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Vent too long for enclosure

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BJtheDJ View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote BJtheDJ Quote  Post ReplyReply Direct Link To This Post Posted: 01 April 2021 at 6:50pm
Originally posted by ssbb1fire ssbb1fire wrote:

I found this but it's for 5" and my driver is 4" so I d'ont know if that's the best choice.


It will do the job for you and is most likely only slightly larger than that for a 4".

It will take up slightly more volume, but will do exactly the same job.


If your vaccinations were mandatory and
nobody in your class had measles, then
you know that you're not a Millenial kid.
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smitske96 View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote smitske96 Quote  Post ReplyReply Direct Link To This Post Posted: 01 April 2021 at 7:57pm
You could also fill up the remaining space with some material. However, I would test first before doing that permanently.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ssbb1fire Quote  Post ReplyReply Direct Link To This Post Posted: 01 April 2021 at 8:14pm
Thank you guys.
I have no problem with it being too big, I just thought that with a 5" driver it would line up perfectly, and a 4" driver wouldn't line up.
If I can just go with it, so I will.
I just need to figure out how to set it efficiently now.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ssbb1fire Quote  Post ReplyReply Direct Link To This Post Posted: 09 April 2021 at 10:05pm
Excuse me, but working on loudspeaker has raised some question and when I was talking about the frequency response and group delay you said :
Originally posted by Conanski Conanski wrote:

It's not rocket science they are just using bass boost to bring the lowend up.

I'm wondering, is there a way to lower the group delay of a loudspeaker or loudspeaker system ? There's information here and there, but I can't fin an acceptable group delay reference (like 20 hz => 30 ms is ok, 30 Hz => x ms, etc...) and I don't know if there's something I can do about group delay after the loudspeaker is build, by some signal processing...
(tell me if I'm not clear)
In short :
group delay too big
filter goes beep beep boop boop
less group delay
tl,dr : happy
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DMorison View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DMorison Quote  Post ReplyReply Direct Link To This Post Posted: 10 April 2021 at 2:07pm
I have seen a rule of thumb that GD(ms) > 400/f is likely to be audible, but I don't know if that is based on solid science or not, sorry.

Things that you can do to improve it: 
If a ported system, reduce the tuning frequency.
If using a high pass filter, reduce its frequency and order.
If using EQ to shape the low frequency corner of the system's response, make sure you don't try to make that corner too sharp. 

Note that several of these have other consequences you may not want.

HTH,
David.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ssbb1fire Quote  Post ReplyReply Direct Link To This Post Posted: 11 April 2021 at 12:01am
I agree with everything you said.
I'm looking for explanation on this : https://circuitcellar.com/research-design-hub/group-delay-basics-more-filter-fun/
It's a very complete document, where negative group delay though filters is mentioned. I don't know if that can help me or anyone can explain it in simpler words, because I d'ont understand everything, and that could be very interesting !
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DMorison View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DMorison Quote  Post ReplyReply Direct Link To This Post Posted: 11 April 2021 at 2:16pm
The method used in that example to create -ve GD would not work for a subwoofer as it relies on a notch filter, which would have to be positioned at the frequency of maximum GD. 
This of course would result in you notching out content that you want to keep, right around the low frequency corner of your system.

FWIW,
David.
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studio45 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 12 April 2021 at 2:34pm
Group delay is one of the things that defines the "feel" of a subwoofer or bass driver's output. In general, a sub with lower group delay will be reviewed using terms like "tighter", "dryer", "accurate" and so on, whereas one with higher group delay will elicit responses like "warm", "full", or "rounded". HOWEVER these are obviously very subjective terms and in fact the room the subwoofer is placed in, and its position within that room, can have a MUCH larger effect on its perceived sound. And, GD has nothing in particular to do with the actual output achievable. A very high or very low GD box could be just as loud.
The only mistake to avoid is to have a *large* narrow spike in group delay, such as might be caused by a port tuned for excessive gain in a small box, or application of too much bass boost EQ. I like to tune boxes to have the flattest GD curve I can get, while retaining as much low end extension as possible. Not necessarily the lowest possible GD figures, but the *least change* across the frequencies below 250Hz. 
Studio45 - Box Builder Commotion Soundsystem -Mobile PA
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