New Tempest-X2 15" Slot Ported Design (Sketchup Attached) - Feedback Appreciated - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 25 Old 03-14-10, 09:35 AM Thread Starter
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Re: New Tempest-X2 15" Slot Ported Design (Sketchup Attached) - Feedback Appreciated

Quote:
gperkins_1973 wrote: View Post
I agree with Kevin that the 1.5" will be fine but I don't think you will be doing the driver justice with only 500 watts.
Graham/Kevin,

Thanks for the feedback. I'm starting to agree that if I'm going to do this project, I might as well maximize my investment and go with the 1000W amp. I would feel better with the 2" port height @ 1000W. I'll create an external amp Sketchup drawing with the 2" longer port for any that are interested in it and attach it to the first post of this thread.

Steve
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post #12 of 25 Old 03-14-10, 10:31 AM
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Re: New Tempest-X2 15" Slot Ported Design (Sketchup Attached) - Feedback Appreciated

Go on Steve you know you wanna! LOL! Let the party start.

cheers

Graham
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post #13 of 25 Old 03-14-10, 08:40 PM
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Re: New Tempest-X2 15" Slot Ported Design (Sketchup Attached) - Feedback Appreciated

That will be great. I am interested in building one with the Dayton SA1000 amp. Thanks.
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post #14 of 25 Old 03-14-10, 09:57 PM Thread Starter
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Re: New Tempest-X2 15" Slot Ported Design (Sketchup Attached) - Feedback Appreciated

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mardelgo wrote: View Post
That will be great. I am interested in building one with the Dayton SA1000 amp. Thanks.
Ok ... updated first post of this thread to include larger slot port enclosure better suited to 1000W standalone amp (like the SA1000).

Enjoy.
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post #15 of 25 Old 04-02-10, 06:24 PM
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Re: New Tempest-X2 15" Slot Ported Design - Feedback Appreciated

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lsiberian wrote: View Post
1.5" is way to thin for a slot port. 2.5" at least is suggested. Flaring is only useful for looks.
Flaring is about more than just looks. A number of years ago I was experimenting with different flares, from no flare up to 72mm radius on a 100mm vent. I was using a 12" driver in a 70L box with 46mm excursion at 20 Hz. No flare lead to massive turbulence and air was coming out the vent like a fan. You could feel it blowing from some distance. 18mm radius made a big improvement, 36mm a similar improvement, and 72mm also noticeable. With the latter, the air didn't seem to "blow" at a distance but made a more gradual transition. In all cases, chuffing was still audible, but went from a noisy obnoxious sound to a quiet noise that could be masked by other content.

I had a discussion with Collo on another forum, but didn't anticipate what he'd do with the ideas we talked about. He did a whole lot of experiments, then created a great little application for predicting if a port will chuff or not. The info is here:

http://www.subwoofer-builder.com/flare-testing.htm

Anyone building a vented sub should read this and download his application flareit.exe

Of course, slot ports are different as the aspect ratio is very different. Perhaps a small radius has more effect, but it's certainly not true to say that flares don't do anything. What you want to do with the flare is size it so that the aerodynamics are not a bottleneck at the ends. Each vent has a certain "core limit" where velocity is too high and the frictional resistance causes excessive turbulance and chuffing. Ideally you make the port flare big enough so that it can handle velocities up to that point.

What most do is accept a compromise, as this approach leads to big flares and a design that often isn't practical or is difficult to realise. The result is a sub that won't chuff even if you try with sine waves. Of course, real material is more less demanding as there is masking content and a wider distribution of frequencies, so a sine wave chuff test is more rigorous than most situations will require.

I read an AES paper on vents that actually shows that the best profile has two radii - one which has a very large radius where the cross sectional area increases from the centre to the ends, and another at the ends where there is a transition. This is virtually impossible for a diyer to realise in a circular vent, but could easily be done with slot ports made with 3mm MDF bent into shape. This is one feature of a slot port that I haven't seen tried, but if I was going to make a slot port it's what I'd do. The paper is called

Maximising performance from Loudspeaker ports
No 4855
Alex Salvatti and Doug Button
JBL Professional
Northridge, CA, USA
Allan Devantier
Infinity Systems
Northfidge, CA, USA

Very interesting paper, just wish I could figure out the formula that actually determines tuning!!!

Of course, you have to choose a point to draw the line between practical and ideal and decide how far you want to go.

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post #16 of 25 Old 04-04-10, 09:50 PM
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Re: New Tempest-X2 15" Slot Ported Design (Sketchup Attached) - Feedback Appreciated

Good post Paul.
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post #17 of 25 Old 07-28-10, 12:18 AM
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Re: New Tempest-X2 15" Slot Ported Design (Sketchup Attached) - Feedback Appreciated

How is the build going dboff01?

Just interested as i'm looking at using your design as a base for my own DIY build.
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post #18 of 25 Old 07-28-10, 11:38 AM Thread Starter
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Re: New Tempest-X2 15" Slot Ported Design (Sketchup Attached) - Feedback Appreciated

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How is the build going dboff01?
It's not.

With other home project and financial obligations, I'll be lucky if I can build before the end of the year. If you've seen the Money Pit with Tom Hanks, that's pretty close to my life.

In the meantime, I continue to model (WinISD) and draw (Sketchup) various enclosures/drivers/configurations to determine ultimately what I will build when I get the chance.

Steve
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post #19 of 25 Old 07-29-10, 01:05 AM
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Re: New Tempest-X2 15" Slot Ported Design (Sketchup Attached) - Feedback Appreciated

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dboff01 wrote: View Post
It's not.

With other home project and financial obligations, I'll be lucky if I can build before the end of the year. If you've seen the Money Pit with Tom Hanks, that's pretty close to my life.

In the meantime, I continue to model (WinISD) and draw (Sketchup) various enclosures/drivers/configurations to determine ultimately what I will build when I get the chance.

Steve
Bummer.

What design changes were you thinking of making?
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post #20 of 25 Old 07-29-10, 03:37 AM
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Re: New Tempest-X2 15" Slot Ported Design - Feedback Appreciated

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paulspencer wrote: View Post
I read an AES paper on vents that actually shows that the best profile has two radii - one which has a very large radius where the cross sectional area increases from the centre to the ends, and another at the ends where there is a transition. This is virtually impossible for a diyer to realise in a circular vent, but could easily be done with slot ports made with 3mm MDF bent into shape. This is one feature of a slot port that I haven't seen tried, but if I was going to make a slot port it's what I'd do. The paper is called

Maximising performance from Loudspeaker ports
No 4855
Alex Salvatti and Doug Button
JBL Professional
Northridge, CA, USA
Allan Devantier
Infinity Systems
Northfidge, CA, USA
Just for reference, this paper is available here.

Quote:
paulspencer wrote: View Post
Very interesting paper, just wish I could figure out the formula that actually determines tuning!!!
Do you mean this one?

Quote:
paulspencer wrote: View Post
Of course, you have to choose a point to draw the line between practical and ideal and decide how far you want to go.
That's very true.
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