Is there an ideal shape for Karlson front chamber?

[freddi]

if one is trying to build a usable (other than firewood) Karlson type, is there certain aspect and front chamber shape/deflector, etc. which gives better result than others?

one builder (who rarely posted at Ulfman's old Karlson speaker forum) claims the front wave goes up then back down while its being released.

how does baffle tilt really affect things? is the coupled cavity peak pretty much predictable from looking at the 3rd impedance peak region of traditional Karlson? (~155Hz in K15, 224Hz in Acoustic Control's 115BK)

K15 from 1951 used a front shelf to deflect and null a dip around 250 but techniue probably too rough for smaller boxes. I've had 23 degrees baffle and 10 degree slant board do "ok" in a 6.2 cubic foot bulk coupler.

a damped stub might be added to the front chamber at top to smoth ripple and lower the 3rd Z peak (if needed). adding a 6" high fold-over stub to one coupler see-sawed its response about like simple bandpass simulations would indicate based upon the Z plot. --- not sure about stored energy effects in the added stub.

these things can play loud without much cone excursion but that may depend upon certain relationships. that part is generally easy - one wants them to play acceptably on most recordings and that can be tough.

anyone here brave/curious enough (besides Magnetar - lol) to go into the realm of k?

small coupler for 15" - IIRC builder used 25 degree/10 degree and then tilted deflector and HF waveguide down ~35 degrees

I had an 1844 Martin like this builder used in this coupler below (showing K33E) but mine was rough imo - my coupler had different reflector. 1844.15269/151269 has great cone but high Le and fairly high moving mass.

[PeteMcK]

Freddy,
depends what you mean by 'better'?
You are actually probably in the best position to answer the question for traditional K's, with all the graphs you have....
(How about a summary table?)

However, I would like to see more non-traditional Ks built (taller, different aspect ratio, etc), to get a wider perspective.
Magnetar & Forsman have shown the idea can be used in different ways.

The main thing that isn't understood well, I think, is the effect of the cross-sectional area of the pipe. Should we follow TL theory here?

Unfortunately time & $ preclude more building for me (gotta find a new job next year)...

cheers,
Pete McK

[Empee]

Hey there!


SUPPOSE i got a cool pair of 70's Philips 10" AD1065's,
and i wanted to put them in Karlson enclosures,
what would be the best design ?

I've seen Karlson drawings with upright (vertical) inner plates,
with tilted inner plates,
with grooves in that plate, or
with one wide slot,
with a wide shelf between slant plate and upper board,
with two small shelves at either side leaving only a gap in the middle,
with a shelf at the front side (just above the rim of the speaker)

??


I'm just curious,
as a pair of Karlsons is gonna be my next speaker building project....

[freddi]

hey back ! -

a 10" on adaptor board in K10 might work (?)

do you have AD1065 T-S parameters? if so, you might use WinIsd badpass model to get rough idea of low end and peaking (if any) by looking at a Karlson Twelve setting rear chamber to ~1.25 cubic foot tuned to about 60-65Hz, front chamber to about 0.625 and play with front chamber tuning around 200Hz region until a 3rd impedance peak of around 225Hz appears in the simulation.

I think a 10" coupler could be narrower than K12. A cheap test box with variable baffle tilt and removable port panel and mucking with upper deflector might help dial in tone.

one builder had a tall/ narrow K10 and ran Scan-Speak and JBL 10 during testing - the front pipe wasn't much wider than the driver's frame and height was around 28" - shelf , reflector and several sets of wings were all removeable for testing.

heres that builder's K10 (never heard) - I'm sure later on that the slot was run all the way up to the top with a narrow V-slit and that would give a faster sound - this K10 might like a pretty strong motor



front shelf in couplers under K15 size will probably mess up things worse and front shelf didn't appear in Karlson's originals other than K15.

the 1955 k12 had 30 degree baffle, flat port board and a 45 degree deflector at top. The later K12 had 10 degree slant board and 25 degree baffle then a plan on ebay indicated there was a 25 degree model with ~ 6 degree slant board. There was also a factory K12 with 30 degree baffle, 10 degree board and 45 degree baffle. The outer box dimensions remained the same for all these K12.

wtih higher Qts woofers a distributed slit (or holes) vent will give better damping and "faster" bass on drum with less resonance than a single vent.

a slight cant for board above baffle might be helpful.

I have a 30 degree 10" coupler loaded with Eminence 10cx which does not sound as good as would like but looks pretty and makes noise - too bad it wasn't prototyped to satisfaction but I[ve no saw setup - the builder did great job - here's that coupler with a temporaray vent board replacing the normally finished baltic birch vent board

[Empee]

hey Freddi!


My appologies for not being on site lately.

However, the K10-plan still exists so i'm looking for the best dimensions to build them.
i haven't fount T/S parameters to the AD1065/M8's yet, but so far I've found a fs of 55hz
and a QTS of around 0.63 (same as about all other 10" Philips full range drivers of the time?)

I did some web-searching and dived into some litarature,
gathering pieces of the puzzle.

Looking at Ulfman's page, I found 2 15" designs, 2 12" designs and a 8" design,
but no K10.

My initial 'gut feeling' says to go with the Popular Mechanics K12 design as it has
a tilted slant board w. slits as apposed to one reflex opening, dampening the reflex better as you say.

Might it be an idea to make the slits very wide (accross the complete board) and to
make 'sliding doors' behind them so i can vary the opening / crossection of the vent ?

What influence has the degree of tilt of the port board?
I saw a sketch in Ulfman's picture gallery where the port board is not tilted but
curved! Now is that the way to go ?


Looking forward to your opinions,

Thanks in advance!

empee

[VintageToo]

About the AD/1065 M8 drivers...
Pardon me for entering this thread, I also have a pair of AD/1065 M8 drivers that were in some terrible homemade boxes with a pair of Philips tweeters. The result was very shrill.

Empee, did you find parameters for your drivers? I can't find any general listings for Philips drivers and am not equipped to measure them. I saw specs for the AD/1265 M8 that claimed 18000hz. If the 10's are close to this they should sound nice. I'll pair with a sub-woofer so am not worried about bottom end.

I expected they were intended for a sealed box like the old Philips kits I have picked up along the way.

Any help or suggestions would be appreciated.

Thanks!

[Empee]

Hi VintageToo,


Here's a scan of a 1983 Philips booklet

unfortunatly, there's no Qts on it,
but I can measure that tonight.

here's scan #1

[Empee]

scan #2


wait for my measurements,
will post later tonight........

Cheers!

Empee

[Empee]

Hi !

average of the two AD1065's I've got:

Fs: 60Hz
Qms: 5,90
Qes: 1,21
Qts: 1,00
Vas: 101,45 liters


So you see, they differ a bit from the specs given


I'd say; open baffle !
afterall, you mentioned the use of a subwoofer.....


Cheers,

Empee

[VintageToo]

Thanks Empee!

I'm going to play with the open baffle approach for starters. What did you do with your set?

Bernard