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Cornscala Split Bass Bin Design


No.4
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This build was supposed to begin this time last year (2020). I decided to work on another project at the time and just never got around to finalizing the design and making some sawdust. Hopefully everyone is up for a build thread, and not tired of Cornscalas. These will be going in my living room and have to be designed around a foot print requirement. These will be splits so they need to match the tops that I already have completed as well. This thread will be primarily a discussion of the bass bin construction. The exterior foot print is 25.5" wide by 18" deep. all of the panels on 4 sides and top and bottom will be 1.5" thick. Probably a combination of ply and MDF. These will be heavy! I have everything to complete this build except for the veneer, which will be walnut.

 

The following is the component list.

 

Eminence kappa 15C woofers

B&C DCM 50 midrange drivers 

Eliptrac 400 horns

Dayton PHT1-6 planar tweeters

ALK ESN500 and ESN5800 networks

Miles of assorted cabling and binding posts

 

Utilizing online calculators and digging through old posts I have collected the data used to generate all of my dimensions. the consensus seems to be, that the dimensions need to be close but a little give or take should not make too measurable a difference.

 

The starting point is the overall internal dimension. 10641.5 cubic inches. This was scrounged from posts by JWC. 

Using 10641.5 as a baseline and the internal footprint dimension of 22.5" x 15" (25.5" x 18" external dimension subtracting 1.5" thickness for all of the panels 3")

 

32" H x 22.5"W x 15"D = 10800 cubic inches internal dimension. (This will allow for allow for some loss due to internal bracing)

 

Port measurements 22.5" wide by 3 3/8" tall. The port baffle board will be 9 1/2" deep.


Assuming these measurements will make music, I just need to decide where to locate the kappa on the front baffle. My instinct tells me I should try to push it a high as possible and keep it close to the midrange horn, just not sure how much. assuming my design is sound, the placement of the woofer is where I need some guidance.

 

I will add my highly technical drawings (done by hand, on paper) in the next post.

 

If anyone sees any glaring errors in my design, please call it out. 

 

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2 hours ago, Madman1 said:

Where is the tweeter going?

This is the top half setup that I will be using. I replaced these components with the heil with wings double stack above the La Scala clone bins. the bass bins will be built to match the top half. I just cant let these parts sit in the closet any more. These will end up as the mains in my living room. the 18" depth should be a little more living room friendly too. I will do some more updating to the drawing as I get time. I have the Kappa about 3 inches from the top of the cab which is much higher than the original design. Any comment on the location good or ill is welcome. I am hoping to start on the motor boards soon.

top half.jpg

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My two cents....

 

Does the mid range horn end up at ear level when you are sitting?

 

If not,  you might want to go deeper and shorter on the cabinet.

You may end up with LaScala like dimensions

 

There might be some on line design software for bass bins that includes ports, no ports etc.

 

 

 

 

 

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13 hours ago, Bubo said:

My two cents....

 

Does the mid range horn end up at ear level when you are sitting?

 

If not,  you might want to go deeper and shorter on the cabinet.

You may end up with LaScala like dimensions

 

There might be some on line design software for bass bins that includes ports, no ports etc.

 

 

 

 

 

These will be going in a living room so the height should not be an issue. They will have to compete with furniture etc. in the room. A little extra height would help. They are still not as tall as k-horns either. If I do encounter an imaging issue I can always angle the top half a little to aim them at the listener as well.

 

I will hunt around for some calculators. I would like to stay as true to the Cornwall internal dimensions as possible. But if the driver location is going to mess with the function of the port, I may have to rethink the port.

 

Or, I am just overthinking it😵💫

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1 hour ago, No.4 said:

These will be going in a living room so the height should not be an issue. They will have to compete with furniture etc. in the room. A little extra height would help. They are still not as tall as k-horns either. If I do encounter an imaging issue I can always angle the top half a little to aim them at the listener as well.

 

I will hunt around for some calculators. I would like to stay as true to the Cornwall internal dimensions as possible. But if the driver location is going to mess with the function of the port, I may have to rethink the port.

 

Or, I am just overthinking it😵💫

Check the speaker mfg web sites for design software

plus there are some packages.

They have the specs for their speakers pre-loaded if I recall correctly

 

Setting the bar low....some of the guys on here can point you in the right direction and maybe give you some feedback on your design based on their experiences and mistakes.

 

Good luck

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Would there be any benefit to going with round ports and tubes as opposed to a port shelf?

 

I always felt the shelved port didn't do the first three iterations of the Cornwall any favours. And the shelf was replaced by tractrix ports on the latest Cornwall.

 

...asking for a friend, lol

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2 hours ago, Bubo said:

Check the speaker mfg web sites for design software

 

 

1 hour ago, geoff. said:

Would there be any benefit to going with round ports and tubes as opposed to a port shelf?

 

I always felt the shelved port didn't do the first three iterations of the Cornwall any favours. And the shelf was replaced by tractrix ports on the latest Cornwall.

 

...asking for a friend, lol

Both great suggestions. Taking a quick look at the Eminence site, they recommend round ports for most of the iterations published. Now I need wade through the rest of the data and make a second potential design. I am going to design around the higher placement of the kappa as in the drawing. Port placement will be the next task. With furniture in the room near the speakers I don't know if ports at the bottom of the cabinet to couple the bass to the floor will be as effective as ports just below the driver. 

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I made almost identical pairs of Super Heresy's. One had the round 4" rear port and the other was designed to use some aluminum trim and look like HIP's utilizing a 1" slot port on the front.

I cannot tell any difference in the sound between the round vs flat port. I did do some rough calculations to make sure they could move the same amount of air and they were very similar (4" round vs 1" x 14" flat) I doubt your would notice the difference. Eminence probably uses round more often simply due to the easy implementation of a round port. The last subwoofers I got from them offered both designs (Lab 15)

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@MookieStl great info. I spent a good portion of the afternoon reading through threads all over the web about port location. The consensus seemed to be that location was not critical in a reasonably sized enclosure. There were opinions or preference but as Mookie said most could not tell the difference. This was of course internet research down while cooking and eating so take it with a grain of salt. I am very interested in the ports of the Cornwall IV though. The one point that did pop up consistently in most threads was port noise. The shape of the elements of the port was important. Looking at the CW4 ports exits you can see the 45 degree bevel. Much different than the exit of the previous versions. I would assume the port entry also has smoothed/rounded edges. I would like to explore this further. Anyone have CW4s that would be willing to measure the opening height and width, of course the depth of the the port?

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