Speaker ID Help - Speakerlab K made by ISC

[Jdiesel87]

I picked up some what I thought were Speaker Lab K corner horns but after getting them home and digging in a bit deeper they don't match up with the regular Speakerlab kits. The enclosures are a mixture of plywood and particle board but very well constructed and point to something commercial rather than DIY.




Tweeter is a EV T-350 which was an upgrade on the Speakerlab kits to my knowledge. These alone will be worth my purchase as I hear they are well regarded.



The mid driver is a EV 1828R and the horn is a fiberglass construction with no visible markings. My research indicated that early Speakerlab K's did come with a fiberglass mid horn but the EV 1828R was never an option.





Finally the woofer is unknown. I opened it up and had a look inside but the driver was a generic stamped basket 15". No markings of identifiers. I'm a bit lost on these but perhaps they were replaced by the previous owner.





There is a badge on the front grill cover that has the letters ISC. The son of the person I purchased from thought they may have been construction in Canada possibly BC or in the Maritimes.



My plan is to restore the cabinets as they are very well built and the veneers is in good shape overall. I'm going to keep the T-350 tweeters, possibly look at replacing the mid driver and horn after testing what is currently installed, and replacing the woofers.

These were purchased in Canada. Does anyone have any info on ISC? Or perhaps businesses in Canada who were doing commercial Speakerlab K builds?

 

[JRhoBurton]

I picked up some what I thought were Speaker Lab K corner horns but after getting them home and digging in a bit deeper they don't match up with the regular Speakerlab kits. The enclosures are a mixture of plywood and particle board but very well constructed and point to something commercial rather than DIY.
View attachment 3307973

View attachment 3307974

Tweeter is a EV T-350 which was an upgrade on the Speakerlab kits to my knowledge. These alone will be worth my purchase as I hear they are well regarded.

View attachment 3307976

The mid driver is a EV 1828R and the horn is a fiberglass construction with no visible markings. My research indicated that early Speakerlab K's did come with a fiberglass mid horn but the EV 1828R was never an option.

View attachment 3307977

View attachment 3307978

Finally the woofer is unknown. I opened it up and had a look inside but the driver was a generic stamped basket 15". No markings of identifiers. I'm a bit lost on these but perhaps they were replaced by the previous owner.

View attachment 3307979

View attachment 3307980

There is a badge on the front grill cover that has the letters ISC. The son of the person I purchased from thought they may have been construction in Canada possibly BC or in the Maritimes.

View attachment 3307981

My plan is to restore the cabinets as they are very well built and the veneers is in good shape overall. I'm going to keep the T-350 tweeters, possibly look at replacing the mid driver and horn after testing what is currently installed, and replacing the woofers.

These were purchased in Canada. Does anyone have any info on ISC? Or perhaps businesses in Canada who were doing commercial Speakerlab K builds?

I can't help, but good luck with that. I suppose it's possible that other companies made versions of the K-horn, after the patents expired, which are unrelated to Speakerlab.

 

[Jdiesel87]

A minor update:

I was able to confirm that the mid horn is in fact a Speakerlab HD350 (Fibreglass version) which is an exact clone of the K400.

Electro Voice also produced a K-56 (EV-1828) as a temporary replacement for K-55's in 1974. Found on Cornwall's, La Scala’s, and Belle's produced in that year.

So it seems like Klipsch did for a short time use a EV mid driver. The fact that it is an 8ohm versus a 16ohm will require some crossover modifications should I decide to drop in a Klipsch AA network. It's tempting to swap them out for some Atlas PD-5VH drivers. Will have to think about this.

There is a good chance the woofer is a Speakerlab W1504S or W1508S. Much like the K-33 there were some with square magnets and some with round. I will need to measure the DC resistance to see if it is a 4ohm or 8ohm. On the off chance they might be something like an EV SMX2151 but i'm not confident in that.

 

[Jdiesel87]

I measured the DC resistance of the woofers and they both came in at 5.8ohms which suggests to me that that are indeed 8ohm woofers

I hooked them up to my little Hifiberry Amp2 Raspberry Pi board and gave them a test. Wow did they every get loud off of a tiny bit of power. I can confirm that all drivers are functioning which is a big win. The Lpads are a bit scratchy but I will hit them with some deoxit when I disassemble them.

Next step is to remove the tophats and get the cabinets ready for refinishing.

