12.5 question

[ChrisM]

Does anyone know what the T/S values for the 12.5 drivers might be? I want to have some baseline numbers so when I apply Roy's sealant to them I can compare my measurements to the "originals". I'm thinking they need a light touch. I'm also looking for the same sort of data for Philips midranges. Any help appreciated!

[JKent]

I don't know about the T/S parameters but I assume you read the service bulletin: http://www.classicspeakerpages.net/library/klh/other/klh_schematicsservice/klh_service_bulletin_60.pdf

It gives no guidance about how heavy but I agree, a light touch. To tell the truth, I've restored many speakers that use the 12.5 driver: Twelves, Fives, Elevens, Fourteens, Fifteens, Nineteens (probably some others) as well as all of the Model Eight, Thirteen and Twenty-One radios that use the 12.5 and I rarely use the surround goo. But KLH's Service Bulletin is pretty clear: It should be used on ALL 12.5 drivers and woofers regardless of the reason for service.

Kent

[ChrisM]

I did read bulletin 60. I was just hoping for some baseline data. The problem is the same for most old drivers, they just didn't publish any of this data.I'm sure Henry had it all scribbled down somewhere. The only people who published anything at all were those people who sold raw drivers. A light touch it is for the 12.5s.

Chris

[JKent]

8 minutes ago, ChrisM said:

I'm sure Henry had it all scribbled down somewhere.

Maybe not.

According to Wlkipedia (and you know it can only go there if it's true ) "Beginning June 1972, Richard H. Small published a series of very influential articles in the Journal of the Audio Engineering Society restating and extending Thiele's work."  Henry had left KLH in 1968 to start up Advent (to build projection TVs. By then the speakers were sort of an afterthought).

Maybe ask PeteB. I think he's calculated TSPs for several speakers.

[Pete B]

First question, what are 12.5 drivers, can you provide a link?

[Pete B]

Next it sounds like you want to re-dope a woofer edge and you want to know the T&S parameters.

My advice is that you don't really need them due to the nature of acoustic suspension speakers.

The first thing to consider is the in box resonance Fc and since the air spring dominates the important

parameter is moving mass which is mainly the cone, VC assembly and a bit of air that couples to the 

cone.  These do not change.  What you need when you dope it is to keep the compliance high.

You could measure the woofer in free air and/or in the box in its old state, then dope it and measure

both again.  Fs might change a bit, Fc should change less due to the air spring and all that is really

important is Fc.  

The second important parameter is Qts, which becomes Qtc in box this is mainly determined by the

motor strength combined with the resonant system at Fc.  If Fc is correct and the VC and motor are

still in spec then Qtc should be correct.

[Pete B]

About doping the AD5060 that is with the fabric edge I take it?

I'd use a very light coat of a material that remains very soft.

Edit:  Don't use Permatex Form a Gasket,  JKent wrote this:

• I see a "possible" problem. Our late friend Carl Richards (one of the moderators here btw) did great work but in 2009 he may have still been using Permatex to seal the woofers. That was suggested in the 2007 AR-3a restoration guide but that was a mistake. Turns out Permatex eventually hardens somewhat. The ONLY sealant that should be used is RoyC's butyl rubber solution but that may not have been available in '09. So the real question may be; how to remove the Permatex."

 

Here are some threads about re-doping tweeters but I don't think that shellac or varnish is the 

correct material for edges:

https://audiokarma.org/forums/index.php?threads/how-to-re-dope-snell-tonegen-foster-tweeters-model-e-j-k-gens-i-ii.696046/page-2

https://www.audiokarma.org/forums/index.php?threads/re-coating-audax-dome-tweeters-w-measurements.559836/

[JKent]

1 hour ago, Pete B said:

First question, what are 12.5 drivers, can you provide a link?

