1966 H-700

[JohnA]

I picked up a really nice 1966 H-700. It is in fabulous shape, not looking its 40 years, at all.

It sounds bassy and not quite right. Does anybody have the Type C

schematic so I can check to see if it's been modified?

The squawker cap has 4 terminals and it's labeled 1.0 uF x 2.

Only 2 of the terminals are used. What do I have there?

[JohnA]

The 1.0 x 2 cap is the one on the left.

[Erik Mandaville]

I'm working on this now, too -- with the same model Heresy. What taps are being used on the squawker? Try moving

[Erik Mandaville]

Ooops....

John: I meant to say that both autoformer taps to the squawker were on the highest attenuation setting, and I was not getting a good balance between the drivers. Both midrange and tweeter were moved up one tap, and things sound much better. The motor run caps I got appeared to be in good shape, but I'm trying the speakers today with some poly caps from Mouser. Grainger doesn't appear to stock the GE motor run caps anymore. I have also been using the original tweeter for the past couple of weeks, and am going to try them this afternoon with a pair of K77Ms.

BTW: The value of capacitance for the input to the autoformer on this pair was 1uf.

I'm going to test the original capacitors later this weekend. I'm trying to squeeze all this in among class preparation for next week, but it's fun!

Also: I have reconfigured the output transformers for my amp (Moth 2A3) for the 16 ohm output, which really seems to work much better.

Erik

[Deang]

That's a 16 ohm woofer John. Going through the archives it looks like it's probably an Electrovoice SP12B. This means 3dB more down on the K-77 and K-55 than we see with the Type E network. So, 240 ohms or slightly more of reflected impedance back to the amp puts the primary cap at 1uF for 700Hz. The tweeter cap would be the same 2uF we always see. I wouldn't waste my time trying to figure out if it's been modified or not, I would just tear it down and rebuild it. Since you know more about this stuff than half of us out here -- I can't figure out for the life of me why you posted this!

[JohnA]

Dean,

If this one ever ends up in my HT (as rear center) I'll rebuild the

crossover to match the others. However, it is now destined for an

period authentic mono system powered by a Heathkit EA-3. So, I

want it to be entirely original. The fly in "authentic" will be

the mini-CD player source. []

This is the same system I started to build for my M-i-L using a

Shorthorn so she'd have something to listen to Big Band on. She

enjoys that music and should have more of that since my F-i-L

died. Cathy talked me out of it saying she wouldn't use it, but

I've never given up on build such a little rig.

Eric,

It would appear my crossover is configured exactly like yours, with

only half of the 1.0 x 2 cap in use and thus 1.0 uF on the autoformer

input. I don't like it. The bass and mids are strong and

the treble is weak. For the test it was sitting on the floof

about 3' out of the corner (amidst the clutter). Not at all what

a Klipsch normally sounds like to me.

Anybody know what the SP12B efficiency rating is, or how to convert RETMA 46.5 dB to dB/w/m?

[Malcolm]

1 uF and 2 uF is correct for what you have. The autotransformer taps used are different than on the later D, E and E2 networks. I wouldn't worry about the fact that you have dual section caps. They could be original. Klipsch used just about anything they could get at the time when it came to Heresy caps. It almost looks like they used a lot of surplus stuff. OTOH changing them out with decent new caps certainly wouldn't. What you are hearing could be due to the caps not being in spec anymore. I have a mix of Heresys from the mid sixties to the late seventies and I don't here a difference. But then your hearing may be better than mine.

Clipped from an old audioasylum thread:

"EIA is 1mW at 30ft, add 30dB for 1W, add 19.216dB for 1M"

46.5 + 30 + 19.2 = 95.7

[JohnA]

If the woofer is just under 96 db/w/m, then the trouble MUST be the

caps. Al of the drivers work, but the tweeter, in particular, has

very little output.

[Erik Mandaville]

John:

I wanted to keep these 100% original, too, but truly found very much the same sort of response you describe. A closer look at both caps this morning revealed what appeared to be a sort of petrified-like oil or lacquer around the the terminals, which wasn't simply solder rosin. I wanted to use replacement GE caps such as those Bob offers with his networks (or used to) but found the Grainger just down the road from us doesn't stock them any more. I should have bought a bunch of useful values when they had them.

The insides of these are really pristine, but I suspect as you (and as Malcom suggest) that cap refreshing was in order. I'm about to put the one remaining network back inside and get things going.

The replacement capacitors or metallized poly things from Mouser. They are white, and I turned them upside down so I can pretend they are some exotic brand.

I'll let you know what I find.

Erik

[Deang]

John -- well, the caps are at least 40 years old. Consider also that they might have been made towards the end of WWII -- and might be much older.

[Erik Mandaville]

John:

Much, much, much better with both capactors replaced. I can actually hear the tweeters now, but I do like the K77Ms better -- just as I did with the K-horns, which now have Bob's replacements.

The autoformer changes last week brought some sparkle, but the cap change and OPT conversions on the amp have really brought them back to life very nicely.

These guys are old, and just need some TLC, I think.