They way I see it I have 4 options.
1. Leave everything the way it is and refresh the capacitors in the existing crossover. ($)
2. Keep all the existing drivers, measure them individually and design an improved custom crossover. ($$)
3. Swap out the woofers for K-33-E, the mids for Atlas PD-5VH, and replace the crossover with a Type AA. ($$$)
4. Ditch the crossovers and go active with a MiniDSP Flex8 and 6 channels of amplification. ($$$$)

 

[avguytx]

@Jdiesel87 Those horns and crossovers are definitely a minor "weak link" in the SK's as the cast HD350 horns were much better and closer to the K400 horn. I picked up a pair of SK's last September and they had the W1508S woofers, Atlas PD5VH mids and their WA4000 tweeters (EV T35 driver on their own horn). Mine came with a set of brand new never used Crites W1526C cast woofers so I used those instead. The original woofers were ok but I preferred the Crites. I also went to Celestion CDX1412Neo tweeters on 3D printed tweeter horns and stayed with the HD350/PD5Vh mid setup. RJM in Washington has replacement crossovers for those but they are a grand for a pair. I built my own set called the "X4500" designed by a couple of members here on AK. They were designed for Klipschorn users who change out the OEM T35 tweeters for something better (yours are better than T35, of course).

As far as your listed options, the first is ok but those crossovers in them are awful and would benefit changing completely. You could try new caps but may not be a huge change. If you decided to do something new, there's the X4500 crossover that can be built that "might" work for yours with that T350 tweeter. Your original woofers might be original but there was usually a tag somewhere on them that said whether they were the W1504S or W1508S. K33's or any of the variants would work in place. Going active is ok, I guess, but way more stuff involved.

What do the back sides look like? Have a pic of the whole back? Your cabinets do look quite good. I'm rebuilding the tops on mine, eventually, where they will have the "collared" look like the Klipschorn AK6 where I can separate them. I also painted mine satin black as the veneer was getting a little ratty after 40+ years. I can veneer but paint was cheaper. lol

My crossovers I built..

 

[Jdiesel87]

Thanks for the reply! I don't have good photos of the back right now but I will take some tonight when I'm home. I don't know if the Klipschorns built around this era had backs on the bassbin but my SK's do. I removed the tophats already in anticipation of sanding the cabinets down.

Do you recall if your stock W1508S woofers had a square or round magnet? I can't seem to find any photos of the round magnet version online but old posts allude to one existing. Either way getting some new K-33-E is the easiest and cheapest change I can make so that's likely what I'll do to remove at least one variable from the equation.

I don't know if the T350 goes much lower than the T35/K77 but it does go higher and I do believe it runs 1db hotter. How does your CDX1412Neo compare to the K77 efficiency wise? Did the X4500 crossover require adjustments to bring the tweeter levels down?

Where did you source your autotransformers from? I see Crites sells them but I was wondering if there was another option, perhaps Mouser or Digikey.

 

[absolve2525]

I picked up some what I thought were Speaker Lab K corner horns but after getting them home and digging in a bit deeper they don't match up with the regular Speakerlab kits. The enclosures are a mixture of plywood and particle board but very well constructed and point to something commercial rather than DIY. I know AV
View attachment 3307973

View attachment 3307974

Tweeter is a EV T-350 which was an upgrade on the Speakerlab kits to my knowledge. These alone will be worth my purchase as I hear they are well regarded.

View attachment 3307976

The mid driver is a EV 1828R and the horn is a fiberglass construction with no visible markings. My research indicated that early Speakerlab K's did come with a fiberglass mid horn but the EV 1828R was never an option.

View attachment 3307977

View attachment 3307978

Finally the woofer is unknown. I opened it up and had a look inside but the driver was a generic stamped basket 15". No markings of identifiers. I'm a bit lost on these but perhaps they were replaced by the previous owner.

View attachment 3307979

View attachment 3307980

There is a badge on the front grill cover that has the letters ISC. The son of the person I purchased from thought they may have been construction in Canada possibly BC or in the Maritimes.

View attachment 3307981

My plan is to restore the cabinets as they are very well built and the veneers is in good shape overall. I'm going to keep the T-350 tweeters, possibly look at replacing the mid driver and horn after testing what is currently installed, and replacing the woofers.

These were purchased in Canada. Does anyone have any info on ISC? Or perhaps businesses in Canada who were doing commercial Speakerlab K builds?

