La Scala up scale ?

[Valde]

Hello,

I have a question regarding the La Scala model. For the moment I'm using a JBL2350 mid horn (80cm wide) for my AscentV2 corner speaker (Dana Moore's). The La Scala model is around 60cm wide.

Do the forum think that it will give a reasonable result if I do some scaling so the wide of my future La Scala cope with the 80cm wide mid horn. So to say I will "stretch" the numbers on the drawing, keeping the angle in the horn throat and just prolong the lines in hight and wide. The dept will I keep.

Any thought about the fn of this "tweaking"?

Regards

Valde

[Islander]

Audio scaling is not like cooking scaling, like "twice as many people eating calls for twice as many potatoes". Since the sound waves don't scale up, the calculations used to design the original-size speaker will no longer be correct.

A forum member built a scaled-down La Scala a while back and it took quite a bit of tweaking to make it sound good. It used a smaller woofer and all the measurements were 80% of the regular size. He succeeded in the end, but it was much more complicated than he had anticipated.

There was quite a bit of discussion and interest in his project, but I wasn't able to track down the thread when I searched for it a few minutes ago. Perhaps someone else can find the link.

The completed speakers were quite good-looking and got a lot of favourable comments.

[WMcD]

I believe that such an alternate design will do just fine.

Consider that an LS has three flare sections. 1) At the back where the area basically doubles in 12 inches. 2) The short section where there is no change of area, probably about 6 inches or less. 3) The last flare to the mouth where the two paths combine at the mouth at a point.

As I've pointed out, overall, you've got doubling of area every 12 inches of length, and that is an exponential.

But let's look at the Belle. It really only has two flare sections. 1) At the back. but here the flare is a bit slower than the LS. 2) Well, there is no 2) because the Belle doesn't have that region of no change. 3) The flare to the front, maybe a bit faster than the back section. Granted, the mouth has that flat surface and the paths don't actually join.

Still, IMHO, these are both approximations of an exponential flare. Small departures don't hurt.

The issues which really hurt short horns in bass are just that A) they're short; related to that is the fact that the mouth (big end) is not very big. Mods which increase either are good.

Gil

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[Valde]

Yes, that also what I belive would be the case. If I do the resizing it will still obey the exponential development and the benefit will be, that the horn will be some 15 to 20 cm longer (haven't done any cal. yet) and more interesting the mouth will be considerable biggere. As I understod the horn stuff the start and end area is of great importance (of course also the exp. dev. in the horn). I like the look the LS has and also the possibility to build in my midrange (WAF)

I have done the Ascent V2 which is a design Dana Moore did for some 3 years ago (I have posted my construction of it in the diy area). A modified K-horn. Here the midrange is on top (low WAF).This horn, due to corner placement, hase a very powerfull lowend <45 Hz. For the LS what is the low end here?

Reg.

Valde

[greg928gts]

Why don't you build Dana Moore's Jamboree bass bins?

We have a diy section? [:^)]

Greg

[JohnA]

It will work, but you should maintain the throat size, slot size and back chamber volume, if you use the K-33 woofer. I think that will end up looking like a Belle.

[PrestonTom]

I agree with the above posts about maintaining the flare rate and throat size.

I have not drawn out the exponential and how the La Scala approximates it. However if I recall correctly the mouth is undersized (and perhaps the horn length is foreshortened). So I would target those features when you increase the width of the cabinet. This could actually improve the performance by getting rid of some of the ripple that occurs with an undersized mouth and horn length. In this case however it may be too small of a difference to have any large effect - I don't know.

Definitely, draw out the desired exponential first and the current approximations. This will make it easier to visualize. Also if the initial flare has been increased (relative to the exponential) then you have a "rubber throat" design. If so, you may not want to alter the initial section (immediately after the throat). I do not recall if the La Scala incorporated a rubber throat or not. The ideal back volume can be calculated (see the JAES article: Delgado and Klipsch, 2000). Increasing the back volume can help the cabinet at the lowest frequencies to an extent (don't expect a miracle however). So that could be another target for the "extra" space.

Please note that if you substitute a different woofer, then there a number of other design considerations

Please let us know how it works out.

Good Luck,

-Tom

[Marvel]

I've wanted to start a section called "Dennis sez", but it probably wouldn't be right. [:#]

However, he did say, "The taper rate of a LaScala is 100hz,The mouth area is good for 125hz. Below this it is a big woofer in a small sealed box."

My take, would be to maintain the initial flare rate and leave the back width of the cabinet the same. Make the front wider, to accomodate the larger mid horn you have described. You have two benefits: One, you can install the wider mid horn in the same cabinet, and Two, you increase the horn mouth size, even if only by a small amount.

Bruce

[djk]

Light grey is K33, dark is K43.

[Valde]

Hi,

The woofer I will use is the same as I'm using now in my corner speaker, the JBL K-145. It has a very light diapragme and is able to go >400 Hz. The reason for trying other cabinets is also to flatten the response from 100 to 500 Hz as good as possible. I guess my woodwork is to claim for my current response [:$]

Anyway what is the drawback if the flare rate is not maintained? My opinion is that the throat vs. mouth size is settled and then the "road" to the mouth is done as a exp. development so this is it or....?

Anyway I will keep you updated in the building progress which should start within 30 days.....

Regards

Valde

[Don Richard]

Still, IMHO, these are both approximations of an exponential flare. Small departures don't hurt.

PWK used what he called a "rubber throat", a section of horn segment with a rapid initial flare followed by a slower flare rate. The Khorn has 2 such "anomalies",IIRC, from a perfect exponential flare. If you want to augment bass in a LS the best thing to do is to put it against a wall or in a corner.

[Don Richard]

PWK used what he called a "rubber throat", a section of horn segment with a rapid initial flare followed by a slower flare rate. The Khorn has 2 such "anomalies", IIRC, from a perfect exponential flare. If you want to augment bass in a LS the best thing to do is to put it against a wall or in a corner.

The Khorn, LaScala, and Jubilee all use different flare rates throughout. The LS is an interesting standout in that it uses a 60 Hz flare throat section and a 125 Hz terminal (mouth) section for an overall Fc of approx. 70 Hz. Not the usual configuration, and was likely done to allow the use of the same driver, throat opening, and crossover/slope as the Khorn, an economic decision, I presume.