Newly Acquired AR-7's

[Rich W]

Just got a pair of AR-7 speakers from a yard sale for at $5. The cabinets, albeit clad in vinyl, are in very good condition, the muslin grill fabric is original and clean, even the logo plates look good. Best of all, all the drivers are operational. Obviously, a refoam will be in order, as there was nothing left but a few fossilized pieces of surround dangling from the woofer!

Just need some advice on caps for these units. The print has rubbed off each cap and I can't visually determine what the value should be. I used my DMM and measured them at 7.1 uf and 7.3 uf respectively. Shouldn't they be closer to 6 uf, similar to the AR18?

If the correct value is in fact 6 uf, I have a another set of Solen 6.2 uf caps which worked very well in my recently refurbished AR18's. It seems they should work equally well in the AR7's. However, I recapped a pair of AR18S's (whose cap value is 5 uf) with a set of Solens, and was not satisfied with the result - the speaker seamed too bright (who knows - maybe that's how it was voiced originally).

Obviously, I don't want to make any mistakes with so valuable a vintage speakers as the AR7, so any advice would be appreciated. Perhaps I should leave the caps "as is".

Thanks and best regards to all,

Rich W

[Guest hilltroll67]

I can't help you with cap values, but have to ask: what do you suppose wiped off the values on the originals? I can't picture the circumstance.

Bob

[Rich W]

Bob, both capacitors were mounted "face down" in the hot glue. When I pulled them away, the plastic coating peeled off the cap and remained attached to the glue. Just my luck that both caps had done so!

Best Regards,

Rich W

[tysontom]

>Just got a pair of AR-7 speakers from a yard sale for at $5.

>The cabinets, albeit clad in vinyl, are in very good

>condition, the muslin grill fabric is original and clean, even

>the logo plates look good. Best of all, all the drivers are

>operational. Obviously, a refoam will be in order, as there

>was nothing left but a few fossilized pieces of surround

>dangling from the woofer!

>

>Just need some advice on caps for these units. The print has

>rubbed off each cap and I can't visually determine what the

>value should be. I used my DMM and measured them at 7.1 uf

>and 7.3 uf respectively. Shouldn't they be closer to 6 uf,

>similar to the AR18?

>

>If the correct value is in fact 6 uf, I have a another set of

>Solen 6.2 uf caps which worked very well in my recently

>refurbished AR18's. It seems they should work equally well in

>the AR7's. However, I recapped a pair of AR18S's (whose cap

>value is 5 uf) with a set of Solens, and was not satisfied

>with the result - the speaker seamed too bright (who knows -

>maybe that's how it was voiced originally).

>

>Obviously, I don't want to make any mistakes with so valuable

>a vintage speakers as the AR7, so any advice would be

>appreciated. Perhaps I should leave the caps "as

>is".

>

>Thanks and best regards to all,

>

>Rich W

>

Rich,

The capacitor for the AR-7 was a 6 mfd, 50V NP sized unit.

--Tom Tyson

[Rich W]

Thanks, Tom

I noticed after I posted this thread (in an archive search) that you had mentioned the 6uF cap for the AR-7, and also the fact that its surround has a smaller roll diameter than later 8" woofers. With all the comparisons I did to find the perfect surround replacements for my AR18 (see my next post), I do have a pair with the smaller roll diameter, which I intend to use for the AR7's.

Thanks again,

Rich W

[Guest dishbert]

Hey guys, I was just thinking of rebuilding my AR-7's and found this great forum with Google.

The only think I can see that's wrong with them is the foam surrounding the woofers. I found a site on ebay that sells EdgeKits, but they don't seem to list that model.

Where do you get yours?

dishbert

[JKent]

My favorite refoam supplier is M_Sound. He gives you the surrounds, shims, dust caps, glue, brushes, swabs, alcohol wipes, excellent directions and email support. I've tried others but will always go back to M_Sound

http://www.citlink.net/~msound/

Kent

[Rich W]

Hi Dishbert,

The AR-7 uses a surround with a smaller roll diameter than some of the later generation 8" models (such as the AR-18).

For my AR-7s, I used the surrounds from Larry at Vintage AR (see "links" area of this website). You'll also see them show up on Ebay.

Best Regards,

Rich W

[Guest dishbert]

Thanks for the info, sorry for the late reply, I got involved with other projects.

While I'm waiting for my supplies to fix the surround, is there any thing else I should be checking while I have the boxes open?

[Rich W]

Hi Dishbert,

I've just completed restoring my AR-7's and I am very happy with the results. Below are some other things I would check while the cabinets of your AR-7's are open. It's helpful the have a good Digital Multimeter to check capacitor and resistor values, but if you don't, you can't go wrong by changing the caps and leaving the resistor alone (resistor values generally stay stable over time).

- Capacitors. The values of mine were off, probably from age (see my original post above). I replaced mine with Solens 6.2 uF 400v available from Parts Express. The original spec calls for a 6 uF cap, but the 6.2 will work fine with no discernable difference in sound. Cut the leads of the old caps, and solder the new ones in place. Glue to back of cabinet with GE silicon glue, rather than hot glue.

- 3 Watt resistor for tweeter level. Replace if you notice any swelling. If you do replace, do not glue to back of cabinet, as the resistor needs some air around it to cool (that's why some originals go south in the first place).

- Clean the level switch by spraying some Caig's De-oxit into the switch and toggling it back and forth to work the cleaner in. You'll have to do this from the outside, as the entire switch is encased in a plastic substance on the inside, no doubt to maintain a good acoustic seal.

- Cabinet seal. To maintain proper bass response, it is extremely important that the seal around the woofer be air-tight. Do not reuse the original foam seal, as it has already been compressed from use. You'll see a number of posts on this website suggesting different sealant types. Mortite rope caulk works good for the larger AR woofers, but for the smaller 8" woofers, I prefer Hercules "Sta Put" Plummers Putty, as it is more pliable and less likely to bend the frame of the smaller woofer. I can't stress enough the importance of a good woofer-to-cabinet seal, and I can attest from personal experience that even the smallest leak will degrade bass performance.

That's about it. As unbelieveable as it sounds, these speakers are capable of producing an output at 32 hz (sub-contra C on a church organ - an extremely low bass note), albeit at a reduced level vs. its larger AR siblings. They, along with its successor, the AR-18, are the finest small speakers I have ever heard, and IMO are far smoother and natural sounding (particularly in the lower treble region) than the highly venerated Large Advent speaker (which I once owned). Of course, the Advent surpasses the modest AR-7 in the lowest bass octave and ability the play at extremely loud levels.

Enjoy the restoral process (it's a great thing to do to relax), and enjoy listening to these superb speakers when you're done.

Best Regards,

Rich W