15" Jubilee Design

[infurno]

Math is not my strong point, I'm relatively a newbie to speaker design (7 built), and it's pretty late at night. With that disclosure in place, I wanted to share an idea for a 15" jubilee.

I used the plans for a La Scala as a starting point. The inner panel which mounts the 15" driver on a La Scala is 397mm x 565mm. I found the same part in a Jubilee and found it's ~22.5% smaller. Then I used this ratio to convert the rest of the measurements.

What I ended up with is a 51" x 37" x 23-1/2" woofer module. Double the height and add reflectors to fit two drivers.

Am I an idiot or does this show promise?

[garyeanderson]

If I were going to try this, I would stretch the center of the bass bin to accommodate the 15-inch woofer and leave all of the other dimensions as drawn. But I am just a rookie and when I drew out the full size top view I count up the different pieces and when I reached the end of the alphabet and it looked like AA was to be the next part I though I ought to try something else. It could have been the fact that I thought I counted 5 sheets of plywood for each bin had a little something to do with it. I started to cost out the project and the $700 for just the plywood didn't seem like the way to go when you could get Klipsch to do the completed project playing in your livingroom for about 10 times that. I am doing the La Scala clones instead.

[PrestonTom]

Before you get too far there are some important considerations. You need to know the T/S parameters of the drivers (especially the Qts, Fs, Vas also efficiency and Xmax are useful).

These will determine (mostly) the high frequency extension, the throat size and the back volume required. The existing values are for a K-31 driver, your driver will be different.

BTW, in the build done by Gil (the "caves ..." article) he used 15 inch drivers (electro voice something or other) and used the plans (as outlined in the JAES article) as a starting point and made the appropriate modifications. You mentioned the La Scala, are you thinking of using a K-33 (or 43) as the 15 inch driver(s). If so, it is not a good candidate for a Jubilee build.

Let us know what you are up to ....

-Tom

[dtel]

There is way more to it than adjusting for drivers size with the cabinet, I asked something similar a long time ago. I was thinking of going in the other direction. I wanted to build a Heritage design but using something like a 4" or 6" bass driver or even smaller and making a mini version like desktop or computer Heritage. It just does not work, there's no telling what you would end up with.

I am not saying don't do it but even with considering driver parameters it's still kind of a shot in the dark as to the performance of the overall finished product.

I only say this because that is not an easy design to build, or should I say it's alot of work especially if your not happy in the end.

[seti]

Do a search for William F Gil McDermott thread where he built a jubilee with 15 inch driver. Can't remember if he used one or two.

[dtel]

It could have been the fact that I thought I counted 5 sheets of plywood for each bin had a little something to do with it. I started to cost out the project and the $700 for just the plywood didn't seem like the way to go when you could get Klipsch to do the completed project playing in your living room for about 10 times that. I am doing the La Scala clones instead

How big do you want to go, or how big can your room accommodate ? [6]

I mean you were looking for something bigger than the Jube, that's why I ask, there is bigger...........

[infurno]

Agreed. Now that I have had coffee, I realize this was a silly idea.

I'm a bit over my head with this one. Horns are a pretty advanced topic compared to my previous projects (picture here). Not really sure how to design and simulate with hornresp yet, or what characteristics of a driver make it good for horn loading. Low QTS and a high BL but I'm sure there is more to it.

I'll stick to proven designs and search for the 15" Jubilee mentioned above.

[infurno]

If I were going to try this, I would stretch the center of the bass bin to accommodate the 15-inch woofer and leave all of the other dimensions as drawn. ...

Actually it looks like this is exactly what William F. Gil McDermott did in his Caves build. Extended the chamber by 3 inches to fit the 15" drivers. Since the Jubilee is symmetric this is a simple modification as you pointed out but I wonder how well this works in the end.

[Guest " "]

You could use stock LaScala split bass bins as the core.

[PrestonTom]

You could use stock LaScala split bass bins as the core.

Perhaps we should back up a bit and find out what the guy is trying to accomplish. IOW, what are the goals.

The La Scala is a simple build, but the low freq extension is limited (short path & undersized mouth) since it is basically a 100-125 Hz horn. Its high freq is limited because of the driver (partly) and the folding (mostly - I think).

If size is not a problem and you can can live with a 40-50 Hz low end, then a simple build would be to follow Dtel's lead and make a MWM. This is a simple build, however it is a big boy and may still require a sub depending what your goals are.

What is it you are up to? Three-way or two way? Deep bass?

[infurno]

I have been playing with the idea of Jubilee for months now. I think the
real reason I'm interested in it is because of how people praise it's
acoustical properties and it's a bit of an exotic. I'm looking for a
high performance, high fidelity, high spl, low distortion, and something
a bit more challenging to build. If the project is a success, it will be placed in a HT, just not sure what it would be doing just yet. Depends on how it sounds.



One of the reasons I never started building a Jubilee is because I could
never design a two way system I was happy with. Still can't. The low
crossover of this LF horn creates serious limitations in HF. Compression
drivers don't seem to work well to such low xo without massive horns
and compromising the higher end and thus requiring a super tweeter.
Again, leading to a 3 way. I'm not going to make this a 3 way because of
the problems associated with multiple drivers and crossover points. If I
recall correctly, Klipsch originally wanted the Jubilee built as a two
way but ended up having to compromise.

