Karlson thrift shop score!

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WARNING -- LONG NEWBIE POST --
Hi folks! Long time listener, but first time caller to the forums here. My hope is that Freddi and others can help me out with my Karlson dilema(s).

I've been following the forums for many years, with a keen interest in the Karlson discussions. Imagine, my dumb luck the other day while walking through my local thrift shop (which ironically seems to always have good audio gear), and I turn around and find a pair of Karlson K12s!

I couldn't pass up the opportunity to actually get a pair of Karlsons, that aside from the "refinishing" someone had done (think watered down brown paint), and a few nicks and dings, they looked really good. So, I snagged them and happily paid for them!

Got them home, and wiped the dust off of them and verified the impedance of the drivers (as of yet not knowing what they are) and both measured 8 ohms on the dot, which is a good start... There are no markings on them (i.e. the gold Karlson script or a plaque), but the cabinets are solid and either the person assembling them was one heck of a shadetree carpenter or these were purchased as a kit from Karlson back in the day and assembled by someone with great care. The wood appears to be of the fruitwood variety (I'm thinking cherry by the grain pattern on the curtains). The only features on the back are an RCA jack for the amp connection, and an L-Pad for adjusting the tweeter.

So, hooked them up to the good ole' Crown D150, flipped on the tube preamp and sat back for some Karlson bliss...Well, that's when I realized, there was bass (and gobs of awesome bass) coming, from only 1 side. Highs filled the air from both sides, but the left channel was only high's, nothing else... Time to bust out the screwdriver and pop them open...

All of the back panel screws were recessed into the back panel, providing for a very nice and clean finish on the back (thus my statement above about the care of assembly). After taking all of the screws out of the back and gently prying the back panel off, I finally discovered the drivers that lerked inside of these cabinets... A Realistic branded Utah Celesta 12 Triaxial driver (both are the same). I took note of a few things before checking on the driver: First my cabinets are not vented, there are no slits vents or the vertical rectangular vent, the top board is solid. Secondly, the entire back chamber is lined with 1" fiberglass that has been carefully stapled into place. Both of those features, seem rather rare, or at least from my reviews of past posts here on the site.

So, now with the "Mystery drivers" issued solved, I checked on the left channel, and gently tried moving the cone...It's seized up, no movement what so ever...So either someone dropped the cabinet at one point and the magnet got jossled, or something else happened (Playing Led Zepplin too loud??) ...either way, this driver isn't going to be working again anytime soon.

Which now leads me down to my "Please help a newbie out" section:

1) Are these current vintage drivers worth attempting to fix/update? One of them is good, the other is not. A local shop here in Denver quoted me just north of $150 to get the broken one fixed via a quick phone call (which may end up being more depending upon what is truly wrong with it)...

2) I am thinking of perhaps doing an Econowave style build with these, using a Selenium/Horn top end as per the E-wave build guides....My goal is to build these into a nice pair of speakers that I can use in my 2 channel setup, to replace a pair of Technics SB-L100 Linear Phase speakers that currently occupy the left and right positions...

3) Which woofer(s) would you folks recommend that I look at the replace the Realistic/Utahs? Since the back chamber is sealed (according to what I'v'e read ~1.3ft3), I was considering the following:

* Used/refurbed pair of KLH Model 17/20 10" Woofers (Can source these locally for a decent price)

* MCM 12" Dual Voice Coil Woofer (as per Freddi in past posts -- how do these sound? Do they sound good up to 1.2-1.6k to crossover to a horn loaded tweeter?)

* Dayton PA310-8 (Given the specs not sure how low it would go -- response plot looks very smooth though...)

I appreciate all of the lively and very informative discussions, and I hope to be able to perhaps start yet another with this post. I will get pictures posted here as soon as I can, once I get home from work tonight.

Thanks!

RFB
 
Pictures

Here are some pictures like I promised...
 

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Founder of XSA-Labs
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Nice find! Would you mind telling us what the low low thrift store price you paid was?

If impedance measures 8 ohms still if means voice coil isn't broke. Probably a stuck voice coil due to debris or some other foreign matter. Take drivers out and see if pushing on cone gently while applying lateral pressure helps to free it up. Maybe Freddi has tips on how to unstuck frozen drivers.

Interesting that it's a sealed design and has good bass. Usually sealed will have roll off at 100Hz. Unless this is a higher Qts driver? But magnet is too big for that.
 
After my veteran discount and such, I paid $30 for the pair...

I had the broken driver out of the box, but it didn't seem to want to move no matter what I tried, but I'll have to try again.

The bass that was present (audible) I'd say based of frequency sweeps starts to get quiet around ~50Hz with the working driver...

