cone loading as in Karlson ?

[Empee]

Dear all,


I've been following all threads and ideas about Karlson cabs with great interest,
although I still don't understand the benefits of what I call "cone loading" using
the reflex-wave (or is it essentially a folded TL instead of a reflex cab ?)

I was just sketching some ideas and came up with this....

What would happen if you'd make a folded voigt, and projected
the terminus at the cone ?


cheers,
Empee

[PeteMcK]

You're right, it's a folded TL.
The benefit of Karlson loading is some gain in LF efficiency,
at the expense of some peakiness higher up.

Here's my version (not Voight though):

[freddi]

dunno - looks to me would be similar to truncating a Karlson's wings. A traditional Karlson has a final wedge shape with decreasing volume while the slot's area is increasing.

certain baffle angles with certain height may make smoother graphs than other.

here's a 30 degree coupler not too far off from K15. sounded a bit better than the plots indiacates. I could get smoother plots with 23 degree baffle at 32" height.

cone motion seems reduced in some cases. resistive vents might cause offset problems at higher input power.

8CF box with oid 18"

http://img470.imageshack.us/img470/2...frazjpgxy0.jpg

http://img205.imageshack.us/img205/8074/8cfshelfcr8.jpg

http://img205.imageshack.us/img205/4654/8cfuirce5.jpg

http://img205.imageshack.us/img205/3452/8cfpkb2.jpg

http://img470.imageshack.us/img470/8...onejjpgoi4.jpg

http://img281.imageshack.us/img281/469/34hz3rd6xv.jpg

http://img178.imageshack.us/img178/1...830vrms0lm.jpg

[Empee]

Thanks for the replies!

The picture for me is getting more clear every time I think of it.

Here’s what I think and correct me if I’m wrong:

The waves of the back of the driver go up in the back-cavity of the cab,
then fold over through the slot(s) and travel back toward the cone in the front cavity.

Now the back of a cone is in anti-phase, and the length it has to travel through the
cabinet gets it ‘in-phase’ so-to-speak.

If the direct and in-direct waves are in perfect phase you’d get a theoretical 3dB boost
(twice the energy) but when the waves are in perfect anti-phase you’d get a theoretical
complete cancellation !

Now the reason there’s no complete cancellation is because there’ll be always some
energy absorbed by the cabinet so the direct and in-direct waves will always
differ in energy and when it’s not exactly the same there’ll be at least some output.

Could this be when the K15 in your post displays such a dip @ 250Hz ?
Partial cancellation due to anti-phase cone loading ?

If the above is actually correct, the place of the dip should change with cab size,
at least the position of the slot in the dividing board.

Making the path of the backwave longer or shorter should make a difference….

Should I make a K15 with a narrow slot (vertical) which opening can be moved
up-and-down to see if this has effect on overall response ??

maybe Freddi has already got enough graphs to compare ?

[moray james]

this cabinet was designed for a Fostex FE166E and will also work with the FE167E.

[freddi]

here's a coupler with 85L rear chamber, 23 degree baffle, 10 degree reflector and a stub attached to front pipe - a mod/simplification of an idea by KenL
http://img142.imageshack.us/img142/4...wjpg1cofr0.jpg

here's response 1/6 odtave smoothing at ~ground plane perspective with 18" speaker - note how tilting the cabinet forwards affects the graph dip(s) depth
http://img78.imageshack.us/img78/7889/tilt18mr3.jpg

this 18" had factory spec of Fs ~30, qts, ~0.25 and mms ~103g

other perspectives look a bit different

adding the 6" cap moved the 3rd Z peak down givng ~2dB more on low end and maybe 2dB less somewhere else. My kluge was flimsy & flexy

I want a lot of power out for a lot of power in and not much cone excursion at 300W peaks

a 1.5" piece of pvc was used for a k-tube HF thingy

the degree of subjective reverb might be adjusted by reflector style, aperture flare and starting gap width. Opening the gap to 1.2" on coupler above sans stub sounded very good trying to push 18" or 15" wideband. to a Smith horn on top. This moved Fb up a few Hz so there's a juggling act to maintain Fb via rear vent tuning (and subbjective matters) plus lost a dB or so on the bottom - perhaps part of that was not having the wave forced down to the "floor" as much vs a 5/8" gap - ?

