remember the Sadhara? - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

Old 01-30-09, 04:01 PM Thread Starter
Senior Shackster
Ben

Join Date: May 2006
Posts: 343

Quote:
Are you sure the calculations are right? A round port 2.3 inches in diameter has a port area of 5.5 inches.
My calcs are prolly right... it's my terminology that's off. I meant 5.5" of equivalent diameter, not area.
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Old 01-30-09, 04:14 PM
Elite Shackster

Mike

Join Date: Apr 2007
Posts: 19,397

Gotcha.
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Old 01-30-09, 10:53 PM Thread Starter
Senior Shackster
Ben

Join Date: May 2006
Posts: 343

I guess I can't call mine the Sadhara - but I named it that on my desktop.

at 48" of outer tube, and 26" of inner tube, I get 0.2062 ft^3 of equivalent vent area according to Sketchup's area calculator - which translates into 29.69 inches^2 of vent area, or the approx equivalent of a 6" diameter port.

the 48" outer tube and 26" inner tube also give a combined volume of 3.38 ft^3.
3.38 ft^3 interacts with 26" of 6" diameter port to achieve a tuning freq. of 26 hz.

My port dimensions can't change, so to achieve lower tuning I need to lengthen my 14" diameter tube.

extending the 14" tube to 56" long brings my tuning down to 25 Hz.

Last edited by Bent; 01-30-09 at 10:58 PM.
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Old 01-30-09, 11:58 PM
Senior Shackster

Collo

Join Date: Dec 2006
Location: Newcastle, Australia
Posts: 284

Quote:
Bent wrote: View Post
Creating any transition within is going to be difficult,
Do you think that chuffing might be an issue even if equivalent port area is as high as ....
The CSA should be fine, but its the terminations that might cause noise.

Some MDF plugs can make flares for you...

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Old 02-03-09, 11:19 AM Thread Starter
Senior Shackster
Ben

Join Date: May 2006
Posts: 343

I ran this through Unibox,
Drive Unit Parameters
CSS SDX-10
Fs 26.00 Hz
Re 3.50 Ohm
Qms 4.00
Qes 0.42
Sd 330.0 cm2
Vas 53.0 l
Xmax peak 18.40 mm
(Le) 1.42 mH
(Le2) 0.00 mH
(Re2) 0.00 Ohm
Nominal Power 300.0 W

I re-measured my tubes, and get an equivalent area of a 5" diameter port.
The port would be 26" long - as dictated by the length of the smaller tube.

inside tube is 26" long, outside tube is 48" long,
total sum of volumes of each tube = 3.38 ft^3

it shows, when using a Creative Sound 300 watt Bash amp.

(Note, I'm just moderately under ported here).

This has grown to be larger than a computer monitor subwoofer though.
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Last edited by Bent; 02-03-09 at 11:25 AM.
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Old 02-04-09, 11:43 AM
Elite Shackster

OJ

Join Date: Oct 2006
Location: Toronto, Ontario
Posts: 1,966
My System

Heh, I was going to ask if this had gotten bigger than you thought it would. It looks like a very cool project though. Are you intent on using the concentric design? If you're OK with the bigger size, it would make a very nice sub. As you saw in my thread, my SDX10 is going into about 1.5 cubes in a ported box, and the response rolls off a lot earlier than yours does in the big tube. I think my F3 is about 28Hz.

Now my only question is... how are you going to mount that BASH amp if most of your tube is port??

- OJ -
DIY Ported Original Tempest Sub (offline)
DIY SDX10 Sub
DIY Dipolar rear surround
DIY XLR to RCA cables (offline)
DIY 1 to 4 RCA splitter
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Old 02-04-09, 12:23 PM Thread Starter
Senior Shackster
Ben

Join Date: May 2006
Posts: 343

Well, I don't actually have the SDX-10, nor the BASH amp yet. All I do have are the tubes and Unibox.
(and the tools).

I'd stick with the concentric design because it is unusual - but not original. I really like the idea of not having a port open to the top, in fact, I think there might be some acoustical gain in keeping it low to the floor.

The amp, I'd think, would mount in a cut-out a few inches above the top of the inside tube, it would take ome tests, but I have lots of 14" to practice with in trying to integrate a flat amp into a rounded surface (I'd need to fabricate a mount of some type).

I found the concept of designing the enclosure to match the port dimensions kinda backwards - but unique itself.
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