Are these drivers worth the hassle of perhaps a rebuild or are their better drivers out there? Once I get a chance to pull the broken one again, I'll post some pix...it's basically a 12" cone with a yellowish fabric surround and a whizzed cone with a massive cone tweeter sticking up through the center (almost blocking the whizzed cone). The working driver is very compliant (floppy) when you move the cone and being a sealed enclosure it seems to hold air pretty well when pushed in, taking a second or two to come back out..

I know Fresdibhas mentioned in previous posts that he's had good luck with the MCM DVC 12 in a K12 with the vents plugged...but MCM doesn't have a response graph for this driver but lists the response as 25-4K (Fs is listed as 25Hz)
 
nice cabinets ! - - I had a pair of Celesta 50-51 years ago starting out with homemade 5 cubic foot reflex which I cut into half to get two cabinets for stereo :D Its said qts is around 0.7 (?) - the cone tweeter was much like Quam, with "spokes" ribbing and perforated metal cover - still remember their sound with an Eico ST40 and Audio Fidelity "Marches from Operas"

it might not hurt to replace the highpass capacitor - not sure where its located


48ck5bX.jpg


https://www.youtube.com/watch?v=SWJ8CHcBM4U
 
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Joined 2004
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Kevin: would the coil still read 8 ohms if it was burned up? I always thought the adage was that if it was burned up it would measure close to a dead short???

Sometimes it gets just hot enough to cause problems with the adhesive on the VC without actually causing a short. What I have seen is adhesive that flowed and glued the former to the pole piece. The other possibility is debris wedged in the gap.
 
Thanks for all the replies! The best I can figure is that these drivers were made by Utah for Radio Shack circa 1969-1975, and rebadged their C12PC3B speakers as the Americana 12". Yes, Freddi these have a tweeter with ribbing on them with a metal grill over the top...Give the sound of the working one, I'm just not sure that it would be worth the hassle (time and money) to fix the broken one..I was rather underwhelmed...they produce music, but nothing special, but they may not be the right drivers for an invented Karlson....

Freddi, you've mentioned in previous posts about the DVC MCM 12 with sealed up vents in a K12, can you tell me more about that experiment?
 
if it's burnt, it will likely still smell burnt as the voice coil is large.
you may be able to get some contact cleaner in there that might loosen it up.
if you need to you can make a small hole in the spider as close to the outside edge as possible to stick the contact cleaner hose through.

otherwise you can find a driver at parts express that fits the opening and adjust the crossover if nesscessary
 
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that Fane with port sealed/reduced to aperiodic , would be good in the vocal range- it probably would seem bass lacking to most ears

some 8" work decently in K12

Visaton BG20 used to be $23 but now up to $37 ea. They could use a helper tweeter https://www.parts-express.com/visat...XYZ_Products_Exact&utm_group=292-548_E_E20-50

FostexFE206EN are clear sounding overall - strong motor - - Audio Gradient AX08 despite higher Qts need a BSC to tame top. The port would need to be reduced/stuffed

Some 10" work well enough but success with coaxial depends upon the crossover blend.

There's an Eninence 10" bass guitar woofer at Ebay with 54oz magnet for $49.95 shpiped - the backplate is not vented - its a bit stronger than a Delta10 and may behanve similar - I'll been sick and not felt well enough to measure it.

There's two older Beta10cx at Ebay - those have stronger motors than the current model - the would need crossovers and compression drivers.

A compressoin driver and K-tube can be mounted on top for two way Ks.

Strong motor 12"s such as Delta12A are pretty good in K12 - don't expect deep bass - but there will be punch.

Some speakers can be used with the back chamber sealed.

MCM Part #55-1465 Dual voice coil 12" woofer $45.65ea (MCM offers discounts which can help)- same as used by the late Marshall Leach in a sub-sat project. Will work sealed - not sure how good its midrange woiuld be in 2-way. Should go ~40Hz F6-F10 in-room.
Specifications::
Power Capacity: 100W/200W RMS/peak (per coil)
Sensitivity: 93dB (W/M)
Impedance: 8ohm (per coil)
Re: 5.8ohm (per coil)
Le: 0.59mH (per coil)
Frequency response: 25Hz~3KHz
Fs: 25Hz
Qts: 0.30
Qes: 0.32
Qms: 3.13
Vas: 203.81 (liters)
Xmax: 5.0mm
 
Hey xrk971 - take a look at what data I have for that MCM DVC 12" driver and tell me if you think it would make to a K-tube with compression driver.

Its specs are pretty much as published - "Qtc" in a standard K12 with vent sealed with tape and no damping material at all would be around "1" with system resonance of ~53Hz - if vied like a direct radiator sealed box.

the mic was laying on the floor in these response traces - I was interested in it as a "helper woofer" and it seemed to have decent punch and depth

I only ran the MCM DVD 12 for brief evaluation


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Hhmmm, that response plot doesn't look to good as far as that driver making it to a 2-way...Looks like it would work better in a 3-way or as a "bass augmenter" (similar to what the old Hawthorne Augie drivers did for open-baffle)...

