Karlson K-15 what driver?

[mightym]

I'm interested in playing with a Karlson, K-15.

I do not however wish to go fullrange, or coaxial.

I'm curious to experiment with this either loved or maligned enclosure.

This has to be done on a strict budget, I can't afford to spend $500 on a single bass driver. My budget runs to more like $100 per bass driver.

Can someone help me with some T-S parameters suitable for this enclosure, so I can select a driver that is within my budget.

My plan is to combine the K-15 with a Horn Mid/High driver for a 2 way.

I am totally and completely open to encouragement, help, or constructive criticism. Naysayers will be cheerfully ignored. If, when I'm done, I don't like what I built, I'll recycle the drivers and barbeque the cabinets.

John

[audiokinesis]

I am under the impression that with a Karlson, you don't need a whole lot of x-max but you need a woofer whose response doesn't "sag" in the bottom end like modern low-Q prosound woofers do. The old Altecs were good in that respect.

If this is true, then I think the Selenium WPU-1509 is a good candidate for a Karlson. In a 3 to 6 cubic foot box, with appropriate tuning, there's less than 1 dB sag (and no peak) in the bottom end - it holds up fine until it starts to roll off (no "shelving" or early rolloff).

Here are the parameters; try modelling in 3-6 cubic feet tuned 42-39 Hz:

Fs = 36 Hz
Qes = .35
Qms = 14.7(!)
Qts = .35
Vas = 164 liters

And, here's a link:

http://www.selenium.com.br/site2004/...09-slf_new.pdf

Now from what I understand a Karlson doesn't behave like a conventional reflex enclosure, but looking at the behavior of the Altecs it looks like their low-end response followed this pattern. If anything, I think the Selenium might go a bit deeper than the Altecs, at the expense of a dB or two of efficiency.

I welcome comment or correction from those who know Karlsons better than I do.

Duke

[Magnetar]

The two best drivers I have found for Karlson Klams is PHL 5320 and Altec 921-8a

Best person to ask is Freddi at The Karlson Forum.

[mightym]

Thanks for your reply's Duke, and Magnetar.

I looked for altec T-S Parameters for several hours yesterday, guess I should have looked on the "unofficial" site too...

Got Your E-mail Duke, responded, then decided to check you out. Nice webpages, excellent reviews on your products from several sources. aleveiated any doubts I may have had about the veracity of your offer.

Magnetar, I've seen freddi's pawprints all over the Karlson pages here. I hope that he will weigh in, as I would like to pick his brain too. I have in mind building them with inexpensive materials in a manner that will allow me to adjust the internal bits to experiment. then build a visually presentable cabinet when/if I'm satisfied with the sound.

[sreten]

http://home.comcast.net/~jhidley/

Hi,

There is a very nice Jensen type 15" on the above link.

TBH with a horn for the top end midrange response becomes very
important, if you cannot measure then get a driver that is at least
specified to be flat in the midrange, many 15"ers are anything but.

Or easily controllable e.g. : http://eminence.com/pdf/delta-15b.pdf
Which is easier than : http://partsexpress.com/pdf/DC380-8_specsheet.pdf

Worst of course is if you have no idea of the response ....

/sreten.

[mightym]

Sreten, thank you for your reply.

It's been too wet for me to work today, so I've been reading all the material I could find on Karlson and his design. Looking for all available plans for the K-15. There were several minor changes made that I've been able to find up into the late 1960's.

I think that with any luck I'm making a deal with Duke at AudioKinesis to purchase a set of Seleniums that have pretty attractive parameters and a good response. They are certainly better looking than I had imagined being able to afford for the price.

I'm waiting for the moderator over at the Karlson forum to approve my membership and plan to post over there too.

John

[mightym]

I whipped up a Sketchup of a K Kab, with variations per JK's newest patent.

There's a dutch builder who's completed one like this or similar to it anyway, who seemed to be very pleased with the results.

This isn't in any way final result, just wanted to put up an image.

[kenpeter]

Of what I got spec sheets handy (this is far from the complete list)

B&C 15PH40, 15NDL76
Emininence Delta-15A, DeltaLiteII-2515, Kappa-15A, KappaLite3015, Legend-CB15
PA BlueMonster15-CXHA

I've got reason to believe a Sigma 18 might be shoehornable...
4xBeta8's or 4xSammi's with room for a horn in the middle....

A pair of 10's side by side is just too tight, no meat left in the
middle after the holes are cut... Unless your K15 also deviates
from the original width to permit that option.

I've seen a horn mounted in the "shelf" facing up into the top half of
the koupler... That works OK, and maybey even helps break up the
short path around the middle that causes the 250Hz "dip".

I'd go big on VAS, high on sensitivity, high on EBP.
Low as possible on all Q's (including the mechanical).
Low coil overhang (Meaning low XMax and low Le)
Lightest moving mass you can find... A few rings in
the cone are usually a good thing. A cone thats all
ripples is probably too heavy.

The air mass of the coupler will attempt to Lower Fs if the cone
isn't allready too heavy, but the springy air in the box behind the
cone will certainly raise both Fs and Qts... Its a trade that Karlson
balanced extremely well.

I'm running only a DeltaPro12 in my K15 now, not lacking for bass,
which is absolutely astonishing.... Martin 1114 might be a good 12"
choice (the old Eminence coaxial).

Some of the spec sheets may show an on-axis peak. You can bet
there is an equal off-axis drop even if they don't show that detail.
The slot may be helpful evening out the midrange dispersion.
I don't necessarily believe a little rise before Le cutoff is as bad
when seen through a Koupler...

[mightym]

Thanks for the info Kenpeter, I' probably going to top mount a waveguide of some kind, although Freddyi over on the Karlson discussion is trying to convince me of the efficacy of the " tube " mounted above the shelf.... I'll probably try it, but primarily now I will use the Koupler as a bass cab.

I've been following the thread over at Audio Karma about the Econo waveguide JBL has out and the relatively inexpensive Comp. drivers from Selenium. I'm also considering the Smith distributed source horn ( 'cause I like working wood, and I can " make " that one ). It has a very wide dispersion capability to hopefully match the Karlson Kabinet.

Duke Lejune has offered me an attractive pair of discontinued Selenium woofers, and opinions vary as to whether they are suitable, in fact they're pretty evenly divided.

Decisions, decisions....

John

[audiokinesis]

MightyM,

It looks to me like those with more Karlson experience than myself are recommending woofers whose parameters go in a very different direction from the Selenium. If you were doing a straight-forward reflex box the Selenium looks quite good, but now I'm not confident that it would work well in a Karlson.

A great deal on the wrong woofer is a lousy deal in the long run, and it looks like that's what I was offering you.

Duke