Erik

[Deang]

Did you put the tap settings back to where they were? If you didn't, and didn't adjust the primary cap value -- your crossover point to the squawker is at 1400Hz.

[Erik Mandaville]

If you're talking to me, no. I changed the autoformer settings; kept them there; but also changed the value of the input cap to the autoformer. This was done only with the new capacitors. When I first made the autoformer changes, I was using the original caps. I did that as an initial trial, and tailored the response by ear from there.

[whamo]

I've found that the Grainger caps work well too. They look identical to the GE's except for the label that says made in China. I'm sure that they would test pretty close and one would be hard pressed to here the difference. Grainger also sells the brackets needed as well. I'll even bet that GE sent all their tooling over there so they probably are in fact GE caps. Mark

[Deang]

Actually, Bob tried some of those, and after testing -- rejected them. The GE cans test very good, while these others are apparently marginal at best. Bob is now using the Sonicap for his builds. Bob doesn't get too excited about caps unless they measure bad, but I think he made a good move here. He loses the classic look to his networks, but nets a sound that I think is a bit cleaner. Naturally he thinks I'm nuts, and says he doesn't hear any difference at all. I believe he hears a difference, but won't admit it because he enjoys driving up my blood pressure.

[Audible Nectar]

Bob's now using Sonicaps in his new builds? My goodness - it IS catching - or else the world is coming to an end[]

"I believe he hears a difference, but won't admit it because he enjoys driving up my blood pressure."

LOL! I'll back you up on this one, Dean. I never used to think much about caps either, until I got to hear those three different MC30 builds. I'm glad I didn't go too wild rebuilding my networks before, because I'm thinking LOTS about how to update these networks for the long haul. You'll no doubt get email from me sooner or later on this......

[Deang]

Bob's now using Sonicaps in his new builds? My goodness - it IS catching ...

Not really. Bob's being as consistant and practical in his thinking as ever. For whatever reason, GE has stopped making those capacitors. Bob loaded up on as many he could find -- but he just can't source them anymore. So, the search was on. Bob says the Sonicaps test as good as the GE cans and are always within tolerance. This was something he couldn't say about other things he looked at. The Sonicaps are also more reasonably priced than some other things out there -- and he's definitely not the sort to pay more for something that doesn't deliver something more. What shouldn't go unnoticed as far as I'm concerned is that none of the cheap metallized types were chosen for his work. I think Bob's response might be that though he doesn't believe there are any real audible differences between them and what he settled on general -- he did see inconsistencies in both measurements and construction with them that caused him to reject them. I'm kind of guessing here, I never asked him!!

[BEC]

Actually, Bob tried some of those, and after testing -- rejected them. The GE cans test very good, while these others are apparently marginal at best. Bob is now using the Sonicap for his builds. Bob doesn't get too excited about caps unless they measure bad, but I think he made a good move here. He loses the classic look to his networks, but nets a sound that I think is a bit cleaner. Naturally he thinks I'm nuts, and says he doesn't hear any difference at all. I believe he hears a difference, but won't admit it because he enjoys driving up my blood pressure.

I guess I could comment on this a bit. I was considered a sort of major user of the GE caps at least by my Grainger store in Little Rock. They stocked a hundred or so of each of the GE sizes I used so I could get them overnight. When Grainger could not get them any more (best I can tell, GE just quit making them), Grainger had a Chinese company start making them to, (supposedly), exactly the same specs as the GEs. Grainger has them branded as "Dayton" which is a name they own according to what they told me.

Grainger sent me (free of charge) a large sample of the Dayton motor run caps when they were first available. I tested them and found them to be all over the place in their measurements. ESR was typically 2 to 3 times higher than the norm for a GE cap. Capacitance varied as much as 4 to 5 percent from stated value where the GE's were almost always within 2 percent. These measurements just tell me that they are not as high quality as the GEs. The higher ESR in particular tells me that the materials or methods of construction are just not up to the GE standards. And after all that they put "Made in China" on the caps and priced them about 40 percent higher than the GE caps.

I reported all that back to Grainger and they could not explain it since (according to Grainger) they are made exactly like the GEs. Perhaps some day the Dayton caps will be as good as the GEs. I think they are probably good enough to use as crossover caps now since that is an easy job for a cap to do well. I would hate to have to use them for motor-run caps though where ESR is much more important. We know that in a crossover ESR can go up to an ohm or more and all that happens is the mids and highs are reduced a bit and efficiency of the crossover is decreased and frequencies shift around a bit. Imagine what happens when ESR goes to one ohm with 240 VAC applied in a motor-run circuit. BOOM!!

Bob

[JohnA]

It turns out the caps were the problem, or at least most of it, after all.

Bob couldn't supply a 1 uF oil cap, so I installed Solens this afternoon and I'm listening to it now. Nice.

I still think the tweeter output is low. I have at least one on

the shelf, but I'm tired of opening it up right now. I also think

the SP12B has more output than the K-22s in my other Heresies.

It's sitting on the floor about 3 feet out of the corner and the bass

guitar notes in some satellite jazz I have on are nice and full.

Thanks for the advice! Now to the restoration of a vintage Heathkit.