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WHAT IF its somewhat Smaller? or Larger? Sealed Woofer Box and Frequency Response
WHAT IF its somewhat Smaller? or Larger? Sealed Woofer Box and Frequency Response
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Old 5th January 2018, 01:31 PM   #1
Eftegarie is offline Eftegarie  Netherlands
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Smile WHAT IF its somewhat Smaller? or Larger? Sealed Woofer Box and Frequency Response

Say a typical woofer driver for example a Dayton Audio 18" woofer, which happens to be highly reviewd, very affordable and thus I've bought two, in a sealed box to extend our base a little in a 3 way speaker system. link

Click the image to open in full size.
Credits thanks to diyAudio community member "Inductor"

The red line in the graph represents the frequency response for the sealed and fully closed enclosude of 154 Liters, right?

Now, what I'm curious about, is how would three other lines show this your graph:
- slightly larger enclosure of say 175 Liters (lets all make this an orange line)
- slightly smaller enclosure or say 125 Liters (lets all make this a pink line)
- much smaller enclosure of 100 Liters (lets all make this a blue line)
- Finally a line for the 100 liters enclosure stuffed with damping materials (brown)

I'm okay if you were to estimate / sketch roughly something in microsoft paint I just want to have a rough idea what happens with the frequency slope of a sealed woofer box, when the speaker enclosure is made larger/smaller

I hereby invite you all to respond with your own version of the above graphic drawn over it Thank you!
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Old 5th January 2018, 01:38 PM   #2
starkeyg is offline starkeyg
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Hello,

The other way to go is to use your "given" box size and user active equalization to boost the bass some. Search the web and you will find several have and are doing that to get the curves they want.
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Old 5th January 2018, 02:03 PM   #3
Eftegarie is offline Eftegarie  Netherlands
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As i'm a real fan of 3 way active crossovering systems, I knew that already, but thanks for pointing that out. Independant of equalisation (yess that can always be done to boost something indeed) my question remains:

How will the frequency response line differ when enlarging / reducing the box size?

Last edited by Eftegarie; 5th January 2018 at 02:05 PM.
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Old 5th January 2018, 04:23 PM   #4
scottjoplin is offline scottjoplin  Wales
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This will give you a rough idea what to expect mh-audio.nl - Home
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Old 5th January 2018, 04:58 PM   #5
Fidstang is offline Fidstang  United States
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What size room is this going in and what is your expectation for these? Are you looking for SPL or extension?

I think you will find the PA460-8 limited below 50Hz in sealed enclosures and a medium/large room. Then once DSP/EQ is applied, you may find the output to be lacking a little. Have you looked at the V.B.S.S design?

If your plan is to just reinforce the low-end of some quality speakers for music, then I would look into a PPSL configuration.
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Old 5th January 2018, 05:28 PM   #6
Nenola is offline Nenola  Finland
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I think the answers can be found in one of the simulation softwares, I personally use this one WinISD - Linearteam
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Old 6th January 2018, 12:26 AM   #7
DiscoJones is offline DiscoJones  United States
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This is very straightforward. The larger you make the enclosure, you will get more amplitude below the knee and less amplitude at the knee (shallow rolloff). The smaller you make the enclosure, you will get less amplitude below the knee and more amplitude at the knee (steeper rolloff). F3 will be lowest at some "optimal" enclosure size where Qtc = 0.707.

Dan
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Old 6th January 2018, 12:53 AM   #8
bentoronto is offline bentoronto  Canada
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WHAT IF its somewhat Smaller? or Larger? Sealed Woofer Box and Frequency Response
Quote:
Originally Posted by DiscoJones View Post
F3 will be lowest at some "optimal" enclosure size where Qtc = 0.707.
Wouldn't F3 be lowest the biggest the box?

B.
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Old 6th January 2018, 04:05 AM   #9
Ron E is offline Ron E  United States
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Quote:
Originally Posted by bentoronto View Post
Wouldn't F3 be lowest the biggest the box?
What do you think 'maximally flat' means?
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Old 6th January 2018, 04:16 AM   #10
globalplayer is offline globalplayer  Germany
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You can trade in efficiency for low end spl with a bigger enclosure.
Although the spl curve might not look as "nice"/flat.
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