DBKeele Plans for a Ported Horn

[mas]

...Not sure if this has been posted before, but it may be of interest to both the LaScala and Jubilee camps.

The design is for a W Box that, except for its scale, most closely resembles a ported LaScala bass bin format, but the concept easily carries over to the variants including the Jubilee.

Just thought there might be some who might find it interesting...

Keele_W_BoxPlansPDF.pdf

[Guest " "]

very close to an over sized belle with ports and 45 degree fillets at the first turn.

[freddyi]

like this?

http://img80.imageshack.us/img80/5912/keele18wboxxk1.jpg

on the subject of w-bins- whats this group's faves and what limitations will one accept for goodness in the passband? a smaller woofer can allow more path within a typical 8 cubic foot bulk but is there something fun about W-bins such as Belle and La Scala that keeps them alive?

[mas]

Thanks for the explanation Doc...FWIW, I agree! In the meantime I will attempt to refrain from being my own best enemy![]

This version is the same as the other posted. The difference is the inclusion of the application notes, response measurements, and the exploded construction drawing.

Note that Don did this circa 1977, just after moving to JBL from his stint with Klipsch in 1976.

Keele K151 2240H W Horn Plans.pdf

[DrWho]

If you edit a post without reattaching the attachment, the attachment

gets dropped. I agree, it's stupid [] I'm interested in the design

though...is the picture speakerfritz posted the same thing?

The problem with porting outside the horn is that you don't get the

same efficiency benefits. In such situations you almost have to

implement EQ and take advantage of the lack of cone-movement at the

tuning frequency.

[D-MAN]

That's an interesting point - I've got another design that is prime for a port and has enough Vb to resonate at 30Hz (with the right driver, of course), and that's well below the -3db down point below the front-horn 40Hz Fc. Since I haven't seen it done, except for the DJK modded La Scala's (and EQing was specifically mentioned), I'm a little afraid of actually chopping a hole in the thing to find out why I shouldn't have done it.

However, what about the Altec A7? That is a front-loaded horn with a reflex port, and it seems to work quite well without EQ?

DM

[DrWho]

I was under the impression that the short waveguide was for boosting the high-end response of the bassbin. Below the Fc of that horn (probably around 100Hz) it'll just be a normal direct radiator? There can't be much loading going on there either.

There have always gotta be some gains associated with the port, it's just not as big as a normal ported situation.

What speaker you planning on cutting holes in? Can you do it in such a way as to be reversible if it doesn't work out?

[D-MAN]

Yes, my backup plan is to cover up the port if I have to. I'd just like to avoid that before hand, i.e., if I knew better ahead of time, that would be one thing, but it feels like taking a blind risk.

The problem is, the design works fine without it.

It's just that the capability to port it is there and that is a powerful alure. To find out what a port can do below cutoff... tantilizing... Bob Crites has the perfect woofer for it, too. All these things make it possible.

The front-horn won't be anulled (of course) and should fall off about like a Klipschorn. The available Vb is 4.8 cu. feet., which I don't need if its front-loaded only (I can annull it in that case). I plan on making the things as convertable (or reversable, that is) as possible.

DM

[mas]

Bump...

I have updated the posts and also posted Don's plan+notes again in each. Heck, I just may post it again here![]

The file names for the 2 diagrams are different, but the contents are the same, so please don't let that become an issue!

And one other observation...these plans are from right after Don published his LF Horn design Using Thiele-Small Parameters AES paper. It might be useful to give him a call and see if there is any direct relationship, as Don has a propensity for generating several proof of concept designs whenever he brainstorms like that! I assume most have that fundamentally significant paper, but I will also post it again as well for anyone who might have missed it in the past.

Keele K151 2240H W Horn Plans.pdf

[mas]

DBKeele - LF Horn design Using Thiele-Small Parameters AES paper

LF_Horn_Design_Using_TS - Keele.pdf

[freddyi]

just peeking, the sealed rear chamber design example's spec for output doesn't look horribly far off from a 2-12" Sentry IV with low Qts drivers. guess example is for 1-12" (?)

I recollect that 20CF W-box - wonder how much weaker an 18" Karlson box 8-10CF would be in the 50-200Hz area? one might have to start with an 18" with 5% or greater No rating. above 200Hz the Karlson would have no gain and Fb probalby would be more like 41-50.

lookling at Keele's ported w-bin expansion with calculator, its looks like m=0.7, St = 169sq.in. and Sm of aobut 820sq.in. reached around 4ft path for a 40Hz flare rate. it take 7ft path to get 40Hz 1/4 wave. What would change today in design practice?

[mas]

Please pardon me if I am simply being a bit obtuse this morning before a cup of coffee, but what does a Karlson have to do with the Keele lit and ported W box configurations? This is not a thread about basic comparative LF horn topologies. Have I missed something?

[freddyi]

my apologies to interject the Karlson box so removed the graph- low end on the Karlson-stype was similar in shape to Keele's W-box plot. Would the 20CF Keele box sound "good" overall for bulk involved and did I miss something - Is this for home use?

FWIW 30" depth will make a 100Hz straight horn about bulk of La Scala's bass section to be used with 35-40Hz horn or pipehorn sub but that's not the Klipsch approach either. What midrange and HF would one employ with the Keele box?

how might one apply rear chamber volume and tuning vs nominal flare in these ported hybrids?

Bob's cast-frame woofer looks good for EQ-ed ported horn

I know Karlson are hated - sometimes with good reason.

Freddy

[djk]

"what does a Karlson have to do with the Keele lit and ported W box configurations?"

Fred's POV is the Karlson, I have no problem with that. It is always useful to know where people are coming from.

"just peeking, the sealed rear chamber design example's spec for output doesn't look horribly far off from a 2-12" Sentry IV with low Qts drivers.guess example is for 1-12" (?) "

The design in the Keele paper

http://forums.klipsch.com/forums/storage/6/776355/LF_Horn_Design_Using_TS%20-%20Keele.pdf

Is the TL5050, the Sentry IV. The back volume calc is for one driver.

The box you linked to

http://img80.imageshack.us/img80/5912/keele18wboxxk1.jpg

is for a K151, an 18" low Qts driver.

I've heard these before, they have a lot more bass for even just one cabinet than even a stacked pair of (stock) LaScala. The rear chamber is about 5 cu ft, and tuned to about 35hz. My vented LaScala mod is about the same size and tuning. The Vas on the JBL K151 is only about 20% higher than the Klipsch K43E, and the JBL design would also benefit from a Q=2 high pass filter to boost the low end below 50hz and protect from LF signals below the port tuning frequency. The Klipsch K43E is capable of higher volume displacemet than the K151, and so will actually have more maximum output.

The JBL box sounded much better than the non-vented C-V B48 of similar size, basically a 64hz W-bin.

[freddyi]

is there a possiblity of an in-between Keele and LS size ported w-bin for Bob's new high Vas cast frame 15" woofer or could 18" Keele's ramp and throat be better adjjusted for that 15" - maybe just with an adaptor plate? did the Keele 18' boxes go up as smooth soundwise as La Scala? 20CF seems awfully large for a 15" horn.

re:LB76 mentioned at the beginning of the thread - have you simmed it? might a vented LB variant work well?