AKABAK 3

[kaameelis]

What elements T-S parameters you want in 0.44 scaled Kalson?

 

[freddi]

0.44 size for a 6.5" driver

Def_Driver ‘6PEV13’ | B&C 6 inch midrange driver 2.5mm xmax
Sd=132cm2
fs=126Hz
Mms=6.0g
Qms=4.6
Qes=0.39
Re=5.2ohm
Le=0.60mH
Vas=6.0L


and if possible on the horizontal polars, two general mic perspectives

 

[kaameelis]

I made correction to file, only Sd is little bigger to fit to existing hole for element. Rms is missing in element data, used is value 1.0 Ns/m. Infinity baffle is removed, so result is like free field.

 

[freddi]

Thank you very much.

That looks plausible - and suggests front chamber aspect and depth might be changed in hopes to lessen the first dip - such as making the front cavity less deep.

The cabinet with the deepest dip in this picture was about K15's size and with a 3 panel reflector. The middle cabinet is an old K15 with 40 sq.in. port and its 18 inch speaker mounted over the 13.3 inch cutout. The smaller cabinet to the right has a more shallow front cavity and smoother response.

I'm not sure if having the microphone on the ground is a good way to check smoothness - what do you say ?

This is case where Akabak3 could solve things which normally take empirical work. Such as see if a particular cavity, port placement, and other factors produces better results than others.

 

[freddi]

maybe pelanj or other handy person could make a 3d model from the Acoustic Control 115BK, which when scaled 1.2X would be K15's bulk and accommodate 15 or 18 inch speakers.

I don't know if there's any inherent advantage to its baffle layout - but it does play smooth

 

[freddi]

also, one Karlson builder's scheme with a curved reflector and vent at the top of the reflector. This plan is a 6.5 inch driver version scaled down from an 8 inch cabinet plan

It would be interesting to see what Akabak 3 would do with that cabinet.

I have an 18 inch driver Karlson type which is a very good performer - was just a guess.

The picture at the far right is the 6.5 inch driver cabinet

 

[freddi]

another case where Akabak 3 should be very useful would be to examine horizontal on and off axis response of member Oldfi's "XKi" cabinet as its tapered aperture is quite narrow.

The vent is shown in the top view and 1.5 inches high and flared at both ends.

 

[freddi]

-- thanks to TB46 for an Autocad 2d drawing, and Pelanj for translating that drawing into a 3D file, I now have the 3D file for Acoustic Control's 115BK Karlson-type cabinet.


It would be interesting if kaameelis would examine how it does in Akabak3 at regular size, scaled ~1.2X to K15 size (would accommodate 18" speaker) and perhaps see if it could downscale somewhat.

I'm not sure how to upload that file so PM for my email if interested

Here's are some possible drivers - - (EVM15L is what is in my 115BK but could not find Mms and don't have hornresp to calculate it)

Def_Driver ‘Kappa 12A’ | Eminence 12” speaker 3.2mm xmax
Sd=519,5
Fs=46Hz
Mms=42g
Qms=7.76
Qes=0.28
Re=5.41ohm
Le=0.77mH
Vas=112.1L



Def_Driver ‘Signa Pro 18A - 2’ | Eminence 18 inch woofer, 6.1mm xmax
Sd=1140cm2
Fs=28Hz
Mms=130g
Qms=8.28
Qes=0.30
Re=6.29ohm
Le=1.90mH
Vas=441.2L

Def_Driver ‘Delta Pro15A’ | Eminence 15 inch speaker, 3.2mm xmax
Sd=856cm2
Fs=42Hz
Mms=61g
Qms=4.73
Qes=0.44
Re=5.71ohm
Le=0.83mH
Vas=243.5L

 

[freddi]

and more transparent

 

[kaameelis]

I'm not sure how to upload that file so PM for my email if interested

Compress cad file to zip file, zip files can be uploaded same way as images.

 

[freddi]

lets see

 

[freddi]

besides response on and off axis, would input impedance be available to see where Akabak determines tuning ?

Here's how it tuned with EVM15L

 

[freddi]

For reference, here's what I have for measurements of the Acoustic Control 115BK cabinet, loaded with Electrovoice EVM15L.

The mic laid on the ground 2M away from the cabinet. Two sweeps were made - one with cabinet upright, one with cabinet tilted forwards as to put the speaker baffle perpendicular to the ground,.

There was no damping material whatsoever in the cabinet.


I have a question which hope Akabak3 can solve. Is there an excursion dip where the front chamber resonates? Perhaps that would show different for the 1.2X version with 18 inch driver than with 1X and 15 inch driver. That does not show with hornresp.

 

[freddi]

@kaameelis - - I can't open that Karlson11bk file anymore in my viewer,

Did it work for you?

 

[freddi]

I'll try again just in case - maybe my free viewer only allowed a few openings ?

 

[kaameelis]

First version I downloaded was OK.
But I had no time to put it on Akabak.

 

[freddi]

"eventually" would be fine 😀. perhaps 5 companies built nearly the same cabinet at the same time - multiple licensing and there's a story that JBL had purchased the rights w/o Karlson's wife's knowledge and shut them down.

The late Ernst Beck was one builder. His version was like KK-Audio's version and probably like Transylvania Power Company's cabinet with an extra reflector panel. Beck choked the vent's area as seen in the picture below. I doubt if it shifted fb much. (my 115BK ~53Hz)

I do think the smaller vent may have some subjective effect upon "tone"

This BEC cabinet belongs to Franz Stolz

 

[kaameelis]

I made simulation, based on previous K15 and Kappa Pro 15A simulation.Not very good.

 

[freddi]

@kaameelis.

Thank you very much. I think the correlation between your Akabak3 simulation and my graph is very good other than the depth of the nulls.

What factors in the real cabinet vs the simulation might make the nulls appear different in depth ?

 

[freddi]

If both the 1951 Karlson "K15" and Acoustic Control's 115BK were new - "not yet built" designs and 115BK were scaled to K15's bulk, plus each used the same driver, one would probably say K15 is the better of the two proposed designs based on Akabak3's interpretation.

The Karlson enclosure has been pretty tough to simulate. Matthew Morgan J came up with an approximation of 115BK for hornresp.