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post #31 of 114 Old 10-14-08, 07:01 PM
 
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Re: Sealed test enclosure

A big thanks to Martin King for his help and analysis. He just got back to me .

The only time a quarter-wave cancellation will occur is in a system that is closed on one end and open on another. In a closed system such as the one Collo tested, there should only be half-wave resonances as found.

In explanation of Ricci's resonant dip/peak he said that it is likely a half-wave resonance on the 36.75" axis. To explain for the discrepancy between the found anomaly and actual half-wave node King said that it was likely a small air leak and/or cone movement causing this movement.

Glad we got this cleared up. Looks like your results were dead on Collo. Thanks!

Time to go brush up on my physics .
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post #32 of 114 Old 10-14-08, 08:00 PM
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Re: Sealed test enclosure

That's good news - I can go ahead and fix boxnotes and sonosub.exe with confidence.

Thanks to all involved. I just love the internet.. if you're not scared of a bit of criticism, you can get to the truth of just about anything fairly quickly.

Thxgoon, thanks for that link. I've been looking for some decent drawings and animations of standing waves for ages. The ones on that site are perfect!
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post #33 of 114 Old 10-15-08, 12:28 AM Thread Starter
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Re: Sealed test enclosure

Cool. I feel like I learned a bit here..

Andrew,

To clarify...Mr. King was saying that the reason the 170hz blip doesn't quite correspond with the internal box length (it should be slightly higher in frequency) could be due to an air leak or the cone movement? This could cause it to be slightly lower in freq? That's a new one for me...

Last edited by Ricci; 10-15-08 at 05:49 PM.
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post #34 of 114 Old 10-15-08, 12:37 AM
 
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Re: Sealed test enclosure

Quote:
Ricci wrote: View Post
Cool. I feel like I learned a bit here..

Jordan,
To clarify...Mr. King was saying that the reason the 170hz blip doesn't quite correspond with the internal box length (it should be slightly higher in frequency) could be due to an air leak or the cone movement? This could cause it to be slightly lower in freq? That's a new one for me...
Pretty sure you are asking me this.

That is what he speculated as the potential cause for the lowered resonance. Always learning, a great part of this hobby!
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post #35 of 114 Old 10-15-08, 05:54 PM Thread Starter
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Re: Sealed test enclosure

Yes. Apparently it was too late for me to be posting as I couldn't even keep my names straight!

On a sad note I'd like to have a moment of silence for my poor SRM sound card. It has gone to the big electronics guru in the sky. I fried the input on it. I made a stupid mistake trying to measure the FR of a CE4000. A new one is on the way.
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post #36 of 114 Old 06-18-09, 03:21 PM Thread Starter
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Re: Sealed test enclosure

I finally started on the first pair of sealed boxes awhile ago. It's slow going. I only have 14 clamps and very little time to devote. The basic dims are 24Lx24Wx36D. About 9 cu ft internal after displacements. I'm doing a few things with these that are going to be out of the norm. They'll have removable baffles like I've done on my last 2 boxes, removable back panels and probably some removable bracing. I was only going to do that on one of the 4 enclosures but it's almost easier to build all of them the exact same. I'm sort of modifying things as I go. I'll be able to configure the enclosures to use different drivers, ports, PR's, dual opposed drivers, etc for personal enlightenment. I don't want to have to build a new box, or chop one up when I want to try something out. Finish will be truck bed liner. Rugged and simple since these will be abused I'm sure. The basic idea is I make a bunch of baffles and just swap those out for whatever I want to do. I should be able to churn out a new baffle for a new driver or whatever in less than 2 hrs and cheaply.










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post #37 of 114 Old 06-23-09, 04:43 PM Thread Starter
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Re: Sealed test enclosure

More progress...Sloooooow...









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post #38 of 114 Old 06-23-09, 05:23 PM
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Re: Sealed test enclosure

They certainly look solid!

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post #39 of 114 Old 06-24-09, 01:00 PM Thread Starter
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Re: Sealed test enclosure

It's getting there. I have a lot more bracing left to add, which I'm sort of modifying as I go and can only clamp so much at one time. I'm working on the driver baffles currently. Still a lot left to do.
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post #40 of 114 Old 06-24-09, 07:11 PM
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Re: Sealed test enclosure

I think I have clamp envy ...

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