Awesome find! Especially with the upgraded tweeter! I have a similar model to yours, with the fiberglass horn and T—350 tweeters. Mine have the Atlas midrange drivers however, and 4ohm woofers. Speakerlab made a crossover for the 8ohm woofer, so yours may have that design already included. Your crossover may also have been adjusted for the 8ohm midrange driver also. I know the Atlas midrange is 16 ohms obviously. I know AVGUYTX totally revamped his Ks and I'm sure they're killer, but there's nothing wrong with the original Speakerlab woofer and i don't see or hear a problem with a fiberglass horn vs metal. Klipsch moved away from cast metal horn with their K401 horn and claimed improvements. If you want a different midrange horn entirely, there are plenty out there such as a popular one mentioned in the forums. Do you have pics of the crossovers? That would help us determine if they have accounted for the 8ohm midrange horn. Again, awesome find! Congrats That T-350 is a definitely a higher caliber compared to the base tweeter.

 

[avguytx]

Thanks for the reply! I don't have good photos of the back right now but I will take some tonight when I'm home. I don't know if the Klipschorns built around this era had backs on the bassbin but my SK's do. I removed the tophats already in anticipation of sanding the cabinets down.

Do you recall if your stock W1508S woofers had a square or round magnet? I can't seem to find any photos of the round magnet version online but old posts allude to one existing. Either way getting some new K-33-E is the easiest and cheapest change I can make so that's likely what I'll do to remove at least one variable from the equation.

I don't know if the T350 goes much lower than the T35/K77 but it does go higher and I do believe it runs 1db hotter. How does your CDX1412Neo compare to the K77 efficiency wise? Did the X4500 crossover require adjustments to bring the tweeter levels down?

Where did you source your autotransformers from? I see Crites sells them but I was wondering if there was another option, perhaps Mouser or Digikey.

Mine were not closed off in the back. I thought about it but they work well in the corners so I didn't decided against it...for now. Hopefully they aren't enclosed like one person's Klipschorns I saw where the previous owner had literally enclosed them to the point they were closed off. lol

My woofers have the original tags on them and are both square.

The CDX1412's have more extension oh HF than the T35 and even as bad as my HF hearing is, I can kind of tell the difference. lol Efficiency wise, they might be a little more, and they are adjusted via the autoformers along with the mids as a group for adjustability.

I bought my autoformers and coils from @Deang but don't know if they are plentiful or not. Those are not something that Mouser or Digikey sells. I did initially update the original SK crossovers but mine were the last generation, presumably better versions, that used the dip switches for adjustment. Changed out the capacitors and went to 16ga wiring for the mid and tweeter. Those sit idle now.

 

[Jdiesel87]

Awesome find! Especially with the upgraded tweeter! I have a similar model to yours, with the fiberglass horn and T—350 tweeters. Mine have the Atlas midrange drivers however, and 4ohm woofers. Speakerlab made a crossover for the 8ohm woofer, so yours may have that design already included. Your crossover may also have been adjusted for the 8ohm midrange driver also. I know the Atlas midrange is 16 ohms obviously. I know AVGUYTX totally revamped his Ks and I'm sure they're killer, but there's nothing wrong with the original Speakerlab woofer and i don't see or hear a problem with a fiberglass horn vs metal. Klipsch moved away from cast metal horn with their K401 horn and claimed improvements. If you want a different midrange horn entirely, there are plenty out there such as a popular one mentioned in the forums. Do you have pics of the crossovers? That would help us determine if they have accounted for the 8ohm midrange horn. Again, awesome find! Congrats That T-350 is a definitely a higher caliber compared to the base tweeter.

They are covered in a layer of dust right now. Once I've documented everything well enough I will remove the boards and have a better look. I can't see that the capacitor values are. This is what I have right now.

 

[avguytx]

I hate these ads that block posts while on a cell phone. Trying to read the thread and all this crap gets in the way. One of the reasons I stopped subscribing after being on here 17 years.

Sorry to derail...

 

[avguytx]

They are covered in a layer of dust right now. Once I've documented everything well enough I will remove the boards and have a better look. I can't see that the capacitor values are. This is what I have right now.

Yeah, I'd replace those. Even an AA crossover would be better.

 

[Jdiesel87]

I managed to get the cabinets finished over the weekend. The veneer was nice and thick so it took well to sanding. Starting with 100 grit, I was able to get even the deep scratches and gouges out. I followed up with some 120 and then 220 then hit it with two coats of Danish oil. Pretty happy with how they turned out.



Now I'm trying to source some Klipsch Type A, Type AA, or Type E crossovers to complete the build. Hell even a pair of T2A autotransformers would suffice.

 

[Jdiesel87]

Project has been slow going the past few weeks. I received some Type E crossovers that I will harvest the autotransformers and 2.5mh inductors from. The plan is to go with a Type AA crossover. I haven't fully decided on the remainder of the crossover components yet but I will likely go with some cheap metalized polyester capacitors and a 0.245mh air core inductor for now. Capacitor upgrades can come down the line if I get bored.

