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effect of internal standing wave?
effect of internal standing wave?
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Old 8th June 2010, 10:05 PM   #1
warpscan is offline warpscan  United States
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Default effect of internal standing wave?

I really need the experts knowledge here:

Can anybody describe the effects of internal standing wave in bass enclosure? I know it causes problems and causes peaks and valleys, so which is it? peak or valley in what situation?

Problem I have is suckout (-8dB) at 100~200Hz. The result is lack of punch in kick drum. my small bookshelf in same location (woofer cone) sounds like 1812 cannon in contrast.

I've built this full range speaker of following Internal dimension: 8"W X 11.5"D x 35"H It has 3" x 15" port (but I could plug the port to make it aperiodic sealed box, but same problem perists)
woofer is Seas Alu 8" tuned to 23Hz in ported configuration.

I don't think this is room standing wave problem nor Boundary effect as the woofer cones are situated 18" from
rear wall and 4 feet from side walls (speakers are 6' apart)
Im suspecting internal box standing wave. standing wave (half wave) for this box (height-wise) is 200hz.

My question is what is the expected effect of this? would standing wave of 200Hz reduce the 200hz output at the cone or amplify it? is this function of cone location? If so, my woofer being near the bottom of the cabinet cause suckout? at 200hz. This still does not explain why 100hz suckout.

by the way, my crossover point is 220hz to mid
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Old 9th June 2010, 02:37 AM   #2
warpscan is offline warpscan  United States
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I see that this is "full range" forum. I noticed that the term "full range" today is not what I thought it was. Realizing the word "Fostex" is all over this forum made me realize this is single driver (full range wannabe) forum.

Perhaps I should repost this on Subwoofer or multiway forums.
But if your dealing with TL's, of all people you should know answer to my questions.
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Old 9th June 2010, 02:47 AM   #3
planet10 is offline planet10  Canada
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effect of internal standing wave?
Your box has dimensions with a high enuff ratio that it could be acting as an ML-TL. Where are the driver and the port?

Of the terminus (ie port) output is out of phase with the front output you will have a suck-out. Any damping in the box?

dave
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Old 9th June 2010, 02:51 AM   #4
tinitus is offline tinitus  Europe
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effect of internal standing wave?
Quote:
Originally Posted by warpscan View Post

Perhaps I should repost this on Subwoofer or multiway forums.
Its in Multi-way speakers now
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Old 9th June 2010, 03:05 AM   #5
warpscan is offline warpscan  United States
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Quote:
Originally Posted by planet10 View Post
Your box has dimensions with a high enuff ratio that it could be acting as an ML-TL. Where are the driver and the port?

Of the terminus (ie port) output is out of phase with the front output you will have a suck-out. Any damping in the box?

dave
Center of the driver is 12" from the bottom. The port 3"x15" is mounter on the bottom firing down.

The woofer and port proximity is close enough that suckout seems not likely. The other end of the port is at about center of the box.
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Old 9th June 2010, 03:17 AM   #6
planet10 is offline planet10  Canada
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effect of internal standing wave?
The port is essentially in the middle of the line... almost as effective for exploiting the quarter wave resonance as if it was on the end.

Are the dimensions in post 1 internal or external?

dave
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Old 9th June 2010, 03:35 AM   #7
warpscan is offline warpscan  United States
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Quote:
Originally Posted by planet10 View Post
The port is essentially in the middle of the line... almost as effective for exploiting the quarter wave resonance as if it was on the end.

Are the dimensions in post 1 internal or external?

dave
Aforementioned dimensions were for the internals: Here is the quick sketch of it.
speaker00.JPG

As a quarter wave resonator, the length of the resonator equals to box height?
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Old 9th June 2010, 03:59 AM   #8
planet10 is offline planet10  Canada
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effect of internal standing wave?
An ML-TL is more complex because of the mass loading. you will need to model it in MJK to get a reasonable sim. Assuming 3/4" material you model your terminus as 14 1/4" (ie Zport) from the driver end. Zd = 12".

I'd just load it up with polyfluff to kill the undamped harmonics that are causing your suckout.

dave
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