Jensen Coaxials

[widman]

I acquired a set of Karlson speakers from my father-in-law, mainly because no one else in the family was interested. They have a great vintage look, complete with a blond wood-grain formica finish. Unforunately I wasn't as impressed with the sound. Lots of boomy bass.

I opened the cabinets and found 12” Jensen Coaxials inside. They are rated at 16 ohms and seem to be in pretty good shape. Inside the speaker frame, behind the terminals, it looks like they have a small crossover and a 50 ohm pot is wired into this section. I know they don't qualify a full range speakers, but this seemed like the best place to get some information on them. Is there a better enclosure design for these speakers? Any info or comments would be appreciated.

pete

 

[widman]

Another view.

 

[rcavictim]

Given their vintage those may work well in a large infinite baffle sealed enclosure of 5-9 cu.ft. Arrange the driver height to put the tweeter horn about 36 inches above the floor.

I`ve been playing around with Bozak B199, 12 inch vintage alnico woofers and that is what they like, a 4-8 cu.ft. sealed box. Bozak literature claims the 8 cu.ft. is the best.

Different amplifiers will also likely give you different sound. Experiementation is the path to audio nirvana.

 

[Geoff H]

Hi Widman, that looks like 15" to me, hard to read the tape. Is there a model no? Looks like a P-15LL with a horn added.

 

[widman]

It is a 12" speaker. There are a few numbers printed on the frame, but I'm at work right now. I'll check them out tonight and post them.

Thanks,
pete

 

[widman]

I opened up the other speaker and pulled out the driver tonight. Turns out it looks slightly different than the one posted above.

Here is a description of each coaxial driver:

1.
12" driver with a brown frame, marked ST 875 H222 C6015-3. Also has the number 220845. The back of the magnet cover says "Coaxial Loudspeaker" and "High Fidelity"

2.
12" driver with a blue-gray frame, marked ST 875 H222 C6015-2. Also has the number 220620. The back of the magnet cover says "Wide range" and "Low Frequency".

Both drivers have a similar segmented horn and a potentiometer that is connected to the cross-over behind the terminals.

I listened to the drivers again in the Karlson enclosures. Very bass heavy and the upper range sounds veiled. Vocals especially have an echo. Tomorrow night I want to crank them up (before the kids go to bed) and see how they sound loud.

I'm sure they would sound better mounted on a proper baffle. I've found some info online about using this type of driver on an open baffle, so maybe I'll give that a try first. Definitely the cheapest experiment, although not the most wife-friendly.

Any information or hints would still be appreciated.

pete

 

[Geoff H]

The six digit code is a date code, but they didn't include the decade. They probably thought no one would be interested 40 years later.
220845, year 8, week 45. 220620: year 6, week 20. My guess is 68 and 66. esp if they have alnico magnets. The other numbers don't match with any of my data. The could have been OEM for Karlson.

Try here. www.oaktreeent.com/Jensen_Speaker_Parts.htm They may have info on them.

 

[tomtt]

I opened the cabinets and found 12” Jensen Coaxials inside. They are rated at 16 ohms and seem to be in pretty good shape.

pete

Best with a Tube amp

these are truly valuable


http://images.google.com/images?hl=...m=0&q=jensen coaxial&ie=UTF-8&oe=UTF-8&tab=wi


http://history.sandiego.edu/gen/recording/jensen.html

 

[tomtt]

here is an h222 w/altec515's

 

[freddi]

Do your Karlson still have their logo decals? - if so do they read
"Karlson" or "Ultra Fidelity by Karlson"? I'd like a clear picture of the logo if latter.

do they have 3 damping pads? 1" thick at top and bottom and ~2" thick under the rear shelf? - sometimes a piece of jute or similar on the back panel will help and I think Karlson suggested a bath towel. A dowel strut jammed between the rear shelf and back panel can cut down some boom. Karlson can have some tubbiness but should play very clear drum transients without much cone movement and dryly recorded vocals can be clear.

Are they cutout for 15" but use an adaptor? IIRC 15" work better than 12". FWIW you might pidde with vent width. Normal old K15 had ~4.5" by 9" port. Supposely 15" Jensen coaxial are very good in K15. Freddy

 

[widman]

The enclosures have the "Karlson" label;

 

[widman]

There is padding on the back panel, behind the driver:

 

[widman]

There is also a piece of padding on the bottom of the enclosure.

 

[widman]

Here is a picture of the baffle in all its glory:

 

[freddi]

ahh - looks like you have Karlson Twelve and not 15" model. Is the vent a horizontal slot? Let me know if you wish to sell the cabinets alone. If they're 12 then lower limit will be about 70Hz before rolloff and qts will have to be pretty low to keep peaking down.

whats the box dimensions ???? is that one piece of trim the worse spot?

Freddy

here's a 1955 K12 with adjustable damping bar adjacent to the rear shelf - I see it on your cabs back too

 

[widman]

Re: Re: Jensen Coaxials

Best with a Tube amp

these are truly valuable


http://images.google.com/images?hl=...m=0&q=jensen coaxial&ie=UTF-8&oe=UTF-8&tab=wi


http://history.sandiego.edu/gen/recording/jensen.html

I've seen ebay pricing of similar drivers, but I'm more interested in trying these drivers in a different setup.

Thanks for the second link, I love the history of this hobby.

pete

 

[freddi]

that vintage grill cloth alone doesn't help matters - your Jensens should sound fine once right cabinet is found. I stupidly cut the grille cloth off my lone K12 to make a drawing

 

[widman]

ahh - looks like you have Karlson Twelve and not 15" model. Is the vent a horizontal slot? Let me know if you wish to sell the cabinets alone. If they're 12 then lower limit will be about 70Hz before rolloff and qts will have to be pretty low to keep peaking down.

whats the box dimensions ???? is that one piece of trim the worse spot?

Freddy

here's a 1955 K12 with adjustable damping bar adjacent to the rear shelf - I see it on your cabs back too

Yes, it is a 12(" driver). The dimensions are 16-1/2"w x 13-3/4"d x 25"h. The vent is a horizontal slot, just above the middle brace.

The speakers also came with a set of stands. Two pieces of wood, with 45 deg. cuts, held up by a 3/4" dowel. Looks like this: /--\. The stands raise the speakers about 2" off the floor.

Do you have any suggestions about setting up the speakers for the best sound. Currently I am powering them with a 3886 Gainclone.

pete

 

[widman]

here is an h222 w/altec515's

Do you have dimensions for that enclosure? I've been considering trying an open baffle like:

Open Baffle

pete

 

[freddi]

I;ve not had 222 but looks like it may have high qts and fairly high resonance. you might muck with the position of the tuning bar - my k12 has 3 sets of hole to allow moving it around a bit

looks to me some folks might be using H222 on open baffle - couldn't find Thiele-Small parameters on the web yet

you got the stands = kool

here's The Edge software free for modeling open baffles - I'm not sure how one models floor bounce nor wings so you'll have to ask around

http://www.tolvan.com/edge/