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

I just found this pair of ADC 303a at an estate sale for $20. I've looked at a lot of posts in AK about these speakers. Apparently the older 303a's like these are 8" woofers and there were later 303ax's which were 10", not to mention other differences. It appears one of my cabinets "works" (I didn't 'extensively' test it) and the other measures a dead short across the speaker terminals. They're coming open- I'm just trying to figure out the best way to do it. The grills are not coming off- and I don't want to tear them up. It sounds like the drivers are mounted from the inside, anyway. (6/23/19 Edit: The woofer is mounted from the rear. The tweeter is mounted from the front.)

In a post about 3 years ago, Philliam (PT) says that he opened the backs of 303ax's by cutting 1-1/8" inside around the outside edge of the box. I would really like to see photos of this, or any other repairs you guys have made on this model, or any other speaker that wouldn't open by civilized methods.

I've also had someone else tell me they would also cut the entire back out, but at 3/4" around the edge- the same dimension as the thickness of the wood. Then, before putting the same backs back on, install bracing around the inside and re-install the backs onto the bracing with 'cabinet putty' and screws after repairs were complete.

What do you think my best options are?
Brian

I think cutting the back off the way you describe would ruin the original quality of the speakers. That may not be important to you. Chances are, those grilles are your most likely method of entry. If you're careful, you probably won't damage them significantly. Take a thin butter knife, bend the tip 90 degrees in a vice and see if you can pry off the grille. It may be stapled on. If the woofer is mounted from the rear, you can always take out the mid if there is one, or the tweeter to access the inside of the cabinet. It is possible that the front baffle will come off easier than the back. That has occurred with a couple of speaker boxes I have dismantled.

I have a pair of those and all the research that I've done points to the router to the back method. Mine sound ok so I've never had to go inside.

YMMV, Steve

Sealy- I know what you mean about the loss in value for cutting open the backs. It pains me to have to do it that way. But from what I'm reading on the net I'm just going to screw up the grills trying to remove them and then I can't be assured that I can remove the drivers from the front. At least by cutting open the backs the patch job won't be evident in normal use from the front. These are for my personal use so resale value is not an issue with me.

Steve- How do YOURS sound? I really haven't had a chance to hear mine- I've read that someone holds the 303ax (with 10" woofers) in as high regards as AR-2's.

So, guys, the question is what is the best way to cut them open with the least damage and reduce the amount of work involved to seal them back up. Looking at this image, would you cut along the red, blue or green lines? The green lines are about a 10" square- ample in size to remove fiber fill and an 8" woofer if need be.



Thank you for your help!
Brian

The grilles won't come off. Ever. Not without destroying them. You have to cut the back off.

It looks like there are 4 bolts holding the woofer on, if my eyes aren't deceiving me. That probably means the woofers are affixed from the inside. It could also mean the front baffle is screwed on, and could be removed. All speculation, though. Too bad about the grilles.

Blast said:

I just found this pair of ADC 303a at an estate sale for $20. ...<snip>

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

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!).

Steve- How do YOURS sound? I really haven't had a chance to hear mine- I've read that someone holds the 303ax (with 10" woofers) in as high regards as AR-2's.

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Haven't listened to them in about a year.
From what I remember they were pretty descent sounding.
I've never heard Ar2's but I had a set of AR2a's and would say that they are similar.

If you decide to cut on the green line I would move it up an inch +/- to make sure that I didn't screw up the plate with the switches and maybe Xover.
( Pure speculation on my part).
Red line would be the way to go if there is no corner bead / brace .. whatever you want to call it.
As a buddy of mine says "Hard Telling .. not Knowing".
Steve

Can you shine a flashlight thru the grille and see whether the drivers are front or rear mounted? If rear mounted (a common practice back then) there won't be any point in removing the front grille. The front is more than likely dadoed into place like the rear panel.

I agree fixing/creating new grills is a lot easier and less risky than cutting open the back.

CUlater said:

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

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...

Strange, I also had a pair of 303ax's bought new in 1972 but recently sold. They had a 10" woofer and a single cone tweeter each, no two tweeters. The grill was tarred on and was cloth, not foam. Were there more than 1 version of the 303ax?

CUlater said:

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

---snip---

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

Click to expand...

You funny guy! Actually if you look on the backs there's a "10--" on each one. That was the direction I faced the cabinets towards the cashier when I took them up to pay for them. I didn't even SEE the "15--"s on the fronts (of BOTH) before I got them home. Really... I was too absorbed in that sparkle grill cloth!

Yes, sealy, the 4 marks on the grill appear to be someone's skin oil as they felt around for screws. That's not even the bad cabinet. The bad cabinet has it's back to us and has an even cleaner grill.

Celt, I shined a flashlight in as you asked. The only things I can see are what's further back in the depths of the drivers like the irregular shaped dust cap- WEIRD- if I take this woofer out wait until you see it! Maybe that's the Frequency Discriminating Decoupling part of the woofer they call it on the label. The grill cloth is so heavy you can barely see through it. You can't see anything near the surface like screws or the front edge of the cone. The tweeter appears to have a shiny dust cap like a dome. It's like driving in thick fog trying to look through that cloth!

I just hooked up the one that works. It has EXCELLENT smooth bass/mid but has very little emitting from the tweeter. It doesn't appear to be a really efficient speaker- I had to hit it hard- maybe that's the crossover, too. Of course, I'm not EVEN hooking up the one that reads shorted.

