Very weird LaScala question (designing bass bin)

[Coytee]

Or a split half height jubilee with only one twelve.

Hmm... a Runtlee? [*-)]

[russ69]

Does the nose-cone of the LaScala have to be pointed or is that for cosmetic/build reasons?

I don't want to bust your bubble or a possible future project but there is nothing in a loudspeaker design that isn't there for a reason. If you wish to become a loudspeaker designer it's an expensive path of testing and re-design. The finished products that have made it to market have a ton of hours of engineering and research built into them. Show me a good speaker designer and I'll show you a huge scrap pile! You can bet he's not listening to the first pair of speakers he made either!

[Daddy Dee]

Or a split half height jubilee with only one twelve.

Hmm... a Runtlee?

Now that would be fun... a Jubilee version of the LB. That would have some historic connections and could be a super center. Plenty of options for mounting the 510, too.

[Coytee]

I don't want to bust your bubble

heh...you flatter me. I can assure you that I don't have much of a bubble to burst in this arena! I'm just tossing spagetti to the walls to see if any of these ideas stick as something interesting. The odds of ME then being able (or even willing) to try to achieve it are rather small and I'm well aware of that reality.

[Y]

[DrWho]

Question: Is it the point of the nose or simply the area behind the woofer? What if instead, the 'cone' was oval? rectangular? BUT... had the same area. I thought the area was the key, not the shape?

What do you mean by area around the woofer?

What matters in the sealed chamber behind the woofer is the volume of trapped air. What matters as the sound wraps around the back towards the front is the area expansion rate.

However, you can't change the angle of the walls without affecting the polar response...and you can't just change one wall without affecting the area expansion.

Btw, changing the polar response is also going to change the frequency response because now the same amount of energy is being sprayed over a different area. If the polars get wider, then you measure less SPL on-axis and more SPL off-axis. If the polars get narrower, then you measure more SPL on-axis and less SPL off-axis.

[DrWho]

Or a split half height jubilee with only one twelve.

Hmm... a Runtlee?

Now that would be fun... a Jubilee version of the LB. That would have some historic connections and could be a super center. Plenty of options for mounting the 510, too.

I personally would go with a faster flare rate if going with a half height Jubilee since the mouth area is going to be half. Raising the Fc of the horn to ~80Hz instead of ~40Hz is going to be fine for a center channel.

[Invidiosulus]

I'd speculate the 510 would need to be horizontal for dispersion?

Maybe...

Not if you turn your belle/scala cab on it's side.

[DrWho]

JPB?

[Marvel]

You could build Erik Forker's scaled down LS bass cab with a 10" woofer. 100-500Hz. It's about 16 inches wide. Would the 510 fit on top of that? Ought to make an excellent center and it wouldn't be very tall.

[Marvel]

JPB?

Oh, Mike, you missed this?

http://forums.klipsch.com/forums/t/128394.aspx?PageIndex=1

[jwc]

Josh. You are really crackin me up with the JPB thingy.

Say....if your into drawin up stuff....humor us with this for you new audio company...I do everything by hand so I'm super slow.

Turn that bass bin right side up. Instead of that middle section coming to a point.....have it be exactly as wide as the baffle (in the back)...the one with the ramps. Can't remember the width of that panel....~16-17".

any way...say it is 16 for ease of explanation. So now the middle section no londer is "flared" but pointing straight out the front of the speaker and there is a flush panel to put a K510 on.

Now the side panels of the bass bin need to "flare out" 8 inches on each side. There are two ways to do that on the scala bin....but just leave it at that for now.

So now the area of expansion is about the same and the mouth/exit is about the same.

Yea...I know...the polars will be different...but hey...that can't be too hard to build...

whos up???

jc

OH...I forgot...you can also throw two 4" ports coming out the front under the 510 as you have added some sealed chamber volume to play with.......whew hooo!!!!

[Coytee]

Not if you turn your belle/scala cab on it's side.

Wow... I guess I must have seen something like that somewhere in the past... that is the exact concept of which I'm talking about. I imagined it to look a little different but that's it.

Turning on it's side... PFFFT! who would have ever thought of that one! lol..... show's you how stubborn I can be in my thinking to only see it as vertical.

[Y]

[DrWho]

JPB?

Oh, Mike, you missed this?

http://forums.klipsch.com/forums/t/128394.aspx?PageIndex=1

lol, that's awesome.

[DrWho]

Turning on it's side... PFFFT! who would have ever thought of that one! lol..... show's you how stubborn I can be in my thinking to only see it as vertical.

I believe the original lascala was on its side...or is that the current lascala is now on its side? Either way, I know I've seen a very early picture of the lascala where the sharp edge was horizontal instead of vertical like it is today.

[Coytee]

JPB?

Oh, Mike, you missed this?

http://forums.klipsch.com/forums/t/128394.aspx?PageIndex=1

Wow...I was really unplugged from this humor! I read it as JBL then when Who typed JPB I thought he referred to someone's comment (somewhere) about the speakers that someone (DJK?) designed, the D2 or something like that....

I bit on Josh's design/picture hook line & sinker as it being a copy of some brochure...

[]

[PrestonTom]

Or a split half height jubilee with only one twelve.

Hmm... a Runtlee?

Now that would be fun... a Jubilee version of the LB. That would have some historic connections and could be a super center. Plenty of options for mounting the 510, too.

I personally would go with a faster flare rate if going with a half height Jubilee since the mouth area is going to be half. Raising the Fc of the horn to ~80Hz instead of ~40Hz is going to be fine for a center channel.

