A Speaker that Kicks Butt in Large Spaces

[xrk971]

OK, why did I just pick on the MLTL? Many folks associate a BIB with a speaker that is good for filling sound in a larger space. Well, below are sims of a Betsy K in a BIB with dimensions as prescribed by GM's BIB calculator spreadsheet (20 in wide x 28 in deep x 67 in tall, all internal dims).

The first plot shows the BIB flush against a wall with mic at 1 m away. The response actually looks very good - nice and flat with great bass extension, and boy is it loud at 1 watt!. This is just to show that on paper, the BIB can actually look good for certain cases.

Second plot: when one steps back 5 m with BIB still against a wall, the response doesn't look as good anymore - there is a big wide dip at 450 Hz.

Third plot: move the BIB to 60 inches away from a wall and listen to it at 5 meters away and you get recessed low end bass and a bass peak at 100 Hz and generally uneven response with average SPL in the mid 80 dB's.

Fourth plot: Now lets look at the Betsy K in the K15 (per Job Ullman's plan with a 21.5 square inch vent) at 5 m away and 60 in from a wall. Clearly a nice performer with nice even bass response and huge punch at 90 dB.

If you are curious what the Betsy looks like in the K15 plan with the 40 square inch vent, this is shown in the fifth plot. Still pretty good but not as tight a bass shelf as the Job Ullman variant with 21.5 sq inch vent.

So there you have it, the K15 continues to kick butt even when matched against the venerable BIB.

[GM]

Hmm, many folk's listening experiences and occasional measurements don't line up hardly at all with these or other long distance sims you've posted, so I'm inclined to ignore all of the room modes BW of those more than a meter away.........

For sure, I wouldn't use them for tweaking a design.

GM

[freddi]

"....K15 continues to kick butt even when matched against the venerable BIB"

I would hope! - LOL traditionally a K's wings visually just intercept the edge of the driver with a dead-on view. The smallest driver I've run in K15 was the Nirvana Super 10 - the reduction in cone excursion was very helpful

how difficult for you is it to scale your model to 0.8 size and run for BetsyK and FE206EN?

[freddi]

re: BetsyK - she probably likes a minimum rear chamber volume of around (qts*fs*vas)/50

when I compared an extended height K8 size coupler with 1772 to 1772 in the Karlsonette, the skinny K had 2 to 5dB less output in the 110-220Hz octave.

here's a graph of BetsyK in the skinny coupler - I think the downwards trend between 110 and 220 is partly room mode where the speaker and mic were placed - so if measured outdoors it might be rather flat versus the regular Karlson rise/"hit".

bass was "soft" in this little K - mids were good and I preferred BetsyK in this particular coupler to 1772, It will probably eventually run a Sammi with ST324 on top.

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[xrk971]

Originally Posted by GM

Hmm, many folk's listening experiences and occasional measurements don't line up hardly at all with these or other long distance sims you've posted, so I'm inclined to ignore all of the room modes BW of those more than a meter away.........

For sure, I wouldn't use them for tweaking a design.

GM

You are probably right about room modes being dominant. What I have here is a large room meaning it is "infinite" in extent beyond the floor and one wall that forms a boundary. So if you can imagine a room being a box, only two sides to the box are present, and these sides extend infinitely (no ceiling and no 3 other walls). So when a BIB is placed in a larger room with all 6 walls, there will be reinforcement from room modes for sure. I am basically talking auditorium/outdoor stage with a back and floor.

[freddi]

here's the size of the high aspect K next to a factory Karlson 12 from the 1960's
that Eminence coax has over 4mm xmax, a 109oz magnet slug, and a 4 inch voice coil

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[xrk971]

Originally Posted by freddi

"....K15 continues to kick butt even when matched against the venerable BIB"

I would hope! - LOL traditionally a K's wings visually just intercept the edge of the driver with a dead-on view. The smallest driver I've run in K15 was the Nirvana Super 10 - the reduction in cone excursion was very helpful

how difficult for you is it to scale your model to 0.8 size and run for BetsyK and FE206EN?

I have an overall scaling factor that I can tweak and I tried the 0.8 factor which is same as scaling it for a 12 in driver (12/15). The simulation is 60 in from back wall and mic at 2 m away. Second plot is for the FE206EN. It doesn't look too bad actually.

[IG81]

Originally Posted by freddi

here's the size of the high aspect K next to a factory Karlson 12 from the 1960's
that Eminence coax has over 4mm xmax, a 109oz magnet slug, and a 4 inch voice coil

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That's the TSG coax right?

I always get mixed up with the terminology, but this 8" HAK is pretty much a stretched SK8 isn't it? 13.5" wide and 12" deep? Did you prefer W8-1772 in this or SK8? I would have liked to give this TB driver a try if it weren't for the price, which is even worse here in Canada.

IG

[freddi]

yeah - that's the TSG with the yellow spider/dustcap - -in the tall SK8, I think 1772 was pretty good. That coupler may be a bit too tall or not the best front chamber shape. Lapaire seemed to like GB's scheme better than the Karlsonette/SK8 version. 1772 seemed happy in the little SK8. The coaxials can "beat" the fullrange in some ways.

hey XRK971 - K12 can work well with some 8 inch speakers as noted all the way back to 1955 by Julian Hirsch. Once you're into the 0.8 mode, can you easily reduce just the back chamber?

[freddi]

hey IG81 - - sometime make one set of the fast flare wings suggested by Carl as an upper boundary and give a listen - I liked those with 1772 in the little SK8. K12's rear chamber seemed too large for 1772.

Fast taper parameters, 131.9 square inch aperture

Gap Slope p q Area Length Wmax
0.5 2.9 1.08 9.5 131.9 18.5 12



Aperture
x w
0 0.50
1 0.78
2 1.10
3 1.43
4 1.76
5 2.11
6 2.46
7 2.81
8 3.17
9 3.54
10 3.91
11 4.30
12 4.72
13 5.18
14 5.73
15 6.43
16 7.38
17 8.72
18 10.69
18.5 12.00

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