Looking at all sorts of HF options. Everything from CD, horns, full ranges... Even BG planar transducer line arrays, which may complement the RD50 planars on my mains. [^o)]

I don't have a two way design yet but I figure building the cabinet will
take a while anyway. Was down at Home Depot today and have my first set
of panels for my 15" Jubilee. I'll follow in the footsteps of others
and for now plan to stretch the center chamber.



Building one cabinet at first to see how it works, I'll be using an active DCX2496 xo and a dedicated amp.

[PrestonTom]

Good Luck on your project.

I am curious what drivers you will be using and what the efficiency, Fs, Qts & Vas numbers are.

[dtel]

This is a simple build, however it is a big boy and may still require a sub depending what your goals are.

Your exactly right, it is an easy build and they are better with a sub, I cross the sub at 40 it makes a big difference. IMO

[PrestonTom]

This is a simple build, however it is a big boy and may still require a sub depending what your goals are.

Your exactly right, it is an easy build and they are better with a sub, I cross the sub at 40 it makes a big difference. IMO

Dtel, I am curious about something.

When you first put them in the house, I am sure your reaction was: "hey, these are huge".

How many days, weeks, months did it take so that you could walk into the room and not think: "hey, these are huge"?

[dtel]

Dtel, I am curious about something.

When you first put them in the house, I am sure your reaction was: "hey, these are huge".

How many days, weeks, months did it take so that you could walk into the room and not think: "hey, these are huge"?

I will let you know when it happens. []

They still look big but since it was my daughter and wifes idea there was no second thoughts. I would guess a few weeks and they kind of blended in.

You know people come in here and ask when did you build those shelves ? Or they say that's some big horns, talking about the 402's, I tell them not as big as the ones there sitting on, most people don't think there speakers.

My Granddaughter 3 climbs in one side and out the other, the cat like sitting IN the back on one even when it's playing at a moderate levil, that suprised me.

[infurno]

I am curious what drivers you will be using and what the efficiency, Fs, Qts & Vas numbers are.

I'm curious too!

If my math is right the volume of the modified chamber in the current design is ~68 liters per driver (dual woofers 68*2) . The internal height is ~22 1/4". I don't think space will be much of a problem, there are a number of 15" drivers that would work well.

My current center channel is a Gedlee Summa clone (DE250/wg and B&C 15TBX100 15" Woofer) I may prototype the horn and run some frequency/impulse measurements with this woofer and see what happens.

http://www.parts-express.com/pe/pshowdetl.cfm?&DID=7&Partnumber=294-670

[DrWho]

Compression
drivers don't seem to work well to such low xo without massive horns
and compromising the higher end and thus requiring a super tweeter.

What compression driver / horn combinations have you tried?

Btw, you can't just scale the dimensions of a horn and expect it to behave the same...it's the area expansion rate that matters, and then the shape of that area is gonna determine your polars.

FWIW, if you wanna cover 20-20k, then you're really gonna need to go 3-way....and if you're going 3-way, then it might make more sense to xover from a midbass module to your subwoofer at around 80Hz, and then it'd be a piece of cake to xover as high as 1kHz to your tweeter...

[infurno]

Btw, you can't just scale the dimensions of a horn and expect it to behave the same...it's the area expansion rate that matters, and then the shape of that area is gonna determine your polars.

Yeah I reached this conclusion the next moring with a cup of coffee and help from everyones response.

What compression driver / horn combinations have you tried?

Some from Selenium and B&C DE250 with a few waveguides and horns. A 18sound horn was the last thing I toyed with. However, I also did my homework and the general concensus appears to strongly discourage placing a CD anywhere that low. At least, a CD that would need to reach anywhere near 20kHz. As a 3 way it may work but I'm trying to avoid that..

I saw a CD from JBL that was interseting but it's a bit pricy.. something to the tune of $500.

[Guest David H]

Some from Selenium and B&C DE250 with a few waveguides and horns.

I also did some instrument and a/b testing with waveguides and the DE250 and a few other horns. The DE-250 is a fantastic midrange however falls short on the top end. The P/E 12" waveguide didn't seem to help matters, they seemed flat sounding, even off axis. I much prefered the Tractrix in comparison, but had to give the waveguides a chance.

During these tests I also did some experimenting with the GedLee 80ppi foam, I found the foam to do a nice job softening a harsh horn without sacrificing the sound.

BTW, I your project is very interesting, hope it functions to your satisfaction.

Good Luck....Dave

[Guest " "]

Btw, you can't just scale the dimensions of a horn and expect it to behave the same...it's the area expansion rate that matters, and then the shape of that area is gonna determine your polars.

Thats right. Klipsch used a very exacting and complex process with their early heritage line. A process that can't be duplicated by the novice.

Hersey's= were sized so as to use the most wood possible from 1 sheet of plywood.

Cornwalls = were sized so as to use the most wood possible from 2 sheets of plywood

LaScala's = were sized so as to use the most wood possible from 3 sheets of plywood

etc

etc

etc

why would anyone think they can just step in and change the sizes of the cabinets and expect the speakers to work correctly.