AR4X Speakers rebuild - some questions

[Guest graham]

Hi All,

I recently acquired a pair of AR4X from an auction for $10. One was working, on the other the tweeter was silent. I acquired 3 tweeters from ebay, however I think they may be mid-ranges.

So question 1 - from the photos attached can you identify the age/model of the original tweeters one of which has Jan 28 1969 on the back. Can you identify the model/make of my proposed replacement tweeters which have 5803028 137 524 1405 on the back, and a grill with a foam pad underneath, on the front. Are they suitable replacements? they are the same size, are they tweeters?

Question 2. Why are the woofers different colors? I attach photos of the rear and front. The Brown paper woofer on the left has sticky brown paper sealing the sides at the rear with the marking Jan 31 1969. The Black Paper woofer has black material sealing the sides at the rear, and the marking 4X 2748 137 6903D. The Case with the black woofer has serial FX227334 on the back, the Case with the brown speaker has had the serial paperwork torn off.

Question 3. Is there any way to get the non-working tweeter working.? I connect speaker wires to it, it is dead, the other works.

Question 4. Are the two tweeters with the grills actually tweeters or mid-ranges, and will they work as replacements for both of the original tweeters. Can I solder this all together and get a working pair of speakers?

All advice and information welcome.

Graham

[ar_pro]

Graham -

The drivers with the grills & foam are AR-2ax midranges - they're not suitable replacements for the AR-4 tweeter.

[dynaco_dan]

Hi there;

The lower two are AR-2AX midranges and also AR-4 tweeters.

The AR-4 and AR-4X have different crossover points, but otherwise, can be used if you want to experiment with the earlier AR-4 sound.

I do not know the crossover differences.

[johnieo]

>Hi All,

> I recently acquired a pair of AR4X from an auction for

>$10. One was working, on the other the tweeter was silent. I

>acquired 3 tweeters from ebay, however I think they may be

>mid-ranges.

>So question 1 - from the photos attached can you identify the

>age/model of the original tweeters one of which has Jan 28

>1969 on the back.

Hi Graham:

The 28 Jan 1969 driver is an AR-4x tweet. I think I saw the two with the front grille covers incorrectly advertised on Ebay as AR-4x tweets they--as others have told you--are not. They were used in the AR-4 (and 2x); they are not suitable for the 4x as their crossover frequency is too high.

The AR-4x tweet dated 28 Jan 69 should solve your problem. The crossover for the AR-4x was originally 1,400 Hz (early serial numbers with a #4 woofer inductor). Later drivers used the #5 coil---the crossover was reduced slightly to 1,200 Hz. Early #4 inductors were marked with the number 200 written in magic marker, meaning 200 turns of wire. Early units used 16-18 oz. of fiberglass stuffing, whereas the weight was reduced to 12 oz in units using the #5 coil.

When removing the stuffing, it is desireable to collect the material from each cabinet in a separate paper bag and weigh the contents. 'tis dusty stuff, so best to use latex gloves and work outside or in a well-vented area.

The reason for going into this detail is simply to comment that you would be best served with a matched pair. That is, the same woofer inductor and stuffing weight in both cabinets. If they are both the same, no changes are necessary.

If your coils are not the same (one each size) you might consider increasing the number of turns on the smaller coil. I can provide the gory details off-line.

While you have the cabinets open, you might consider cleaning the potentiometer surfaces--lots of material posted on this site, just use the search command for cleaning potentiometers.

Also, consider replacing the 37-year-old 20-uF capacitors with good quality prolypropylene capacitors. They are likely out of specification. A simple capacitance meter is not sufficient to tell if they are good. A common failure causes their series resistance to increase significantly. This will show up on an inexpensive capacitance meter as a higher capacitance, but within the nominal +/- 10% tolerance.

>Question 2. Why are the woofers different colors? I attach

>photos of the rear and front. The Brown paper woofer on the

>left has sticky brown paper sealing the sides at the rear with

>the marking Jan 31 1969. The Black Paper woofer has black

>material sealing the sides at the rear, and the marking 4X

>2748 137 6903D. The Case with the black woofer has serial

>FX227334 on the back, the Case with the brown speaker has had

>the serial paperwork torn off.

Both smooth-cone and ribbed-cone woofers were used interchangably. There appears to be no clear pattern of woofer type and serial number sequence. Both were used in early serial numbers, both in later serial numbers. AR did change cone designs to improve performance; perhaps Tom Tyson would care to comment on the differences. Personally, I cannot hear the differences- even in mismatched pairs.

>Question 3. Is there any way to get the non-working tweeter

>working.? I connect speaker wires to it, it is dead, the other

>works.

First, you must determine if the tweeter is <> dead, or if the potentiometer is corroded. Try wiggling the potentiometer, if you get no sound at all, then disconnect the tweeter and check it with an ohmmeter. Its resistance is in the range 4.2-to-4.8 Ohms. If the unit is open, then use it for a paperweight. Many AR-4x sold with tweeters turn out to have corroded potentiometers that only need a good cleaning.

>Question 4. Are the two tweeters with the grills actually

>tweeters or mid-ranges, and will they work as replacements for

>both of the original tweeters.

As earlier responders stated, unfortunately not.

>Can I solder this all together

>and get a working pair of speakers?

Certainly! Take your time and work carefully. If you run into any sticky details, send me an e-mail. You will be astounded at how nicely the AR-4x sounds, proud of your accomplishment, and understand why it was so popular. Go for it!

[Guest graham]

Hi John,

thanks to you and the others for your response.

>

>The 28 Jan 1969 driver is an AR-4x tweet. I think I saw the

>two with the front grille covers incorrectly advertised on

>Ebay as AR-4x tweets they--as others have told you--are not.

>They were used in the AR-4 (and 2x); they are not suitable for

>the 4x as their crossover frequency is too high.

Damm, you probably saw the ones I got. There were 3 of them in the lot, only 2 in the photo. So I now have 3 x 2AX midranges. that are no use for the purpose I intended. They all work, I guess I will put them back on ebay, unless anyone here wants to make me an offer, or wants to trade for a single AR4x tweeter.

>

>The AR-4x tweet dated 28 Jan 69 should solve your problem.

Not really, thats the only one I have that works. The two AR4x tweeters in the photo were the ones I just removed. One works the other doesn't.

>Later drivers used the #5

>coil---the crossover was reduced slightly to 1,200 Hz. Early

>#4 inductors were marked with the number 200 written in magic

>marker, meaning 200 turns of wire.

>If your coils are not the same (one each size) you might

>consider increasing the number of turns on the smaller coil.

Both coils in these have a very rough '5' handwritten in magic marker on the top. So I assume they are the later 1,200 Hz models.

And they both look identical.

>While you have the cabinets open, you might consider cleaning

>the potentiometer surfaces-

Done, there was a bit of green inside them, I used 1000 gauge steel wool, put them back together with the original puttee over the wire, the seem ok.

->

>Also, consider replacing the 37-year-old 20-uF capacitors with

>good quality prolypropylene capacitors. They are likely out of

>specification.

Ok I will check out prices of replacements.

>First, you must determine if the tweeter is

><> dead,

I connected live speaker wires directly to the disconnected tweeters, one played music, the other didn't. The potentiometer was not in the way of this test.

>disconnect the tweeter and check it with an

>ohmmeter. Its resistance is in the range 4.2-to-4.8 Ohms. If

>the unit is open, then use it for a paperweight.

Damm, the paper is in good shape, what can be wrong with it? Unfortunatly all is sealed up, and no way to open. oh well, I guess I am back to scanning ebay for a single replacement AR4x tweeter.

Graham