Pete,

The 12.5 driver was a 4" full-range, very similar to the Foster 10F3 I believe. KLH used them as radio speakers in the Eight, Thirteen and Twenty-One. They were the mids in the Five and Twelve and they were standalone full-range speakers in many of the compact systems such as the Eleven. They were also used in pairs in the Fourteen, Fourteen B and Nineteen,

Kent

[ChrisM]

What Kent said. Also, and perhaps less important, there was the tweeter version as in the Model 24.

I know from the saga surrounding Roy's experiments to recreate the cloth sealant that the main thing is to monitor the Fs. The question is what was the Fs of them when they were new? I can measure a dried out driver and then reseal it and the Fs shouldn't go up and remain there over time but Henry didn't ship them dried out so I don't know if it is REALLY correct. Maybe I just obsessing over this but you can't really say it sounds right if you don't know if it works right. I won't even ask about the correct magnetization level for the Alnico magnets in old woofers......

Chris

[ChrisM]

Pete,

i just looked at the links you suggested about re-doping tweeters. I have some of the Audax tweeters which are a bit crusty so thanks for the links. I also think a call to Richard So of ADS restoration fame would be good since they work on highly doped tweeters all the time. I was PMing with Roy about his sealant and he suggested that less is more. The thing about the 12.5s and the Philips mids is that they also go to rather high frequencies and the surround if not terminated correctly could mess that up.

Chris

[Pete B]

"The thing about the 12.5s and the Philips mids is that they also go to rather high frequencies and the surround if not terminated correctly could mess that up."

I agree.

Is the 12.5 sealed back or did they use a cup behind it?

[Pete B]

Was the 12.5 similar to this also?

https://www.madisoundspeakerstore.com/approx-4-fullrange/fostex-fe103en-4-full-range/?gclid=EAIaIQobChMI1ZqrvoDJ5AIVCZSzCh3XHwwSEAYYAiABEgJYvfD_BwE

Open back full rangers like these usually have an Fs of 80 to 120 Hz.

Sealed back Fs would probably be 200 to 500 Hz depending on how Kloss designed the system.

I know, not very specific but if you measure Fs/Fc at 1 KHz something is probably wrong.

[JKent]

2 hours ago, Pete B said:

Was the 12.5 similar to this also?

That's my understanding but I don't know for sure. I've considered using that driver in KLH restorations with blown 12.5 (4") drivers but originals are so common there's no need. Also considered this: https://www.madisoundspeakerstore.com/approx-4-fullrange/markaudio-chp-70-gen2-natural-paper/

Quote

Is the 12.5 sealed back or did they use a cup behind it?

It's open.

[ra.ra]

50 minutes ago, Pete B said:

Is the 12.5 sealed back or did they use a cup behind it?

Both the KLH 12.5 and the Phillips 5060 are open-backed with cloth surrounds. In the KLH Five and Twelve (used in pairs), they are installed in their own separate sealed cabinet chamber. My familiarity with the Phillips driver (with whizzer cone) is from its use in several of the best Rectilinear speaker models, where it is installed in an isolated cup chamber.  Attached images are: KLH 12.5; Phillips 5060; Phillips 5061; and 5061 tech sheet. If you look closely at the Phillips cones, there appears to be traces of a liquid sealer probably used on the cloth surrounds.

 

 

[Pete B]

Thanks for all the info,  it would be great to find out what was used originally.

Save a sample from a blown 12.5 and perhaps a materials person might analyze it someday.

I've been told that Shoe Goo and E6000 are the same product from the same company, no

idea if this might work:

http://eclecticproducts.com/downloads/tds-shoegoo-us-au-nz.pdf

How to dilute it:  https://www.rcgroups.com/forums/showthread.php?385740-Thinning-Shoe-Goo

[Pete B]

I'm fairly certain that Jkent sent me a 12.5 years ago, did it have a buzz or something?

Seem to remember measuring it and reporting T&S here somewhere.