Mike, your comment about the mouth size on a "half jubilee" is incorrect (although a number of folks have made that same statement).

Look at the JAES article where the Jubilee bass bin and its design are presented. The flare, throat and mouth calculations are based on a single driver (or half the height of the final cabinet).

Yes, the mouth (or horn length) is small (or foreshortened). By effectively having two horns stacked on top of one another, there is mutual coupling between the two horns (the two half height "cabinets") and this will decrease the peaks and troughs of the frequency response at the low frequencies (due to a mouth that is "too small"). It is further decreased by placing the cabinet in a corner, so there is a boundary condition (1/8 space loading).

Of course, a "half height" Jubilee used as a center channel will end up being 1/4 space loaded and not 1/8 space loaded and will also not benefit from the mutual coupling of a "pair" of horns. So it will not have the same low end response, but the Fc from the design is not changed. If I get a chance (and if my back is up to the task) I will try and make some quasi 1/8 space measures of a single, a double and a triple stack of "half height" cabinets (if my amp can drive a 2 ohm load).

Good luck,

-Tom

[billybobg]

Question: Is it the point of the nose or simply the area behind the woofer? What if instead, the 'cone' was oval? rectangular? BUT... had the same area. I thought the area was the key, not the shape?

What do you mean by area around the woofer?

What matters in the sealed chamber behind the woofer is the volume of trapped air. What matters as the sound wraps around the back towards the front is the area expansion rate.

However, you can't change the angle of the walls without affecting the polar response...and you can't just change one wall without affecting the area expansion.

Btw, changing the polar response is also going to change the frequency response because now the same amount of energy is being sprayed over a different area. If the polars get wider, then you measure less SPL on-axis and more SPL off-axis. If the polars get narrower, then you measure more SPL on-axis and less SPL off-axis.

Mike,

Not wanting to speak for Coytee, I believe he was
talking 'volume' not area, I very much appreciated your response as I delved into this area by shortening and widening a bass bin in order to fit under a yet to be built home screen. I did consider volume, but didn't expect that the angle of the v-shape would have a huge effect on the sound. While I thought about possible impacts, I had no idea on how to compensate, so I am proceeding with the build. Maybe this comes under the heading of soon to be 'Heading to the Woodpile". As it's going to be a center channel, perhaps it will not be a 'noticable' issue. Your thoughts would be appreciated.

Thanks,

bob

[seti]

Turning on it's side... PFFFT! who would have ever thought of that one! lol..... show's you how stubborn I can be in my thinking to only see it as vertical.

I believe the original lascala was on its side...or is that the current lascala is now on its side? Either way, I know I've seen a very early picture of the lascala where the sharp edge was horizontal instead of vertical like it is today.

Like this one. It is at the New Mexico Klipsch Museum. Notice it also has braces.

[Coytee]

Not wanting to speak for Coytee, I believe he was talking 'volume' not area, I very much appreciated your response as I delved into this area by shortening and widening a bass bin in order to fit under a yet to be built home screen. I did consider volume, but didn't expect that the angle of the v-shape would have a huge effect on the sound

Bob, you spoke accurately! I wish I'd thought of this before...but to draw an analogy... the Belle has a 'truncated nose' (or cone as I called it) so Who... are you suggesting that the chopping off of the nose of the bass bin to make the Belle is a major change?

Bob is correct in that I was asking about the volume of air for the backchamber. I personally don't see why the LaScala would know nor care if the back chamber was pointed as it is, or square or oval, as long as the volume was correct.

I'll admit there is a lot that I don't know so we have no surprise here.

Put a bit differently, if the doghouse of the LaScala were an air filled balloon and the driver/horn of a K510 were to be pushed into said balloon then what would happen (presuming it didn't pop)

The balloon would want to stretch to the sides while the indention of the 510 entered it. This would essentially, displace that volume off to the sides or something like that. If the balloon stretched enough, you could still have the same air volume in the balloon however, it would have a different shape since it was now formed around this inserted horn.

This is what I was trying to get to about putting a square box behind the woofer. The volume of the K510/69 would need to be known so that a commensurate amount of volume could be recreated by making this box a little bigger.

This is why I was asking if the "point" of the doghouse was any important factor or merely came about for construction purposes. The mere fact that the Belle has a truncated "point" suggests to me this was more for building purposes than the need to have a wedge shaped area behind the woofer.

Am I remotely close?

[Invidiosulus]

Josh. You are really crackin me up with the JPB thingy.

Say....if your into drawin up stuff....humor us with this for you new audio company...I do everything by hand so I'm super slow.

Turn that bass bin right side up. Instead of that middle section coming to a point.....have it be exactly as wide as the baffle (in the back)...the one with the ramps. Can't remember the width of that panel....~16-17".

any way...say it is 16 for ease of explanation. So now the middle section no londer is "flared" but pointing straight out the front of the speaker and there is a flush panel to put a K510 on.

Now the side panels of the bass bin need to "flare out" 8 inches on each side. There are two ways to do that on the scala bin....but just leave it at that for now.

So now the area of expansion is about the same and the mouth/exit is about the same.

Yea...I know...the polars will be different...but hey...that can't be too hard to build...

whos up???

jc

OH...I forgot...you can also throw two 4" ports coming out the front under the 510 as you have added some sealed chamber volume to play with.......whew hooo!!!!

You mean a miniature MWM ?