Model Six questions

[Guest rrD]

I was just given a pair of KLH Model Six’s and have a couple of questions. First one of the tweeters is painted black. Is this the right tweeter? Other then being black, it looks exactly the same as the other. My other question is, both tweeters work, but sound rather dull, not very bright. Is it time to replace the caps? If so does anyone have a schematic for the crossover?

Thanks

[Guest Sal Brisindi]

Hi,

I also have KLH model 6 speakers but unfortunately both my tweeters are bad. I purchased a set of Pyle Pro model PSN1165 piezo tweeters for less than $4.00 a pair that had the same screw pattern as the original tweeter. I installed them tonight with the recommended 30ohm resistor and they sound pretty damn good, Unfortunately I cannot compare them to the original tweeters as far as sound go. Until I can find a set of original tweeters, the Pyle are here to stay.

Now as far as your tweeter not sounding as good as the other one, I have a set of Dynaco A25's where 1 tweeter sounded weak. I figured the crossover capacitor was bad, I was wrong as I swapped the tweeters between both cabinets and the weak highs followed the tweeter. Maybe you can swap them to make sure its the tweeter or capacitor.

Regards,

Sal Brisindi

[soundminded]

The KLH 6 tweeter is a very unusual animal. It is not a dome. According to someone who posted here, might have been Tom, Kloss tried hundreds of different designs before he settled on this one. It is most unusual, in fact unique for its era. It's FR extends down to a crossover frequency of around 1 or 1.5 khz (I think) where it crosses over to the woofer. The cone is made out of a hard phenolic shell like material which will not break up. It can make an excursions of 1/16 inch which is very great for a driver of its size and type. I think the crossover capacitor is 8 mfd, npc. In the units I replaced them in, they were two 4 mfd paper caps with wax on the outside in parallel in a single body. One pair had failed. If one of the two caps failed, the tweeter output would be severely reduced because the remaining cap will result in a much higher crossover frequency leaving a substantial gap in the overall FR. How difficult is is to replace this tweeter depends on what era it was manufactured in becuse the method of manufacture had changed. In the earliest units, it was epoxied right into the baffleboard making it very difficult. After that it was screwed in even if the woofer is expoxied in and there was enough loose wire to pull the cap through the hole once the tweeter was unscrewed, in fact I was able to get my hand though the hole to reach in and pull it out. A small flashlight and inspection mirror like a dental mirror can help (that's what I used.) To restore this speaker to proper operation it is necessary to obtain an exact replacement tweeter if it is damaged. The good news is a lot of them were made and they were used in other systems like KLH models 5, 12, 17 among others (someone here may have a complete list) so if you find one of those systems which is in very bad shape, perhaps the tweeter can be canabalized from it. Sometimes you will see them sold separately on e-bay. Any other substitute I can think of will probably not work as well but if you must re-engineer the system, look for a tweeter with a very low crossover point like some Morrel models. Or you could use an outboard midrange and tweeter. Good Luck.

[Guest MarkAnderson]

I've seen examples of silver, gold (zinc chromate, I'd reckon), and black tweeters. They are all them same tweeter.

The Model Six is not an especially bright sounding speaker to start with. I believe the tweeter starts to roll off at around 15k or so. That said, bad crossover cap(s) can certainly cause reduced output and, at their age, should be replaced. There's an 8uF (or equivalent) cap (as previously mentioned) in-line with the + tweeter lead and two 2uF (or equivalent) caps between the + speaker terminal and two of the switch terminals.

There is a schematic posted somewhere on this site. Perhaps in the KLH library.

[KLHSvcMgr]

Hi Everyone...

Been away for awhile and so I am catching up.

The tweeter used in the Model 6 loudspeaker was the same in the Model 4, 7, 9 and 10 up until serial number 93,000.

Production after serial number 93,000 used a different tweeter (C00103) which was also used in the Model 17, 20 and 33.

Mark

[Guest matty g]

Hi Mark

Can you tell me if the tweeter used in the serial numbers below 93,000 were 4 ohm units, and were all of the tweeters above 93,000 4 ohm units? I read somewhere that an 8 ohm unit was used in the Sixes and maybe the other large models - just a rumor?

Thanks

Matt

[Andy]

According to a 1968 KLH ad, there is a bit of a difference in the tweeters used for various models-

Model Six & Model Five - 1 5/8" tweeter

Model Twelve, Model Seventeen & Model Twenty - 1 3/4 " tweeter

Model Twenty two, Model Twenty Four, & Model Twenty Six - 2" tweeter

I'm sure the crossover points were also different, not sure what the internal difference of the tweeters was though.

[soundminded]

>The Model Six is not an especially bright sounding speaker to

>start with. I believe the tweeter starts to roll off at around

>15k or so.

Tests showed the tweeter is good to about 16 khz. I've had very good results adding a pair of 3/8" upfiring 8 ohm polys per channel crossed over at 6db per octave at 6 khz with a 3.3 mfd NPC each and some equalization. I'm thinking of a project to convert this to a 3 way system which is feasible because of the 3 terminal configuration. The range of both drivers can therefore be further restricted by adding external components to the crossover network. I've got some 4" RS full range drivers which will make excellent midrange speakers. I don't think a forward firing supertweeter will be necessary.

[Guest MarkAnderson]

>According to a 1968 KLH ad, there is a bit of a difference in

>the tweeters used for various models-

>

>Model Six & Model Five - 1 5/8" tweeter

>Model Twelve, Model Seventeen & Model Twenty - 1 3/4

>" tweeter

>Model Twenty two, Model Twenty Four, & Model Twenty Six -

>2" tweeter

>

>I'm sure the crossover points were also different, not sure

>what the internal difference of the tweeters was though.

Interesting, especially since the Model 6, 17, 20 use exactly the same hi-pass circuit in the crossover.