Seems it was the KLH-20 tweeter version that probably has a much stiffer spider for 

a higher Fs:  http://www.classicspeakerpages.net/IP.Board/index.php?/topic/4238-klh-20-tweeter-dissection/

 

[JKent]

I believe what I sent was a 3" driver, originally used in the Model Eight. Here's a pic of the 4" 12.5 driver used in later Eights, with the 3". The 3" had an interesting history: Back in 1959 the audio consultants Bolt, Beranek & Newman had a project to equip the Senate chambers with high quality individual speakers for each Senator. So BB&N went to KLH and Kloss designed a speaker but the project fell through, so the speaker ended up in the Model 8 radio in 1960.

The 3" speaker was very high quality. IIRC you were not able to take it apart. Unfortunately the hard plastic rim will break if the speaker is treated roughly, as you can see in the photo. I've had some success fixing them with JB Weld.

Sorry for drifting off-topic.

[ra.ra]

51 minutes ago, Pete B said:

....no idea if this might work:

There have been many hypotheses applying and guessing at suitable re-sealing materials which have resulted in damaged or ruined drivers, and unless/until these materials are documented with results measured over time, my own attempts to re-seal cloth surrounds will remain confidently loyal to the liquid butyl goop that Roy has cooked up and generously shared with this community. It works very well on AR and KLH drivers, and I see no reason why it shouldn't perform the same on these Phillips drivers or similar.

BTW, where does this "12.5" nomenclature come from?  

[JKent]

8 minutes ago, ra.ra said:

BTW, where does this "12.5" nomenclature come from?  

Dunno. The only place I've ever seen it was in Service Bulletin #60 and it was called "Twelve point five"

[Pete B]

I was talking about the one on the left and if you read the thread I talk about removing the grille.

I also have the one on the left that you sent but have not done anything with it.

[Pete B]

16 minutes ago, ra.ra said:

There have been many hypotheses applying and guessing at suitable re-sealing materials which have resulted in damaged or ruined drivers, and unless/until these materials are documented with results measured over time, my own attempts to re-seal cloth surrounds will remain confidently loyal to the liquid butyl goop that Roy has cooked up and generously shared with this community. 

As far as I know Shoe Goop is butyl goop.  Someone who needs some might want to experiment.

[ChrisM]

In the case of the AD5061 drivers I have out of Rectilinears, there is the original Philips spec sheet which lists the Fs as 85Hz. I'm trying to ascertain where anyone knows what a typical production Fs would have been for the 12.5s when they were manufactured. KLH wouldn't publish this because they didn't sell drivers separately. The was a member here who, I believe, uploaded the service bulletin 60 about the sealant. I think, without looking it up, that his name was KLHSvcMgr. He might have some insight on this but I think he's long gone.

By the way, the AD5061s I have are totally dried out and they measure 91 for their Fs. If they were about 85 back in the '60s, I don't think they'll be hurt by Roy's goo and probably be helped by making them more compliant. I may thin the goo out a bit because it was tested on woofers not the super thin surrounds on the drivers we're talking about.

[ChrisM]

I did a search and found him. Mark Wilson, goes by KLHSvcMgr. The posts were back in 2007 or so.

[ra.ra]

36 minutes ago, Pete B said:

As far as I know Shoe Goop is butyl goop.

Yeah, you may be right, Pete, but that data sheet does not describe the chemistry of the solid components, so we just don't know.

13 minutes ago, ChrisM said:

I may thin the goo out a bit...

Always a good idea, particularly in a "test case" scenario. I have some AR-4 woofers that had never been touched in fifty years but the surrounds were dry, and a little bit stiff and delicate. Carefully, I brushed on some solvent a few times and let that fully evaporate, then followed up with a light coat of Roy's butyl and this really did improve their texture and flexibility.  

[ChrisM]

Great idea on the pre-treatment with solvent idea. I guess I'll have to spring for the gallon can of Toluene. The only place I can find it has it in a gallon can for $30.

I'll have enough to last the rest of my life. Oh well.