1993 KLH 81 Premier Tweeter Death

[jgstudios]

A friend gave me a pair of KLH 81 2-way premier bookshelf speakers many years ago, but they stayed in a closet until last night. I plugged them into an vintage Tanberg reciever, and they seemed to play, but something was not right. I decided to investigate and removed all the speakers from the cabinets. The VOM shows the woofers are reading within spec approx 6.5 ohms, and sound is coming out ok. The tweeters, on the other hand, read a big ZERO and no sound comes out of either one. So naturally I'm very bummed. So first, can anyone tell me if the standard terminal to terminal VOM test on the tweeters is the right way to check these? Is there anything special about these tweeters that would make that test invalid? They look like standard dome tweeters to me. Second, where can I get equivalent quality replacements? I presume factory tweeters are going to be hard to find, and I don't really know about that market, so any suggestions, modern equivalents? Id' like to learn as much as I can about these, and I found an old 1993 stereo review article, but it's hard to find much else. Looks like the cossover hits at 1300 Hz. I know these might not be worth the trouble, but it's fun to fix them and see what they sound like.

 

[zieglj01]

Look for Model 81 and 61 on ebay --
https://www.ebay.com/itm/KLH-Loudspeakers-Premier-Series-Model-61-Single-Speaker-6-Woofer-1-Tweeter/302628144658?hash=item46760b0612:g:-sgAAOSwGBhad8v6:rk:31:pf:0

Contact Simply Speakers, and also Parts Express

However all in all, the investment for tweeters may not be worth it

 

[lovinthehd]

Keep in mind there's more to replacing tweeters than their physical dimension and crossover point as far as how a new tweeter will work with your existing components in the speaker. Finding OEM replacements is not likely without cannibalizing another of the same model (or maybe zieglj01 has info on the two models he mentions using the same tweeter).

 

[Dennis Murphy]

Keep in mind there's more to replacing tweeters than their physical dimension and crossover point as far as how a new tweeter will work with your existing components in the speaker. Finding OEM replacements is not likely without cannibalizing another of the same model (or maybe zieglj01 has info on the two models he mentions using the same tweeter).

Right, although for the record I very much doubt that the crossover point is 1300 Hz. That's just a garden variety 1" dome tweeter, and judging from the appearance and probably cost, I doubt that it would be happy much below 2400 Hz.

 

[BoredSysAdmin]

In addition to that said above (and I 100%) agree - measuring static electrical resistance on speakers is pointless since it's a dynamic number and provided number by the manufacturer is (forgive me for oversimplification) an average resistance across speaker's usable output.

 

[jgstudios]

I remember when the KLH brand used to garner some degree of respect, but obviously things changed. Yeah, the cost of the tweeter replacement would not justify the fix based on that eBay post, but I'm curious, so I may get a set of parts express tweeters and see what they sound like. Now that I've spent some time looking at the guts of the thing I see the quality here is pretty much a consumer model. Here is a quote from the HI-FI Review Article "The Premier 81, one of two bookshelf models in the line, is a vented two-way system with an 8-inch woofer crossing over at 1,300 Hz to a 1-inch soft-dome tweeter. The woofer has a 1.5-inch high-temperature voice coil and a polymer-fiber cone. The tweeter voice coil is wound on a Kapton form and cooled by ferrofluid." I'm wondering if that number was a typo and should have read 3100 Hz. Anyway, Doesnt the VOM test simply indicate the condition of the voice coil? If I'm getting a zero or OL reading, doesn't that show the coils are toast ? Thanks for the input guys .

 

[MrBoat]

When the tweeters (Dayton/Usher RS28A) for my Bagby Continuum speakers stopped being manufactured, it irked me that this was to decide the ultimate future of my speakers serviceability. First thing I did was to find a pair of the actual diaphragms. I think I may have even gotten the last pair in captivity.

Whether there is a cross reference to the part from Usher themselves, I do not know. I also wanted the option to build another complete pair of the speakers so, I found another pair of the RS28A on the e bay. Of course, they have since upgraded the design to use another tweeter but that would mean a crossover change, I am sure. I don't care if the upgraded version is better. I was already at that place with speakers of not improving something that doesn't really need it.

I don't hold much reliance on manufactured goods being serviceable these days, but the things I make myself, should at least be serviceable by me for the long term. It's the only way left to thumb nose at the current disposable goods trend.

 

[TLS Guy]

I remember when the KLH brand used to garner some degree of respect, but obviously things changed. Yeah, the cost of the tweeter replacement would not justify the fix based on that eBay post, but I'm curious, so I may get a set of parts express tweeters and see what they sound like. Now that I've spent some time looking at the guts of the thing I see the quality here is pretty much a consumer model. Here is a quote from the HI-FI Review Article "The Premier 81, one of two bookshelf models in the line, is a vented two-way system with an 8-inch woofer crossing over at 1,300 Hz to a 1-inch soft-dome tweeter. The woofer has a 1.5-inch high-temperature voice coil and a polymer-fiber cone. The tweeter voice coil is wound on a Kapton form and cooled by ferrofluid." I'm wondering if that number was a typo and should have read 3100 Hz. Anyway, Doesnt the VOM test simply indicate the condition of the voice coil? If I'm getting a zero or OL reading, doesn't that show the coils are toast ? Thanks for the input guys .

Yes, those voice coils are burnt out. I bet the crossover is 1300 Hz which is why the tweeters are burnt out. Those speakers typical of the era, have large, by modern standards bass drivers. It is a fairly heavy 8" cones that really would need to be crossed at 1300, certainly by 1500 Hz. The problem is there is a lot of power that the tweeter has to handle. So you are looking for a tweeter that has a free air resonance around 700 Hz. It also must no roll off until below 1200 Hz at least.

Most of those tweeters back then for that type of application were from Vifa or Peerless.

Peerless now make a version of the an old Vifa tweeter which yours may be.

This is it.

It will do what you want to a point. The problem is that if pushed it will probably burn out like yours have. The power bandwidth is quoted as above 2 KHz. As you can see it does not roll off until below 1 KHz, and it free air resonance is low enough for your application.

Now you will probably have to modify the L-pad in the crossover to get the balance right between woofer and tweeter. Even then the speakers will probably not sound the same as the originals. You will have to modify the speaker to actually install the tweeters.

Only you can make the judgement if all that trouble is worth it, for a design that is fundamentally flawed, which has caused both tweeters to burn out.