To Dope or NOT

[Grid]

I have a Utah A-100 12" 3-way with horn and tweeter system. The woofers have cloth surrounds. I purchased the doping stuff but a member has brought to my attention that it is possible that although AR and KLH doped the cloth surrounds, that doesn't mean Utah doped their cloth surrounds.

Were all speaker manufacturer's cloth surrounds doped?

I have the new caps, too, and would like to install them but I don't want to do anything that would alter the stock sound. And I'm also unsure, is the dope applied to the entire cloth or just the edges that meet the paper.

Thank you.

 

[60 Cycle Hum]

If the cabinets are ported (not sealed) then doping is likely not useful.

 

[N8Nagel]

I remember you asking. The answer above is correct. Now they may have treated the surround as a port, that would be odd but it could happen. It is good you asked and I don't have that answer. Can you tell by inspection if it looks like there was ever any kind of butyl coating on the cloth?

 

[Grid]

If the cabinets are ported (not sealed) then doping is likely not useful.

Sealed Acoustic Suspension. Sorry, I should have noted that. Thank you.

 

[Grid]

I remember you asking. The answer above is correct. Now they may have treated the surround as a port, that would be odd but it could happen. It is good you asked and I don't have that answer. Can you tell by inspection if it looks like there was ever any kind of butyl coating on the cloth?

You know, I kinda think so! If I gently run a finger around the surround, it does seem to give off a sandy kind of dust. I'm thinking that may be the dried butyl?

 

[N8Nagel]

Is there a model number on the driver and/or cabinet?

I'm pretty convinced that butyl is appropriate on your drivers, but I don't have the knowledge to say it with authority.

 

[Grid]

Is there a model number on the driver and/or cabinet?

I'm pretty convinced that butyl is appropriate on your drivers, but I don't have the knowledge to say it with authority.

Sure is. But info is hard to come by.

 

[N8Nagel]

Well if the manufacturer called them acoustic suspension, that's another argument for doping.

 

[Katalyst]

If you do dope the surrounds,only do one.Then you can a/b and tell if it helped.

 

[Grid]

Well if the manufacturer called them acoustic suspension, that's another argument for doping.

I just read an article at Vintage Assylum by member DavidLD. He refers to the surrounds as "cloth roll." I have e-mailed him.

 

[Grid]

If you do dope the surrounds,only do one.Then you can a/b and tell if it helped.

Thank you. But that scares me. What if the undoped one sounds better?

 

[N8Nagel]

I doubt that'll happen. But the carrier is toluene so you could try that to remove it. It never really sets up or polymerizes so it should be possible.

 

[Grid]

I doubt that'll happen. But the carrier is toluene so you could try that to remove it. It never really sets up or polymerizes so it should be possible.

I don't know. Seems a lot of stressing that cloth. That's all I'd need is to put a hole in it form too much messin' with the cloth. With my luck the toluene would travel to the paper cones. I'm about to put the new caps in. If it sounds great maybe I'll leave it be until / if ever I know for sure Utah doped the cloth in the first place. Thing is, the dope I guess is good for only a year.

 

[N8Nagel]

I think if it gets too thick you can cut it with toluene. But I have to admit I'm pretty convinced that they should be doped.

 

[Grid]

I think if it gets too thick you can cut it with toluene. But I have to admit I'm pretty convinced that they should be doped.

Well, right now this is close to a scrapped project. Disaster happened. This is what happens when you don't have room to work and you live in a shoe box apartment and you FORCE a job you know you don't have room to do. I nicely recapped one. But then, long story short, the rear board the crossover is mounted to fell and it took the leads to the tweeter with it. The whole freakin' tweeter is housed in metal. I'm up shit's creek and ready to toss these both in the dumpster. Or maybe I'll pour that dope shit all over them and set them aflame. I'm so upset and angry that I'm in tears!

 

[Archguy]

36w Peak Power Handling. Those were the days!
Now why are they called Utah if they're from Indiana?
Another vote for doping. I just like doping. Adds durability.

Never even heard of these before. Learn something new every day!

 

[Grid]

36w Peak Power Handling. Those were the days!
Now why are they called Utah if they're from Indiana?
Another vote for doping. I just like doping. Adds durability. Never even heard of these before. Learn something new every day!

My first speaker was a Utah Dad gave me. Utah started in 1929 in Salt Lake City and Chicago. Later moved to Huntington. My Avatar is a rare Utah I have that sounds sweet. Been looking years for a mate to it. Here it is in a Utah catalog:

 

[gdmoore28]

Well, right now this is close to a scrapped project. Disaster happened.

Don't despair. If human hands assembled those components, then human hands can repair them. Time to step back, take a deep breath, and regroup. Once you've regained your composure, post some detailed pics and we'll try to find a way to repair your speaker. Some how or another, it can be repaired.

GeeDeeEmm

 

[Grid]

Don't despair. If human hands assembled those components, then human hands can repair them. Time to step back, take a deep breath, and regroup. Once you've regained your composure, post some detailed pics and we'll try to find a way to repair your speaker. Some how or another, it can be repaired.

GeeDeeEmm

Thank you for the reassuring words. Yeah, I slept on it. Thinking more clearly today. The garbage truck came at 8 AM but thankfully I was still in bed. Oh, wait, I don't mean I would have let them take ME, I was considering how satisfying it would have been to look out the window and see those speakers get compacted into the garbage truck. See that, I smiled; must be feeling better.

OK, I will take detailed photos and post shortly. Here's my situation since I cried about the tweeter. A very nice, hard working eBay seller, who has a pair of these same speakers but out of the enclosures went to the trouble of individually photographing the speakers for me, and he accepted my $50 offer. So I figure I can take what I need and part out cheaply on eBay to recoup.

But by all means, I want to save the life of that perfectly good tweeter. 50 years old and working fine, and I gotta kill it! When I post photos, I'll share an idea I have. Basically, I located the thin bare wire that goes to the heart of the speaker, and I carefully brought it out of the hole. When I touched the leads that go to the crossover, the speaker played. So if I can gently solder it to the crossover wires, it'll live. BUT here's the bastard of it all: There is a insulating washer that broke off and is too big to come out the hole. We can't have that rattling around in there.

 

[Grid]

Thank you all for your insights on redoping. I now believe these Utah cloth surrounds were originally sealed. Take a lot at the photo, which I think makes that evident. On one woofer, you can see that it looks like the sealant dried away, when compared to another woofer that still has an intact coating on the surrounds. Thus I have to conclude Utah cloth surrounds were originally doped. The stuff comes Monday. I will redope.