New Approach for an Outline from a DIY Subwoofer - Precision Devices PD2150 inside - Page 3 - diyAudio
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Old 12th November 2011, 08:21 PM   #21
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Location: Los Angeles
Quote:
Originally Posted by tiefbassuebertr View Post
The image supplements from that one of post #1 (from the 1500 liter chamber in the attic) I have order in the meantime by the user. If I have receice, I will post it here. In this case I try to find comparable concepts by other user's by the use of follow term (keyword by google):

"IB sub in the attic"

As an example I find this:
Sub in the attic? - AVS Forum
and this both:
IB subwoofer picture gallery page 4
IB subwoofer picture gallery page 1
Are there basic articles about this kind of solutions ??
Well, if the stiffness of air behind the woofer is much less than the stiffness of the woofer suspension, then it will not affect the total stiffness. This means if the box is very big, it does not change the resonance of the woofer very much. So in a true infinite baffle, the parameters of the woofer do not change.* You will just get the response of the empty woofer. Something like an attic or the outdoors should be a true infinite baffle.*


*OK, the baffle can add some air mass load, and the walls/ceiling may not be perfectly rigid. But basically infinite baffle means if the speaker is Fs=50 at Q=0.3, then your response is Fs=50, Q=0.3. The bass response-without considering room effects-can become more like -6 dB/octave or even less.


Quote:
Originally Posted by tiefbassuebertr View Post
I ask this, because I miss the actually chamber (nearly free air condition and thus no wanted 24 db high pass filter character through certainly vented box alignment).
Basiclly I don't like 12 db high pass character in this frequency aera by the possibility for realizing large chambers. Only in case of low volume chamber the closed box 12 db character (and no vented box 24 db character) is to prefer from my view.
I think you are saying:
- You never liked 24 dB vented box sound
- 12 dB sealed sound is OK only if the box size is small
- You prefer the "open" sound of infinite baffle
Is my understanding correct?

If that is so, I would say you don't need an infinite baffle all the time. Many pro drivers have a stiff suspension, and even a medium size box does not affect their response so much at room temperature.

When the pro drivers become hot, their parameters shift, and then they work in big ported boxes.


I admire you working to type the English, by the way!
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Old 14th October 2013, 11:57 AM   #22
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Location: D-55629 Schwarzerden
Quote:
Originally Posted by head_unit View Post
Well, if the stiffness of air behind the woofer is much less than the stiffness of the woofer suspension, then it will not affect the total stiffness. This means if the box is very big, it does not change the resonance of the woofer very much. So in a true infinite baffle, the parameters of the woofer do not change.* You will just get the response of the empty woofer. Something like an attic or the outdoors should be a true infinite baffle.*


*OK, the baffle can add some air mass load, and the walls/ceiling may not be perfectly rigid. But basically infinite baffle means if the speaker is Fs=50 at Q=0.3, then your response is Fs=50, Q=0.3. The bass response-without considering room effects-can become more like -6 dB/octave or even less.




I think you are saying:
- You never liked 24 dB vented box sound
- 12 dB sealed sound is OK only if the box size is small
- You prefer the "open" sound of infinite baffle
Is my understanding correct?


If that is so, I would say you don't need an infinite baffle all the time. Many pro drivers have a stiff suspension, and even a medium size box does not affect their response so much at room temperature.

When the pro drivers become hot, their parameters shift, and then they work in big ported boxes.
I admire you working to type the English, by the way!
Unfortunately it isn't so easy, so that I can't you give an exactly explain in a short form. Please note additional, that english isn't my native language. By english is so bad, so that I get biggest problems in the event of a move to a country, where English is the main language.
If I say what I think in English, I will almost always misunderstood.


BTW - the main speakers to the mentioned project in post #1 are the follow:
Ein "Meilenstein" unter den Lautsprecher-Boxen: Dahlquist DQ10, Hifi-Klassiker - HIFI-FORUM

Last edited by tiefbassuebertr; 14th October 2013 at 12:00 PM.
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