a wide gap might not work on some coupler - I like K's effect on a good day

subjective note of two gaps on a 21.25" wide coupler 32" tall loaded with 18" - same set of wings but swiveled at top on its cleats to provide a different opening gap and flare in the coupler's upper half. (the main semi-known k-guy with higher math abilities said my 1.2" gap was too wide to "load")

http://img236.imageshack.us/img236/6959/badgappx7.jpg

http://img236.imageshack.us/img236/5387/goodgapga1.jpg

K15 with M151 vs RCA-Fan's V-vent box - V-vent has Fb close to 41hz
http://img285.imageshack.us/img285/6...k15m151xs5.jpg

i "think" k can have less cone motion then reflex equivalent to theri rar chamber size and tuning

[Empee]

Great design Moray !!!


But as I see it, the cone will not be loaded by the waves comming
out of the TL path

And as I see in Freddi's reply, the tilting of the baffle (or even the complete cabinet)
aswell the top-opening of the flares has an effect on sound, but not so much on the low-end...

However, my intentional questions were about the cone-loading-principle

Anyone got a K15 from wich they can plug the ports and do measurements?

(eg. make a closed cabinet with a Karlson front chamber?)


cheers,

Empee

[freddi]

Hi Empee - here's two graphs of K15 with port blocked

LF K15 port open then blocked with cardboard (other cabinet was "x15" = 43% smaller than K15)

http://img71.imageshack.us/img71/5237/k15lfpobyn5.jpg

Midrange transition K15 port open then blocked with cardboard

http://img71.imageshack.us/img71/708...500wjpgkd2.jpg

K15 moderate-high Q woofer vs lower Q woofer
http://img132.imageshack.us/img132/6...xvsm1518sv.jpg

K15 beta 15CX vs 50Hz reflex the size of K15's rear chamber - Note reduction in modulation sidebands
http://home.earthlink.net/~buddhaboy2/doppler1.jpg

Freddy

ps - heres a sealed klam w. 18" - samller set of wings giving big gap got ditched so can't examine effect on Z

http://img186.imageshack.us/img186/7...wq18jpgmx4.jpg

http://img91.imageshack.us/img91/654/klam18gap5pb.jpg

[Empee]

Dear Freddi


Sorry I haven't been on this site lately,
although I looked at your reply a few times and thought about it...

I find the first two attachements of your reply the most interesting;
it seems by blocking the port the dip @ 175Hz becomes less, wich would
mean the cone loading has a possitive effect, but there's a second dip
@ 225 wich isn't there with the port blocked ?

Hmmmm, weird science going on there...


However, I'm planning to use the K-desing for a future system consisting
of Tractrix horns for low / mid and a tweet for higher, so I'm
specifically interested in the nod-to,say,250Hz range...

Now I see a X15 (that's smaller than a K15?)
performing WAY better (first attachement in your reply)

Do you perhaps have drawings of an X12 ?

I'd like to try a X12 instead of a K12 for my further testing...


Thanks for keepin' the Karlson vibes alive

[GM]

Originally posted by Empee
What would happen if you'd make a folded voigt, and projected
the terminus at the cone ?

Originally posted by PeteMcK
You're right, it's a folded TL.

Greets!

Sorry, assuming you're referring to the K-15, we'll have to agree to disagree. It's basic alignment is a band-pass (BP) except with two additional series acoustic low pass filters (LP, aka muffler), so in the current vernacular that makes it an 8th order BP, or as Paul Klipsch called it, a "polyresonant 4 - cavity box". The folded pipe horn (aka Voigt) shown is a BP similar in concept to DSL's current Tower of Power DTS-20 sub and Jensen's '50s era Transflex sub with the former a stunning performer and the latter fundamentally flawed.

Seems to me a smoother, wider BW 'K' would be the Voigt variant, but haven't been able to experiment with one yet.

GM