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Speakerlab K horn rebuild help


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>> WMcD said:

>> Not everyone likes the Speakerlab woofers.  Dr. Bruce Edgar said the only was of fixing the situation was to smash them with a sledgehammer.  PWK published a Dope from Hope about an >> unidentifed near copy (must have been the SK) and the curves were not so good


Don't believe everything that you read!


It depends on what woofer came with the SpeakerLab you got.  If you were lucky enough to get the W1504S woofers, this was the exact CTS 4-Ohm woofers (K-33) that Klipsch used during that time period.  SpeakerLab also offered the W1508S  8-Ohm version that was special order if you wanted to run four SpeakerLab K speakers off one amp.  Even in the SpeakerLab catalog they express that they preferred the 4-Ohm version (W1504S) for the SpeakerLab K speakers.


There is a lot of inaccurate information out there about the SpeakerLab K and it's woofers and it's accurate copy of the bass-bin.  I bought my AK-4 Klipschorn's brand new and always curious about how well SpeakerLab K held up to the Klipschorn, finally in 2018 I found a mint SpeakerLab K factory made pair came up for sale 5 hours away.  Several people told me the woofers would have to be replaced with K-33 woofers or the bass will never wake up that tried the SpeakerLab K already so I went ahead and ordered brand new K-33 woofers to replace them.

I made the 5 hour trip each way and picked them up. They are flawless with a beautiful red/golden mahogany veneer over high-quality ply-wood, not one piece of MDF or particle board crap is in this set.  They are factory made and bought them from the original owner that has had them since 1977.  They came with HT350 tweeters/metal horn (like K-77), Atlas PD-5VH Mid, Same metal K-400 horn but with ribs, and CTS woofers 4-Ohm (W1504S) same that Klipsch (K-33) used at that time.


When I got them hooked up and listened, I was shocked at how good the bass was! I could hear right away that the mid and highs were more subdued than what I was used to with my AK-4 Klipschorn's. The problem with the SpeakerLab's wasn't the bass, it was the crossovers!!!  Once I built a set of Klipsch Type A crossovers, they are great Klipsch sound!  I changed the woofers to the K-33 and they sound very much a like only being that the square CTS (W1504S) woofers go slightly lower than the K-33 round magnet woofers. After going months back and forth between the woofers, I decided to keep the CTS (W1504S) woofers that came with the SpeakerLab K in them, they sound a little better and slightly lower bass but it's so minimal it doesn't really matter.  I did not need to buy new woofers for them like a few told me, they must have had a different version woofers with their SpeakerLab K than I did.  All the drivers in this 1977 SpeakerLab K looks brand new, I don't think this guy ever used them much! He kept decorative cloth covers over the speakers when not in use, one of Pink Lady and the other of Blue Boy. He was nice enough to give me the covers too. I am also shocked how well these factory SpeakerLab K are built!  These things are better built than my AK-4 Klipschorn's!  When I open up the Klipschorn and SpeakerLab K and compare, I am sorry to say this but it's amazing the level of care and detail on quality build these SpeakerLab K has over my new Klipschorn's!  Even something as simple has putting all 8 screws in to hold the woofers, Klipsch only puts 4 screws.  When I asked Klipsch about this, they said they have always only put 4 screws in for each woofer for the Klipschorn.  What?  Really?


So I just want to help others here that if you get SpeakerLab K speakers and they come with the W1504S woofers, you don't need to replace them if they are working and in good shape. I bought new woofers when I didn't need to after others said I would or they would have no bass.  They have bass!  The problem is the crossovers, you will have to change them to Klipsch Type crossover or the Mid and Highs are more subdued sounding than the Klipsch sound.
As for the bass-bin, these SpeakerLab K bass-bin are every bit as good as my Klipschorn bass-bin! They have bass and do it very well! There is nothing missing with the bass!

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On 3/6/2020 at 12:03 PM, No.4 said:

I did the same thing with my Eliptrac horns


Man that looks really good! I haven't normally liked the way Eliptrac horns look, but something about that tall tweeter bring it all together. I'd like to see more pics of your speakers.

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On 4/10/2020 at 12:46 AM, SkyDover said:

Even something as simple has putting all 8 screws in to hold the woofers, Klipsch only puts 4 screws


Didn’t make “a dime’s worth of difference.”    


My my experience with factory built ~1976 Speakerlab Ks was similar.  Mine were special ordered 8 ohm versions, as I typically ran a pair in parallel on each channel to present a 4 ohm load to my Dynaco ST400.  I think the crossovers, which used L-pads instead of autotransformers, we’re always the weak link.  After decades they need updating under any circumstances.



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  • 11 months later...

I just stumbled upon this conversation and having built my Speakerlab Super K's in my Dad's garage in 1976 may be of assistance. I know it's been a year and am wondering how things are working out. My super K's have Electrovoice T350's not T35's. The T35 was smaller, less expensive and not as desirable. The SK W1504 (4 ohm) woofer had a alnico 5 magnet. As long as the free air resonance of the woofer is 18 cycles or less should work to get down to 31.2 cycles flat. Pat Snyder injected what He called "magnar" (Ferrofluid) into the voice coils of the tweeter and mid drivers only on the Super K's. I would be interested in hearing what you did with your crossover networks as mine are original factory issue crossed at 400 and 4000 cycles. I still have the original Building plans for the K's I paid $5.00 for. I've been enjoying my corner horns for about 45 years now. I'm using a Carver C2 preamp and Carver TFM-55 amp. Sansui SR 929 turntable. Jim



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  • 6 months later...

I bought a pair of W1504S from SpeakerLab back in 1977. Recently I bout a pair of Khorn knockoff bass bins that look like they were built with SpeakerLab plans however it is high grade plywood and thicker than the 3/4”. My question is how much batting material to put in the Woofer enclosure? I have Acosta-Stuf polyfil batting. Should I use 2lb or just pack in as much as I can?

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