Given that the current drivers (aside from one being non-functional) are only mediocre soundwise, I'm thinking it may be best to look at something along the lines of a 3-way horn setup (or perhaps a K-tube systems) or building some smaller K enclosures and using those up top, with a bigger woofer in the K12? Thoughts?

Also, being as my enclosures are unvented, what are the thoughts on a "parallel" tuned Karlson vs a "series" tuned? Anyone try this yet? I remember seeing one member that used furnace filters as aperiodic venting out the backside of his K12...

Thanks again all, for your thoughts, ideas, suggestions!
 
I also found another MCM driver 10" Die Cast Pro Woofer (55-2981) that has been used successfully as a midbass/midrange for open baffle...

It appears someone on the MCM site even ran a box calculator for a 1cuft sealed box tuned to 67Hz (which I think is close to the Karlson tuning IIRC) putting it ~ -6dB at 51Hz which may work for me as well...

Since it's not a K15 and not ported I'm thinking 50-60Hz is about as low as I'll be able to go with these boxes without rework...

Although a 3-way setup wouldn't be too bad either, but I do like the looks of the other Ks on here with just a horn on top (2 way) they do look sharp...and my wife even really likes the looks of the cabinets to, so high WAF is a good thing!

For a mid range, how do Smith horns sound? I'm new to the whole horn thing, so I don't have too much experience with them...
 
a Smith distributed horn type generally has to be pretty big to go "low" - the original one inch format version sounds very nice - perhaps partly due to inert nature from the dividers and wood construction (mine are 3/4" plywood) - they are popular in mono setups

Karlson work well with coaxial and good fullrange - I like reasonably strong motors - like 54oz magnets for 10" 80oz for 12" with published sensitivity around 99dB or so for a 12 - I have 12" Eminence coax with 109oz motor but their sensitivity is only about 96-97dB due to a pretty long overhang on their 4 inch diameter coil - they still sound pretty good with such program as Fritz Wunderlich's DG lieder. Mms ~53g for the 4 inch coil 12cx.

Some higher qts speakers sound good in K12s - a vibrant midrange is important - I've heard nice vocals with vintage speaker having high fs and Qt around 1 or even higher (many old drivers have stiffened raising Fs a half to whole octave)- that's where small spiders, small coils and low mass come into play vs heavier cones which can produce bass

MCM has a lot of speakers with wonky specs - best to find reviews where they've been tested

one reviewer tested that MCM 10

RE(DCR) = 6.5 ohms......... FS= 57.87hz ........ QTS=.861 .........QES= 1.153 .........QMS=3.401.....LE=.58 (10khz) ..... MMD= 37.18 .....VAS= 31.998 ...... SPL= 89.13 @1W/1M (would improve with higher motor strength) ...... BL factor = 9.15

I would probably use regular vented K12 crossed over to a sub at 70Hz - a pym1298 - (about the same as a Kappa12a) sounds more exciting in the midbass than my Klipschorns - a K-tube and inexpensive compression driver work.,

I have an old Eminence B102 (pleated surround - stronger motor than current B102) in a slit vent K12 - its a lot of fun with a K-tube on top. Drum beats barely move the 10" (Qts ~0.23) I had those 10's in my Zu-Druid knockoff.

What are the dimensions of your K's vent? - is it scaled from K15?


Here's a bass guitar 10 for $50 shipped which models well in horn I had built - - the back plate isn't vented - it may have
response like an Eminence Delta 10 - it has a 2inch col vs Delta10's 2.5" coil


05-RE OHMS 4.33 13-FS HZ 52.22

06-LE MH .74 14-MMS GMS 25.60

07-QM 2.94 15-CMS mm/N .3622

08-QE .250 16-RMS NS/M 2.8583

09-QT .230 17-VAS LTRS 68.19

10-XMAX MM 3.00 18-SD SCM 366.10

11-BL TM 11.99 19-EBP 206.2

12-EFF % 3.70 20-SPL dB 97.7



http://www.ebay.com/itm/10-Eminence...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
 
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My K12s aren't vented, the top panel is solid plywood. The back chamber is fully lined with 1" fiberglass.

External dimensions are the same as the Popular Mechanics dimensions, including the slanted feet at the bottom (mine don't have the wood dowel in them though)...
 
unusual someone made them sealed - - Karlson offered a K12 Kit with blank port panel - a friend thinks there were instructions on how many holes to drill for specific speakers

do you K12's have the rear shelf like this factory kit?

approximate dimensions from kit instructions illustration (they were made of 3/4" particleboard)

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as supplied for Tannoy Red
ZxGbIup.jpg


can xrk971 "shut off" the vent easily in his K15 model ?
 
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