Karlson front chamber - what is best shape?

[freddi]

for different purposes and how might one determine beforehand which shape, asoectm baffle angle and reflector will make best use of volume, play the smoothest, etc? (with vented case, is the 3rd impedance peak an indicator?)

how should the front and rear chambers be sized? how might height matter with a vertical confituration?

[PeteMcK]

Hi Freddy,

My gut feeling is that for max resonance in the front tube, height needs to be a quarter wavelength fo the lowest freq, The cross section needs to be around Sd, lower & you loose efficiency, higher & the tube resonance would become hard to control.

However, if dispersion pattern is the design aim, then shorter/wider may be better for the desired result.

Rear chamber, I see as simply a BR box, tuning needs to match driver Fs & front tube wavelength for max efficiency.
(Although EBS alignment would be interesting).

Of course, BR is not necessary, extended response is acheivable by using rear radiation as in a TL, but here tube length becomes more important.

Pete McK

[freddi]

Hi Pete -

seems like K15's front pipe cross-section above the baffle would be "~Sd" (maybe somewhat larger) and X15 if just a perpendicular board were aove the baffle would be ~0.75 Sd - in practiwse, X15 and Zintz's KHYBOE wer built somewhat smaller and with forwards cant reflector. (115BK hasd ~0.9 cubic foot front chamber vs 2.2 for K15)

going larger might be counterproductive.

K15's 3rd Z peak is 155Hz (an 8 cubic foot coupler without the shelf had 195Hz 3rd Z peak) and RCA-Fan's X15 came in aorund 195 with a perpendiular panel and horizontal slot vent at top.

if a vented Karlson were made very tall - could it de-tune like a bandpass or would it play correctly? When I added a 20L fold-over stub to front chamber of one test-coupler, the low end impoved by 2dB and lost similar in upper bass. Adding 45 l pushed the 3rd Z peak to below 100Hz losing upper bass output. That may have been a side-branch muffler.

if one is built like Karlson's originals - could narrowing the pipe and going taller have any good effect?

the rear chamber should have practical constraints vs other type - or it could be built ~t-line.

going by Karlson's first "Acoustic Transducers" patent, supppose more baffle tilt (and there might be an optimal aperture and angle for a particular driver)

(1)lowers cutoff (might not be much effect there?)
(2)increases reverb
(3)worsens transient response

it would be interesting to see how far down a front chamber might be takened and still retain the "hit" and same ~ LF as K15. A 32"x16"x21" coupler wiht 23 degree baffle ran shy of K15 and an 8 cubic foot coupler.

Best,
Freddy