the pic, they were only $15...you got ripped off! LOL... :D

Tough question. If you destroy the grille, the good news it making a replacement is pretty straightforward...and you can make it removeable for the future.

I have a pair of 303's and haven't had to open 'em up, thank goodness.

BTW, the 303ax was a fairly different beast altogether. IIRC, mine have a single 10" woofer and two tweeters in a different sized cabinet (and a velcro'ed on foam block grille).

Good luck, looking forward to hearing of your adventure (in case I ever need to get inside of mine!).
Click to expand...

Just for comparisons sake, here is a picture of my old ADC 303ax speakers. Note the removable cloth grill. What a difference a letter makes.
 

Attachments

  • ADC 303ax speakers.jpg
    ADC 303ax speakers.jpg
    121.1 KB · Views: 216
Ken, Broc and all- I'm sorry I wasn't very clear. I did disconnect the woofer from the crossover before testing it. When I free the woofer from the crossover the tweeter now works (and sounds equal to the other tweeter). A DMM attached to the woofer alone reads shorted. When the woofer is hooked back to the crossover as the tweeter is playing program material, the tweeter goes silent as the attachment of the woofer drags the signal down. I don't have a 9v battery handy, but I can guess the outcome. I had hoped that some "goop" on the back of the external terminal hookup screws was conductive and causing the short but, no such luck- the woofer appears to be at fault. Between all the "fiber fill" (I hope it's not asbestos) and the small hole obtained by removing the terminal plate, I can't get enough of my arm in there to do more than look, and feel, where the wires connect to the woofer- I can't feel the cone of the woofer. I can see that the woofer IS screwed in from the inside.

I wish I had Archie's removeable grills- I'd have these fixed already!

I've never had a speaker re-coned- I wonder if that's in order... The working cabinet does not appear to be overly efficient. Maybe new woofers are in order.
Brian
 
If the crossover on the 303a is anything like the one on the 303ax you may have a problem. Here is a pic of the crossover on my old 303ax taken through the woofer hole. I decided not to tackle that tar.
 
archie2 said:
If the crossover on the 303a is anything like the one on the 303ax you may have a problem. Here is a pic of the crossover on my old 303ax taken through the woofer hole. I decided not to tackle that tar.
Click to expand...

I'm not sure the picture worked- or maybe it's me. I'd love to see it though. There's a pair of those here in the office that need caps.
 
Hum. Anyone know the values of the caps? I've heard about this for a while and figured it's easy enough to leave the old caps in place and wire around them, but I don't know what the values are.

(edit)oh, and thanks for the pic!
 
I did a thorough search for the cap value but no luck. Also tried to deduce them from the crossover points, also no luck.
 
We're dragging this off topic. Should we start a new thread? Maybe between the three of us we can decifer what all the caps are. I can pull my woofers and see if anything is visible...
 
Not off topic as far as I'M concerned. The only problem I'M having is trying to remember who has the a's and who has the ax's. If I repair/replace this shorted woofer I am most likely going to rebuild the x-overs so all this info is pertinent to me.
 
Fast_Eddie said:
We're dragging this off topic. Should we start a new thread? Maybe between the three of us we can decifer what all the caps are. I can pull my woofers and see if anything is visible...
Click to expand...

I agree about the off topic direction, sorry for that. But I won't be much help on the cap values as I sold my 303ax's a few months ago. I just have the pics left.
 
I picked up a pair of 303AXs at the dump Sunday. A good friend used to own a pair when I first got into audio, and ADC has always been of interest to me, so was pleased to find them. The switches on one are balky, so I may have to go in to clean them, and will see if its possible to read cap values.
With regard to the poster who thought the 303AX had two tweeters, I think that was the 404 or 450.
If memory serves, ADC gooped the suspensions of both drivers in the 303AX with silicon, which damped out resonances, but also mean they always look like they are drooling, since the silicone migrates.
 
Looks like it's "ADC Month". I didn't even know ADC MADE speakers until I saw these at an estate sale. I can't wait to pull the woofer from my 303a and see that funky shaped dust cap and surround. Problem is right now I'm unemployed and I've mostly exhausted any possibility of fixing these for next to nothing. It's time to shell out some cold hard CASH- of which I have none :tears: I hate to dig in too deep with no money to finish the job.

Eddie and Archie, maybe you SHOULD start a new thread for info on cap values- you would probably kick up some new interest. As soon as I bust that lower cap out of the goop I'll let you know the value.
Brian
 
I may also start a thread on this since there is a 303ax crossover question somewhere else, but the values of the caps in mine are: Low pass: 16mfd 50V in parallel with the woofer, I assume to produce 12 db/octave slope, and unmarked value transformer used as the coil in series with woofer and cap. High Pass: resistor (green/blue/yellow or white/silver color code, but forgot to check value, and uncertain about colors) then two switched caps, a 6 mfd and a 16mfd, both I think 50V and then to the tweeter and to a paralleled ferrite core coil, again unmarked and again I assume to produce 12 db/octave slope. Mine had wax over stuff so not too hard to move the caps to see values, but colored the resistor.
It occurs to me that the resistor might be in series with the tweeter, but it was hard to tell because the switches were made air tight by covering up with masking tape and wax.
Hope this is helpful.
 
My 1971 Lafayett catalogue has a listing suggesting 10 watts/channel minimum power. By comparison, the AR 2 series is listed as needing 20 wpc, which I think would suggest the 303ax is 3 db more efficient. What's not clear is whether that power is RMS or IHF -- the listing for the KLH 6 specifies 25 watts IHF, which, I think, corresponds to 12.5 RMS. The 6s are fairly efficient for an acoustic suspension design, but this suggests that the 303axs are even a bit more efficient.
 
Out of curiosity, I googles efficiency of AR 2ax and up pops a Peter Mitchell article in BAS (Boston Audio Society) with a list of efficiencies -- AR 2ax 82 db/watt and ADC 303ax 85 db/watt. They also list the 303A (83db/watt) and 303B (86 db/watt). I've never heard of the 303B, so this was interesting.
 
Fast_Eddie said:
The grilles won't come off. Ever. Not without destroying them. You have to cut the back off.
Click to expand...

(ADC303a)

For starters, I'm the guy who bought Archie's 303ax's. I've been doing a little tweaking and will report back.

For now, I'd like to comment on the 'permanent' grilles on the 303a. I more recently picked up a pair of 303b's. (What, you never heard of them?) Unlike the removeable grilles on the ax, the grilles on the 303b wouldn't budge. I decided they were going to come off anyway. I took a 2-and-a-half-inch wide chisel and carefully worked it into the small gap between the grille and the edge of the cabinet, and pried gently..... kept doing that up and down both sides, and eventually that grille began to lift, and eventually came off.

It turned out, the grille was held on with copious amounts of the same black tar that has been cited on some of ADC's crossover boards.

I think the reason I succeeded was dumb luck.... I was doing it out in the sun on a hot day, and as the grilles soaked up the rays, that tar softened a bit.

So I'm just thinking that the grilles on the 303a's might be attached the same way.
 
Nat said:
I picked up a pair of 303AXs at the dump Sunday...........
........With regard to the poster who thought the 303AX had two tweeters, I think that was the 404 or 450.
Click to expand...

Some guys have all the luck.
404's were a small, 6.5" two-way with one tweeter.
450's were a 12" two-way, again with one tweeter.
The model with two tweeters was the XT-10, a 10" two-way. The drivers appeared to be the same as those used in the 303ax.
 
You must log in or register to reply here.
Back
Top Bottom