I'm up to 90% sure I'm going in the backs (sorry you 'front guys' but I appreciate your opinion!). I'm basing my decision on everyone's help here, and my own abilities. I don't EVEN want to see defects or anything different about the grills when/if these are sitting in my living room. I don't care what the backs look like as long as the labels remain and they hold air like a tire. 2 people have said that the drivers are installed from the rear, anyways. I can't see any point of removing the grills if that's the case. I'm about 50% sure that I will utilize the green line (see photo), however, I'm going an inch (thanks, Steve) LOWER than the jack plate (rather than above it). That way I don't disturb the label if it's the 8" driver that's shorted I can check it & remove it from there. If it's NOT the driver (are SHORTED voice coils as common as OPEN ones?) and I need to access the crossover I can extend the cut up to the entire green line as shown and pull the crossover/jack plate out.

At the point of re-assembly I can determine whether or not to put a surface mount board over the back hole (with a gasket) or put bracing around the inside of the hole and flush mount a new board. Or maybe upon further inspection I could completely replace the whole back.

I'll post as I go with some nudie photos. Thank you ALL for your help!

i Had a pair of Both the303 A's and the AX's and if your just wanting to get at the crossovers.... that silver plate you see with the two switches is also part of the crossover and that plate is only held on with/by metal staples.. i used a flat piece of wood about 2 &1/2 wide by 3/4 thick about 6 inches long and a small finishing hammer and started tapping my way around the plate untill i worked the staples loose . letting the plate fall inside the speaker cab , i then took a jig saw , i cut the square hole just an inch or so bigger , pulled the crossovers out the hole recapped them and took some scrap 3/4 inch thick particle board routed out the new hole for the crossover plate & cut them to the new size hole about 4 1/8 x 4 1/8 x 3/4 square block & with some clear sillicone and 6 short wood screws attached the crossover on to the back side of the wooden block (dry fitted it a couple times to make sure the fit nice) then . and resealed them back in place with some wood glue around the eddges of the block and tapped them in with a larger peice of wood over them to make sure the fit flush with the cab when setting them . i saved some of the saw dust from cutting the blocks. rubbed in the saw dust between and gaps or seams and let dry a couple two hours or so , hand sanded any burrs and the seems down and took some dark stain and dab stained just the wooden block untill disired darkness . it looked real nice when done you would of had to look pretty close to see any change of wood pattern or materials used . hope this helps

Try using the flash on your digital camera to
get a pic through the grille cloth.

Might surprise ya what you'll see........

kenhappen2u said:

i Had a pair of Both the303 A's and the AX's and if your just wanting to get at the crossovers.... that silver plate you see with the two switches is also part of the crossover and that plate is only held on with/by metal staples.. i used a flat piece of wood about 2 &1/2 wide by 3/4 thick about 6 inches long and a small finishing hammer and started tapping my way around the plate untill i worked the staples loose . letting the plate fall inside the speaker cab , i then took a jig saw , i cut the square hole just an inch or so bigger , pulled the crossovers out the hole recapped them and took some scrap 3/4 inch thick particle board routed out the new hole for the crossover plate & cut them to the new size hole about 4 1/8 x 4 1/8 x 3/4 square block & with some clear sillicone and 6 short wood screws attached the crossover on to the back side of the wooden block (dry fitted it a couple times to make sure the fit nice) then . and resealed them back in place with some wood glue around the eddges of the block and tapped them in with a larger peice of wood over them to make sure the fit flush with the cab when setting them . i saved some of the saw dust from cutting the blocks. rubbed in the saw dust between and gaps or seams and let dry a couple two hours or so , hand sanded any burrs and the seems down and took some dark stain and dab stained just the wooden block untill disired darkness . it looked real nice when done you would of had to look pretty close to see any change of wood pattern or materials used . hope this helps

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Well, now, this changes everything. Did you do that to BOTH your a's and ax's, or just one of them? Maybe the crossover is the only thing I NEED to get to- I've never seen a speaker short out before. Hard for me to imagine one doing it.

Captain Scary said:

Try using the flash on your digital camera to
get a pic through the grille cloth.

Might surprise ya what you'll see........

Click to expand...

I tried that but my bottom-of-the-line camera can only see the cloth- even on macro setting. There's is a scientific name for the shape of the dust cap which escapes me but I'm going to say it looks like a cul-de-sac lot on a plat map. The surround is shaped the same and appears to follow the cap- no two sides are the same length.

Blast said:

Well, now, this changes everything. Did you do that to BOTH your a's and ax's, or just one of them? Maybe the crossover is the only thing I NEED to get to- I've never seen a speaker short out before. Hard for me to imagine one doing it.

Click to expand...

i did it to a pair of the 303 ax's, now on the pair of A's i had to replaced the crossovers with store bought ones (parts express) and replaced that silver plate with a cup (circle) and new bannana plug terminals, the crossovers i used were not an exact match to the old ones so im sure they didnt sound the same but it did get them working again ...it was my first attempt to replace the old crossovers and i prolly shouldnt have picked a speaker that the grills did not come off and no access to the speakers as my first rebuild project ... this is how i found out that the silver crossover plates were held on by staples , i pretty much destroyed one of the silver plate on my first attempt useing some rather crude tools like a butter knife and a mini 6 inch crow bar, screwdriver etc .....not the tools for speaker repair or wood working .

I popped the terminal plate in on the shorted speaker and determined it is actually the woofer which is shorted. I see crossovers could stand to be rebuilt and switches replaced. Ken, mine looked like it was held in with toothpicks! This will be the first shorted woofer I've ever seen (but I don't get out much). I think the next step is to cut the hole on the green line and extract the driver for further analysis.

To jump ahead- if I was to get the driver reconed, would it sound substantially different than the other original driver that still works?



Brian

Brian.....how did you test the woofer ? did you disconnect it completely from the crossover ? try to test it with a 9volt battery

Disconnect woofer from X-Over and drive it with small signal from receiver by itself. Should not rattle or buzz. Should just sound low and rolled off for the highs? If it does not work, or has rubbing, buzzing sounds, it'll need service. If it sounds clean, the X-Over is the issue.