I also have a pair of K-55-V soldered lug drivers on route that should be here next week. I will bite the bullet and get some new K-33-E woofers and be done with it I guess. In the end the cabinets and the EV T350 tweeters will be the only original parts but these will pretty much be Klipschorns when I'm done.

The only thing I am a bit uncertain of is how to bring down the tweeter a db or two if needed as I hear the T350 runs a db hotter than the T35 or K-77.

 

[absolve2525]

Project has been slow going the past few weeks. I received some Type E crossovers that I will harvest the autotransformers and 2.5mh inductors from. The plan is to go with a Type AA crossover. I haven't fully decided on the remainder of the crossover components yet but I will likely go with some cheap metalized polyester capacitors and a 0.245mh air core inductor for now. Capacitor upgrades can come down the line if I get bored.

I also have a pair of K-55-V soldered lug drivers on route that should be here next week. I will bite the bullet and get some new K-33-E woofers and be done with it I guess. In the end the cabinets and the EV T350 tweeters will be the only original parts but these will pretty much be Klipschorns when I'm done.

The only thing I am a bit uncertain of is how to bring down the tweeter a db or two if needed as I hear the T350 runs a db hotter than the T35 or K-77.

Looks awesome! Can you use the tweeter level controls you already have? Just wire them to the screw lugs on your eventual crossovers that you put together. Otherwise parts express has nice 8ohm l-pad level controls with longer shafts.

 

[Jdiesel87]

Looks awesome! Can't you use the level controls you already have? Just wire them to the screw lugs on your eventual crossovers that you put together. Otherwise parts express has nice 8ohm l-pads with longer shafts.

Yes but its not quite that simple from my understanding. I haven't measured my existing L-pads but I believe they are 8ohm. I think the L-pads are essentially adjustable swamping resistors. It can be done but it doesn't seem to be very common with Klipsch crossovers, possibly for good reason. Maybe @Deang can speak to the benefits/downsides to using L-pads on the Klipsch networks.

 

[Jdiesel87]

It's been a few weeks but I finally have some progress to share. First to go were the squawker drivers which made committing to a crossover much simpler. I had originally planning on sticking with the EV drivers but since they were 8 ohm it added unnecessary complexity to the crossover design and would have required something fully custom. In the end I was able to get a pair of K-55-V's and this solidified the path forward by sticking with true Klipschorn parts for this build and being able to stick to a tried and true end project. These are the soldered lug version which "likely" have have the dual phase plug and reduce the 9 khz spike that some Klipsch drivers are known for.


I also replaced the woofers with new Klipsch K-33-E woofers to start fresh. The original woofers were 8 ohm whereas the K-33-E's are 4 ohm. I spend an entire day scraping RTV sealant from the old woofer's mounting screws while doing my best to not strip the screws while working in tight quarters. I'm happy the woofers are replaced and hope I don't need to replace them anytime soon. The K-33-E drivers in the Klipschorn bass cabinets are a combination that just works so I quickly abandoned the idea of using "upgraded" drivers.




The EV T-350 tweeter is the only original part that I'm carrying over from the original speakers besides the cabinets. The T-350 is essentially a T-35 with a bigger magnet that is more efficient and plays higher. The K-77 tweeter is just a cherry picked EV T-35 tweeter. This can be considered an upgrade but it doesn't come without it's own challenges. The T-350 will likely run about 2 dBs hotter than the K-77. I will need to test it out and see how I like the sound but it may require some minor crossover modifications to reduce the output.

I ended up finding a pair of Hersey Type E crossovers that I was able to modify into a Type AA crossover quite easily. The autotransformer and the inductor on the woofer circuit is the same so it just required adding a few new capacitors, adding a 0.245 mH inductor on the tweeter circuit, and changing the squawker taps on the autotransformer. This turned out to be much more cost effective than purchasing a new crossover from Crites and has the benefit of staying true to the specs of the original T2A autotransformer. I choose Solen metalized polyester caps for the time until I can decide on what direction to go. Polyester are typically recommended over polypropylene caps. I will probably experiment with some boutique film caps eventually but the Solen caps will be my baseline for now.


New vs original crossovers


Everything is hooked up and confirmed working but I still need to rearrange some furniture and get these into their new homes in the corner of my room. Replacement speaker grills are on the list of finishing touches but that can wait a bit. I will be powering them with a Yamaha integrated amplifier for now but I'm on the hunt for a nice SE tube amp to complete the setup.