Mini Karlsonator (0.53X) with Dual TC9FD's - Page 16 - diyAudio
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Old 30th November 2013, 03:01 AM   #151
xrk971 is online now xrk971  United States
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I remember that note on the plans for the original Karlson - basically the inside of the wings and front baffle should be as smooth as possible. This is opposite to what what I perceive as smoother highs and better imaging with some fluffy damping right beneath the lower portion of the wings.

You should try it Freddi and tell me if it works. I think in a K15, the high frequencies that I am talking about are not as pronounced because the wings are huge and dealing with the bass and mid bass. The highs typically come from the coax compression driver or a separate K tube tweeter.
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Old 30th November 2013, 03:59 AM   #152
IG81 is offline IG81  Canada
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Quote:
Originally Posted by xrk971 View Post
My mistake, I meant 4FE32 - the 4 ohm Neodymium magnet full range.

FaitalPRO 4FE32 4" Neodymium Professional Woofer 4 Ohm | 294-1120

The ferrite magnet version of the same driver will also work too - costs a bit less.

FaitalPRO 4FE35 4" Professional Woofer 4 Ohm | 294-1123
T/S parameters seem to differ in the 3" and 4" Faital driver lines, between models of different nominal impedance and magnet material. The 4ohm Neo 4FE32 seems the best suited with the lowest Qt of 0.5.

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Old 30th November 2013, 03:54 PM   #153
Greg B is offline Greg B  United States
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Originally Posted by xrk971 View Post
I remember that note on the plans for the original Karlson - basically the inside of the wings and front baffle should be as smooth as possible. This is opposite to what what I perceive as smoother highs and better imaging with some fluffy damping right beneath the lower portion of the wings.
Strangely enough, we've been arguing about this issue for years. There was no shortage of discussion on this matter on the Gregg Baker's old Karlson forum.

Yes, in the plans and notes it was typically recommended that the inside chamber be shellacked to maximize the high frequencies. I think this has a lot to do with the typical drivers people used back in the day, which could easily end up with a pretty serious BBC dip- perhaps more like a BBC canyon.

However, in the actual patent description, Karlson discusses adjusting the tone (or something like that) by varying texture of the interior surface. I'd have to go back and read it, but IIRC he mentions felt or something.

In my relatively limited experience, I'd say a hard shellacked surface does muck up imaging a bit, as well as adding a sort of reverberant quality to the sound that may or may not be desired. The sound gets sort of confused, for lack of a better description. Shellacking the inner surface does (not surprisingly) reduce the HF losses from bandpass effects.

In the larger K15 it doesn't seem to matter as much, as in the smaller K12. If I were to build a new small Karlson type for myself, I would try lining the inside of the chamber with thin cork, and possibly glue some felt right behind the wings in front of the driver. This will probably eat up some HF, and make a rising response horn type specs driver a prerequisite.

Years ago, Ron C shared some interesting data on the reflectivity of surfaces. It was surprising how much difference there was between a rough sanded plywood and a varnished/shellacked surface.
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Old 30th November 2013, 04:34 PM   #154
Squeak is offline Squeak  Denmark
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Also the angle at which the HF reflects off the surface plays a large role too, just as with light.
Read this thread for some pretty good explanations and advice on using selectively absorbant foam lenses: Speaker Directivity - The Gear Page

Last edited by Squeak; 30th November 2013 at 04:38 PM.
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Old 30th November 2013, 04:37 PM   #155
xrk971 is online now xrk971  United States
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THanks X, I did up an excel spreadsheet for scaling, but then realized the picture you posted, I can just print to scale until it is right. With the kids in town for Thanksgiving, and the addition to the shop half done, the build will have to wait a week or two.
I just started on the single driver 0.4x scale Karlsonator this morning. It is a cute little speaker at 12 in tall 6 in wide x 6.5 in deep. Very easy to make out of foam core due to the small size of all the pieces.
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Old 30th November 2013, 06:45 PM   #156
xrk971 is online now xrk971  United States
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Default 0.4x Scale Karlsonator with single Vifa - Build 1

Photo of progress so far. Need to cut out driver hole, add stuffing, add terminal cup and wire, then glue final side panel.
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Old 30th November 2013, 10:07 PM   #157
djn is offline djn  United States
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Very cool X. I am thinking about 1/2" mdf. With its small size that shops be plenty thick. Can't wait to hear your impression of this little guy
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Old 1st December 2013, 01:50 AM   #158
xrk971 is online now xrk971  United States
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Default 0.4x Scale Karlsonator with single Vifa - Build 2

Update of build: driver cutout, stuffing added, terminal cup and wiring. Currently waiting for pva glue to dry on final side panel. Should have first sound tomorrow.
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Old 1st December 2013, 03:54 AM   #159
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You rock X. That is a fast way to build.
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Old 1st December 2013, 04:59 AM   #160
xrk971 is online now xrk971  United States
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Default 0.4x Scale Karlsonator with single Vifa - Build 3 - Completed

The speaker is completed. Here is a photo of it with a CD case for size reference. It is very small and compact at 12 in tall x 6 in wide x 6.5 in deep. This size is perfect for a bookshelf or a desk.

How does it sound? In a word - amazing! It sounds very very good. The highs are clearer than the dual driver 0.54x scale version . I think it may be that the direct radiator cone area is better matched to the Karlson aperture size in this format - or the mid-bass is cleaner? The bass extension is quite nice - not as deep of course as the 0.54x version - but very satisfying. I played "Sermon on the Mount" by Dave Brubeck and his sons - there is a beautiful Cello and it comes through very natural and smooth. I played some Robert Cray and that sounded great. If you pair this with a sub crossed at 80 Hz and below it will really shine - but it sounds great as is. For a desktop computer speaker, it will easily beat a $100+ pair that is out there. The wide angle directivity is very nice and apparent when you step back and walk around the room - it sounds very uniform.

Anyhow, I don't have any reservations about recommending this build. You will not be disappointed. For the cost of a $10 Vifa, 1 sheet of foam core, some pillow stuffing, and a $0.85 terminal cup - this speaker is awesome!

I am very happy with it.

Cheers,
X

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Last edited by xrk971; 1st December 2013 at 05:08 AM.
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